|
 orried by rising gas prices? Top off the tank with
paper pulp. Fill 'er up with maple chips. Drive down the freeway
using cheese whey. As average US gasoline prices soar beyond
$1.80 a gallon, proponents of using bio-based fuels and chemicals
are gaining momentum.
 Gasoline-replacement
research in the past has focused on ethanol derived from corn.
But now agricultural engineers are beginning to understand how
biomass waste also can be used as a substitute for petroleum.
Larry Walker, Cornell professor of agricultural and biological
engineering, and his students are using enzymes to break down
solid biomass waste into a renewable energy form.
In a talk
at the American Chemical Society national meeting in March 29
at the Moscone Convention Center, San Francisco, Walker said
there is sufficient biomass waste available to supply all of
the organic chemicals that are consumed annually in the United
States and still have enough waste left over to convert to auto
fuel. "We need renewable resources, and energy flow. How
do we develop alternatives to petroleum-based products? We do
this through plant materials," said Walker. "Bio-based
fuels are recyclable. Fossil-based fuels are not."
Although waste
biomass is a cheaper raw material than oil, there is a catch.
The cost of converting this raw material to energy is the major
constraint to commercialization, according to Walker. The plant
biomass is chemically diverse, and it must be separated then
converted into desired products. The challenge, he explained,
is to develop industries proficient in using this raw material
and to develop more cost-effective enzymatic and microbial processes
that convert these materials into industrial chemicals and energy.
Walker explained
the principles behind biomass fuel: Carbon dioxide is taken in
by the plant through metabolism, and carbon enters plant cells
where it is converted into cell walls. About 279 million metric
tons of plant waste is generated in the United States annually
from industrial, commercial and agricultural production. The
key to using this resource lies in employing enzymes to break
down the woody, fibrous part of the material into fermentable
sugars.
Caroline Corner,
Tina Jeoh and Hyungil Jung, graduate students in agricultural
engineering in Walker's Cornell laboratory, are studying the
use of enzymes from thermophilic (heat-loving) bacteria to break
down the cellulose in plant waste. The bacteria produce six enzymes,
called cellulase, that attack the biomass through a process called
hydrolysis. This allows the enzymes to process the cellulose
into fermentable sugars, permitting scientists to produce fuel
or industrial chemicals. Walker likens the action of the cellulase
enzymes in breaking down the fibrous lignins (the binding in
plants) to a "tag-team Pac Man moving along the cellulose
fiber."
"In essence
we would use plants to make organic compounds - carbon compounds
once made from petroleum, actively taking the carbon dioxide
out of the atmosphere through plant tissue," said Walker.
Not only do
plants represent a renewable source of organic compounds, but
there also is considerable organic waste produced that could
be a carbon source for bio-industries. For example, corn stover
(much of it used as fodder) accounts for 100 million metric tons
of biomass waste produced annually in the United States, and
newsprint biomass waste accounts for 11.2 million metric tons.
Urban tree residue - leaves, Christmas trees and broken branches
accounts for 38 million metric tons.
The research
was funded by the US Department of Agriculture. 
|
cornell.edu