CHAPTER 2: LITERATURE REVIEW BIOFUELS Two problems roused the world’s concern in recent years. One is energy crisis caused by the squandring of petroleum fuel. Second problem is environmental problems such as greenhouse effect, global warming, etc. To deal with such problems, renewable sources, utilization technology and bioenergy production technology have been developed. Bioethanol as one of the biofuel can be blended in different proportions in automobiles with gasoline. Biobutanol is also a new biofuel (Liu, Wang, & Zhang, 2009). Production through ABE fermentation of acetone, butanol and ethanol was discovered over 100 years ago. In 1861, Pasteur discovered that anaerobic bacteria could produce butanol. In 1905, Schardinger discovered that anaerobic bacteria could also produce acetone. In 1912, Weizmann isolated the bacterium Clostridium which was producing higher yields of acetone and butanol. Great Britain used this process for the first successful industrial ABE fermentation process in 1916 to produce acetone and methyl ketone (from butanol) to be used in World War I. Industrial ABE fermentation was commercialized for the first time in 1918. In early 1960’s ABE fermentation was suspended because of unfavorable economic conditions due to competition with petrochemical industries. In Russia, South Africa and China, ABE fermentation was carried out during 1980-1990 because of cheap supply of molasses as a substrate and the availability of acetone and butanol from