The U.S. has over 2,600 municipal solid waste landfills (MSWL). These landfills receive household waste such as product packaging, lawn clippings, furniture, clothing, glass bottles, metal cans, food waste, newspapers, appliances, paint, and batteries. This comes from homes, schools, hospitals, and businesses. MSWLs emit landfill gas (LFG) biogas comprised of methane and other nonmethane organic compounds.
LFG biogas results from the decomposition of organic material in landfills. LFG biogas composition is mainly methane, carbon dioxide (CO2) and a minor amount of non-methane organic compounds.
Methane is a greenhouse gas (GHG) that is targeted for worldwide reduction to address climate change. MSWLs are the third-largest source of human generated methane emissions in the United States, accounting for approximately 17% of methane in 2019. Reducing methane emissions from MWSLs is part of the strategy to reduce GHG emissions for climate change responses.
Below is a breakdown of methane emissions to the atmosphere by source type in the U.S published by the USEPA:
Note: All emission estimates from the above graphic are from Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2019.
Landfill Gas (LFG)
By volume, LGG typically contains:
- Methane: 50 – 55%
- Carbon dioxide: 45 – 50%
- Nonmethane organic compounds (NMOCs): less than 1%
- Hydrogen sulfide (H2S): less than 1.5%
The energy content of untreated LFG is approximately 500 BTU/scf and can be combusted in a flare or enclosed combustion device.
Uses of LFG
As a substitute for natural gas, LFG that has been processed/conditioned has many uses. These include:
- Fuel gas
- Generate heat
- Generate electricity
- Vehicle fuel
The EPA’s LFG Energy Project Database indicated that, in March 2021, there were 550 LFG energy projects operating in 48 states. A breakdown of these projects
- 70 percent of the projects generated electricity
- 17 percent were direct-use projects with the LFG used in a boiler, furnace or kiln
- 13 percent were renewable natural gas (RNG) projects where the LFG was processed to be comparable to natural gas and injected into a natural gas pipeline
Renewable Natural Gas (RNG)
Renewable natural gas (RNG) is a term used for LFG biogas that has been processed and conditioned so it can be used in place of fossil natural gas. Depending on the amount of LFG treatment, RNG will have a BTU/scf range of about 500 to 1000.
LFG Processing to RNG
LFG that is collected by MSWL collection system needs to be processed to be considered renewable natural gas (RNG).
Levels of treatment of LFG include:
- Primary treatment removes moisture and particulate matter.
- After this treatment, the gas can be combusted in a flare, ECD or thermal oxidizer or used in some boilers and kilns.
- Secondary treatment removes impurities and compression.
- This treatment removes siloxanes and sulfur. The gas can then be used in boilers or for electricity generation using engines or turbines.
- Advanced treatment removes CO2, H2S, oxygen, nitrogen and VOC removal and further compression.
- This treatment produces RNG with a heating value closer to 900+ BTU/scf.
- The treatment results in offgas that contains methane, CO2 and H2S. The offgas is routed to a flare, enclosed combustion device (ECD) or thermal oxidizer for combustion.
Primary and secondary treatment produces medium Btu gas with a heating value less than fossil natural gas (approx. 450 BTU/scf). Advanced treatment produces RNG with a heating value closer to 900 BTU/scf.
RNG created from advance treatment methods will have a methane content of 90% or greater. RNG injected into a natural gas pipeline commonly has a methane content of 96 to 98%.
Impurities in LFG
Impurities in LFG that are typically needing removal include: CO2, oxygen, nitrogen, hydrogen, total sulfur, H2S, siloxanes and volatile organic compounds (VOCs).
Siloxanes are various compounds that contain alternate silicon and oxygen atoms in either a linear or cyclic arrangement usually with one or two organic groups attached to each silicon atom.
Siloxanes are found in everyday products that are disposed of in MSWLs. These products include shampoos, deodorants, moisturizers, health products and beauty products. Siloxanes can also be found in coatings, building sealants and lubricants.
Siloxanes have high vapor pressures, and low solubility in water and have an affinity for the vapor phase making them easily transported in LFG.
Engines, turbines, and compressors can be damaged by RNG that contains siloxanes.
Air Emissions from MSWLs
Air pollutants of concern from uncontrolled emissions include:
- Nonmethane organic compounds
- Hazardous air pollutants
- Vinyl chloride
- Ethyl benzene
Emission controls are used as primary and backup LFG emission control devices.
Primary LFG control devices are used for applications with no energy use project and to combust offgas from secondary treatment of LFG.
Backup control devices are used to ensure no venting of methane or NMOC air pollutants. Also, back up controls can be used to control startup, shutdown and malfunction (SSM) emissions.
Typical emission controls used for MSWLs include:
- Open-tipped flares
- Enclosed combustion device (ECD)
- Thermal oxidizers
- Vapor recovery compressors – used after LFG processed to reduce impurities.
Air Emission Regulations
Federal regulations that apply to MSWLs include:
- Subpart Cc – Emission Guidelines and Compliance Times for Municipal Solid Waste Landfills applies to MSWLs constructed, reconstructed, or modified before May 30, 1991.
- NSPS 40 CFR 60 Subpart WWW – Standards of Performance for Municipal Solid Waste Landfills That Commenced Construction, Reconstruction, or Modification on or After May 30, 1991, but Before July 18, 2014.
