Crop residues, perennial warm season grasses, and short-rotation woody crops are potential biomass sources for cellulosic ethanol production. While most research is focused on the conversion of cellulosic feeedstocks into ethanol and increasing production of biomass, the impacts of growing energy crops and the removal of crop residue on soil and environmental quality have received less attention. Moreover, effects of crop residue removal on soil and environmental quality have not been compared against those of dedicated energy crops.
In the March-April 2010 issue of Agronomy Journal, published by the American Society of Agronomy, Dr. Humberto Blanco reviewed the impacts of crop residue removal, warm season grasses, and short-rotation woody crops on critical soil properties, carbon sequestration, and water quality as well as the performance of energy crops in marginal lands. The review found that crop residue removal from corn, wheat,and grain sorghumcan adversely impact soil and environmental quality. Removal of more than 50% of crop residue can have negative consequences for soil structure, reduce soil organic carbon sequestration, increase water erosion, and reduce nutrient cycling and crop production, particularly in erodible and sloping soils.
“Crop residue removal can make no-till soils a source rather than a sink of atmospheric carbon,” says Blanco, even at rates lower than 50%. Residue removal at rates of less than 25% can cause loss of sediment in runoff relative to soils without residue removal. To avoid the negative impacts on soil, perhaps only a small fraction of residue might be available for removal. This small amount of crop residues is not economically feasible nor logistically possible. Blanco recomends developing other alternative biomass feedstock sources for cellulosic ethanol production.