Using abandoned agricultural lands for biofuel production will meet only a small fraction of global energy needs without compromising food supplies or diminishing biologically-rich habitats, reports a new study published in the journal Environmental Science and Technology.
Using historical land-use data, satellite imaging, and ecosystem models, a team of researchers estimate that 4.7 million square kilometers (1.8 million square miles) of abandoned agricultural lands could be available for producing up to 2.1 billion tons of biomass from energy crops. The biomass would yield an energy content of about 41 exajoules or roughly 7 billion barrels of oil — about 8 percent of current worldwide energy demand or 20 percent of annual oil consumption.
The researchers say that the United States, Brazil, and Australia have the most extensive areas of abandoned crop and pasture lands, but that Africa could see the biggest gains — up to 37 times current energy consumption — from adopting bioenergy production. Nevertheless the research suggests that biofuels are not the panacea that some policymakers had hoped for meeting future global energy demand.
"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," said Elliot Campbell, lead author of the study and a research at the Carnegie Institution's Department of Global Ecology at Stanford University.
"The popular reaction to the recent biofuels papers in Science has been to say that we could still go big with biofuels but along a sustainable path," he told mongabay.com. "The results in this paper warn that this sustainable path leads to a small amount of energy."
"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," added Christopher Field, director of the Department of Global Ecology and a co-author. "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."
