Biofuel Crops Cultivation and Isoprene
A study on the correlation between biofuel crops cultivation and atmospheric isoprene concentration was published in Nature Climate Change in January, 2013. The research was carried out by Professor Nick Hewitt and his coworkers, from the Lancaster Environment Centre of Lancaster University (UK).
The group performed this analysis because in the European Union area there is an increasing cultivation of biofuel crops. Indeed, these crops can be a valuable energy source, as they are renewable; moreover, by planting more crops, the countries can offset carbon dioxide (CO2) emissions.
Recent studies, however, showed that this is not always the case and that biomass use to reduce CO2 emissions is a topic which is more complex than originally thought.
Biofuel and Emissions: The Study
Professor Hewitt and coworkers considered the effects expected if 72 million hectares (Mha) of land across Europe were converted to biofuel crops cultivation from previous different uses (i.e. other crops, grassland and wasteland). This value was chosen as 72 Mha were identified as potentially suitable sites for this type of cultivation.
They assumed all this land would be used to cultivate short rotation coppice (SRC).
The researchers evaluated the consequence of this increased biomass cultivation on the ground level ozone concentration (linked to isoprene emission); moreover, they also studied the effects that ozone would have on the human mortality and the yield of food crops.
Increased Emissions: The Results
The modeling study showed that the increase in SRC cultivation would lead to a substantial increase in isoprene emission (from 11.5 to 16.0 TgC/year, TgC = teragrams of carbon); this would correspond to an average higher ozone concentration of 0.8 ppbv (part per billion per volume).
Although this may seem a small amount, the negative effects could be significant.
According to the model, in fact, this could cause an annual 6% increase in the number of premature deaths (data calculated with a 95% confidence interval), and an estimated cost of about US $ 7.1 billion.
The consequences on the agriculture would also be noticeable, as the losses in the yields of wheat and maize were estimated to be 3.5% and 1% respectively; this would represent a 50% increase in the ozone-related yield losses currently observed.
Dangers of Increasing Biofuel Production
These data show that several parameters have to be considered in biomass evaluation. According to professor Hewitt: “our study shows the need for high-resolution site-specific impact assessment of future biofuel cultivation, which takes into account air quality as well as carbon budget.”
Possible solutions to minimize these problems could be the use of SRC with lower isoprene emissions, or shifting SRC production into more appropriate areas (away from populated areas or from areas with intense food crops cultivation).
Ashworth K, et al. Impacts of biofuel cultivation on mortality and crop yields. (2013) Nature Climate Change, doi:10.1038/nclimate1788.
Amman M., et al. Baseline Scenarios for the Clean Air for Europe (CAFÉ) Programme. Accessed January 2013.
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