Would a wholesale switch from motor gasoline to such alternative fuels as ethanol made from corn, methanol made from natural gas, compressed natural gas (CNG), and liquefied petroleum gases (LPG) yield sharp reductions in transportation-related greenhouse gas emissions?
Not necessarily. A new analysis from the Energy Information Administration considers emissions of six greenhouse gases (water vapor, carbon monoxide, carbon dioxide, methane, nitrous oxides, and nitrogen oxide) produced during the entire production and use cycle for each fuel. When production and distribution emissions are included with tailpipe emissions, and the effects of the differing greenhouse potencies of the gases are taken into account, the four alternative fuels mentioned above show few or no broad advantages over motor gasoline (see figure for a fuel cycle-based comparison of carbon dioxide and water vapor emissions).
Alternatives to Traditional Transportation Fuels, Volume 2: Greenhouse Gas Emissions reveals that alternative fuels differ in their patterns of fuel-cycle greenhouse gas emissions. CNG, for example, produces the lowest emissions of carbon dioxide but the highest emissions of methane. CNG and LPG offer slight improvements over motor gasoline in emissions of carbon monoxide and nitrogen oxides. Ethanol and methanol yield lower emissions of carbon monoxide than motor gasoline but higher emissions of nitrogen oxide.
In appendices, the report discusses the chemistry and physics of global warming, the stability of ozone, fuel combustion chemistry, and greenhouse gas spectral overlaps and their significance.
For more information about this report, contact Velu Senthil, Office of Coal, Nuclear, Electric and Alternate Fuels, Energy Information Administration, at 202-426-1252 or via internet e-mail at vsenthil@eia.doe.gov. To access the report via the internet, go to http://eia.doe.gov and click on Renewables. If you are having technical problems with this site, please contact the EIA Webmaster at wmaster@eia.doe.gov or call 202-586-2753. For general information about energy, contact the National Energy Information Center at 202-586-8800 or via internet e-mail infoctr@eia.doe.gov.
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