UTILIZATION OF SOLID WASTE FROM PAPER INDUSTRY: BANGLADESH PERSPECTIVE Sudipto Chakraborty1, Taif Mahmud1, Md. Moinul Islam2 and Md. Saiful Islam2 1
Undergraduate Student, 2Professor, Department of Civil Engineering, CUET, Chittagong-4349, Bangladesh.
ABSTRACT Paper industry is one of the growing fields in industrial sector all over the world. Waste generation from paper mills is an unavoidable issue. Solid waste known as hypo-sludge produced during the process of coating paper is an issue to be focused on. It is a material generally white in color, found as effluent of Hypo plant. It needs to be disposed without causing health and environmental hazards. But hypo-sludge issue is not pronounced so prominently along with waste-water crisis of paper industry. Hypo-sludge needs large land space to be disposed, create problems for cultivable lands and also fills up the bed of the rivers if discharged into rivers directly. Hence, hypo sludge, solid waste of paper industry, needs to be well managed. In this paper, ill-effects of hypo sludge as waste material and the possible ways of utilization of hypo sludge in engineering construction has been discussed.
INTRODUCTION
The paper industry in Bangladesh went into operation when Karnaphuli Paper Mill (KPM) was established by DAUD group at Chandraghona in Chittagong in 1953 (Saha et. al.,1997).Three more paper mills were established by the government : Khulna Newsprint Mill(KNM),North Bengal Paper Mill(NBPM) and Sylhet Pulp And Paper Mill(SPPM).Among them, only KPM is now in operating condition and currently producing 30,000 tonnes of paper per annum(www.bcic.gov.bd/kmp.php). Afterwards private sectors were also raised in for paper production. In the mid90s, private companies started to take part in this sector due to loss in state owned mills for shortage of raw materials and other problems. Currently it is seen that there are about 55 paper and board mills in our country which produce approximately 550,000 tonnes of paper and board per annum (Haroon, 2010) These paper mills depend upon imported pulp and waste papers. Table 1 shows current varieties of raw material usage in Bangladeshi paper mills (Haroon, 2010).Local paper mills now meet over 60pc of demand: Stakeholders are planning for increased investment.Based on environmental impact effect, Bangladesh government has included paper and board mills in the “red category”(Environmental Conservation Rule 1997, Schedule 1, Ministry of Environment and Forest, Government of People’s Republic of Bangladesh, 1997). Across the world, sustainability is a major issue now-a-days. Unsustainable trends in waste generation of Mills can be regarded as a symptom of environmentally inefficient use of resources(OECD 2011).Transforming such waste otherwise unusable products may mitigate but not solve present and environmental challenges (Naik and Kraus 2000). About 6 kg of sludge is produced per ton of paper produced (Fava et al.,2011). From this, it can be summed up the total production of hypo-sludge (550,000*6)=3,300,000 kg per year in our country. Different studies are going on to use this hypo-sludge as supplementary cementitious materials. Experiments show that when paper mill sludge ash was used to replace up to 10% of the Portland cement; positive results were obtained on the mechanical performance of mortars(Fava et al.,2011).Again it is assumed that to produce 4 million tons of cement,1 million ton green house gases are emitted. So it is encouraged to find an alternative for OPC although could be a small extent. In the context of low availability of renewable energy resources coupled with the
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requirements of large quantities of energy for building materials, the importance of using industrial waste cannot be under estimated.
