Growing too much biofuel crops too close to human settlements may put human health at risk as well as jeopardise food production, a new study has found.
According to a team from the University of Lancaster, common biofuel crops such as varieties of poplar, willow or eucalyptus frequently emit higher levels of isoprene, an ozone precursor, than the traditional crops and vegetation they replace.
As a result, concentrations of toxic ozone increase in the areas where the plants are grown, causing irritation of the respiratory system in sensitive individuals as well as possible long-term effects.
In addition to the effects on human health, high levels of ground ozone could also damage food crops.
“Our model results show that the large-scale planting of poplar as a biofuel feedstock in Europe may increase ground-level ozone concentrations across the region,” said Oliver Wild, co-author of the study published in the latest issue of the journal Environmental Science & Technology. “This deterioration in air quality will lead to small but quantifiable impacts on human health and mortality and crop yields, the magnitudes of which will vary with the type of poplar cultivars used and the chosen locations of large plantations.”
The researchers warned that increasing biofuel crop production in order to meet biofuel targets set by the European Union needs to be carefully planned to prevent the negative effects. Especially in the case of poplar, varieties with higher biomass yields emit more isoprene than the lower-yielding ones. The researchers recommend not to plant too much of the high yielding poplar close to inhabited areas.
“In coming years we can anticipate a rapid expansion in poplar plantations in Europe driven by EU carbon-reduction initiatives,” said Professor Nick Hewitt, who led the study. “The current focus in policy-making circles and the biomass industry is on maximising yields, but this should not be the only consideration.”
According to some estimates, long-term exposure to high levels of ground ozone causes 22,000 premature deaths in Europe every year.
As background levels of ground-level ozone across Europe are already high, the study found that even small increases in ozone resulting from the large scale planting of poplar, willow or eucalyptus could result in more widespread problems in the population.
The team therefore suggests creating a European-wide strategy for growing biofuel crops.
“For example, a decision could be made to cultivate poplar on a large scale in areas of Europe with low population density and less intensive agriculture,” said Professor Hewitt.