May 7, 2009
Growing electricity beats growing
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
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.
Transportation Energy and GHG Offsets from Bioelectricity Than Ethanol
Science, published online May 7, 2009
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