As landfill waste decomposes, it produces landfill gas (LFG)—a collection of air pollutants, including air toxics, volatile organic compounds, carbon dioxide, and methane. LFG is typically composed of 50% methane, 50% CO₂, and less than 1% NMOC (non-methane organic compounds) by volume. The NMOC portion of LFG can contain various organic HAPs (hazardous air pollutants) and VOCs (volatile organic compounds).

When EPA issued Emission Guidelines and NSPS in 1996, the agency selected NMOC as a surrogate for MSW LFG emissions because NMOC contains the air pollutants that at that time were of most concern due to their adverse effects on health and welfare.

Currently, methane’s effect on climate change are also of concern. In 2014, methane emissions from MSW landfills represented 18.2% of total US methane emissions and 1.9% of total US GHG emissions (in carbon dioxide equivalent (CO₂e)). In 2014, MSW landfills continued to be the third largest source of human-related methane emissions in the US, releasing an estimated 133.1 million metric tons of CO₂e.

The revised NSPS retain the current design capacity threshold of 2.5 million Mg and 2.5 million m³, but reduce the NMOC emission threshold for the installation and removal of a GCCS from 50 Mg/yr to 34 Mg/yr for landfills that commence construction, reconstruction, or modification after 17 July 2014.

An MSW landfill that exceeds the design capacity threshold must install and start up a gas collection and control system (GCCS) within 30 months after LFG emissions reach or exceed an NMOC level of 34 Mg/yr NMOC. The owner or operator of a landfill may control the gas by routing it to a non-enclosed flare, an enclosed combustion device, or a treatment system that processes the collected gas for subsequent sale or beneficial use.

Under the new rules, modified and existing landfills will also begin capturing and controlling landfill gas emissions at levels that are one-third lower than current requirements, updating 20-year-old standards for existing landfills.

Combined, the final rules are expected to reduce methane emissions by an estimated 334,000 tons a year beginning in 2025—equivalent to reducing 8.2 million metric tons of carbon dioxide. EPA estimates the climate benefits of the combined rules at $512 million in 2025 or more than $8 for every dollar spent to comply.

In the final NSPS, the EPA has addressed two issues related to LFG treatment. First, the EPA is clarifying that the use of treated LFG is not limited to use as a fuel for a stationary combustion device but may be used for other beneficial uses such as vehicle fuel, production of high-British thermal unit (Btu) gas for pipeline injection, or use as a raw material in a chemical manufacturing process. Second, the EPA is finalizing the definition of treated landfill gas that applies to LFG processed in a treatment system meeting the requirements in 40 CFR part 60, subpart XXX and defining treatment system as a system that filters, de-waters, and compresses LFG for sale or beneficial use. The definition of treatment system allows the level of treatment to be tailored to the type and design of the specific combustion equipment or the other beneficial uses such as vehicle fuel, production of high-Btu gas for pipeline injection, or use as a raw material in a chemical manufacturing process in which the LFG is used.

—“Standards of Performance for Municipal Solid Waste Landfills”

The final rules took into account public comments and additional data and analysis received since the agency issued the proposals in July 2014 and August 2015. The actions update the 1996 guidelines for existing landfills and strengthen the previously proposed rule for new landfills issued in 2014.

In addition, EPA’s Landfill Methane Outreach Program provides landfill owners and operators a suite of tools and technical resources to facilitate development of landfill gas energy projects. Over the last 20 years, LMOP-assisted projects have reduced and avoided more than 345 million metric tons of carbon dioxide equivalent.