Do biofuels require more water than do fossil fuels? Life cycle-based assessment of jatropha oil production in rural Mozambique

Abstract

Biofuels are advanced to replace fossil fuels in order to reduce emissions of greenhouse gases and other environmental impacts. Yet freshwater scarcity is another growing concern and increased production of biofuels may increase this problem. In order to assess whether biofuels truly have a higher water use than do fossil fuels, a life cycle assessment study of a low input jatropha plantation in northern Mozambique was conducted. In addition to different water use indicators, the fossil energy use and global warming potential were assessed for 1 MJ of jatropha oil. The analysis compares results for jatropha oil with fossil diesel, generally showing lower global warming potential and fossil energy use for jatropha oil. However, aspects related to land use may alter the global warming potential of jatropha oil. Regarding water use, the choice of the water use indicator strongly influences the results. Specifically the indication of (1) so-called green water flows, (2) formation of so-called blue water and (3) water scarcity show crucial influences on the comparison. Depending on these specific features, jatropha oil may have higher or lower water use than fossil diesel. A number of uncertainties, such as the jatropha oil yield, are also shown to have a considerable impact on the results.