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Electricity is a thirsty business

Fiona Macleod

Recent research showed that the production of energy requires huge amounts of water, a side effect of electricity not often considered by consumers.

Recent research showed that the production of energy requires huge amounts of water, a side effect of electricity not often considered by consumers.

A common household 60-watt light bulb left to burn for 12 hours, for example, uses up about 36l of water. If the household light was left on for 12 hours every day for a year it would consume between 13 500l and 28 350l of water, according to a study by the Virginia Water Resources Research Centre in the United States.

The study concluded that if every household in the US left a light on for 12 hours a day, it would add up to between 1 512bn and 2 952bn litres of water use over the course of a year. “Without water, our energy and power generation systems will come to an abrupt stop,” said the study, titled “The intertwined tale of energy and water”.

It pointed out that most conventional energy extraction and power generation technologies are water-dependent, but some technologies need much more water than others. “In the near future, increased energy development will compete for available water resources with other water demands such as irrigation, domestic water supplies and ecosystem services.”

Thermoelectric, or fossil fuel power plants in South Africa consumed more than 316bn litres of fresh water in 2010, according to Eskom figures. The plants need water to scrub pollutants generated from burning coal, to cool and clean machinery, and to produce the steam necessary to turn huge turbines and generators.

As the demand for electricity demand rose, energy production would place more demands on the country’s scarce water resources, said Earthlife Africa’s Muna Lakhani. The focus on power generation tended to deal with reducing harmful greenhouse gases responsible for climate change, but more attention needed to be paid to the impacts on water resources.

Water availability and protection needed to be incorported into energy and power generation technologies and policies, Lakhani said. Analysis of water consumption for producing and generating power in 2008 indicated that nuclear power used the most water, at least double that of conventional thermoelectric power.

“Whereas thermoelectric power used 14 200l to 28 400l per 1 000Kw/hours, nuclear power used 31 000l to 74 900l. “Hydroelectric power used just 260l, geothermal used 1 680l and solar thermal used 2 970l to 3 500l,” Lakhani said.

The Virginia research indicated that alternative means of producing power are often not water efficient either. “Some of the new energy initiatives, such as biodiesel and ethanol production, are in conflict with protecting water resources,” the study said.

Soy-based biodiesel was the least efficient alternative in terms of litres of water consumed per energy unit, followed by corn-based ethanol. Hydrogen and fuel ethanol also consumed large volumes of water.

Natural gas was the most water efficient and oil shale ranked fourth, after synfuels and tar sands. Yet the production of oil and natural gas is problematic because it usually relies on the re-injection of water into wells.

According to the Water Footprint Network, a monitoring website hosted by the Universtiy of Twente in the Netherlands, water used to produce energy from biomass was high. “As a whole, the water footprint of energy from biomass is 70 to 400 times larger than the water footprint of other primary energy carriers, excluding hydropower.

“The trend towards larger energy use, in combination with the increasing contribution of energy from biomass, will bring with it a need for more water,” the Network said, citing various recent scientific studies on the topic.

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