Power plant greenhouse gas emissions don’t contribute significantly to ‘dangerous air pollution’

By Daren Bakst & Marlo Lewis, Jr. of CEI. Excerpts:

"No commercial utility-scale natural gas CCS plant exists today. Only one small-scale facility was ever built: Florida Power & Light’s 40-megawatt CCS gas plant in Bellingham, Massachusetts. When the unit closed in 2005, Bellingham had a population of 15,750. A single, small, long-defunct natural gas CCS power plant provides no evidence that a 90-percent carbon capture system is adequately demonstrated for new natural gas power plants serving large metropolitan areas, industrial centers, and new data centers in an era of rising electricity demand."

"the fact that a source category contributes significantly to dangerous air pollution is no guarantee that a specific type of pollutant emitted by the category contributes significantly. In a statute requiring the EPA to take cost into account, it would not be reasonable for the EPA to regulate emissions that do not contribute significantly to dangerous air pollution." 

"It is impossible to judge whether a source category contributes significantly to dangerous air pollution without first analyzing the specific pollutants emitted by the category and their potential effects on dangerous air pollution."

"Pollutant-specific significant contribution findings were the very basis for the EPA’s decisions to list coal and natural gas power plants as CAA § 111 source categories in the first place. In August 1971, the EPA listed coal power plants because of the category’s significant contribution to three types of dangerous air pollution: particulate matter (PM), sulfur dioxide (SO₂), and nitrogen oxides (NO_X) (36 FR 15704). In October 1977, the EPA listed natural gas power plants because of the category’s significant contribution to two types of dangerous air pollution: SO₂ and NO_X (42 FR 53657).

Tellingly, the 1977 rulemaking for natural gas power plants expressly declined to propose new source standards for emissions of hydrocarbons (HC), carbon monoxide (CO), and PM. The EPA explained that, even at peak operating load, gas combustion turbine HC and CO emissions are “relatively low,” and PM emissions from the source category “are minimal” (42 FR 53782, 53783)."

"before the EPA may establish GHG emission standards for fossil fuel power plants, the agency must make the “predicate” finding that GHG emissions from such sources contribute significantly to dangerous air pollution (90 FR 25752, 25754)."

"the Obama EPA found “GHG emissions from domestic fossil fuel-fired EGUs ‘significantly contribute’ to dangerous air pollution based exclusively on the volume of GHG emissions from the source category” (90 FR 25752, 25767).

That was the Obama and Biden EPAs’ supposed “rational basis” and logic for regulating power plant GHG emissions. In fact, it was an arbitrary basis.

A volume threshold comparing domestic power plant GHG emissions to total global emissions does not tell us whether those emissions make any material difference to the “air pollution” or the danger it poses to public health or welfare. Under this volume approach, a significant contribution could be claimed even if the emissions don’t have any detectable effect on the danger level of the air pollution. Given the purpose and language of the Clean Air Act and Section 111(b), which is to protect the public’s health or welfare from dangerous air pollution, not analyzing these effects is unreasonable.

The Proposed Rule rejects “a purely quantitative measure of significance resting on the absolute volume of emissions from a source category.” Ironically, relying solely on a volume threshold would likely work in the favor of the EPA’s current argument that there is no significant contribution. After all, US electric power sector GHG emissions are steadily declining and in 2022 accounted for just three percent of total global emissions. But to its credit, the agency isn’t taking this volume-based approach.

Determining whether there has been a significant contribution requires sufficient reasoning consistent with the requirements of the statute. Section 111(b) expects the Administrator to use his judgment to figure out whether the emissions contribute significantly to dangerous air pollution. This requires assessing the effects the emissions have on air pollution that may reasonably be anticipated to endanger public health or welfare. If the emissions in no way (or in a very small way) affect the danger level from the air pollution, then it would be unreasonable to claim that the emissions contribute significantly to the dangerous air pollution."

"the first link in the chain of endangerment attributed to rising GHG concentration, the first step in determining whether US power plant GHG emissions significantly contribute to that danger is to calculate their effects on global warming.

A recent study by Brent Bennett of the Texas Public Policy Foundation offers a reasonable estimate based on conservative inputs.

• Bennett uses the US government’s standard climate-policy impacts calculator, a model called MAGICC. He runs MAGICC with its mid-range climate sensitivity estimate, namely, that each doubling of atmospheric GHG concentration increases global average surface temperatures by 3.0°C. Note, recent research suggests sensitivity “values between 1.5°C and 2°C are quite plausible.”
• He uses the UN climate panel’s mid-range baseline emission scenario, known as SSP2-4.5. Recent research suggests the world is on a lower emissions path.
• He assumes the US global share of GHG emissions (currently 13 percent) will hold steady through the end of the 21^st century, even though the US share has been declining for the past 25 years.  

Under those assumptions, MAGICC estimates that eliminating all US power plant CO₂ emissions by 2030 would avert 0.015°C of warming by 2050. That is 10.6 times smaller than the National Ocean and Atmospheric Administration’s margin of error (+/-0.08°C) for measuring changes in global average surface temperature.

A temperature effect below margin of error is too small to be detected or verified. The US power sector’s contribution to global warming is, therefore, insignificant.

But if the warming effects of US power sector GHG emissions are undetectably small, even more so are the putative second and third order effects of those emissions. Therefore, US power sector CO₂ emissions do not contribute significantly to dangerous air pollution."