Biodiesel production from an industrial residue: Alperujo

Industrial Crops and Products 52 (2014) 495–498

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Biodiesel production from an industrial residue: Alperujo Diógenes Hernández a,∗ , Luis Astudillo a , Margarita Gutiérrez a,∗ , Claudio Tenreiro b , Cesar Retamal b , Carla Rojas b a b

Institute of Chemistry of Natural Resources, University of Talca, Casilla 747, Talca, Chile1 Faculty of Engineering, University of Talca, Casilla 747, Talca, Chile2

a r t i c l e

i n f o

Article history: Received 20 August 2013 Received in revised form 25 October 2013 Accepted 29 October 2013 Keywords: Biodiesel Alperujo Transesterification Biomass Energy Olive residue

a b s t r a c t Alperujo is a combination of liquid and solid waste of olive oil processing, being dangerous for the environment. This residual does not have common commercial interest, and companies usually dispose of it in landfills where it can be toxic to the environment. The traditional method used in the Chilean olive oil industry produces 20% oil and 80% waste (alperujo). This study was undertaken to know the proper transesterification, amount of biodiesel production (ester) and physical properties of biodiesel from alperujo. In our lab, we obtained 94.7% high quality biodiesel and 5.3% glycerin from alperujo. © 2013 Published by Elsevier B.V.

1. Introduction The need for energy is increasing sharply due to the rapid increase in the world’s population and developing technologies. The need to seek new energy sources clean, reliable energies as well as environmentally friendly, has been stressed many times. While the current energy resources with limited reserves are decreasing, biomass has been recognized as one major world renewable energy source to supplement declining fossil fuel resources (Ozcimen and Karaosmanoglu, 2004; Jefferson, 2006). Even though raw biomass has significantly less energy content than petroleum, it has certain advantages compared to fossil fuels. First, biomass is a renewable organic resource and the most abundant that could be sustainably developed in the future. Second, biomass fixes carbon dioxide balance in the atmosphere by photosynthesis and third, it appears to have significant economic potential provided that fossil fuel prices increase in the future. Due to the lower contents of sulfur and nitrogen in biomass waste, its energy utilization also creates less environmental pollution and lower health risks than fossil fuel combustion (Cadenas and Cabezudo, 1998).

∗ Corresponding author. E-mail addresses: [email protected] (D. Hernández), [email protected] (L. Astudillo), [email protected] (M. Gutiérrez), [email protected] (C. Tenreiro), [email protected] (C. Retamal), lita [email protected] (C. Rojas). 1 Tel.: +56 71 200448. 2 Tel.: +56 75 201764. 0926-6690/$ – see front matter © 2013 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.indcrop.2013.10.051

Biodiesel, namely fatty acid methyl ester (FAME) fuel, has particularly excellent properties as renewable, biodegradable, and has environmentally friendly fewer CO2 and NOx emissions. FAME fuel may represent a good alternative to petroleum fuel and is receiving increasing attention throughout the world through the following advantages: (a) are easily available from common biomass sources, (b) they are represent a carbon dioxide-cycle in combustion, (c) have a considerable environmentally friendly potential, (d) there are many bene-fits the environment, economy and consumers in using and (e) they are biodegradable and contribute to sustainability (Demirbas, 2009; Alburquerque et al., 2004). Vegetable oils and animal fats are the principal biodiesel feedstocks, among which vegetable oils such as soybean oil, peanut oil, and cottonseed oil are widely used, but most of these oils are edible, and the cost is greater using them as feedstocks to produce biodiesel fuel for many countries (Albarran et al., 2004; Atadashi et al., 2012). Olive oil extraction is one of the most traditional crops in the Mediterranean region, the industrial process produced a number of adverse environmental problem that as increased amounts of wasterwater and solid residues. Alperujo is a waste product which originates from the process of olive oil extraction (two phases) and corresponds approximately to 80% of the processed fruits due to incorporation of water in the process. Alperujo is not friendly to the environment when discarded (Pozzi et al., 2010). The waste is a blend made of water, oil, cellulose, lignin, proteins, soluble carbohydrates, small portions of active phenol compounds and other derivatives (Alburquerque et al., 2004). Alperujo is a dark compound with an intense smell, highly organically charged, a

