Impacts of near-future cultivation of biofuel feedstocks on atmospheric composition and local air quality

Abstract

Abstract. Large-scale production of feedstock crops for biofuels will lead to land-use changes. We quantify the effects of realistic land use change scenarios for biofuel feedstock production on isoprene emissions and hence atmospheric composition and chemistry using the HadGEM2 model. Two feedstocks are considered: oil palm for biodiesel in the tropics and short rotation coppice (SRC) in the mid-latitudes. In total, 69 Mha of oil palm and 92 Mha of SRC are planted, each sufficient to replace just over 1 % of projected global fossil fuel demand in 2020. Both planting scenarios result in increases in total global annual isoprene emissions of about 1 %. In each case, changes in surface concentrations of ozone and biogenic secondary organic aerosol (bSOA) are significant at the regional scale and are detectable even at a global scale with implications for air quality standards. However, the changes in tropospheric burden of ozone and the OH radical, and hence effects on global climate, are negligible. The oil palm plantations and processing plants result in global average annual mean increases in ozone and bSOA of 38 pptv and 2 ng m−3 respectively. Over SE Asia, one region of planting, increases reach over 2 ppbv and 300 ng m−3 for large parts of Borneo. Planting of SRC causes global annual mean changes of 46 pptv and 3 ng m−3. Europe experiences peak monthly mean changes of almost 0.6 ppbv and 90 ng m−3 in June and July. Large areas of Central and Eastern Europe see changes of over 1.5 ppbv and 200 ng m−3 in the summer. That such significant atmospheric impacts from low level planting scenarios are discernible globally clearly demonstrates the need to include changes in emissions of reactive trace gases such as isoprene in life cycle assessments performed on potential biofuel feedstocks.