Landfill Methane Outreach Program
LFG Energy Projects
- What is landfill gas?
- How can landfill gas be used for energy?
- What are the economic benefits of using landfill gas as a resource?
- What are the environmental benefits of using landfill gas as an energy resource?
- What are the other benefits of using landfill gas as an energy resource?
- Who uses recovered landfill gas?
- Are landfill owners/operators required to develop and implement LFG energy projects?
- Do LFG energy projects conflict with waste diversion?
- Do LFG energy projects reduce greenhouse gas emissions?
- What are the indirect CO2 emission reduction benefits from replacing fossil fuel-derived energy with energy generated from LFG?
- How do flaring LFG and LFG energy projects compare with regard to controlling fugitive emissions?
- How do LFG energy projects at landfills reduce fugitive methane emissions?
- Do voluntary greenhouse gas markets create incentives for LFG energy projects?
- Do "Wet Cell" landfill practices increase greenhouse gas emissions?
- Are LFG energy projects compatible with bioreactor technologies?
- How do landfill cover requirements affect LFG energy projects?
- How well do LFG collection and control systems manage fugitive methane emissions?
What is landfill gas?
Landfill gas (LFG) is created when organic waste in a municipal solid waste landfill decomposes. This gas consists of about 50 percent methane (the primary component of natural gas), about 50 percent carbon dioxide (CO2), and a small amount of non-methane organic compounds (NMOCs). Instead of being allowed to escape into the air, LFG can be captured, converted, and used as an energy source. Using LFG helps to reduce odors and other hazards associated with LFG emissions, and helps prevent methane from migrating into the atmosphere and contributing to local smog and global climate change.
How can landfill gas be used for energy?
Of the approximately 2,400 active or closed municipal solid waste landfills identified in LMOP's national database, about 595 of them have one or more LFG energy projects in operation, resulting in 645 operational projects. EPA estimates that as many as 440 additional landfills could cost-effectively have their methane turned into an energy resource, producing enough electricity to power nearly 512,000 homes across the United States. The remaining landfills in LMOP's database either have a project in the construction or planning phase or previously had a project that has since ceased operating, or are not known to have LFG energy potential based on the data available.
What are the economic benefits of using landfill gas as a resource?
LFG energy projects are a win-win opportunity for all parties involved, whether they are the landfill owner/operators, the local utility, the local government, or the surrounding community. Even before LFG energy projects produce profits from the sale or use of electricity, they produce a related benefit for communities: jobs. LFG energy projects involve engineers, construction firms, equipment vendors, and utilities or end users of the power produced. Much of this cost is spent locally for drilling, piping, construction, and operational personnel, providing additional economic benefits to the community through increased employment and local sales. Once the LFG system is in place, the captured gas can be sold for use as heat or fuel or be converted and sold on the energy market as renewable "green" power. In so doing, the community can turn a financial liability into an asset.
What are the environmental benefits of using landfill gas as an energy resource?
Converting LFG to energy offsets the need for non-renewable resources such as coal and oil, and reduces emissions of air pollutants that contribute to local smog and acid rain. In addition, LFG energy projects help curtail global climate change, because they reduce emissions of methane, a greenhouse gas more potent than CO2. LFG energy projects go hand–in–hand with community commitments to cleaner air and reductions in greenhouse gases that cause global climate change. For more information on environmental benefits, please visit LMOP's Basic Information page.
What are the other benefits of using landfill gas as an energy resource?
By participating in LFG energy project development, a community is being innovative and responsible with local resources, and can even enhance its image as an environmental leader. Reducing LFG emissions by converting them to energy reduces local ozone levels and smog formation, diminishes explosion threats and unpleasant odors created by the landfill, and improves overall landfill management. This makes the area surrounding the landfill a better place to live. A community that uses its LFG is both a steward of the environment and a leader in ensuring the well–being of its citizens.
Who uses recovered landfill gas?
Almost any entity can use LFG for a variety of purposes. One option is for utilities and power providers to purchase the electricity generated from the recovered LFG. Purchasing electricity from LFG enables utilities and power providers to add a renewable energy component to their energy portfolios. In addition, any entity (including municipalities, local industrial customers, and other organizations) that has a need for a direct and constant power supply is a good candidate for LFG use. LFG can be piped directly to a nearby facility for use as either a boiler or industrial process fuel. Direct use of LFG is reliable and requires minimal processing and minor modifications to existing combustion equipment.