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moderately acid pH and a high conductivity (Borja et al., 2006; Niaounakis and Halvadakis, 2006). Its high content of fats, sugars, nitrogen, organic acids, polyalcohol, pectins, tannins, and polyphenol (Fiestas Ros de Ursinos, 1986; Martínez and Garrido, 1994; Sáiz et al., 1987) leads to serious ecological problems once alperujo is scattered on the soil. It also has a phototoxic activity that does not permit plants to germinate (Morillo, 2007), and a high polyphenol content that produces bad biological degradations into waters (Maestro et al., 1991). Other negative consequences can be seen in the damage caused by the wastes in the washing of the olive oil process, which contain pectins, soft tissues and oils (SanchezMonedero et al., 2008). Chile is a region of sudamerica where olive plantations are rapidly expanding, therefore alperujo is a toxic waste to the environment needs to be treated, Vera et al. (2009) showed that dehydrated olive cake can be conserved for several months with no detriment to its lipid composition and quality. And can be used as food alternative. Vlyssides et al. (2004) reported an integral strategic approach for reusing olive oil byproducts, where produced 1.14 kg of biogas from 100 kg of olives and others products as crude of antioxidants, organic fertilizer and shows new clean technology approaches to be utilized as ingredients in some cosmetics and pharmaceutical products, showing a decreased the environmental problems generated by the olive industries. Demirbas et al. (2000), reported the possibility of creating liquid fuel from used olive oil and olive cake. The by-products were either pyrolised or submitted to alkali catalyzed transesterification using methanolic solutions of NaOH, KOH, Na2 CO3 , or K2 CO3 . The alkali catalyzed processes could yield esters up to 94%, creating a fuel with specifications similar to diesel. Nonetheless, studies about the environment launched by national or international researchers (results obtained from the Faculty of Engineering and Institute at the University of Talca), together with information from the first Olive Culture Congress, Spain 2007, have shown that alperujo has a high energetic potential. In this study, alperujo has been used as the biomass to obtain biodiesel fuel, showing it to be promising as an eco-friendly alternative to obtain diesel fuel. 2. Materials and methods 2.1. Materials The sample of alperujo was obtained from Don Rafael Agriculture and Forestry (Talca, Chile). Certified methanol of 99.8% purity and catalysts—potassium hydroxide, and potassium methoxide—were also used, all pure grade from Merck (Barcelona, Spain). 2.2. Extraction and transesterification process 2.0 kg of alperujo obtained of industrial production of olive oils was submitted to a drying process in a Memmert-brand oven, at a controlled temperature (105 ◦ C for 8 h). Then, a sample was mixed with hexane in a 1:1 ratio and stirred for 30 min. Afterwards, it was decanted and filtered through a gauze and paper filter, obtaining two fractions: the solid phase (pits and pulp) and the liquid phase (hexane and oil). The latter were incorporated into a rotary evaporator at a temperature controlled 60 ◦ C where 100% of the hexane was recovered, leaving behind the oil. The oil obtained was purified through column chromatography packed with aluminum oxide (alumina) to extract the anthocyanin pigments (chlorophyll). Biodiesel from alperujo oil was obtained through trasesterification (Xu and Hanna, 2009). 610 g of the clean oil was mixed with a previously prepared methanolic KOH solution. For the reaction, a mixture of alcohol:oil was 1:2 (v/v) and 0.54% of catalyst

(w/w) in relation to the oil content. The resulting solution was kept under agitation to 50 rpm, to 60 ◦ C, for 1 h. Then, the reaction mixture was transferred to a separating funnel and allowed to cool to room temperature with separation of two phases, the upper consisted of methyl esters and the lower layer contained glycerol and other materials as catalyst, methanol, and soaps formed during the reaction and others. 2.3. Analytical procedure Upper phase obtained through transesterification was transferred to a ball connected to a refrigerant and heated in a heating mantle at 100 ◦ C, evaporating the excess alcohol. Afterwards, the residue corresponding to biodiesel was removed from the ball and its pH was determined potentiometrically with a pH meter (HANNA) obtained a value of 8.5, then these was adjusted to neutral value using a standard solution of phosphoric acid 1 N. The fatty acid profile of alperujo biodiesel and its esters was determined using a previously develop gas chromatography (GC) methods (Rashid et al., 2013). Reaction products were monitored by capillary column gas chromatography, using a Turbo Mass AutoSystem XL Perkin Elmer with mass detector. The injection system was split-splitless. The carrier gas was helium at a flow rate of 1 mL/min; the internal patron (Supelco) technique has been used in order to quantify the amount of the chemical species. The conventional analysis of biodiesel quality—acid value, iodine value, water content, density and viscosity—was carried out using the methods developed by the Complutense University of Madrid and were compared with biodiesel standards (The European Union Draft Standard prEN 14214). The chemical analysis of biodiesel was performed at the Chemistry Laboratory, Universidad de Talca, Campus Curico, following the official methods from AOAC. 2.4. Determining the mass balance in the processing of alperujo In order to quantify the extraction yield, the process mass balance was determined. Olive analysis displayed an average composition of 20% oil, 50% water and 30% pits and plant tissues. Water is added to the pulverized fruit to avoid clogging the decanter and the centrifuge, obtaining 20% extra virgen olive oil and 80% alperujo (62.31% water, 37.69% pits, plant matter and oil). If the alperujo is submitted to a drying process, 62.31% of the water is recovered and the 37.69% remaining corresponds to pits, plant tissue and oil. This 37.69% of the dried alperujo has on average 4% oil and 96% pits and plant tissue. If the dried alperujo is mixed with a solvent, it produces two phases. The liquid phase contains solvent and oil. As such, the alperujo’s 4% oil content is now recoverable and is nearly 100% fuel (94.7% biodiesel and 5.3% glycerin). Meanwhile, the solid phase (96%) composed of pits and plant tissue is strained and separated into 70% small particulate (plant tissue and fine pieces of pit) and 30% large particulate (pits). This process is summarized in the following process (Fig. 1). 3. Results and discussion Alperujo obtained as industrial residue generated 94.7% of biodiesel and 5.3% of glycerine, the use of this and others industrial residues for obtain biodiesel is a good alternative to generate new products giving an added value to the waste produced in large quantities by olivicola industry. The importance of the use these residues is because to the agricultural soil deterioration primarily by an increase in the pH, and water pollution depending on concentration, composition and the seasonal emergence of the wastes (Stamatakis, 2010).


