The water-energy nexus could become a collision in a warming world

 

If you thought fracking was a water-guzzling and violent way to get the oil and gas flowing from shale, then you should check out oil shale* retorting. Earlier this month, details were made public regarding an oil shale project Chevron proposes for western Colorado. Of particular note was the amount of energy and water it will take to produce 100,000 barrels of oil per day. If you think about it, it makes about as much sense as melting down five quarters to make a silver dollar.

In 2012, Chevron announced it was ceasing its oil shale research operations to focus on other things. However, the company continued to pursue water rights associated with the project. Boulder-based environmental group Western Resource Advocates wondered why, and took Chevron to court to find out. It turns out they still want to develop oil shale by strip mining the shale and then using Staged Turbulent Bed retorting, which “processes mined and crushed oil shale rock to remove the shale oil by heat transfer … accomplished by mixing spent oil shale, which has been heated (to temperatures as high as 1,000 degrees Fahrenheit) in a separate combuster, with fresh shale, causing the fresh shale to decompose and release the shale oil,” as it's described in the Chevron documents. They’re planning on cooking a bunch of rocks, in other words, and that requires water.

In order to cool and condense the steam in its turbines, the Four Corners Power Plant in northwestern New Mexico built Morgan Reservoir on an arid mesa next to the plant. Windsurfers can occasionally be seen enjoying the warmed waters of the lake. Photo by Jonathan Thompson.

Chevron says it will need 16,000 acre feet — or 5.2 billion gallons — of water per year to retort 100,000 barrels of oil per day, or about three-and-a-half gallons of water for every gallon of oil produced. An additional 8,000 acre feet per year will be needed to slake the thirst of their man camps, serve other purposes and, the other crazy part of all of this, generate energy. Chevron estimates that they’ll need a 375-megawatt natural gas fired power plant to generate the heat required to retort the shale. The power plant, in turn, will require 2,520 acre feet of water per year to operate. The Chevron documents suggest they may try to produce as much as 500,000 barrels per day, meaning they’d need about 120,000 acre feet of water in all, more than one-third of Las Vegas’ allotted share of the Colorado River.

In the documents, Chevron admits that the whole endeavor remains economically unfeasible, and thus has no plans to start mining shale anytime soon. But the details are telling because they shine a light on the water-energy nexus. That is, it takes a lot of water to produce most sources of energy. And moving and treating water requires a lot of energy, which takes a lot of water, which… well, you get the picture. As the world warms and potentially dries up, says a recent report from the Department of Energy, the water-energy nexus is likely to pose challenges, and the connection could become a full-fledged collision.


While few other energy sources are as insanely thirsty as oil shale, many of them guzzle water. Hydraulic fracturing a coalbed methane well requires as much as 350,000 gallons of water, while fracturing a shale oil or gas well can take as much as 9 million gallons. Oil wells are “flooded” with water or carbon dioxide to increase pressure and oil production, collectively gulping about 1.2 billion gallons per day. Meanwhile, oil and gas wells together “produce” about 2.4 billion gallons of water per day, some of it waste from fracking or flooding, but most of it from aquifers. It tends to be salty and contaminated with hydrocarbons, and can’t be used without treatment (which requires energy). Often, the produced water is injected back into deep wells, potentially causing earthquakes.

Far more water is withdrawn for use in thermoelectric power plants than any other use in the United States. Source: Department of Energy.

All thermoelectric power sources, from coal and natural gas plants to nuclear and even concentrated solar, require water for steam to turn the turbines, and most use water to cool and condense the steam. In fact, thermal power accounts for about 40 percent of all U.S. water withdrawals, and about 4 percent of all consumptive use (cooling water can be returned to the source, uncontaminated but warmer, which speeds evaporation). The cooler the water, the more efficient the process, so a warming world promises to make power plants less efficient and less productive.

Hydroelectric power naturally requires water, as well. Though it’s not a consumptive use, hydropower can compete with other water uses: If a reservoir is drawn down by domestic or agricultural uses, then there’s less water to run through the dam for electricity generation. Similarly, releases to meet electricity demand can deplete reservoirs, leaving less for other uses.

The dynamic works in reverse, too. The Central Arizona Project, which delivers Colorado River water via canal to Phoenix and beyond, is the single biggest electricity user in the state of Arizona, getting more than 90 percent of its electricity from coal-fired Navajo Generating Station, near the shores of Lake Powell. The Southern Nevada Water Authority, which supplies water to the greater Las Vegas metro area, is also that state’s biggest electricity user. SNWA spends nearly $45 million on energy bills each year to pump water from Lake Mead up to Las Vegas, to purify that water for drinking, to move it around the city, and to purify wastewater for reuse or for putting back into Lake Mead. Nationally, energy consumption for water treatment increased by 30 percent between 1996 and 2013, according to the Department of Energy report.

This map shows the relative water use of thermoelectric power plants in the West. Palo Verde Nuclear Generating Station near Phoenix is the biggest water consumer, but it is also the only nuke plant to use only treated wastewater for cooling purposes. Source: Western Resource Advocates.

It’s discouraging to think about — a spiraling cycle of consumption of diminishing resources that has us guzzling gallons of water for every Btu of energy we use, and burning Btus whenever we take a drink of water. Yet there’s a positive twist, as well. Every time we save a gallon of water or kilowatt-hour of electricity through efficiency or conservation, the savings are magnified via the water-energy nexus. The SNWA, for example, has taken big steps to conserve water because it has no choice, which has also resulted in a smaller power bill. Meanwhile, it’s realized big savings by making seemingly small changes: Simply by keeping structures that house pumps, for example, at temperatures that keep the equipment safe but aren’t necessarily comfortable for humans, they save more than $100,000 per year.

As water becomes more scarce due to long-term drought, it will force us to make more and more difficult choices about where our water goes: To lawns and swimming pools and our taps? Or to the power plants and gas and oil wells that heat and cool our homes and power our vehicles and, well, treat and move our water? It’s really an impossible choice. Changing the way we use energy, and water, now will keep that choice at bay.

*Oil shale ≠ Shale Oil. In a more perfect world, we would come up with a better term for both of these. Shale oil is actual crude oil that is locked up in shale formations — e.g. the Bakken, Mancos, Niobrara or Permian. The oil is released from the shale via hydraulic fracturing. I prefer the term oil-bearing shale. Oil shale doesn’t involve crude oil at all, but rather a wax like hydrocarbon that hasn’t yet become oil. We have to process it in order to complete its maturation.

Jonathan Thompson is a senior editor at High Country News. He is based in Durango, Colorado, and tweets @jonnypeace.

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