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Landfill methane reductions in Colorado

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  Update: In its December 2025 meeting, the Colorado Air Quality Control Commission approved the measures described on this web page. Read the CDPHE press release.

Overview

The CDPHE Air Pollution Control Division proposed a rule to the Air Quality Control Commission in April 2025 to reduce methane pollution from municipal solid waste landfills. The commission held the rulemaking hearing in August 2025 and decided to reconvene in December 2025 for further discussions. During its December 2025 meeting, the commission approved the proposed rule.

Municipal solid waste landfills are significant sources of methane, which is a powerful greenhouse gas that contributes to climate change. Colorado identified reducing methane pollution from landfills as a near-term action to reduce greenhouse gas emissions in the state’s Greenhouse Gas Pollution Reduction Roadmap 2.0.

In October 2024, the Colorado Air Quality Control Commission adopted changes to the state’s greenhouse gas reporting requirements that apply to municipal solid waste landfills. The data collected through updates to Regulation 22, Part A will complement the new landfill methane reduction requirements, allowing Colorado to track methane reductions over time.
The methane reduction rule requirements apply to municipal solid waste landfills based on the amount of waste currently in a landfill (“waste in place”). The rule includes measures such as:

  • A stricter emissions control threshold than federal standards, requiring more landfills to install gas collection and control systems.
  • Requirements for closed landfills with emission combustion devices, like flares, to install biofilters when the combustion devices are removed, allowing for further control of methane emissions.
  • Additional methane monitoring, allowing tools like satellite imaging and plane sensors to identify large emission sources at landfills, and the use of approved alternative monitoring technologies by landfill operators for periodic methane monitoring.
  • A phased ban on open flares, replacing them with enclosed flares to enable performance testing and ensure methane emissions reductions.
     

Public participation meetings

Landfill Methane Rule

The division hosted three online public information meetings in late 2024 and early 2025 on the rule proposal. During these sessions, the division:

  • Shared the proposed rule’s concept and requirements.
  • Provided the opportunity for public feedback.
  • Answered questions.

Each meeting was recorded and hosted online.

The division continually seeks public input before proposing new or updated rules. Explore the division's upcoming public participation opportunities.

Technical working group (August-November 2024)

The division convened a technical working group in August 2024 to help support and inform the rule proposal. The technical working group focused on:

  • Evaluating methodologies and best practices for reducing landfill methane emissions beyond federal requirements.
  • Assessing enhanced methane monitoring and control requirements for landfills.
  • Operating and maintenance practices and considerations for landfill gas collection and control systems.
  • Streamlining reporting requirements for landfills.

The technical working group meetings were open for live public listening and also recorded. The meetings primarily focused on technical discussions among the working group members.

Each meeting was about two hours long and hosted online.

The division convened a technical working group with diverse expertise in:

  • Landfill regulatory development and oversight.
  • Methane emission reduction methods.
  • Landfill operations and management. 

The group's expertise helped inform balanced and comprehensive recommendations for landfill methane pollution control. The technical working group members graciously volunteered their time:

  • Aaron Byrne, Summit County Landfill.
  • Brian Dodek, Waste Management.
  • Tom Frankiewicz/Ellie Garland, Rocky Mountain Institute.
  • Melissa Green, Weaver Consultants.
  • Paul Schlicht, CDPHE Hazardous Materials and Waste Management Division.
  • Dana Podell, CDPHE Air Pollution Control Division.
  • Nancy Seidman, Regulatory Assistance Project.
  • Steve Derus, Republic Services.