A recent article from the journal, Science, says that the carbon savings offered by low carbon biofuel crops (like corn for ethanol or soya for biodiesel) depend on how the biofuel is produced. Their studies have shown that conversion of “high carbon storage” forests and grasslands for biofuel crop plantations could actually cause a net increase in carbon dioxide emissions, resulting in a “carbon debt”. Estimates show that the conversion of peatlands to palm oil plantations would incur a carbon debt of about 423 years in Malaysia and Indonesia, before the lands could begin to recover and reduce greenhouse gas levels. In South America, the conversion of Amazon rainforest to soya plantations for biodiesel has been estimated to have a carbon debt of 319 years. However, biofuels made from perennials (i.e. grasses) grown in marginal or abandoned agricultural lands would result in “little or no carbon debt”, and could offer “sustained GHG (greenhouse gas) advantages”. Details of their study can be obtained from the Science journal website (URL above)..