Robin L. Graham talks with
ScienceWatch.com and answers a few questions about
this month's New Hot Paper in the field of Agricultural
Sciences. The author has also sent along images of
Article Title: Current and potential US corn stover
RL;Nelson, R;Sheehan, J;Perlack, RD;Wright,
Journal: AGRON J
Year: JAN-FEB 2007
* Oak Ridge Natl Lab, Div Environm Sci, POB 2008, Oak
Ridge, TN 37831 USA.
* Oak Ridge Natl Lab, Div Environm Sci, Oak Ridge, TN 37831
(addresses have been truncated)
Why do you think your paper is highly
There has been an astounding increase in interest in bioenergy and
especially biofuels over the past three years. The public, decision makers,
and researchers want to know about biofuel feedstocks other than just corn
grain. Cellulosic feedstocks such as corn stover are considered to be very
important future feedstocks but there hasn’t been much published
research on their supply potential in a way that is quantitative or takes
into account environmental constraints to their production or collection.
Our paper addressed the most readily available near–term source of
cellulosic feedstock in the US—corn stover. The weight of a corn
plant is half corn grain, half corn stover. Thus the US produces as much
corn stover as corn grain and corn production occupies more agricultural
land than any other crop and has for decades. We quantified the potential
supply (cost and quantity) of this feedstock and we incorporated
environmental and economic analysis into our assessment. We considered the
range of soils and management approaches that are currently used to produce
Does it describe a new discovery, methodology, or
synthesis of knowledge?
Our paper is a new rigorous assessment of an important potential supply of
biomass which could be used to provide ethanol or other biofuels. We
included economic, agronomic, and environmental considerations in a
Would you summarize the significance of your paper
in layman's terms?
If the US is to use biofuels to increase energy independence, corn stover
(the remains of the corn plant after the grain is collected—i.e.,
stalk, leaves, cob) is an important potential source of biomass for those
fuels. In growing corn for grain we produce millions of tons of corn stover
every year. But leaving corn stover in the field is very important for
reducing soil erosion and conserving soil carbon so we can't remove all the
stover that is produced. Maintaining soil carbon and avoiding excessive
erosion are important for maintaining the productivity of soils.
Taking into account the various soil types and corn crop management
practices, we calculated at a county level how much stover could be
collected in the US and still not cause serious erosion problems. The
analysis was challenging because erosion is a function of weather, soil
type, and how the crop is managed. We did not analyze how much stover
should be left in the field to maintain soil carbon.
produces as much corn stover as
corn grain and corn production
occupies more agricultural land
than any other crop and has for
We also calculated the cost of collecting that stover into bales and found
that most stover could be collected at a cost between $30 and $35 per dry
baled ton. In our analysis we showed that if all corn crops were grown
without tilling the soil we could collect almost twice as much corn stover
without causing harmful levels of erosion.
Farmers can grow corn without tilling the soil and many do. If all corn was
produced without tillage we could collect enough stover from our current
corn crops to produce approximately eight billion gallons of ethanol.
Currently in the US we produce six to seven billion gallons of ethanol
annually from corn grain.
How did you become involved in this research, and
were there any problems along the way?
I am a systems ecologist interested in applied environmental problems. I
would like to solve our energy challenges, but in a way that sustains the
environment. It was challenging to model soil erosion as a function of
stover removal across the thousands of soils on which corn is currently
grown in the US and to marry economic, agronomic, and environmental
We would have liked to have quantitatively assessed the amount of corn
stover that needed to remain in the field to preserve soil carbon but that
is an even more complex problem and there were no soil carbon models we
could easily adapt to assess the thousands of soil and corn crop management
conditions that exist in the US.
Where do you see your research leading in the
We would like continue the collaborations of ecologists, agronomists,
agricultural engineers and economists working to discover ways to produce
biomass feedstocks that are truly sustainable in an environmental, social,
and economic sense. While we addressed erosion in this study in the context
of corn stover removal for bioenergy, we are now researching soil carbon
and water quality effects associated with the production of energy crops,
specifically switchgrass. We are also expanding from a US-centric
perspective to a global perspective.
Do you foresee any social or political implications
for your research?
If bioenergy is to be a useful technology it has to be environmentally,
economically, and socially sustainable. Rigorous, transparent,
peer–reviewable research that explores the intersection of all these
elements is very important to developing a technology that truly meets the
needs of the US. Our research points to the need to explore multiple
cellulosic feedstocks and to tailor those feedstocks and their management
to site-specific conditions. There will not be one feedstock that fits all
Robin L. Graham, Ph.D.
Groupleader, Energy & Environmental Systems Science
Environmental Sciences Division
Oak Ridge National Laboratory
Oak Ridge, TN, USA