NEVADA, Iowa — One of the first and largest commercial-scale
cellulosic biorefineries in the world will begin producing ethanol later this
The DuPont Cellulosic Ethanol facility is expected to
generate 30 million gallons annually of biofuel produced from corn stover.
Stover is the leaves and stalks left in the field as residue after
To supply the corn stover for its plant, DuPont will
contract from 450 to 600 local farmers to gather, store and deliver more than
375,000 dry tons of stover per year into the Nevada facility.
The stover will be collected from an approximate 35-mile
radius around the new facility and harvested off about 200,000 acres.
The development of this facility has included key
This is the first plant involved in working with the U.S.
Department of Agriculture to promote sustainable harvesting of bio-based
feedstocks for cellulosic-ethanol production.
Research in partnership with Iowa State University’s
BioCentury Research Farm has been vital in the project in looking at production,
harvest and transportation, storage and processing.
DuPont’s efforts began in 2010 with the harvest of corn
stover from 2,000 acres and increased to 60,000 acres — about 550 fields — last
fall, producing more than 170,000 large square bales.
Under the program, farmers enter into an agreement that
allows DuPont to collect the stover in a timely manner after grain harvest.
“The timeline for farmers is critical,” said John Pieper,
DuPont Industrial Biosciences stover feedstock workstream leader, at the
company’s recent media event.
“Farmers are willing to give us access to their fields to
harvest the stover after they’re done harvesting grain, but they don’t want us
taking very long because they have other practices that they need to do in that
field, whether it’s spreading manure, putting on fertilizer or tilling.”
Despite weather challenges last fall and the size of the
acreage, the time demands were met.
Pieper said they were wrapping up moving the bales in
February from the field edges to interim storage facilities.
A major piece of the research is to determine how much
stover should remain on the fields and the amount to be harvested because of its
benefits and limitations.
“However, stover is proportional in yield to grain. So the
amount of stover we needed on top of the soil to protect it from erosion was
sufficient over 40 years ago when we were producing about 100 to 120 bushels of
grain and only about two and one-half ton of stover per acre,” Pieper
“Today we’re producing on these fields in central Iowa over
180 bushels per acre on average, and that means nearly five tons of stover per
“That excess stover is problematic. It interferes with crop
establishment and early growth for the next crop, immobilizes nitrogen and
harbors crop pathogens.”
Benefits include protecting the soil from erosion,
maintaining soil organic matter and cycling crop nutrients.
“When we put that carbon on top of the soil and till it back
under, it does break down into carbon and replaces that soil organic carbon,
which is important,” Pieper said.
“However, to manage those heavy stover yields, we have to do
heavier and heavier tillage. In some parts of Iowa, we’re back to tillage equal
to the moldboard plow.”
The research has included stover’s impact on early crop
development. Two years of data indicate that five days after planting, there are
about 6,000 more plants per acre already emerged in soil where stover was
“Typically in this area, farmers plant between 30,000 and
36,000 plants per acre. So about 20 percent of the plants emerge faster rather
than being delayed, and 30 days post-plant, we have the same population farmers
expect to have emerged,” Pieper said.
DuPont’s system targets stover removal at two tons per acre,
with the remaining 2.3 tons per acre from corn producing 180 bushels per acre
yields left on the field. A shredding windrower spreads remaining stover in a
uniform carpet that covers the field.
A partial stover harvest increased corn yield 93 percent of
the time, with an average gain of 5.2 bushels per acre, according to field
“When you translate that, even at $4 a bushel, that’s $20
revenue per acre for the farmer that goes right toward profit because he hasn’t
had to do anything else to get those extra bushels,” Pieper said.
He estimates farmers will spend $15 per acre to replace
nutrients taken off fields through stover harvest. They receive a $24 per acre
direct payment from DuPont that may go up as much as 40 percent in the coming
Add to that the yield gain from stover management and
farmers are receiving a net profit of $32 per acre when stover is harvested as a
residue management tool.
“In addition to the value of the direct revenue, some can
take advantage of things like eliminating the stalk chopper pass. We’re doing
that for them. We go through with a shredder and leave some on field,” Pieper
“Forty percent of the farmers that participate in the
program either have or indicated they intend to decrease their tillage and
that’s a great thing.
“They know they no longer have to use aggressive tillage
because they don’t have as much stover on the field to manage. If they eliminate
a pass or use a lighter tillage tool, they’re saving money on their operation.”
“They also get to enter the field earlier in the spring.
With fewer residues there to keep the soils cool in the spring, they can get in
and plant earlier.”
He said field-specific soil health assessments are also
conducted as part of the program.