It sounds counterintuitive, but burning oil and planting forests to
compensate is more environmentally friendly than burning biofuel. So say
scientists who have calculated the difference in net emissions between
using land to produce biofuel and the alternative: fuelling cars with
gasoline and replanting forests on the land instead.
They recommend governments steer away from biofuel and focus on
reforestation and maximising the efficiency of fossil fuels instead.
The reason is that producing biofuel is not a "green process". It
requires tractors and fertilisers and land, all of which means burning
fossil fuels to make "green" fuel. In the case of bioethanol produced
from corn – an alternative to oil – "it's essentially a zero-sums game,"
says Ghislaine Kieffer, programme manager for Latin America at the
International Energy Agency in Paris, France (see Complete carbon
footprint of biofuel - or is it?).
What is more, environmentalists have expressed concerns that the growing
political backing that biofuel is enjoying will mean forests will be
chopped down to make room for biofuel crops such as maize and sugarcane.
"When you do this, you immediately release between 100 and 200 tonnes of
carbon [per hectare]," says Renton Righelato of the World Land Trust,
UK, a conservation agency that seeks to preserve rainforests.
Righelato and Dominick Spracklen of the University of Leeds, UK,
calculated how long it would take to compensate for those initial
emissions by burning biofuel instead of gasoline. The answer is between
50 and 100 years. "We cannot afford that, in terms of climate change,"
The researchers also compared how much carbon would be stored by
replanting forests with how much is saved by burning biofuel grown on
the land instead of gasoline.
They found that reforestation would sequester between two and nine times
as much carbon over 30 years than would be saved by burning biofuels
instead of gasoline (see bar chart, right). "You get far more carbon
sequestered by planting forests than you avoid emissions by producing
biofuels on the same land," says Righelato.
He and Spracklen conclude that if the point of biofuels policies is to
limit global warming, "policy makers may be better advised in the short
term to focus on increasing the efficiency of fossil fuel use, to
conserve existing forests and savannahs, and to restore natural forest
and grassland habitats on cropland that is not needed for food."
They do admit, however, that biofuels made from woody materials such as
prairie grasses may have an advantage over reforestation – although it
is difficult to say for now as such fuels are still in development (see
Humble grasses may be the best source of biofuel).
Forests at high latitudes have been found to sequester less carbon than
tropical forests (see Some forests may speed global warming). But
Righelato says this does not affect his calculations as biofuel crops
are not, by and large, grown in these areas.
Journal reference: Science (DOI:10.1126/science.1141361)
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Check for earlier Pacific Biofuel posts: http://pacbiofuel.blogspot.com/