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U.S. EPA’s Revised Cross State Air Pollution Rule (CSAPR) Update and Why Non-EGUs Should Care About CSAPR

Posted: November 10th, 2020

Authors: Amy M.  Rich H. 

U.S. EPA recently proposed a revised update to CSAPR to address interstate pollution transport obligations for compliance with the 2008 ozone National Ambient Air Quality Standard (NAAQS).  This action is being taken in response to a court action that remanded their 2016 CSAPR update rule.  If you’re not familiar with CSAPR, it covers 22 eastern states and includes nitrogen oxides (NOx) emissions budgets for each of those states in order to limit the effects of downwind transport of NOx emissions on ozone concentrations.  Currently, those budgets and the associated trading program apply only to electric generating units (EGUs) but several recent court decisions related to interstate transport have stated that non-EGU sources of emissions should also be considered as part of a strategy to eliminate a state’s significant contribution to downwind nonattainment.

U.S EPA is proposing that EGU’s will need to do more starting in 2021 to help downwind states achieve compliance with the 2008 NAAQS. Specifically, EGU’s equipped with selective catalytic reduction (SCR) must operate them throughout the 2021 ozone season,  and in some cases EGU’s may be required to undertake air pollution control projects including the installation of low-NOx burners or overfire air (OFA) to improve their level of NOx control by the start of the 2022 ozone season. While EPA is proposing to find that only EGU’s will need to take these steps, they are requesting comments on what several types of non-EGU sources (think glass furnaces, cement kilns, large internal combustion engines, and industrial boilers) can do to reduce NOx emissions in future years. Additionally, EPA will cover all source types when it addresses the 2015 ozone NAAQS in a future action.

Short History of NOx Transport Rules

Clean Air Act (CAA) Section 110 contains language known as the “good neighbor provision” that requires states to prohibit emissions that will contribute significantly to nonattainment or interfere with maintenance of the NAAQS in any other state.  In the event that a state does not establish its own approved State Implementation Plan (SIP) to address this provision, the U.S. EPA develops a Federal Implementation Plan (FIP), which it has done with CSAPR.  Many studies have established that ozone transport occurs on a regional scale over much of the eastern U.S., so historically, U.S. EPA has established limitations on NOx emissions from large sources (primarily electric utilities) using cap and trade programs in order to reduce interstate transport and improve air quality.

Before CSAPR was an acronym floating around in a regulator’s head, we saw the NOx SIP Call in the late 1990’s/early 2000’s.  This rule required states to establish NOx budgets and trading rules for both EGUs and fossil fuel-fired industrial boilers at least 250 million British thermal units per hour (MMBtu/hr) in size.  Sources lived under these budgets until those rules were replaced by the Clean Air Interstate Rule (CAIR), which only covered emissions from EGUs.  CAIR was then replaced by CSAPR effective January 1, 2015.  The October 2016 CSAPR update finalized requirements for 22 states in order to reduce interstate transport and allow for compliance with the 2008 ozone NAAQS.  However, that rule was remanded to U.S. EPA because the rule analyzed 2023 compliance, not 2021 compliance.

What Analysis has EPA Done for This Update and What Action is EPA Proposing to Take for 2021?

U.S. EPA is now proposing to further limit “ozone season” (May 1 through September 30) NOx emissions from EGUs in 12 states (IL, IN, KY, LA, MD, MI, NJ, NY, OH, PA, VA, WV) and to adjust the states’ budgets for each ozone season thereafter until air quality projections demonstrate resolution of downwind attainment or maintenance problems for the 2008 ozone NAAQS.  They found that the existing budgets in 9 states (AL, AR, IA, KS, MS, MO, OK, TX, WI) are sufficient such that they do not significantly contribute to downwind attainment or maintenance under their current programs, and thus do not need to take any further action.
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The basis of U.S. EPA’s determination is a four-step framework.  First, they identified the downwind receptors that are expected to have problems attaining or maintaining the NAAQS.  Second, they determined what states are significantly contributing to the problem and have established that a 1 percent contribution (0.75 ppb) is significant. U.S. EPA justified the use of 1% because that threshold “captures a high percentage of the total pollution transport affecting downwind receptors”. Third, for the states that were found to significantly contribute to downwind attainment or maintenance problems, they identified the emissions that significantly contribute to the problem.  Fourth, they determined the necessary emissions reductions measures in the significantly contributing states.  Note that U.S. EPA must be careful not to require “over-control” of emissions by a particular state, only what is necessary to reduce its impact to below the level that is significant.

