Today, there are two different major biofuels for transportation. One substitute for gasoline is ethanol produced from starch and sugar derived from corn, sugar cane, and so on. Another substitute for diesel fuel is BDF (bio-diesel fuel) produced through transesterification of vegetable oils such as rapeseed oil and soybean oil. Conventional biofuels use food crops, threatening food supplies as the world population is rising. In contrast, the second generation biofuels will be produced from non-food feedstocks of lignocellulose and so on, for which a number of conversion processes are under development. On the other hand, butanol as a new biofuel is proposed by BP and DMF (2,5-dimethylfuran) is also developed by the University of Wisconsin-Madison. Boeing is developing a new bio-jet fuel with a heat value similar to conventional jet fuels. This bio-jet fuel is not produced through transesterification, but through hydrotreatment of biomass. Recent trends in conversion technologies and new biofuels are reviewed.
In addition, greenhouse gases from life cycle of bio-fuels as well as current environmental issues are also briefly mentioned.
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