Hydropower helped slash one U.S. region’s power-related CO2 emissions by 20%

Bonneville hydro

Carbon dioxide emissions from power plants in the U.S. Pacific Northwest that burn coal and natural gas totaled 45.64 million metric tons in 2020, the lowest in at least 25 years and a roughly 20% decline from 2019. (2020 was the latest year for which emissions data were available).

The data reflect emissions from electricity generation at power plants and do not account for “upstream” emissions from, for example, coal mining and gas production.

Several reasons account for the emissions decline, said Gillian Charles, senior policy analyst in the Northwest Power and Conservation Council’s Power Planning Division, which released the data. Aging and inefficient coal-fired plants are being retired, and more natural gas is being dispatched. Gas produces only about half the carbon dioxide emissions as compared to coal. Renewable (non-carbon) sources of power generation are proliferating – particularly wind and solar.

And, hydropower, the biggest source of electricity generation (about half) in the region, also plays a role. In good water years, there is more hydropower generation and lower emissions from thermal plants.

Overall, carbon dioxide emissions have trended down over the past seven or eight years, even in years with similar hydropower output. For example, emissions fell about 20% from 2013 to 2020 in very similar water years, Charles said. The ongoing decline suggests that the key factor for this trend is that less power is being generated with coal.

On average, coal generation has been declining while natural gas generation has been increasing, Charles said. Since 1995, more than 7,700 MW of new natural gas generation has been brought online in the Northwest. Overall, generation from coal and natural gas has increased over the last 25 years, but coal generation has been declining as natural gas generation increased. Since 1995, coal has accounted for about 78% of the region’s carbon dioxide emissions from power plants. In 2020, coal accounted for about 60%.

Does this trend imply that future emissions will continue to decline? Not exactly, because hydropower generation varies from year to year. During below-average water years there still will be more thermal generation to meet demand for power.

Over the next decade, some 4,400 MW of coal-fired generation is expected to be retired, Charles said. Some of this generation may be replaced with existing natural gas and new renewable resources. “As gas dispatch increases and coal decreases, this will contribute to lower future emissions from power plants that use fossil fuels,” she said.

A somewhat similar downward trend in carbon dioxide emissions has been evident across the U.S. since 2007, she said, and largely for the same reasons – more gas and renewables and less coal, even though elsewhere in the country there is less hydropower than in the Northwest.

As for the future, Charles said that early analysis indicates that 2021 emissions from electricity generation in the Northwest will likely continue to decline. But, that will depend on how the generation from retiring coal plants is replaced, how much new renewable energy comes online (thousands of megawatts are planned), and whether water years lead to more or less hydropower. The trend is a bit different for the U.S. as a whole, with emissions likely to increase thanks to an uptick in the economy as the pandemic eases.

The 1980 Northwest Power Act authorized Idaho, Montana, Oregon and Washington to develop a regional power plan and fish and wildlife program to balance the Northwest’s environment and energy needs. The council’s mission is to preserve the benefits of the Columbia River for future generations.

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