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Table 1 Quality analysis and comparison of test results to the standard value. Property

Standard value

Measured value

Test method

Density at 15 ◦ C Viscosity at 40 ◦ C Flash point Cetane number Acidity index Iodine index Heating value

0.86–0.90 g/mL 3.50–5.00 mm2 /s Min. 120 ◦ C 48–60 Máx. 0.5 mg KOH/g sample Max. 120 g iodine/100 g –

0.86 g/mL 3.80 mm2 /s 126 ◦ C 49.60 0.35 mg KOH/g sample 8.41 g iodine/100 g 10,000 kcal/kg

NCh 822 or 2395 NCh 1950 NCh 69 NCh 1987 EN 14104 EN 14111 –

Treatment Olive fruit

Oil = 20% Water = 50% Pits and tissue = 30%.

Incorporation water Extra virgin oil 20%

Alperujo water= 62,31% 80% Pits, tissue and oil= 37,69% Drying Milling Oil = 4% Pits and tissue = 96% Washing with 60:40 mixture (60% solvent and 40% dry alperujo) solvent Solid phase (96%) pits and tissue

Liquid phase oil (4%) more solvent Solvent (100%)

Screening

Cleaning and distilled Oil (4%) Biodiesel 94,7%

Methoxide

Particle Particle small (70%) large (30%)

Table 2 Olive alperujo chemical characterization. Material

Official method

Result

Percentage of water Percentage of fiber (dry base) Protein and nitrogen (dry base) Percentage of oil (dry base) Ash (dry base) pH (dry base)

Oven method Gravimetric method Kjeldahl method Soxhlet method Muffle pH meter

62.30% 81.10% 13.11% 4.00% 1.71% 5.75

Table 3 Composition of organic fractions obtained with saponification. Fatty acid

Retention time (min)

Abundance (%)

9-Hexadecenoic Hexadecanoic 9-Octadecenoic 7-Hexadecenoic Heptadecanoic Octadecanoic

29.13 29.94 34.39 34.42 34.60 34.63

8 55 100 100 30 5

Glycerine 5.3% Fig. 1. Diagram of mass balance.

Biodiesel obtained from transesterification of alperujo was carried out in the presence of a basic catalyst (Moreira et al., 2013). The quality of biodiesel obtained depends on both the start material used as well as of production process. These factors affect physical–chemical characteristics of the produced biodiesel. The cetane number (CN) is a descriptor of diesel fuel ignition quality, the CN of biodiesel from alperujo was determined as 49.6, in concordance with reference values (Table 1). The CN has been included as fuel quality parameter of biodiesel standards, prescribing a minimum of 47 in the United States and 49 in some European countries (Knote et al., 2003). Knowing the CN of each component would help us apply the mathematical equation previously reported to verify this value, where the CN of biodiesel from alperujo could be is well-explained considering that each component contributes linearly to the overall CN by the equation (Knote, 2012):

