Recent trends in biodiesel production

Document Type: Review Paper


1 Microbial Biotechnology and Biosafety Department, Agricultural Biotechnology Research Institute of Iran (ABRII), AREEO, Karaj, Iran.

2 Biofuel Research Team (BRTeam), Karaj, Iran.

3 Department of Chemical Engineering, Isfahan University of Technology, 84156-83111 Isfahan, Iran.

4 Swedish Centre for Resource Recovery, University of Borås, 501 90 Borås, Sweden.

5 Center for Environmental Research and Technology (CE-CERT), Bourns College of Engineering, University of California, Riverside, California, USA.


This article fully discusses the recent trends in the production of one the most attractive types of biofuels, i.e., biodiesel.with a focus on the existing obstacles for its large scale production. Moreover, recent innovations/improvements under three categories of upstream, mainstream, and downstream processes are also presented. Upstream strategies are mainly focused on seeking more sustainable oil feedstocks and/or enhancing the quality of waste-oriented ones. The mainstream strategies section highlights the numerous attempts made to enhance agitation efficiency including chemical and/or mechanical strategies. Finally, the innovative downstream strategies basically dealing with 1) separation of biodiesel and glycerin, 2) purification of biodiesel and glycerin, and 3) improving the characteristics of the produced fuel, are comprehensively reviewed.

Graphical Abstract

Recent trends in biodiesel production


Algal Biomass Organization (ABO), Available at (accessed on 10 August 2015).

Anastopoulos, G., Lois, E., Serdari, A., Zanikos, F., Stournas, S., Kalligeros, S., 2001. Lubrication properties of low-sulfur diesel fuels in the presence of specific types of fatty acid derivatives. Energy  Fuels. 15(1), 106-112.

Atadashi, I.M., Aroua, M.K., Abdul Aziz, A.R., Sulaiman, N.M.N., 2011. Membrane biodiesel production and refining technology: a critical review. Renew. Sustain. Energy Rev.15(9), 5051-5062.

Azocar, L., Ciudad, G.,  Heipieper, H.J., Navia, R., 2010. Biotechnological processes for biodiesel production using alternative oils. Appl. Microbiol. Biotechnol.  88, 621-636.

Barnard, T.M., Leadbeater, N.E., Boucher, M.B., Stencel, L.M., Wilhite, B.A., 2007. Continuous-flow preparation of biodiesel using microwave heating. Energy Fuels. 21(3), 1777-1781.

Beetul, K., Sadally, S.B., Taleb-Hossenkhan, Bhagooli, R., Puchooa, D., 2014. An investigation of biodiesel production from microalgae found in Mauritian waters. Biofuel Res. J. 1(2), 58-64.

Beopoulos, A., Nicaud, J.M., Gaillardin, C., 2011. An overview of lipid metabolism in yeasts and its impact on biotechnological processes. Appl. Microbiol. Biotechnol. 90, 1193-1206.

Bhave, R., Kuritz, T., Powell, L., Adcock, D., 2012. Membrane-based energy efficient dewatering of microalgae in biofuels production and recovery of value added co-products. Environ. Sci. Technol. 46, 5599-5606.

Bilad, M.R., Arafat, H.A., Vankelecom, I.F.J., 2014. Membrane technology in microalgae cultivation and harvesting: a review. Biotechnol. Adv. 32(7), 1283-1300.

Bojan, S.G., Durairaj, S.K., 2010. Producing biodiesel from high free fatty acid Jatropha curcas oil by a two step method - an Indian case study. J. Sustain.  Energy Environ. 3, 63-66.

Boocock, D.G.B., 2004. Process for production of fatty acid methyl esters from fatty acid triglycerides. US Patent 6712867.

Brennan, L., Owende, P., 2010. Biofuels from microalgae - a review of technologies for production, processing, and extractions of biofuels and co-products. Renew. Sustain. Energy Rev. 14(2), 557-577.

Buckwalter, P., Embaye, T., Gormly, S., Trent, J.D., 2013. Dewatering microalgae by forward osmosis. Desalination. 312, 19-22.

Canackci, M., Gerpen, J.V., 2003. A pilot plant to produce biodiesel from high free fatty acid feedstocks. Trans. ASAE. 46(4), 945-954.

Chen, C.Y., Yeh, K.L., Aisyah, R., Lee, D.J., Chang, J.S., 2011. Cultivation, photobioreactor design and harvesting of microalgae for biodiesel production: a critical review. Bioresour. Technol. 102(1), 71-81.

