Biodiesel Production and Quality

Abstract

Fossil fuels are, nowadays, the most used worldwide but that are some problems involving their utilization. First of all, the price, which is growing often and makes petroleum no longer economically sustainable. Second, during the burning of petrochemical sources there is emission of very dangerous pollutants for human health, like carbon dioxide that is the main reason of the global warming. In addition, fossil fuels are non-renewable resources, so they will last for a limited period of time. For all these reasons, vegetable oils are emerging as a great alternative fuel, because of their renewable nature and environmental benefits (Ferella et al., 2010). Despite all the advantages, the use of vegetable oils as fuel has some disadvantages. The direct use in internal combustion engines is problematic because vegetables oils have high viscosity than diesel fuel and low volatility, so they do not burn completely and form deposits in the fuel injectors of diesel engine. According to specialized literature there are five ways to reduce the problems mentioned above: blending of vegetable oil and diesel, thermal cracking (pyrolysis), microemulsions, esterification and transesterification (Ma & Hanna, 1999). Esterification and transesterification reactions are currently the most favored reaction pathways to produce biodiesel (Janaun & Ellis, 2010). Biodiesel, defined as the simple alkyl monoesters of long chain fatty acids derived from renewable feedstocks, is the most suitable substitute to diesel. For this reason the research on this biofuel are steadily growing all over the planet. In Brazil, the focus of research is the production of biodiesel using ethanol, since this alcohol is produced on a large scale in the country. Ethanolysis produces a biodiesel less damage to the environment than that produced by methyl alcohol, since ethanol is derived from sugar cane or corn. In the rest of the world, the production takes place mostly in the methyl route and with use of heterogeneous catalysts (Pighinelli, 2010). Biodiesel is highly biodegradable in fresh water as well as in soil and great part of it is mineralized in until 28 days under aerobic or anaerobic conditions (Makareviciene & Janulis, 2003; Pasqualino et al., 2006; Zhang et al., 1998). It is also a carbon-free fuel, as the plants that serve as raw material for its production absorb more carbon than that which is released during the burning of this biofuel (Antolin et al., 2002; Lang et al., 2001; Sharma et al., 2008; Vicente & Martinez, 2004). Moreover, when biodiesel is burned in diesel engines the emissions of hydrocarbons, carbon monoxide, particulate matter and sulphur dioxide are reduced with the exception of