Less coal use translates to dramatic reductions in water usage, reports a team from Duke University.
The gradual transition from coal to natural gas and renewable energy in the U.S. is dramatically reducing the use of water in the energy industry. Furthermore, these overall savings in both water consumption and water withdrawal have been seen during a period where fracking and shale gas production have intensified their use of water.
“While most attention has been focused on the climate and air quality benefits of switching from coal, this new study shows that the transition to natural gas — and even more so, to renewable energy sources — has resulted in saving billions of gallons of water,” said Avner Vengosh, Professor of Geochemistry and Water Quality at Duke’s Nicholas School of the Environment.
The team estimates that for every megawatt of electricity produced from natural gas instead of coal, the energy industry withdraws 10,500 fewer gallons of water from the environment (rivers and groundwater). That is equivalent to a 100-day water supply for a typical American household, according to the team. At the same time, water consumption (which is water used by a power plant but not returned to the environment) drops by 260 gallons per megawatt.
If these figures remain steady, and in the context of coal being slowly phased-out by fuels such as shale gas over the next decade, the team estimates that the energy industry will save up to 483 billion cubic meters of water per year by 2030. If all of today's coal-fired plants switch to natural gas, yearly savings will reach 12,250 billion gallons. That's over two-and-a-half times the quantity of water that the United States industry uses annually.
So whence doth the savings come? Coal mining and fracking use roughly the same quantities of water, the team explains, but natural gas power plants use much less of it than coal plants. The difference mostly comes from their cooling systems. Since around 40% of all water use in the U.S. today goes to cooling thermoelectric plants, individual reductions stack up to huge overall savings, Vengosh explains.
"The amount of water used for cooling thermoelectric plants eclipses all its other uses in the electricity sector, including for coal mining, coal washing, ore and gas transportation, drilling and fracking," he said.
However, compared to gas and coal, solar and wind use virtually no water. The study showed that the water intensity (i.e. overall water use throughout their lifecycle) of these renewable sources is only 1% to 2% of that of coal or gas (as measured by water use per kilowatt of generated energy). In other words, a substantial shift to solar and wind would eliminate “much” of the water withdrawal and consumption for energy generation in the U.S.
Natural gas overtook coal as the primary fossil fuel for electricity generation in the United States in 2015, mainly due to the rise of unconventional shale gas exploration (fracking). It made up 35.1% of U.S. electricity in 2018, while wind and solar accounted for 6.5% and 2.3%, respectively. Coal-fired plants generated 27.4% of U.S. electricity in 2018.
The paper "Quantification of the water-use reduction associated with the transition from coal to natural gas in the U.S. electricity sector" has been published in the journal Environmental Research Letters.