Chisti, Y., 2007. Biodiesel from microalgae. Biotechnol. Adv. 25, 294-306.

Chisti, Y., 2008. Biodiesel from microalgae beats bioethanol. Trends Biotechnol. 26(3), 126-131.

Chisti, Y., 2013a. Constraints to commercialization of algal fuels.  J. Biotechnol. 167(3), 201-214.

Chisti, Y., 2013b. Raceways-based production of algal crude oil. Green. 39(3-4), 195-216.

Chung, K.H., Chang, D.R., Park, B.G., 2008. Removal of free fatty acid in waste frying oil by esterification with methanol on zeolite catalysts.  Bioresour. Technol. 99, 7438-7443.

Clean cities alternative fuel price report April 2015. U.S. Department of Energy. Available at  (accessed on 10 August 2015).

Cvengros, J., Cvengrosova, Z., 2004. Used frying oils and fats and their utilization in the production of methyl esters of high fatty acids. Biomass Bioenergy. 27, 173-181.

Daroch, M., Geng, S., Wang, G., 2013. Recent advances in liquid biofuel production from algal feedstocks. Appl. Energy. 102, 1371-1381.

Devan, P.K., Mahalakshmi, N.V., 2009. Study of the performance, emission and combustion characteristics of a diesel engine using poon oil-based fuels. Fuel process. Technol. 90(4), 513-519.

Dias, J.M., Alvim-Ferraz, M.C.M., Almeida, M.F., 2008. Comparison of different homogeneous alkali catalysts during transesterification of waste and virgin oils and evaluation of biodiesel quality. Fuel. 87, 3572-3578.

El Sabagh, S.M., Keera S.K., Taman, A.R., 2011. The characterization of biodiesel fuel from waste frying oil. Energy Sources Part A. 33, 401-409.

Ferrett, G., 2007.  Biofuels ‘crime against humanity’. BBC News. 27.

Gerardo, M.L., Oatley-Radcliffe, D.L., Lovitt, R.W., 2013. Minimizing the energy requirement of dewatering Scenedesmus sp. by microfiltration: performance, costs, and feasibility. Environ. Sci. Technol. 48(1), 845-853.

Gerardo, M.L., Oatley-Radcliffe, D.L., Lovitt, R.W., 2014. Integration of membrane technology in microalgae biorefineries. J. Membr. Sci. 464, 86-99.

Ghadge, S.V. Raheman, H., 2005. Biodiesel production from Mahua (Madhuca indica) oil having high free fatty acids. Biomass Bioenergy. 28, 601-605.

Griffiths, M.J., van Hille, R.P., Harrison, S.T.L., 2012. Lipid productivity, settling potential and fatty acid profile of 11 microalgal species grown under nitrogen replete and limited conditions. J. Appl. Phycol. 24(5), 989-1001.

Gui, M.M., Lee, K.T., Bhatia, S., 2008. Feasibility of edible oil vs. nonedible oil vs. waste edible oil as biodiesel feedstock. Energy. 33, 1646-1653.

Haase, R., Bielicki, J., Kuzma, J., 2013. Innovation in emerging energy technologies: A case study analysis to inform the path forward for algal biofuels. Energy Policy. 61, 1595-1607.

Hájek, M., Skopal, F., 2010. Treatment of glycerol phase formed by biodiesel production. Bioresour. Technol. 101(9), 3242-3245.

Hajjari, M., Ardjmand, M., Tabatabaei, M., 2014. Experimental investigation of the effect of cerium oxide nanoparticles as a combustion-improving additive on biodiesel oxidative stability: mechanism. RSC Adv. 4(28), 14352-14356.

Harvey, A.P., Mackley, M.R., Seliger, T., 2003. Process intensification of biodiesel production using a continuous oscillatory flow reactor. J. Chem. Technol. Biotechnol. 78(2-3), 338-341.

Hasheminejad, M., Tabatabaei, M., Mansourpanah, Y., Khatami far, M., Javani, A., 2011. Upstream and downstream strategies to economize biodiesel production. Bioresour. Technol. 102(2), 461-468, 2011.

Hayyan, A., Alam, Md.Z., Mirghani, M.E.S., Kabbashi, N.A., Hakimi, N.I.N.M., Siran, Y.M., Tahiruddin, S., 2010. Sludge palm oil as a renewable raw material for biodiesel production by two-step processes. Bioresour. Technol. 101, 7804-7811.

