Clean, green image of biofuels questioned

UK researchers find that crop fuels produce more pollution than the plants they replace.

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The drive to large-scale cultivation of biofuels in Europe has hit a roadblock after UK researchers warned that biofuels could lead to deaths and crop losses. Biofuels, usually derived from specialist crops such as poplar, willow or Eucalyptus, are advocated as part of the solution to society’s reliance on carbon-intensive fossil fuels. However, researchers at the University of Lancaster say that many plant species grown for biofuel emit more of the reactive volatile organic compound isoprene than the traditional crops they replace.

When mixed with other pollutants this can damage human health and reduce crop yields. This is because the isoprene takes part in chemical reactions in the lower atmosphere that lead to the formation of ozone. A modelling case study involving a land area of 72 million hectares converted to short-rotation coppice crops, enough to meet the EU’s 2020 goal for biofuel production, found that biofuels made air pollution worse and caused almost 1 400 deaths a year in Europe.

Trees grown as a biofuel have been seen as a greener alternative to fossil fuels, but the new findings, published in the journal Climate Change, show that the wider implications of biofuel cultivation need to be assessed alongside their potential to save carbon. “Growing biofuels is thought to be a good thing because it reduces the net amount of carbon dioxide emitted to the atmosphere, but biofuels could also have a detrimental effect on air quality,” says project leader Prof Nick Hewitt. “Large-scale production of biofuels in Europe would have a small but significant effect on human mortality and crop yields.”

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Hewitt’s research uses a model of atmospheric chemistry to estimate the changes in ground level ozone concentrations that will result from the large-scale planting of short-rotation coppice biofuel crops. “Our study highlights the need to consider more than simple carbon budgets when considering the cultivation of biofuel feedstock crops for greenhouse gas mitigation,” the report states.