Are landfill owners/operators required to develop and implement landfill gas energy projects?
Current EPA regulations under the Clean Air Act require many landfill owners/operators to collect and combust LFG. To comply, landfill owners/operators can either burn the gas off by flaring it, or install an LFG energy system. Beneficial use of LFG is the only option that offers communities and landfill owners/operators the opportunity to reduce the costs associated with regulatory compliance by turning this landfill byproduct into a marketable resource.
Do LFG energy projects conflict with waste diversion?
The promotion of LFG energy is not in conflict with promotion of waste diversion and does not compete with waste reduction, recycling, and composting. LFG energy projects use methane that is generated from waste that has not been successfully diverted from landfills. The goal of LFG energy projects is to promote beneficial utilization of LFG collected from MSW landfills that have already disposed waste. It is possible to support the diversion of the organic fraction of discards from landfills so that uncontrolled methane is not generated and also support LFG energy projects that utilize methane generated from organic waste already disposed in landfills. The two positions are not in conflict. Additionally, the diversion of waste from landfills may not always result in a comparative reduction in greenhouse gas emissions.1
Do LFG energy projects reduce greenhouse gas emissions?
The decomposition of organic wastes generates methane, a greenhouse gas and a primary component of LFG. Many landfills with LFG energy projects are subject to Clean Air Act regulations (40 CFR part 60 subpart WWW) known as the New Source Performance Standards (NSPS) and are required to install and operate LFG collection and control systems.2 According to LMOP's database as of March 2015, there are about 595 landfills with LFG energy projects in place. Of these sites, approximately 60 percent are subject to the collection and control requirements of the NSPS. For the landfills with LFG energy projects in place that are not subject to the NSPS, the presence of an LFG energy project represents the voluntary collection and control of LFG. This results in the reduction of emissions beyond what is required by EPA standards.
What are the indirect CO2 emission reduction benefits from replacing fossil fuel–derived energy with energy generated from LFG?
The benefits of LFG energy in terms of greenhouse gas emission reductions are substantial. For example, a 3 megawatt LFG energy facility requires approximately 1,075 standard cubic feet per minute (scfm) of LFG to operate.3 Not only does the combustion of this quantity of methane in an LFG energy facility result in direct methane emission reductions, but also in indirect CO2 emission reductions of about 11,950 metric tons per year, depending on the type of fuel that was used to generate the displaced electricity. The indirect environmental benefits of fossil fuel displacement through LFG energy can amount to nearly 10 percent of the direct greenhouse gas emission reduction benefits from methane combustion.
The direct and indirect CO2 equivalent (CO2e) emission reductions from a direct–use project utilizing 1,000 scfm of LFG are approximately 126,000 and 12,440 metric tons per year, respectively.
How do flaring LFG and LFG energy projects compare with regard to controlling fugitive emissions?
The NSPS for MSW landfills requires that landfills above a specified size and emission level collect and control LFG emissions, measure and report emissions, and meet other operational standards. These landfills must install and operate a gas collection and control system per the design submitted to the appropriate air regulatory agency. Additionally, these landfills must conduct quarterly surface (fugitive) emission monitoring evaluations to determine if excessive amounts of fugitive organic gases are present. If a surface emission monitoring event shows elevated fugitive emissions, the landfill must adjust or modify its gas collection and control system to increase the amount of LFG recovered from the landfill and to meet the surface emission criteria required by the NSPS. These requirements are the same, regardless of whether LFG is flared or an LFG energy facility is present. Therefore, at landfills regulated by the NSPS, the presence of an LFG energy project does not have an effect on the control of fugitive methane emissions. However, landfills with LFG energy projects are more likely to employ greater efforts to maximize collection efficiencies than landfills which only flare the gas to meet NSPS emission requirements. Given the level of capital investment for an LFG energy project, it is inherently in the project developer's interest to collect and utilize as much LFG as possible to make the project financially successful. Thus, a landfill with an LFG energy facility, if subject to the NSPS rule, will likely have the same or lower amounts of fugitive emissions than a similar landfill that is simply flaring the gas.
How do LFG energy projects at landfills reduce fugitive methane emissions?
Many landfills with LFG energy projects are subject to the NSPS for air emissions from landfills. Therefore, the overriding factor in minimizing fugitive methane emissions is the presence of the NSPS which requires collection and control of LFG along with periodic monitoring of surface (fugitive) emissions.
