Sweet and biomass sorghum would meet the need for
next-generation biofuels to be environmentally sustainable, easily adopted by
producers, and take advantage of existing agricultural infrastructure, a group
of researchers led by Purdue University scientists believes.

The scientists from Purdue, the University
of Nebraska-Lincoln, University of Illinois,
and Cornell University believe sorghum, a grain crop
similar to corn, could benefit from the rail system, grain elevators, and corn
ethanol processing facilities already in place. Their perspective article is
published online in Biofuels, Bioproducts
& Biorefining.

“The Midwest is
uniquely poised to get the biorefining industry going on cellulose,” said
Nick Carpita, a Purdue professor of botany and plant pathology. “As we
move to different fuels beyond ethanol, the ethanol plants of today are
equipped to take advantage of new bioenergy crops.”

The scientists argue that no single plant is a
silver-bullet answer to biofuels, but sorghum should be a larger part of the
conversation than it is today. Cliff Weil, a Purdue professor of agronomy, said
some types of sorghum would require fewer inputs and could be grown on marginal
lands.

“In the near future, we need a feedstock that is not
corn,” Weil said. “Sweet and biomass sorghum meet all the criteria.
They use less nitrogen, grow well and grow where other things don’t grow.”

The ability to minimize inputs such as nitrogen could be a
key to sorghum’s benefits as a bioenergy crop. Carpita said corn, which has
been bred to produce a maximum amount of seed, requires a lot of nitrogen. But
sorghum could be genetically developed in a way that maximizes cellulose,
minimizes seeds and, therefore, minimizes inputs.

“If you’re just producing biomass and not seed, you
don’t need as much nitrogen,” Carpita said.

Farmers may also be more willing to grow sorghum—a crop
they’re familiar with—because it is an annual, compared with perennials such as
switchgrass or Miscanthus, that would take up a field for a decade or longer.
Sorghum would fit in a normal crop rotation with food crops rather than tying
up valuable cropland.

“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.”

Conversion processes for turning biomass into fuel need to
be scalable and take advantage of existing infrastructure for grain production,
said Maureen McCann, a Purdue professor of biology and director of the Energy
Center and the Center for Direct Catalytic Conversion of Biomass to Biofuels.
Sorghum could be harvested and transported using existing rail lines to
collection points such as grain elevators, where the crop could be processed to
a higher-value, more energy-dense product before being transported for further
processing in a refinery.

“Biomass has roughly half the energy content of
gasoline – even if it’s very compressed and tightly packed. 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,” McCann said.

Farzad Taheripour, a Purdue research assistant professor
of agricultural economics, said bringing sorghum back as a biofuel crop could
have an economic impact on poorer rural areas of the country.

“Given that sorghum can be produced on low-quality,
marginal lands in dry areas, producing sorghum for biofuel will significantly
improve the economy of rural areas that rely on low-productivity
agriculture,” Taheripour said. “This could improve welfare in less-developed
rural areas and increase job opportunities in these areas.”

Purdue Agriculture researchers are continuing to look at
how bioenergy crops could be deployed into the agricultural landscape. Work in
the Center for Direct Catalytic Conversion of Biomass to Biofuels continues to
develop a knowledge base for chemical and thermal conversion technologies that
might be able to take advantage of the Midwest’s
transportation infrastructure.

Source: Purdue University