The EU target to replace 10 percent of transport fuels by renewables by 2020 requires additional water. This study calculates water footprints (WFs) of transport modes using first generation bio-ethanol, biodiesel or bio-electricity and of European transport if 10 percent of transport fuels is bio-ethanol. Results are compared with similar goals for other regions. It is more efficient to use bio-electricity and bio-ethanol than biodiesel. Transport by train or car using bio-electricity (8-19 and 11-13 litres per passenger km) is more water efficient than transport by car (36-212) or airplane (65-136) using bio-ethanol. For cars, there is a factor of ten between water-efficient cars using bio-ethanol and water-inefficient cars using biodiesel. Biofuel-based freight transport is most water-efficient by ship or train; airplanes are least efficient. Based on first generation biofuels, the EU goal for renewable transport energy results in a WF of 62 Gm 3 per year, 10 percent of the current WF. Differences in transport energy use and in production systems result in a broad range of annual transport-related WFs: from 60 m 3 per capita in Bulgaria to 500 m 3 in Finland. If similar targets are applied in other regions, the additional WF of North America and Australia will be 52 percent of the present regions WFs. The global WF for biofuel-based transport in this scenario will be 9 percent of the current global WF. Trends towards increased biofuel application enhance the competition for freshwater resources. © 2011 The Royal Society of Chemistry.
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