Towards utilization of water hyacinth for industrial

ZIMBABWE Journal of Technological Sciences

A JOURNAL OF

2 N D I N T E R N AT I O N A L R E S E A R C H C O N F E R E N C E S p e c i a l I s s u e Vo l u m e 1 ( 2 0 1 5 )

EDITORIAL BOARD Guest Editor-in Chief Prof. F.T. Mugabe Guest Editors Prof S.M Makuza Dr C.P. Mubaya Dr O. Tada Dr C. Murungweni Dr R. Ndebele-Murisa Dr J. Madzimure Dr S.S. Mlambo Dr F. Chatiza Dr C. Gomo Dr C. Kufazvineyi Eng. E. Manyumbu

Copyright@2015 Chinhoyi University of Technology ISBN: 2079-8997

Published by: Directorate of Research and Resource Mobilisation Chinhoyi University of Technology, P. Bag 7724 Chinhoyi, Zimbabwe Email: [email protected] Website: www.cut.ac.zw

EDITORIAL This special issue of the Zimbabwe Journal of Technological Sciences contains a selection of papers that were presented at the 2nd International Research Conference held on 20-21 July 2015 at Chinhoyi Hotel. The conference's theme was “Research, Technology and Innovation for Development in Africa” and is considered to be in line with the Zimbabwe Agenda for Sustainable Socio‐Economic Transformation (Zim-Asset), which has its vision “Towards an Empowered Society and a Growing Economy” The conference had four sub-themes viz a viz: Environment and wildlife; Technology, innovation and development; Entrepreneurship, hospitality and tourism; Biotechnology, livelihoods and sustainable development. The objectives of the conference were to: • • • •

Disseminate the research outputs of Africa with special focus on science, technology and innovation Provide intellectual space for cross fertilisation of research ideas in order to stimulate collaborative research amongst international scholars Promote development of scholarship amongst the next generation of African researchers Build partnerships and strengthen cooperation on technology and innovation

The bi-annual international conference is a platform for researchers and development specialists to share advances in research and education related to technology, innovation and development. It is also a place to discuss new opportunities and recent and innovative developments related to technology, innovation, appropriate technology transfer and modernisation of indigenous technologies. The bi-annual conference provides industrial companies, organisations/institutions with an opportunity to build and reinforce strategic relationships, networking with academic professionals so as to build research partnerships for research and development, have a rsthand information on what academics are doing in terms of technology and innovation research, in research institutions and also showcase expertise and capabilities. Professor Francis T. Mugabe Guest Editor-in Chief A Journal of Chinhoyi University of Technology

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CONTENTS EDITORIAL

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Towards utilization of water hyacinth for industrial products: A Review paper Sibanda, N., Murungweni, C., Zvidzai, C., Mashingaidze, A.B. and Ngadze, E

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Activated carbon from baobab fruit shells through domestic processes 17 Kodzwa, J. J., Danha, C., Mangori, L. and Chemura, A. Physical and chemical characterization of acid tar waste from crude benzol re ning. 26 Chihobo, C.H., Kumar, S., Kuipa, P.K. and Simbi, D.J. Characterization of acid tar waste from benzol puri cation Danha, C., Simbi, D.J. and Kuipa, P.K.

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Objective selection criteria and mating strategy of indigenous Nguni cattle under low-input in-situ conservation programs Tada, O., Muchenje V and Dzama, K

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Conservation Agriculture challenges in developing countries and possible suggestions - the case of Gokwe South District, Zimbabwe Mashango, G.

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"A Roadmap for Flue-curing Tobacco Barns: Towards Developing Improved Energy Efficient Barns for Small holder Farmers in Zimbabwe". Munanga, W., Kufazvinei, C. and Mugabe, F.T.

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Towards utilization of water hyacinth for industrial products: A Review paper 1

Sibanda, N., 1Murungweni, C., 1Zvidzai, C., 1Mashingaidze, A.B. and 2Ngadze, E. School of Agricultural Sciences and Technology, Chinhoyi University of Technology, P Bag 7724, Chinhoyi, Zimbabwe 2 Faculty of Agriculture, University of Zimbabwe, P Bag MP 167, Mount Pleasant, Harare, Zimbabwe 1

ABSTRACT Water hyacinth is a useful weed in the cleaning of water bodies loaded with industrial effluent but can become an environmental problem if its growth is not controlled. Water hyacinth is a potential raw material of several industrial applications. However chemical structure of the lignocellulosic hyacinth biomass has to be broken down rst in order to obtain fermentable sugars. Wood rotting fungi has been known to delignify plant biomass. Wood rotting fungi secrete extracellular enzymes including lignin peroxidase, manganese peroxidase and laccases that are important industrial enzymes with numerous biotechnological applications in bio-fuel, food, brewery and wine, animal feed, textile and laundry, pulp and paper and agricultural industries. This paper reviews the potential use of white rot fungi's (Pleurotus sajor caju, P. ostreatus and Lentinus edodes) extracellular enzymes to biodegrade water hyacinth biomass. Key words: water hyacinth, lignocelluloses, wood rotting fungi, extracellular enzymes

INTRODUCTION One of the primary roles of fungi in the ecosystem is decomposition, which is performed by the mycelium. The mycelium secretes extracellular enzymes and acids that break down lignin and cellulose, the two main building blocks of plant ber. White-rot fungi produce various isoforms of extracellular oxidases including laccase (Lac), Manganese peroxidase (MnP) and lignin peroxidase (LiP), which are involved in the degradation of lignin in their natural lignocellulosic substrates (Wesenberg et al., 2003). Lignocellulosic and energy rich crops have in the recent years gained popularity as an alternative feed stock with various applications in the industry. The ability of fungal enzymes to break down the complex structure of lignocelluloses, making available the carbohydrates and sugars in their simple and usable forms in numerous biotechnological applications such as bio-fuel, food, brewery and wine, animal feed, textile and laundry, pulp and paper and agricultural industries, has been studied extensively. White rot fungi species’ enzyme complex A Journal of Chinhoyi University of Technology

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has extensively been studied as well in relation to their application in biotechnology. Examples include Phanerochaete chrysosporium for biofuel production (Bak et al., 2010; Shi et al., 2008; Zhong et al., 2011) and Ceriporiopsis subvermispora for bio pulping and bio bleaching (Akhtar et al., 1998; Ferraz et al., 2008; Yaghoubi et al., 2008). Much of what has been done on the enzyme complex of white rot fungi of the genus Pleurotus species has been on the use of wheat or rice straw as the lignocellulose substrate, with the purpose of increasing yield in the production of Pleurotus mushroom for consumption (Chitamba et al.; Fanadzo et al., 2010; Gume et al., 2013), while little research has been done on the enzyme complex for various biological applications. The same goes for Lentinus edodes. Much of its activity on lignocellulosic substrate has been of interest only as far as mushroom production is concerned (Elisashvili et al., 2008; Morais et al., 2000; Royse, 1985). Water hyacinth biomass, with an average of 20% of cellulose, 10% lignin, and 33% hemicelluloses (Alam et al., 2014), is a potential raw material as a lignocellulosic feed stock.

Factors affecting ligninolytic enzyme kinetics Several factors in uence ligninolytic enzyme activity and these include fungal strain, concentration and source of nitrogen, moisture content, acidity (pH), temperature, aeration and nutrition (Isroi et al., 2011). In addition to the above factors, (Kirk and Farrell, 1987) observed that agitation, oxygen concentration and vitamins also in uence enzyme activity in their study on lignin degradation by P. chrysosporium.

Nitrogen source and concentration The effect of nitrogen varies among fungal strains and species. Studies reveal that nitrogen is critical for lignin degradation (Kirk et al., 1978). Nitrogen nutrient limitation is known to enhance lignin degradation. Depending on the species of white rot fungi, high nitrogen concentration is a drawback as it interferes with the selectivity of some species, hence the removal of some nitrogen improves lignin degradation (Dorado et al., 2001). The source of nitrogen produces different responses in white rot fungi. Inorganic nitrogen source decreased the activities of Laccase, MnP and peroxidases of Pleurotus ostreatus while organic nitrogen in the form of peptone and casein showed positive effects on these enzymes (Mikiashvili et al., 2006). In another study, Lac production from L. edodes was positively affected by increasing nitrogen concentrations. Isroi et al. (2011) attributed the different responses of nitrogen source and concentration to different nitrogen metabolism among species. Low nitrogen concentration and organic nitrogen are preferred for ligninolytic enzyme production and improvement of lignin degradation. 6


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Aeration Lignin degradation is an oxidative process and hence for maximal performance, air (oxygen) needs to be continually replenished through ventilation, to stimulate degradation. Aeration serves the purpose of oxygenation, removal of carbon dioxide, dissipation of heat, regulating humidity, distribution of volatile compounds produced during fermentation (Isroi et al., 2011). Non-lignin components are also degraded as air is replenished. Couto and Sanromán (2005) reported an increase in LiP productivity through an increase in aeration rate. Similar work was done by (Belinky et al., 2003) who recorded improved production of LiP and MnP through aeration with pure oxygen.

Fungal Strain There are many species and strains of white rot fungi, some of which produce an entire ligninolytic enzyme cocktail while others produce only partially the ligninolytic enzymes (Elisashvili et al., 2008). When grown on similar medium, Pleurotus sajor-caju and Lentinus edodes produce MnP and Lac but not LiP whereas P. chrysosporium produces all three; MnP, Lac and LiP (Buswell et al., 1995; Fu et al., 1997). In view of this, screening of a large number of isolates is important for selecting the ones with highest ligninolytic enzymes production and highest lignin degradation on speci c substrates. Scanning electron microscopy can be used to screen white rot fungi for preferential lignin degradation (Blanchette, 1984).

Moisture content Moisture content is critical for fungal growth, and should be de ned at the onset of substrate preparation as it signi cantly affects lignin degradation. Several studies revealed that lower solid to liquid ratio enhances MnP and LiP production (Fujian et al., 2001). The straw substrate is reported to be at optimum with water content of 75 ml/25 g substrate (Zadražil and Brunnert, 1981). The production of Lac was improved by increasing the moisture content from 40 to 60% in a study by Patel et al. (2009), Shi et al. (2008), Also observed that moisture content interaction with other factors such as time, signi cantly affected lignin degradation in biological treatment of cotton stalks using P. Chrysosporium. Cultures with 75% and 80% moisture content achieved higher lignin degradation by approximately 6% compared to those with 60% moisture content. The interaction of these factors with each other also has an effect on lignin degradation. It is important to provide optimized moisture content and control water activity of the fermenting substrate, since its availability in higher or lower levels adversely

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affects enzyme activity. The physico-chemical properties of the solids in the substrate or culture medium are also affected by moisture content, and therefore the overall process of enzyme production (Pandey et al., 1999).

Acidity Most white rot fungi perform optimally on slightly acidic conditions of between pH 4 and 5 (Reid, 1989). The acidity is reduced during incubation and fungal growth, (Agosin et al., 1985; Zadražil and Brunnert, 1981). Wheat straw fermentation using Vararia effuscata and Dichomitus squalens recorded a decrease in pH during growth, (Agosin et al., 1985). Laccase production from Pleuritus ostreatus was observed to be optimal at pH 5.0 and production decreased as pH was increased to more than 5.0. At increased pH the structure of enzyme Laccase is altered and this reduces its activity (Patel et al., 2009).

Temperature Different optimal temperatures for different fungal strains have been reported in the fermentation and production of ligninolytic enzymes. Most white rot fungi are active at moderate temperatures of between 15-35⁰C, (Reid, 1989), cited in (Isroi et al., 2011). The effect of temperature on the selectivity and rate of deligni cation differs among fungal species. Zadražil and Brunnert (1981), observed that lignin degradation was less at 30⁰C than at 22⁰C for white rot fungi species Ganoderma applanutum, Pleurtus ostreatus, and Pleurotus serotinus, whereas enhanced lignin degradation occurred at 30⁰C for white rot fungi Trametes hirsuta. Optimal temperatures for white rot fungi growth and lignin degradation are speci c to fungal strain, eco-physiological requirements of the fungal strain and the type of the substrate. During fermentation, the white rot fungi generate some metabolic heat, and culture temperatures may be raised to levels that inhibit fungal growth and enzyme activity, hence aeration is essential.

Substrate Particle size Particle size of substrate should be moderated or compromised to provide optimum enzyme activity. Small particle size provides a larger surface area for microbial attack, while larger particle sizes will provide better metabolic and ventilation efficiency because of the increased inter-particle space. When the substrate is too small or too ne, compaction occurs, which interferes with microbial respiration and renders ventilation ineffective resulting in poor performance of fungi (Pandey et al., 1999).

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Isolation and extraction of ligninocellulosic enzymes The cost of commercial enzymes in uences the viability of the overall process of biomass conversion into bio-fuels and other chemicals. To counter this challenge, increasing the efficiency of ligninolytic enzyme production by screening for novel fungal strains, and developing more efficient fermentation techniques is the focus of most current research (Pirota et al., 2014). Solid state fermentation (SSF) is a process of choice in lignocellulosic biomass bio-degradation for enzyme production and lignocellulose waste utilization. Among other advantages, SSF serves the purpose of anchoring cells produced during fermentation and the substrate provides the nutrient needed for fungal growth during fermentation, leaving a less costly need of supplementing the only de cient nutrients. Laboratory studies on fermentation and enzyme extraction are generally carried out in Erlenmeyer asks, beakers, petri dishes, roux bottles, glass and glass tubes as column fermentetors and enzyme kits are used for enzyme assays (Cunha and Aires-Barros, 2002) The need for industrial application has necessitated the up-scaling of these studies. Several bioreactors have been developed for various applications in SSF. Large scale fermentation has been carried out in tray, drum, and or deep-trough bioreactors. In the laboratory, SDS-Page and Chromatography are among the methods used successfully in puri cation of enzymes from different substrates. Industrially, several methods are also being used with success, and include, Superuid Critical Extraction, Aqueous Two Phase systems, where separation and concentration of target protein are achieved simultaneously.

WHITE ROT FUNGI APPLICATIONS IN INDUSTRY Enzymatic hydrolysis of Lignocelluloses Enzymatic hydrolysis is the breakdown of lignocellulose biomass by enzymes in order to recover monomeric sugars such as glucose and xylose that are further used in the production of ethanol, xylitol, organic acid and other chemicals, (Isroi et al., 2011). In enzymatic hydrolysis, pre-treatment of the lignocellulose substrate is essential in order to alter the chemical structure, the building blocks of the substrate such as lignin, hemicelluloses, cellulose and acetyl compounds and the physical structure, such as surface area, crystallinity, pore volume, biomass, particle size and the distribution of lignin in the biomass (Chang and Holtzapple, 2000). The most studied physical/mechanical and chemical pre-treatment methods like dilute-acid hydrolysis and ammonium bre explosion (AFEX), were found to effectively reduce biomass recalcitrance in a short time and therefore are attractive


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in industrial applications (Isroi et al., 2011). The problem with these methods, however, is that they are costly because they require high-energy, corrosion resistant, high-pressure reactors and extensive washing (Shi et al., 2008). Biological pre-treatment with white rot fungi is fast gaining favour as an alternative pre-treatment method because it is less costly. Other advantages include greater substrate and reaction speci city, lower energy requirements, less pollution generation, and higher yield of the desired product (Kirk and Chang, 1981). Slow rates of pre-treatments and potential carbohydrate loss due to cellulose and hemicelluloses degradation during pre-treatment are the major drawbacks on this method, and hence it has in the past been investigated less. But because biomass pre-treatment is a global issue that needs an environmentally friendly process, of late interest has been directed towards this method (Bak et al., 2010; Kirk and Chang, 1981; Ma et al., 2010; Shi et al., 2008; Taniguchi et al., 2010; Yu et al., 2009) Several white-rot fungal species have been used for pre-treatment on different lignocellulose biomass with the primary aim of delignifying the biomass making accessible to enzymes during hydrolysis the cellulose and hemicelluloses, and for increased sugar yield. In a study by (Hattaka, 1983; Shi et al., 2008) an evaluation of biological pre-treatment of wheat straw using nineteen white-rot fungi species followed by enzymatic hydrolysis, showed that after ve weeks of pre-treatment with Pycnoporus cinnabarinus, 54.6 % of the residue could be converted to reducing sugars by enzymatic hydrolysis. Another study by Taniguchi et al. (2005) also showed three to ve fold improvements in enzymatic hydrolysis yield using four white-rot fungi Phanerochaete chrysosporium, Trametes versicolor, Ceriporiopsis subvermispora and Pleurotus ostreatus. (Dias et al., 2010) also showed that wheat straw biologically pretreated with two white-rot fungi Irpex lacteus and Euc-1 could signi cantly increase hydrolysis yield by three and four times respectively compared with untreated straw.

Biofuels Bioethanol Biogas and Pyrolysis White rot fungi, with more than 1500 different species, are able to degrade lignin with little consumption of the cellulose component and therefore are mostly used in the biological pre-treatment of biomass to produce bio fuels including biogas, (Müller and Trösch, 1986; Sánchez, 2009) and bio char through the process of pyrolysis (Ma et al., 2010). Bio ethanol is produced from lignocellulosic biomass after hydrolysis of polysaccharides into monosaccharides. Increase in sugar yield by

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enzymatic hydrolysis after biological pre-treatment indicates a high ethanol yield (Isroi et al., 2011). According to Wan and Li (2010), corn stover biologically pretreated with C. subvermispora for 35 days increased ethanol yield by up to 57.8%. Ganguly et al. (2013) achieved ethanol yield of 3.496g/L with biological pretreatment with Pichia stiptis, 3.449g/L with Candida shehate and 3.144g/L from Saccharomyes cereviciae from water hyacinth. Saritha and Arora (2012), observed a lignin loss of 10.5 and 23.5% on soft wood and hard wood pre-treated with Streptomyces griseus. Pretreatment with white rot fungi Pleurotus ostreatus have been successfully used to increase biogas production. Müller and Trösch (1986) achieved 0.342L/g with wheat straw pre-treated with Pleurotus ostreatus from 0.293L/g untreated wheat straw. In another study by Zhong et al. (2011) corn straw pre-treated with Pleurotus orida recorded 16.58% less yield than chemically pretreated. It is important, however, to identify exact enzymes responsible for effecting the changes being reported.

Bio pulping and Bio bleaching White rot fungi can be used directly in the biological conversion process such as bio pulping and bio bleaching (Tian et al., 2012). Bio bleaching, now considered an effective alternative to chemical bleaches can reduce the use of chemicals, energy and pollutants, while increasing yield and strength of the pulp (Albert and Pandya, 2014). The process of bio bleaching uses white rot fungi in a solid state fermentation process (SSF) to degrade residual lignin in the pulp by using ligninolytic enzymes such as xylanases (Albert et al., 2011; Isroi et al., 2011). Trichoderma is one of the most effective white rot fungi that produce enzymes with high xylanolytic properties. Xylanase enzyme is especially used for bleaching (brightening) cellulosic bres. Cellulase-free xylanase from different fungal cocktail preparations have been successfully tested in the paper industry. Biological pre-treatment has been shown to decrease mechanical pulping energy, increase paper strength and properties (Albert and Pandya, 2014). In a study by Scott et al. (2002), bio pulping was demonstrated to be more bene cial over the traditional pulping methods throughout the production process to the nal product. In this study, energy savings of 33% from thermo mechanical method (traditional method) were reported. Tensile, tear, and burst indexes of the papers produced were improved, and this indicated much higher cellulose conservation during pulping. The brightness of the pulp was also improved and this indicated higher lignin removal and bleaching by the white rot fungi. In another study, use of Irpex lacteus on cornstalks showed enhanced deligni cation and xylan loss during mild alkaline pre-treatment and enzymatic digestibility. The lignin structure was


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modi ed over a treatment period of 15 days, with lignin loss from 75.67% to 80% and xylan loss from 40.6%- 51.37% (Yu et al., 2010).

Enzyme Production The ability of ligninolytic enzymes to oxidise both phenolic and non-phenolic lignin related compounds and highly recalcitrant environmental pollutants makes these enzymes useful for applications in several biotechnological processes. In order to feasibly apply fungal enzymes in various industrial biotechnological applications, high levels of enzymes must be available (Jurado et al). Several studies have focused on convenient and reliable production systems that are inexpensive with optimized media for large scale production . Laccase, cellulase, and xylanases are commercial enzymes that have a place in the food, pharmaceutical, pulp and paper industry. However, their relatively high cost on the market is a challenge and production from white rot fungi presents a favourable alternative for these industry sectors. Solid state fermentation method has numerous advantages over (SmF) submerged fermentation method. High product yield and simpli ed downstream processing, including enzyme extraction, characterizes the SSF method —

Animal feed The use of lignocellulosic (agro waste) waste directly as animal feed is widespread and most common form of biomass utilization (Isroi et al., 2011). Then use of white rot fungi to improve the quality of the feed by increasing the digestibility of agricultural residues was developed in 1902 by Falck (Cohen et al., 2002). Since then, this concept has been applied to improve the nutritional value of lignocellulosic wastes and forages (Agosin et al., 1985; Okano et al., 2009; Zadrazil and Puniya, 1995). Biological pre-treatment can increase bio-availability of nutrients and decrease anti-nutritional factors in forages (Mandebvu et al., 1999)

CONCLUSION Water hyacinth can offer suitable biomass for production of enzymes required for various industrial processes like biogas production and for improving feed quality in livestock industry. Application of white rot fungi capabilities can offer environmentally friendly processes for utilising lignocelluloses when compared to chemical and mechanical applications. The ability of wood rotting fungi to degrade lignocelluloses and the potential of lignocellulose biomass as a low cost source of mixed sugars for application in industry offers an opportunity to utilise water hyacinth biomass to produce hydro carbon products while reducing its negative impact on the environment. It is with this background that there is growing research interest on the effect of wood rotting fungi on lignocellulose biomass such as water hyacinth. 12


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Saritha, M., and A. Arora. 2012. Biological pretreatment of lignocellulosic substrates for enhanced deligni cation and enzymatic digestibility. Indian journal of microbiology 52: 122-130. Scott, G. M., M. Akhtar, R. E. a. Swaney, and C. J. Houtman. 2002. "Recent development in biopulping technology at Madison, WI," Progress in Biotechnology. Elsevier: 61-71. Shi, J., M. S. Chinn, and R. R. Sharma-Shivappa. 2008. Microbial pretreatment of cotton stalks by solid state cultivation of Phanerochaete chrysosporium. Bioresource Technology 99: 6556-6564. Taniguchi, M. et al. 2005. Evaluation with pretreatment with Pleurotus ostreatus for enzymatic hydrolysis of rice straw. Journal of Bioscience and Bioengineering 100: 637-643. Taniguchi, M. et al. 2010. Effect of steam explosion pretreatment on treatment with Pleurotus ostreatus for the enzymatic hydrolysis of rice straw. Journal of Bioscience and Bioengineering 110: 449-452. Tian, X. f., Z. Fang, and F. Guo. 2012. Impact and prospective of fungal pre‐treatment of lignocellulosic biomass for enzymatic hydrolysis. Biofuels, Bioproducts and Biore ning 6: 335-350. Wan, C., and Y. Li. 2010. Microbial pretreatment of corn stover with Ceriporiopsis subvermispora for enzymatic hydrolysis and ethanol production. Bioresource Technology 101: 6398-6403. Wesenberg, D., I. Kyriakides, and S. N. Agathos. 2003. White-rot fungi and their enzymes for the treatment of industrial dye effluents. Biotechnology Advances 22: 161-187. Yaghoubi, K., M. Pazouki, and S. A. Shojaosadati. 2008. Variable optimization for biopulping of agricultural residues by Ceriporiopsis subvermispora. Bioresource Technology 99: 4321-4328. Yu, H. et al. 2010. Fungal treatment of cornstalks enhances the deligni cation and xylan loss during mild alkaline pretreatment and enzymatic digestibility of glucan. Bioresource Technology 101: 6728-6734.


