“Turn off that light!” (… and save water)

Here’s a new argument for getting your kids to “Turn off that light!”

Increasing power bills are one thing… Global Warming is another… but did you know that burning more power than we need can lead to water shortages too? For every 12 hours that a 60 watt bulb is lit, the power required to keep it burning has used approximately 60 litres of water.

A team from the Virginia Water Resources Research Center in the U.S. has collated material from a number of sources and calculated the water required to supply fuel sources. Here are the results by fuel source, taken from an article written by Willie D. Jones on the the Institute of Electrical and Electronics Engineers web site – http://www.spectrum.ieee.org

Researchers also looked at water consumption by type of electricity generation:

So why does it take so much water to keep a light bulb burning? The extraction of the petroleum-based fuel sources from deep beneath the ground requires a lot of water… as does the stripping, refining and processing of these fuels. But by far the biggest user of water is the plant-based power-products – ethanol and bio-fuels. These are traditionally considered to be ‘green power’ … but there’s another argument.

Fuel ethanol is mostly made from the starch in corn kernels or the juice in sugar cane while bio-fuels (such as bio-ethanol and bio-diesel) are in theory carbon-neutral as the CO2 released by burning the fuel is equalled by the CO2 absorbed by the corn or sugar from which the fuel is produced. The dissenters however say that far from solving our problems, bio-fuels trash rainforests, suck water reserves dry, kill off species and raise food prices.

They’re also worried about a possible acceleration in the corporate takeover of agriculture, which could leave fuel importers as dependent as ever on other countries. The truth is probably that the environmental benefits of bio-fuels over fossil fuels may be more limited than is usually assumed.

Sugar beet in particular – used by the world’s leading producer and user of bio-fuels (Brazil) – is a very ‘thirsty’ crop. Its widespread use for fuel purposes puts huge pressure on water supplies.

Generation of the power we use in our daily lives also uses vast amounts of water, mostly for cooling towers.

So what’s the answer? We can’t really choose how our power is generated and even if we choose to buy ‘green power’, it may be from a plant source that is using way too much water.

Small-scale solutions like solar panels on every rooftop and rainwater tanks for every roof would be a great response. If we reduce the need to generate and distribute vast amounts of energy to homes, we automatically reduce our CO2 footprint, our power bills and the amount of precious water we use by leaving those lights on.

Energy’s Water Footprint

According to Conservation Magazine’s reporting of an Environmental Science & Technology publication (Earth Stats.), “It can take 3,028 litres of irrigation water to produce the amount of corn necessary to make just 3.8 litres of ethanol.”

Here is a breakdown of the amount of water needed to produce the fuels needed to quench our energy needs (Litres per Megawatt hour):

  • Oil refining: 80-150
  • Oil Shale: 170-681
  • Natural Gas Combined Cycle power plants: 230-30,300
  • Coal: 900
  • Nuclear, closed loop cooling: 950
  • Geothermal, closed loop cooling: 1,900-4,200
  • Enhanced Oil Recovery: 7,600
  • Natural Gas Combined Cycle power plants, open loop cooling: 28,400-75,700
  • Nuclear, open loop cooling: 94,600-227,100
  • Corn ethanol irrigation: 2,270,000-8,670,000
  • Soybean bio-diesel irrigation: 13,900,000-27,900,000

Data: Conservation Magazine July/Sept 2009


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