- NSPS 40 CFR 60 Subpart XXX – Standards of Performance for Municipal Solid Waste Landfills That Commenced Construction, Reconstruction, or Modification After July 17, 2014.
- NESHAPs 40 CFR 63 Subpart AAAA – National Emission Standards for Hazardous Air Pollutants: Municipal Solid Waste Landfills
Subpart Cc applies to existing MSWLs and these rules are administered by State environmental regulatory agencies using the State specific plan that has been accepted by the USEPA. NSPS WWW and NSPS XXX apply to new MSWLs based on each regulation’s applicable dates.
These regulations focus on controlling Nonmethane organic compounds (NMOC).
Rules in 40 CFR 63 Subpart AAAA regulate emissions of hazardous air pollutants (HAPs). HAPs emitted by municipal solid waste (MSW) landfills include vinyl chloride, benzene, ethyl benzene, and toluene. This rule has similar requirements as the NSPS WWW and NSPS XXX.
MSWLs with a design capacity greater than or equal to 2.5 million metric tons and 2.5 million cubic meters are subject to Title V/Part 70 or Part 71 federal permitting requirements. Part 70 operating permits are administered by the State air permitting agency. Part 71 permits are administered by the USEPA. Most MSWLs would obtain a State administered Title V/Part 70 permit. Title V air permits do not have specific emission controls for facilities or emission sources. Title V permit operating permits are designed to ensure that all Federal and State applicable requirements are listed for the operator and air permitting regulator.
Greenhouse Gas Reporting
Annual GHG reporting is required for MSWL that received waste on or after January 1, 1980, and generated methane in amounts greater than or equal to 25,000 metric tons CO2e per year. The MSWL reporting rules are in 40 CFR Part 98, Subpart HH – Municipal Solid Waste Landfills. Reporting requires calculations based on modeled methane generation based on measured/estimated historic annual waste disposal quantities, soil oxidation and quantity of methane recovered and destroyed.
For 2020, there were 1,123 MSWLs reporting GHG emissions for a total of 86.5 million metric tons CO2e.
The USEPA’s Landfill Methane Outreach Program (LMOP). LMOP is a voluntary program that works with industry and waste managers to reduce MSWL methane emissions. LMOP promotes recovery and use of biogas generated. LMOP partners include MSWL owners/operators, industry partners, energy partners, governmental partners. Currently LMOP has over 1000 partners.
The USEPA created the Waste Reduction Model (WARM) to assist with tracking and reporting GHG emissions reductions, energy savings, and economic effects from various waste management practices. WARM calculates effects from baseline and alternative waste management practices including source reduction, recycling, anaerobic digestion, combustion, composting and landfilling.
Summary and Conclusions
MSWLs emit landfill gas (LFG) that contains methane, organic compounds and H2S. These gases are generated by the decomposition of organic matter. Methane is a greenhouse gas that is targeted for reduction to address climate change.
Flares and enclosed combustion devices (ECD) are used to reduce methane emissions. Flares and ECDs can be used as a primary or backup control device.
Also, there are readily available treatment methods to condition/purify LFG so that it can be used as a renewable natural gas (RNG). Depending on the level of treatment, the RNG can contain 45 to 95+% methane and BTU values of 450 to 950+ BTU/scf.
Federal and State air regulations require MSWLs to use an LFG collection system and then to recover the LGF for treatment/beneficial use or to send the LFG gas to a control device.
There are no current federal regulations requiring reduction of methane emissions from MSWLs.
LFG recovery and emission control methods used to comply with existing regulations reduce methane emissions since methane is a major component of LFG.
In November 2021, President Biden posted a Fact Sheet with plans to reduce methane emissions in the U.S. The plan includes a push to enhance the USEPA’s voluntary Landfill Methane Outreach Program (LMOP). The national goal is to achieve a landfill methane capture and flare rate of at least 70%, a 12% increase from the current rate.
Cimarron – Who We Are
Cimarron’s vision is to work with our clients to create a cleaner environment by controlling their emissions.
We can assist you in your landfill gas emission control needs.
The company engineers and manufactures environmental, production and process equipment for the upstream, midstream and downstream energy industries, as well as environmental control solutions for biogas at wastewater facilities, digester tanks and landfills.
Cimarron offers our customers the know-how and environmental expertise to meet the environmental standards of today and tomorrow. Cimarron is committed to bring value to the Energy industry and their shareholders based on our financial strength, experienced personnel, and engineering capabilities.
As a company, we thrive every day to make a difference through innovation (e.g. ESG), customer focus, and operational efficiency. In addition to being present in all major regions in the US, Cimarron serves more than 45 countries around the world, ranging from offshore to desert. From key operational centers in the United States, Italy and the United Arab Emirates, Cimarron offers ongoing service and support through its own field service personnel and strategic third-party partners, creating a cleaner environment for our customers and their shareholders.
Since its founding in the mid-1970’s in Oklahoma, the company’s product offering has expanded from production equipment to include the largest line of environmental solutions that capture or incinerate fugitive vapors. With the acquisitions of HY-BON/EDI in 2019 and AEREON (including Jordan Technologies) in 2020, Cimarron has added strong brands, products, and ervices to its portfolio.