Water consumption from coal plants
Power generation has been estimated to be second only to agriculture in being the largest domestic user of water. To produce and burn the 1 billion tons of coal America uses each year, the mining and utility industries withdraw 55 trillion to 75 trillion gallons of water annually, according to the US Geological Survey.
It was estimated in January 2011 report by the Civil Society Institute, "Benefits of Beyond BAU: Human, Social, and Environmental Damages Avoided through the Retirement of the US Coal Fleet", that the number of gallons drawn per day for nuclear and coal power plants is 200 billion gallons. According to data collected by the United States Geological Survey (USGS), water withdrawals from thermoelectric power sources account for 49 percent of total withdrawals in the United States in 2005, or 201 billions a day.
The 2012 report "Burning Our Rivers: The Water Footprint of Electricity" estimates that a mega-watt hour (MWh) of electricity generated by coal withdraws approximately 16,052 gallons and consumes approximately 692 gallons of water.
Additionally, the debris from mountaintop removal is often pushed into streams, depleting freshwater supplies. Coal combustion produces the nation’s largest share of carbon dioxide and other greenhouse gases that are accelerating global climate change and also diminishing the nation’s freshwater reserves. And water is used daily in mining operations to cool and lubricate mining machinery, wash haul roads and truck wheels to reign in airborne particulates, and to suppress underground coal dust that otherwise could ignite.
Coal Plant Water Usage
Water is used by thermoelectric generating facilities (coal, natural gas, and nuclear) to make electricity through converting the water into high-pressure steam to drive turbines. Once through this cycle, the steam is cooled and condensed back into water, with some technologies using water to cool the steam, increasing a plant's water usage. In coal plants, water is also used to clean and process the fuel itself. The U.S. Geological Survey estimates that thermoelectric plants withdrew 195 billion gallons of water per day in 2000, of which 136 billion gallons was fresh water. Researchers at Sandia National Laboratories put the estimate higher, finding that the typical 500-megawatt coal-fired utility burns 250 tons of coal per hour, using 12 million gallons of water an hour—300 million gallons a day—for cooling.
The two primary evaporative technologies for cooling power plants are categorized as wet and dry; hybrid systems are also in use. Wet systems dissipate heat to the atmosphere either by recirculating water through a cooling tower or by constantly replenishing an evaporative cooling pond. In the U.S. roughly 39% of coal plants use once-through cooling, while 60% evaporate heat via wet recirculating cooling towers or cooling ponds; less than 1% makes use of dry cooling, which use no water but are more expensive than wet systems. According to the Department of Defense National Energy Technology Laboratory (NETL), a wet recirculating cooling water system for a 520-MW coal-fired power plant uses about 12 million gallons of water per hour.
Processing and Cleaning
Although water requirements for cleaning or scrubbing coal are a fraction of those required for cooling purposes, they require a significant amount of water to produce and handle the various process streams, including limestone slurry and scrubber sludge. Makeup water requirements for a 550 MW coal-fired plant with a flue gas desulfurization island, to lower the emission levels for sulfur dioxide (SO2) under the Clean Air Act and help prevent acid rain, are about 570 gallons per minute (gpm), compared to about 9,500 gpm for cooling water makeup.
Power plants, like the Clinch River Plant, use tens of millions of gallons of water or more of freshwater daily. The coal turns the water to steam, the steam powers the turbines, and what’s left of the coal, the fly ash, is scraped from the smokestacks and stored in federally unregulated coal waste sites.
Mountaintop removal and water
Mountaintop removal (MTR) mining involves the blasting off the tops of mountains to reach the coal seams below, with the millions of tons of former mountains pushed into stream valleys. MTR has buried nearly 2,000 miles of Appalachian streams, while also contaminating drinking water, impairing water quality for river recreation, increasing water treatment costs for industry, displacing some communities, and increasing susceptibility to flooding for others.
