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CHINA: September 28, 2007
BEIJING - Most crops grown in the United States and Europe to make
"green" transport fuels actually speed up global warming because of
industrial farming methods, says a report by Nobel prize winning chemist
Paul J. Crutzen.
The findings could spell particular concern for alternative fuels
derived from rapeseed, used in Europe, which the study concluded could
produce up to 70 percent more planet-warming greenhouse gases than
conventional diesel.
The study suggested scientists and farmers focused on crops, which
required less intensive farming methods, to produce better benefits for
the environment.
Biofuels are derived from plants which absorb the planet-warming
greenhouse gas carbon dioxide as they grow, and so are meant as a
climate-friendly alternative to fossil fuels.
But the new study shows that some biofuels actually release more
greenhouse gases than they save, because of the fertiliser used in
modern farming practices.
The problem greenhouse gas, nitrous oxide, is more famous as the
dentists' anaesthetic "laughing gas," and is about 300 times more
insulating than the commonest man-made greenhouse gas carbon dioxide.
"The nitrous oxide emission on its own can cancel out the overall
benefit," co-author Professor Keith Smith told Reuters in a phone interview.
The results, published in "Atmospheric Chemistry and Physics
Discussions," were based on the finding that fertiliser use on farms was
responsible for three to five times more such greenhouse gas emissions
than previously thought.
http://www.atmos-chem-phys-discuss.net/7/11191/2007/acpd-7-11191-2007.pdf
They cast further doubts on the credibility of biofuels as a climate
cure, following the revelation of other unintended side effects such as
rainforest clearance and raised food prices, from competition with
forests and food for land. Brazil and the United States produce most of
the world's bioethanol, as a substitute for gasoline, while the European
Union is the main supplier of biodiesel.
"FUTILE EXERCISE"
Using biodiesel derived from rapeseed would produce between 1 and 1.7
times more greenhouse gas than using conventional diesel, the study
estimated.
Biofuels derived from sugar cane, as in Brazil, fared better, producing
between 0.5 and 0.9 times as much greenhouse gases as gasoline, it found.
Maize is the main biofuels feedstock used in the United States, and
produced between 0.9 and 1.5 times the global warming effect of
conventional gasoline, it said.
"As it's used at the moment, bioethanol from maize seems to be a pretty
futile exercise," Smith said.
The study did not account for the extra global warming effect of burning
fossil fuels in biofuel manufacture, or for the planet-cooling effect of
using biofuel by-products as a substitute for coal in electricity
generation.
"Even if somebody decides that our numbers are too big ... if you add
together the undoubted amount of nitrous oxide that is formed, plus the
fossil fuel usage, with most of the biofuels of today you are not going
to get any benefit," Smith said.
However, the study did not condemn all biofuels, suggesting that
scientists and farmers should focus on crops needing little fertiliser,
and harvesting methods that were not energy intensive.
"In future if you use low nitrogen demanding crops, and low impact
agriculture, then we could get a benefit," Smith said.
The study singled out grasses and woody coppice species -- like willows
and poplars -- as crops with potentially more favourable impacts on the
climate. (Additional reporting by Nigel Hunt in London)
Story by Emma Graham-Harrison
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Check for earlier Pacific Biofuel posts: http://pacbiofuel.blogspot.com/
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