Urbana, Illinois
July 31, 2008
In the largest field trial of its
kind in the United States, researchers have determined that the
giant perennial grass Miscanthus x giganteus outperforms
current biofuels sources – by a lot. Using Miscanthus as a
feedstock for ethanol production in the U.S. could significantly
reduce the acreage dedicated to biofuels while meeting
government biofuels production goals, the researchers report.
The new findings, from researchers at the
University of Illinois, appear
this month in the journal
Global Change Biology.
Using the grass Miscanthus x giganteus as a feedstock for
ethanol production would significantly reduce the amount of
farmland needed for biofuels, said U. of I. crop sciences
professor Stephen P. Long.
Using corn or switchgrass to produce enough ethanol to offset 20
percent of gasoline use – a current White House goal – would
take 25 percent of current U.S. cropland out of food production,
the researchers report. Getting the same amount of ethanol from
Miscanthus would require only 9.3 percent of current
agricultural acreage.
"What we've found with Miscanthus is that the amount of biomass
generated each year would allow us to produce about 2 1/2 times
the amount of ethanol we can produce per acre of corn," said
crop sciences professor Stephen P. Long, who led the study. Long
is the deputy director of the BP-sponsored Energy Biosciences
Institute, a multi-year, multi-institutional initiative aimed at
finding low-carbon or carbon-neutral alternatives to
petroleum-based fuels. Long is an affiliate of the U. of I.'s
Institute for Genomic Biology. He also is the editor of Global
Change Biology.
In trials across Illinois, switchgrass, a perennial grass which,
like Miscanthus, requires fewer chemical and mechanical inputs
than corn, produced only about as much ethanol feedstock per
acre as corn, Long said.
"It wasn't that we didn't know how to grow switchgrass because
the yields we obtained were actually equal to the best yields
that had been obtained elsewhere with switchgrass," he said.
Corn yields in Illinois are also among the best in the nation.
In field trials in Illinois, researchers grew Miscanthus x
giganteus and switchgrass in adjoining plots. Miscanthus proved
to be at least twice as productive as switchgrass.
"One reason why Miscanthus yields more biomass than corn is that
it produces green leaves about six weeks earlier in the growing
season," Long said. Miscanthus also stays green until late
October in Illinois, while corn leaves wither at the end of
August, he said.
The growing season for switchgrass is comparable to that of
Miscanthus, but it is not nearly as efficient at converting
sunlight to biomass as Miscanthus, Frank Dohleman, a graduate
student and co-author on the study, found.
"One of the criticisms of using any biomass as a biofuel source
is it has been claimed that plants are not very efficient –
about 0.1 percent efficiency of conversion of sunlight into
biomass," Long said. "What we show here is on average Miscanthus
is in fact about 1 percent efficient, so about 1 percent of
sunlight ends up as biomass."
"Keep in mind that when we consider our energy use, a few hours
of solar energy falling on the earth are equal to all the energy
that people use over a whole year, so you don't really need that
high an efficiency to be able to capture that in plant material
and make use of it as a biofuel source," he said.
Field trials also showed that Miscanthus is tolerant of poor
soil quality, Long said.
"Our highest productivity is actually occurring in the south, on
the poorest soils in the state," he said. "So that also shows us
that this type of crop may be very good for marginal land or
land that is not even being used for crop production."
Because Miscanthus is a perennial grass, it also accumulates
much more carbon in the soil than an annual crop such as corn or
soybeans, Long said.
"In the context of global change, that's important because it
means that by producing a biofuel on that land you're taking
carbon out of the atmosphere and putting it into the soil."
Researchers at Illinois are exploring all aspects of biofuels
production, from the development of feedstocks such as
Miscanthus, to planting, harvest, storage, transport, conversion
to biofuels and carbon sequestration.
Corn, switchgrass and Miscanthus are grown side by side in
experimental plots in Urbana, Ill. These fields, shown in 2006,
were in their second year of growth.
Using Miscanthus in an agricultural setting has not been without
its challenges, Long said. Because it is a sterile hybrid, it
must be propagated by planting underground stems, called
rhizomes. This was initially a laborious process, Long said, but
mechanization allows the team to plant about 15 acres a day. In
Europe, where Miscanthus has been grown for more than a decade,
patented farm equipment can plant about 50 acres of Miscanthus
rhizomes a day, he said.
Once established, Miscanthus returns annually without need for
replanting. If harvested in December or January, after nutrients
have returned to the soil, it requires little fertilizer.
This sterile form of Miscanthus has not been found to be
invasive in Europe or the U.S., Long said.
There are at least a dozen companies building or operating
plants in the U.S. to produce ethanol from lignocellulosic
feedstocks, the non-edible parts of plants, and companies are
propagating Miscanthus rhizomes for commercial sale, Long said.
Although research has led to improvements in productivity and
growers are poised to begin using it as a biofuels crop on a
large scale, Miscanthus is in its infancy as an agricultural
product, Long said.
"Keep in mind that this Miscanthus is completely unimproved, so
if we were to do the sorts of things that we've managed to do
with corn, where we've increased its yield threefold over the
last 50 years, then it's not unreal to think that we could use
even less than 10 percent of the available agricultural land,"
Long said. "And if you can actually grow it on non-cropland that
would be even better."
Funding for this research has been provided by a number of
organizations including, the Illinois Council on Food and
Agriculture (C-FAR), the University of Illinois and BP through
the Energy Biosciences Institute. |
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