Denver (Dec. 18, 2025): The Colorado Air Quality Control Commission has adopted a new standard to reduce methane, a greenhouse gas that contributes to climate change, and other harmful pollutants from municipal solid waste landfills. The measures align the state with leading practices already adopted in other parts of the country and moves the Centennial State one step closer to its goal of 100% net-zero greenhouse gas emissions by 2050.
“Colorado prides itself on sustainable regulations, and this progress reflects the extensive collaboration and commitment of our partners in advancing state climate goals,” said Michael Ogletree, the senior director of the state’s air quality programs. “This new standard will significantly reduce methane emissions using proven technologies and climate-smart practices. Strong actions like this help address climate change while protecting our environment, public health, and state economy.”
In addition to methane, the standard will lower emissions of harmful pollutants, such as benzene and hydrogen sulfide, which are often released from landfills.
The commission approved the creation of Colorado Air Quality Control Commission Regulation 31, which creates new emission control and monitoring measures for municipal solid waste landfills. These types of landfills contain household and commercial waste and primarily emit methane as organic matter breaks down.
“Carbon dioxide equivalent” is a common metric used for evaluating potential climate change impacts from various greenhouse gases. The CDPHE Air Pollution Control Division estimates the standard will reduce as much as 12.53 million metric tons of carbon dioxide equivalent by 2050 — the same as the carbon dioxide emissions from burning nearly 1.41 billion gallons of gasoline.
Up to 32 landfills will be subject to stricter methane controls
The new regulation applies to up to 32 of the state’s 82 municipal solid waste landfills, including both open and closed sites, based on the amount of waste they hold and their methane emissions. Currently, 11 of the state’s largest municipal solid waste landfills are already subject to similar federal emission control measures, which have resulted in lower greenhouse gas emissions in the past five years. This success provides a strong foundation for expanding these efforts across Colorado.
Key components of Colorado Air Quality Regulation Number 31 include:
- 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, ensuring 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.
These requirements build on an October 2024 rulemaking that expanded greenhouse gas reporting for state landfills. Data obtained through that rule will help Colorado track methane reductions over time as the new Colorado Air Quality Regulation Number 31 is implemented.
Public input shaped the rulemaking
The CDPHE Air Pollution Control Division worked closely with community members, environmental groups, and industry representatives for over a year throughout the rule development and rulemaking process. The division incorporated suggestions from a technical working group that met from August 2024 through November 2024. Then, the division held community meetings starting in December 2024 to share information about the proposal and gather more input. After the start of the rulemaking hearing in August 2025, the division then met with interested parties through November 2025 to further refine the proposed rule, which the commission adopted at the December 2025 rulemaking hearing. The division will continue to engage stakeholders during the implementation of the standard to support compliance and transparency.
For more information and updates, visit the division’s landfill methane reductions web page.
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