Table 1 : Raw materials used in bangladeshi paper mills Type of raw materials
Source
Waste paper
Local
Waste paper
Foreign
Pulp
Local (only in KPM) and Imported
Share 45% 25% 30%
DISPOSAL OF HYPO-SLUDGE Hollingsworth (1989) described an innovative approach where primary sludge, biological sludge, and polymers were mixed and matched to the vacuum filter, belt press, and screw press to achieve optimum production, dryness, and overall efficiency. Slagel (1989) discussed critical problems and equipment changes made to meet performance guarantees for a sludge screw press system. A collection of papers assembled by NCASI discussed paper industry sludge disposal practices in the U. S. and the NCASI [Experience with and Laboratory Studies of the Use of Pulp and Paper Mill Solid Wastes in Landfill Cover Systems." NCASI Tech. Bulletin No. 559 (1989)] investigated the use of sludge and fly ash as landfill cover materials. Fifteen sludge (both combined and primary) and eight fly ashes were characterized chemically and physically with hydraulic conductivity being the chief parameter of interest. The sludge had hydraulic conductivities of 10-4 to 10-8 cm/s. Combined sludge (80% secondary and 20% primary) was mixed with 2%Industrial Wastes and 9.5% ash and slopes 5:1, 6:1, and 7:1 (H:V) were considered. Haas et al., (1989) reported on the use of paper mill sludge as binders for iron ore concentrate. Five sludge samples were evaluated in laboratory testing as a substitute for bentonite clay. Sludge showed potential to be a cost-effective binder additive. Maher et al., 1989 presented one landfill case history in which an upward seepage gradient protected the groundwater from contamination. The landfill was unlined yet hydrogeologically secure. Another case history (Griffith et al., 1989) presented special design considerations where a site did not have all the desired locational anddesign features specified in state solid waste management regulations. Valitchka (1989) discussed experiences in development, operation, and maintenance of a state-of-the-art landfill. Grefe (1989) noted that in closure of paper mill sludge lagoons, paper mill sludge impose limitations on the use of conventional materials and construction methods due to their high moisture content, organic matter content, potential for leachate and gas production, and low shear strength or bearing capacity. A 2.5:1 mixed primary/secondary paper industrysludge was applied to a red pine plantation and leaching of inorganic nitrogen was examined by Bockheim et al.,1988.Applications of 32 Mg/ha (550 kg N/ha) did not contaminate groundwater at depths greater than or equal to 1.6 m. Higher application rates could be made without exceeding the 10 mg/L nitrate standard at depths greater than or equal to 5.2 m. Shimek et al.,(1988) reported on a greenhouse sludge land application study, field demonstration plots, and a nitrogen mineralization/computer simulation study conducted for mills representing three different papermaking and treatment processes. Typical municipal sludgemineralization rates of 15% to 20% could not be used for determining papermill sludge loading rates. Estimated first year nitrogen mineralization rates at two sites were higher and lower than the typical municipal sludge rates. Krouskop and Ayers (1989) discussed the technical, regulatory, and public issues concerning dioxin in the use of bleached kraft sludge for abandoned strip mine reclamation. They presented a case history and noted the importance of risk communication. Lawrence et al., (1989) discussed the assessment of abandoned strip mines. The acceptable risk level, the cancer potency factor, and the exposure duration were parameters having the greatest influence. Thiel et al., (1989) reported that application of paper mill sludge containing 59 to 80 ppt 2,3,7,8 TCDD to the land in a pine plantation had no noticeable negative effect on target populations of animals and birds.
USE OF HYPO-SLUDGE IN MAKING CONCRETE The innovative use of hypo sludge in concrete formulations as a supplementary cementitious material was tested as an alternative to traditional concrete. The cement has been replaced by waste paper sludge accordingly in the range of 0% (without Hypo sludge), 10%, 20%, 30% & 40% by weight for M25 and M40 mix. Concrete mixtures were produced, tested and compared in terms of strength with the conventional concrete. These tests were carried out to evaluate the mechanical properties like compressive strength up to 28 days and split strength for 56 days. The compressive strength increased up to 10% addition of hypo sludge and further increase in hypo sludge reduces the strengths gradually. This research work is concerned with experimental investigation on strength of concrete and to find the optimum percentage of hypo sludge as the partial replacement of cement by 10%, 20%, 30%, and 40% of Hypo Sludge in making concrete (Pitroda et al., 2012). The test results were analyzed and compared so as to get some conclusions as stated below : 1) Use of hypo sludge in concrete can save the paper industry disposal costs and produces a ‘greener’ concrete for construction. 2) Environmental effects from wastes and the amount of cement manufacturing can be reduced through the judicious use of hypo sludge. 3) A better measure by an innovative supplementary cementitious construction material is achieved, through this research. 4) The study concludes that hypo sludge can be an innovative supplementary cementitious construction material although judicious decisions for its use are to be taken by engineers.
