It is generally accepted that emissions of greenhouse gasses, such as CO2 from fossil energy carriers, are responsible for anthropogenic impacts on the climate system. In this context, there has been a remarkable shift in policy attitudes towards CO2-neutral energy carriers such as biomass. The production of biomass for food and fibre in agriculture requires about 86% of the worldwide freshwater use. In many parts of the world, the use of water for agriculture competes with other uses such as urban supply and industrial activities. In a scenario of increasing degradation and decline of water resources, a shift from fossil energy towards energy from biomass puts additional pressure on freshwater resources.

There are large differences among the water footprints for specific types of primary energy carriers. As a whole, the water footprint of energy from biomass is 70 to 400 times larger than the water footprint of the other primary energy carriers (excluding hydropower). Nevertheless, it depends on crop type, agricultural production system and climate. The trend towards larger energy use in combination with increasing contribution of energy from biomass to supply will bring with it a need for more water. This causes competition with other claims, such as water for food crops.

When crops are used for bio-energy, it is more efficient to use the total biomass, including stems and leaves, to generate electricity than to use only a fraction of the crop (its sugar, starch or oil content) to produce biofuel. The weighted average water footprint of energy (m3/GJ) is a factor two to four smaller for bio-electricity than for bio-ethanol or biodiesel. This is because for electricity, the total biomass can be used; whereas for ethanol or biodiesel only the sugar or starch respectively the oil fraction of the yield can be used. In general, when considering biofuels for transportation, the water footprint of bio-ethanol is smaller than the water footprint of biodiesel.

Publications

2012	Gerbens-Leenes, W. and Hoekstra, A.Y. (2012) The water footprint of sweeteners and bio-ethanol, Environment International, 40: 202-211.		1.2 MB
2012	Mekonnen, M.M. and Hoekstra, A.Y. (2012) The blue water footprint of electricity from hydropower, Hydrology and Earth System Sciences, 16(1): 179-187.		0.9 MB
2011	Mekonnen, M.M. and Hoekstra, A.Y. (2011) The green, blue and grey water footprint of crops and derived crop products, Hydrology and Earth System Sciences, 15(5): 1577-1600.		1.2 MB
2011	Gerbens-Leenes, W. and Hoekstra, A.Y. (2011) The water footprint of biofuel-based transport, Energy & Environmental Science, 4(8): 2658-2668.		0.3 MB
2010	Mekonnen, M.M. and Hoekstra, A.Y. (2010) The green, blue and grey water footprint of crops and derived crop products, Value of Water Research Report Series No.47, UNESCO-IHE.	Main Report Volume 1	1.2 MB
		Appendices Volume 2	9.7 MB
2010	Gerbens-Leenes, P.W. and Hoekstra, A.Y. (2010) Burning water: The water footprint of biofuel-based transport, Value of Water Research Report Series No.44, UNESCO-IHE.		0.4 MB
2010	Van Lienden, A.R., Gerbens-Leenes, P.W., Hoekstra, A.Y. and Van der Meer, Th.H. (2010) Biofuel scenarios in a water perspective: The global blue and green water footprint of road transport in 2030,Value of Water Research Report Series No.43, UNESCO-IHE.		1.3 MB
2009	Gerbens-Leenes, P.W. and Hoekstra, A.Y. (2009) 'The water footprint of sweeteners and bio-ethanol from sugar cane, sugar beet and maize', Value of Water Research Report Series No.38, UNESCO-IHE.		0.7 MB
2009	Gerbens-Leenes, W., Hoekstra, A.Y. and Van der Meer, T.H. (2009) The water footprint of bioenergy, Proceedings of the National Academy of Sciences, 106 (25): 10219-10223		0.5 MB
2009	Gerbens-Leenes, W., Hoekstra, A.Y. and Van der Meer, T.H. (2009) A global estimate of the water footprint of Jatropha curcas under limited data availability, Proceedings of the National Academy of Sciences, 106(40): E113.		0.7 MB
2009	Hoekstra, A.Y., Gerbens-Leenes, W. and Van der Meer, T.H. (2009) The water footprint of Jatropha curcas under poor growing conditions, Proceedings of the National Academy of Sciences, 106(42): E119.		0.7 MB
2009	Gerbens-Leenes, P.W. Hoekstra, A.Y. and Van der Meer. Th. (2009) The water footprint of energy from biomass: A quantitative assessment and consequences of an increasing share of bio-energy in energy supply, Ecological Economics, 68(4): 1052-1060		0.4 MB
2008	Gerbens-Leenes, P.W., Hoekstra, A.Y. and Van der Meer, Th.H. (2008) 'Water footprint of bio-energy and other primary energy carriers'		0.5 MB