USDA study boosts fuel
conversion efficiency
rating for ethanol
By Stephen Thompson
Assistant Editor
he viability of ethanol as
an alternative fuel continues
to improve. New
research by USDA economist
Hosein Shapouri
shows a marked improvement in the
energy efficiency of ethanol from five
years ago.
In the July-August 2004 issue of
Rural Cooperatives, we reported that
Shapouri’s research had refuted claims
by ethanol opponents that it costs
more energy to produce ethanol than
it yields. His study showed the net
energy balance of ethanol at 36 percent
in 1996, an improvement
on the 24 percent
figure reported in 1991.
That means that 1.36
BTUs worth of ethanol
requires only one BTU of
energy to produce.
The results of
Shapouri’s latest research,
using data from 2001,
were released in June.
They show an even
greater improvement than
that of the previous fiveyear
period, with ethanol’s
net energy balance growing
to an impressive 67
percent. The continuing
improvement, he says, is
due to technological
advances both in farming
and manufacturing.
"Crop yields per acre have increased,
fertilizer is more energy efficient and
ethanol plants are more efficient," he
says. "So the net energy value of
ethanol improves."
Shapouri’s calculations included the
amount of energy used to grow and
harvest the crop; to transport feedstock,
byproducts and the finished
product; energy used in the production
of seed, pesticides and fertilizer; and
energy consumed in the manufacturing
process.
He is critical of studies that have
disputed the USDA findings, including
one by Dr. David Pimentel, an entomologist,
in 2003. Shapouri says the
Pimentel report is deeply flawed, using
questionable and unsupported information,
especially on energy expenditures
in the production of secondary
inputs, such as farm equipment and the
construction of ethanol plants. "I don’t
know how they come up with these
figures," he says.
Shapouri’s research does not include
such calculations because, he says, the
latest figures on energy costs in those
areas are 25 years old. In any case, he
says available information indicates
that energy used in production of secondary
inputs is much lower. "This
study," says Shapouri, "unlike the
Pimentel report, is based on straightforward
methodology and highly
regarded quality data."
Shapouri believes
that the energy efficiency
of ethanol will
continue to improve,
due to continuing
increases in crop
yields and improvements
in ethanol production
technology.
"Inputs of pesticides
and fertilizers in crop
production are continuing
to fall," he says.
"And in India, a
new molecular filtering
technology is
removing the last bit
of water from ethanol
for a much lower cost
than the process we
currently use."