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Yu, J., J. Zhang, J. He, Z. Liu, and Z. Yu. 2009. Combinations of mild physical or chemical pretreatment with biological pretreatment for enzymatic hydrolysis of rice hull. Bioresource Technology 100: 903-908. Zadražil, F., and H. Brunnert. 1981. Investigation of physical parameters important for the solid state fermentation of straw by white rot fungi. European journal of applied microbiology and biotechnology 11: 183-188. Zadrazil, F., and A. K. Puniya. 1995. Studies on the effect of particle size on solid-state fermentation of sugarcane bagasse into animal feed using white-rot fungi. Bioresource Technology 54: 85-87. Zhong, W., Z. Zhang, W. Qiao, P. Fu, and M. Liu. 2011. Comparison of chemical and biological pretreatment of corn straw for biogas production by anaerobic digestion. Renewable Energy 36: 1875-1879.

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Activated carbon from baobab fruit shells through domestic processes Kodzwa, J. J., Danha, C., Mangori, L. and Chemura, A. Department of Environmental Science, Chinhoyi University of Technology, Zimbabwe, P. Bag 7724 Chinhoyi, Zimbabwe

ABSTRACT Surface and groundwater pollution is rampant due to poor waste management and runoff. Dry regions of the country also writhe from water scarcity which leaves communities to resort to unsafe water supplies for domestic use. It is estimated that about 90% rural households in Zimbabwe consume untreated water (Hoko, 2005) and that more than 75% of Zimbabwe's population lives under water stressed conditions in most rural areas (Manyanhaire et al., 2009). Commercially produced activated carbon is expensive. The aim of the research was to investigate the production of activated carbon from baobab fruit shells (a cheap raw material) using a method that can be employed at rural homesteads in removing organic pollutants. Two methods of producing activated carbon were also compared i.e. activating before carbonization and activating after carbonization. Activating with salt after carbonization proved to be the efficient (adsorption% 93.2). A contact time of 60 minutes was determined as the maximum time required for adsorption and a pollutant concentration equivalent to 0.3M oxalic acid gave the highest adsorption of 98.9%. The activated carbon from baobab fruit shells follows a Langmuir isotherm which explains the existence of a monolayer and the saturation of adsorption sites on the activated carbon. It was concluded that activated carbon from baobab fruit shells have the potential of removing organic pollutants from water. Key words: activated carbon, percentage adsorption, carbonization, adsorption, organic pollutants and fruit shells

INTRODUCTION Addressing the deterioration of water quality in developing countries, where most people lack access to potable quality water is a primary motivating aspect for many community development determinations and was a key element of the Millennium Development Goals. Hoko, (2005) reported that about 90% rural households consume untreated water. More than 75% of Zimbabwe's population lives under water stressed conditions in most rural areas, (Manyanhaire et al., 2009). A Journal of Chinhoyi University of Technology

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According to Hoko, (2005) water pollution is caused by poor management of waste water and solid waste, leaching and runoff of heavy metals and nutrients and unconventional consumption of fertilizers in agriculture. Mapira, (2011) concluded that as industrialization, including high-input agriculture, extends into less developed countries around the world, societies must contend with additional sources of contamination due to surface runoff and deep percolation containing pesticide, fecal matter, herbicide, fertilizer and agricultural residues. Increased surface water contamination due to runoff consequently increases the concentrations of organic pollutants in water and renders it unsafe for domestic use. Commercially produced activated carbon is expensive. In most developing countries, the activated carbon is imported at high cost and the activated carbon has been mostly used worldwide as an effective ltration or adsorption substance for removing biological and chemical pollutants from drinking water (Misihairabgwi et al. 2014. Lack of adequate water all year round in Zimbabwe and the heightened global warming effects, has resulted in the rural communities turning to polluted rivers as their source of domestic water. Mapira, (2011) states that the lack of water treatment facilities in the rural communities where there are vast natural and anthropogenic activities that contribute to high levels of organic pollutants in surface water systems along with groundwater exacerbates the risk of water borne diseases. Zimbabwe uses approximately 20 tonnes of activated carbon per month for urban water treatment and imports the activated carbon at high charges; the high cost of importing the activated carbon puts a signi cant burden on the water reticulation budget (Misihairabgwi et al. 2014). The strained nancial resources of the local authorities is forcing them to release raw wastewater into streams/ rivers and they leave uncollected solid waste be washed off into rivers posing health hazards to downstream users in the long run. Poor management of agricultural waste baobab shells included causes land pollution and reduces the aesthetic beauty of most market places in the country. Baobab fruits are mostly found in the in the semi-arid parts of Zimbabwe. Baobabs are used by locals as a source of income, they sell and distribute to most parts of the country where they are being used to make drinks and yoghurts. Using baobab fruit shells to produce activated carbon is a move to create economic value out of waste materials. Activated carbons are carbon derived compounds that have exceptional adsorption properties because of their high surface area, pores and large adsorption capacity. Activated carbon is a form of carbon that has been processed 20


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so as to be highly porous and have a large surface area. The volume of these pores varies subject upon the activating agents used during the production process (Kearns, 2012). Activated carbon is known to be effective in the removal (adsorption) of large and less soluble organic molecules from water, and smaller molecules if they t into the smaller pores (Mahommad-Khah et al., 2009). Activated carbon is used in water treatment plants and through physical adsorption it removes contaminants particularly micro organic pollutants from waste water, it improves taste, odour and colour associated with organics present in the water (Bolto et al. 2004). The carbon containing waste is processed into activated carbon through two processes i.e. carbonization and activation (Mohammed-Khan et al., 2009). Carbonization is also called charcoal production. The process of carbonization takes place when organic matter is raised to high temperatures in the absence of oxygen through a process known as pyrolysis (Wondwosen, 2009). Activation is the process of increasing the adsorptive capacity of charcoal (Kearns, 2012). The preparation of activated carbon with different pore sizes can be accomplished by using physical or chemical activation process (Abdullah, 2010). Chemical activation is the use of chemicals to activate the charcoal. Adsorption is fundamentally a surface phenomenon. Vanloon (2005) de nes adsorption as a process that takes place when a liquid solute collects on the surface of an adsorbent, forming a molecular or atomic lm. Physical adsorption or physisorption occurs with the formation of multilayer or monolayer of adsorbate on to the adsorbent and has a low enthalpy of adsorption (Garcia, 2011). The performance of an adsorbent for adsorption of adsorbate can be attained from plotting adsorption isotherms. The adsorption isotherm can also be de ned as the equation relating the amount of solute adsorbed onto the solid and the equilibrium concentration of the solute in solution at a speci ed temperature (Garcia, 2011). According to Wondwosen (2009) adsorption isotherms exhibit one of the three common distinguishing shapes depending on the adsorption mechanism and distribution of solute between the liquid and solid phases which are Freundlich, Langmuir and the Brunauer-Emmet-Teller (BET) isotherms. The BET is most common in gas adsorption and is a derivative of the Langmuir and Freundlich.

MATERIALS AND METHODS The baobab fruit shells were prepared by removing dirt and bers and were then sun dried. The dried baobab shells were cut into small pieces of between three to seven centimeters in length.


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Table 1: Naming the methods of producing activated carbon

Soak after carbonization Soak before carbonization

Salt (NaCl)

Lemon juice (citric acid)

Method A1

Method A2

Method B1

Method B2

Method A: The baobab shells were cleaned and sun dried. The dried shells were burnt in a closed perforated container until no smoke was being produced. The burnt charcoal was soaked in chemical solution some in salt (NaCl) and some in lemon juice for 4 hours. Method B: the dried shells were soaked in chemical agents before being burnt Determining the percentage adsorption was done using the equation, % adsorption = (Δ conc/initial conc) * 100 The activated carbon was weighed from 0.5 to 6.5g and the maximum percentage adsorption determined using 0.1M oxalic acid. The weight that produced the maximum percentage adsorption was used in different concentration of oxalic acid (0.1 to 1.3 M) and shaken. The samples were titrated at different time intervals (20, 40, 60, 80 and 100 minutes) for all the concentrations and the percentage adsorption was determined. Isotherms were then plotted.

RESULTS AND DISCUSSION Method A1 of soaking in salt after burning showed the highest percentage adsorption with a value of 93.2% and the method B2 of soaking in lemon before burning had the lowest percentage adsorption recorded of 40.2%.

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100

Method A adsorption efciency

90 80

% adsorption

70 60 50 40 30 20 10 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 amount of activated carbon (g) Method A1

100

Method A2

Method B adsorption efciency

90 80

% adsorption

70 60 50 40 30 20 10 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 amount of activated carbon (g) Method B1

Method B2

Figure 1: Trends in % adsorption for method A and method B A Journal of Chinhoyi University of Technology

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The higher percentage adsorption of Method A (soaking in chemical after burning) as compared to method B (soaking before burning) could have been as a result of changes in chemical composition of the activating chemical and the activated carbon during the carbonization process. The chemical lattice of activated carbon and that of the activating chemicals is affected by heat and causes the collapsing of the internal pores (Ademiluyi 2009). According to Horsfall et al., (2007) longer carbonization time also results in the evaporation of volatile compounds in the inner part of carbon. The possible reason for higher adsorption by activated carbon from method A than method B is because activating charcoal after carbonization increase the reaction of the activating chemical with the carbon surface were as before carbonization the chemical will evaporate as heat is increased before any carbonization thus there will be little contact between the carbon and the activating chemical. Differences observed between using salt and lemon juice amongst the sampled methods can be attributed to the molar concentrations of the activating agents. Lemon juice contains between 3% to 6% citric acid, Penniston et al. (2008) depending on the environmental conditions within which the fruit was grown. The salt was diluted in a ratio of 1:2 implying that there was 33 % salt in this activating solution. The higher percentage of salt as compared to that of citric acid in activation chemicals may have contributed to higher percentage adsorption by methods soaked in salt. The different interactions between the activating agent and the baobab shells could have contributed to the different levels of adsorption between the two chemicals used in the research. This is because one is neutral and the other is acidic. A maximum residence time of 60minutes is required to reach optimum percentage adsorption. The increase in contact time also increased the percentage adsorption up to a point where no further increase in adsorption was observed as shown by Fig 2. The available results revealed that the uptake of oxalic acid concentration is fast at the initial stages of the contact period, and subsequently it becomes slower near the equilibrium. The initial increase in concentration during the initial stages is because a large number of vacant surface sites are available for adsorption, and after a lapse of time, the remaining vacant surface sites are difficult to be occupied due to repulsive forces between the solute molecules on the solid and bulk phase.

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Effect of time on % adsorption

% adsorption

100 98 96 0.3 M 94 92 20 mins 40 mins 60 mins 80 mins 100 mins Time

Fig 2: line graph showing the effect of time on percentage adsorption

Effect of adsorbate concentration 120 % adsorption

100

96.6

98.4

90.6 82.1

80

63.5

60 40

60 minutes

20 0 0.1 M

0.3 M

0.5 M

0.7 M

1.3 M

concentration

Fig 3: Trend showing the effect of concentration on percentage adsorption Fig 3 shows that increase in the concentration resulted in an increase in adsorption up to a level where a further increase in concentration of oxalic acid yielded no changes. A further increase in concentration resulted in a decrease in the percentage adsorption as the activated carbon was saturated. The increase in concentration at rst is attributed to the large initial concentration gradient between the adsorbate in solution and the number of available vacant sites on the A Journal of Chinhoyi University of Technology

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adsorbent surface this causes an increase at rst until saturation of adsorption sites. The saturation can be attributed to the maintenance of xed number of binding sites in the dosage of activated carbon. This implies that an increase in pollutant concentration requires more activated carbon. The sorption sites on the activated carbon could only adsorb a certain concentration of oxalic acid. Organic pollutant removal by activated carbon is more efficient at low concentrations and reduces with an increase in pollutant concentrations. Freundlich Isotherm 0 -1.5

-1

-0.5

0 -0.1

Log qe-solute adsorbed (g/g)

-0.2 y = -1.289 x -1.5235 2 R = 0.8156

-0.3

-0.4

-0.5

-0.6

-0.7

Log Ce-equilibrium conc of solute (M)

9 8 y = - 66.269 x + 13.321 2

7

R = 0.9411

Ce/qe g/l

6 5 4 3 2 1 0 0

0.1

0.2

Ce -equilibrium concentration of solute (M)

Fig 4: Adsorption isotherms showing correlation 26


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Fig 4 shows the isotherms results obtained, both the Freundlich and Langmuir isotherms were found to correlate to adsorption data. It can be deduced that the Langmuir isotherm gave a better t to the experimental data than the Freundlich isotherm. This is attributed to the high R2 value of the Langmuir (0.9411) as compared to the Freundlich isotherm (0.8156). The results also imply that there is a homogenous distribution of active sites on the adsorbent from baobab fruit shells since the Langmuir equation assumes that the surface is homogenous. This con rms the formation of a mono layer on the adsorbent surface

CONCLUSIONS Activation by salt produced activated carbon with better percentage adsorption as compared to activation by lemon. Burning shells before soaking produced better results when compared to soaking before burning. However burning shells before activating by salt was the best method that produced activated carbon with the highest percentage adsorption of 93.2%. An increase in concentration of pollutants beyond 0.3 M reduces percentage adsorption of organic pollutants from water though an increase up to 0.3 M increases the percentage adsorption of organics. An increase in time of contact between adsorbate and adsorbent up to 60 minutes increases the reduction of organic pollutants by activated carbon produced from baobab fruit shells. Adsorption using activated carbon from baobab fruit shells produced a monolayer model with homogeneous distribution of active sites on the activated carbon which best ts the Langmuir isotherm.


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REFERENCES Abdullah, A., & Aberuagba, F. 2010. Comparatives study of the Adsorption of phosphate by activated charcoal from corn cobs, groundnuts shells and rice-husks. AU J Technol, pp59-63. Ademiluyi, F. T., Amadi, S. A., & Amakama, N. J. 2009. Adsorption and Treatment of Organic Contaminants using Activated Carbon from waste nigerian bamboo. J. Appl. Sci. Environ. Manage,13:39 - 47. Ansari, A. and Mohammad-Khan, R. 2009. Activated charcoal: Preparation, characterization and applications. International journal of chem tech research, 1 (4): 859-864 Bolto, B., Dixon, D., & Elridge, R. (2004). Ion exchange for removal of natural organic matter. React. Funct. Polym., 60:171-18 Garcia, I. 2011. Removal of natural organic matter to reduce the presence of trihalomethanes in drinking water. Stockholm: School of Chemical Science and Engineering, Royal Institute of Technology. Hoko, Z. 2005. An assessment of the water quality of drinking water in rural districts in Zimbabwe : A case of Gokwe South,Nkayi, Lupane and Mwenezi districts. Physics and Chemistry of the Earth, 30:859-866. Horsfall Jnr, M., & Vicente, J. L. 2007. Kinetic study of liquid-phase adsorptive removal of heavy metal ions by almond tree leaves waste. Bull. Chem. Soc. Ethiop, 23:349362. Kearns, J. 2012. International Bioachar initiative. Retrieved from http://www.wcponline.com: http://www.wcponline.com/pdf/October2012Kearns.pdf Mapira, J. 2011. River pollution in the city of Mutare (Zimbabwe) and its implications for sustainable development. Journal of Sustainable Development in Africa, 13(6):181-194. Manyanhaire, T., & Kamuzungu, T. 2009. Access to safe drinking water by rural communities in Zimbabwe: A case of Mundendavillage in Mutasa district. Journal of Sustainable Development inAfrica, 11:13-125.

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Misihairabgwi, J., Kasiyamhuru , A., Anderson , P., Cunningham, C., Peshkur, T., & Ncube, I. 2014. Adsorption of heavy metal by agroforestry waste derived activated carbon applied to aqeous solutions. African Journal of Biotechnology, 13(14):15791587. Penniston, K. L., Nakada, S. Y., Holmes, R. P., and Assimos, D. G. 2008. Quantitative Assessment of Citric Acid in Lemon Juice, Lime Juice, and Commercially-Available Fruit Juice Products. J Endourol HHS:567-570 Vanloon, G. 2005. Environmental Chemistry a Global Perspective (2nd ed.). New York, USA: Oxford University Press. Wondwosen, B. 2009. Preparation of charcoal using agricultural wastes. Ethip. J Educ. and Sc., 5(1):79-92


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Physical and chemical characterization of acid tar waste from crude benzol re ning *1Chihobo, C.H., 2Kumar, S., 1Kuipa, P.K. and 1Simbi, D.J. 1

Department of Fuels and Energy, Chinhoyi University of Technology, P Bag 7724 Chinhoyi, Zimbabwe

2

Department of Aerospace Engineering, Indian Institute of Technology, Bombay, Mumbai, 40076, India *Corresponding author: email address: [email protected]

ABSTRACT The physical and chemical composition of acid tar waste is important in assessing and developing technological processing options for their subsequent utilization. In the present investigation gas chromatography/mass spectrometry (GC/MS), fourier transform infrared (FTIR), inductively coupled plasma/atomic emission spectrometry (ICP/AES), scanning electron microscopy with energy dispersive Xray (SEM/EDX) were mainly used to characterize the acid tar waste from crude benzol re ning. The acid tar waste had a moisture content within the range 7-11%, pH values < 2.5 at a Liquid Solid (L/S) ratio of 20. Chemical analysis indicated the presence calcium, phosphorus and iron at 56.3, 15.7 and 11.3 ppm respectively with trace concentrations of lead, zinc, manganese and chromium. Organic analysis of the aromatic fraction of the acid tar waste by GC-MS revealed a wide range of compounds, including polycyclic aromatic hydrocarbons, furans, phenols, thiophenes and biphenyls. FTIR analysis was used to complement GC-MS. These results may be useful in the design and development of technological processes that can utilize acid tar waste. Key words: Acid tars; Analytical techniques; Hazardous waste; Hydrocarbons

INTRODUCTION Acid tars are hazardous waste generated during coal, petroleum and petrochemical processing (EPA 2002). They are generated as by-products of three distinct industrial processes, namely oil re-re ning, crude benzol re ning and white oil production. Although all the processes leading to the generation of acid tar waste involve the use of sulphuric acid, the physical and chemical composition of the resultant acid tar waste differ and depends on the initial raw materials and the process severity. In Zimbabwe, crude benzol re ning is carried out at ZimChem re neries near Kwekwe. The process utilizes the conventional sulphuric acid route to recover benzene, toluene and xylene fractions. 30


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The acid tar waste produced during the sulphonation processes is deposited in designated lagoons on the banks of Kwekwe river posing a threat to aquatic life. To date large quantities have accumulated in these designated lagoons. In order to eradicate the environmental problems associated with the acid tar land ll disposal option, an effective treatment method is needed for the existing lagoons and for quantities that are still being generated. The proper utilisation of acid tar waste in any application requires an in depth understanding of the physical and chemical properties of the acid tar waste. Data on physical and chemical characteristics of acid tar waste from benzol re ning are rather limited or unilaterally oriented, or are of an informative nature. This is due to the complex nature of the waste. No work has been reported on the characterization of acid tar waste from this particular site that is being investigated. Much of the existing research on the characterization and utilization of acid tar waste focused mainly on acid tars derived from petroleum processing Frolov et al.,(1980); Frolov et al.,(1981); Frolov et al., (1986); Aminov and Karpova (1988); Kolmakov et al., (2006) a,b; Kolmakov et al., (2007); Leonard et al., (2010). The physical parameters and composition of coal carbonization derived acid tars is important to assess the possibility to handle them, to determine extraction procedures and to develop technological processing options for their subsequent utilization. In this study GC/MS, FTIR, SEM/EDX and ICP/AES were used to characterize the acid tar waste originating from crude benzol re ning. It is hoped that the results will be useful for mapping appropriate remedial actions and treatment options for acid tar waste at ZimChem Re neries.

MATERIALS AND METHODS For this work, the acid tar waste was sampled from the land ll site and the fresh acid tar was obtained from the day tank before treatment prior to disposal. The land lled acid tar waste was coarse to ne grained whilst the fresh acid tar was found to be a dark brown thixotropic liquid with a characteristic acrid sulphurous odour. Both samples were packed in sealable bags and containers and transported to the Fuels and Energy Laboratory at Chinhoyi University of Technology, for analysis.

Physical characterisation The moisture content was determined as the weight loss after heating 1g of the sample at 105 C in a muffle furnace for 1hour. The ash content was determined as the residue remaining after combusting the sample to a constant weight in a muffle furnace at 750 C using open crucibles. The volatile matter content was determined using a non-isothermal thermogravimetric method following ASTM D 7582-12. About 30 mg of the sample were pyrolyzed in a Simultaneous Thermal Analyzer, Labsy Evo TG- DSC 1600 A Journal of Chinhoyi University of Technology

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(Setaram Instruments Inc, France) using a nitrogen ow rate of 100 ml/min. The temperature was programmed from ambient to 1000 oC at a heating rate of 20 K/min. The xed carbon content was calculated by difference. The ultimate analysis was based on ASTM D5373-14 and the test was performed using a Thermo scienti c FLASH 2000 Organic elemental analyzer.

Chemical characterization Aqueous extracts for pH determination were prepared by contacting the acid tar samples at liquid to solid (L/S) ratios of 5, 10, 20 and 40 for 48 hours with intermittent shaking at 180 rpm on a Gemmy Orbit Shaker, model VRN 480. Aliquots were obtained after vacuum ltration and the pH was measured using a Lasany LI 702 Digital pH meter equipped with a combination electrode.

