A renewable energy source designed to reduce greenhouse gas emissions is contributing more to global warming than fossil fuels, a study suggests. Measurements of emissions from the burning of biofuels derived from rapeseed and maize have been found to produce more greenhouse gas emissions than they save. Other biofuels, especially those likely to see greater use over the next decade, performed better than fossil fuels but the study raises serious questions about some of the most commonly produced varieties. Rapeseed and maize biodiesels were calculated to produce up to 70 per cent and 50 per cent more greenhouse gases respectively...