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Ethanol Byproduct Shown to Improve Soil

By Don Comis
September 24, 2004

In the first study of its kind, an Agricultural Research Service scientist has shown that the byproduct of ethanol fermentation from corn stover can increase the structural stability and organic matter content of soil, particularly of highly eroded soil.

"Stover" refers to the plant parts remaining in the field after harvesting corn. The corn stover ethanol byproduct has three times the concentration of nitrogen as the original cornstalks. It consists of stalk parts too tough for digesting by alcohol fermentation microbes and has a compost-like consistency, according to Jane Johnson, a soil scientist with the ARS North Central Soil Conservation Research Laboratory in Morris, Minn.

Applying this byproduct to the land may partially offset the risks associated with harvesting crop biomass for conversion to biofuel. The main risks from harvesting the biomass are possibly increasing soil erosion, as well as depriving the soil of carbon and nutrients it might have derived from the biomass. Another consideration is the safety of applying the fermentation byproduct to farm fields.

In the lab, Johnson applied the byproduct to two types of soil, at three rates, up to the equivalent of six tons of stover an acre. Some of the soil was very rich in organic matter, while some was highly eroded and low in organic matter. Johnson also added chopped cornstalks to some of each soil type and left some untouched, for comparison.

To verify the safety of applying the byproduct of stover fermentation to farm fields, Johnson is growing crops in soil treated with the byproduct, for analysis. Preliminary results have shown no adverse effect to corn or soybeans grown in the presence of the byproduct.

The U.S. Department of Energy (DOE) helped fund this study as part of a complete DOE life-cycle analysis of ethanol production from corn stover that includes comparing possible economical and environmentally sound uses for the byproduct. The work of Johnson and colleagues suggests one use may be as a soil treatment for eroded areas.

A paper on this study has been published in the Soil Science Society of America Journal.

ARS is the U.S. Department of Agriculture's chief scientific research agency.