Metal Analysis by ICP/AES A representative 2 g sample from each acid tar waste was digested by repeated addition of nitric acid and hydrogen peroxide according to EPA acid digestion procedure 3050B. In order to increase solubility of other metals 10 ml of concentrated hydrochloric acid was added to the digestate and re uxed further for 15 minutes. The ltrate was used as the nal analysis solution after vacuum ltration. The concentration of metal ions was determined by an ICP – AES (model ARCOS from M/S. Spectro, Germany). The Radio Frequency (RF) generator was operated at a maximum power of 1.6 kW at a frequency of 27.12 MHz. The spectrometer wavelength range was 130 nm to 770 nm with a resolution of approximately 9 picometer. The detector was a charged coupled device (CCD).

GC/MS Analysis The aromatic organic fraction was extracted by re uxing a 3 g sample of each acid tar waste in 300 ml of toluene for 24 hours. After re uxing, ltration was done under vacuum and Celite powder was used to absorb all the toluene insoluble impurities. The excess toluene was removed by rotary evaporation. The analysis was performed on an Agilent 7890 Gas chromatograph and a Joel Mass spectrometer model ACCU TOF GCV equipped with an Electron Ionisation (EI) source and a time of ight (TOF) mass analyzer with a mass range of 4 – 2000 amu and a mass resolution of 6000. The following GC-MS conditions were used: the oven temperature was held at 70 C for 1 minute and ramped by 8 C/min to 150 C; the temperature was held for 5 minutes at 150 C; gradually increased at a rate of 8 C/min to 260 C with a holding time of 7 minutes at 260 C. The temperature was nally ramped to 280 C at

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20 C/min with a 12 minutes nal holding time at 280 C, resulting in a 35 minutes run time, with cooling down to 70 C. Aliquots of 0.4 μL were injected into the Agilent split injector at 250 oC using a split ratio of 20:1. A 30 m long HP 5 neat column was used with a 0.25 mm diameter and a 0.25 μm lm thickness. A constant ow rate of 1 ml/minute of helium gas with a constant pressure of 93.17 kPa was used as the carrier gas. The mass spectrometer was operated in the full scan mode, scanning from 50 – 600 amu, with an acquisition speed of 25 spectra/second. A 3 minutes solvent delay time was used. The temperatures of the transfer line and the ion source were 260 C and 150 C, respectively. The NIST MS Search version 2.0 software was used for searching and identifying compounds from their mass spectra and for browsing the electron impact ionisation mass spectra library.

FTIR The fourier transform infrared spectroscopy (FTIR) analysis was carried out using a MAGMNA 550 Spectrometer (Nicolet Instruments, USA). A small quantity of acid tar waste weighing approximately 2 mg was mixed uniformly with KBr and pelletized into a transparent disk by applying a 3 T load. Samples were analyzed over a scanning range of 4000 cm- - 500 cm- at room temperature.

SEM/EDX micro analysis The morphological and chemical composition analysis was done using an Environmental Scanning Electron Microscopy (ESEM), Philips FEI Quanta 200, (Netherlands). The Quanta 200 ESEM was linked to an Energy Dispersive spectrophotometer (EDS) for semi quantitative micro chemical analysis. Before analysis samples were evenly dispersed onto a double sided carbon tape attached to a round metal stub, dried and sputter coated with a layer of platinum to reduce charging. The stubs were then xed to a sample holder, loaded into the sample chamber and evacuated. The analysis was done under a high vacuum mode using a 20kV accelerating voltage.

RESULTS AND DISCUSSION The pH values for acid tar waste at various liquid to solid (L/S) ratio are summarized in Table 1. Land lled acid tar generally showed relatively higher pH levels than fresh acid tar due to pre-treatment and neutralisation prior to disposal. As a result of concentrated sulphuric acid used in the crude benzol re ning process, pH of the fresh acid tar waste was highly acidic with values of < 1 at L/S ratios of 5, 10 and 20. The pH values at L/S 40 are suggestive of the strong acid dilution. The values in Table 1 are within the range of 0.3 - 3.9 and are in agreement with those reported by other


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investigators Milne et al., (1986); Nesbit et al., (1995); Banks et al., (1998). The pH of acid tars is variable and is dependent on the type of the process that generated the acid tar, the amount and strength of the acid used in the process and the degree of pre-treatment prior to disposal Nancarrow et al., (2001). Table1: pH values for acid tar waste. pH

Waste Type

Fresh acid tar Land lled acid tar

L/S =5

L/S =10

L/S=20

L/S = 40

0.53 ± 0.02 2.12 ± 0.02

0.63 ± 0.05 2.39 ± 0.02

0.85 ± 0.02 2.47 ± 0.03

1.23 ± 0.02 2.74 ± 0.02

The proximate and ultimate analysis data for the respective acid tars is displayed in Table 2 and 3. Table 2: Proximate Analysis result for acid tar waste. Proximate Analysis(%)

Waste Type Moisture Fresh acid tar Land lled acid tar

10.94 ± 0.34 7.27 ± 0. 14

Volatile matter 85.14 ± 0.46 34.12 ± 0.72

Ash 0.13 ± 0.23 7.48 ± 0.04

Fixed Carbon 3.79 51.13

Table 3: Ultimate Analysis results for acid tar waste. Waste type Fresh acid tar Land lled acid tar

Carbon 47.09 ± 1.68 62.18 ± 1.2

Ultimate analysis (%) Hydrogen Nitrogen Sulphur 5.97 ± 6.30 ± 12.3 ± 0.53 0.79 0.33 3.37 ± 0.57 ± 8.92 ± 0.16 0.02 0.17

Oxygen 28.34 25.54

The moisture content of the acid tar waste from crude benzol re ning determined by this study varied within the range 7- 11%. In separate studies Milne et al., (1986) and Leonard et al., (2010) reported the moisture content of acid tar waste from white oil production to be in the range of 3-10%. Nichol (2006) reported a moisture content of 6% for an acid tar waste originating from benzol re ning at the BurmahCastrol company, Ellesmere port, England. Frolov et al., (1980) also reported a moisture content in the range of 2.75- 8% for a fresh acid tar waste produced by a re nery operation treating lube oil with sulphuric acid. The fresh acid tar was 34


Chihobo et al.

characterized by a very high volatile matter and a low ash and xed carbon content. The ultimate analysis results of acid tar waste from crude benzol re ning in Table 3 are substantially higher than those found in many earlier studies. For example Kerr and Probert (1990) reported an ultimate analysis for an acid tar waste having; Carbon (25.12- 27.15%), Hydrogen (2.38-3.39 %), Oxygen (4.63-5.72%), Nitrogen (0.05-0.34%) and Sulphur (2.68-3.18%). Both the Carbon and Oxygen contents are much lower than those obtained from the sample under discussion. Figure 1 shows the GC-MS chromatographs for the aromatic fraction extracted from the two samples. (a)

x103

Intensity (7222710)

25.16

20.69 6000

25.84 29.86

16.12

4000

15.70

7.69

25.92

20.81

18.48

2000

33.97

0 0

(b)

x103

5

10

15

20 Time (min)

25

30

35

Intensity (2754228)

3.13

4.28 5.31 7.70

2000

18.48

1000

0 0

5

10

15

20

25

30

35

Time (min)

Figure 1 (a) Chromatograph for aromatic fraction of land lled acid tar. (b) Chromatograph for aromatic fraction of fresh acid tar. The land lled acid tar chromatograph Figure 1(a) showed more numerous and intense peaks from 7 to 36 minutes with the most abundant peaks occurring between 15 and 30 minutes. Comparison of the resulting mass spectra with the NIST 02 Electronic Ionisation Spectra Library con rmed the following main compounds in land lled acid tar waste; 1H -indene, 1-methylene, dibenzofuran, uorene, 1,1'-biphenyl,4-(1-methylethyl)-, 1,1'-biphenyl,2,2'5,5'tetramethyl,dibenzothiophene, phenanthrene, uoranthene, pyrene, 9H- uorene9-methylene, triphenylene and benz[e]acephenanthrylene. The most abundant peaks in fresh acid tar occurred between 3 and 9 minutes, likely compounds were


35

Chihobo et al.

identi ed as styrene, phenol, 1,3,5 trimethyl benzene, indene, naphthalene and 1,1'biphenyl,2,2'5,5'-tetramethyl. A compositional analysis of the two acid tar samples showed the presence of simple, lower molecular weight, aromatic hydrocarbon in fresh acid tar waste. On the other hand land lled acid tar waste was characterised mainly by complex higher molecular weight polycyclic aromatic hydrocarbons (PAH), furans, biphenyls and thiophenes. It can be suggested that some of the compounds detected in land lled acid tar waste are products of various chemical transformations that occur between the various components of acid tars under natural weathering conditions in the lagoons. Acid hydrolysis, oxidation, substitution and condensation reactions would be some of the postulated reaction mechanisms responsible for the various chemical transformations occurring in acid tar lagoons Frolov et al., (1985); Carey (2007) and Leonard, et al. (2010) reported the presence of PAHs such as naphthalene, ourene, ourathene, phenanthrene and pyrene in acid tar waste derived from processing of petroleum and petrochemicals using sulphuric acid. Similarly Jia et al., (2005) also reported the presence of xylene, toluene, pyrene, phenanthrene and naphthalene form a tar pond sludge containing waste streams from coal coking and steel making processes. Tables 2 and 3 describe the main products identi ed from the land ll and fresh acid tar waste samples . Table 4: Main products identi ed from the aromatic fraction of land lled acid tar waste by GC-MS Analysis and NIST Library Peak No

RT

IUPAC Name

Molecular Formula

1

7.69

1H -Indene, 1 - methylene

C 10 H8

2

13.79

Dibenzofuran

C 12 H8O

3

15.70

Fluorene

C 13 H10

4

16.12

1,1' - Biphenyl,4 -(1- methyl ethyl) -

C 15 H16

5

18.48

1,1' -Biphenyl,2,2'5,5' tetramethyl

C 16 H18

Chemical Structure

O

36


Chihobo et al. Peak No

RT

IUPAC Name

Molecular Formula

Chemical Structure S

6

20.05

Dibenzothiophene

C 12 H8S

7

20.69

Phenanthrene

C 14 H10

8

20.81

9H-Fluorene,9 - methylene

C 14 H10

9

24.14

Fluoranthene

10

25.16

Pyrene

C 16 H10

11

29.86

Triphenylene

C 18 H12

12

33.97

Benz[e]acep henanthrylene

C 20 H12

C 16 H10


37

Chihobo et al.

Table 5: Main products identi ed from the aromatic fraction of fresh acid tar waste by GC-MS Analysis and NIST Library.

38

Molecular Formula

Peak No

RT

IUPAC Name

1

3.13

Styrene

C 8H8

2

4.2 8

Phenol

C 6H6O

3

4.49

Benzene,1,3,5 trimethyl -

C 9H12

4

5.31

Indene

C 9H8

5

7.70

Naphthalene

C 10 H8

6

18.48

1,1' Biphenyl,2,2'5,5' tetramethyl

C 16 H18


Chemical Structure

OH

Chihobo et al.

422.79

566.88

746.49

84

86

88

1169.32

90

1031.70

698.14

618.83

473.33

878.64 812.59

1489.25 1444.40 1374.39

1602.16

1631.76

3053.80

2921.46 2854.82

3026.21

3419.04

92

94

96

98

Transmittance [%]

(a)

100

There were very few notable differences between the FTIR spectra of fresh and land lled acid tar (Figure 2). Although the intensities of the chemical groups varied between the two samples absorption bands were observed in almost the same regions. In the FTIR spectra of fresh acid tar waste an additional weak band was observed at 2150.87 cm- indicating the presence of a C C stretch. The absence of this group in land lled acid tar waste suggests that chemical transformation, possibly polymerisation had occurred. The broad peaks at 3436.11 cm- and 3419.04 cm - correspond to the heterocyclic and aromatic N-H stretches. The characteristic aliphatic C-H absorption bands were observed between 30002800 cm- in both the samples with fresh acid tar showing a much broader peak at 2850.20 cm- . This peak meant that fresh acid tar contained more long chain aliphatic compounds than land lled acid tar.

3500

3000

2500

2000

1500

1000

500

Wavenumber cm-1

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472.52 441.83

1393.44

845.22 753.38 680.55 583.04

1223.51

50 40

1049.14

1635.29

1485.76

1539.96

2850.20

2954.70

3436.11

3069.15

80 70 60

Transmittance [%]

90

1448.99

2150.87

100

(b)

3500

3000

2500 2000 Wavenumber cm-1

C:\PROGRAM FILES\OPUS_65\2013-2014\INTERNAL\ANOOP\REFINARYWASTE-LIQUID.0

1500

REFINARYWASTE-LIQUID

1000

500

SAIF IIT Bombay 27/08/2014

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Figure 2: (a) FTIR Spectrum of land lled acid tar. (b) FTIR Spectrum of fresh acid tar waste A Journal of Chinhoyi University of Technology

39

Chihobo et al.

The weak to medium spectral bands observed around 1640 cm- - 1550 cm - can be assigned to the N-H bending vibrations suggesting the presence of nitro compounds. However, aromatic ring vibrations are also centred around 1600 cmand 1500 cm- making interpretation of the spectrum in this particular region very difficult. Both samples showed a series of weak bands in the region between 1620 cm- and 1400 cm- called ring modes. These bands may be due to the stretching vibration of the carbon - carbon bonds in benzene rings. Fresh acid tar waste showed an intense ring mode at 1485.76 cm- . However, the ring modes were weaker and overlapping in the land lled acid tar waste spectra. The differences in the number and intensity of the ring modes between the two samples showed the variation in the substitution pattern and nature of substituents on the aromatic rings. The bands observed between 1225 cm- and 950 cm- can be assigned to aromatic C-H in plane bending vibrations. However, these bands have a wide range in which they can appear and are not useful group wave numbers (Smith,1998). The existence of the narrow and sharp out of plane C-H bending vibrations between 700 cm- - 1000 cm- is strong evidence of the presence of aromatics and/or PAHs in both samples. The out of plane C-H vibrations were much more intense in fresh acid tar waste with peaks at 845.22 cm- , 753.33 cm- and 680.55 cm- , possibly indicating a relatively higher concentration and presence of aromatics in fresh acid tar waste than in land lled acid tar waste. The peak at 3436.11 cm- combined with the elementary analysis results in Table 3 further suggest that fresh acid tar may contain macromolecular aromatic nitrogen compounds. The FTIR results con rmed some of the functional groups in the compounds identi ed by GC- MS. Table 6 shows the metal ion concentration in the acid tar determined by ICP/AES. The dominant metals in fresh acid tar were iron, calcium and phosphorous with concentration of 11.263, 10.779 and 15.664 ppm respectively. The calcium concentration was exceptionally higher in land lled acid tar waste with a concentration of 56.257 ppm. This high concentration of calcium may be attributed to the use of CaO in the neutralisation of acid tar waste prior to disposal. By way of comparison Leonard et al., (2010) measured an iron and lead concentration of 1200 and 2420 ppm, respectively from an acid tar derived from petroleum and petrochemicals processing. The concentration of metals determined by this study are much lower than those reported by Leonard. The concentration of metals in acid tar waste varies over a wide range depending on the process leading to their generation. Generally, acid tar waste derived from oil- re re ning are characterised by higher metal concentrations due to the wear and tear from metallic parts during lubrication (Dominguez-Rosado and Pichtel, 2003).

40


Chihobo et al.

Table 4: Metal concentration in acid tar waste determined by ICP/AES Fresh AT Land lled AT

Pb

Zn

Fe

Al

Mn

Ca

Cr

Mg

P

Si

S

0.202

3.179

11.263

2.731

0.141

10.779

0.313

1.908

15.664

2.63

3.044

0.052

0.744

4.724

5.816

0.356

56.257

0.126

2.429

5.44

1.284

0.084

The surface morphologies of the land lled and fresh acid tar waste are presented in Figure 3. Fresh acid tar had a smooth surface, while the land lled acid tar revealed a characteristically coarse grained surface morphology. Elemental chemical analysis by EDX of both samples showed strong sulphur peaks as expected. Land lled acid tar waste showed a much stronger carbon peak than fresh acid tar waste indicating the presence of carbon rich molecules. These observations corroborate with results obtained in the ultimate analysis of both samples in Table 3. Fresh acid tar waste showed a signi cant high metal concentration than land lled acid tar waste. This can be explained by the fact that during storage in lagoons acid tars leach signi cant amounts of metals when exposed to water. (a) C

S

P

o N Mg Na AI

Ca

Ti

K

1.00

2.00

3.00

4.00

Mn Fe 5.00

6.00

Pb 7.00

8.00

9.00

10.00 11.00

(b) S

0 Ti Mn C B

Mg Na AI Si

P

Ca K Cd 1.00

2.00

3.00

Ti V Cr 4.00

5.00

Fe 6.00

7.00

8.00

9.00

10.00 11.00

12.00 13.00

Figure 3 (a) SEM/EDX micrograph and spectra of land lled acid tar waste. (b) SEM/EDX micrograph and spectra of fresh acid tar waste. A Journal of Chinhoyi University of Technology

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Chihobo et al.

CONCLUSION The physical and chemical properties of acid tar waste from crude benzol re ning were studied using different analytical techniques. Signi cant differences in physical and chemical properties exist between the two acid tar samples. The acid tar waste in general had a moisture content within the range of 7 -11% and pH values < 2.5 at a L/S ratio of 20. Fresh acid tar waste exhibited a high volatile matter and a low xed carbon content compared to land lled acid tar. Elemental chemical analysis by EDX showed strong sulphur peaks as expected form both samples. The ultimate analysis indicated a higher nitrogen content in fresh acid tar. No heavy metals were detected by ICP/AES. Organic analysis of the aromatic fraction of the acid tar waste by GC-MS revealed a wide range of compounds, including polycyclic aromatic hydrocarbons, furans, phenols, thiophenes, styrene and biphenyls. FTIR analysis results con rmed the presence of aromatics and/or PAHs in both samples and was used as a complementary analytical technique to GC-MS. These results can be used in the design and development of technological processes that can utilize acid tar waste.

ACKNOWLEDGEMENTS The authors are grateful to all the staff members at the Sophisticated Analytical Instrumentation Facility (SAIF), Indian Institute of Technology, Bombay, for providing some of the characterization facilities and ZimChem Re neries for the materials. We appreciate and acknowledge the nancial support provided by Chinhoyi University of Technology through the Staff Development Fund.

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REFERENCES Aminov, A. and Karpova, I. 1988. "Production of binders from acid pond tar." Chemistry and Technology of Fuels and Oils, 24(8):335-337. Carey, F. 2007. "Organic Chemistry, 7th." Ed., MacGraw Hill,pgs 235-238 Dominguez-Rosado, E. and Pichtel, J. (2003). Chemical characterization of fresh, used and weathered motor oil via GC/MS, NMR and FTIR techniques. Proceedings of the Indiana Academy of Science. EPA. 2002. European Waste Catalogue and Hazardous Waste List EPA. Ireland Frolov, A., Aminov, A. and Timrot, S. (1981). "Composition and properties of acid tar and asphalt produced from acid tar." Chemistry and Technology of Fuels and Oils, 17(5):284-288. Frolov, A., Aminov, A., Veselov, A., Lysenko, B. and Timrot, S. 1980. "Production of paving asphalt from acid tar." Chemistry and Technology of Fuels and Oils, 16(9):564-566. Frolov, A., Denisova, T. and Aminov, A. 1986. "Utilization of acid tars." Chemistry and Technology of Fuels and Oils, 22(5):203-206. Frolov, A., Titova, T., Karpova, I. and Denisova, T. 1985. "Composition of acid tars from sulfuric acid treatment of petroleum oils." Chemistry and Technology of Fuels and Oils, 21(6):326-329. Jia, L., Anthony, E. and Turnbell, R. 2005. "Treatment of tar pond sludge in a circulating uidized bed combustor." Remediation Journal 15(2): 63-73. Kerr, K. and Probert, S. (1990). "Fluidised-bed incineration of acid tar wastes." Applied Energy, 35(3):189-243. Kolmakov, G., Grishin D., Zorin, A. and Zanozina, V. 2007. "Environmental aspect of storage of acid tars and their utilization in commercial petroleum products (Review)." Petroleum Chemistry, 47(6):379-388. Kolmakov, G., Zanozina, V., Karataev, E., Grishin, D. and Zorin, A. 2006. "Thermal cracking of acid tars to asphalts as a process for utilization of re nery wastes." Petroleum Chemistry, 46(6):384-388. Kolmakov, G., Zanozina, V., Khmeleva, M., Okhlopkov, A., Grishin, D. and Zorin, A. 2006. "Group analysis of acid tars." Petroleum Chemistry 46(1): 16-21.


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Leonard, S. A., Stegemann, J. A. and Roy, A. (2010). "Characterization of acid tars." Journal of hazardous materials, 175(1):382-392. Milne, D., Clark, A. and Perry, R. 1986. "Acid tars: their production, treatment and disposal in the UK." Waste management & research, 4(1):407-418. Nancarrow, D., Slade, N. and Steeds, J. 2001. Land contamination: technical guidance on special sites: acid tar lagoons, Environment Agency. Nesbit, N., Mallett, S. and Pollard, S. 1995. Resolving the Heterogeneity of Tarry Wastes During Investigation of Acid Tar Pits. Contaminated Soil'95, Springer: 243244. Nesbit, T., Banks, D., Firth, T. and Power, S. 1998. "Contaminant migration from disposal of acid tar wastes in fractured Coal Measures strata, southern Derbyshire." Geological Society, London, Special Publications,128(1):283-311 Nichol, D. 2006. "Geo-engineering problems at Llwyneinion hazardous waste site. Smith, B. C. (1998). Infrared spectral interpretation: a systematic approach, CRC press.pgs 412-415.

