Sorghum meets biofuel needs

June 22, 2012 – 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 early online in the
journal 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.