Fig.3. Compressive Strength Testing (Pitroda et al., 2012)
Fig.4. Split Tensile Strength Testing (Pitroda et al., 2012)
Another study was conducted by R. Srinivasan, K. Sathiya and M. Palanisamy, 2010. The 28 days compressive and split tensile strength of M25 concrete made with hypo sludge as partial replacement of cement (Ref. Fig.5 and Fig. 6) was taken. From the test data presented in graphical form, it is seen that maximum compressive strength is obtained at around 40% cement replacement level. Of the various cement replacement levels, the maximum strength is observed again at around 40% replacement level. However, Srinivasan et al.,2010 concluded with the following comments : * Compressive strengths of the concrete were observed to increase as the percentage replacement level is increased up to 40% and then decrease. * The split tensile strengths followed the same trend as that for compressive strength results. * 30% to 40% replacement of cement with this waste (hypo sludge) material provides maximum strength. * Cost of cement could be reduced with the use of such waste materials.
* Environment effects from wastes and amount of cement manufacturing could be reduced through the use of hypo sludge. * A better measure by a new construction material was achieved.
Fig.5. Compressive strength for 28 days M25 Grade Concrete (Srinivasan et al.,2010)
Fig.6. Split tensile strength for 28 days M25 Grade Concrete (Srinivasan et al.,2010)
HYPO-SLUDGE USED WITH CEMENT MORTAR Fava et al., 2011 conducted a research on hypo-sludge to use it as a partial replacement with cement in mortar. Paper mill sludge is often incinerated for heat recovery and volume reduction. In Italy, about 600,000 ton of paper mill sludge isproduced yearly. About 6 kg of sludge is produced per ton of paper produced. The paper mill sludge is recovered from a primary mechanical separation process. When it is combusted as a single fuel source, it produces paper mill sludge ash (PA). In this project, PA was studied toevaluate its use as a supplementary cementitious material in mortars and concrete manufacturing. On the basis of the data collected, it was concluded that PA, if used to replace up to 10% of the Portland cement, shows a positive effect on the mechanical performance of mortars.On the other hand, because of its high fineness and consequently high water absorption, it required a higher amount of water. It was concluded that the use of PA should not be higher than 10% by weight of the cement replaced, unless mortar mixtures are judiciously proportioned (Fava et al., 2011). In the above mentioned study,the authors arrived at the following conclusions:
1) At 28 days, the mortars containing 5% PA exhibited a compressive strength higher than or as high as that of mortar made from cement only. 2) The results presented encouraged the researchers to undertakefurther study on the use of PA in concrete, which could lead toa reduction in the cost of mortars and concrete, as well as amethod for minimizing cost for disposal of PA. On the basis of the data collected from this experimental project, it can be concluded that the PA, particularly if it replacesup to 10% of cement, shows a positive effect on the development ofthe mechanical performance of mortars. Judicious use of PA andproper mixture proportioning can give a better contribution to the cement paste hardening, leading to an increase in the cement activity index.On the other hand, because of its high fineness and, consequently,high water absorption, the dosage of PA should not be too high (theupper limit currently appears to be 10% of the weight of cement). Further research is continuing regarding the benefits of PA in cement based construction materials and especially for the use of PA as a cement replacement material by greater than 10% of the weight of cement (Fava et al., 2011).The same study also used XRD and SEM analysis for the blended mortar.
Fig.7. X-Ray Diffraction (XRD) of PA (Fava et al., 2011)
X-ray diffraction analysis (Fig.7) also showed the presence of calcium oxide (CaO), gehlenite (Ca2Al2SiO7), and mayenite (Ca12Al14O33). In addition, other components such as Talc (3MgO.4SiO2H2O), Barium Sulfate (BaSO4), and Zinc Oxide (ZnO) were also probably present in small and variable percentages. PA was studied at increasing magnifications by using a scanning electron microscope (SEM) (Fig. 6).The dominant morphology of the PA consisted of minor fragmentsof clay/shale residue and agglomerated loose particles. Overall, theparticles ranged from 1 to 200 μm in size and their shapes variedwidely. Such results have been confirmed by others (Naik and Kraus 2000). On the basis of these
observations, it was concluded that the PA recovering system was particularly selective for non spherical morphologies (Fava et al., 2011).