CNmix = ˙AC × CNC where CNmix is the CN of the mixture, AC is the relative amount (vol.%) of an individual neat ester in the mixture, and CNC is the CN of the individual neat ester. As reduction of the high viscosity of vegetable oils, which can cause engine deposits, is the major reason for producing biodiesel fuels of lower viscosity, this parameter is prescribed in biodiesel standards. The viscosity of biodiesel from alperujo was determined to be 3.8 mm2 /s at 40 ◦ C. Thus, the viscosity of biodiesel is well within the ranges specified in the biodiesel standards values. Similar to the discussion of the CN, the viscosity of biodiesel could be determined as to function of viscosity of individual components to the same temperature (Knote and Steidley, 2005). A calculation,

analogous to above for the CN, using literature values for the individual components ought to yield a value on the order of 4.0. Density is not specified in standard of American Society for Testing and Materials D6751 but is included as a specification in EN 14214. It may be surmised that the primary reason for the inclusion of density in this last, is to exclude vegetable oils as triacylglycerols usually display density values >0.90 g/cm3 . Furthermore, similar to CN and viscosity, the density of the mix can be given for the density of the individual compounds in the mixture (Knote, 2012). Table 1 shows some quality parameters for the biodiesel obtained compared with reference values. The chemical analysis of alperujo was performed showing a significant degree of similarity with the values reported in literature (Alburquerque et al., 2004), but the fat content was reduced by about 90% while the fiber and nitrogen content increased. The chemical analysis results are shown in Table 2. Mass Gas Chromatography (MGC) was used to establish the components present in the biodiesel produced. The chromatogram analysis shows the preponderance of 9-octadecenoic acid and 7-hexadecanoic acid and other fatty acids in smaller amounts, showing a high degree of purity in the biodiesel obtained. The biodiesel composition is shown in Table 3. The mass balance shows a high yield of biodiesel, with a 94.7% production and 5.3% of glycerin. The use of the residual from the olive industry is very important, for it generates a possible use of a residual that is considered a contaminant. Biodiesel quality depends on several factors, being a reflection of its chemical and physical characteristics. The flash point is one of them. This parameter is the minimal temperature where enough vapors of the liquid form an inflammable mixture with the air. Faber et al. (2011) reported to biodiesels present elevated flash points (usually from ca. 160 to 170 ◦ C), if compared with mineral biodiesel whose minimum flash point can be as low as 38 ◦ C. With respect to the minimal flash point regulated for biodiesel, ASTM norm D6751, is the most restrictive, with the minimal

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temperature at 130 ◦ C, whereas the European norm, EN 14214, regulates the minimal flash point at 120 ◦ C and the Brazilian ANP 07/2008 at 100 ◦ C. Very small quantities of residual alcohol present in biodiesel provoke a significant decrease in the flash point and, therefore, according to the regulations, both the alcohol content and the flash point must be determined for each batch of biodiesel produced. The flash point obtained in this investigation is higher than the reference value, and this can be attributed to double or triple bonds that may still exist in the biodiesel and the presence of alcohol residual insomuch as the experimentally determined flash point temperature also informs the methanol or ethanol concentration in the biodiesel. The advantages of higher flash points in biodiesel include increased safety, making it easier to transport compared to other fuels, lower fire hazard, safer storage and reduced chances of uncontrolled detonation. Therefore, as a cheap byproduct in olive production, alperujo can be potentially used as a raw feedstock for producing biodiesel on a commercial scale from the olive oil industry. 4. Conclusions Biodiesel is an important new alternative of energy production. It can be produced from many vegetable oils, animal fat feedstocks or industrial residues. In this paper we present a methodology to produce biodiesel from alperujo’s residual oil. Since the alperujo contains oil, it is harmful for the environment. We start our study by characterizing the alperujo’s chemistry, determining the oil content (about 4%). This residual oil was turned into 94.7% biodiesel and 5.3% glycerin by means of a transesterification reaction. The transesterification process used for obtaining biodiesel from alperujo can produce chains with an average length of 17 carbons. This biodiesel fulfills the ASTM normative, and after this process, the oil-free alperujo is no longer dangerous for the environment. These results show that the alperujo oil present a possible viable alternative for the production of biodiesel. References Alburquerque, J., González, J., García, D., Cegarra, J., 2004. Agrochemical characterisation of “alperujo”, a solid byproduct of the two-phase centrifugation method for olive oil extraction. Bioresour. Technol. 91, 195–200. ˜ Albarran, A., Celis, R., Hermosin, M.C., Lopez-Pineiro, A., Cornejo, J., 2004. Behaviour of simazine in soil amended with final residue of the olive-oil extraction process. Chemosphere 54, 717–724. Atadashi, I.M., Aroua, M.K., Abdul Aziz, A.R., 2012. Sulaiman production of biodiesel using high free fatty acid feedstocks. Renew. Sustain. Energy Rev. 16, 3275–3285. Borja, R., Raposo, F., Rincón, B., 2006. Treatment technologies of liquid and solid waste from two-phase olive oil mills. Grasas y Aceites 5, 32–46.

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