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One way to reach the president's objective is
offered by Chris Somerville, professor of biological sciences at
Stanford University and director of the Carnegie Institution's
Department of Plant Biology. Somerville advocates increasing the
production of cellulosic ethanol, which is distilled from the
fermentation of sugars from the entire plant, not just the grains.
''To expand beyond 12 billion gallons, we need to
use the body of the plants rather than use the seeds,'' Somerville
said. He has discuss his research at 8 a.m. Saturday, Feb. 17 (2007),
at the annual meeting of the American Association for the Advancement
of Science in San Francisco.
The ideal plant: A perennial grass
The body of a plant is composed of polysaccharides,
such as cellulose, which can be converted to ethanol by fermentation.
Using the entire plant body as a starting raw material will result in
a higher yield of fermentable sugar per unit of land, Somerville said.
The ideal plant for producing cellulosic ethanol,
he added, is Miscanthus, a perennial grass native to subtropical and
tropical regions of Africa and southern Asia, which is used as an
ornamental plant in the United States.
What makes Miscanthus so special?
''It uses less water per gram of biomass produced
than other plants,'' he said. ''For example, to make a pound of
alfalfa or spinach requires about 600 pounds of water, while to grow a
pound of Miscanthus requires only about 200 pounds of water.''
According to Somerville, Miscanthus produces about
twice as much biomass per acre without irrigation than other grasses,
and reaching the president's target of 35 billion gallons of biofuels
annually would require putting far fewer acres of land into Miscanthus
production.
The main reason behind the call for increased
biofuel production is to reduce emissions of greenhouse gases, not
because we are running out of fossil fuels, he added. ''There are
reserves of coal for 200 years at least, and coal can be liquefied
into fuel, but it produces an awful lot of CO2,'' he
explained.
Biofuels, on the other hand, are carbon-neutral
sources of energy, Somerville said, noting that plants absorb
atmospheric carbon dioxide during photosynthesis, which compensates
for the CO2 that is released when biofuels burn.
Environmental costs
Some environmentalists criticize the use of
biofuels by arguing that planting large quantities of corn or grass to
produce ethanol will require widespread deforestation, which threatens
biodiversity. ''It depends on what acres of land one uses [to plant
Miscanthus],'' said Somerville, who advocates growing biofuel crops on
land currently used for food production.
''There's a lot of deforestation certainly going to
take place in tropical regions, because those countries are going to
develop biofuel businesses,'' he said. ''Already in Malaysia,
Indonesia, the Philippines, the acreage of palm oil is extending very
rapidly because palm oil can be converted to biodiesel with a quite
high efficiency and very low capital investment. But is it worse for
the environment than climate change? That's the question.''
According to Somerville, ''Climate change threatens
biodiversity more than anything that I know. For example, in British
Columbia they are losing each year forests the size of Rhode Island
because of beetle infestation, because it is not cold enough in the
winter to kill the beetles, and they are killing the forest.''
Achievable goals
The president's target of 35 billion gallons of
alternative fuels by 2017 ''is very substantive, but Bush did not
provide any insights into what he is going to do to make that happen,''
Somerville said, adding that it will take seven to 10 years to produce
cellulosic ethanol at competitive prices.
''It is certainly possible to achieve Bush's goals
technically,'' he said. ''The question in my mind is whether investors
are ready to put up the money required to make it happen.'' |