Heasman, M., Diemar, J., O'connor, W., Sushames, T., Foulkes, L., 2000. Development of extended shelf-life microalgae concentrate diets harvested by centrifugation for bivalve mollusks - a summary. Aquacult. Res. 31(8-9), 637-659.

Hompson, J.C., He, B.B., 2007. Biodiesel production using static mixers. Trans. ASABE. 50(1), 161-165.

Hosseini, M., Nikbakht, A.M., Tabatabaei, M., 2012. Biodiesel production in batch tank reactor equipped to helical ribbon-like agitator. Mod. Appl. Sci. 6(3), 40-45.

Huang, Y.P., Chang, J.I., 2010. Biodiesel production from residual oils recovered from spent bleaching earth. Renew. Energy. 35, 269-274.

Javani, A., Hasheminejad, M., Tahvildari, K., Tabatabaei, M., 2012. High quality potassium phosphate production through step-by-step glycerol purification: A strategy to economize biodiesel production. Bioresour. Technol. 104, 788-790.

Kannan, G.R., Karvembu, R., Anand, R., 2011. Effect of metal based additive on performance emission and combustion characteristics of diesel engine fuelled with biodiesel. Appl. Energy. 88(11), 3694-3703.

Karatay, S.E., Dönmez, G., 2011. Microbial oil production from thermophile cyanobacteria for biodiesel production. Appl. Energy. 88(11), 3632-3635.

Ki-Teak, L., Foglia, T.A., 2002. Production of alkyl ester as biodiesel from fractionated lard and restaurant grease. J. Am. Oil Chem. Soc. 79(2), 191-195.

Kombe, G.G., Temu, A.K., Rajabu, H.M., Mrema, G.D., 2012. High free fatty acid (FFA) feedstock pre-treatment method for biodiesel production. Proc. 2nd Int. Conf. Adv. Eng. Technol. 176-182.

Kongjao, S., Damronglerd, S., Hunsom, M., 2010. Purification of crude glycerol derived from waste used-oil methyl ester plant. Korean J. Chem. Eng. 27(3), 944-949.

Lertsathapornsuk V., Pairintra R., Ruangying P., Krisnangkur K., 2005. Continuous transethylation of vegetable oils by microwave irradiation, In: Proc. 1st Conf. Energy Network. Thailand, RE11-RE14.

Liang, M.H., Jiang, J.G., 2013. Advancing oleaginous microorganisms to produce lipid via metabolic engineering technology. Prog. Lipid Res. 52(4), 395-408.

Liu, X., Brune, D., Vermaas, W., Curtiss, R., 2010a. Production and secretion of fatty acids in genetically engineered cyanobacteria. Proc. Natl. Acad. Sci. U.S.A.

Liu, T., Vora, H., Khosla, C., 2010b. Quantitative analysis and engineering of fatty acid biosynthesis in E. coli. Metab. Eng. 12(4), 378-386.

Lu, H., Liu, Y., Zhou, H., Yang, Y., Chen, M., Liang, B., 2009. Production of biodiesel from Jatropha curcas L. oil. Comput. Chem. Eng. 33, 1091-1096.

Lundquist, T.J., Woertz, I.C., Quinn, N.W.T., Benemann, J.R., 2010. A realistic technology and engineering assessment of algae biofuel production. Report of Energy Biosciences Institute, University of California, USA.

Machado, I.M., Atsumi, S., 2012. Cyanobacterial biofuel production. J. Biotechnol. 162(1), 50-56.

Manosak, R., Limpattayanate, S., Hunsom, H., 2011. Sequential-refining of crude glycerol derived from waste used-oil methyl ester plant via a combined process of chemical and adsorption. Fuel Process. Technol. 92(1), 92-99.

Mirzajanzadeh, M., Tabatabaei, M., Ardjmand, M., Rashidi, A., Ghobadian, B., Barkhi, M., Pazouki, M., 2015. A novel soluble nano-catalysts in diesel–biodiesel fuel blends to improve diesel engines performance and reduce exhaust emissions. Fuel. 139, 374- 382.

Mofijur, M., Masjuki, H.H., Kalam, M.A., Hazrat, M.A., Liaquat, A.M., Shahabuddin, M., Varman, M., 2012. Prospects of biodiesel from Jatropha in Malaysia. Renew. Sustain. Energy Rev. 16(7), 5007-5020.

