Replacing coal-fired power plants in Texas with natural gas combined cycle plants would reduce freshwater consumption in the state by an estimated 53 billion gallons annually -- 60% of coal power's current water footprint -- according to a report by researchers at the University of Texas at Austin (UT).
Even when factoring in the use of more water-intensive hydraulic fracturing (fracking) operations to extract natural gas, "natural gas extraction appears to consume less freshwater than coal per unit of energy extracted in Texas because of the high water intensity of Texas lignite extraction," said the report. Lignite extraction is more than three times as water intensive as gas extraction, "primarily because of the need to de-water mines."
The researchers quantified water consumption associated with Texas' coal- and gas-fired electricity using resource basin-specific data and including major second-order sources of water consumption, including the water intensity of unconventional natural gas production via fracking as quantified for 11 separate basins.
Coal-fired power generation accounted for an estimated 90 billion gallons of freshwater consumption in the state in 2007. Generating the same amount of power from natural gas combined cycle plants would consume an estimated 37 billion gallons of water, the researchers said.
"The impact of coal-to-natural gas fuel-switching on freshwater consumption in Texas is highly relevant to state policy," they said. Water resources in the state, which last year experienced a drought over 100% of its area -- leaving more than 11 GW (about 1%) of power generation capacity at risk of curtailment -- are increasingly strained, they said. The water savings possible by switching coal-fired generation to natural gas "are particularly attractive when combined with the potential for positive economic and air quality impacts to Texas, a major natural gas producer and coal importer."
Switching from coal-fired to gas-fired generation would increase natural gas demand in the state by about 1.04 Tcf annually, according to the report.
Last year another team of UT researchers, which included two of the same members as the more recent study, concluded that fuel switching to natural gas in the power, transportation and residential sectors "has significant economic and environmental benefits for Texas," and could potentially have the same benefits on a larger scale if implemented nationwide (see NGI, Oct. 24, 2011). In the power sector, the researchers found that replacing 4,000 MW of capacity from coal-fired plants would require roughly 0.23 Tcf of gas annually, an amount unlikely to have much influence on the natural gas market but enough to potentially replace 24% of the state's 2007 coal-fired generation.
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