Petroleum fuels have provided cheap, portable energy. Engines attached to
moving platforms using petroleum fuels have profoundly changed human activities,
increased affluence and promoted population growth. The task of replacing these
optimal fuels is not easy and not cheap. Two reasons for replacing petroleum
Hill et al describe the features desirable in new biofuels: "Negative environmental consequences of fossil fuels and concerns about petroleum supplies have spurred the search for renewable transportation biofuels. To be a viable alternative, a biofuel should provide a net energy gain, have environmental benefits, be economically competitive, and be producible in large quantities without reducing food supplies. We used these criteria to evaluate, through life-cycle accounting, ethanol from corn grain and biodiesel from soybeans. "
Ethanol can be manufactured in a sustained manner from plant carbohydrates and offers similar portability and versatility. Ethanol reduces dependency on oil producing countries. Diluting gasoline with ethanol can improve engine life, reduce nitrogen gas emissions and, in the best case, ethanol could become a cheaper fuel. Ethanol can be produced from any plant fiber (cellulose), given improvements in enzymes and production technology. Novozymes and Genencor announced the development of new enzymes that can reduce the production costs of cellulosic ethanol to less than US$0.13 a liter (a best case scenario). Cellulosic ethanol companies such as Poet, in South Dakota hope to start commercial production with cost of $0.53 per liter. As gasoline prices rise, cheaper ethanol will look more and more attractive.
Biofuels burned in diesel engines have a better environmental profile. Diesel engines can run on a variety light oils including vegetable oils. New sources of biodiesel fuels include non-food plants and algae which can be grown in large fermentation vats. Algae factories and greenhouses could be attached to coal burning electrical generators to use surplus heat and C02 to yield a useful biomass, supplying food and diesel fuel instead of air pollution.
Modified E. coli that convert fatty-acids from plants into diesel was developed by a collaboration of researchers from the U.S. Department of Energy’s Joint BioEnergy Institute (JBEI), from next-gen biofuel company and scientists from UC Berkeley. An industrial process would use the E Coli to make alcohols, waxes, surfactants, solvents and lubricants from non-food plant sources. ( Nature News: Altered microbe makes biofuel. Bacterium could work directly on grass or crop waste. Published online 27 January 2010 | Nature 463, 409 (2010) | doi:10.1038/463409a)
Biofuels cannot replace petroleum without impacting food supplies. Even dedicating all U.S. corn and soybean production to biofuels would meet only 12% of gasoline demand and 6% of diesel demand. Until recent increases in petroleum prices, high production costs made biofuels unprofitable without subsidies. Biodiesel provides sufficient environmental advantages to merit government subsidized research and development.
Compressed natural gas (Methane) is another alternative. The reservoirs of natural gas are greater than oil reserves and, once compressed, the fuel is portable for use in land vehicles and ships, but not aircraft.
See Jason Hill, Erik Nelson, David Tilman*, Stephen Polasky, and Douglas
Tiffany. Environmental, economic, and energetic costs and benefits of biodiesel
and ethanol biofuels. PNAS | July 25, 2006 | vol. 103 | no. 30 | 11206-11210