Replacing coal-fired power plants with natural gas-fired ones would save as much as 60 percent of the fresh water used in Texas for power generation, according to a report released Tuesday by the Texas Clean Energy Coalition.
Despite the massive amounts of water used by hydraulic fracturing to extract natural gas from shale, coal power plants in Texas generally are less efficient and more water-intensive than their gas counterparts, the researchers said.
“One of the biggest reasons for the lower water consumption for the natural gas fuel cycle is the much higher efficiency of natural gas combined cycle power plants versus Texas’ currently operating pulverized coal-fired power plants,” said study co-author Emily Grubert, a graduate research assistant for the UT Austin Department of Environmental and Water Resources Engineering.
The study measured the three largest water needs in the power generation life cycle: energy production, plant cooling and emissions control. While cooling uses the highest volumes, the growing prevalence of fracking and stiffer emissions regulations have increased water use in those areas as well.
Unconventional natural gas production, like shale gas, uses 10 to 35 times more water than conventional natural gas, Grubert said. Still, coal mining uses five times more water than the average natural gas extraction operation.
However, power generation in Texas slightly skews water use results. Texas coal is largely lignite. Lignite mining uses much higher volumes of water than other types of coal, Grubert noted.
“On a kilowatt-hour basis, Texas lignite is about seven times more water intensive than Texas natural gas,” she said. “That is not applicable across the United States.”
Further, natural gas plants generally are newer and use the more efficient combined cycle form of power generation.
While most electricity in the United States is generated by coal, natural gas is dominant in Texas. Natural gas-fired power plants generated about 53 percent of the electricity in Texas during July, according to federal data. About 33 percent came from coal-fired plants and 9 percent was nuclear power. The rest came from renewable sources.
The study was part of a nationwide look at water use funded by the George and Cynthia Mitchell Foundation, the U.S. Department of Energy and the National Science Foundation.