BioFuels Journal

By Susan Reidy, BioFuels Journal editor

A new study shows that soybean-based biodiesel returns 93% more energy than is used to produce it, while corn-based ethanol provides 25% more energy.

The study by University of Minnesota researchers was published online July 11 in the Proceedings of the National Academy of Sciences.

Its purpose, according to post doctoral researcher and lead author Jason Hill, was to compare the renewable fuels options in terms of energy efficiency and cost competitiveness.

�We did the study so we could learn where the differences lie and where we could look for improvements in efficiency,� Hill said.

Study Method

Hill said in determining the energy balances, researchers looked at all the inputs for producing the fuels as well as all the products and coproducts that come out.

The study included inputs such as the energy required to produce the tractors and other equipment used on the farm to produce the corn and soybeans feedstocks and the energy used to build an ethanol or biodiesel facility.

Researchers used the most recent production numbers for corn and soybeans as well as up-to-date costs for items such as fertilizer and pesticides.

Biodiesel has a better energy return, in part, because of the energy savings in growing soybeans vs. corn.

Ethanol production also requires a more intensive conversion process than biodiesel and, therefore, needs more energy.

From an environmental perspective, biodiesel produces 41% less greenhouse gas emissions than diesel fuel, where as ethanol produces 12% less than gasoline.

The Next Step

Although the fuels are energy-positive, neither can do much to meet the U.S. demand for energy, researchers said.

Dedicating all current U.S. corn and soybean production to biofuels only would meet 12% of gasoline demand and 6% of diesel demand.

Researchers suggested looking for methods of producing biomass that require lower inputs as well as examining non-food sources for biofuels production.

�We need to look at biomasses that are dedicated from the beginning for energy rather than taking our existing infrastructure for corn and soybeans and adapting that from food to fuel uses,� Hill said.

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