Mohammadi, P., Nikbakht, A.M., Tabatabaei, M., Farhadi, K., Mohebbi, A., Khatami far, M., 2012. Experimental investigation of performance and emission characteristics of DI diesel engine fueled with polymer waste dissolved in biodiesel-blended diesel fuel. Energy. 46(1), 596-605.

Mohammadi, P., Tabatabaei, M., Nikbakht, A.M., Farhadi, K., Castaldi, M.J., 2013. Simultaneous energy recovery from waste polymers in biodiesel and improving fuel properties. Waste Biomass Valorization. 4(1), 105-116.

Mohammadi, P., Tabatabaei, M., Nikbakht, A.M., Esmaeili, Z., 2014. Improvement of the cold flow characteristics of biodiesel containing dissolved polymer wastes using acetone. Biofuel Res. J. 1(1), 26-29.

Montefrio, M.J., Xinwen, T., Obbard, J.P., Montefrio, M.J., Xinwen, T., Obbard, J.P., 2010. Recovery and pre-treatment of fats, oil and grease from grease interceptors for biodiesel production. Appl. Energy. 87, 3155-3161.

Moser, B.R., 2011. Biodiesel production, properties, and feedstocks. Biofuels, Springer New York, 285-347.

Mythili, R., Venkatachalam, P., Subramanian, P., Uma, D., 2014. Recovery of side streams in biodiesel production process. Fuel.117, 103-108.

Noipin, K.N., Kumar, S., 2014. Optimization of ethyl ester production assisted by ultrasonic irradiation. Ultrason. Sonochem. 22, 548-558.

Noureddin, A., Shirazi, M.M.A., Tofeily, J., Kazemi, P., Motaee, E., Kargari, A., Mostafaei, M., Akia, M., Hamieh, T., Tabatabaei, M., 2014. Accelerated decantation of biodiesel–glycerol mixtures: Optimization of a critical stage in biodiesel biorefinery. Sep. Purif. Technol. 132, 272-280.

Oh, P.P., Lau, H.L.N., Chen, J., Chong, M.F., Choo, Y.M., 2012. A review on conventional technologies and emerging process intensification (PI) methods for biodiesel production. Renew. Sustain. Energy Rev. 16(7), 5131-5145.

Ong, H.C., Mahlia, T.M.I., Masjuki, H.H., Norhasyima, R.S., 2011. Comparison of palm oil, Jatropha curcas and Calophyllum inophyllum for biodiesel: a review. Renew. Sustain. Energy Rev. 15(8), 3501-3515.

Ouachab, N., Tsoutsos, T., 2012. Study of the acid pretreatment and biodiesel production from olive pomace oil. J. Chem. Technol. Biotechnol. 88, 1175-1181.

Parmar, A., Singh, N.K., Pandey, A., Gnansounou, E., Madamwar, D., 2011. Cyanobacteria and microalgae: a positive prospect for biofuels. Bioresour. Technol. 102(2), 10163-10172.

Peyravi, M., Rahimpour, A., Jahanshahi, M., 2015. Developing nanocomposite PI membranes: morphology and performance to glycerol removal at the downstream processing of biodiesel production. J. Membr. Sci. 473, 72-84.

Pinzi, S., Leiva, D., López‐García, I., Redel‐Macías, M.D., Dorado, M.P., 2014. Latest trends in feedstocks for biodiesel production. Biofuels, Bioprod. Biorefin. 8(1), 126-143.

Pitakpoolsil, W., Hunsom, M., 2014. Treatment of biodiesel wastewater by adsorption with commercial chitosan flakes: parameter optimization and process kinetics. J. Environ. Manage. 133, 284-292.

Qiu, Z., Zhao, L., Weatherley, L., 2010. Process intensification technologies in continuous biodiesel production. Chem. Eng. Process. Process Intensif. 49(4), 323-330.

Ramadhas, A.S., Jayaraj, S., Muraleedharan, C., 2005. Biodiesel production from high FFA rubber seed oil. Fuel. 84(4), 335-340.

Ribeiro, N.M., Pinto, A.C., Quintella, C.M., da Rocha, G.O., Teixeira, L.S.G., Guarieiro, L.L.N., do Carmo Rangel, M., et al., 2007. The role of additives for diesel and diesel blended (ethanol or biodiesel) fuels: a review. Energy Fuels. 21(4), 2433-2445.

Ruffing, A.M., 2011. Engineered cyanobacteria: teaching an old bug new tricks. Bioeng. Bugs. 3, 136-149.

