EPA’s ACE rule for affordable clean energy: what next?

16 November 2018

31 October 2018 saw the close of the comment period for the US EPA’s proposed Affordable Clean Energy rule. This opens the way for the EPA to issue a final ACE rule, which is expected to happen in the first quarter of 2019. Kyle Danish and Stephen Fotis, Van Ness Feldman, Washington, DC, USA

On 21 August, 2018, the Environmental Protection Agency (EPA) issued a proposed rule pursuant to section 111(d) of the Clean Air Act (CAA) that would establish emission guidelines for states to develop plans to limit carbon dioxide emissions from existing fossil-fired power plants. The proposed Affordable Clean Energy (ACE) rule would replace the previous administration’s 2015 Clean Power Plan (CPP), which EPA is proposing to repeal (in a separate rulemaking) on the grounds that the CPP exceeded the agency’s authority under the CAA.

Core elements of the proposed ACE rule include:

  • a determination of the best system of emission reduction (BSER) for CO2 emissions from coal-fired power plants;
  • a list of “candidate technologies” states can use when setting CO2 performance standards for affected plants;
  • a new preliminary applicability test for determining whether a physical or operational change made to a power plant may be a “major modification” triggering New Source Review (NSR); and
  • new implementing regulations for establishing emission guidelines under CAA section 111(d).

Section 111(d)

As already noted, EPA is proposing the ACE rule pursuant to section 111(d) of the CAA. This section directs EPA to promulgate regulations establishing a federal–state process for setting standards of performance limiting emissions from existing sources for pollutants not otherwise regulated in other specified sections of the CAA. Implementing section 111(d) is a three-step process. First, EPA issues a “guideline” for states to use in developing compliance plans that include standards of performance for stationary sources within a particular source category. The guideline identifies what EPA determines is the BSER for the relevant sources within the source category. Second, each state submits a plan to EPA that includes standards of performance for the covered sources in the state. Third, EPA approves or disapproves of the state plans. If a state fails to submit an approvable plan, the CAA requires EPA to impose a federal plan.

Proposed BSER determination

EPA is proposing to define BSER for CO2 emissions from existing coal-fired power plants as heat-rate efficiency improvements based on a range of “candidate technologies.” This “inside the fence” BSER determination reflects a different approach from that used in the Clean Power Plan. The CPP determined the BSER for power plants based on reductions achievable not only through inside-the- fence measures such as heat rate improvements but also through shifting of generation from higher-emitting to lower-emitting or zero- emitting plants. As noted above, EPA has proposed to find that such an “outside-the-fence” approach to determining BSER exceeds the agency’s authority under the CAA.

EPA has identified a list of the “most impactful” heat rate improvement measures (see table below). EPA is proposing that this list serve as the “candidate technologies” or “checklist” of BSER technologies, equipment upgrades, and best operation and maintenance practices for coal-fired power plants. These candidate technologies (described in more detail in the proposed rule published in the Federal Register) are:

  • neural networks/intelligent sootblowers;
  • boiler feed pump overhaul/upgrade;
  • air heater and duct leakage control;
  • variable frequency drives on induced draft fans and boiler feed pumps;
  • steam turbine blade path upgrade;
  • redesign/replacement of economiser; and
  • improved operation and maintenance practices focused on heat rate improvement, eg improved steam surface condenser cleaning and improved condenser tube cleaning.

States are expected to consider the above technologies in establishing standards of performance for existing coal-fired power plants. EPA is proposing that performance standards will set a specific allowable emission rate expressed as a pounds of carbon dioxide per MWh-gross rate for each affected unit based on the application of the appropriate candidate BSER technologies to each unit. 

EPA explains in the proposed rule that it does not have sufficient information to make a BSER determination with respect to heat rate improvements at natural-gas-fired simple cycle units or combined cycle plants. The agency is soliciting comment on this issue. Previously, EPA determined that heat rate improvement measures at natural gas fired combustion turbines would not be considered BSER because such measures cannot provide meaningful reductions at reasonable cost.

