Rapeseed and maize biodiesels were calculated to produce up to 70 per cent and 50 per cent more greenhouse gases respectively than fossil fuels. The concerns were raised over the levels of emissions of nitrous oxide, which is 296 times more powerful as a greenhouse gas than carbon dioxide. Scientists found that the use of biofuels released twice as much as nitrous oxide as previously realised.
The research team found that 3 to 5 per cent of the nitrogen in fertiliser was converted and emitted. In contrast, the figure used by the International Panel on Climate Change, which assesses the extent and impact of man-made global warming, was 2 per cent. The findings illustrated the importance, the researchers said, of ensuring that measures designed to reduce greenhouse-gas emissions are assessed thoroughly before being hailed as a solution.
Professor Smith told Chemistry World: “The significance of it is that the supposed benefits of biofuels are even more disputable than had been thought hitherto.”
It was accepted by the scientists that other factors, such as the use of fossil fuels to produce fertiliser, have yet to be fully analysed for their impact on overall figures. But they concluded that the biofuels “can contribute as much or more to global warming by N2 O emissions than cooling by fossil-fuel savings”.