Policy Research

Water quality impact assessment of large scale biofuel crops expansion in agricultural regions of Michigan

Renee O’Connell

Summary

Bioenergy crops are important for climate-change research as well as domestic energy security. The increase demand for biofuels has pressured farmers to use marginally capable croplands, meaning low levels of soil organic matter, poor soil structure and fertility, and lower yields for traditional crops. Agriculture is responsible for the largest contribution of non-point source pollution to freshwater in the United States, and this article outlines different conditions of biofuel production that minimize negative impacts to water supplies. The Soil and Water Assessment Tool (SWAT) was used to predict the effects of four future land use scenarios and 15 bioenergy crop rotations combined to form 42 total cropping scenarios on sediment, nitrogen, and phosphorus loads in four watersheds in Michigan during a 19 year period. In general, scenarios with perennial grasses, such as switchgrass, miscanthus, and native grasses, had significantly better water quality than scenarios with intensive annual bioenergy crops.

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Policy Implications

The authors recommended not to convert land previously cultivated with “other crops” or marginally capable croplands to any bioenergy rotation in areas with preexisting high nitrogen levels in order to prevent damage to water quality. As policymakers debate the various pros and cons of each source of energy, it is important to minimize environmental impact by understanding how different energy sources and different methods of biofuel production affect soil quality and water supplies. Michigan’s Clean, Renewable, and Efficient Energy Act required 10 percent of the state’s electricity to come from renewable sources by 2015. It is important policymakers understand biofuels can have negative environmental impacts when produced on marginal lands as they push to expand biofuels production.