May 7, 2009

Growing electricity beats growing fuel

If we're going to power our vehicles with energy from crops, a lifecycle study shows we're better off turning plants into electricity rather than liquid fuel, at least as far as efficiency and climate are concerned.

The study compared bioelectricity and ethanol for distance traveled per unit of cropland and greenhouse gas emissions. It looked at a range of feedstocks, conversion processes and vehicle classes, and considered the lifecycles of the energy and the vehicles. The bioelectricity powered battery electric vehicles and the ethanol fueled internal combustion vehicles. The study used the Energy and Resources Group Biofuel Analysis Meta-Model.

The study found that bioelectricity generated from switchgrass averages 81 percent higher net distance per unit of cropland than ethanol made from switchgrass. Switchgrass bioelectricity also has a 108 percent better average net offset for greenhouse gases than switchgrass ethanol.

Bioelectricity beats ethanol mainly because electric vehicle engines are more efficient than internal combustion engines.

The study didn't weigh water use, air pollution or economic factors. Ethanol's competitiveness depends on the cost of petroleum. Bioelectricity's competitiveness depends on the cost of coal, nuclear, wind, solar and hydro power.

Research paper:
Greater Transportation Energy and GHG Offsets from Bioelectricity Than Ethanol
Science, published online May 7, 2009

Researchers' contact:
J. Elliott Campbell

Related stories and briefs:
Wind powered electric vehicles top study -- related research
Net energy under fire -- related research

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