Alternative fuels, such as biofuel or hydrogen, could use much more water in their production than conventional petroleum-based fuels, says new research.
According to Carey W. King and Michael E. Webber at the University of Texas at Austin, the production of some alternative fuels could put a strain on water resources in some regions.
The researchers compared the amount of water withdrawn (water taken from source, used and returned for reuse) and consumed (water that is not directly returned to source) per mile travelled by a typical car powered by conventional fossil-fuel based petrol and diesel, biofuels, hydrogen and electricity.
Biofuels derived from irrigated crops like corn in the US require up to three orders of magnitude more water per mile travelled than conventional fuels.
However, non-irrigated biofuels are just as low in water consumption and usage as petrol and diesel.
The picture for hydrogen-powered and electric vehicles depends on how the fuel is produced. If power is derived directly from the US grid (for plug-ins or to produce hydrogen), significantly more water is needed. However, if renewable energy sources are used then the water consumption and usage drops back down to the lowest levels.
The facts and figures:
- Petrol and diesel, non-irrigated biofuels, hydrogen and electricity from renewable resources – <0.15 gal H2O/mile consumed water and <1 gal H2O/mile withdrawn water;
- Hydrogen and electricity derived direct from the US grid (currently mainly fossil fuel and nuclear power) – 2-5 times more consumed water and 5-20 times more withdrawn water;
- Irrigated biofuels (corn ethanol) – 28 gal H2O/mile consumed water and 36 gal H2O/mile withdrawn water;
- Soy-derived biofuels – 8 gal H2O/mile consumed water and 10 gal H2O/mile withdrawn water.
The research indicated that policymakers need to be aware of the differences in water use – particularly for irrigated and non-irrigated biofuel feedstocks – in the planning of alternative fuel adoption. In regions of the US already heavily reliant on aquifers for food crop production, it may not be possible to use those same resources to produce alternative fuels.
For further information:
Carey W. King and Michael E. Webber. Water Intensity of Transportation. Environ. Sci. Technol. (2008), 10.1021/es800367m
20 October 2008