Friday, December 13, 2013

How will Future Ways to Produce Energy Impact Water Supply?

The Water Demand of Energy: Implications for Sustainable Energy Policy Development(14 page pdf, Saeed Hadian and Kaveh Madani, Sustainability, Nov. 5, 2013)

Today we review a paper that examines the type of sources needed to meet the 40% increase in global energy demand and what this implies in terms of a 37 to 66% increase in demand for fresh water. While the search for pollution-free cities in this blog has been on ways of reducing air pollution and usually concludes that non-polluting renewable energy sources are optimum, some of these sources (such as corn and ethanol) have a disproportionate demand for water - as high as 400 times higher than from conventional fossil energy sources. Some sources, such as solar energy, appear to have few if any negative impacts from energy generation but, if one looks at the water impact from the manufacture of photo-voltaic cells, the overall impact changes. The impact on water from fracking natural gas also needs scrutiny from this aspect. The paper being reviewed is based on a water footprint index made up of a blue, green and grey components, referring to the rainwater or surface water consumed during production or the water used for dilution to maintain water quality standards. world energy
Shares of energy sources in world’s total energy supply (a) 2012; (b) 2035.

 Key Quotes:

“global energy consumption is estimated to rise from 77 million BTU (81.2 GJ) per capita in 2012 to 91 million BTU (96 GJ) per capita in 2035, resulting in 40% increase in global energy use in the next two decades “

“ecological footprint exceeded biocapacity by 44% in 2006 and is estimated to exceed the biocapacity by 100% in 2030”

“In the U.S., the energy sector is expected to be the fastest growing water consuming sector, being responsible for 85% of the increase in domestic water consumption in the 2005–2030 period “

Water footprint is a reliable measure for this purpose and represents the amount of freshwater used to produce one unit of energy from a given energy source:
  • blue water footprint, which is the volume of surface and ground water consumed in the energy production process;
  • green water footprint, which represents the volume of rainwater consumed during the production process (related to evapotranspiration and the rainwater incorporated in crop or wood);
  • gray water footprint, which represents the amount of freshwater required to dilute the pollutants such that the quality of water remains above given water quality standards. “
“governmental ethanol subsidies and mandates in the U.S. are aimed to increase the biofuel supply while the water footprint of this type of energy might be 70–400 times higher than the water footprint of conventional fossil energy sources. “

"the amount of water required for total energy production in the world will increase by 37%–66% during the next two decades, requiring extensive improvements in water use efficiency of the existing energy production technologies, especially renewables.”
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