44


Characterization of acid tar waste from benzol puri cation Danha, C., Simbi, D.J. and Kuipa, P.K. Chinhoyi University of Science and Technology Department of Environmental Science and Technology,

1

ABSTRACT The use of concentrated sulphuric acid to purify benzene, toluene and xylene produces acidic waste known as acid tar. The characterization of the acid tar to determine the composition and physical properties to device a way to use the waste was done. There were three acid tars two from benzene (B acid tar), toluene and xylene (TX acid tar) puri cation streams and one which was from the storage tank (HT acid tar). The viscosity and density varied greatly amoung the three acid tars with B acid tar having the lowest viscosity (28.3mPa.s) and HT acid tar having the highest viscosity (63.592Pa.s). For density HT had the lowest (1.43g/ml) and TX had the highest (1.549g/ml). The sulphuric acid % concentration was 15.4% for HT, 23.7% for TX and 24.2% for B acid tar. The solubility test also showed a difference in the three acid tars, B acid tar was more soluble in water than in methanol while the other two were more soluble in methanol than in water. GC-MS and FT-IR results showed that TX and HT acid tars had weak organic acid such carboxylic acid, alcohols and aldehydes. The B acid tar had few organics as compared to TX and HT. The results show that the sulphuric acid is being lost in the holding tank and the physical and chemical properties of B and TX acid tar are different thus the need to treat differently if they are to be treated separately. The HT acid tar has properties that make it easier to work with; an example is the high viscosity and the high organic content. Key words: Acid tar, benzol processing, sulphuric acid, organic acids, characterization and viscosity

INTRODUCTION Acid tar is waste produced from puri cation of benzene, toluene and xylene using sulphuric acid. The benzene, toluene and xylene are from benzol processing. Benzol is a by product of coal carbonization. Acid tars are mainly from three processes namely re-re ning of spent lubricating oils, re ning of petroleum fractions and in crude benzol re ning. The re ning of crude benzol involves washing with concentrated sulphuric acid which sulphonates the more A Journal of Chinhoyi University of Technology

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Danha et al.

undesirable compounds and allows easier separation and recovery of the Benzene, Toluene and Xylene fractions. The Acidic tarry waste material generated is regarded industrially as a product of low commercial value and is disposed off in lagoons; however, acid tars from crude benzol can be feed stocks for the synthesis of other valuable products. In Zimbabwe acid tar waste is generated at Zimchem Re neries (PVT) LTD situated at ZISCO Steel in Redcliff. The waste is contained in lagoons lined with sealing tar which expose the waste to air and rain. The acid tar is sometimes mixed with lime at the lagoons. There are two streams that produce acid tar at Zimchem. The benzene puri cation, which uses oleum (100% sulphuric acid) and the toluene and xylene puri cation which uses 98% sulphuric acid are the two streams. The acid from the two streams is then directed to a holding tank before taking the acid tar to the lagoons. Under normal production the company disposes about 40 tons of acid tar a month. Kwekwe River is situated at the bottom of the mountain where the lagoons are. The river is a source of water for Redcliff town. Disposing acid tar in open lagoons expose the environment to different impacts since the effects are dependent on the temperature and moisture content (Catney, et al, 2005). Leaching of acid tar affects ground water for example acidi cation of groundwater was observed with high levels of sulphates in areas close to the Pesniski Dvor dumping site (Zilic-Fiser et al., 2010). Evolution of gas from the waste also affects the atmosphere which might lead to acid rain which will in turn affect surface water. During storage in holding ponds, the chemical composition of the acid tar changed as a result of leaching of the acid from the tar by rainfall, evolution of sulphur dioxide and condensation of the substances present in the acid tar leading to the inconsistent chemical composition of the acid tar that changes with time due to the reaction of the organic components with atmospheric oxygen and sulphuric acid (Frolov et al., 1981 and Burtanaya et al., 2007). The use of quick lime to neutralise acid tars in lagoons has been found to be environmentally unacceptable since it produces emissions which will lead to environmental problems such as acid rain and global warming (Catney et al., 2005). The proper utilisation of acid tars in any application requires an in depth understanding of the chemical composition of acid tar. The composition of acid tar has been determined using gas chromatography-mass spectrometry (GC-MS) (Leonard et al., 2010). Mass spectrometry detection simpli es the analysis by eliminating the need for standards to identify the organic groups. In another research organic compound content of spent sulphuric acid from benzol re ning process was analysed using gas chromatography with ame ionisation detector (Chojhacki et al., 2005). The use of Fourier transform infrared (FTIR) spectrometry with gas chromatography-mass spectrometry for characterisation of organics and

46


Danha et al.

coal by-products was common (Kempe et al., 2005, Ku et al., 2005, Leonard, et al., 2010 and Semenova, et al., 2007). FTIR is used to further con rm the presence of organic groups detected by GC-MS (Burtnaya, et al., 2007 and Semenova et al., 2007). GC was used to separate the organic components using oven temperatures adapted to each mixture (alkanes, branched alkanes, cycloalkanes and aromatics the temperature range was 28 to 2700C) (Kempe et al., 2005). There are some investigations that just relied on FTIR for characterisation (Hu, et al., 2012, Rincon, et al., 2005 and Semenova et al., 2012). Generally the results obtained indicate that the percentages of organic oils in the acid tars are higher than corresponding sulphuric acid present in the samples (Frolov et al., 1981, Leonard et al., 2010, Chojnacki et al., 2005, Kolmakov et al., 2006, Frolov et al., 1986, Nichol, 2000 and Aminov et al., 1989). Fresh acid tar has a high percentage of sulphuric acid as compared to the pond acid tar. Percentage of sulphuric acid decreased with time in storage tanks where a solid lm had formed on the surface of the acid tar (Frolov et al., 1981). The differences in the percentages of the sulphuric acids may be explained by the fact that the acid is either being consumed by chemical reactions or evaporating into the air, thus there is need to nd out what happens to the acid tar the minute it is produced to about a year in a monitored environment. The percentage of sulphuric acid varies from sample to sample. In the characterisation of acid tars, two acid groups were observed as evidenced by the two plateaus obtained in the acid base titration, suggesting the presence of both weak acids and strong acids in the acid tar (Leonard et al., 2010). In their further characterization they obtained methyl phenyl benzoic acid, naphthalenyl propenoic acid, phtalic acid, naphthalene acetic acid and phenathrene carboxylic acid. Freshly produced acid tars consisted of mainly sulphuric acid, sulphonic acid and carboxylic acid (Frolov et al., 1986). The pH of acid tar is variable and depends on the process by which the acid tar is generated, the amount and strength of the sulphuric acid used in the process and pre-treatment prior to disposal (Nancarrow et al., 2001). Chojnacki et al., (2005) characterized petrochemical sulphuric acid from benzol re ning and observed that sulphuric acid was 63.8 mass%, organic was 3.547mass% and the inorganic impurities constituted the rest. Sulphuric acid content ranged from 29.5 to 41.1% for the acid tar from various oil treatments (Purings et al., 1990). In studying the Hoole Bank Lagoon in Europe, it was observed that particles settled at the bottom of the lagoon, and the


47

Danha et al.

density of acid tars ranged from 1.2 to 1.4 g/ml and the viscosity varied with temperature (Nichol, 2000). In a similar research at the D.I. Mendelev Yaroslav in Russia, high ash content of approximately 6.5% and high viscosity for the bottom layer of acid tars (Tumanavskii et al., 2004). The research aims at coming up with physical and chemical characteristics of the acid tars produced at Zimchem Re neries so as to deduce ways to utilize the waste.

MATERIALS AND METHODS Materials Acid tar samples Three different acid tar samples from crude benzol processing were used. The sample denoted as TX acid tar was from the toluene and xylene puri cation with 98% sulphuric acid. This sample was brown and viscous. The second one was from benzene puri cation with oleum. This sample was black and less viscous than the rst one and was assigned the name B acid tar. The third one was from the holding tank were the rst two streams are collected into. This sample was dark brown and more viscous than the rst two and was assigned the name HT acid tar. The three acid tars were very acidic such that the pH had to be measured after dilution with distilled water (1g/100ml).

Method Viscosity and density Viscosity was measured using NDJ-85 viscometer at 25⁰C. Density was measured using speci c gravity bottle at 25⁰C. Titration of acid tar 1g of acid tar was placed into 100ml volumetric ask and was diluted with distilled water to 100mls. 20 mls was withdrawn and titrated with 0.1M sodium hydroxide, after a Lasany L1-702 pH meter was immersed. pH was measured after every 2mls of base and a record was made. Plot of volume versus pH were made from which the volume at pH 7 was obtained. The concentration of the acid was then calculated. Solubility of acid tar in various solvents 1g of acid tar was diluted with 100mls of two solvents (water and methanol). The mixture was ltered after agitation for 30 minutes. The percentage soluble was

48


Danha et al.

obtained from the initial and nal weight. % of soluble = [(Initial grams – grams of sample on lter paper)/initial weight]x 100 Gas Chromatography – Mass Spectroscopy (GC-MS) Liquid- liquid extraction Acid tar was dissolved in water then ltered and the water soluble organics were extracted using pentane and hexane. The solid part was dissolved in methanol, dichloromethane and in toluene. The samples were also re uxed with toluene. Then the samples were analysed using GCMS-QP2010 Ultra Shimadzu. The solvents were used for baseline determination. The GC was operated in split mode ratio 2:1. Helium gas owed at 47.1cm/sec and this was the carrier gas. The capillary column was 30m by 0.25mm and was programmed at 60⁰C for 5 minutes and increased to 300⁰C at 10⁰C/minute, was held at 300⁰C for 2 minutes, which resulted in 31 minutes total running time. The MS scanning was between 35 and 500m/z with an inlet line temperature of 250⁰C, ion source temperature of 200⁰C and electron ionization mode of 70eV. All this was done to identify the organic compounds found in the acid tar. Fourier transform infrared spectroscopy (FTIR) Samples were ltered and analysed using the Agilent 600 FTIR. The samples were analysed in solid form. The results were interpreted using (Coates, 2000).

RESULTS Viscosity and density Table 1 shows the viscosity of the acid tars and their density and the more viscous acid tar has a lowest density. HT acid tar has the highest viscosity and the lowest density. This can be because the acid tar is not fresh as the other two are and is a mixture of the two which might have resulted in chemical reaction. This means that the reaction that occur in the tank lead to production of polymers which are more resistant to motion. These polymers will be light since it has low density. TX and B acid tar has viscosities lower than HT acid tar, but their densities are higher than that of HT. TX acid tar is more viscous and denser than B acid tar. TX acid tar has more particles which are causing resistance to motion applied and these are also increasing the density. Table 1: Viscosity and density of three acid tars. Acid tars

Viscosity (mPa.s)

Density (g/ml)

B

28.6±0.7

1.519±0.002

TX

183±2.3

1.549±0.004

HT

63592

1.43±0.020


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Danha et al.

Titration of acid tar Fig 1 shows that despite the difference in concentration of acid in the acid tar the two plateaus are showing in all the three acid tars just like Leonard et al., (2010) obtained using sodium hydroxide. 14 12 10

pH

8 pH HT 6

pH TX

4 2 0 0

5

10

15

20

25

30

volume of sodium hydroxide (ml)

Fig 1: acid tar titration with sodium hydroxide of the three acid tars. There is a strong possibility of the presence of both organic (weak) acids and inorganic (strong) acids in the acid tar since they behave differently with weak acids partially dissociating and strong acids completely dissociating. The rst sharp raise at pH of 4 is as a result of complete neutralization of the strong acid (sulphuric acid). The second sharp raise is then from the weak organic acid which take time to dissociate due to the fact that equilibrium will have been reached between the acid and the dissociated ions. This is what causes the drag that is seen after the rst sharp rise. The drag from the rst plateau though is different with the HT having the longest followed by the Toluene and xylene then the Benzene one as the shortest. This then indicates that HT acid tar has more organic acids than the other two acid tars. TX acid tar has more organic acid than B acid tar as shown by the difference in the drag. Table 2: Acidic concentration of acid tars Acid tars B TX HT

50

Acid concentration (mol/l)

Sulphuric acid concentration(mol/l)

9.5 10.5 8.5


7.5 7.5 4.5

% of sulphuric acid in sample 24.2 23.7 15.4

Organic acid concentration (mol/l) 2 3 4

Danha et al.

The results in Table 3 show that the acid tar concentration from the Holding Tank is less than the one from benzene, toluene and xylene streams, this might be due to the vaporization of the acid into the atmosphere since the tank is open. The pH after dilution of 1g into 100mls of water is HT 1.34, B 1.02 and TX 1.10. The anomaly is the B acid tar; it should have a higher acid concentration than the TX since it has the lowest pH. Fig 1 and the results in Table 3 show that the B acid tar has the same concentration of sulphuric acid with TX acid tar this maybe due to the amount used in the puri cation since these are fresh acid tars. Thus the same amount of sulphuric acid is being used in the puri cation of benzene, toluene and xylene. The two acid tars differ in the concentration of organic acids. TX acid tar has more organic acid than B acid tar this can be because B acid tar has fewer organic compounds as compared to TX acid tar. The organic acid at this point can not be as a result of reaction between sulphuric acid and organic compounds in the two fresh acid tar. HT acid tar has the lowest concentration of sulphuric acid and the highest concentration organic acid. This acid tar is not fresh and the concentration of sulphuric acid is expected to be the same as the B and TX acid tar since it is a mixture of the two. But because of the fact that it is exposed to the atmosphere the concentration of sulphuric acid is low. The sulphuric acid has been consumed in the production of the organic acid (acidi cation of organic compounds) and some might have been lost into the atmosphere.

Solubility Table 3 shows that a higher percentage of acid tar is soluble in water with benzene stream having the highest (94.31%), toluene and xylene stream having the second (73.44%) and Holding Tank having the least (70%). Table 3: Acid tar solubility in % Solvent Water Methanol

TX acid tar 73.44±0.21 94.2±1.3

B acid tar 94.31±1.18 87.0±1.4

HT acid tar 70 96.0±0.6

In the entire solubility test TX seems to be very similar or close to the HT acid tar. B acid tar is different from the other two; their solubility is increasing as you go from water to methanol while for B acid tar the increase in solubility is from methanol to water. This shows that b acid tar has less organic compounds than TX and HT acid tar.


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(x100,000,000) 2.5TIC (1.00) 2.0 1.5 1.0 0.5 0.0

5.0

7.5

10.0

12.5

15.0

17.5

20.0

22.5

25.0

27.5

30.0

Fig 2: B acid tar chromatography

2.00(x10,000,000) TIC (1.00) 1.75 1.50 1.25 1.00 0.75 0.50 0.25

5.0

7.5

10.0

12.5

15.0

17.5

20.0

22.5

25.0

27.5

30.0

20.0

22.5

25.0

27.5

30.0

Fig 3: TX acid tar chromatography

(x100,000,000) 3.0 TIC (1.00) 2.5 2.0 1.5 1.0 0.5 0.0 5.0

7.5

10.0

12.5

15.0

17.5

Fig 4: HT acid tar chromatography Fig 2, Fig 3 and Fig 4 show the chromatograph of the three acid tars dissolved in toluene. The chromatograph can be used to estimate the difference in the amount of organic chemicals soluble in toluene of the three acid tars. B acid tar has the least with TX acid tar being average and HT acid tar having the most of organic compounds soluble in toluene. Compound two in Table 4 under the B acid tar column also was found in HT acid tar and is compound one in the HT acid tar

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column. TX acid tar had a compound that was also in HT, compound eight in the TX column and is compound twelve in the HT acid column. The two scenarios show that both B and TX acid tar represented in the HT acid tar. Table 4 shows that there are more organic compounds in HT acid tar than there are in B and TX acid tar. Table 4: Organic compounds in the three acid tars. 1.

2.

3.

4.

5.

6.

7.

8. 9.

1 0. 1 1.

1 2.

B acid tar 3-[(5 -Amino tetrazol -1ylimino) -methyl] phenol (Alcohol) 3-Ethylidene -2methyl -1-hexen -4yne (Alkyne) Cyclooctyne (Alkyne)

TX acid tar 2-Phenyl -2H-1,2,3 benzotrial -5-amine (Amine)

HT acid tar 3-Ethylidene -2-methyl -1hexen -4-yne (Alkyne)

Phenyl carbamate (Amide)

Benzonitrile oxide (Nitro compound)

1-Methylene -1Hindene (Alkene)

Isobutyl 2 -ethoxy1(2H) quinolinecarboxyla te(Ester/ether) 2-Methoxy-2-(2nitroethoxy) propane (Nitro compound) E-1, 5, 9 Decatriene (Alke ne)

2-Chloro -2norbornanecarboxy lic acid (Carboxylic acid) 3-(1-Methyl-1phenylethyl) thiophene (Sulphur compound) 5-(1,1 dimethylethyl) -2,3 dihydro -3,3 dimethyl - 1H-inden1-one (Ketone) 1,4 -Dimethyl -2phenoxybenzene (Ether) N-(2-Phenylethyl) benzamide (Amide) 2-Benzoylamino -3phenyl -N-(2phenylethyl) propanamide (Amide)

5-Nitro -2-(4nitrobenzylidenamino) toluene (Nitro compound) 3-Methyl- phenol (Alcohol)

N[(Phenylmethoxy)carbonyl] - DL-alanine (Carboxylic acid) N-(4-Nitrobenzylideno) quinolin -6-amine (Nitro compound)

Benzenepropanal (Aldehyde) Benzocyclo heptatriene (Alkene) 1,2 -dimethyl -4(phenylmethyl) – benzene (Aromatic)

1-(o-Ethylphenyl) -1phenyl - ethane (Aromatic) 2-(1,3 -Dihydro-3,3 dimethyl -1-phenyl -3,4 benzofuran -1-yl) acetic acid (Carboxylic acid) N-(2-Phenylethyl) benzamide (Amide)


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Fourier transform infrared spectroscopy results

120

Stream five 10-10-14 110 100 90

5

%Transmittance

80 70 60 50 40 30 20 10 0 4000

3500

3000

2500

2000

1500

1000

Wavenumbers (cm-1)

Fig 5: FTIR benzene acid tar

120

Stream 6 110 100 6

90

%Transmittance

80 70 60 50 40 30 20 10 0 4000

3500

3000

2500

2000

Wavenumbers (cm-1)

Fig 6: FTIR of Toluene and xylene acid tar

54


1500

1000

Danha et al. 120 110 100 90

% Transmittance

80 70 60 50 40 30 20 10 0 4000

3500

3000

2500

2000

1500

1000

Wavenumbers (cm-1)

Fig 7: FTIR of holding tank acid tar Fig 5, Fig 6 and Fig 7 show the spectrum for the three acid tars with common bands of wave number being observed in the three spectrums. The rst band is at 1600cm-1 which is for alkenes thus the three acid tars have an alkene or –C=C-. HT acid tar has a more reduced transmittance as compared to B and TX acid tars at this wave number showing it has more alkenes than B and TX acid tars. This is also supported by the number of compounds (3) that have a -C=C- bond in Table 4 under the HT acid tar column. The other common band was 1100cm-1which is for alcohols and is found in all the three acid tars. TX however has no alcohol and Coates (2000) also indicated that it can be due to the presents of secondary amines. TX and HT have one at 1050cm-1 which is for amines. B acid tar had bands at 3510 and 3400cm-1, TX had a reduced transmittance at 3440 and HT at 3350cm-1 all representing the presence of nitro compounds in the three acid tars. For aromatic compounds B and TX acid tars had a ban

CONCLUSION B acid tar has the lowest viscosity (28.6 ±0.7) and HT acid tar has the highest viscosity (63592). TX acid tar has the highest density (1,549±0.004) and HT acid tar has the lowest density (1.43±0.020). The fresh acid tars have sulphuric acid concentration that is higher than the HT acid tar and yet the HT has the highest concentration of organic acid. The sulphuric acid concentration for all the acid tars is less than 25% thus recovery of sulphuric acid will be difficult. The organics that are contributing to acidity in the three acid tars are not the same. B acid tar had an alcohol and an ester while TX had carboxylic acid and ketone and HT acid tars had two carboxylic acids,


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an alcohol, and an aldehyde. This then explains the drag that is after the neutralization of sulphuric acid in TX and HT acid tars, which is bigger than that of the B acid tar. B acid tar has the lowest number of organic compounds followed by TX then HT acid tar. d stretching from 3150-3000cm-1while the one for HT was at 1480cm-1.

REFERENCES Aminov. A. N and Karpova. I. V. 1989. Production of binders from acid pond tar, Plenum Publishing Corporation. Burtanaya. I. A, Gachechiladze. O.O, Mitin. A. V, Prokhorov. S. A, Ruzhinskaya. L. I and Shafarenko. N. V. 2007. Membrane technology for processing of acid tars, Chemistry and Technology of Fuels and Oils, 43:521-523. Catney. P, Lawson. N, Palaseanu-Lvejoy. M, Shaw. S, Smith. C, Stafford. T, Tabot. S and Xuhao. 2005. Acid tar lagoons: risks and sustainable remediation in an urban context, paper presented to the SUBR: IM Conference March 2005. Chojnacki. A, Chojnacka. K and Gorecki. H. 2005. Utilization of spent petrochemical sulphuric acid in the production of wet process phosphoric acid, Journal of chemical technology and biotechnology, 80:1331-1338. Coates. J. 2000. Interpretation of infrared spectra, A practical approach. Encyclopedia of analytical chemistry, R. A. Meyers (Ed), pp. 10815-10837. John wiley and sons Ltd, Chichester. Frolov. A. F, Aminov. A. N and Timrot. S. D. 1981. Composition and properties of acid tar and asphalt produced from acid tar. Plenum publishers. Frolov. A. F, Titova. T. S, Karpova. I. V and Denisova. T. L. 1986. Composition of acid tars from sulphuric acid treatment of petroleum oils. Plenum publishers. Hu. L, Zhou. Y, Zhang. M and Liu. R 2012. Characterization and properties of a lignosulfonate based phenolic foam, Bioresources, 7:554-564 Kempe. C, Bellmann. C, Meyer. D and Windrich. F. 2005. GC-IR based two dimensional structural group analysis of petroleum products, Anal bioanal chem. 382:186-191.

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Kolmakov. G. A, Zanozina. V. F, Khmeleva. M. V, Okhlopkov. A. S, Grishin. D. F and Zorin. A. D. 2006. Group analysis of acid tars. Petroleum chemistry, 46(1):16-21. Ku. C. S and Mun. S. P. 2006. Characterization of pyrolysis tar derived from lignocellulosic biomass, Industrial chemistry, 12:853-861 Leonard. S. A, Stegemann. J. A and Roy. A. 2010a. Characterization of acid tars, Hazardous material, 175:383-392 Nancarrow. D. J, Slade. N. J and Steeds. J. E. 2001. Land contamination: Technical guidance on special sites: Acid tar lagoons, Environment agency UK. Nichol, D. 2000. Geo-engineering problems at Hoole Bank acid tar lagoon, Cheshire, UK. Land Contamination & Reclamation, 8:167-173. Puring. M. N, Neyaglov. A. V, Kruglova. T. A, Bituleva. L. A, Gorbacheva. N. A and Startsev. Yu. V. 1990. Composition of acid tars from production of oils. Plenum Publishing Corporation. Rincon. J, Canizares. P and Garcia. M. T (2005) Waste oil recycling using mixtures of polar solvents, Industrial Engineering chemistry resources, 44:7854-7859. Semenova. S. A and Patrakov. Yu. F. 2007. Effect of ozonation on the composition of crude coal-tar benzene, Russian journal of applied chemistry, 80: 846-850. Semenova. S. A, Gavrilyuk. O. M, Zaostrovskii. A. N, Fedorova. N. I and Ismagilov. Z. R. 2012. Modi cation of coal tar in low temperature oxygen plasma, Coke and chemistry, 55:277-281. Tumanovskii. A. G, Kosobokova. E. M and Ryabov. G. A. 2004. Production of energy carriers as a method of utilizing the bottom layer of acid tar. Chemistry and technology of fuels and oils, 40(6):351-357. Zilic-Fiser. S and Dvorsak. S. 2010. The model of an effective public communication in remediation of acid tar dump: case of Pesniski dvor.


