Cellulosic Ethanol from Wood: Has Its Time Come?
Craig McKinley
Oklahoma State University
Printed in The Cedar Leader Apr-Jun 2008
We are all too familiar with the current cost of petroleum energy.
In the last few months the prices of gasoline, diesel, and other
similar fuels have risen at an astounding rate, and based on media
reports, further increases are forthcoming.
One outfall of the rise in fuel costs has been an increased interest
in using ethanol as either a substitute or additive for gasoline. A
number of service stations in the U. S. currently offer E85 (85%
ethanol, 25 % gasoline) for automotive use, and we can expect more
widespread ethanol availability in the future.
Ethanol is manufactured through the fermentation of sugars by
microbial action (yeasts), followed by distillation and then removal
of water. To date most of the U. S. ethanol production has been by
using corn as the basic feedstock because of the ease with which
corn starch can be converted to sugar then fermented.
A relatively new approach to ethanol production is that of
cellulosic ethanol. This ethanol is produced from plant structural
material, and as the name implies, a majority of this raw material
is comprised of cellulose. Cellulose consists of long chains of
glucose molecules, with glucose being the same sugar that is derived
for fermentation from corn. Thus, ethanol is the same whether from
corn or cellulosic materials. Examples of these cellulosic materials
include switchgrass, straw, barley, and even wood.
Since wood is readily available in many parts of the United States
(to include possibly redcedar in Oklahoma), why has there not been
more emphasis placed on producing ethanol from wood? The answer lies
in the fact that fermenting of sugar from corn is a much easier (and
cheaper) process than removing non-cellulose sugars and lignin from
wood, then fermenting.
The U.S. Department of Energy estimates that it costs almost twice
as much to produce ethanol from cellulosic materials as from corn.
In 2006, the cost of producing cellulosic ethanol was estimated at
$2.25 per gallon. At that price, it would cost about $120 to
substitute for a barrel of oil. That $120 oil price might have
looked unreal in 2006, but today oil has topped $100 per barrel,
with future increases expected. Couple that with recent increases in
corn prices, and previous economic assumptions are becoming rapidly
outdated.
No doubt, wood is also getting a second look. Of the 21 cellulosic
ethanol plants in the United States that are currently either
planned, under construction or in operation, eight are specifically
designated as using wood chips or wood waste as the raw material.
The first of these plants, in Upton, Wyoming, became operational in
February of this year.
With this kind of interest and activity, can red cedar ethanol be
far behind?
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