Can Biofuels Be Sustainable?

Corn stover is made up of the leaves and stalks of corn plants that are left in the field after harvesting the edible corn grain. Corn stover could supply as much as 25% of the biofuel crop needed by 2030.

Scientists with the USDA-ARS Agroecosystem Unit located at the University of Nebraska examined the long-term sustainability of using corn stover as a biofuel crop.

When corn stover is not harvested as a biofuel crop, it can be left on the fields to restore vital nutrients to the soil. Full-scale harvesting of corn stover may deplete the soil.

Researchers measured the soil organic carbon levels and residue production over 14 years in fields planted continuously with corn, continuously with soybeans, and with a rotation of corn and soybeans. Organic carbon rates were found to stay steady or even increase in all three field types.

Gary Varvel and Wally Wilhelm, who conducted the study, said "These results suggest that a portion of corn stover could be harvested for biofuel production without reducing soil organic carbon levels in high yielding systems. However, since this study did not study the direct impact of stover removal, that aspect remains to be evaluated."

Research into the effects of residue removal on soil organic carbon levels in several different cropping systems is ongoing at this and several other USDA-ARS locations throughout the U.S. Much of this research is under the auspices of a multi-location CRIS project within ARS called REAP (Renewable Energy Assessment Project).