It's Not Easy Being Green: Ethanol Production Requires Careful Management For Maximum Environmental Benefits

Compared to gasoline, producing and using corn ethanol adds fewer greenhouse gases to the environment. But producing ethanol from corn grain requires careful management for the greatest environmental benefits.

"Biofuels can provide large environmental benefits when compared to gasoline or petroleum diesel," said Bruce Dale, Michigan State University professor of chemical engineering and materials science.

"But if we're going to fully realize the environmental potential of biofuels, we need to plan carefully. For example, producing ethanol from corn grain can release large amounts of nitrous oxide, a greenhouse gas that is 300 times more potent than carbon dioxide, into the environment. It's possible to minimize nitrous oxide emissions and significantly improve the greenhouse gas profile of ethanol, but we need to be aware of and deal squarely with this issue."

Dale, who also is associate director of the MSU Office of Biobased Technologies, is one of seven speakers discussing biofuels and biopower at a symposium, titled "Renewable Energy from Biomass: Technology, Policy, and Sustainability," today at the American Association for the Advancement of Science annual meeting.

An internationally recognized expert on producing ethanol from cellulose, Dale used a powerful agroecosystem model called CENTURY and life cycle analysis to compare and analyze various methods of producing corn for ethanol in 38 counties in eight states.

"Nitrous oxide was by far the dominant greenhouse gas produced, almost all of it generated at the farm level," Dale explained.

Making some modifications to the way corn is grown -- using cover crops, for example -- can reduce the amount of greenhouse gases released. Planting winter cover crops, such as rye grass, reduces nitrous oxide emissions and boosts levels of organic matter in the soil, which makes for more fertile soil.

Harvesting the corn stalks or the cover crop to make cellulosic ethanol also reduces nitrous oxide emissions and reduces overall greenhouse gas levels because the ethanol is used instead of gasoline. But without proper management, harvesting corn stalks also can reduce the amount of organic matter in the soil, which reduces the fertility of the soil over time.

"We need to carefully consider and intelligently manage the entire ethanol production system for long- term sustainability -- not just focus on pieces of the system," Dale said. "Ethanol is and will be a critical part of reducing our national dependence on oil for liquid fuels. Production technology for both corn and cellulosic ethanol is advancing rapidly. So it's essential that we understand how to improve all portions of the system for maximum environmental benefits."

This work is funded by the National Science Foundation, the U.S. Department of Energy, the Michigan Agricultural Experiment Station and DuPont Biobased Materials Inc.

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