Elsevier

Industrial Crops and Products

Volume 50, October 2013, Pages 485-493
Industrial Crops and Products

Assessing the potential of non-edible oils and residual fat to be used as a feedstock source in the enzymatic ethanolysis reaction

https://doi.org/10.1016/j.indcrop.2013.07.040Get rights and content

Highlights

  • The potential of six non-edible feedstocks were assessed to yield biodiesel by enzymatic route.

  • Lipase from Burkholderia cepacia immobilized on silica-PVA was used as biocatalyst.

  • All feedstocks were found to be suitable for biodiesel production, attaining yields higher than 94.6%.

  • The high yields obtained enable the product to be classified as a fuel according to ASTM standards.

Abstract

The focus of this work was to evaluate the potential of non-edible feedstocks to yield biodiesel by an enzymatic route. The ethanolysis of native oils from tropical crops, such as andiroba (Carapa guianensis), babassu (Orbignya sp.), jatropha (Jatropha curcas), macaw palm (Acrocomia aculeata), palm tree (Elaeis guineensis) and industrial waste (beef tallow) in solvent-free system was studied. All reactions were carried out with the microbial lipase from Burkholderia cepacia immobilized on a silica-polyvinyl alcohol matrix in a solvent-free system at 50 °C for a maximum period of 24 h. Under the conditions tested the biocatalyst was efficient in converting all fatty acids in the lipid feedstocks into the corresponding ethyl esters. Viscosity values for biodiesel samples obtained in each reaction (4.3 and 6.0 mm2/s) showed consistent reduction in relation to their original feedstock material, which also confirms the high conversion of triglycerides to ethyl esters (>94.5%). This comparative study shows that the formation of ethyl esters from different non-edible feedstocks was feasible and can provide a considerable increase in the prospect of attaining an environmental sustainability of the process as a whole.

Introduction

Biodiesel is defined as a biofuel derived from renewable biomass for use in internal combustion engines with ignition by compression or for generation of another type of energy that can partially or totally substitute fossil fuel (Takahashi and Ortega, 2010).

Conventionally, the production of industrial biodiesel is based on the chemical transesterification of vegetable oils with methanol, using homogeneous catalysts to promote the cleavage of triglycerides molecules and generate a mixture of fatty acid alkyl esters (biodiesel) (Leung et al., 2010). In this process, high rates can be obtained at short reaction times; however, the energy consumption is very high and requires significant downstream processing steps, such as washing, separation and purification (Ganesan et al., 2009). Alternatively, transesterification of triglycerides to produce biodiesel can be processed by heterogeneous catalysts, including immobilized enzymes (Bajaj et al., 2010). This process has many advantages over its chemical counterpart: it works well with fluctuating raw material quality, it needs fewer processing steps, it produces higher-quality glycerol (a valuable byproduct) and it uses less energy and generates less wastewater (Lam et al., 2010).

The enzymatic transesterification using ethanol instead of methanol has been suggested as a cleaner and more sustainable alternative for biodiesel production. (Stamenkovic et al., 2011). Furthermore, ethanol is a larger and heavier alcohol than methanol, which means a mass yield gain in the enzymatic synthesis of fatty acid ethyl esters (FAEE), resulting in a higher biodiesel per unit of oil (Brunschwing et al., 2012). In some countries, such as Brazil, ethanol is sold at lower prices than methanol, which means that the alcohol component is always significantly cheaper than the oil component. Thus, the extra volume gain when using ethanol instead of methanol could become a major sales argument, particularly for the Brazilian market (Stamenkovic et al., 2011, Brunschwing et al., 2012).

The fundamental advantage of an enzymatic biodiesel process is that triglycerides (and partial glycerides), as well as free fatty acids (FFA), can be efficiently transformed into biodiesel under the same mild conditions (Lam et al., 2010). By selecting the appropriate enzyme, it is possible to make a continuous single-step process, even with very high FFA content in the oil. This allows the use of low-quality and non-edible oils, without causing a negative impact on the environment (Lam et al., 2010, Adlercreutz, 2013).

The choice of feedstock for biodiesel production depends largely on geography, with rapeseed and sunflower oils dominating the European production, soybean oil dominating the USA and Latin American production, and palm oil mainly being used in Asia and Brazil. The use of edible oils for fuel production is controversial, and with increasing prices, there is a growing interest in alternative feedstocks. It is clear that the search for beneficial biodiesel sources should focus on feedstocks that do not compete with food crops, do not lead to land-clearing and provide greenhouse-gas reductions. These feedstocks include not only high-yielding (Table 1), non-edible tropical crops, such as andiroba (Carapa guianensis), babassu (Orbignya sp.), jatropha (Jatropha curcas), macaw palm (Acrocomia aculeata), palm tree (Elaeis guineensis), but also waste material as beef tallow. Large amounts of these non-edible oil plants are available in several regions of Brazil (Bergmann et al., 2013) with low cost of exploration and beef tallow becomes a second source of raw material to produce biodiesel in many countries. Saponification number, iodine value and fatty acid profile play an important role in selection of feedstock for biodiesel production. Based on these parameters, the physicochemical properties of several feedstocks (some of which still little explored) were investigated in order to identify their potential as a starting material in the enzymatic transesterification reactions carried out under suitable conditions.

Lipase from Burkholderia cepacia was immobilized on epoxy silica-polyvinyl alcohol (SiO2-PVA) composite; the enzyme was chosen based on its suitability for typical biotransformation applications (Freitas et al., 2009, Da Rós et al., 2010). In addition, to the conventional methods of analysis, information on the quality of the biodiesel samples obtained by 1H NMR, as well as thermogravimetric analysis (TGA), help to attest the efficiency of the transesterification reaction and to select the feedstocks which gave samples having properties in accordance with standard specification to be used as a fuel.

Section snippets

Materials and methods

Commercial B. cepacia lipase, from Amano Pharmaceuticals (Nagoya, Japan), in a crude form was used without further purification. Tetraethoxysilane (TEOS) was acquired from Aldrich Chemical Co. (Milwaukee, WI, USA). Epichlorohydrin, hydrochloric acid (minimum 36%), ethanol (minimum 99%), polyvinyl alcohol (PVA molecular weight 72,000) and polyethylene glycol (PEG molecular mass 1500) were supplied by Reagen (RJ, Brazil). The feedstocks were obtained from several suppliers as follows: andiroba

Feedstock chemical properties

Physicochemical properties, including the fatty acid profile, are important to determine the suitability of the feedstocks for the production of biodiesel. Feedstock quality influences not only the transesterification reaction, but also the quality of the biodiesel generated. The feedstocks used in this study were characterized according to the methodology recommended by official methods; the most important properties are shown in Table 2.

Acidity and peroxide values reveal the feedstock

Conclusion

All feedstocks analyzed in this work proved to be suitable for biodiesel production. Physicochemical properties of feedstocks were assessed and all samples revealed similar characteristics, attaining high conversion (>92%) in 24 h reaction. The biocatalyst showed consistent selectivity by producing the corresponding ester from each fatty acid. Analytical techniques, including viscosimetry, thermogravimetry and 1H NMR spectroscopy proved to be practical aids in the selection of the most suitable

Acknowledgments

The authors wish to thank Dr. Jayne C.S. Barboza for helping in the 1H NMR interpretations. This work was supported financially by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Coordenação de Aperfeiçoamento de Pessoal de Ensino Superior (CAPES).

References (33)

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