"Clean Coal" and Increased Water Usage
Integrated Gasification Combined Cycle (IGCC), which converts coal into synthetic gas or syngas to extract more energy, is being promoted as a path toward carbon capture and storage; however as of 2009 capturing carbon dioxide (CO2) reduces plant efficiency and increases water usage. An Electric Power Research Institute study found CO2 capture equipment decreased plant output by at least 25% and increases water consumption by approximately 23%. Scientists with Sandia National Laboratories who’ve studied CCS say it will increase water withdrawal and use by 25 percent to 40 percent.
Integrated Gasification Combined Cycle (IGCC) can also contribute to water contamination through cleaning the syngas. Coal gasification wastewater has an average pH of 9.8, while pure water has a pH of 7.0. The principal contaminant of “process wastewater” is nitrate, which contributes to algal blooms and dead zones. The Great Plains Coal Gasification plant in Beulah, North Dakota, generated 4.83 million metric tons of wastewater in 1988, contaminating local groundwater with high pH, sulfates, chlorine, arsenic, and selenium. The Department of Energy’s IGCC pilot project in Wabash River, Indiana, the Wabash River Generating Station, had selenium and cyanide limits that “routinely exceeded” legal limits.
Environmental Impacts from Coal Plant Water Usage
Heavy water usage from coal plants can have a long-term impact on aquifers in a region, since once depleted they can take hundreds of years to replenish. In 2011, the Union of Concerned Scientists (UCS) reported that, in at least 120 vulnerable watersheds across the U.S., power plants are a factor contributing to water stress. Power plants can also potentially harm fish eggs, larvae, and other aquatic biota in their early stages, as they require particular combinations of fresh water flow and temperature, among other factors, all of which can be impacted by coal plant water usage.
There is also water pollution from coal, including negative health and environmental effects from acid mine drainage, acid rain, and contamination of groundwater, streams, rivers, and seas from heavy metals, mercury, and other toxins and pollutants found in coal ash, coal sludge, and coal waste. Also, there can be thermal pollution from coal plants, as water not cooled to tolerable temperatures when released back into streams and rivers can kill fish populations or encourage excessive algal growth. Discharged water should therefore not only be cleaned, but also cooled, requiring more water.
Climate change from increased greenhouse gas emissions like carbon dioxide from coal plants is leading to decreased supplies of rain, snowmelt, and fresh water. Energy demand is increasing even as pressure steadily grows to limit greenhouse emissions and reduce water consumption.
Water consumption by states
A 2011 Union of Concerned Scientists report, "Freshwater Use by U.S. Power Plants: Electricity’s Thirst for a Precious Resource," calculated the available water in every major watershed in the U.S. and measured that against the water used by power plants in each watershed. The report found that:
- Every day in 2008, on average, water-cooled thermoelectric power plants in the United States withdrew 60 billion to 170 billion gallons of freshwater from rivers, lakes, streams, and aquifers, and consumed 2.8 billion to 5.9 billion gallons - coal plants were responsible for 67 percent of those withdrawals, and 65 percent of that consumption.
- In the Southwest, where surface water is relatively scarce, power plants withdrew an average of 125 million to 190 million gallons (380 to 590 acre-feet) of groundwater daily, tapping many aquifers already suffering from overdraft. By contrast, power plants east of the Mississippi relied overwhelmingly on surface water.
- Plants in the East generally withdrew more water for each unit of electricity produced than plants in the West, because most have not been fitted with recirculating, dry cooling, or hybrid cooling technologies. Freshwater withdrawal intensity was 41 to 55 times greater in Virginia, North Carolina, Michigan, and Missouri than in Utah, Nevada, and California.
- Power plants across the country contribute to water-supply stress: in 2008, 400 out of 2,106 watersheds across the country were experiencing water-supply stress, particularly in North Carolina, South Carolina, Missouri, and Michigan.
