Group Hoekstra/Gerbens

Research topic: Water Footprints of Energy Use Description: Description: Description: C:\Users\ARJENE~1\AppData\Local\Temp\Rar$DI00.754\WaterFootprintLogo-darkblue-lowres.jpg

Research group: Faculty of Engineering Technology/Water engineering and management

People involved: professor Arjen Y. Hoekstra and dr. P. Winnie Gerbens-Leenes

Contacts: and

Freshwater of adequate quality is an important issue in many countries. Today, most freshwater is used in agriculture, which is becoming increasingly important for bioenergy production. All forms of energy have a water footprint (WF); these include various biofuels, as well as fossil energy, wind, solar, and hydropower.

Our research focuses on the use of fresh water for all types of human consumption, such as water for food, materials and energy. Agriculture accounts for a majority (about 86 percent) of fresh water used by humans. The other part is used by industry (9 percent) and by households (5 percent). Energy extraction of all kinds—coal, nuclear, bioenergy, etc.—requires the use of water. The use of water for bioenergy is the main use of water as an energy resource. Our research shows that there are large differences in water needed to produce a unit of energy, for example to produce ethanol or biodiesel (see figure 1).

Figure 1. Global weighted average green (precipitation), blue (ground and surface water) and grey (water related to pollution) water footprints of ethanol for ten crops

The most water efficient way to generate bioenergy is to use total biomass and generate heat. Electricity generation is the second best option. First-generation biofuels are less water efficient than the future biofuels using new techniques. Important energy carriers also include fossil energy (crude oil, coal and natural gas), uranium, and electricity from hydropower. Promising renewables are solar and wind energy. We do not know their water footprints yet. Present projects are the water footprints of algae (presently, a SET student is working on the topic) and the water footprint of Solar energy (project with Abengoa, Spain).

Future research projects:

We would like to expand our knowledge in the direction of water for energy and calculate water footprints of:


fossil energy (coal, gas, crude oil)


wind energy (cooperation with the UT group of Production Technology of prof. Akkerman)


hydropower in China (cooperation with the Beijing University of Forestry)


biodiesel under different scenarios (cooperation with ITC)