The use of biofuels produced from food crops as a way of reducing carbon emissions has proved controversial. Critics argue that cultivation of crops for biofuels competes with cultivation of actual food crops. This means either that land is cleared to make way for the biofuel crops (direct land use), or land is cleared elsewhere to make way for the food crops displaced by the biofuel crops (indirect land use). Both of these actions will release stored carbon that will reduce, and potentially nullify, any benefits gained by using biofuels.

Pal Borjesson of Lund University compared the environmental impacts of a range of biofuels, including biogas from sugar beet, maize and waste products such as manure and household waste; biodiesel from rapeseed; and ethanol from wheat, sugar beet and Brazilian sugar cane. He analysed effects such as eutrophication, acidification, energy balance, and emissions from the use of biofuels in light and heavy vehicles, as well as the effects of direct and indirect land use changes.

The results showed that biogas from manure was the most efficient biofuel, producing 140 per cent fewer greenhouse gas emissions than petrol and diesel. Even the worst-performing fuel performed twice as well as the EU directive that states that biofuels should reduce greenhouse gas emissions by at least 35 per cent compared with fossil fuels.

‘In the future, we could see negative indirect land use changes if we increase production of biofuels from food crops very rapidly and significantly,’ Borjesson said. ‘There is a limit, but we are not there yet.’

November 2010