Title: Environmental, economic, and energetic costs
and benefits of biodiesel and ethanol biofuels
Author(s): Jason Hill et al.
Summary
Negative environmental consequences of fossil fuels and concerns
about
petroleum supplies have spurred the search for renewable
transportation
biofuels. To be a viable alternative, a biofuel
should
provide a net energy gain, have environmental benefits,
be
economically competitive, and be producible in large quantities
without
reducing food supplies. We use these criteria to evaluate,
through
life-cycle accounting, ethanol from corn grain and biodiesel
from
soybeans. Ethanol yields 25% more energy than the energy
invested
in its production, whereas biodiesel yields 93% more.
Compared
with ethanol, biodiesel releases just 1.0%, 8.3%, and
13%
of the agricultural nitrogen, phosphorus, and pesticide
pollutants,
respectively, per net energy gain. Relative to the
fossil
fuels they displace, greenhouse gas emissions are reduced
12%
by the production and combustion of ethanol and 41% by biodiesel.
Biodiesel
also releases less air pollutants per net energy gain
than
ethanol. These advantages of biodiesel over ethanol come
from
lower agricultural inputs and more efficient conversion
of
feedstocks to fuel. Neither biofuel can replace much petroleum
without
impacting food supplies. Even dedicating all U.S. corn
and
soybean production to biofuels would meet only 12% of gasoline
demand
and 6% of diesel demand. Until recent increases in petroleum
prices,
high production costs made biofuels unprofitable without
subsidies.
Biodiesel provides sufficient environmental advantages
to
merit subsidy. Transportation biofuels such as synfuel hydrocarbons
or cellulosic ethanol, if produced from low-input biomass grown
on agriculturally marginal land or from waste biomass, could
provide much greater supplies and environmental benefits than
food-based biofuels.