On June 19, 2019, the Environmental Protection Agency (EPA) issued its final "Affordable Clean Energy Plan," (ACE), which represents the current Administration's attempt to tackle greenhouse gas (GHG) emissions from the electric power sector. At the same time, the EPA repealed the Obama Administration's signature climate change regulation, the "Clean Power Plan," and with it, more stringent requirements for curbing GHG emissions from coal-fired power plants. These were formally published in the Federal Register on July 8, 2019.
Both regulations are meant to carry out EPA's obligation under Section 111(d) of the Clean Air Act to regulate air pollution from existing stationary sources. In December 2009, the EPA made an "endangerment finding" that found that greenhouse gas emissions threaten health and the human environment, triggering its responsibility under Section 111(d).
The Clean Power Plan (CPP), carrying out that responsibility, was proposed in June 2014 and finalized in August 2015. With an overall goal of reducing CO2 emissions from the electric power sector by 32% over 2005 levels by 2030, it required states to meet specific CO2 reduction targets by either (a) increasing the generating efficiency of coa-fired power plants, (b) substituting natural gas for coal, or (c) substituting renewables or other low-carbon sources of power. It also required the states to require any remaining coal-fired power plants within their borders to limit their CO2 emissions to 771 pounds of CO2 per megawatt hour (MWh) of electricity producted (for stationary combustion turbines) or 1305 pounds of CO2 per MWH (for electric generating units).
The CPP never went into effect, as it was subject to instant legal attack, and was stayed by the Supreme Court in February 2016.
The ACE is the Trump Administration's replacement for the CPP. It contains two major changes from the CPP's approach: First, it dispenses altogether with the requirement that states reduce CO2 emissions from the electric power sector by 32% by 2030. Second, it dispenses with the specific efficiency improvements for existing electric power plants called for in the CPP, calling only on the states to require existing coal-fired power plants within their borders to impose some form of heat-rate reduction to bring down the amount of CO2 they emit per MWh of electricity produced.
The first change will have little effect on US CO2 emissions, as emissions were already down 28% compared to 2005 levels by 2017, and are projected to be down 38%-42% over the next few years.
The second change will have more of an impact, as the US will lose an opportunity to impose a strict limit on CO2 emissions from remaining coal-fired power plants, which would have driven emissions down further. This will also mean that co-benefits, in the form of reduced conventional air pollutants that would have been reduced as a side effect of the efficiency improvements, will not be realized.
The cost-benefit analysis accompanying the final ACE rule predicts that its looser heat-rate reduction requirements will still reduce CO2 emissions by 11 million tons compared to business as usual. This is far less thant the reductions that would have been realized under the CPP--not to mention the 13-30 million tons of CO2 emissions reductions predicted when EPA issued the proposed ACE rule last year.
Environmental and public health groups have universally condemned the final ACE rule. As soon as the rule was published in the Federal Register on July 8, 2019, the American Lung Association and the American Public Health Association, represented by the Clean Air Task Force, filed the first lawsuit challenging the rule.