Ground-level ozone is an important pollutant because it’s an oxidant that affects tissues. It causes damage both to plants and to the human respiratory system. Essentially, ozone reduces the productivity of crops and is potentially fatal in humans.
Professor Nick Hewitt
A modelling case study conducted by researchers at Lancaster University
has revealed that the large-scale production of biofuels in Europe could result in increased human mortality and crop losses. The researchers, whose results have been published online in the journal Nature Climate Change
, point out that many biofuel plant species, including poplar and willow, release more isoprene – an ozone precursor – than the conventional crops that they would replace.
If the European Union (EU)
is to meet its biofuel goals for 2020, large areas of land will need to be converted to grow short-rotation coppice crops. With this in mind, the Lancaster-based team created a model to calculate how such levels of land conversion would impact air quality. The scientists discovered that the rise in ground-level ozone pollution that would result from higher isoprene emissions would likely precipitate increased human mortality and lower crop yields.
To find out more about the potential dangers of large-scale biofuel cultivation, I spoke to Professor Nick Hewitt from the Lancaster Environment Centre (LEC)
. I began by asking how the adverse effects of ground-level ozone pollution tend to manifest themselves.
"Ground-level ozone is an important pollutant because it’s an oxidant that affects tissues," explained Professor Hewitt. "It causes damage both to plants and to the human respiratory system. Essentially, ozone reduces the productivity of crops and is potentially fatal in humans. The World Health Organization (WHO)
estimates that approximately 22,000 Europeans die every year because of ozone pollution."
The rise in mortality that would result from increased biofuel production would be small but significant, according to Professor Hewitt. He and his colleagues estimate that approximately 1,300 additional European deaths – a six per cent rise on the current figure – would result from the increase in cultivation required to meet 2020 biofuel targets. I asked whether these findings imply that biofuel is not
a viable energy solution.
"We are not saying that at all," emphasised Professor Hewitt. "We are simply pointing out that when assessing biofuel cultivation, policymakers must account for detrimental effects to air quality as well as for climate-related benefits. This is not to say that large-scale biofuel production isn’t a viable option. Whether or not it’s viable is a political
decision. I’m not expressing a preference one way or the other. You have to bear in mind that our calculations are based upon large-scale biofuel cultivation; 72,000,000 hectares, which is a lot of land. We chose this figure because it would provide enough biofuel to meet the EU targets for 2020. We are just saying that if this area of land is converted for biofuel cultivation, these are the likely consequences.
"However, there are ways of ameliorating the adverse effects of increased production," he continued. "One method would be to plant the trees in specific areas. If you plant them in areas with low levels of the oxides of nitrogen, for example, they won’t cause ozone formulation. With this in mind, it might be possible to shift production into areas of Europe in which NOx
pollution is lower. Shifting the crops away from populated regions, and areas of intense agricultural pollution, would certainly help the situation. There is also the potential – although I am not advocating this – to use genetically modified trees in which the propensity to emit isoprene has been suppressed. In fact, work is already underway in Germany to engineer a poplar tree that doesn’t produce isoprene."
To conclude our interview, I asked Professor Hewitt about the next steps for his research. He and his colleagues now aim to broaden their project to encompass different crops.
"We want to extend our research to include other biofuels," he explained. "As you’ll appreciate, this is a computer-modelling study based on measurements that we made previously on poplar and willow trees. We now want to look at other potential biofuel crops. Three years ago, we published a paper that came to similar conclusions about the large-scale production of oil palm. Although we didn’t go on to investigate the implications in terms of crop-yield reductions and mortality, we did highlight the ground-level ozone pollution that results from oil palm production in Southeast Asia. Similarly, in terms of Europe, we would like to develop our study to cover other biofuels – not just poplar and willow."