Not long ago biofuels were seen as one of the major tools to combat climate change, but a large number of studies in recent years have shown that many first generation biofuels may have little climate benefit—and some are actually harmful—and are also linked to rising food prices. Now, a new study in Nature Climate Change warns that biofuels using fast-growing trees (polar, willow, and eucalytpus) could also exacerbate ground-level ozone pollution.
“Concerns about climate change and energy security are driving an aggressive expansion of bioenergy crop production and many of these plant species emit more isoprene than the traditional crops they are replacing,” the paper states.
Isoprene is a precursor to ozone, which as a ground-level pollutant is believed to cause many health-problems especially among the vulnerable, including premature death. The compound is produced by a number of species of trees, including those most likely to be grown en masse for bioenergy. The paper estimates that growing trees on 72 million hectares of land in Europe could result in 1,400 premature deaths on the continent annually at a cost of $7.1B. Currently, 22,000 people are estimated to die prematurely from ozone pollution in Europe every year. Ground-level ozone also reduces crop yields.
“The extent to which these crops will be grown is still a subject of much debate. Using all the land available (72 million hectare) must be seen as an extreme case, especially when food security is a priority,” Keith Goulding with Rothamsted Research said in response to the paper.
While planting trees for bioenergy would no doubt lead to an uptick in ozone pollution, it should be noted that burning fossil fuels—coal, oil, and gas—is generally seen as a larger and graver contributor to air pollution than tree plantations.
When asked about how potential isoprene pollution would compare to offsetting burning some fossil fuels, the study’s co-author, Nick Hewitt, told the Guardian, “We’re not in a position to make that comparison.”
The researchers do suggest that ozone pollution could possibly be mitigated through genetic engineering or growing the plantations in areas where the pollution wouldn’t have a significant impact.
In the end, research like this helps experts weigh the best option for biofuels, according to Ottoline Leyser, Director of the Sainsbury Laboratory at Cambridge.
“There are many different biofuel crops, cultivation methods, production and processing systems post-harvest, and different final biofuels. Each one has advantages and disadvantages, which must be compared to the advantages and disadvantages of alternative options,” he notes.
CITATION: K. Ashworth, O.Wild and C. N. Hewitt. Impacts of biofuel cultivation on mortality and
crop yields. Nature Climate Change. 2013.
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