Fig. . SEM observations of PA at different magnifications: (a) 500 μm; (b) 100 μm; (c) 50 μm; (d) 10 μm (Fava et al., 2011)
HYPO-SLUDGE AS CERAMIC BRICKS : The construction sector is experiencing the rapid emergence of waysto implement principles of sustainable development as well as a trend to achieve buildings with minimal energy consumption. In Spain, RD 47/2700 establishes the requirement that all new buildings constructedhave an energy performance certificate. Consumption of energy frombuildings constitutes about 33% of total consumption, with about halfof this energy lost through the walls. European standard EN832 statesthat, depending on location and climate, walls should be made of materialwith a heat transfer coefficient of 0.4–0.7 W/mK, the lower the better(L.Y. Jaramillo et al.,2007) EN 832:1998 (EN 832, Rendimientotérmico de los edificios-Cálculo del uso de la energía paralos edificiosresidenciales, Calefacción, CEN, Brussels, Belgium. cbe, 1998). Ultimately, the goal of these standards is toreduce final energy consumption. One of the great concerns of the construction sector having this kind of project is that using of waste materials lowers the quality of the brick. Previous studies show, however, that bricks to which sludge from the paper industry has been added can fulfill the quality parameters of manufactured bricks, decreasing brick density and avoiding both the typical changes in final color and the considerable surface defects caused by incorporating residue (L.Y. Jaramillo et al.,2007).
SAMPLE PREPARATION Martinez et al.,(2012) described and showed the schematic diagram for sample prepatation of ceramic brick incorporating hypo sludge (Fig.7). The sludge was produced by the waste water treatment plant and the paper waste in the production of paper pulp. These wastes were dried for 24 h at90 °C to remove
moisture. To obtain uniform particle size, all wastesand the clay were crushed and ground to yield a powder with a particlesize suitable to pass through a 150 μm sieve. Different amounts of waste were added to the raw clay body tostudy their effect on pore formation. The mixtures were homogenized in a blender and moulded under 54.5 MPa of pressure using a uniaxiallaboratory-type pressing Mega KCK-30 A. The amount of water (10%w/w) necessary for mixing was added to all of the mixtures to obtainadequate plasticity and absence of defects in the compression stage.Waste-free mixtures were also made as a reference. Solid bricks with30×10 mm cross-sections and a length of 60 mm were then formed.The shaped samples were dried for 48 h at 110 °C to reduce the moisturecontent. The dried samples were then fired in a laboratory-type electricallyheated furnace at a rate of 10 °C/min to 950 °C for 6h.
Fig.7. Schematic Diagram of Preparation of the Ceramic Brick Samples (Martinez et al., 2012) On the basis of the experimental investigation, Martinez et al.,2012 concluded with the follwing remarks about the use of paper mill waste as ceramic material development : 1) The use of wastes in manufacturing ceramicsis an option that coincides with the principles of sustainabledevelopment. 2) Wastes (hypo sludge) from the paper industry can provide an environmental and economic benefit, since it can be used as raw material for cement manufacturing. 3) The technique of N2 absorption–desorption and the BET and BJH methods used to determine the surface properties of the prepared samples show that the materials are mesoporous. 4) The results of water absorption and density show an increase inthe porosity of the specimens prepared. 5) This increase in porosity is accompanied by a decrease in compressivestrength, although the values obtained comply with those requiredby legislation. 6) The materials studied have significant thermal insulating properties that are increasingly important for these materials. 7) The addition of waste can save energy because the waste has ahigher heating value. 8) Of the two wastes added, the one that produces the best thermal properties in the pieces is the paper waste (Martinez et al., 2012).
CONCLUSION : Bangladesh is a country with huge population.Energy consumption is a crucial issue for overall development.Sustainability is the word which should be given utmost importance for the development of a
country like ours.Hypo-sludge utilisation in our country can bring a mass change in our economy and play an important role in engineering construction. Considering the cost of each cement bag as 500 taka which is current market price for every bag of cement saving upto 50 taka can be made if we can replace hyposludge upto 10 %.Furthermore around 66000 bags of cement per year can be produced by utilsing hyposludge. However, further studies are requiedto utilise hypo-sludge as a cement replacement material in different concrete construction works to determine the optimum replacement level and also save our environment from pollution.
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