We don’t give a second thought to many things in our daily lives until those things become hard to get or costly. We don’t think about where electricity comes from when we turn on a light switch nor do we give much thought to the many steps it takes for gasoline to be readily available whenever we stop to fill up our tank.
Water is another resource we may often take for granted. As the drought in Texas has become more prolonged, water is becoming an everyday consideration.
Something else we don’t think about is how much water it takes to produce the energy that we use, whether it is the fuel that is used to produce the electricity, the gasoline that we put in our cars or the natural gas that we use to heat our water and cook our food.
The U. S. Department of Energy has studied how much water it takes to produce the energy resources that we depend on and the results of their studies were quite surprising. It turns out that the most water-efficient raw fuel source is natural gas, outside of wind and solar power which are not significant fuel sources.
Let’s break down water usage by energy source. This is best accomplished by comparing how much water is used to generate 1 MMBTU (million British Thermal Unit). A typical household in North Texas uses 15 to 20 MMBTUs of natural gas during the winter for heating and hot water. The most intense water users are biodiesel from irrigated soybeans, which uses 14,000 to 75,000 gallons of water per MMBTU, and ethanol from irrigated corn, which uses 2,510 to 29,100 gallons per MMBTU. Obviously, much of this water is used in the irrigation of the crop, but it is water used nonetheless.
Water usage drops significantly when we move to the more conventional sources of energy: oil, natural gas and nuclear. Conventional oil uses 8 to 20 gallons per MMBTU with nuclear close at 8 to 14 gallons per MMBTU. Coal transported by slurry uses 12 to 32 gallons per MMBTU while coal with no slurry transport uses 2 to 8 gallons per MMBTU.
Surprising or not, natural gas is the most efficient option, using only 1 to 3 gallons of water per MMBTU. This includes all forms of natural gas production from conventional onshore wells, offshore wells and natural gas from shales, including the Barnett Shale.
You might wonder to yourself, “What about all the water that is used in the hydraulic fracturing process like we have here in the Barnett Shale?” As it turns out, the water used to hydraulically fracture shales does its job very efficiently by unlocking significant amounts of natural gas for every gallon of water used. The high production volume from deep shale natural gas wells sets them apart from other natural gas wells, including coal bed methane and conventional wells. From a water perspective, it is this high production that helps offset the larger volumes of water used in the hydraulic fracturing process.
The numbers explain the situation well. A typical Barnett Shale natural gas well will produce roughly 2 million to 4 million MMBTUs (million British thermal units) over its lifetime; consequently, it will use between 1.5 and 2.5 gallons of water per MMBTU. Although some of the produced water is recycled, the majority goes into deep disposal wells. However, in less than a year, a Barnett Shale gas well will produce and burn enough gas to generate more water vapor than was used to drill and produce the well, therefore making it the most efficient use of water among energy resources, excluding wind and solar, which are not significant power sources (GWPC, “Deep Shale Natural Gas and Water Use.” 2010).
The bottom line: all of our energy needs require water, so it makes sense to promote and use the most efficient user of water—natural gas. Coupled with the fact that natural gas is clean, abundant and domestic, it could be the fuel of choice moving forward, whether water is plentiful or under recommended restriction.