The Carbon Debts of Land-Use Changes for Biodiesel Production
Achten, W.M.J. and Verchot, L.V. 2011. Implications of biodiesel-induced land-use changes for CO2 emissions: Case studies in tropical America, Africa, and Southeast Asia. Ecology and Society 16: 10.5751/ES-04403-160414.
In doin so the two researchers identified carbon debts ranging from 39 to 1744 Mg CO2/hectare, with oil palm case studies creating the largest debts (473-1744 Mg CO2/hectare), because, as they learned about this crop, "most of the area expansion came at the expense of dense tropical forest." And given numbers such as these, they found that only soybean in certain parts of Brazil needed less than one human generation (30 years) to repay the initial carbon debt, while "highest repayment times were found for Jatropha (76-310 years) and oil palm (59-220 years)."
Achten and Verchot say their findings "raise serious questions about the sustainability of biofuel production," and they say that "due to direct land use change carbon implications following the conversion of (semi-)natural ecosystems with medium to high carbon content, and to indirect land-use changes following conversion of agricultural or pasture land, the potential of biofuels to contribute to climate-change mitigation is questioned."