NSAC's Blog

Report Highlights Environmental Challenges of Producing Energy from Corn Stover

December 1, 2015

Last month, the Natural Resources Defense Council released a new report, authored by longtime NSAC ally, Loni Kemp, that explores the production of ethanol from corn residues, also known as stover. Stover is the byproduct of harvesting corn kernels, and is made up of stalks, husks, cobs, and leaves. Two energy-production companies opened stover-to-ethanol plants in 2014, and a third company plans to open a plant shortly.

The report is cautiously hopeful about the future of stover-to-ethanol production, but explains that current efforts to reduce the environmental impacts of removing stover from fields fall short. Plant residues protect and enhance natural resources on and around farms, so should only be partially removed, and always in accordance with a conservation plan.

“Corn stover is not ‘waste,'” the report notes in its introductory paragraph. “Some amount of crop residues are essential to return organic matter to farm fields, maintain healthy soils, minimize erosion and water pollution, and sequester carbon.”

Beyond the direct environmental impacts of removing residues from the field, stover-to-energy production has the secondary impact of discouraging diversification into other crops.

“Greater market demand for stover threatens to push higher harvest and ultimately more monoculture corn-on-corn planting,” the report states. “Stover harvest is being promoted by some (DuPont, in particular) as a practice that can solve the challenges of, or even enable, monoculture no-till corn by reducing problems of excess residue.” Fewer rotations and less diversity, however, will increase pest pressures, reduce soil quality, and lead to more erosion and runoff.

The report’s recommendations include:

  • Stover-to-ethanol companies, conservation groups and experts, and farmers should work together to develop best practices for stover removal;
  • Stover-to-ethanol companies should be required to establish sustainability plans for stover harvest to ensure that adequate cover is left on the field (the three companies profiled in the report have criteria to address soil erosion and quality, but not water quality, wildlife habitat, or other resources);
  • Each company must work with USDA’s Natural Resources Conservation Service (NRCS) or a certified conservation planner to develop site-specific conservation plans for every field that is harvested (the report details how DuPont is working with NRCS to do something very similar to this);
  • Each company must work with a third-party verifier to ensure that stover harvests occur in accordance with conservation plans; and
  • Additional federal policies are needed to encourage a transition from corn and stover-based ethanol production to ethanol made from perennial energy crops like grasses and willows.

In recent years, the U.S. Department of Agriculture (USDA) has invested hundreds of millions of dollars to support the production of cellulosic ethanol from corn stover, primarily through the Biomass Crop Assistance Program (BCAP). For many of the reasons outlined above, NSAC has urged USDA to reduce its spending on stover-based ethanol production and instead to focus on the production of ethanol from perennial native grasses and forbs.

You can download the full NRDC report here.


Categories: Conservation, Energy & Environment

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