Wasting water

8 June 2007

Everyone hopes alternative energies can rein in global warming - but it may come at a price. The US Department of Energy is worried that some technologies could make world water shortages worse

Amid all the hype and excitement surrounding clean energy adoption, Ron Pate, from Sandia National Laboratories in the US, argues that one big component has gone largely unnoticed. Hardly anyone's talking about water and energy interdependence.

Which is all a little worrying when you consider that the energy decisions we make today will have far-reaching consequences for our fresh water supplies in coming decades. Energy production requires water - and water processing and transportation require energy. Worse, some alternative energies actually consume more water than traditional sources.

Pate is certainly in a position to know about the scale of the problem. Sandia, a Department of Energy-owned public/private partnership, has a remit to develop technologies to enhance US national security, a key priority for a country that's increasingly worried about the military and security implications of its 'addiction' to oil. While much of Sandia's work is in the nuclear sector, it also carries out significant research into alternative energies.

Speaking at last month's Cleantech 2007 conference in Silicon Valley, Pate pointed out that the same amount of freshwater is drawn down for thermoelectric cooling and emissions scrubbing as is used in irrigated agriculture - around 39 per cent of the total draw down goes on each, according to figures from 2000, compared to just 14 per cent going into the public supply. The figures for actual consumption are less dramatic, since water from the power industry can be recycled - on this basis, according to figures from the 1990s, irrigation accounts for 80-odd per cent of freshwater consumption, while thermoelectric ties with industrial use at just 3.3 per cent. But as Pate points out, the thermoelectric figure could easily double in the next couple of decades.

The fundamental problem is that freshwater supply is 'fairly well maxed out'. In a 2003 General Accounting Office study, most US states' water managers said they expected shortages over the next decade, even under normal climate conditions. But as populations and economies grow, they create additional demand for both water and power. And then there's the wild card of climate change - if snowpacks melt, for example, that has a serious impact on freshwater supplies.

And that's before we start adopting alternative energies on a bigger scale. 'Bioenergy and biofuel production will increase water demand,' says Pate, pointing out that two to six gallons of water are used per gallon of ethanol refined. According to a US Department of Energy report to Congress entitled 'Energy Demands on Water Resources', which was made public in February, 'the most water-intensive aspect of biofuel production is growing the feedstock, with water consumption for refining generally similar to that for oil refining. When the feedstock is corn or soy (used to make ethanol and biodiesel, respectively), and grown on irrigated land, then the water consumption per gallon of fuel produced can exceed the water consumption for refining by a factor of one thousand.'

So the big question is - can energy generation be scaled up in a way that doesn't damage the environment or create major water problems? It's possible. Some alternative energies, such as solar and wind, don't have anything like the same water impact, although their percentage contribution to total energy generation is still small. And new sources of alternative energies are being researched - Pate points out that algae, for example, holds promise as an energy source, and has the added advantage that it doesn't need fresh water or high-value arable land. At the same time, we could adapt our water consumption habits, making more use of salinated water and reusing waste water.

Then again, don't expect this to be simple. Pate warns, somewhat inevitably, that non-conventional water use may actually require more energy-intensive treatment. And so the vicious cycle of interdependency continues to turn...

By Keith Rodgers, Webster Buchanan Research