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THE experiment by three researchers at the Ateneo de Manila
University has deepened our understanding of the sequence of
biochemical reactions that lead to the production of ethanol.
On May 20, 2008, Crisanto Lopez, the team’s
adviser, told The Manila Times that the extraction of ethanol from
rice straws solves the food versus biofuel conundrum.
Miguel Angelo Vicente, Dulce Marie Romea and
Jose Maria Villamor used three microorganisms to break down the
lignin, to produce cellulase and to ferment it into ethanol.
“The results,” they said, “were compared
to the results of a control set-up which simulated the procedure . .
. in industrial ethanol production.”
Their paper has still to be published in a
refereed journal.
To put their achievement in perspective, I’ll
recount the state of play in the highly contentious field of
bioenergy research.
Extracting structural sugars from cellulose was
first bruited in the late 1970s, at about the same time that Brazil
began making sugarcane ethanol. By 2006, the price of Brazilian
ethanol was $0.81 per gallon, making it competitive with gasoline.
As the price of crude oil goes up the search for
alternative fuels also intensifies. Investments by governments and
private companies in biomass energy research have increased very
substantially since the ’70s. For example, the European Union has
set aside $1.5 billion over seven years for research and development
(R&D) in renewable energy. In the US, the Advanced Research
Project Agency will spend $1 billion over five years for R&D in
bioenergy. British Petroleum has given the University of California
in Berkeley $500 million for biofuel research over 10 years. Other
corporations have made similar grants to other universities.
A key problem in the extraction of ethanol from
plant cellulose is a cost-effective method of separating the lignin
that’s entangled with the cellulose.
There are several ways of doing it but I’ll
summarize only the prototypical method.
The biomass is treated with saturated steam at
200 degrees Celsius and ammonia, then cooked in a dilute acid. The
lignin is exposed to cellulolytic enzymes that digest the cellulosic
components to release six- and five-carbon sugars by hydrolysis.
These are fermented by ethanol-producing microorganisms in a single
process called simultaneous saccharification fermentation (SSF) that
combines hydrolysis and fermentation. The purpose is to break up the
complex carbohydrates into monosaccharides and to convert the
carbohydrate to carbon dioxide and alcohol. This also prevents the
hydrolytic enzymes from being inhibited by the reaction products.
SSF typically lasts 3 to 6 days. The product is a thin ethanol of 4
percent to 4.5 percent that still needs to be distilled. (Gregory
Stephano-poulos, Science, Feb. 9, 2007)
This process is much too slow and difficult to
scale up economically for industrial production.
Researchers have taken three tacks to solve
these problems.
The first is to find a way of reducing the costs
of cellulolytic enzymes in order to make the final product
competitive with corn ethanol.
The second is to modify genetically the plants
that will be used as feedstock so that the lignin-cellulose
entanglement is easier to break apart. The yeasts that will be used
for fermentation are bioengineered to make them resistant to the
toxic compounds of ethanol.
And the third is to design microorganisms that
can produce hydrocarbons efficiently. Synthetic biology is the
cutting-edge of bioenergy research.
Experts estimate that it may take 10 to 15 years
before cellulosic ethanol becomes available at the pump. With crude
oil prices expected to rise to $200 per barrel, the pressure—and
incentives—to produce biofuels become more urgent with each
passing day for both political and economic reasons.
Ethanol, it must be said, compares poorly to
gasoline as it delivers 30-percent less energy by volume. In
addition, ethanol is hard to transport by truck or by pipeline
because it exudes water vapor. And it is corrosive.
Another fuel that can be produced from
cellulosic biomass is butanol. It is better than ethanol because it
is less corrosive, less volatile, denser and easier to produce.
There are others: alcohols, alkanes and oils can
be derived biochemically from biomass.
Which of these will become the transportation
biofuel of the future depends on the interplay of science,
technology and economics.
It would be desirable for the Department of
Energy and the Department of Science and Technology to encourage
Ateneo and other universities to expand or start R&D in biofuels.
And these two agencies should undertake a parallel research program
on jatropha. One of the byproducts of biodiesel production is
glycerol, which can be converted into hydrogen and methane to drive
an electric generator.
Biofuels are the future and we should not miss
out on them.
opinion@manilatimes.net
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