Driving on biomass

Science 22 May 2009:
Vol. 324. no. 5930, pp. 1019 - 1020
DOI: 10.1126/science.1171740


Policy Forum

Energy:
Driving on Biomass

John Ohlrogge,1,* Doug Allen,1 Bill Berguson,2 Dean DellaPenna,3 Yair Shachar-Hill,1 Sten Stymne4

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.

http://www.sciencemag.org/cgi/content/summary/324/5930/1019

Originally published in Science Express on 7 May 2009
Science 22 May 2009:
Vol. 324. no. 5930, pp. 1055 - 1057
DOI: 10.1126/science.1168885

Prev | Table of Contents | Next
Reports
Greater Transportation Energy and GHG Offsets from Bioelectricity Than Ethanol
J. E. Campbell,1,2,* D. B. Lobell,3 C. B. Field4

The quantity of land available to grow biofuel crops without affecting food prices or greenhouse gas (GHG) emissions from land conversion is limited. Therefore, bioenergy should maximize land-use efficiency when addressing transportation and climate change goals.

Biomass could power either internal combustion or electric vehicles, but the relative land-use efficiency of these two energy pathways is not well quantified.

Here, we show that bioelectricity outperforms ethanol across a range of feedstocks, conversion technologies, and vehicle classes. Bioelectricity produces an average of 81% more transportation kilometers and 108% more emissions offsets per unit area of cropland than does cellulosic ethanol. These results suggest that alternative bioenergy pathways have large differences in how efficiently they use the available land to achieve transportation and climate goals.
http://www.sciencemag.org/cgi/content/full/324/5930/1055