Using crops for motor fuel was supposed to reduce carbon dioxide emissions, but a new study has found it has exactly the opposite effect. Burning biofuels may release less carbon dioxide than burning fossil fuels, but the rising demand for biofuel—driven by government mandates and subsidies—has induced farmers to clear land to grow the crops needed for biofuel. These land-use changes increase carbon dioxide emissions by an amount that far outweighs the reduction in emissions from burning biofuels instead of fossil fuels, according to a new study commissioned by the British government and leaked to the Times. The study finds that using palm oil for fuel actually increases carbon dioxide emissions by 31 percent compared to using fossil fuels. The Times reports:

It takes up to 840 years for a palm oil plantation to soak up the carbon emitted when the rainforest it replaced was burnt. The expansion of the palm oil industry in Indonesia has turned it into the third-largest CO2 emitter, after China and the US. Indonesia loses an area of forest the size of Wales every year and the orang-utan is on the brink of extinction in Sumatra.

Biofuel from rapeseed and soy also increases carbon emissions compared to fossil fuels, according to the study, which was performed by the consultancy E4tech.

You’d think the British government might have looked at this question before requiring that 3.25 percent of all fuel sold come from crops—a requirement set to rise to 13 percent by 2020. The U.S. government, by the way, has similar biofuel mandates, and Europe as a whole gives  £3 billion in subsidies to the biofuel industry.