Soybeans Processing for Biodiesel Production

There is a need for alternative energy sources to petroleum-based fuels due to the depletion of the world’s petroleum reserves, global warming and environmental concerns. Biodiesel is a clean and renewable fuel which is considered to be the best substitution for diesel fuel (Singh & Singh, 2010). Soybean oil is one of the major feedstocks for biodiesel production. According to United States Department of Agriculture (USDA), the U.S. was the largest producer of soybean oil in the world in 2006/2007. The U.S. was followed by Argentina, China, Brazil and India in soybean oil production. The U.S. produced 34.5 % of total soybean oil in the world (United States Department of Agriculture, 2008). This amount of oil is a promising source for biodiesel production from a natural and environmentally friendly agricultural product (Patil & Deng, 2009). Although Food and Agriculture Organization of the United Nation (FAO) stated many environmental problems associated with large scale production of soybeans and maize (FAO, 2009), Life Cycle Assessment (LCA) studies indicated that cultivation of soybeans has less negative impacts on environment than some other oil seeds like sunflower and rapeseed (Sanz Requena et al., 2010). In addition to biodiesel production, soybeans can be used to produce ethanol. Soybean hulls contain significant amount of carbohydrate for ethanol production and producers prefer to use soybean hulls for animal feeding because of its high protein content (Mielenz et al., 2009). Although, biodiesel is usually used as a blend with petro-diesel at varying ratios, it can also be used to fuel compression ignition engines alone. The results of engine emission tests showed that use of biodiesel alone produced less emissions of CO, HC, NOx and smoke than petro-diesel (Qi et al., 2009). Conventional biodiesel production from soybeans uses separate processes for oil extraction and biodiesel conversion. Oil extraction from soybeans is accomplished by using mechanical presses, solvent extraction, supercritical fluid extraction and microwaveand ultrasound-assisted solvent extractions. The extracted oil is degummed and converted to biodiesel via transesterification. Transesterification is a chemical reaction process during which the oil is combined with alcohol, usually ethanol or methanol, in the presence of a catalyst to form fatty esters and glycerol. Reducing biodiesel production costs from $ 3.11 per gallon to below the petro-diesel cost of $3.0 per gallon is important to make biodiesel competitive in the diesel fuel market (Kargbo, 2010). The objective of this chapter is to provide a literature review on oil extraction and biodiesel production from soybeans and to discuss the uses of high intensity ultrasound in processing