In many cases a landfill with an LFG energy facility will have an incentive to collect greater amounts of LFG than is required by the NSPS in order to increase the amount of useful energy generation. Increases in LFG recovery typically are achieved by making wellfield adjustments and increasing the number of wells in order to achieve higher collection efficiencies. Additionally, at landfills that are not subject to the NSPS, the presence of an LFG energy project provides a revenue source that can make the voluntary collection and control of LFG financially attractive, resulting in the destruction of fugitive methane emissions that would not have been reduced otherwise.
Do voluntary greenhouse gas markets create incentives for LFG energy projects?
Due to the high costs of installing and operating gas collection and control systems, the voluntary installation of such systems is more likely to occur when financial incentives are present, such as greenhouse gas emission reduction credits or the sale of renewable energy credits generated at an LFG energy facility. In these cases, the presence of greenhouse gas markets and LFG energy projects contributes to lower fugitive methane emissions from unregulated landfills by providing the incentive for collection and control beyond what is required by regulation. In fact, for a gas collection and control system to be eligible to generate greenhouse gas credits, a project developer has to demonstrate that the project results in methane destruction beyond what is required by Federal, state, and local requirements and "business as usual."
Do "Wet Cell" landfill practices increase greenhouse gas emissions?
The use of leachate recirculation and bioreactor methods incorporate liquid management and pumping systems to maintain higher moisture content in the disposed waste mass. These technologies are similar, with the difference being that bioreactors utilize other liquids, in addition to leachate, in the recirculation and are not considered to be bioreactors until the average waste moisture content reaches 40 percent. The reason for the growth of leachate recirculation and, on a much smaller scale, bioreactors, is for landfill owners to save valuable landfill space. A secondary reason is to economically manage leachate.
The implementation of bioreactor technologies does accelerate the generation of methane by a landfill. Therefore, bioreactor landfills are required to install and operate LFG collection and control systems earlier than non-bioreactor landfills. According to the National Emission Standards for Hazardous Air Pollutants (NESHAP) for MSW landfills (40 CFR part 63 subpart AAAA), landfills that are bioreactors are required to commence operation of a gas collection and control system within 180 days after reaching bioreactor status, regardless of the amount of emissions. For non-bioreactor landfills, the required date for commencement of operation of a gas collection and control system is 30 months after NMOC emissions exceed 50 megagrams (Mg) per year, per the NSPS. Therefore, Federal requirements to control air emissions from bioreactor landfills address the acceleration of methane generation from these sources and minimize any additional fugitive methane emissions that would result from the implementation of a bioreactor technology. However, landfills that recirculate leachate but do not meet the NESHAP definition of a bioreactor landfill, may have increased emissions relative to similar landfills that do not recirculate leachate during the time period prior to installing a gas collection and control system.
Are LFG energy projects compatible with bioreactor technologies?
Several U.S. MSW landfills are considered to be bioreactors, and many of these have LFG energy projects in operation. Bioreactor landfills are required to collect and control LFG earlier than non-bioreactor landfills. After the LFG is collected from a landfill, the type of landfill (bioreactor or non-bioreactor) has little influence on the characteristics of LFG and its use in an LFG energy project.
How do landfill cover requirements affect LFG energy projects?
While landfills with only intermediate or daily soil covers can achieve high collection efficiencies and tend to have higher methane oxidation rates, final cover installation lowers fugitive emissions and helps improve collection efficiency and the methane quantity in collected gas. The benefits in terms of decreased efforts needed for a landfill to remain in compliance with the NSPS can be significant. The increases in collection efficiency will likely offset decreases in LFG generation resulting from decreased waste moisture following the installation of a final cover. For these reasons, a final cover helps a landfill with NSPS compliance without significantly impacting its ability to collect sufficient quantities of LFG to support an LFG energy project. However, if a landfill is subject to the NSPS, it is required to meet surface (fugitive) emission requirements regardless of the cover type.
How well do LFG collection and control systems manage fugitive methane emissions?
Even without early installation of LFG collection and control systems, landfills regulated under the NSPS will flare or burn in LFG energy facilities the majority of methane they generate over the long term. An IPCC report asserts that the average fraction of LFG collected over the long term may be as low as 20 percent. This percentage is for the low end of the range of estimates in the literature for landfills with "less efficient or only partial gas extraction systems."4 Additionally, the data presented in the IPCC report are based on landfills observed in operation around the world across a wide range of conditions. However, landfill and LFG collection operations in the United States are well established.
