Impact of land use change on greenhouse gas emissions from Jatropha biofuels : review of recent studies

The chapter reviews the studies available to date about the impact of the introduction of the biofuel crop Jatropha curcas on greenhouse gas GHG emissions from land use change in tropical regions. The limited available data consistently point to Jatropha's GHG reduction potential when the plant is grown on wastelands or severely degraded agricultural lands. At the same time, the studies suggest - directly or indirectly - that the GHG balance will tip in the other direction if Jatropha were to be introduced on more productive lands, where considerable carbon is being stored in the existing biomass and/or soil. However, none of the available studies has taken account of land use change in a comprehensive and realistic fashion, and therefore there is no information as to where the GHG tipping point lies in specific situations. Further research should be aimed in particular at measurement of soil organic carbon (SOC) levels under different climatic and ecosystemic conditions, and at refming concepts of 'wastelands', 'degraded lands' and so on, in order to prevent wrong estimations and misallocation of lands for Jatropha production on a vast scale. Furthermore, efforts should be devoted to standardizing LCA methodologies and their application in terms of boundary assumptions, input and output assumptions and measurement units so that GHG results from different studies can be more easily compared.