Last month, a landmark study by NASA researchers provided one of the grimmer takes on the effects of climate change to date. The lead authors Benjamin Cook, Toby Ault, and Jason Smerdon predict an unprecedented rise in drought risk in the Southwest and Central Plains of Western North America as we approach the later half of the 21st century. Specifically, the researchers calculate that high emissions – and a warmer base – increase the risk of multi-decade mega-droughts more than six-fold compared to the historical period, 1950-2000. The research, combined with population trends, suggests the United States will require high levels of adaptation and forward action not yet demonstrated. One area in particular is of critical importance: the water-energy nexus.
Simply put, the energy industry is water-intensive and the water industry is energy-intensive. Each year, roughly 150 trillion gallons of freshwater are withdrawn for energy production, or about 15 percent of the world’s total water withdrawal. Of those 150 trillion gallons, approximately 11 percent – 17 trillion gallons – are consumed, or permanently withdrawn from its source. By 2035, freshwater withdrawals are expected to hit 185 trillion gallons, while the consumed volume nearly doubles to 32 trillion gallons.
At a share of roughly 38 percent, thermoelectric power generation is responsible for the bulk of annual freshwater withdrawals in the United States. Coal, which forms the backbone of US electric generation capacity, is the single biggest user. In some of the most arid regions, coal plants account for more than 90 percent of the water consumed for power generation each day.
Thus far, the debate around coal has focused primarily on its carbon emissions, and not unfairly so – coal-fired electricity generation emits approximately 1,575 million metric tons of CO2 annually, or nearly one-quarter of the US total. But – barring change – water, in tandem with emissions regulations, will sign coal’s death certificate.
Coal is already on the decline – EPA mandates are putting pressure on coal to get clean or get out. However, those same mandates are increasing the burden on local water supplies. A move toward closed-loop cooling and carbon capture and storage technologies is projected to increase water consumption by about 24 percent. On a cubic meter per megawatthour basis, water consumption intensity for clean coal – with carbon capture – is nearly three times higher than natural gas combined cycle generation.
The vulnerability is real and within the next decade the US Department of Energy projects that water conflicts will seriously affect approximately 5 percent of coal-fired generation capacity.
What does this mean for oil and natural gas, and what can we do about it?
For oil, not much. The fuels don’t compete in the power sector, though falling prices are thought to be a boon for coal miners. Instead, the focus is on gas – the industry anointed bridge fuel.
Stretching back two years, skyrocketing gas capacity additions have characterized the electric power market. By 2035, natural gas generation should overtake coal generation as the top source of electricity. Looking at the water-energy nexus, gas is a win-win. Combined cycle generation is the most efficient form of electric power generation – both thermally and in terms of water use. While this isn’t a groundbreaking revelation, it’s an idea that – combined with the aforementioned and impending water constraints – deserves more immediate and adaptive policy responses.
Looking abroad, Chinese lawmakers are on the cutting edge of water-minded energy legislation. While the country is still years away from a meaningful reduction in coal-fired generation and carbon emissions, it’s response to water scarcity should be noted.
85 percent of China’s coal lies in the water-poor north. In response, the nation mandated the use of air-cooled condensers. At the onset of 2014, air-cooled coal-fired generation accounted for 16 percent of the nation’s 801 gigawatts of coal capacity. As a result, China’s average thermoelectric power water consumption fell 41 percent between 2000 and 2010.
In the US, air-cooled systems comprise less than one percent of the nation’s coal fleet and just 3 percent of the total power generating mix.
It’s not a long-term fix, but coal was never the long-term answer.