Hewitt et al. (2009) examined the effect of converting rainforests to oil palm plantations in Malaysia. The production of palm oil has increased, partially due to the fact that the biofuel has been touted as “environmentally-friendly.” However, using various measurements and models, the researchers discovered that oil palm plantations actually emit a far greater amount of nitrous oxides and volatile organic compounds (VOCs) than rainforests. This is especially problematic as nitrous oxides and VOCs can react in the presence of sunlight to create O3, which is classified as an air pollutant with the potential to seriously damage human health, among other things. Should nitrous oxides in Malaysia reach levels comparable to those over rural North America and Europe, it is likely that O3 levels could reach over 100 ppbv, well above the level known to be dangerous to human health. Thus, the authors concluded that nitrogen emission management schemes must be developed. — Christina Mainero
Hewitt, C., MacKenzie, A., DiCarlo, P., Di Marco, C., Dorsey, J., Evans, M., Fowler, D., Gallagher, M., Hopkins. J., Jones, C., Langford, B., Lee, J., Lewis, A., Lim, S. McQuaid, J.. Misztal, P., Moller, S., Monks, P., Nemitz, E., Oram, D., Owen, S., Phillips, G., Pugh, T., Pyle, J., Reeves, C., Ryder, J., Slong, J., Skiba, U., and Stewart, D., 2009. Nitrogen management is essential to prevent tropical oil palm plantations from causing ground-level ozone pollution. PNAS 106, 18447–18451.
In their investigation, Hewitt et al. took fully integrated and comprehensive biosphere-to-atmosphere flux measurements and modeled the atmospheric chemistry of rainforests and oil palm plantations in the tropics. They determined that VOC emissions from both types of land tend to be dominated by isoprene, though the plantations emit five times as much of it as the rainforests, evidently because of biogenic emissions from oil palm trees. The researchers suggested that the emissions of VOC compounds from the oil palm plantations were greater than those of European cities, such as London. Moreover, their measurements suggested that oil palm plantations emit roughly 2.5 times as much nitrous oxide as rainforest land, a result of vehicle exhaust, combustion, and soil nitrogen fertilization.
Thus, the researchers demonstrated that land use change for the purpose of producing more “environmentally-friendly” biofuels can be problematic. Their results supported the notion that converting rainforest land to oil palm plantations for biofuel production purposes leads to increased emissions of nitrous oxides and volatile organic compounds (VOCs). Although levels of O3 have not yet increased substantially, Hewitt et al. believed that ozone emissions will rise with the increased industrialization and production of nitrous oxides in the area. Such an increase in emissions will negatively impact human health. Moreover, the researchers noted the importance of controlling and managing nitrogen levels at local and regional scales in order to prevent significant changes in the air quality. Because of its potential cost to human health and crop productivity, the researchers argued that oil palm biofuel production might be fairly short-lived.