Policy ForumENERGY

Driving on Biomass

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Science  22 May 2009:
Vol. 324, Issue 5930, pp. 1019-1020
DOI: 10.1126/science.1171740

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The development of the internal combustion engine (ICE) vehicle dramatically influenced American society during the 20th century by providing affordable, reliable transportation. However, the ICE vehicle is an inherently inefficient converter of chemical energy to mechanical power; less than 20% of the energy in gasoline is transformed into mechanical work, and the remainder is lost as heat. With seemingly unlimited supplies of low-cost petroleum in the last century, the poor efficiency of the ICE was initially less important than the power, convenience, and reliability it provided. However, two major factors make it likely that electric vehicles, rather than the ICE, will be the power source of choice for passenger vehicles in the 21st century. First, heightened world petroleum demand coupled with more expensive oil recovery will continue to increase gasoline costs. Second, concerns over the environmental impact of CO2 production are leading toward carbon taxes, cap-and-trade limits, and other strategies that will impact the ICE.