State compliance plans

The proposed rule would provide each state with broad discretion in establishing specific performance standards for particular plants. The proposal also allows state plans to rely on emission averaging and trading among affected coal fired units at a particular plant. However, EPA has proposed that state plans should not be allowed to incorporate averaging and trading among different plants, such as a state-wide or interstate cap-and-trade programme. Nor will any credit be given for CO2 emissions reductions achieved through increased generation of renewable energy or gas-fired generation not covered under the section 111(d) regulatory programme. The proposed rule explains that such an approach would be inconsistent with EPA’s proposed “inside-the-fence” interpretation of BSER under section 111.

Permitting under NSR programme

EPA is proposing revisions to the NSR (New Source Review) permitting programme to make it easier for power plants to adopt heat rate improvements without triggering NSR obligations. The NSR programme is a preconstruction permitting programme. An NSR permit is required not only before construction of a new major stationary source; it is also required before modifying an existing major source if the modification will result in a significant emissions increase of any NSR-regulated pollutant. Projects that cause a significant increase in annual emissions may trigger onerous NSR permitting requirements, which include installation of state-of-art emission control technologies, prescriptive air quality modelling, and extensive public notice and comment procedures.

To avoid widespread triggering of NSR permitting requirements from heat rate improvement projects undertaken by affected coal fired plants, EPA is proposing to amend the NSR regulations to include an hourly emissions increase test. Under the proposed revisions, a non- excluded physical or operational change to an electricity generating unit would only trigger NSR if the change resulted in an increase in the unit’s maximum hourly emissions rate under procedures proposed in the ACE rule, as well as a significant emission increase in annual emissions under the current NSR regulations.

As drafted, the proposed maximum hourly emission increase test would be available to any electricity generating unit, including natural gas-fired units that would not be subject to regulation under section 111(d).

States with approved NSR programmes would have the option but would not be required to adopt the hourly emission increase test ultimately promulgated as part of the NSR provisions in their SIPs (State Implementation Plans). For those states with delegated NSR programmes that are acting on behalf of EPA, the NSR permitting process would have to include any changes that are ultimately made to the federal NSR provisions as they would be administering the federal programme.

EPA is proposing that the potential revisions to the NSR permitting program are severable from the rest of the ACE rule.

Implementing regulations for emissions guidelines under Section 111(d)

The proposal revises the general implementing regulations for section 111(d) that govern how EPA issues emission guidelines, and how and when states develop and submit their plans. These changes would apply for all future section 111(d) rules. Proposed changes include the following:

  • Timing: The proposal updates timing requirements regarding submission of state plans and EPA action on those state plans. 

State submissions: EPA is proposing to give states three years to develop state plans. The existing implementing regulations provide nine months.

EPA action: The proposal would allow EPA 12 months to act on a complete state plan submittal. The existing implementing regulations provide four months.

Federal plan: The proposal would allow EPA two years to issue a federal plan after a finding of a state’s failure to submit an approvable plan. The existing implementing regulations provide six months.

  • Criteria for state plans: The proposal has completeness criteria for state plans that include administrative materials and technical support for state implementation of the plan. EPA would have six months to determine completeness and would make that determination by comparing the state’s submission against the completeness criteria.
  • Variance provisions: The proposal provides greater flexibility to states to adopt plans that include variances from the EPA guidelines that will allow, among other things, states to take into account the remaining useful life of the unit and other relevant factors in establishing a performance standard for a particular affected unit.

Impacts of EPA proposal

According to EPA, the proposed ACE rule would reduce the compliance burden by up to $400 million per year when compared to the CPP. EPA estimates that the ACE rule could reduce overall 2030 CO2 emissions by up to 1.5% from projected levels without the CPP. It is envisaged that the new rule will be applicable to around 600 coal fired units at some 300 facilities across the USA.

Next step

The proposed ACE rule was published in the Federal Register on 31 August 2018, triggering a 60 day period for comment, including a public meeting, which was held on 1 October. The comment period closed on 31 October, with no major changes expected to be implemented as a result The next step is expected to be the issuing by EPA of a final rule, possibly in the first quarter of 2019. 

Emissions trends in the USA (source: EPA)
CPP vs ACE, the EPA’s view

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