Sadhik Basha, J., Anand, R.B., 2012. Effects of nanoparticle additive in the water-diesel emulsion fuel on the performance, emission and combustion characteristics of a diesel engine. Int. J. Veh. Des. 59(2-3), 164-181.

Sahafi, S.M., Goli, S.A.H., Tabatabaei, M., Nikbakht, A.M., Pourvosoghi, N., 2015. The reuse of waste cooking oil and spent bleaching earth to produce biodiesel. Energy Sources Part A. In press.

Sajjadi, B., Abdul Aziz, A.R., Ibrahim, S., 2015. Mechanistic analysis of cavitation assisted transesterification on biodiesel characteristics. Ultrason. Sonochem. 473, 72-84.

Sarin, R., Sharma, M., Sinharay, S., Malhotra, R.K., 2007. Jatropha–palm biodiesel blends: an optimum mix for Asia. Fuel. 86(10), 1365-1371.

Sharma, Y.C., Singh, B., Madhu, D., Liu, Y., Yaakob, Z., 2014. Fast synthesis of high quality biodiesel from ‘waste fish oil‘ by single step transestrification. Biofuel Res. J. 1(3), 78-80.

Shibasaki-Kitakawa, N., Honda, H., Kuribayashi, H., Toda, T., Fukumura, T., Yonemoto, T., 2007. Biodiesel production using anionic ionexchange resin as heterogeneous catalyst. Bioresour. Technol. 98, 416-

Shirazi, M.M.A., Bastani, D., Kargari, A., Tabatabaei, M., 2013a. Characterization of polymeric membranes for membrane distillation using atomic force microscopy. Desalin. Water Treat. 51(31-33), 6003-6008.

Shirazi, M.M.A., Kargari, A., Tabatabaei, M., Mostafaeid, B., Akia, M., Barkhi, M., Shirazi, M.J.A., 2013b. Acceleration of biodiesel–glycerol decantation through NaCl-assisted gravitational settling: a strategy to economize biodiesel production. Bioresour. Technol. 134, 401-406.

Shirazi, M.M.A., Kargari, A., Bazgir, S., Tabatabaei, M., Shirazi, M.J.A., Abdullah, M.S., Matsuura, T., Ismail, A.F., 2013c. Characterization of electrospun polystyrene membrane for treatment of biodiesel's waterwashing
effluent using atomic force microscopy. Desalination. 329 , 1-8.

Shirazi, M.J.A., Bazgir, S., Shirazi, M.M.A., 2014a. Edible oil mill effluent; a low-cost source for economizing biodiesel production: Electrospun nanofibrous coalescing filtration approach. Biofuel Res. J. 1(1), 39-42.

Shirazi, M.M.A., Kargari, A., Tabatabaei, M., 2014b. Evaluation of commercial PTFE membranes in desalination by direct contact membrane distillation. Chem. Eng. Process. Process Intensif. 76, 16-25.

Shirazi, M.M.A., Kargari, A., Tabatabaei, M., Ismail, A.F., Matsuura, T., 2014c. Assessment of atomic force microscopy for characterization of PTFE membranes for membrane distillation (MD) process. Desalin. Water Treat. 1-10.

Shirazi, M.M.A., Kargari, A., Tabatabaei, M., 2015. Sweeping gas membrane distillation (SGMD) as an alternative for integration of bioethanol processing: study on a commercial membrane and operating parameters. Chem. Eng. Commun. 202(4), 457-466.

Shirazi, M.M.A., Tabatabaei, M., 2014. Biofuels, In: Sharma, U.C., Kumar, S., Prasad, R. (Eds.), Energy Science and Technology (Vol. 6), Studium Press LLC, USA.

Shuman, T.R., Mason, G., Marsolek, M.D., Lin, Y., Reeve, D., Schacht, A., 2014. An ultra-low energy method for rapidly pre-concentrating microalgae. Bioresour. Technol. 158, 217-224.

Silitonga, A.S., Masjuki, H.H., Mahlia, T.M.I., Ong, H.C., Chong, W.T., Boosroh, M.H., 2013. Overview properties of biodiesel diesel blends from edible and non-edible feedstock. Renew. Sustain. Energy Rev. 22, 346-360.

Singh, A.K., Fernando, S.D., Hernandez, R., 2007. Base-catalyzed fast transesterification of soybean oil using ultrasonication. Energy Fuels. 21(2), 1161-1164.

Singh, I., Taggar, M.S., 2014. Recent Trends in Biodiesel Production—An Overview. Int. J. Appl. Eng. Res. 9(10), 1151-1158.

