Jun Sugimori / Yomiuri Shimbun Staff Writer
Producing bioethanol from wood, grass or leaves instead of grain is
gaining increasing attention nationwide, with three projects using the
method under way.
Bioethanol is becoming popular worldwide as an environmentally
friendly fuel with less impact on global warming.
Bioethanol is made from plants that absorb carbon dioxide as they
grow. Burning the biofuel does not increase greenhouse gas CO2 in the
air as absorption and discharge offset each other.
Biofuels can contribute to the prevention of global warming if they
are used instead of fossil fuels. In April, Japan began permitting the
sale of bioethanol mixed into gasoline.
Bioethanol is produced mainly from sugarcane and corn in Brazil and
the United States. But producing biofuel from plants requiring such
intensive farming methods can be wasteful from the standpoint of
energy efficiency.
Increasing bioethanol demand has caused some negative effects, such as
surging prices of corn and other agricultural commodities.
Thus, Japan's attempt to utilize inedible plant matter for bioethanol
production is gaining attention.
The bioethanol production process is basically the same as that of
sake or wine--yeast disintegrates the starch or sugar extracted from
sugarcane.
When wood and grass are used, sugar is made via the disintegration of
cellulose or other fibers. But there is one problem. Yeasts for
brewing sake can't be used because an incompatible type of sugar
molecule containing five carbon atoms is produced as well as that of
the standard six-molecule variety.
A breakthrough was achieved by using a bacteria used in Mexico to
produce tequila from maquey leaves. It is the only species among
yeasts and bacteria used for brewing that can disintegrate sugar
molecule with five carbon atoms.
In the Japanese projects, genes of the bacteria are transplanted into
Bacillus coli and yeasts to also make them capable of disintegrating
sugar molecules with five carbon atoms.
In Sakai, Osaka Prefecture, Bio Ethanol Japan Kansai Co., a company
capitalized by Taisei Corp. and other firms, started full-scale
operations in January to produce biofuel from construction waste.
The company secured operational funding and profitability by
classifying the materials as industrial waste.
The company's plant can annually produce 1,400 kiloliters of
bioethanol from 40,000 to 50,000 tons of discarded wood. First
shipment is scheduled for August.
Mitsui Engineering & Shipbuilding Co. built a demonstration plant in
Okayama Prefecture, in which a special enzyme is used to produce sugar
by disintegrating wood waste.
Wood fibers are extremely hard to disintegrate because they are firmly
connected by the adhesive substance lignin. Using conventional
methods, it was necessary to boil wood waste at high temperature in
solution containing sulfuric acid.
As the enzyme used in Mitsui's method can do the same under much
milder conditions, less energy is needed.
The Research Institute of Innovative Technology for the Earth (RITE)
and Honda Motor Co. jointly started a demonstration experiment in
April that uses straw. The key is the selection of bacteria used for
fermentation.
Conventional yeasts and other bacteria trigger fermentation while
reproducing themselves. But Coryne bacteria, selected by RITE, execute
fermentation without self-reproduction when placed in oxygen-free
conditions.
Regarding the bacteria as delicate living creatures requiring special
care is unnecessary, and fermentation can be made more efficient by
putting a large number of bacteria into containers.
Using the RITE-selected bacteria speeds ethanol production by 10 to 20
times, making it possible to produce 300 grams of ethanol from a
kilogram of straw.
Though the technologies are logical, there are hurdles to
mass-production of ethanol from straw and related material on an
industrial scale.
It would be ideal that such a factory functions stably and predictably
year-round, but it is feared that production can only be conducted in
the autumn harvest season. Supplies of straw are also insufficient as
the commodity is also used in fertilizer production.
Hideaki Yukawa, chief of RITE's microbe study group said, "Practically
speaking, it is best to exclusively use perennial plants to produce
energy resources that require less farming methods."
This fiscal year, the Okayama prefectural government began using a
Mitsui Engineering & Shipbuilding facility to test-cultivate sorghum,
a plant used for biofuel production, and will analyze the crops'
profitablity.
Yukawa emphasized, "Only considering technological successes can't
clear hurdles for bioethanol."
The issue needs to be examined from a wide range of perspectives, such
as the nation's self-reliance in energy resources and how to utilize
abandoned farmlands.
(May. 29, 2007)
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