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Objective selection criteria and mating strategy of indigenous Nguni cattle under low-input in-situ conservation programs 1 *Tada, O., 2Muchenje Vand 3 Dzama, K Department of Animal Production and Technology, Chinhoyi University of Technology, P. Bag 7724, Chinhoyi, South Africa. 2 Department of Livestock and Pasture Science, University of Fort Hare, P. Bag X1314, Alice 5700, South Africa. 3 Department of Animal Sciences, Stellenbosch University, P. Bag X1, Matieland 7602, South Africa. *Corresponding Author: email: [email protected] 1

ABSTRACT Participatory Rural Appraisal techniques were employed to determine the breeding objectives of Nguni cattle under community-based management of indigenous livestock genetic resources. Six groups each composed of nine representative farmers from communal and small-scale conservation enterprises participated in deriving the objective selection criteria of breeding animals using data on economic weights of preferential traits. The shuffled focus groups brainstormed on the mating strategy and management of breeding animals within low-input conservation enterprises. An economic-weight dependent culling method (EWCM) and two-tier open nucleus breeding scheme were conceptualized. The Nguni breeding animals ideally need to maintain optimum body condition score (4 - 6) and low tick counts across seasons under low-input production system. The indigenous breeding bulls need to have high reproductive efficiency while breeding cows must have calved before reaching 27 month age. The farmers set a two-and-half-year service period of breeding bulls in the in-situ conservation enterprise before culling. Farmers are recommended to objectively assess breeding animals and maintain an updated performance data and information recording system. Key words: economic weight-dependent culling, focus group discussion, preferred traits, two-tier open nucleus breeding

INTRODUCTION Quanti cation of the levels of economic bene t associated with growth, fertility and adaptability traits expressed by farmed livestock has been a central issue in the development of breeding objectives (Roessler et al., 2008; Kassie et al., 2010). Furthermore, it was noted that in developing countries where animal production is still mostly subsistence-oriented and livestock ful l many functions (Tada et al., 58


Tada et al.

2012), a considerable number of breeding programs have failed due to lack of smallholders' participation in the planning and designing phase (Kosgey et al., 2006). This necessitates the input of the rural cattle producers in formulating the breeding objectives of a conservation program intended to bene t them. The in-situ conservation program of the indigenous Nguni cattle, pioneered by the University of Fort Hare, has been in place for two cattle generations (6-7 years) in the Eastern Cape Province of South Africa. Efforts by the Industrial Development Cooperation, Department of Rural Development and Agrarian Reform and other academic institutions resulted in active participation of other provinces in preserving the Nguni cattle (IDC, 2010). A high number of young bullocks are erupting in the conservation enterprises because of the balanced birth sex ratio observed by Tada et al. (2013a). This also resulted in a high ratio of breeding male to breeding female animals (17%) and a high bulling rate in communal and small-scale conservation enterprises (Tada et al., 2013a). A selection model based on the knowledge of the farmers on preferential traits is justi ed to identify potential productive young breeding bulls for marketing within and outside the rural areas. Selection is possible because genetic and phenotypic variation exist as observed in other studies on health, reproductivity, growth and adaptability of this indigenous breed (Reed, 2008; Nqeno et al., 2010; Scholtz and Theunissen, 2010). The low-input Nguni conservation enterprises are characterised by random mating and a high inbreeding rate has been postulated (Mapiye et al., 2009; Tada et al., 2012). A proper mating strategy may address these breeding concerns as well as other effects of low effective population sizes so as to sustainably maintain the overall goal of community-based in-situ conservation of the indigenous cattle. Some schools of thought had long established that improving food security and alleviating poverty through the conservation of farm animal genetic resources in Africa, as well as utilization of local farm animal populations depends on the ability of communities to decide on and implement appropriate breeding strategies (Wollny, 2003; Gizaw et al., 2010). The selection criteria can be in uenced by socio-economic and biophysical conditions of an area. Hence, different communities may have different criteria or same criteria but different strengths of selection parameters. Therefore, the objective of the study was to determine a farmer-derived selection criteria and mating strategy for young breeding Nguni cattle under low-input production systems. It was hypothesized that, given the proper tools, low-input Nguni cattle farmers are able to make recommendations on the breeding objectives of their enterprises.


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MATERIALS AND METHODS Description of the study sites and selection of participants The study was conducted in the Eastern Cape Province of South Africa in form of a group discussion with 54 farmers from 54 Nguni cattle conservation enterprises representing 75% of the target population. The farmers who participated in the preliminary study on the use of choice experiments to determine economic weights of most preferred traits in young breeding Nguni animals were considered (Tada et al., 2013b). Thirty participants represented communal enterprises while 24 were from small-scale enterprises. The criteria involved selecting a representative farmer, literate and willing to implement cattle recording system. Farmers were rst exposed to interactive discussions on the value of animal records, traits of economic importance and recording. Data and information collection Focus group discussions were used to elicit responses from the farmers on the derivation of the selection model and mating strategy of breeding animals. The discussions were conducted in Xhosa vernacular. Six groups of nine individuals each were randomly created composed of ve and four farmers representing communal and small-scale enterprises, respectively. The small-scale enterprises were de ned as livestock holdings with less than 100ha farm sizes and not exceeding 500 cattle. With the assistance of trained moderators, groups of farmers were presented with economic weights and values of the most preferred trait levels from the previous study involving choice experiments (Table 1 and 2) (refer to Tada et al., 2013b). The traits used in the study were; tick infestation (TI), body condition score (BCS), aggression and mating behaviour (AMB) of bulls, and age at rst calving (AFC) of cows.

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Table 1 Estimates of economic weights and values of traits level in young breeding Nguni bulls Economic Trait Level

weight ± s.e

pvalue

Economic values -R8 494.00

0.987±0.095

p < 0.05

Good Body Condition Score (4 - 6) Over Body Condition Score (7 - 9)

0.447±0.073 Base level

p < 0.05

R3 849.00 R4 645.00

Low Tick Infestation (visible ticks < 10) Medium Tick Infestation (tick count of 10 - 30) High Tick Infestation (tick count of > 30)

0.573±0.103

p < 0.05

R4 927.00

0.581±0.084

p < 0.05

High Aggression and Mating Behavior Average Aggression and Mating Behavior

4.408±0.095

p < 0.05

2.534±0.094

p < 0.05

Low Aggression and Mating Behavior

Base level

R5 001.00 -R9 928.00 R37 939.00 R21 807.00 -R59 746.00

Poor Body Condition S core (1 - 3)

-

Base level

Price

0.001±0.0017

p < 0.05

Constant

10.106±0.375

p < 0.05

NB: Economic value of trait level used as a base is zero (0). US$1.00 = R7.80 (South Africa Reserve Bank, 2011


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Table 2 Estimates of economic weights and values of traits level in rst parity Nguni cows Trait Level

Economic weight ± s.e

pvalue

Poor Body Condition Score (1 - 3)

-0.057±0.055

p> 0.05

-R 413.00

Good Body Condition Score (4 - 6)

1.080 ±0.061

p< 0.05

Over Body Condition Score (7 - 9)

Base level

R7 834.00 -R7 421.00 R10 859.00

Low Tick Infestation (visible ticks < 10) Medium Tick Infestation (tick count of 10 - 30) High Tick Infestation (tick count of > 30)

1.496±0.059

p < 0.05

0.829±0.067

p < 0.05

Age at First Calving ≤ 27 months

2.368±0.068

p < 0.05

Age at First Calving 27 – 36 months

1.303±0.076

p < 0.05

Age at First Calving > 36 months Price Constant

Base level

Base level 0.001±0.0002

p < 0.05

8.973±0.310

p < 0.05

Economic value

R6 015.00 -R16 874.00 R17 185.00 R9 454.00 -R26 638.00

NB: Economic value of trait level used as a base is zero (0). US$1.00 = R7.80 (South Africa Reserve Bank, 2011).

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The group activity involved the objective determination of trait levels that brings the most perceived retains to the enterprise. An independent culling method was “modi ed” to an Economic Weight-dependent Culling Method (EWCM). The EWCM caters for only the positive and signi cant economic weights of trait levels in the selection criteria for the breeding animals. Ranking according to the part worth values was done in descending order on the trait levels under consideration. The group activity also involved discussions on the economically acceptable threshold trait level to be included in the selection model. The effect of the seasonal differences on body condition scores and tick infestation challenge were also discussed by the farmers. Each group made a short presentation of their task to all the participants. Derivation of a mating strategy was achieved through another interactive discussion with randomly shuffled group members. Each group behaved as Nguni conservation enterprise and needed to; (1) identify sources of breeding stock, (2) determine the duration of the breeding bull in the herd, (3) determine methods of identi cation and culling the breeding animals, and (4) device a sound recording and record keeping system. The groups made a presentation of their work and with the help of the workshop moderator the business linkages were formed between the “Nguni conservation enterprises” i.e. participant focus groups. The linkages between “Nguni conservation enterprises” formed through common sources of breeding stock, record keeping system, and destination of culled animals were the basis of formulating a systematic open-nucleus breeding scheme.

Statistical analyses All the descriptive statistics of the demographic factors, frequencies of choices, method of cattle identi cation, duration of breeding bulls in an enterprise, and information on sources of breeding stock, culling and record keeping system were analysed using GenStat 7.2.2 (2008). The trait levels of Nguni breeding cattle were ranked using Kruskal-Wallis test for the order of inclusion in the breeding objective. This was done for the two selection models i.e. rst parity cows and young breeding bulls.

RESULTS A signi cant majority (>50%) of the farmers were above 50 years of age in both communal and small-scale enterprises. No signi cant differences (p > 0.05) were observed in the education levels attained by farmers in communal and small-scale enterprises although primary (42%) and secondary education (46%) had signi cantly high frequencies than college education (12%). It was also observed that 21% of the respondents were females while 79% were males.


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Criteria of selecting young breeding Nguni bulls The criteria of selecting young breeding Nguni bulls were farmer-derived and followed an economic weight-dependent culling method (EWCM) in three steps as explained below and illustrated schematically on Figure 1; Step One: The young Nguni bulls need to have a high score on Aggressiveness and Mating Behavior (AMB). A medium AMB score is only acceptable given that Tick Infestation (TI) score is low and the Body Condition Score (BCS) is good i.e. 4 to 6 on a scale of 1 to 9. Step Two: The TI score need to be medium or low depending on the season where a medium score may be acceptable under hot-wet and post-rain season unlike during the hot-dry and cold-dry season. Step Three: The acceptable BCS need to be in the range of 4 to 6 depending on the season where a score of 4 is acceptable during the hot-dry and colddry season, and a score of 6 in the post rain and hot-wet season.

Criteria of selecting rst parity breeding Nguni cows The criteria followed a three-step procedure presented below and schematically on Figure 2. Step One: The age at rst calving need to be less than 27 months. First-calvers of 27 – 36 months are acceptable only if the TI is low and the BCS is good (4 – 6). Step Two: The TI need to be low. A medium score of TI is only acceptable (a) in the hot-wet and post-rain season, (b) when the age at rst calving is below 27 months and (c) the BCS is 4 – 6 depending on the season i.e. a score of 4 is acceptable during the hot-dry and cold-dry season, and a score of 6 in the post rain and hot-wet season. Step Three: The acceptable BCS need to be in the range of 4 to 6 depending on the season with a score of 4 is acceptable during the hot-dry and cold-dry season, and a score of 6 in the post rain and hot-wet season.

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S T E P

High Aggression and Mating Behavior

Average Aggression and Mating Behavior

O N E

S T E P

Medium Tick Infestation

Low Tick Infestation

(Acceptable during hot-wet season and post-rain season)

T W O

S T E P T H R E E

Body Condition Score 4 - 6

Body Condition Score 4 is lower limit acceptable during hot-dry and cold-dry

Body Condition Score 6 is upper limit acceptable during hot-wet and post-rain




Figure 1 Selection criteria of young breeding Nguni bulls in communal conservation enterprises


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S T E P

Age of rst calving: less than 27 months

Age at first calving: 27 - 36 months

O N E

S T E P

Medium Tick Infestation

Low Tick Infestation

(Acceptable during hot-wet season and post-rain season)

T W O

S T E P T H R E E







Figure 2 Selection criteria of rst parity breeding Nguni cows in communal conservation enterprises

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Mating strategy and management of Nguni cattle conservation enterprises The farmers concurred on a two-tier open-nucleus breeding scheme with a minimum of three enterprises as a mating strategy of the in-situ conservation program. The linkages were formed from common sources of breeding stock. The schematic representation of the breeding scheme is in Figure 3. A continuous breeding season was also highlighted by all farmers. The maximum service period of the breeding bull in the herd of an enterprise was set at two-and-half years. Furthermore, to increase the accuracy of selection, branding was the method of identi cation favoured by most farmers (86%) while others preferred ear-tagging (14%). Farmers agreed when culling the breeding animal to follow the selection criteria of an economic weight-dependent culling method (EWCM) (Figure 1 and 2). All the farmers (100%) indicated a need for a sound record keeping system in form of a booklet in order to implement the selection criteria and mating strategy. The data and information to be captured include; pedigree, sex, phenotypic characteristics, husbandry practices, animal dynamics, reproductive efficiency, and product quanti cation (Figure 4).

DISCUSSION The communal low-input Nguni cattle production is characterised by lack of pedigree records and standard performance data, and information recording (Mapiye et al., 2009; Tada et al., 2012). This makes it difficult to compute genetic parameters (i.e. phenotypic and additive genetic variances and covariances) of the preferred traits by the farmers in the hope of coming up with a selection index. The independent culling level method was modi ed to cater for the limitation of relative economic values of traits and trait levels using results from a preliminary study on choice experiment. The culling levels considered were based on positive and signi cant economic weights to give the name “Economic Weight-dependent Culling Method”. Only three traits were considered in the formulation of the breeding objectives in an effort to maximize genetic progress in any one trait (Hazel and Lush, 1943; Hazel et al., 1994).


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S

Y

X Communal Nguni Enterprise A

Communal Nguni Enterprise C

X S Y

Y Communal Nguni Enterprise B

X S

Enterprise exists include; Productive breeding bulls (Y), Infertile heifers, cull cows and unproductive breeding bulls (X). Enterprise entries include; Productive breeding bulls and cows and heifers from genetically distant commercial stud herds (R, S, T e.t.c), and Proven animals from other enterprises (Y).

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Figure 3 Schematic representation of the two-tier open nucleus breeding scheme for Nguni cattle conservation enterprises.

Figure 4 Individual animal record sheet for capturing performance data and information Under smallholder production systems, conventional breeding methods are constrained by absence of individual animal identi cation and records, low level of literacy, small herd sizes per household and uncontrolled breeding (Mapiye et al., 2009; Tada et al., 2012). To design viable genetic improvement schemes under small-scale sector, the prevailing production conditions and/or systems and production goals must be fully understood. The views of the targeted communities were accounted for through focus group discussions as all farmers had an equal opportunity to express their ideas. Farmers of indigenous Sheko cattle in Ethiopia reported a success story achieved through focus group discussions (Desta et al., 2011). Because breeding and conservation programs are becoming increasingly cognisant of factors such as sustainability with many intangible bene ts, the views of the farmers were considered very crucial in this low-input conservation system. Though the majority of farmers indicated preference for branding their cattle as a


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way of identi cation, this may be because it is a cheaper method compared to eartags and the reading is visible from a distant. This is important to the rural enterprises as it limits labour use and injuries associated with handling untamed cattle. Consideration of preferential traits that farmers understand, easily measure and record as well as derive direct economic value is seen as a way to increase the accuracy of selection on those traits and overall genetic progress. The involvement of farmers in the determination of the EWCM and a two-tier open nucleus mating strategy in upgrading the rural livestock and in-situ conservation of Nguni cattle is an approach to increase the adoption level of the intervention. It has been established that livestock development interventions in the smallholder sector of developing countries had been missing the farmer participatory component (Wollny, 2003; Kosgey et al., 2006; Roessler et al., 2008). Such participation in the planning and design of breeding programs is set to encourage success. In a study conducted by Mapiye et al. (2009) in the Eastern Cape Province of South Africa in communal and small-scale sector, farmers revealed that adaptability and growth traits are the most treasured traits in selecting beef breeds and breeding stock. Therefore, involving farmers in selecting traits for genetic improvement is a forward step towards the adoption of a breeding model at community level where communal property is in the hands of many. The use of economically viable traits in the selection criteria has also been reported, through choice experiment procedures, in Vietnam where adaptive and performance traits were preferred particularly in resource-driven/subsistence production systems (Roessler et al., 2008). These ndings had similar meaning under this study where reproductive efficiency, tick and disease resistance and animal body condition have positive implications on the breeding objectives. Animal performance recording systems have been known for long to affect genetic improvement programs (Kahi et al., 2003). An establishment of performance data and information recording system for these rural enterprises is seen as a basis of formulating a database for animal evaluation. For accurate performance evaluation in terms of genetic and phenotypic trends, computation of genetic parameters, selection criteria and mating system designs, the cattle records are fundamental. In many cases, breeding programs are only implemented successfully where accurate recording is possible. This accurate record keeping requires money, expertise and a well-developed infrastructure, which is partially or completely lacking in most rural areas of developing countries (Rege et al., 2001). The UFH Nguni cattle restoration program assisted the rural farmers on that regard. In Kenya, nucleus breeding schemes were developed to circumvent the high costs arising from performance recording and selection

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(Rege et al., 2001). Therefore this open nucleus scheme can be a good strategy for genetic improvement in the rural areas of Eastern Cape Province of South Africa where the expertise and structures required for operating an efficient genetic improvement program are minimal. Bondoc and Smith (1993) recommended the establishment of two-tier open nucleus breeding systems to maximise genetic improvement, reduce inbreeding rate and reduce the total cost of recording in the participating herds. Open nucleus systems provide approximately 10% more genetic gain than a closed system because there are more animals which are potential candidates for selection. This system has potential to integrate farmers' resources, reduce overhead costs and encourage more farmer participation (Bondoc and Smith, 1993; Wollny, 2003). The advantages of a two-tier open nucleus include; 1) generation of genetic gain with sire selection as the main activity, 2) movement of bulls from the nucleus to sire progeny in the other communal and or small-scale conservation enterprises, 3) introduction of dams born in the participating enterprises selected objectively on easily and cheaply measured traits, and 4) selection in the participating enterprises i.e. bulls born in the nucleus are used to produce cows and breeding bulls in other genetically distant enterprises while dams in the herds are used to produce both bulls and cows in this and other production systems. The groups of farmers concurred with each other and set a two-and-half year service period limit for a breeding bull in an enterprise. This was because the average age at rst calving of the Nguni breed was observed by the farmers to be 31 months and the breed standards accept 39 months (Nguni Cattle Breeders Society, 2011), an approximate period that would preclude the breeding bull to mate its daughters. The breeding bull would leave the enterprise at the time when its rst crop of heifers are about to be serviced. In this way, formation of inbred lines is discouraged as mating is controlled despite the absence of a de ned breeding season. Farmers amicably defended the idea of continuous roaming of breeding bulls and breeding cows given the nature of the community resources as well as the difficulty in maintaining camps and separating breeding bulls. Cattle dipping frequency ranged from 1-2 times per month, farmers dipped their cattle more in the hot–wet and hot–dry seasons than the post-rain and cold–dry seasons (Tada et al., 2013a).

CONCLUSIONS AND RECOMMENDATIONS Farmers managed to de ne the enterprise breeding objective in terms of economic-weight dependent culling method and a two-tier open nucleus breeding scheme. The selection method is an improved version of the


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independent culling method and it is closer to a selection index. The basis of identi cation of superior breeding animals was the performance records of individual animals using preferential traits that farmers understand, easily measure and see a direct economic value. The farmers set a two-and-half year maximum service period for breeding bulls in an enterprise before exchanging or culling. The farmer-determined breeding objectives form an enabling policy for a sustainable community-based management of indigenous cattle genetic resources. It is recommended for farmers to implement cattle recording system and objectively assess livestock performance. The economic-weight dependent culling method and a two-tier open nucleus breeding schemes are available tools for in-situ conservation of Nguni cattle in the rural enterprises.

ACKNOWLEDGEMENTS The authors are grateful to the farmers under the UFH Nguni Cattle Program in the Eastern Cape Province for cooperation during the study period. The project was funded by Adam Fleming through the Nguni Project Operations (P329) of the University of Fort Hare.

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REFERENCES Bondoc, O.L., Smith, C. 1993. Deterministic genetic analysis of open nucleus breeding schemes for dairy cattle in developing countries. Journal of Animal Breeding and Genetic, 110: 194 – 208. Desta, T.T., Ayalew, W., Hegde, B. P. 2011. Breed and trait preferences of Sheko cattle keepers in south-western Ethiopia. Tropical Animal Health and Production, 43(4): 851 – 856. GenStat Release 7.2. 2008. Discovery Edition 3, VSN International Ltd, UK. Gizaw, S., Komen, H. and van Arendonk, J.A.M. 2010. Participatory de nition of breeding objectives and selection indexes for sheep breeding in traditional systems. Livestock Science, 128 (1): 67 – 74. Hazel, L.N., Lush, J.L. 1943. The efficiency of three methods of selection. Journal of Heredity, 33: 393 - 399. Hazel, L.N., Dickerson, G.E., Freeman, A.E. 1994. Symposium: Selection index theory. The selection index – Then, now and for the future. Journal of Dairy Science, 77: 3236 - 3251. Industrial Development Cooperation. 2010. IDC Newsletter. Available at http://www.idc.co.za/access/includes/htmlnewsletter/pdf/full_newletter.pdf Accessed on 21August 2011.

