Policies that cut carbon emissions may be counterproductive if they strain dwindling water supplies -- a problem that has already stemmed from some poorly crafted laws, experts said.

Water and energy systems are intertwined throughout the world. Forty percent of the United States' freshwater withdrawals are used to produce energy, and 18 percent of the nation's electricity goes to treat, move, distribute and use water.

How both of these resources are used is raising concerns worldwide as scientists link fossil fuels to climate change and water supplies become increasingly scarce.

With many experts dubbing water the new oil, U.S. senators hope to integrate energy and water policy, and Sens. Lisa Murkowski, R-Alaska, and Jeff Bingaman, D-N.M., have introduced legislation to do just that.

It's more important now than ever to bring these two issues together as the nation looks to green its energy supply, Murkowski said Tuesday at a hearing in the Senate Energy Committee. That's because many clean-energy technologies have unintended consequences for water.

"An energy technology that produces zero emission … is worthless if it's going to consume more water than we can supply," Murkowski said.

Different energy-production methods require different amounts of water. Nuclear power plants, which are carbon-neutral, consume about 40 percent more water than coal plants, according to the National Energy Technology Laboratory, an arm of the U.S. Department of Energy.

Other technologies aimed at reducing emissions could decrease water supplies, including carbon capture and storage, where carbon dioxide is taken out of power plant emission streams and then stored underground in geological formations or saline aquifers that contain water too salty to drink.

"The use of technologies to capture CO2 out of the current fleet (of coal-fire power plants) requires a lot of energy and additional water," NETL Director Carl Bauer told senators at Tuesday's hearing.

Power plants with carbon-capture technology may consume as much as 90 percent more water than conventional plants; if the technology were widely deployed, it could bump the amount of water that power plants use nationally from 4.1 billion to 6 billion gallons per day, according to a 2007 report by the NETL.

That makes environmentalists like Emily Rochon, climate and energy campaigner at Greenpeace International, wary of policies to speed up the technology's use.

"In the Desert Southwest, where you're already seeing fighting over water usage, the last thing you need to be employing is a technology that requires more water usage," Rochon told United Press International.

Some low-emissions laws have already begun to adversely impact water supplies, said Michael Webber, associate director of the Center for International Energy and Environmental Policy at the University of Texas at Austin.

"We have mandated an increase in water use because of targets for biofuels," Webber told senators.

The Renewable Fuel Standard that Webber referenced, passed at the end of 2007, requires the nation to produce 36 billion gallons of biofuels per year by 2022.

"The RFS will cause water consumption to increase from 1 trillion gallons today to 2.5 trillion in 2022," Webber said.

Ethanol, which will likely account for about 15 billion gallons of the 36 billion required, is made from water-intensive crops like corn. When water for irrigation is included, it takes 1,700 gallons of water to produce one gallon of ethanol, said Sen. John Barrasso, R-Wyo.

Not all biofuels consume water at this rate, though. Researchers can now produce fuel from waste materials, such as wood and agricultural leftovers, as well as algae. One company, PetroAlgae, is now producing fuel from algae with a water-recycling rate of 98 percent.

"It is a little bit counterintuitive, because algae grow in water," Fred Tennant, vice president of business development at PetroAlgae, told UPI. "We harvest the algae and dewater it, and then we put the water back in the bioreactor" where the algae grow.

There are other climate-friendly energy options that go easy on water, too. For instance, solar photovoltaic and wind energy require almost no water to produce.

Power plants can also install equipment that recycles water more efficiently and eliminates waste. However, this costs money, which means the vast majority of U.S. facilities are using more water than necessary, said Stephen Bolze, chief executive of General Electric Energy's Power and Water business.

"Of our 50,000 customers, less than 1 percent are really reusing any water," Bolze said.

That's not very much compared to the industrial sectors in other countries. The United States only recycles 6 percent of its water; Australia reuses 6 percent; Singapore, 15 percent and Israel, a whopping 70 percent. Domestic water savings would rise if Congress learned a lesson from these countries and provided tax incentives for energy producers who install water-management systems, Bolze said.

Policymakers can also look within U.S. borders for ideas on integrating water and energy policy. California, for instance, has a pilot program that facilitates cooperation between energy utilities and water providers to implement projects to save both water and energy.

Bingaman and Murkowski's bill lays out a number of objectives, including a study by the National Academy of Sciences on water usage in producing fuels and electricity, increased Energy Department research on the best technologies to help power plants decrease water use and a requirement that the Energy Information Administration continually track water usage.

These steps are essential to avoiding unintended consequences, said experts at Tuesday's hearing, including Peter Gleick, president of the Pacific Institute, a California-based environmental research organization.

"The failure to consider both (water and energy) together leads us to make bad decisions, bad policies," Gleick said.

([email protected])