Drought leads to higher carbon emissions from utilities in the West, study finds
Energize Weekly, January 2, 2019
Drought across the West between 2001 and 2015 led to reduced hydropower and a 10 percent increase in greenhouse gas emissions as utilities shifted to fossil fuel generation, according to a study by Stanford University researchers.
In total, drought conditions led to 100 million tons of carbon dioxide (CO2) being emitted during the 15-year period across 11 western states, the study, which was published in “Environmental Research Letters,” calculated.
The largest CO2 increase occurred in California, an estimated 51.3 million tons over the 15 years, followed by Washington, 21.8 million tons, Oregon, 13.5 million tons and Wyoming, 6.9 million tons.
“These drought-induced emissions are large enough to pose challenges to western states’ progress towards their CO2 emissions targets,” the researchers said.
The study also documented an increase of 45,000 tons of sulfur dioxide (SO2) and 57 tons of nitrogen oxides (NOx) across the region.
Some of the biggest SO2 increases were in Colorado, Utah, Washington and Wyoming. Large NOx increases were recorded for California, Colorado, Oregon, Utah, Wyoming and Washington.
Hydropower provided 23 percent of the West’s electricity in 2015, and thermoelectric power plants, which need water for cooling, generated 62 percent of the region’s power.
The research found that droughts led to an increase in electricity generation from natural gas in California, Idaho, Oregon and Washington and an increase in coal-fired generation in Colorado, Montana, Oregon, Utah, Washington and Wyoming.
Drought-induced emission accounted for 7 percent to 12 percent of total emissions in Oregon, Washington, California and Idaho.
The study calculated the decline in stream flows across the region during droughts, which in turn decreased hydro baseload electricity generation.
Droughts are often accompanied with heat waves, and that increases electricity demand for air conditioning and requires the use of peaking plants, the last and most expensive generation put online.
Heat waves can also increase stream-flow temperatures, which impair the cooling capacity of thermoelectric plants and reduce generating capacity.
“The increased use of fossil fuel power plants for peak generation induced by droughts may last from months to years, which can lead to significant increases in pollutant emissions from the electricity sector,” the researchers said.
Previous studies found that during the recent California drought, thermoelectric power plants in the Western Interconnection, the regional grid, that use municipal water, surface water, once-through cooling and cooling pounds were most sensitive to water scarcity.
Wyoming hydropower posted the most negative drought impact with an 18 percent decline over non-drought periods. Washington and Colorado saw a 17 percent drop in generation followed by Idaho at 15 percent and California at 12 percent.
While natural gas-fired generation saw big increases during drought in Washington, up 38 percent and Oregon, a 17 percent increase, natural gas generation joined hydro in declining in Colorado and Wyoming.
Coal-fired generation, however, was up 8 percent in Colorado, 12 percent in Montana, 9 percent in Oregon and 8 percent in Wyoming. Coal-fired generation, which is a small part of generation in Washington, was also up 38 percent in that state.
Electricity is traded across the Western Interconnection. During drought, in-state generation surpluses dropped sharply for Washington and Oregon, indicating that hydropower was not being exported.
At the same time, generating surpluses were noted in Wyoming, up 26 percent, and Montana, up 17 percent. “The pattern of drought response suggests that generation from coal increases in Wyoming and Montana in order to export electricity to surrounding states that experience drought-induced declines in generation,” the study said.
“Climate change could alter the pattern of drought frequency and severity in future decades, particularly during the spring and summer due to reduced snowpack,” the study said. “Regional drought-induced emissions are likely to continue at their historical levels (absent other interventions such as investments in renewable technology and thermoelectric power plants with more efficient cooling systems and emissions controls).”