Kahi, A.K., Barwick, S. A., Graser, H.U. 2003. Economic evaluation of Hereford cattle breeding schemes incorporating direct and indirect measures of feed intake. Australian Journal of Agriculture Research, 54: 1039 - 1055. Kassie, G.T., Abdulai, A., Wollny, C. 2010. Implicit Prices of Indigenous Bull Traits in Crop-Livestock Mixed Production Systems of Ethiopia. African Development Review 22 (4): 482 – 494. Kosgey, I.S., Baker, R.L., Udo, H.M.J., van Arendonk, J.A.M. 2006. Successes and failures of small ruminant breeding programs in the tropics: a review. Small Ruminant Research, 61: 13 – 28. Mapiye, C., Chimonyo, M., Dzama, K., Raats, J.G., Mapekula, M. 2009. Opportunities for improving Nguni cattle production in the smallholder farming systems of South Africa. Livestock Science, 124: 196 - 204. A Journal of Chinhoyi University of Technology

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Nguni Cattle Breeders Society. 2011. Nguni 2011 25 Years – Breed from the past for the future. Nguni Cattle Breeders Society. Bloemfontein, South Africa. Page 35. Nqeno, N., Chimonyo, M., Mapiye, C., Marufu, M.C. 2010. Ovarian activity, conception and pregnancy patterns of cows in the semiarid communal rangelands in the Eastern Cape Province of South Africa. Animal Reproductive Science, 118: 140 – 147. Reed, D. 2008. Does size count; in Nguni 2008, Pendulum Visual Communication, Bloemfontein, South Africa, 89. Rege, J.E.O., Kahi, A.K., Okomo-Adhiambo, M., Mwacharo, J., Hanotte, O. 2001. Zebu cattle of Kenya: Uses, performance, farmer preferences, measures of genetic diversity and options for improved use. Animal Genetic Resources Research 1. ILRI (International Livestock Research Institute), Nairobi, Kenya. 103 pp. Date accessed: 29 June 2012. http://agtr.ilri.cgiar.org/documents/Library/docs/zebucattle/5Breeding.html#To pOfPage Roessler, R., Drucker, A.G, Scarpa, R., Markemann, A., Lemke, U., Thuy, L.T., Zárate, A.V. 2008. Using choice experiments to assess smallholder farmers' preferences for pig breeding traits in different production systems in North–West Vietnam. Ecological Economics, 66: 184 – 192. Scholtz, M.M., Theunissen, A. 2010. The use of indigenous cattle in terminal crossbreeding to improve beef cattle production in Sub-Saharan Africa. Animal Genetic Resources, 46: 33 – 39. Tada O, Muchenje V., Dzama K. 2012. Monetary Value of Nguni cattle and socioeconomic pro les of farmers in the low-input communal production system of Eastern Cape Province, South Africa. African Journal of Business Management, 6 (45): 11304 – 11311. Tada O, V. Muchenje and K. Dzama. 2013a. Reproductive efficiency and herd demography of Nguni cattle in village-owned and group-owned enterprises under low-input communal production systems. Tropical Animal Health and Production 45 (2). DOI 10.1007/s11250-013-0363-x. ISSN 0049-4747. http://link.springer.com/content/pdf/10.1007%2Fs11250-013-0363-x.pdf

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Tada O, Muchenje V, Madzimure J and Dzama K. 2013b. Determination of economic weights for breeding traits in indigenous Nguni cattle under in-situ conservation. Livestock Science 155 (1): 8-16. http://www.springerplus.com/content/pdf/2193-1801-2-195.pdf Wollny, C.B.A. 2003. The need to conserve farm animal genetic resources in Africa: should policy makers be concerned? Ecological Economics, 45 (3): 341 – 351.


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Conservation Agriculture challenges in developing countries and possible suggestions - the case of Gokwe South District, Zimbabwe Mashango, G. CIMMYT Southern Africa Head Office, P.O. Box 163 Mt Pleasant, Harare, Zimbabwe Email:

ABSTRACT Globally, food insecurity is a huge challenge, especially among developing nations. The severity of the problem varies from one continent to the other. Development practitioners, researchers, government leaders and scientists are struggling to come up with a sustainable solution in addressing food insecurity. Conservation agriculture (CA), which is a concept for resource-saving agriculture crop farming system that strives to achieve acceptable pro ts together with high and sustained production level while concurrently conserving the environment is one of the potential remedy to food shortage. CA is characterized by three major principlesminimum soil tillage, soil cover (mulch) and crop rotation. CA is widely perceived as one way of sustainably addressing food insecurity not only in Africa but also in other developing countries globally. Research has shown that CA when properly practised can lead to increased yield, improved soil structure and increased utilization of agricultural resources. Despite CA's numerous bene ts, some farmers in developing nations are reluctant to adopt the farming system. The reasons behind this are immense and diverse and this study aimed to achieve the following objectives: (i) to assess why there is low uptake of CA, (ii). to assess contribution of CA to food security (iii). to recommend strategies and appropriate approaches in resolving food insecurity. A total of four wards of Gokwe South District were purposively sampled and 403 households were interviewed. Evidence from survey results indicated that although CA contributes signi cantly to household food security for smallholders 'as a best practice' itis not a 'best t' practice since results uctuate from one agro-ecological zone to the other. It was found out that low uptake of CA is emanating from high labour requirements, multi-usage of crop residue in mixed farming systems, lack of knowledge and poor markets. CA should not be promoted as a full package but as farming options for the farmers to choose what is appropriate to them. Introduction of conservation agriculture in Zimbabwe was input driven supported mostly by non-governmental organisations hence sustainability of the concept is highly questionable. CA should be promoted using developmental approaches which are more sustainable than humanitarian. 76


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Key words: : Sustainability, Conservation Agriculture, Food Security, Smallholder farmers, Household

INTRODUCTION Conservation Agriculture (CA) is increasingly perceived by the research and development community as the way forward in attaining food security particularly in developing nations (Gupta and Sayre 2007; Hobbs 2007; ; Thierfelder and Wall, 2010).CA is a concept for resource-saving agriculture crop farming system that strives to achieve acceptable pro ts together with high and sustained production level while concurrently conserving the environment is one of the potential remedy to food shortage. CA is characterized by three major principles - minimum soil tillage, soil cover (mulch) and crop rotation. Scientists have now reached a common understanding on the inevitability of global warming and that it will have serious impacts on global climate and agriculture productivity. Hence the use of a sustainable ways of farming such as CA is of paramount importance (Friedrich et al., 2012). African countries are facing severe food insecurity which is directly linked to population growth and massive land degradation. Under this scenario innovative farming systems like CA which increases productivity as well as conserving environment. Professed conservation agriculture bene ts are increased soil organic matter, improvements in water harvesting, reduction of the risk of crop failure, increased and stabilised yields, reduction in soil erosion, improvement in soil structure, reduced pests and diseases, reduced weed germination, and increased productivity (Derpsch et al., 2010; Li et al., 2011; Marongwe et al., 2011). Conservation agriculture preserves soil fertility which is in line with current and globally promoted climatic change mitigation strategies. Conservation agriculture also involves reduced burning of fuel during land preparation hence the farming system reduces the depletion of ozone layer. Despite the perceived bene ts of conservation agriculture, its adoption in most parts of Africa is low (Kassam et al., 2009). Friedrich et al. (2012), noted that less than 1% of cropped land in Africa is under conservation agriculture and globally it accounts for only 8 % of arable and permanent cropped land. The focus of the study is to assess why farmers are reluctant to adopt CA since it yields positive results particularly in boosting productivity and conserving environment.


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MATERIALS AND METHODS Both qualitative and quantitative data were analysed in a single study. The main drive why the two were combined is that they provide a better understanding of the research problem. One type of research: qualitative or quantitative, was not enough to answer the research objectives. The research questions comprise of qualitative information, for instance, farmer's perceptions, experiences, challenges and prospective views towards attributes of conservation agriculture to food security. Within the research framework, it was noted that to fully answer the research goal, qualitative information was to be augmented by quantitative information like yields, metric tonnes per conservation agriculture farmer per hectare. Quantitative data were crucial in triangulating qualitative information. Combining both qualitative and quantitative research methods comprehensively addresses research thrust. The data collection methods used includes household (H/H) in-depth interviews, Key Informant Interviews (KII), Focused Group Discussions (FGD) and Most Signi cant Change (MSC). These tools were complemented by observation technique (On site visual inspection) through farmer- eld visits. The data collection tools were designed to answer the research questions which were directly linked to study objectives. A total of 403 households were interviewed during data collection in 2013/2014 farming season.

RESULTS It was found out thatfactors behind food insecurity were found to be immense, diverse and interlinked. The survey revealed that drought, unavailability and unaffordability of inputs, lack of productive assets, poor infrastructure, pest and diseases and poor markets are root causes of food insecurity in Gokwe South District. Severity of these factors to food security varies from one place to the other. Similar observations were made by Rosegrant et al. (2001) who concluded that food shortages in Southern Africa are an on-going problem, and long-term projections suggest that regional food production per capita is likely to diminish in future. Although increase in productivity was noted from the CA plots numerous problems which hinders uptake of the innovative farming system. CA was perceived by farmers as labour demanding hence majority of smallholder farmers are unable to adopt the technology. CA's high demand for labour is attributed mainly to land preparation as farmers in Gokwe indicated that basin formation, precision planting and weeding was more difficult in mulched elds as compared to bare elds.

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Cross tabulation of labour status and yield output during the survey revealed that farmers with average labour force and large labour force have comparative advantage in terms of getting higher yields as compared to farmers with small labour force. The table below shows cereal sufficiency of farmers in relation to the sizes of the labour force. The tabulation below analysed only hand hoe based CA which is referred to as conservation farming (CF) in Zimbabwe.

Cereal sufciency by farmers status and labour force size 120% 100% 80% 60%

9 to 12 months

40%

5 to 8 months

20%

less than 5 months

0% CF Small Non CF Small Labour Labour force force

CF Non CF CF Large Non CF Average Average Labour Large Labour Labour force Labour force force force

Fig 1: Cross tabulation analysis of labour size per household and CA yields. Note the small labour forces constitute less than 3 able bodied members, average labour force has 5 able bodied and large labour force consist of more than six able bodied members. N = 403 households. The above table shows that cereal sufficiency of farmers improve with conservation agriculture participation and increase in labour force size (labour units). The results show that 82% of conservation agriculture practicing households with average labour force had a cereal sufficiency of 9 to 12 months compared to 50% of their non- conservation agriculture counterparts. Households with small labour size struggled to achieve cereal sufficiency of 9-12 months, for instance only 3% of conservation agriculture participants with small labour force had a cereal sufficiency of 9-12 months. The majority of labour constrained households had a cereal sufficiency of 5-8 months, with 82% and 75%


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of conservation agriculture and non- conservation agriculture farmers falling in this category respectively. Therefore, conservation agriculture farmers with a big labour force got higher yields compared to farmers with a small labour force. Besides labour, some farmers in Gokwe South district identi ed soil cover, precision management, crop rotation and minimum soil disturbance as some of the challenges facing conservation agriculture farmers. Over 90% of the farmers interviewed mentioned mulching as one of the major problems that affect them. Low biomass production, termites problems, alternative use of crop residue such as animal feeds (free grazing system), domestic fuel, construction and burning of residue, pests and diseases were identi ed as problems that impact negatively on conservation agriculture systems. Various reputable researchers shared similar observations on mulching (Umar et al., 2012; Aune et al, 2012; Valbuena et al., 2012; Marongwe et al., 2011 and Giller et al., 2009). Survey results indicated that mulch proved to be one of the most difficult CA principals. Majority of the CA farmers collect crop residue and keep them at a protected area soon after harvest then retain residue to the eld during farming season. This is done as way of addressing free grazing challenges since livestock consume residue in the eld. The idea is good but the soil will be exposed to heat wind and water during off farming season. This also affects the soil organic ecosystem which is fundamental in enhancing soil fertility. Therefore, there is need of coming up with a strategy to protect residue speci cally in free grazing communities. The farmers were asked on the type of mulch they use in the CA elds. A total of 3% of the farmers indicated that they used maize stover while 28% used a mix of grass and stover. Only 2% of the farmers indicated using no mulch in their elds. Through FGDs and key informant interviews, it emerged that the mulch types used had multiple uses and thus a household was faced with a task on how to secure mulch for the CA elds.

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Mulch Material used by CA farmers in Gokwe

Figure 1: Mulching materials in Gokwe Maize stover is a supplementary livestock feed during winter and as such little is left for the elds. All interviewed CA farmers mentioned mulching as one of challenging tasks in practising CA. Key informants for example AGRITEX officers and local leaders revealed numerous reasons linked to mulching glitches. These include low biomass production, termite's problems, alternative use of crop residue like animal feeds, domestic fuel, construction e.g. thatching and fencing, burning of residue as a traditional means of controlling weeds, pests, insects and rodents. Mulch is of paramount importance in reducing surface run-offs, improving rain water in ltration, suppressing and controlling weed growth, etc. (Hobbs, 2007; FAO, 2008; Giller et al., 2009). Farmer group discussions during the survey showed that farmers were conscious of the long term bene ts of mulching their elds. The challenge was how to balance crop and livestock farming since farmers' depend on livestock as a livelihood source, not only during drought periods but also for basic amenities. There is very high interdependence between crop and livestock production among small scale farmers. In Zimbabwe livestock is used as draught power, meat A Journal of Chinhoyi University of Technology

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and to produce organic manure. There is evidence suggesting that aspects of conservation agriculture can con ict with some of the livestock production practices (Valbuena et al, 2012).

DISCUSSION CA labour reduction was literally prescribed from industrialized nations like Argentina, Australia, Brazil and United States of America who adopted minimum tillage as a way of reducing labour costs (Gonzalez, 2012; Kassam et al., 2009). The reduced labour costs were mainly from low fuel requirement for tillage emanating from minimum tillage. Small scale farmers in Africa farm mainly for subsistence hence they do not use sophisticated equipment like tractors, planter and disc harrows. The different context and characteristics of farmers led to nonhomogeneous results for instance CA increased labour for small scale farmers in Africa yet the same concept is reducing drudgery costs in industrialised nations. In any technological transfer or expansion to other countries it is very important to consider the environmental conditions, not only agro-ecological factors but also level of technology implements. A very good example in support of this view is China which is one of the fast growing industrialised countries in the world where adoption rate of CA remains very low. The current statistics show that China has about 3 million hectares under CA compared to about 26 million hectares in United States of America and Argentina (FAO, 2008). In China existence of cheap labour led to the low uptake of CA speci cally minimum tillage. According to Wang et al. (2010) the adoption rates of CA technology (either in full or partial) in China is still low; especially the full adoption of CA is almost zero. According to Jat et al. (2014) the main factors behind uptake of CA by Chinese farmers are low labour cost and low share of machinery and fuel in the total cost of cultivation which gives little incentive to them to embrace CA technology. Looking closely to countries with high uptake of CA for instance Argentina, Australia, Brazil and United States of America were the main motivator was to reduce tillage costs. Further analysis on intensity of labour requirements revealed that in Gokwe over 90% of the farmers are making plant basins using hoes and they are not using herbicides. On the same vain it is critical to note that herbicides are not part of the three principles of CA. Therefore if CA concepts are applied in different worldwide it is not correct to generalize ndings. The Gokwe survey showed that CA is labour intensive during land preparation and the weeding stage as farmers use hand hoe based system commonly referred to as conservation farming (CF). The demand for labour is also high in the rst two years of CA adoption and this negatively affects 82


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the uptake of the technology as most farmers lack resources to buy herbicides. Herbicides when correctly applied help to reduce the intensity of labour requirements. Andersson and Giller, (2012) concur with the above observation and say that herbicides are one of the most effective labour saving technologies available to farmers. The question which is open for further exploration is to what extend can farmers depends on herbicides when the majority of African smallholders are resource-constrained? In support of high labour requirements Ndlovu et al., (2015) concluded that CA preparation is one of the most common challenge which impedes large-scale adoption of the technology particularly in an environment where mechanisation or herbicides are not available or affordable to farmers. During MSC story collection exercise, one of the lead farmers of Chisina 3(ward 25) acknowledged that since 2005 when CA was being promoted by Concern Worldwide, mulching was one of the major problems which negatively affected the adoption of the technology. On how to keep crop residue the lead farmer mentioned that it used to be problematic mainly due to free grazing. At village level together with traditional leaders they established binding by laws where there established controlled grazing system. In developing countries resource-poor farmers may fail to retain crop residue due to competing requirements for such biomass for fodder, fuel or building material (Giller et al., 2009). In attempting to resolve crop residue management problems, Magnan (2015) who studied property rights and CA practice in Morocco noted that Individual farmers may start to enforce property rights over crop residues to ensure either restricted grazing or retention as mulch, particularly when the shadow price of crop residues increases. This is an important consideration as shown by some farmers in Gokwe who successfully enacted by laws collectively with the local and traditional leaders at community level. Privatization of crop residues in previously open grazing systems has also been reported in Niger (LaRovere et al., 2005). Important factors in uencing pressure on crop residues are the land use ratio between rangeland/fallow and crop land (Mekasha et al., 2014) and system productivity (Valbuena et al., 2012). There is an associated evolutionary gradient of crop residue rights from open access through communal rights to private residue rights – with established property rights giving rise to the emergence of residue markets, including in situ stubble grazing contracts in Mexico (ibid) and ex situ hauling, trading and monetization in India (Blummel and Rao, 2006).


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Traditionally crop residues are considered to be community resources. Most of small scale farmers in Africa used to open the crop elds after grain harvest for the communities to let their animals graze on the crop residue. This is common under community free grazing system. Reserving more crop residue implies that residue are becoming a private resource of economic value. On the other hand feeding crop residue to livestock increases the availability of manure, which can contribute to maintaining and increasing crop yields. Feeding crop residue to draught power animals enable crop intensi cation particularly under mechanized CA. Establishing these linkages within individual households and through reciprocal arrangements within communities and eventually markets would support sustainable integrated crop-livestock systems. There is high potential of sustaining food security through the inclusion of fodder production in conservation agriculture farming system. Mupangwa and Thierfelder, (2013) revealed that forage crops can be successfully produced in conservation agriculture systems. There is high degree of complementarity and symbiotic relationships in mixed farming as livestock provide drought power and manure for crop production. Crop farming avails stock feeds for livestock and these linkages within a mixed farming system should be considered when promoting conservation agriculture. If these dynamics are not considered, attainment of sustainable food security through conservation farming will be problematic in a mixed farming system. During the survey, 10% of the interviewed conservation agriculture farmers in Gokwe South district of Zimbabwe faced problems on crop rotation which is one of the key principles of conservation agriculture. In the district, farmers normally rotate maize and cotton, legumes with the exception of groundnuts are not very popular in the district. Not all farmers were practising crop rotation in the district due to lack of knowledge and market. Farmers indicated that they consider legume production as a footnote of the main crop, maize and generally it is a women crop hence they are growing groundnuts on small scale for household consumption. The other problem which hinders crop rotation among farmers is accessibility of arable land especially for newly married young couples and youths who normally get a piece of land from parents. For instance a young household family may have 0.5 of a hectare which will be difficult for them to practise crop rotation. Conservation agriculture advocates for rotation of cereal and legumes mainly for nitrogen xation. Since newly married couples have limited arable land, rotation is difficult to implement in such cases. Moser and Barrett, (2003), concluded that 84


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poorer farmers with little land are much less able and less likely to adopt crop rotation than richer farmers with more land. Knowler and Bradshaw, (2007) argue that for conservation agriculture strategies to be successful they should be tailored to t local conditions and this observation is echoed by Erenstein (2002) who says that the success of the technology and soil conservation technologies depends on the local bio-physical and socio-economic environments. Interviews with key informants in the district revealed that most of the extension officers were not formally trained in conservation agriculture. About 50% of AGRITEX officers were trained in CA mainly through short training sessions sponsored by Food and Agriculture Organisation (FAO, 2008). Most farmers are failing to access accurate conservation agriculture management information at community level due to lack of well-trained extension service agents. This explains why adoption rates of conservation agriculture remain very low in the district. Nyanga (2012) who carried out conservation agriculture adoption analysis in Zambia concluded that effective trainings is one of the key factors which in uence uptake and ownership of the technology in a sustainable manner. According to Marongweet et al. (2011) government of Zimbabwe is in the process of institutionalizing conservation agriculture in agricultural colleges. Conservation agriculture promotion should go beyond institutionalization by strengthening accessibility of accurate conservation agriculture information at community level. This involves availing user-friendly extension materials to farmers and extension service providers (Marongwe, et al., 2011). In view of this, Wall (2007) argues that successful uptake of conservation agriculture depends on ''awareness raising'' in the community to the problems of soil degradation. Con icting statements on conservation agriculture among extension service also affects uptake. A notable example was the presence of conventional equipment such as tractor ploughs at DDF district offices. DDF promotes maximum tillage of the soil and this contradicts promotion of minimum tillage promoted under conservation agriculture farming system. A holistic approach in promoting the technology is required among development practitioners. Information collected from focus group discussions and key informant interviews showed that conservation agriculture was introduced by Non-Governmental Organisations (NGOs) in Gokwe South District. The NGOs that introduced the farming system also provided seed and fertilizers to farmers and as a result, conservation agriculture introduction in the district was input driven and this affected continuity of the practice at the end of project lifespan. Most humanitarian organisations like Concern Worldwide were targeting the extreme A Journal of Chinhoyi University of Technology

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poor in programming. In most cases poor households do not have the capacity to fully utilize agricultural resources as compared to better resourced families; hence conservation agriculture attractiveness was compromised. In some circles the technology was associated with the poverty or associated with poor people without good means of draught power. Given this negative perception by some farmers, there is need to adopt a development oriented approach and not a humanitarian approach in promotion of the technology. Giller (2009) concurs that conservation agriculture in Zimbabwe was introduced together with free agricultural inputs and blames this approach for distorting uptake and adoption rates of the technology. Giller (2009) further argues that conservation agriculture adoption rates claimed during the course of active promotion of technologies by NGOs and research later came about because of the temporary in uence of the project, rather than a sustained change in agricultural practice. For example, the apparent success of Sasakawa Global, (2000) in promoting conservation agriculture (Ito et al., 2007) appears largely to have been due to its promotion package that included fertilizers, pesticides and herbicides. When the project support stopped farmers quickly reverted to their former crop management practices. The widespread adoption of conservation agriculture that was claimed through promotion programmes like the one discussed above suffered the same fate in South Africa and in Zambia (Baudeon, 2007). In a detailed study of uptake of zerotillage practices in South Africa, Bolliger (2007) found patchy pockets of small numbers of farmers who embraced and practiced the technology, but little adoption of conservation agriculture across most of the areas he surveyed, despite earlier claims of remarkable success. Currently worldwide statistics according to Kassam(2009), South America has the largest area under conservation agriculture with 49,586,900 ha (46.6 per cent of total global area under conservation agriculture) followed by North America (39,981,000 ha, 37.5 per cent). Australia and New Zealand have 12,162,000 ha (11.4 per cent), Asia 2,630,000 ha (2.3 per cent), Europe 1,536,100 ha (1.4 per cent) and Africa 470,100 ha (0.4 per cent). Another factor that affected conservation agriculture adoption considered in Gokwe South is the way different organisations introduced and implemented the technology to the farmers they worked with. It was noted that, organisations introduced conservation agriculture in different ways since the focus of interest and emphasis varies from one organisation to the other. For example, ICRISAT mainly emphasized fertilizer micro-dozing and seemed not to emphasize 86


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mulching in their publications (Twomlow et al., 2008). Promotion of conservation agriculture by River of Life Church did not include labour saving technologies such as herbicides and farm implements as their focus was mainly on distribution of certi ed seed to farmers (Andersson and Giller, 2012). River of Life Church's approach to conservation agriculture is labour intensive and is against farmers needs in Gokwe South district where labour is one of the main challenges negatively affected adoption uptake. The answer to the high labour required to control weeds in the rst years of practising conservation agriculture by farmers is use of herbicides. One may however, wonder why herbicides usage is not part of the key principles of conservation agriculture given that weed control is often laborious and costly in the rst years. The debate on weed control is interesting as some proponents of conservation agriculture argue that good ground cover resulting from mulching or cover crops reduce weed pressure. Wall (2007) argues that apart from anecdotal reports there appears to be little published evidence to back this claim. Siziba (2008), argues that the increased amount of labour required to weed crops may outweigh the labour-saving gained by not ploughing, unless herbicides are used to control weeds. It appears there are too many unanswered questions about conservation agriculture labour needs and given this there might be need to carry out some research to determine conservation agriculture labour needs. The survey also revealed that availability and affordability of certi ed seed, fertiliser and herbicides in certain remote areas of the district hinders the promotion of conservation agriculture. Availability and non-availability of inputs is a marketing problem which may be either input or output market related. It is important to note that output and input markets in remote parts of Zimbabwe such as Gokwe are weak and offer low prices to the farmer and because of such problems farmers are not motivated to invest in conservation agriculture new farming systems and technologies. Given the situation discussed above, there might be need to do participatory environmental scanning to help farmers choose conservation agriculture components that best suit their needs and their operating environments. A nonhomogenous approach to conservation agriculture by different institutions may not seem problematic as it is good to allow institutions to work independently but it may be a good idea to have standard guidelines on how to introduce and implement conservation agriculture to different communities as this may help to check whether institutions are giving relevant technologies to farmers.


