Analysis: Energy's Water Demands Worrisome

By ROSALIE WESTENSKOW
UPI Correspondent

THE DALLES, Ore., April 24 (UPI) -- Add another requirement to the clean-energy checklist: low water usage.

Two Virginia Tech researchers released a study this week examining the water-use requirements for 11 different energy sources, ranking them in terms of efficiency.

One of the most important aspects of the study was to raise awareness of the role water plays in energy production, said Rachelle Hill, a recent Virginia Tech graduate who co-authored the study.

"We need to do more research and really study what goes into energy production, not just what comes out," Hill told United Press International.

And a lot of water goes in. According to the study, U.S. thermoelectric power plants consume 136 billion gallons of water per day, averaging out to 25 gallons for every kilowatt-hour produced. Water is used in almost every aspect of energy, from the cooling and cleaning of machinery to the production of steam to turn turbines. And as energy demand rises in coming decades, so will the amount of water required to produce it.

Water usage has become a major concern in recent years because supply has dwindled, said Eric Evenson of the U.S. Geological Survey, a federal science agency.

An ever-growing population has increased water usage in a number of sectors, leading to shortages in some areas, Evenson said, and policymakers should examine any strain on supply.

"Any one factor, like water needs for energy, or for public supply, or for agriculture … bears on the quantity of overall water availability," he said.

And energy has a big impact, said Mike Hightower, a member of the Energy-Water Nexus National Lab Team, a group of scientists from a number of national laboratories researching the issue.

"In the United States on a daily basis, about 40 percent of our fresh water withdrawals are for energy production," said Hightower, a technical staff member at Sandia National Laboratories in Albuquerque.

While much of the water used in energy production is not consumed but returned to its source and later reused, the energy sector's reliance on water's availability could cause problems down the road, Hightower told UPI.

"Even if you don't consume a lot of water, if you use it, you need it day in and day out to operate," he said. If a drought occurs, "then water levels lower, you can't withdraw any more and that's going to impact your energy supply."

In the past, U.S. municipalities have often used groundwater faster than it can be replenished, lowering overall groundwater levels. If this continues to occur, Hightower said, power plants and other energy producers will have less water available for use, interrupting their production capabilities.

While the study points out the necessity of looking at water when considering environmental impacts, it raises some issues about how to balance that concern with carbon emissions. The energy sources receiving the highest accolades in the study for their limited water usage also emit CO2, a growing dilemma now that climate-change concerns have overshadowed the energy arena.

Natural gas, a carbon-emitting fossil fuel, took the top spot for water efficiency, but researchers ranked the purportedly less carbon intensive fuel sources biodiesel and corn ethanol last.

Ethanol production received a bad rap because it requires large amounts of water to grow the corn crops used to produce the fuel, and, unlike the water used to cool power plants, irrigation water is not reusable, according to the study. The water seeps into the ground and often becomes contaminated with the fertilizers used on the crops.

On the power-generation side, however, things look brighter. Hydroelectric power came in first, followed by geothermal and solar power. And this doesn't include wind or other types of renewable energy that the researchers excluded from the study specifically because their water use is negligible.

Although hydroelectric requires water, that water is never consumed -- it simply runs through the turbines. This makes it a winner on both fronts, as it emits zero carbon, said Kerry McCalman, power manager for the Bureau of Reclamation, a U.S. Department of Interior agency and one of the largest producers of hydroelectric power in the country.

"Hydropower generated by the Bureau of Reclamation as a whole offsets 31 million tons of CO2 emissions per year, on average," McCalman told UPI.

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