IWRA Proceedings

AbstractAbstract conference 13th IWRA World Water Congress 2008, 1-4 September, Montpellier, France The Water Footprint of Energy Carriers P.W. Gerbens-Leenes*, A.Y. Hoekstra and Th. H. van der Meer University of Twente, the Netherlands Introduction Today, the scientific as well as the international political community consider global change often in relation to climate change. It is generally recognized that emissions of greenhouse gasses, such as CO2 from fossil energy carriers, are responsible for anthropological impacts on the climate system. A shift towards CO2-neutral energy carriers, such as biomass, is heavily promoted. Important issues in this respect are trade offs and interplays with other factors that play a role in global changes other than climate change, such as, for example, the availability and increased pressure on global water resources. The use of energy in society requires water. Energy carriers are often made available with water, for example, for coal mining, or produced with water, for example, biomass. The objective of this study is to calculate the water footprint (WFP) of different types of biomass and compare these results with the WFP of other energy carriers, such as fossil energy carriers (coal, natural gas, oil), and types of energy, such as wind energy and solar thermal electricity. Method Agriculture, providing biomass for different purposes, requires about 86% of the worldwide fresh water use. In many parts of the world, the use of water for agriculture already competes with other uses such as urban supply and industrial activities. A tool that addresses international virtual water flows is the concept of the WFP. This tool has been introduced by Hoekstra and Hung (2002) and has been developed further by Chapagain and Hoekstra (2004). Those authors define the WFP as the total annual volume of freshwater used to produce the goods and services related to a certain consumption pattern. So far, the tool has been used to assess the WFP of food and cotton consumption. This study assesses the WFP of various types of biomass by applying the WFP concept resulting in the WFP of biomass in m3 per GJ. Next, the study compares this WFP with data on water requirements of other energy carriers and types of energy from literature. Results and discussion Results show large differences per unit of energy. The WFP of wind energy is zero, of natural gas 0.10 m3 per GJ, of coal 0.04, of nuclear energy 0.09, of thermal solar energy 0.3, of oil 0.8 and of biomass (average) 22.6 m3 per GJ. Based on an energy use of 100 GJ per capita per year in western societies, a mix from coal, oil, nuclear energy and gas requires 26 m3 of water, while 100 GJ from biomass requires 2260 m3. This requirement competes with water for food, which lies in the same order of magnitude. Conclusions Biomass requires much more water per unit of energy than the average fossil energy carrier. A shift in western societies from generally applied energy (fossil and nuclear energy) towards energy from biomass causes a ninety fold increase of the WFP of energy and puts large claims on scarce fresh water resources. Strategies towards larger biomass use for energy should take this large WFP into account. Keywords: Sustainability, climate change, energy, biomass, natural resource use, water footprint Chapagain, A.K., Hoekstra, A.Y., 2004 Water footprints of nations. Value of Water Research Report Series No. 16. UNESCO-IHE Delft, the Netherlands. www.waterfootprint.org Hoekstra, A.Y., Hung, P.Q., 2002. Virtual water trade: a quantification of virtual water flows between nations in relation to international crop trade. Value of Water Research Report Series, No. 11. UNESCO-IHE, Delft, the Netherlands. * Corresponding author. Faculty of Engineering and Technology, Water Engineering and Management, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands P: + 31 53 489 2080, E: P.W.Gerbens-Leenes@ctw.utwente.nl, I: www.utwente.nl