With all the recent scientific studies, media coverage, and policy decisions about reducing greenhouse gas (GHG) emissions, one might think that the emissions issue is the only challenge that results from our demand for electricity. Years of successful advocacy funded by philanthropists and the public concerned about climate change has resulted in action to address the sources of these emissions. President Obama announced his Climate Action Plan on June 25, 2013, that included, among other elements, a direction to the Environmental Protection Agency (EPA) to issue a draft rule for controlling carbon dioxide emissions from existing power plants. The EPA also proposed a carbon pollution standard for new power plants.
On March 28, 2014, the president directed federal agencies to study ways to cut methane emissions from various sources. At the same time, the energy efficiency, renewable energy, and clean technology industries in many states have won victories in the establishment of policies and incentives that launched a new generation of low-carbon, clean energy markets.
With carbon and methane emissions being addressed and a clean energy industry launched—and whose establishment is predicated on the need to reduce GHG emissions from electricity production—it is past time to address an equally critical, more tangible, and more urgent issue than even GHG emissions. We must recognize that reduction in water consumption associated with the entire lifecycle of electricity generation is as important as reduction of GHG emissions.
Water Availability Could Limit Generation
Reliable water supplies are a growing constraint on the generation of reliable electricity. In water-constrained areas, including most of the western U.S., difficult trade-offs are being made between power plants, agriculture, and municipal uses, as illustrated recently in Texas. The Electric Reliability Council of Texas (ERCOT) has stated that continued drought may limit electric output from power plants due to lack of cooling water for coal-fired plants.
Overall water consumption, the portion of total water withdrawals by electricity generators that is not returned to the hydrological cycle, is about 3% of national water consumption. Some fuel types and generation technologies are more water intensive than others, according to Dr. Michael Webber and his colleagues at the University of Texas. The most water-hungry technologies are second-generation nuclear, concentrated solar, coal, and natural gas steam generators. The technologies that use the least amount of water are natural gas combustion turbine, solar photovoltaics, natural gas combined cycle, and wind. Of course, energy efficiency and other demand reduction strategies require no water resources.
Webber also found that, when the water consumption analysis includes the complete lifecycle of coal and natural gas, from mining to generation and hydraulic fracturing to generation, natural gas still results in a net water savings over coal. While hydraulic fracturing might withdraw less than 1% of water on average, this use can account for greater than 25% of water at the local or watershed scale. And the water used for shale development is, in most cases, not returned to the hydrological cycle.
Since most shale development occurs in drought-prone areas of the country, losing 25% of water resources will eventually become an obstacle to further shale development.
Managing Water and GHGs
Reducing GHGs and water consumption by the electricity sector are not mutually exclusive goals. In fact, when Webber ranked fuel type and generation technology by carbon emissions and water consumption, the lowest emitters and water leanest technologies were generally the same.
In terms of lowest emissions and water consumption, solar photovoltaics and wind were the best performers. Nuclear small modular reactors also emit no carbon dioxide and use only about 50 gal/MWh of water. Natural gas combustion turbines use negligible water but produce about 1,200 lb/MWh of carbon dioxide. On the other end of the spectrum, the worst performers were natural gas steam generators, coal with carbon capture and sequestration, second-generation nuclear, and concentrating solar power, due to associated water use.
Clearly, there are options for promoting a diverse energy mix that minimizes or eliminates carbon emissions and water use. We need to continue our drive toward these technologies while also calling for their continuous improvement. Effective strategies can help accelerate fuel switching toward renewables, certain natural gas generation types, and small modular nuclear reactors. These approaches include:
■ Require shale developers to disclose the amount and source of water they use in the hydraulic fracturing process and the fate of these resources.
■ Establish policies to reflect the true value of water resources to shift resource use decisions and technology development toward conservation.
■ Engage as heavily in water conservation as we have in energy efficiency by designing innovative water-smart metering and design and adoption of incentives for conservation.
■ Invest in research and development for advanced electricity generation technologies, including deployment of small modular nuclear reactors.
■ While designing GHG emission rules for power plants, include a water conservation standard to drive choices toward conservation.
■ Incentivize shale developers to accelerate the use of water substitutes or no-water hydraulic fracturing.
While addressing GHG emissions is important, we have ignored the water issue as it relates to fuels and electricity generation for far too long. It is time that we vigorously address this issue that is already upon us. ■
—Marilu Hastings (@MitchFound) is Sustainability Program Director for the Cynthia and George Mitchell Foundation (www.CGMF.org).