The use of biofuels could sharply increase greenhouse-gas emissions by driving the conversion of native land to agriculture, according to research published online last week in Science.
Timothy Searchinger from Princeton University in New Jersey and his colleagues suggest that it takes 167 years for the emissions reductions gained by burning corn ethanol to make up for the sharp spike in emissions caused by clearing new land for farms (T. Searchinger et al. Science doi:10.1126/science.115861; 2008).
And a second study, led by Joseph Fargione of the Nature Conservancy in Minneapolis, Minnesota, calculates that the time needed to clear this 'carbon debt' would vary from 17 to 420 years, depending on the circumstances. J. Fargione et al. Science doi:10.1126/science.1152747; 2008).
But biofuels made from waste biomass, or perennial crops grown on abandoned agricultural lands, offer “immediate and sustained greenhouse-gas advantages”, according to Fargione's team.