The first step was completed using a combination of modeling and ambient monitoring data to predict ozone concentrations in 2021.  Given the time constraints, U.S. EPA did not completely update their analysis performed for the 2016 rule.   Ultimately, four monitors, two of which were considered nonattainment and two of which were considered maintenance, were identified for review of upwind contributions (3 in CT and 1 in TX).

In performing the modeling, U.S. EPA used the newest modeling platform, but used emissions based around the 2014 National Emissions Inventory (NEI) supplemented by CEMS data for 2016 for those EGU’s that were in the 2014 NEI. The most current version of the NEI is 2017. Three model scenarios were run: 2016, 2023, and 2028. The 2023 and 2028 model runs were based on projected emissions built on the 2016 data set and took into account announced retirements, state and federal regulations scheduled to come into effect between 2023 and 2028, planned air-pollution control projects at existing facilities, etc.

The initial modeling run used the 2016 emissions data and was used to ground truth the accuracy of the data set by comparing the results to actual monitored concentrations. The results found that the data set produced concentrations within the accepted range of accuracy. The projected concentrations in 2021 were produced by running the 2023 scenario and making a linear interpolation between the 2016 results and the 2023 results. The contributions and significance test for each state was calculated by determining the model-predicted concentration in 2023 and adjusting them to represent 2021. Sources were “tagged” by group: Each state was a tag, as were different types of emissions: anthropogenic, biological, fires, EGU, non-EGU, etc. The concentrations from specific sources within a state were not reported.

The results of this modeling determined the 12 states that required further review and aided in the determination of the proposed revised state NOx budgets.

The agency has historically focused on EGUs for emissions reductions because past work indicates that this sector is a large source of NOx emissions and that there are cost-effective means of reducing NOx emissions.  For this proposal, they identified a control strategy for EGUs that reflects optimization of existing controls for 2021 and beyond and installation of new controls in future years.  (Note that although their analysis is based on assuming certain sources will optimize or apply certain controls, the ultimate requirement is to stay below a certain number of tons of NOx emissions during the ozone season.)  U.S. EPA did a cursory evaluation of 150-tpy non-EGU sources to determine if any near-term emissions reductions should be required, but do not generally have the quality or quantity of information for industrial sources available that would make such an evaluation robust.  Their past work generally indicates that emissions reductions are not as cost effective for industrial sources.  However, read on to find out what information U.S. EPA is seeking to improve their analysis (either for this rule or a future rule that addresses compliance with the 2015 ozone NAAQS).

What Comments is EPA Seeking for non-EGU Industrial Sources?

Although they are not proposing to establish requirements for non-EGU sources in the near term, U.S. EPA is seeking comment on its analysis of non-EGU sources and whether there are grounds to find non-EGU emissions reductions necessary.   The agency also analyzed and is specifically requesting comments on the NOx emissions reduction potential for glass furnaces and cement kilns.  Comment is also requested on the feasibility of further controlling NOx from large internal combustion engines (e.g., those at natural gas compressor stations) and large industrial boilers, including combustion optimization and low-NOx burners.  However, don’t think you are out of the woods because you don’t operate any of those sources, because comments are also requested on whether there are other sources or sectors that could achieve cost-effective NOx reductions and what they would be.  The question is also asked whether cost-effective reductions could be achieved by replacing older equipment or fuel switching.  (Several facilities made those changes in order to comply with Boiler MACT.)

Keeping in mind that the old NOx SIP Call regulated large industrial boilers, comment is also requested on whether large non-EGU boilers and combustion turbines that would have been covered by that program should be required to employ controls equivalent to the emissions level achieved by low-NOx burners.  Given that most new gas-fired units employ low-NOx burners, this should only be a concern for older units that may not have upgraded their burners already or are not located in a state that already has this requirement.  Comment is also requested on whether states should be allowed to include former NOx SIP Call industrial units in the revised CSAPR update trading program (just when you thought you were out, they could pull you back in).

What’s Next?

Comments on the proposed rule are due December 14, 2020.  If you own or operate a facility with NOx emissions greater than 150 tpy or one of the source types that U.S. EPA called out specifically as possible candidates for NOx reductions after 2021, you should review the proposal and either work with your corporate environmental group or your industry association to provide comments.  Better information on available controls and the costs of those controls will be critical to the outcome of this and related future actions.  The agency will review comments and must finalize the rule by March 15, 2021 so that the initial required reductions will be achieved during the 2021 ozone season.  However, as mentioned above, this CSAPR update only addresses the 2008 ozone NAAQS, so stay tuned for a future action that addresses the 2015 NAAQS or a state’s petition to U.S. EPA to impose additional controls on upwind sources not covered by CSAPR.  ALL4 is assisting with comment development on the proposal so feel free to reach out to Amy Marshall or Rich Hamel for more information.
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