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RECOMMENDATIONS •

• •

•

•

•

Conservation agriculture should not be promoted as a package based on its three options, farmers should be free to choose what is ideal to them since its components are not universally applicable. Promotion of herbicides should be linked to market mechanisms for example affordability and accessibility at grassroots level. Labour saving mechanism like application of herbicides and mechanisation of conservation agriculture should be promoted to reduce high labour demand. However marketing concepts like accessibility and affordability of herbicides and conservation agriculture equipment should be considered in a sustainable manner. Fodder component should be part of conservation agriculture promotion especially in a mixed farming system so as to reduce usage competition of crop residue or trade-off between mulching and fodder. Conservation agriculture should be promoted in a developmental context, since in emergence situation farmers will be more interested in immediate solutions than long term bene ts like improved soil fertility, yields and reduced soil erosion in the long run. Conservation agriculture to be institutionalized in formal agricultural colleges and universities so as to ensure holistic promotion of the farming system. This needs to be backed up by supportive governmental policies which supports the technology for instance by availing certi ed seeds and input to all rural areas of the country.

CONCLUSION Large scale adoption of conservation agriculture is possible if key constraints being faced by farmers are curtailed. The problem of high labour requirements can be minimized by use of herbicides and mechanization of conservation agriculture equipment. Multi-usage of crop residue and trade-off between mulch and livestock feeds can be resolved through introduction of fodder component in mixed farming system. Although conservation agriculture has potential to address food shortage in developing countries the role of markets needs to be seriously considered to ensure sustainable food security. Although crop rotation is highly recommended with legumes for nitrogen xation, it is prudent to allow farmers to start the processing by using crops they are familiar with and marketable for instance cash crops like cotton. Legume can only be effectively promoted if new improved varieties which are not common to farmers are promoted as well as enhancing legume market.

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REFERENCES Anderson and Giller, K. 2012. On heretic and God's blanket sales Contested claims for Conservation Agriculture the politics of its promotion in Africa smallholder farming Blummel, M., Rao, P.P., 2006. Economic Value of Sorghum Stover Traded as Fodder for Urban and Peri-urban Dairy Production in Hyderabad, India. International Sorghum and Millets Newsletter, 47, 97-100. Baudeon, F., Mwanza, H, M., Triomphe, B. and Bwalya, M. 2007. Conservation agriculture in Zambia: a case study of Southern Province. Nairobi. African Conservation Tillage Network, Centre de Coopération Internationale deRecherche Agronomique pour le Développement, Food and Agriculture Organization of the United Nations Aune, J.B.,Nyanga, P.,Johnsen, F.H., 2012. A monitoring and evaluation report of the Conservation Agriculture Project 1(CAP1) in Zambia. Department of International Environment and Development Studies, Noragric, Norwegian University of life sciences Bolliger, A., 2007. Is Zero-till an appropriate agricultural alternative for disadvantaged smallholders of South Africa? A study of surrogate systems and strategies, smallholder sensitivities and soil glycoproteins. PhD Thesis. University of Copenhagen, Copenhagen, p. 67. Corsi, S., Friedrich, T., Kassam, A., Pisante, M. &Sà, J. d. M. 2012. Soil organic carbon accumulation and greenhouse gas emission reductions from conservation agriculture: a literature review. Food and Agriculture Organization of the United Nations (FAO). Derpsch, R., Friedrich, T., Kassam, A., &Hongwen, L. 2010. Current status of adoption of no-till farming in the world and some of its main bene ts. International Journal of Agricultural and Biological Engineering, 3(1), 1-25. Erenstein, O., 2002. Crop residue mulching in tropical and semi-tropical countries: an evaluation of residue availability and other technological implications. Soil Tillage Research, 67:115–133.


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"A Roadmap for Flue-curing Tobacco Barns: Towards Developing Improved Energy Efficient Barns for Small holder Farmers in Zimbabwe". 1

*Munanga, W., 2Kufazvinei, C. and 3Mugabe, F.T.

Tobacco Research Board of Zimbabwe, P.O. Box 1909 Harare, Zimbabwe. *Corresponding author: [email protected] 2

Department of Physics, School of Natural Sciences and Mathematics, Chinhoyi University of Technology, P. Bag 7724, Chinhoyi, Zimbabwe.

3

Directorate of Research and Resource Mobilisation, Chinhoyi University of Technology, P. Bag 7724, Chinhoyi, Zimbabwe.

ABSTRACT Tobacco crop currently provides the best economic return per hectare amongst all the major annual crops grown in Zimbabwe. Tobacco production currently contributes 30 % of the total exports and nearly 10 % of the GDP. According to the Tobacco Industry and Marketing Board, of the 106 127 number of registered tobacco growers, about 84 % belong to the smallholder category. The small holder section contributes more than 50 % of the total tobacco output. This article details the curing process and phases as well as the necessity of curing efficiency. An overview of the relationship between tobacco production and deforestation in Africa, and especially in Zimbabwe, is highlighted. A justi cation of the need for improved energy efficient ue-curing tobacco barns is presented. The article also reviews the different types of curing barns in Zimbabwe with particular attention to their development, operational systems, curing efficiencies, advantages and disadvantages. The main conclusion was that there is urgent need for improving energy efficiency in tobacco curing. In the short term, high fuel consumption can be reduced by optimizing the thermal efficiency of curing structures, particularly for smallholder tobacco growers in Zimbabwe. Key words: tobacco, ue-curing, smallholder farmers, energy efficient barns, heat transfer.

INTRODUCTION Most small scale tobacco growers in Zimbabwe rely on wood - fuelled old conventional barns because they are viewed to be inexpensive to construct, operate and maintain. However, these traditional barns are known to be inefficient with speci c wood to dried tobacco ratio of 14 kg: 1 respectively (Musoni et al., A Journal of Chinhoyi University of Technology

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2013). The 2013- 2014 tobacco season was characterised by lower tobacco prices, which experts say re ected the low quality of the tobacco due to the use of inefficient curing facilities. Efficient curing systems are required to minimize deforestation attributable to tobacco curing and to improve cured leaf quality particularly for small scale tobacco growers in Zimbabwe. High energy consumption in the conventional barns can be reduced through re-designing the furnace and heat exchange system (Musoni et al., 2013). Zimbabwe is currently the largest producer of ue-cured tobacco in Africa and the world's fth largest producer after China, Brazil, India and the United States of America (Food and Agricultural Organization (FAO), 2013). Zimbabwe grows some of the world's nest avour tobacco due to the favourable soil and rainfall conditions in the northern and eastern parts of the country which are particularly suitable for the Virginia type (Zimbabwe Tobacco Association (ZTA), 2014). The period from 2000-to 2008 in Zimbabwe was largely dominated by the land reform programme (Masvongo, 2013). Large-scale farms were sub-divided and land allocated to indigenous farmers. This rapidly increased the number of growers thereby increasing the potential tobacco production base. The number of growers has increased from 90 879 in 2013 to 106 127 in 2014 with about 84 % of the registered tobacco farmers belonging to the smallholder category (Tobacco Industry and Marketing Board (TIMB), 2014). In correspondence, tobacco cropped area also increased from 109 000 ha in 2013 to more than 115 553 ha in 2014 (ZTA, 2014). Tobacco provides the best economic return per hectare amongst all the major annual crops grown in Zimbabwe (Keyser, 2002). A survey conducted by Masvongo (2013) revealed that the average gross margin from smaller holder tobacco farming is USD $2 352 per hectare. This gross margin is attractive when compared to USD $1280 per hectare for maize and USD $620 per hectare for cotton. In addition, Keyser (2002) also noted that tobacco contributes signi cantly to the Gross Domestic Product (GDP) and to export revenue. For instance, in the year 2011, tobacco production accounted for more than 50 percent of agricultural exports and nearly 10 percent of GDP (FAO, 2013). Tobacco curing is an arti cial process that creates conducive conditions for the leaf to physiologically ripen (Bernard, 2000). Curing is an energy intensive process due to large amounts of moisture that must be removed from freshly harvested leaves (Nyer, 2008). About 80 % to 85 % of leaf moisture at harvesting must be removed to bring the leaf to approximately 0 % moisture content at the end of curing (Johnson, 94


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1985). Curing aims to achieve the correct chemical balance, a desirable colour and the actual drying of the leaf for proper storage (Mwandira, 2011). Heat is generated in a furnace or hot box and transferred through a heat exchanger. The air in the curing structure is heated under prescribed conditions of temperature, vapor pressure and humidity (Bernard, 2000). Curing changes starch and sugars to glucose by hydrolysis to produce carbon dioxide and water. The chemical composition of tobacco leaves varies during the various stages of curing (Figure 1). Colouring (35- 43°C), occurs at a relative humidity of 85 %. The colour of the tobacco leaf is xed by the chemical and enzymatic changes produced by the heat applied to the tobacco leaf. The second stage of curing is the lamina drying (40-57 °C) and lastly midrib (stem) drying which occurs at (57-75 °C) (Scott, 2009).

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Figure 1: The various stages of the curing process. Source: Sumner et al., (2009). Proper control of temperature and relative humidity are essential for efficient tobacco curing (Blake, 2014). Curing is carried out by various types of barns in which tobacco leaves are loaded in relatively compact masses in racks or clips and placed inside an enclosed curing barn (Johnson, 1985).


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Curing Phases Three phases which includes coloring, lamina drying and midrib drying are considered in tobacco curing (Blake, 2014). The coloring phase is a biological process in which the tobacco leaf stays alive until it reaches its best chemical balance (Reid, 2013). This is achieved by controlling the latent heat transferred to the plant cells which should be ranging from 51.4 to 102.8 Joules per leaf. While the leaf is alive, respiration continues within the leaf resulting in the colour changes of the leaf (Johnson, 1985). The coloring phase, takes an average of 48 hours depending on the maturity of the leaf (Bernard, 2000). The duration of the coloring phase is consistent for all types of barns (Sumner et al., 2006). This phase is characterized by reticulating a volume of 170 m of air per hectare of tobacco in an environment of 90 % humidity to avoid any premature wilting of the leaf (Bernard, 2000). After the colouring phase, the stomata cells are killed to prevent gaseous exchange between the leaf and air (Raju, 1989). This marks the beginning of the lamina drying stage. During this phase, the dry-bulb temperature is gradually increased and the relative humidity is reduced to prevent the leaf colour from progressing to undesirable brown colour (Nyer, 2008). During lamina drying, barn temperatures are increased at a rate of 3⁰C in every four hours with a pause at 50⁰C to ensure that the moisture in the atmosphere has a chance to clear (Bernard, 2000). If temperatures are moved too fast for the ventilation available, the humidity in the barn will rise sharply. The drying will be slowed and the tobacco will lose luster and turn brown (sponge) with a lot of black spots on it.The relative humidity is reduced by increasing ventilation while the dry bulb temperature improves from combusting more fuel (Siddiqui, 1990). Once the lamina drying of the leaf is complete, the dry bulb temperature is raised immediately to mark the last stagethe midrib drying phase (Raju, 1989). The mid rib drying is characterized by less than 65 % humidity and temperatures ranging from 57⁰C to 70⁰C (Bernard, 2000). Barn vents are then lowered to a quarter of their full size to allow for this rise in temperature. This limits the air ow while maintaining the temperature at approximately 70⁰C until the stem of every leaf is dry (Siddiqui, 1990). At the end of the curing process the moisture content of the tobacco leaves is near zero. In this state, the leaves are too brittle to handle, so adequate moisture must be added to the leaf to bring the moisture content up to about 20 percent (Michael, 2006). Siddiqui (1990) suggested adding 12 % to 15 % moisture back into the leaf to enable easy handling. The curing period varies with local conditions, position of leaves in curing barns, quality and ripeness of the tobacco leaves, one curing cycle lasts approximately 120–150 hours (Tobacco Research Board (TRB), 2012).

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The total time taken and amount of fuel used per curing cycle depends largely upon the efficiency of the curing barn (Musoni et al., 2013). Higher efficiency of the barn results in high quality tobacco, shorter period of the curing cycle and less fuel consumption (Rice, 2010).

Tobacco Production and deforestation The African Perspective In order to raise the dry-bulb temperature and remove moisture from the tobacco leaves in a curing barn, an energy source must be consumed (Boyette, 1999). Various sources of energy may be used to produce heat required to cure tobacco and these include wood, liquid petroleum gas, coal and agricultural wastes. According to the World Bank (1983), "developing countries will continue to use wood as a curing fuel because no cost-effective alternative has emerged”. Tobacco production in Africa has increased from approximately 250 000 - 500 000 tonnes in 2012 (ZTA, 2014). About 90 % of ue-cured tobacco production in the Southern African Developing Community (SADC) region is in countries such as Malawi, Tanzania and Zimbabwe (TIMB, 2012). Tobacco production accounts for 5 percent of Africa's total deforestation, 20 percent in Malawi and 12 percent in Southern Africa (Clay, 2003). Tobacco curing has accelerated the deforestation rate while exacerbating other environmental-related problems such as soil erosion, siltation, ooding and hydrology, reduced natural habitat for biodiversity and climate change (World Bank Report, 1983). Tobacco curing requires large quantities of fuel wood. Estimates are varied but small scale farmers consume approximately 43 m of fuel wood (15 000 kg per year) to produce an average of 1 400 kg of cured tobacco (Raju, 1989). This translates to a Speci c Fuel Consumption (SFC) of 10.7 kg/kg of cured tobacco. In contrast, estimates by Clay (2003) show that 19.9 m of wood is used to cure one metric tonne of tobacco. Geist (1999) suggests a value range between 9 and 37m of wood per tonne of tobacco cured translating to about 9.2 kg/kg of cured tobacco. In Kenya and Malawi the estimates are 8 kg/kg of tobacco respectively (Geist, 1999). Experimental research on wood fuel consumption for ue cured tobacco done in Tanzania (Siddiqui, 1990) showed that 14 kg of fuel wood is required to cure a kilogram of tobacco. Variations in wood resources consumption can be linked to a number of factors including the types and efficiency of barns used, moisture content and wood specie calori c value as well as the farmers knowledge on correct wood stoking practice (Manyanhaire, 2014).


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In view of the adverse environmental effects of conventional tobacco-curing practice, there is an urgent necessity to improve efficiency of the curing process. This can be done through the improvements in the barn structure, use of insulation materials, research on alternative fuel sources and improvements in the furnace and ue-pipe system designing. In addition, there is need for sufficient and effective emphasis on energy conservation and ecological consideration in tobacco-curing practice at national and regional levels.

The Zimbabwean Perspective Prior to the year 2000, ue cured tobacco production in Zimbabwe was largely dominated by large-scale commercial farmers whose majority used coal for curing tobacco (Manyanhaire, 2014). The post 2000 era has witnessed a sharp increase in the number of small scale tobacco growers (approximately 90 000 farmers) who bene tted from the land reform programme (TIMB, 2014). This movement of new farmers has been associated with the general clearance of land for various farming activities including tobacco production (Shumba, 2006). Thus, there is a link between the massive destruction of trees and the production of tobacco in newly resettled areas of Zimbabwe (Musoni et al., 2013). In Zimbabwe, most of the small scale growers rely on wood as their source of energy for curing tobacco (TRB, 2012). Tobacco curing is has evidently contributed to the deforestation in the country. For example, over 46 015 hectares of forests were harvested to provide 138 000 000 m of rewood that was used to cure part of the 127 000 000 kg of tobacco delivered to the auction oors during the 2010-2011 season (TIMB, 2014). In order to curb tobacco related deforestation in the country, several interventions have been pursuit. These include afforestation, use of coal, solar power and adoption of wood fuel saving barns like the rocket barn. Tobacco Wood Energy Act of 2012 which controls the movement and use of rewood for tobacco curing was also effected. With very low growth rates of Zimbabwean native woodlands averaging 0.8 m /ha/year; the rate of deforestation remains higher than the time required for woodlots to mature (Chapman, 1994). The use of coal requires electrical energy to drive combustion fans but the majority of small scale tobacco farmers are not connected to the electricity grid. Use of standby petroleum generators not only increases the cost of production, but these are also a source of noise pollution and re hazards. Additionally, there is a limited accessibility to coal as a result of its high cost coupled with poor railway transportation. This results in difficulties in the moving of coal from the mining areas to tobacco growing districts (Miller, 2010). The use of solar systems has been

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limited by the high initial cost and the need for efficient back up facilities (Scott, 2009). The 100 % solar curing trials done at Kutsaga failed to raise temperatures beyond 55⁰C (TRB, 2012). According to ZTA (2014) the rocket barn is currently the most energy-efficient wood- fuelled barn. However, with a curing efficiency of 4 kg to produce a kg of cured leaf, the rocket barn still uses a high amount of rewood (TRB, 2012). Tobacco growers require curing units that can handle at least 1 ha worthy of tobacco (TIMB, 2014). The initial cost to construct a rocket barn is also prohibitive to the majority of small scale tobacco growers ranging from USD 1100 to USD 1300 (TIMB, 2014). Such growers may view the rocket barn as a limitation despite its proven wood fuel efficiency. There is therefore, need to further reduce wood fuel consumption in conventional barns whilst addressing cost and capacity challenges.

Necessity for curing efficiency Curing efficiency can be quanti ed as mass of cured leaf per unit of fuel consumed (Rapier, 2013). Individuals and tobacco producing companies often spend more time and effort on improving agronomic aspects while overlooking curing losses (Isaacs and Mundy, 1990); (TIMB, 2014). Good and efficient curing is highly cost effective. The bene ts go far beyond the value of the fuel saved, because both the weight and the quality of the tobacco are increased (Sumner et al., 2006). The rst consideration in barn design was always towards minimizing the capital cost, which was understandable when fuel was plentiful, operating costs low and pro ts high (Bernard, 2000). Tobacco barns used by the newly resettled farmers in Zimbabwe are known for being inefficient (Musoni et al., 2013). The inefficiencies of the traditional barns are resulting in long curing time (9 - 12 days) which causes high fuel consumption and shortage of curing space as a result of continuous ripening of tobacco leaves in the elds (TIMB, 2014). It is also necessary to conserve fuel by employing the most energy efficient curing structures and heating equipment, balancing barn capacity with its capability to cure efficiently (Blake, 2014). Due to the high inefficiencies cited above, it is clear that there is need to develop energy - efficient low cost tobacco curing barns.

Types of Flue – Curing Tobacco barns in Zimbabwe The different barn types depend on several factors. Some re ect the traditions of the people who built them while some, like the New England connected barn, stem from regional or local building traditions (Miller, 2010). Others, like the plastic barn, re ect the availability of local building materials because its superstructure is


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made out of plastic. The scienti c principle of operation or the physics behind the barn can also in uence the barn name and type. A cascade is a series in which one component over ows into the next and hence the cascade barn which consists of a single heat source from which hot air is directed into a series of curing rooms (Bernard, 2000). Other historic barns like the Billy and Taylor barn were built to patterns developed and popularized by their designers (Siddiqui, 1990). Some barns were named from specialized advantages such as increased packing curing capacity such as the, “bulk curers” (Bernard, 2000). The choice of a particular barn type depends on several factors such as the need for improved curing efficiency, affordability, labour availability, fuel type, cost and desired curing capacity (Walton et al., 1993).

Conventional up draft barn According to Bernard (2000), the conventional up draft barn operates using natural convection where the air is forced to rise through the tobacco by the heat from the ues (Figure 2). The heated air reaches the top of the barn displacing the cold air at the top which then begins to move downwards towards the ue pipes to be heated again and the process continues (Mc-Quiston et al., 2005). The inlet (bottom) vents are ducted under the ue pipes so that air enters the barn and picks the heat from the hot pipes to the top of the barn where the top exhaust vents are found. This barn mostly uses wood as the curing fuel though coal can also be used. The conventional updraft barn is commonly used in Southern African countries because it is easy to construct, maintain and is considered to be the least expensive (Incropera and DeWitt, 2002). The major disadvantage of this barn type is that it relies on natural convective draft for air circulation which results in non-uniform curing (Bernard, 2000). In order to address some of these shortcomings, previous researchers, modi ed and tted a re-circulation fan (Bernard, 2000). A vertical duct is tted from the bottom tier to the top tier and a fan is tted at the bottom of the duct. The fan blows downwards so that the air is drawn from the top of the barn and distributed across the oor to be heated again. This encourages even wilting from top to bottom, minimizing channeling and ensuring fast drying (Boyette and Ellington, 1999). The barn has a maximum curing capacity of 2.5 ha of tobacco with an energy efficiency of ±9 kg of wood to produce a kg of cured tobacco (FAO, 2013). It is common practice that the furnace for this barn is outside the barn resulting in high heat losses to the surrounding. This barn can be improved by modifying the furnace system so that the furnace protrudes inside the barn to reduce heat losses.

