Burning water: the water footprint of biofuel-based transport

摘要

The trend towards substitution of conventional transport fuels by biofuels requires additional water. The EUudaims to replace 10 percent of total transport fuels by biofuels by 2020. This study calculates the water footprintud(WF) of different transport modes using bio-ethanol, biodiesel or bio-electricity and of European transport if 10udpercent of transport fuels is replaced by bio-ethanol. We compare results for Europe with similar goals for otherudregions (Africa, Asia, Latin America, the former USSR, Australia and North America). In order to provide audcontext, we compare results with WFs of food and cotton.udIn general, it is more efficient to use bio-electricity and bio-ethanol than biodiesel. Transport per train or electricudcar using bio-electricity (8-19 and 11-13 litres per passenger km) is more water efficient than transport by caruddriven by bio-ethanol (36-212) or by airplane using bio-ethanol (65-136 litres per passenger km). For cars, weudfind a range of a factor of ten between the most water-efficient car using bio-ethanol and the least efficient carudusing biodiesel. When using bio-energy, freight can be transported in the most water-efficient way by ship orudtrain; airplanes are the least water efficient.udThe European goal to have 10 percent biofuel in transport in 2020 will result in a water footprint of 62 Gm3 perudyear. This is equal to about 10% of the current European water footprint of food and cotton consumption.udDifferences in per capita energy use for transport among European countries, together with differences inudproduction systems, result in a broad range of transport-related WFs: from 60 m3 per year per capita in Bulgariaudto 500 m3 per year per capita in Finland. If the same 10% biofuel target would be applied in all other regions ofudthe world as well, the additional water footprint of China would be equivalent to 5% of the water footprintudrelated to food and cotton consumption, in the rest of Asia 3%, in Africa 4%, in Latin America 10%, in theudformer USSR 22% and both in North America and Australia 52%. The global water consumption related toudbiofuel-based transport in this scenario would be 9% of the current global water consumption for food andudcotton. The results show that a trend towards the increased application of biofuels in transport will substantiallyudenhance the competition for fresh water resources.