University of Twente Student Theses


The water footprint of bioenergy

Meekeren, Bouke Theodoor van (2008) The water footprint of bioenergy.

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Abstract:Fresh water is an important natural resource which is limited and scarce. Fossil energy is another important resource which is associated with emissions of greenhouse gasses. An alternative energy source is bioenergy, such as biomass from crops, which consume fresh water to grow. Therefore, there is an interaction between fresh water and bioenergy. The objective of this research is to quantify the relation between fresh water and bioenergy. The research contains three sub-objectives, the first is to assess the volume of water which associates with one unit of bioenergy produced in the current system. The second is to assess this for an optimal system where biomass and bioenergy are produced more efficient. The third sub-objective is to assess the volume of water which associates with the current consumption of bioenergy. Basis for the calculation of the relationship between water and bioenergy is the water footprint concept. The research includes input from three systems: the energy, the agriculture, and the water system. The first regards the kind of energy and the amount of energy which can be obtained from biomass. Here primary energy is the energy of the whole plant, secondary energy is energy or energy carriers made from this biomass. The current system regards secondary energy as biodiesel, ethanol, or power which are produced with ‘conventional processes’. Part of the optimal system, second transformation, includes second generation processes to also utilize crop residues. Second is the agriculture system, this regards biomass yields and cultivation characteristics. The current system regards current yields and current cultivation characteristics. The second part of the optimal system, HEI-system, uses different cultivation characteristics, such as irrigation, to achieve higher yields. The water system regards water consumption during crop cultivation. This consists of soil moisture (green water), irrigation water (blue water), and pollution caused by fertilizers (grey water). The average water consumption of bioenergy in the current system varies greatly per crop and per kind of energy (-carrier). The average water consumption of primary energy in the current system ranges from 20 to 80 m3/GJ HHV . The average of secondary energy ranges from 40 m3/GJ HHV for ethanol from sugarbeet to 500 m3/GJ HHV for power from rape (oil). The optimal system consists of second transformation and the HEI-system. Both components of the optimal system can be combined. In this case, the average water consumption of liquid biofuels (biodiesel and ethanol) ranges from 20 to 40 m3/GJ HHV . The total water footprint of bioenergy consumption, as covered in this research is 1500 Gm3/yr. Compared to the global water consumption this is a considerable amount. Therefore, consumption of bioenergy has a large impact on fresh water resources.
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Subject:43 environmental science
Programme:Civil Engineering and Management MSc (60026)
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