Crop residues like wheat straw and corn stover—i.e.
stalks and leaves—have been proposed as a sustainable
feedstock for a “next-generation” cellulosic ethanol industry
in the United States. However, use of agricultural
residues should not be considered to have low environmental
impacts simply because they are a by-product
of an existing use of the land. Such residues currently
replenish and protect soils on working agricultural
lands, and their removal is unlikely to be sustainable
unless accompanied by adoption of agricultural best
management practices such as no-till production, cover
crops, and precision fertilizer management.
- Even moderate corn stover harvest increases erosion and
depletes soil carbon on working lands.
- The increased fertilizer application and increased erosion
associated with harvest of corn stover leads to increased
nutrient losses from the field, which will exacerbate
critical surface and coastal water issues like the Gulf of
Mexico’s “dead zone.”
- A conversion to reduced tillage production can help protect
against soil loss due to erosion, but it is relatively ineffective
at protecting against the depletion of soil carbon.
- Other best management practices such as winter cover
crops are effective at capturing nutrients and replacing
harvested residues as a source of soil enrichment, but are
not widely used by farmers in practice.
- All federal and state policies providing support for biofuel
production (such as the Renewable Fuels Standard
and the Volumetric Ethanol Excise Tax Credit) should
include environmental performance requirements that
ensure the adoption of best management practices to offset
the environmental impacts of feedstock production.
- Federal biomass research programs should be fully
funded. Both USDA and USDOE should invest greater
resources into research on the long-term sustainability
of using biomass and agricultural residues for biofuel
- All projects receiving federal funds to explore crop use
for biofuel production should be required to explicitly
address the soil, water, and greenhouse gas implications
of the new crop varieties or production methods.
- USDA should increase investment in research on
obstacles and opportunities for adoption of agricultural
best management practices, particularly cover crops and
conservation tillage, and support programs and/or policies
to overcome them.
- In federal evaluations of biomass availability, the
criteria for “sustainable” residue supply systems must
be broadened beyond a consideration of erosion to include
other ecosystem services provided by agricultural
land such as soil carbon sequestration and water quality