From: Carnegie Institution
Published June 24, 2008 10:29 AM
Abandoned farmlands are key to sustainable bioenergy
Stanford, CA—Biofuels can be a sustainable part of the world's energy
future, especially if bioenergy agriculture is developed on currently
abandoned or degraded agricultural lands, report scientists from the
Carnegie Institution and Stanford University. Using these lands for energy
crops, instead of converting existing croplands or clearing new land, avoids
competition with food production and preserves carbon-storing forests needed
to mitigate climate change. Sustainable bioenergy is likely to satisfy no
more than 10% of the demand in the energy-intensive economies of North
America, Europe, and Asia. But for some developing countries, notably in
Sub-Saharan Africa, the potential exists to supply many times their current
energy needs without compromising food supply or destroying forests.
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Elliot Campbell, Robert Genova, and Christopher Field of the
Carnegie Institution's Department of Global Ecology, with David Lobell
of Stanford University, estimated the global extent of abandoned crop
and pastureland and calculated their potential for sustainable bioenergy
production from historical land-use data, satellite imaging, and
ecosystem models. Agricultural areas that have been converted to urban
areas or have reverted to forests were not included in the assessment.
The results of the study are published in the June 25 online edition of
Environmental Science and Technology. |
The researchers estimate that globally up to 4.7 million square kilometers
(approximately 1.8 million square miles) of abandoned lands could be
available for growing energy crops. The potential yield of this land area,
equivalent to nearly half the land area of the United States (including
Alaska), depends on local soils and climate, as well as on the specific
energy crops and cultivation methods in each region. But the researchers
estimate that the worldwide harvestable dry biomass could amount to as much
as 2.1 billion tons, with a total energy content of about 41 exajoules.
While this is a significant amount of energy (one exajoule is a billion
billion joules, equivalent to about 170 million barrels of oil), at best it
would satisfy only about 8% of worldwide energy demand.
"At the national scale, the bioenergy potential is largest in the United
States, Brazil, and Australia," says lead author Campbell. "These countries
have the most extensive areas of abandoned crop and pasture lands. Eastern
North America has the largest area of abandoned croplands, and the Midwest
has the biggest expanse of abandoned pastureland. Even so, if 100% of these
lands were used for bioenergy, they would still only yield enough for about
6% of our national energy needs."
The study revealed larger opportunities in other parts of the world. In some
African countries, where grassland ecosystems are very productive and
current fossil fuel demand is low, biomass could provide up to 37 times the
energy currently used.
"Our study shows that there is clearly a potential for developing
sustainable bioenergy, and we've been able to identify areas where biomass
can be grown for energy, without endangering food security or making climate
change worse," says Field, director of the Department of Global Ecology.
"But we can't count on bioenergy to be a dominant contributor to the global
energy system over the next few decades. Expanding beyond its sustainable
limits would threaten food security and have serious environmental impacts."
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