Review Upstream and downstream strategies to economize biodiesel production Meisam Hasheminejad a , Meisam Tabatabaei a,⇑ , Yaghoub Mansourpanah b , Mahdi Khatami far c , Azita Javani d a Biodiesel Research Team (BRT), Microbial Biotechnology and Biosafety Department, Agricultural Biotechnology Research Institute of Iran (ABRII), Seed and Plant Improvement Institute’s Campus, 31535-1897, Mahdasht Road, Karaj, Iran b Department of Chemistry, Faculty of Science, Lorestan University, Khorramabad, Iran c Iran Renewable Energy Organization (SUNA), 146861-1387, Tehran, Iran d Department of Applied Chemistry, Faculty of Chemistry, Islamic Azad University, North Tehran Branch, 191367-4711, Tehran, Iran article info Article history: Received 15 May 2010 Received in revised form 3 September 2010 Accepted 3 September 2010 Available online 1 October 2010 Keywords: Biodiesel production Upstream Downstream Strategies Economize abstract In recent years biodiesel has drawn considerable amount of attention as a clean and renewable fuel. Bio- diesel is produced from renewable sources such as vegetable oils and animal fat mainly through catalytic or non-catalytic transesterification method as well as supercritical method. However, as a consequence of disadvantages of these methods, the production cost increases dramatically. This article summarizes dif- ferent biodiesel production methods with a focus on their advantages and disadvantages. The down- stream and upstream strategies such as using waste cooking oils, application of non-edible plant oils, plant genetic engineering, using membrane separation technology for biodiesel production, separation and purification, application of crude glycerin as an energy supplement for ruminants, glycerin ultra- purification and their consequent roles in economizing the production process are fully discussed in this article. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Energy supply and its security issues have been the topic of interest lately. With growing environmental awareness about the negative implications brought by excessive usage of fossil fuels, the race for finding alternative energy as their substitutions is get- ting heated up (Lim and Teong, 2010). Recently, biodiesel has been receiving increasing attention not only as an alternative but also as a sustainable fuel (Rajendra et al., 2009). It is used for diesel en- gines (Haas, 2005) and is becoming well-known as an environmen- tally friendly fuel due to its non-toxic and biodegradable characteristics (Ellis et al., 2008). The many advantages of biodiesel include high cetane number (in the US at P47 while for diesel at P40), dissolved oxygen content (10–12% by weight), sulphur-free, better combustion process and improved emission profile of ex- haust gas (Lapuerta et al., 2009). The biodiesel production is increasing every year and in 2002, Wilson predicted that in the US alone, production will reach 1.3 billion liters annually by 2011 (Wilson, 2002), however this amount in the US and EU were about 1.5 and 5.7 million tonnes in 2007, respectively (Smith et al., 2010), which shows the rate of biodiesel production is far higher than pre- dicted. In 2008, the production of biodiesel was increased by 180% compared to the year 2007 in the EU (Lozada et al., 2010). Any types of feedstock which contains free fatty acids and/or triglycerides such as vegetable oils, waste cooking oil, animal fats, and waste greases can be converted into biodiesel (Janaun and Ellis, 2010). The most common way to produce biodiesel is by transesterification (Wang et al., 2009) which takes place between a vegetable oil and an alcohol (methanol or ethanol) in the pres- ence a catalyst (homogeneous or heterogeneous) or without the application of catalysts as in supercritical fluid method (SCM). Homogeneous catalysts i.e. basic (sodium hydroxide, potassium hydroxide and sodium methylate), and acidic catalysts (sulphuric acid) are necessary to boost the rate of the transesterification reac- tion. The type of homogenous used depends on the free fatty acids (FFA) content of the raw oil (Sharma et al., 2008). Heterogeneous catalysts such as metal oxides or carbonates, sulphonated amor- phous carbon, heteropolyacid solid and biocatalysts (specifically lipases) are commonly used as well. Various biodiesel production methods have disadvantages such as limitation for using unrefined oils as in homogeneous catalyzed process, low rate reaction as in heterogeneous catalyzed process and high pressure and temperature required in SCM method. As a consequence of these disadvantages the production cost increases dramatically. Biocatalysts are also classified as a kind of heteroge- neous catalyst used for biodiesel production through enzymatic transesterification, but the enzymes are expensive and unable to provide the degree of reaction completion required to meet the ASTM fuel specification (Gerpen, 2005). In addition, glycerin as a 0960-8524/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2010.09.094 ⇑ Corresponding author. Tel.: +98 2612703536; fax: +98 2612704539. E-mail address: meisam_tab@yahoo.com (M. Tabatabaei). Bioresource Technology 102 (2011) 461–468 Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech