EMBARGOED till 0001 GMT on Wednesday 9 January
By Tim Radford
Producing energy for transport and industry from crops may damage human health as well as leaving less land for growing food.
LONDON, 9 January – Biofuels – the green low-carbon alternative to fossil fuels – could both damage human health and reduce crop yields, British scientists warn in the journal Nature Climate Change. They calculate that widespread introduction of plantations of fast-growing trees for ethanol, diesel and methane production could increase concentrations of ground-level ozone, resulting in millions of tonnes in crop losses and an additional 1,385 deaths per year.
The sums are notional, and the research is intended to highlight a hazard and suggest ways of reducing an already low risk. But it is also a reminder that some kind of cost is imposed with every environmental decision.
To reduce carbon emissions and limit global warming, the European Union plans to produce 10% of fuel for transport and for power generation from biofuels by 2020. This could be met, the researchers say, by the conversion of 72 million hectares of farmland or wasteland into short rotation coppice of poplar, willow and eucalyptus.
These trees all produce a volatile organic compound called isoprene: in the presence of oxides of nitrogen from fertilisers and other sources, and in strong sunlight, this can set up a chain of reactions that increase ground level concentrations of ozone.
Ozone is a more complex form of oxygen. While it is an important component of the stratosphere, where it filters out dangerous ultra-violet sunlight, it is an unwelcome component of pollution at street level. This toxic irritant accounts for an estimated 22,000 premature deaths in Europe right now, and the European Commission’s Clean Air for Europe programme has calculated that pollution control legislation, if implemented, could avoid as many as 5,500 deaths per year.
But the widespread plantations of biofuels intended to limit global warming could raise the risk levels once more. The extra isoprene generated by biofuel plantations on such a scale could add another 1,385 deaths and – by affecting wheat and maize yields – cause annual economic losses to cereal farmers of US$1.5 billion.
Nick Hewitt, professor of atmospheric chemistry at Lancaster University, UK, and one of the authors, had been looking at isoprene levels in oil palm plantations in Malaysia: palm oil is used in food and household products and, increasingly, as a biofuel.
“So this got us thinking about what might happen in Europe,” he says. “We wanted to go beyond thinking about the carbon budget, to think about air quality. When people think about biofuel, they think about it in a positive way: these fuels will reduce our emissions and hence will have a benefit for the climate, which may be correct. But there are reservations about that.”
The Lancaster team suggest that the unwelcome consequences could be mitigated by the choice of coppice trees genetically engineered to reduce isoprene emissions – one genetically modified poplar has already been tested under laboratory conditions – or by the choice of other biofuel crops such as grasses, or by shifting biofuel production away from densely populated areas and highly productive cereal land.- Climate News Network