Sitepu, I.R., Garay, L.A., Sestric, R., Levin, D., Block, D.E., Bruce German, J., Boundy-Mills, K.L., 2014. Oleaginous yeasts for biodiesel: current and future trends in biology and production. Biotechnol. Adv. 32(7), 1336-1360.

Sivakumar, P., Sindhanaiselvan, S., Gandhi, N.N., Devi, S.S., Renganathan, S., 2013. Optimization and kinetic studies on biodiesel production from underutilized Ceiba Pentandra oil. Fuel. 103, 693-698.

Stephenson, P.G., Moore, C.M., Terry, M.J., Zubkov, M.V., Bibby, T.S., 2011. Improving photosynthesis for algal biofuels: toward a green revolution. Trends Biotechnol. 29(12), 615-623.

Stojković, I.J., Stamenković, O.S., Povrenović, D.S., Veljković, V.B., 2014. Purification technologies for crude biodiesel obtained by alkali-catalyzed Transestrification. Renew. Sustain. Energy Rev. 32, 1-15.

Strathmann, H., 2011. Introduction to membrane science and technology. Wiley-VCH, Weinheim.

Sulistyo, H., Rahayu, S.S., Winoto, G., Suardjaja, I.M., 2008. Biodiesel production from high iodine number candlenut oil. World Acad. Sci. Eng. Technol. 48, 485-488.

Sun, A., Davis, R., Starbuck, M., Ben-Amotz, A., Pate, R., Pienkos, P., 2011. Comparative cost analysis of algal oil production for biofuels. Energy. 36, 5169-5179.

Sundaramurthy, J., Li, N., Kumar, P.S., Ramakrishna, S., 2014. Perspective of electrospun nanofibers in energy and environment. Biofuel Res. J. 1(2), 44-54.

Tabatabaei, M., Khatami far, M., 2009. Pro spinning tube in tube reactor (Pro-STT) equipped with high voltage system for the production of biodiesel and glycerin. IR Patent 62533.

Tabatabaei, M., Tohidfar, M., Salehi Jouzani, G., Safarnejad, M.R., Pazouki, M., 2011. Biodiesel production from genetically engineered microalgae: Future of bioenergy in Iran. Renew. Sustain. Energy Rev. 15(4), 1918-1927.

Talebi, A.F., Mohtashami, S.K., Tabatabaei, M., Tohidfar, M., Bagheri, A., Zeinalabedini, M., Hadavand Mirzaei, H., Mirzajanzadeh, M., Malekzadeh Shafaroudi, S., Bakhtiari, S., 2013. Fatty acids profiling: a selective criterion for screening microalgae strains for biodiesel production. Algal Res. 2(3), 258-267.

Talebi, A.F., Tabatabaei, M., Chisti, Y., 2014. BiodieselAnalyzer©: a userfriendly software for predicting the properties of prospective biodiesel. Biofuel Res. J. 2, 55-57.

Talebi, A.F., Tohidfar, M., Bagheri, A., Lyon, S.R., Salehi-Ashtiani, K., Tabatabaei, M., 2014. Manipulation of carbon flux into fatty acid biosynthesis pathway in Dunaliella salina using AccD and ME genes to enhance lipid content and to improve produced biodiesel quality. Biofuel Res. J. 1(3), 91-97.

US Energy Information Administration (US-EIA), 2014. Monthly biodiesel production report.

Venkateswarlu, K., Murthy, B.S.R., Subbarao, V.V., 2015. An experimental investigation to study the effect of fuel additives and exhaust gas recirculation on combustion and emissions of diesel–biodiesel blends. J. Braz. Soc. Mech. Sci. Eng. 1-10.

Vonortas, A., Papayannakos, N., 2014. Comparative analysis of biodiesel versus green diesel. Wiley Interdiscip. Rev. Energy Environ. 3(1), 3-23.

Zhang, Y., Dube, M.A., McLean, D.D., Kates, M., 2003. Biodiesel production from waste cooking oil: 1. Process design and technological assessment. Bioresour. Technol. 89, 1-16.

Zhang, J., Jiang, L., 2008. Acid-catalyzed esterification of Zanthoxylum bungeanum seed oil with high free fatty acids for biodiesel production. Bioresour. Technol. 99, 8995-8998.

Zhu, X.G., Long, S.P., Ort, D.R., 2008. What is the maximum efficiency with which photosynthesis can convert solar energy into biomass?. Curr. Opin. Biotechnol. 19, 153-159.