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exhaust air exhaust air vent

heated air

ceiling supporting vertical strings of tobacco chimney draught damper

ambient air in wood fired furnace

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Figure 2: Principle of operation of conventional updraft barn (Bernard, 2000)

Down draft traditional barn In this barn, the heat is introduced to cure the tobacco leaf from the top vent which is directly linked to the heat exchanger system (Figure 3). The advantage of this barn is that the curing air is introduced from the top of the barn (Johnson, 1985). As the hot air descends down, it becomes denser and therefore is likely to move faster aided by its own weight (Boyette and Ellington, 1999). There are also limited chances of barn res from leaking heat exchangers because the heat system is isolated from the curing room (Bernard, 2000). However, this barn requires an airtight and insulated ceiling to prevent heat losses through the roof top (Oke, 2003). There is very little residence time of hot air as the conduit length and heat transfer area are both too small to allow high heat transfer to the drying chamber (Mc-Quiston et al., 2005). This leads to the exhaustion of hot air from the chimney to the atmosphere with unused energy and the laminar ow of hot air in conduits leads to low dissipation of heat energy from the conduit air (Michel, 2006). This barn is has less ue pipe maintenance costs because the barn loaders do not interfere with the ue system throughout the curing period (FAO, 2013).


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The barn relies on rewood as the curing fuel. The use of coal in this barn requires combustion fans rendering the barn more expensive and less favourable. In order to conserve heat within the barn, previous researchers recommended the inclusion of extraction fans to draw hot air from the top allowing it to pass through the leaves extracting moisture. The air is moved from the barn upwards through the heat exchanger system where it picks hot air again and repeats the cycle. A proportion of the air is exhausted and an equal amount of fresh air is drawn in. Usually the barn has 6 tiers upwards by 10 tiers across and it can cure up to 3, 5 ha depending on the size of the tobacco leaf (Bernard, 2000). The energy efficiency of the barn is ±2.5 kg of coal cobbles to produce a kg of cured tobacco (TRB, 2012). This barn can be improved by reducing barn volume whilst maintaining the existing heat transfer area as well as appropriate design of the barn ceiling to promote air movement inside the curing room.

chimney

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Figure 3: Principle of operation of a conventional down- draft barn. (Source: Bernard, 2000)

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Bulk curers In principle, hot air is forced by a fan through the hot box and into the bulk curer barn where it subsequently rises over the tobacco leaves compacted on racks (Mashonjowa, 2010). As the hot air rises, it evaporates moisture from the leaves before it is recycled into the heat exchanger (Figure 4) (Mc-Quiston et al., 2005). Bulk curing barns have been designed for easy regulation of temperatures and to handle large quantities of tobacco per given cycle (Hestian Rural Innovation Development (HRID), 2009). Despite this advantage, bulk curers are not feasible for small-holder farmers because they are expensive to acquire (Bernard, 2000). In addition, bulk curer barns are difficult to retro t on existing commercial barns and therefore are either bought or have to be newly constructed in situ (Michel, 2006).The heating system also has a large fan power requirement, in the order of 5.5 kW to 7.5 kW for a large barn (BulkTobac, 2003). This barn is mainly used by large scale commercial growers in Zimbabwe and is also most common in the United States of America (USA) because of labour challenges as the loading of tobacco leaves in the barn can be easily mechanized (Macialek, 2006). Bulk curers are fuelled by a variety of fuels from LP Gas to wood (HRID, 2009). The barn can cure 1 to 3 ha depending on the size of the leaf (BulkTobac, 2003). The energy efficiency of the barn is ±1.5 kg of coal nuts to produce a kg of cured tobacco (Bernard, 2000).

heat exchanger

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Figure 4: Principle of operation of a bulk curer (Source: Bernard, 2000)

Plastic barn The barn was designed for beginners and low income small scale tobacco growers (Isaacs and Mundy, 1990). It is a 4 m × 4 m × 4.5 m structure with a curing capacity of


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0.5 ha of tobacco leaf. Temperatures of 70 ˚C are achievable and a turnaround time of 6-7 days can be attained (TRB, 2012). A plastic barn requires about 2000 farm bricks, 37 tree poles (105 – 125 mm thick) and 80 m2 of 250 μm black polythene plastic to construct. Usually the barn has 3 tiers up by 5 tiers wide. The major disadvantage of this barn is that of low curing capacity (0.5 ha) for most small scale growers who grow the tobacco crop on 2 – 3 hectares (TIMB, 2012). The energy efficiency of the barn is ± 4.5 kg of wood to produce a kg of cured tobacco (TRB, 2012). The plastic barn can be improved by incorporating insulation because as the black plastic gets hot at higher temperatures, the radiation losses to the surrounding also increases. There is also need to use more durable plastics to reduce seasonal barn repairs expenses as the plastic is easily exposed to all forms of damage. Nanomaterials research with technology innovation can greatly enhance the efficiency of this barn type. Flexible, durable and suitable plastics or equivalents can be used such that solar cells are integrated into them. The solar energy can become the primary source of heat or can be the supplementary source and heat exchanger system can be used if temperatures inside become too high.

Figure 5: Plastic barn (Source: T.R.B, 2012)

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The rocket barn The rocket barn is a structure which was developed in Malawi in 2006 to arrest the inefficient use of rewood in tobacco curing (HRID, 2009). The design of the rocket barn is such that an increase in barn temperatures also increases the air sucking effect through the double exhaust chimney. On entering the barn, the temperature of the ambient air is quickly heated up by the furnace wall making it less dense and enabling it to move at a faster rate, extracting moisture from the leaves before exhausting it to the atmosphere through the large diameter chimney (Scott, 2009). In the rocket barn, ambient air enters into the barn and ows through a brick furnace ( label 26, Figure 6).The hot ue gases ow inside the heat exchanger, made from thin steel metal (label 30, Figure 6) and a brick rebox. From the brick heat exchange rebox, the hot gases enter the metal inner chimney (label 28, Figure 6 & 38, Figure 7). The hot gases exit the inner metal chimney (label 42, Figure 7) and into the outer metal chimney (label 36, Figure 7) thus heating the air inside the outer metal chimney and creating a pressure drop. The pressure drop in the outer metal chimney generates a suction, drawing air through the vents on the front wall (label 24, Figure 6), across the leaves in the inner barn space, through the window in the back wall of the barn (label 32, Figure 6 and Figure 7) and out of the metal outer chimney.

Figure 6: Principle of operation of a rocket barn (Scott, 2009)


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Figure 7: Double Chimney of Rocket Barn (Scott, 2009) The rocket barn has been adopted as an energy efficient smallholder barn in many African countries such as in Malawi, Zimbabwe, Zambia, Tanzania, Kenya, Uganda, Bangladesh and Madagascar (Geist, 1999). The major advantage of the rocket barn is that the increased air ow over the leaves increases convectional heat transfer and the drying capacity of the barn yielding higher efficiencies (Scott, 2009). The heat exchanger is elongated to increase the surface area of heat transfer (30, Figure 6). Insulation is also added in the form of grass ceiling, which research has suggested can increase the barn's efficiency index by 30 % (Scott, 2009). However, tobacco growers already using the rocket barns are facing problems of limited capacity and high initial cost (TRB, 2012). In order to attain sufficient curing space; a farmer needs to construct numerous rocket barns. This result in high costs of building materials, time consuming in construction; and the complexity faced in the management of numerous barns to the small scale farmer who has limited manpower (TIMB, 2014). Some farmers make rocket barn extensions to suite their requirements without considering important curing factors such as temperature, air ow and humidity (Munanga et al., 2014). Farmers are ending up converting their kitchens to tobacco curing barns (Figure 8). In most cases this is done without considering the major factors of barn designs such as choice of materials, structural strength and insulation that increase the efficiency and quality of their tobacco resulting in them remaining poor (Masvongo et al., 2012). The rocket barn can be improved by research on controlling air ow inside the barn, possibilities of hot air recirculation to provide preheated air in the furnace. The tobacco carrying capacity also needs improvement for the same curing efficiency.

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Figure 8: Modi ed kitchen in Rural Community of Mrewa, Mash East Zimbabwe (Source: Author, 2013)

Billy barn A Billy barn is tted with a re-circulation fan (Goodman, 1995). A vertical duct is tted from the bottom tier to the top or second from the top tier and a fan is tted at the bottom of the duct (Figure 8). The fan blows air downwards so that air is drawn from the top of the barn and distributed across the oor, to be heated again (Figure 8) (Incropera, and DeWitt 2002). The fan encourages even wilting of tobacco from top to bottom tier, minimizes channeling and ensures fast drying (Boyette and Ellington, 1999). The top vent is closed and completely sealed at all times when the fan is in operation. Any leakage will draw cold air into the barn, at the expense of the warm air ow through the tobacco (Incropera and DeWitt, 2002). However, the barn requires electricity for efficient operation which limits their adoption rate (TIMB, 2014). According to Bernard (2000), the barn can have 7 tiers upwards by 5 tiers across and curing capacity of 1 ha ± 0.5 ha, with a barn energy efficiency of ± 2 kg of coal to produce a kg of cured tobacco, or wood consumption of 7 kg / kg of cured leaf. This barn can be improved by adopting solar powered fans to enhance adoption by most small scale growers.


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Figure 9: Schematic diagram of a Billy barn (Bernard, 2000)

Continuous tunnel curing systems The principle of operation of continuous tunnel curing systems involves hot air circulation from a single heat source (Bernard, 2000). As the hot air passes through the tobacco it evaporates moisture whilst cooling and becoming more humid as it progresses, which establishes suitable temperature and humidity gradients. The major advantage of the tunnels is that the curing air is only discarded when it is almost saturated with moisture (Boyette and Ellington, 1999). By comparison, in some curing system, typically the conventional barn, bulk barn and rocket barns, hot dry air has to be relatively discarded for much of the time. However in tunnel systems, exhaust air is used to condition the dried tobacco and partly re-circulated to control the wet bulb temperature. Continuous curing systems are the most efficient with regard to both fuel and electricity (Bernard, 2000). A tunnel system minimizes tobacco leaf handling losses because tobacco is wheeled on trolleys into the barn (Figure 10b). When fully understood they are simple to operate but require some care because any bottleneck in the curing process disrupts the entire output. They need a well-organized infrastructure from the tobacco handling aspect to ensure continuity through the whole system from reaping to untying (ZTA, 2014). In particular, regular loading with uniform amounts of tobacco will ensure minimum control problems. These barns are the most expensive to acquire and are mostly used by large scale developed growers (TRB, 2012). The cost makes them unattractive to the bulk of the tobacco growers who are mainly small scale low income growers. The barn can cure up to 120 ha of

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tobacco and the energy efficiency of the barn is ±0.9 kg of coal nuts to produce a kg of cured tobacco (TRB, 2012). The tunnels can be improved by redesigning for low cost material and research on efficient and affordable heat exchange systems.

Figure 10: Tunnel barn (T.R.B, 2014)

Cascade System A cascade system consists of barns connected in series and supplied by a single heat source (Figure 11), (Bernard, 2000). Separate hot air ducts are connected to any one of the barns (compartment) that is at mid rib drying stage. The hot air is passed through each barn in turn before being exhausted from the coldest coloring barn (Scott, 2009). Every 24 hours the inlet hot air is diverted to the next barn. The rst is cooled, conditioned, offloaded, re lled and reconnected to the air ow at the end of the series to become the last one in line. These barns are energy efficient due to the use of a single heat source to cure a series of barns and by incorporation air recirculation mechanism, the curing air is discarded when it is almost saturated with moisture unlike in the conventional barns (Bernard, 2000). However according to the same author, the cascade system requires uniform tobacco and any bottleneck in the system will have negative consequences and therefore require good agronomic standards from the eld. This can be a challenge to small scale growers who in most situations, rely on rain fed crop which is often non-uniform (TRB, 2012). The system is also expensive to set up as it usually requires radiators, automatic feeding stockers, hot water boilers (ZTA, 2014). A standby power source is required to avoid major down time and just like the tunnel system, the cascade barns can be improved by research on low costefficient heat exchange systems and possibility of using solar power fans.


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heat exchanger 70oC

ambient air in

exhaust air o +30 C

vents closed

hot air vent

Figure 11: The principle of cascading (Bernard, 2000)

Proposed Work It is apparent that investigation into effective curing systems to reduce energy consumption in tobacco-curing practice for small scale farmers is urgently needed. High fuel consumption could be reduced through improvement of the technology associated with barn construction. Factors such as the size and shape of the barn as well as the furnace type and con guration of the ue pipe, could be investigated. Barn design in general has to put a high priority on thermal efficiency which could result in fuel saving. The cost and durability of materials should also be considered. Heat transfer principles need to be reviewed in order to improve heat generation, transfer and use in tobacco curing. The fundamental heat transfer mechanisms include conduction, convection, thermal radiation and phase-change transfer. To increase heat transfer through conduction; more designs are necessary that incorporate a variety of other heat transfer modes like convection and phase change. The convectional distribution of heat through convective currents is essential in ensuring that heated moist air reaches the tightly packed tobacco leaves at the top of the barn. The air heated by hot ues is forced to rise through tobacco by natural convection, hence displacing the cold dense air at the top. The displacement is in downward motion towards the ue pipes where it will be heated again and thus continuing the process to ensure constant delivery of heat to the top parts of the barn through convective heat transfer. Provision of intake air vents over to the heating surfaces in barns increases outside pressure gradient

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and promotes heat transfer through convection. The radiant frequency or intensity of the electromagnetic waves is a directional quantity of radiant power per unit direction and surface area of the emitting surface. This can be utilized in barns by increasing the length and surface area of the ue pipes to ensure greater heat transfer through radiation. Much can be done towards improving the design of barns using the heat transfer mechanisms at little cost. Heat for curing is generated in a furnace and in order to ensure efficient heat generation, an efficient furnace is desirable. The furnace system must be able to promote complete combustion and should create the necessary turbulence for proper mixing of gases. In order to make use of heat radiated from the furnace, it is important to build the furnace inside the curing room. A slot furnace is also important in ensuring that the air for combustion is at a reasonable velocity for high temperature forge effect. Once the heat is generated in the furnace, it is then transferred into the curing room and the heat exchange system has to be efficient. The most common heat exchange systems are metal ue pipes. Due to their high thermal conductivity, heat transfer by radiation has a tendency of rapidly increasing leaf temperature which may scorch the leaf and is not desirable. In addition, any leakages along the ue pipes have potential to drastically reduce chimney draught which is necessary for drawing the hot gases out of the barn. If the furnace and heat exchange system is inefficient, there is likely to be more fouling of the inside surfaces by ash deposits, carbon particles and tar, thereby increasing the hot gas to heat exchanger surface convective resistance, leading to lower heat transfer from the gas to the heat exchanger surface. Tobacco curing is a chemical process that requires stable temperatures for the desired leaf colour. It is therefore important to have a heat exchange system that produces more stable temperature pro les and that have small day-night cyclic variations. The common ue pipe heat exchange system is very sensitive to both low and high temperatures by the good absorber- good emitter principle. In order to allow more heat transfer by conduction, it is important to ensure there is enough residence time of the hot gases inside the barn. In most conventional barns, the ue pipes are arranged in a traditional U con guration and there is no adequate residence time to maximize heat transfer. The ue pipes have got plain surfaces and the use of ns could possibly increase the conductive area for better heat exchange.


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CONCLUSION There has been a marked shift in the tobacco grower base from large scale to small scale growers in Zimbabwe. Most small scale tobacco growers use conventional, inefficient wood- red barns and the use of wood in these inefficient barns has accelerated the deforestation rate in the country. In view of the negative environmental effects of existing tobacco curing practice, there is an urgent need to reduce fuel consumption by improvements in the furnace and heat exchange system as well as seeking alternative sources of energy. In this connection, solar energy can also play a supplementary role. However, there is need to investigate cheaper, yet effective, methods of solar energy use for tobacco curing. Nanomaterials and nanotechnology can play a very important role for the solar energy aspect. For instance, efficient solar cells can be developed and integrated into barn roofs to provide pre-heated air in the curing room. Regardless of fuel type, high fuel consumption remains a major cost to growers and the development of efficient curing structures is an important baseline. Technology innovation is vital for this aspect. Modeling and simulation can also be included to produce highly efficient and cost effective ue curing tobacco barns. There are a lot of projects underway globally testing new techniques and several types of heat sources. Hopefully, these will provide new and innovative curing methods that can deliver further bene ts to tobacco farmers, our tobacco industry and the environment in a sustainable way.

RECOMMENDATIONS There is need to support the growth of the tobacco industry in an efficient and sustainable manner. Curing is the bottleneck through which all tobacco passes through and there is need to improve efficiency for the small scale grower in order to reduce yield losses and improve income from tobacco production. The most common conventional barns are very inefficient and there is need to optimize thermal efficiency of these structures. Optimization of heat transfer has an overall impact on barn design, turnaround time, fuel use efficiency, weight and quality of cured leaf and the market price.

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List of Abbreviations AGRITEX

–

Agricultural Technical and Extension Services Department

BAT

-

British American Tobacco

FAO

-

Food and Agricultural Organisation

GDP

-

Gross Domestic Product

ITGA

-

International Tobacco Growers Association

HRID

-

Hestian Rural Innovation Development

SADC

-

Southern African Development Community

SFC

-

Speci c Fuel Consumption

TIMB

-

Tobacco Industry and Marketing Board, Zimbabwe

TRB

-

Tobacco Research Board

USA

-

United States of America

USD

-

United States Dollar

ZTA

-

Zimbabwe Tobacco Association


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ACKNOWLEDGEMENTS We are grateful to Dr. S. Dimbi, Assistant General Manager, Research and Extension at the Tobacco Research Board for her encouragement throughout the preparation of this manuscript.

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Johnson, W. 1985. Energy Efficient Curing and Drying System, Patent paper no. US 4499911A. Keyser J.C. 2002. World Bank Discussion Paper. The Costs and Pro tability of Tobacco Compared to Other Crops in Zimbabwe. Economics of Tobacco Control Paper No 1. Macialek, J.A. 2006. Reduction of Flue -Cured Tobacco Production Cost Utilizing a Hot Water System. Manyanhaire, I.O. and Kurangwa, W. 2014. Estimation of the Impact of Tobacco Curing on Wood Resources in Zimbabwe. International Journal of Development and Sustainability, 3(7): 1455-1467. Mashonjowa, E. 2010. Modelling Heat and Mass Transfer In Greenhouses: An Aid to Greenhouse Design and Climate Control for Greenhouse Rose Production in Zimbabwe. PhD Thesis, Ghent University. Belgium. pp 292. Masvongo, J., Mutambara, J. and Zvinavashe, A. 2013. Viability of tobacco production under smallholder farming sector in M ount Darwin District, Zimbabwe. Journal of Development and Agricultural Economics, 5(8):295-301 Mc-Quiston, Parker and Spitler. 2005. Heating, Ventilation and Air Conditioning: Analysis and Design, 6th Edition. Hoboken NJ: John Wiley and Sons Inc. pp.261. Michel, A. 2006. Rocket Barn Development in Malawi. GTZ – Probec, Malawi. Miller H, (2010), The Lure of Sot Weed: Tobacco and Maryland History. Zimbabwe. Munanga, W. Kufazvinei, C, Mugabe, F.T. and Svotwa, E. 2014. Evaluation of the curring efficiency of the Rocket Ban in Zimbabwe. International Journal of Agriculture Innovations and Research. 3 (2): 2319-1473. Musoni, S., Nazare, R., Manzungu, E. and Chekenya, B. 2013. Redesign of Commonly Used Tobacco Curing Barns in Zimbabwe for Increased Energy Efficiency, International Journal of Engineering Science and Technology, 5(3): 609-617. Mwandira, C. 2011. Energy Efficiency In Tobacco Curing, Malawi Tobacco Research Authority. P.O Box 418, Lilongwe. Nyer, E. 2008. The Use of Biomass in High Efficiency Tobacco Curing for Small Holder Farmers in Bangladesh. Department of Civil, Environmental & Architectural Engineering. University of Colorado, pp 11-48.


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Raju, N. 1989. An Energy Efficient Drying Chamber for FCV Tobacco Curing Process. Solar and Wind Technology, 6(2):159-163. Rapier, R. 2013. Energy Trends Insider: The Key to Running the World on Solar and Wind Power. Reid, L. 2013. Manual for Australian Agriculture. Elsevier Publishing, Australia. Rice E. 2010. New Tobacco Curing Method Traps the Sun's Power. Scott P, 2007. Biomass Energy Consultant: Insights into Fuel Efficiency and the Dissemination of Mud and Ceramic Stoves in Southern Africa. Scott, P. 2009. Natural Draft Curing Systems. Alliance One and Phillip Morris International. Siddiqui, K.M. 1990. Analysis of a Malakisi Barn Used for Tobacco Curing in East and Southern Africa. Shumba, E.M. and Whingwiri, E.E. 2006. Commercialisation of Smallholder agriculture. In: Rukuni M, Tawonezvi P, Eicher C .Zimbabwe's agricultural revolution revisited. University of Zimbabwe Publications, Harare. pp. 577-593. Sumner, P. Moore, J. and Boyette, M. 2006. Retro tting Tobacco Curing Barns. College of Agricultural and Environmental Sciences, Biological & Agricultural Engineering Publications. University of Georgia. Accessed on 05/06/2014. Tobacco Industries Marketing Board. 2012. T.I.M.B Annual Statistical Report. Harare, Zimbabwe. Tobacco Industries Marketing Board. 2014. T.I.M.B Annual Statistical Report. Harare, Zimbabwe. Tobacco Research Board. 2012. Flue Cured Tobacco Recommendations. TRB, Harare, Zimbabwe. Walton, L. Casada, J. Swetnam, L. and Duncan, G.A. 1993. A Field Curing Structure and Mechanized Housing System for Burley Tobacco. Applied Engineering in Agric, ASAE Vol. 9. No. 1. World Bank Report. 1983. Technical Assistance Package to improve the efficiency of Wood Fuel Use in the Tobacco Industry. Zimbabwe Tobacco Association: History of Flue Cured Tobacco in Zimbabwe, accessed from www.fctobacco.com/index.php/about/history-of-tobacco on 05/11/14. 116


ZJTS Guidelines for authors 1. 1 Editorial Policy The editorial policy of the Zimbabwe Journal of Technological Sciences (ZJTS) is to review and publish peer-reviewed, high quality and original research articles, reviews and short communications in any area of technological sciences. The editorial board welcomes articles that contribute to the creation of knowledge in science and its application in solving problems faced by society through innovation and technology development. The journal has a broad disciplinary focus in science and technology and its coverage encompass, but is not limited to; physics, chemistry, biology, medicine, ecology, environmental sciences, geology, engineering, agriculture, biotechnology, nanotechnology, arts, education, sociology and psychology, business and economics, nance, mathematics and statistics, computer science, social sciences, linguistics, architecture, industrial and all other science and engineering disciplines. The journal produces two issues per year, the rst issue dedicated to sciences, mathematics, engineering and technology and the second issue dedicated to education, linguistics and sociology, psychology, business and nance sciences and technology. Papers can be submitted throughout the year but the two issues of the journal will be published every year in August.

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