Researchers: Sorghum holds promise as next-gen ethanol crop
By Kris Bevill | July 09, 2012
First-generation ethanol
producers who are looking for ways to provide advanced biofuels for the U.S.
renewable fuel standard (RFS) may find an easy “in” with
sweet or biomass sorghum, according to a group of scientists from Purdue
University, the University of Nebraska-Lincoln, the University of Illinois and
Cornell University. In a paper published in the scientific journal Biofuels, Bioproducts & Biorefining, titled
“Envisioning the Transition to a Next-Generation Biofuels Industry in the U.S.
Midwest,” the researchers examine how the existing biofuels infrastructure
could be used for second- and third-generation biofuels production and
highlight sorghum as a bioenergy crop that is particularly well suited for use
in existing facilities.
“In the near future, we
need a feedstock that is not corn,” Purdue agronomy professor Cliff Weil said.
“Sweet and biomass sorghum meet all the criteria. They use less nitrogen, grow
well and grow where other things don’t grow.”
Logistical considerations for biomass-to-fuel processes require
further refinement, but Maureen McCann, a Purdue professor of biology and
director of the Energy Center and the Center for Direct Catalytic Conversion of
Biomass to Biofuels, suggests that sorghum could be transported from harvest
locations to collection points such as grain elevators using existing rail
lines. From there, sorghum could be densified before being transported to the
biorefinery for further processing. “Biomass has roughly half of the energy
content of gasoline – even if it’s very compressed and tightly packed,” she
said. “The issue is really how to increase the intrinsic energy density by
preprocessing conversion steps that could be done on farm or at the silo so
that you’re transporting higher-energy products to the refineries.”
The researchers also predict that farmers may be more willing to
grow an annual energy crop such as sorghum rather than a perennial crop. “If
we’re talking about planting switchgrass, that’s a 15-year commitment,” said
Nathan Mosier, a Purdue associate professor of agricultural and biological
engineering. “You can’t switch annually based on the economy or other factors.
You are committed to that crop.”
According to the National Sorghum Producers, a group representing
1,100 sorghum growers, between 5 million and 7 million acres of sorghum are
grown annually in the U.S. About 35 percent of the grain sorghum crop is
currently being used for ethanol production, however the majority of the crop
is used for animal feed. In 2010, the Top 5 sorghum-producing states were
Kansas, Texas, Oklahoma, Colorado and South Dakota, according to the NSP. The
group expects biomass and sweet sorghum acreage to expand most noticeably in
the Southeast region of the U.S. and in South Texas as demand for biofuels
grows. Growers’ main concerns related to sorghum are weed control and lack of a
market, and the United Sorghum Checkoff Program is working to address both
issues through research and market development.
