EPA flips on Trump-era plan to exempt pyrolysis from CAA regs


Jun. 05, 2023

The Environmental Protection Agency has announced that it has withdrawn a provision from its proposed rule for Other Solid Waste Incineration Units to remove an exemption for pyrolysis and combustion units. These units are often used to recycle plastics or other hard-to-destroy chemicals.

Regulatory background

  • Section 129 of the Clean Air Act (CAA) requires that the Environmental Protection Agency (EPA) develop and adopt New Source Performance Standards (NSPS) and emissions guidelines for the waste management industry. These regulations apply to new sources of emissions in the industry (under the NSPS) as well as procedures for states to submit plans for implementing emissions guidelines for existing sources of emissions. For the waste management industry, these are often solid waste incineration plants or sewage sludge treatment plants. The section also includes Other Solid Waste Incineration (OSWI), which covers sources that differ from traditional solid waste incineration plants.
  • The EPA first enacted NSPS and emissions guidelines for OSWI units on December 16, 2005. Since that time, the NSPS and emissions guidelines for OSWI units have been amended several times, with the EPA most recently proposing new standards on August 31, 2020.
  • Under the 2005 regulations, and in all enacted regulations since that point, the agency has stated that “pyrolysis/combustion units” are within the ambit of OSWI. The agency has defined these units as “two chamber incinerators with a starved air primary chamber followed by an afterburner to complete combustion,” which are often used to recycle plastics or other hard-to-destroy chemicals. Pyrolysis and gasification generally begin with solid or semi-solid feedstocks, which are then heated to break down the product into energy, fuels, or chemical commodities. Pyrolysis has been floated as an option to break down per- and polyfluoroalkyl substances (PFAS) in biosolids or other solid waste, with at least one 2022 study finding a high level of removal efficiency through exposing the biosolids to pyrolysis.
  • As plastic waste recycling continues to grow, the agency has received inquiries on the applicability of the OSWI standards to pyrolysis/combustion units based on differences in the process or feedstock for the units. The CAA does not define pyrolysis/combustion units, and the agency noted that it believed there was “considerable confusion among the regulated community” over the scope and applicability of the regulations.
  • In August 2020, the EPA proposed to remove the reference to “pyrolysis/combustion unit” from the definition of “municipal waste combustion unit” under OSWI, which would remove the units from CAA regulations. The EPA received a significant number of comments on this proposed revision, and responded in September 2021 with an advanced notice of proposed rulemaking (ANPRM) that would develop specific regulations for pyrolysis/combustion units.
  • The 2020 rule had hinged on a proposal that pyrolysis units do not work via combustion (due to the absence of oxygen in the unit during heating) and therefore would not be covered by the OSWI regulations. The comments against this rule heavily argued that pyrolysis (and gasification) are combustion technologies, and therefore should be regulated under the OSWI rule. The EPA’s reasoning for issuing the 2021 ANPRM was to gather information and form a more comprehensive understanding of pyrolysis/combustion units to aid in the development of future regulations.

EPA withdrawal of proposed exemption

  • On June 5, 2023, the EPA published a notice in the Federal Register that it was withdrawing the proposed “municipal waste combustion unit” definition that would have removed pyrolysis/combustion units from the OSWI regulations. The agency explained that it had reviewed information gathered through the 2021 ANPRM comment process and is using that information in developing a finalized OSWI rulemaking package. Based on discussions the agency had with stakeholders and its own review of the comments on the 2021 ANPRM and 2020 proposed rule, the agency determined that pyrolysis is a “complex processing that is starting to be used in many and varied industries.”
  • Reading into the notice, it appears that the withdrawal of the proposed change is more of a stopgap method, rather than the EPA’s plan for the future. The agency noted that it would require “significant time and personnel” to analyze the comments and evaluate all current information to achieve both technical and regulatory understanding of the pyrolysis process. The agency noted that it did not believe it would be “appropriate” for these sources to become unregulated during the process under the 2020 rule, especially if the agency eventually determined that regulation is needed for these units. Therefore, the agency announced that it will continue with developing the agency’s OSWI rulemaking with the pyrolysis/combustion units as part of the OSWI regulations to prevent a regulatory gap and protect public health.

Impact of the change

  • By the EPA’s own admission, it is unlikely that this is the “end of the road” for pyrolysis/combustion unit-specific regulations. The agency clearly stated that it was likely to further regulate these units on their own, but that it has not yet had the time or personnel to develop these regulations. As different pyrolysis feedstocks and processes may seriously impact the emissions of the unit, it is likely that more fully developed pyrolysis/combustion unit regulations will be on their way, but the agency’s explanation makes it seem likely they are at least several years away.
  • The current withdrawal means that the units will stay regulated when the agency releases the final version of the OSWI regulations. In the future, the agency may deploy regulations that move pyrolysis/combustion units into their own section, but for the foreseeable future these units will be regulated under the OSWI standards.

To contact the author of this analysis, please email Walker Livingston.
To contact the editor of this analysis, please email Patricia Iscaro.

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