The same IPCC report also states that more than 90 percent recovery can be achieved at cells with final cover and an efficient gas extraction system. This higher estimate is based on intensive field studies of the methane mass balance at landfills.5 Other similar studies conducted recently have also measured very high collection efficiencies.6, 7 The often-cited EPA estimate that collection efficiencies range from 60 to 85 percent, with an average of 75 percent, should be considered to be conservative for landfills that are in compliance with the NSPS using comprehensive gas collection systems.
Reductions in collection efficiencies to account for uncollected LFG prior to system installation and after system decommissioning (“lifetime” collection efficiency estimates) will not be large at NSPS-regulated landfills (if calculated on a flow-weighted average) because LFG generation rates before and after system installation will be relatively low. NSPS regulations require that landfills that have a design capacity over 2.5 million metric tons use EPA's Landfill Gas Emissions Model (LandGEM) to estimate LFG generation. Once the model's estimate of NMOCs in LFG exceeds 50 Mg per year, the landfill owner will be required to install and begin operation of a gas collection and control system within 30 months in compliance with NSPS regulations. This 50 Mg threshold can be exceeded as quickly as one year after a landfill's opening date if 250,000 tons of waste per year or more are disposed and NSPS Tier 1 default values are applied to the model. NSPS regulations will then require the system to be operated for at least 15 years and until NMOC emissions are less than 50 Mg, based on measurements taken over at least a nine month time period.
As a result of these NSPS requirements, a large percentage of lifetime LFG emissions will be controlled. For example, a landfill that disposes 250,000 tons of waste per year for 20 years will collect and control approximately 62 percent of generated LFG over a 100 year period if 75 percent collection efficiency is achieved while the system is operating in compliance with NSPS.8 The 100-year overall LFG collection efficiency increases to 70 percent if the landfill is able to achieve 85 percent collection efficiency while the system is operating in compliance with the NSPS. However, even after the gas collection and control system can be decommissioned in accordance with the NSPS rule requirements, the system will likely need to be operated and maintained during some or all of the remaining post-closure care period.
1 Organic waste diversion may not always result in lower greenhouse gas emissions than landfills with efficient gas collection systems if all emissions are accounted for, including from the transportation and processing of organic waste. EPA has developed detailed procedures for evaluating the greenhouse gas impacts of alternative solid waste management options as described in Solid Waste Management and GHG Emissions – A Life–Cycle Assessment of Emissions and Sinks. Furthermore, studies by the South Coast Air Quality Management District in California have shown that open windrow composting produces significant amounts of volatile organic compounds and methane if not properly operated.
2 Some older landfills are subject to Federal and state plans that implement the Federal MSW landfill emission guidelines (40 CFR part 60 subpart Cc). The emission guidelines have the same LFG collection and control requirements as the NSPS. For simplicity, the term “NSPS” as used in this FAQ, encompasses both the NSPS and the emission guidelines.
3 Assumes the LFG energy plant is online 92 percent of the time, requires 7 percent of the electrical output to operate the plant (“parasitic load”), and displaces power produced by a fossil fuel power plant.
4 IPCC 4th Assessment Report, Chapter 10 – Waste Management (p. 600).
5 Spokas, K., J. Bogner, J. Chanton, M. Morcet, C. Aran, C. Graff, Y. Moreau-le-Golvan, N. Bureau, and I. Hebe, 2006: Methane mass balance at three landfill sites: what is the efficiency of capture by gas collection systems? Waste Management, 26, pp. 516-525.
6 Huitric, R., D. Kong, “Measuring Landfill Gas Collection Efficiency Using Surface Methane Concentrations,” Proceedings from the Solid Waste Association of North America's 29th Annual Landfill Gas Symposium. St. Petersburg, Florida. March 27-30, 2006.
7 Huitric, R., D. Kong, L. Scales, S. Maguin, and P. Sullivan, “Field Comparison of Landfill Gas Collection Efficiency Measurements,” Proceedings from the Solid Waste Association of North America's 30th Annual Landfill Gas Symposium. Monterey, California. March 2007.
8 Based on a LandGEM model run using NSPS default values for wet sites and an NMOC concentration of 1,000 ppm to estimate the system decommission date. Higher estimated lifetime collection efficiencies would result from higher assumed NMOC concentrations (due to longer system operation period requirements under the NSPS). Note that methane emissions would be further reduced due to oxidation in cover soils.