- Power plants that did not report their water use to the EIA accounted for 28 to 30 percent of freshwater withdrawals by the electricity sector, and at least 24 to 31 percent of freshwater consumption by the sector, according to UCS calculations. UCS also noted discrepancies, especially large in the Lower Colorado River and Southeast-Gulf regions, where plant operators reported consumption five times greater—and withdrawals 30 percent less—than median water-use values would suggest.
Drought may shut down Texas power plants
It was reported in August 2011 that a number of Texas power plants might need to cut back operations or shut down completely if the state’s severe drought continues. At the time at least one North Texas power plant has had to reduce how much it generates because the water level in its cooling reservoir has fallen significantly, said Kent Saathoff, vice president of system planning and operations for the Electric Reliability Council of Texas.
It was also reported that if the state’s drought continues and water levels continue to fall at other power plant reservoirs, other units could be forced to curtail operations or shut-down completely.
Renewables vs nonrenewables
The September 2012 Civil Society Institute report, "The Hidden Costs of Electricity: Comparing the Hidden Costs of Power Generation Fuels," concluded that nonrenewable energy sources like nuclear and coal use far more water overall to generate electricity than clean energy technologies like solar and wind. According to the report:
- Nuclear uses 700 - 1,100 gallons per MWh in closed-loop systems and 25,000 - 60,000 gal per MWh in open-loop;
- Coal uses 500 - 600 gal per MWh in closed-loop systems and 20,000 - 50,000 gal per MWh in open-loop;
- Biomass uses 2.42 billion gal per 50 MW plant and 40,000 - 100,000 gal per MWh for irrigating crops to burn;
- Solar uses 225 - 520 gal per MWh (washing Photovoltaic panels) and 800 gal per MWh (Concentrating Solar Power wet method cooling); and
Wind uses 45-85 gal per MWh.
Gas, coal, and nuclear water use
The June 2012 River Network report, Burning Our Rivers: The Water Footprint of Electricity, calculates how much water is used to generate electricity on an average per-kilowatt basis. The report found that electricity production by coal, nuclear, and natural gas power plants is the fastest-growing use of freshwater in the U.S., accounting for more than about half of all freshwater surface withdrawals from rivers -- more than any other economic sector, including agriculture.
- Lance Frazer, "Low water consumption: a new goal for coal" Environmental Health Perspectives, April, 2004
- Sierra Crane-Murdoch, "A Desperate Clinch: Coal Production Confronts Water Scarcity" Circle of Blue, August 3, 2010.
- "200B Gallons of Water Drawn Each Day for U.S. Coal, Nuclear Power" January 31, 2011.
- Wendy Wilson, Travis Leipzig & Bevan Griffiths-Sattenspiel, "Burning Our Rivers: The Water Footprint of Electricity," River Network Report, April 2012.
- Dr. Robert Peltier,“New coal plant technologies will demand more water” PowerMag, April 15, 2008
- Mountaintop Mining/Valley Fills in Appalachia: Final Programmatic Environmental Impact Statement, U.S. Environmental Protection Agency, accessed March 2008.
- “’Clean Coal’ Power Plants (IGCC)" EnergyJustice.net Report, Oct. 31, 2007
- Averyt, K., J. Fisher, A. Huber-Lee, A. Lewis, J. Macknick, N. Madden, J. Rogers, and S. Tellinghuisen, "Freshwater use by U.S. power plants: Electricity’s thirst for a precious resource," A report of the Energy and Water in a Warming World Initiative. Cambridge, MA: Union of Concerned Scientists (p. 25), 2011.
- Averyt, K., J. Fisher, A. Huber-Lee, A. Lewis, J. Macknick, N. Madden, J. Rogers, and S. Tellinghuisen, "Freshwater Use by U.S. Power Plants: Electricity’s Thirst for a Precious Resource," The Union of Concerned Scientists' Energy and Water in a Warming World initiative, November 2011 Report.
- "More power plant woes likely if Texas drought drags into winter" Tom Fowler, Fuel Fix, August 24, 2011.