Landfill gas collection plays a vital role in capturing methane. This greenhouse gas has a global warming potential that makes it at least 28 times more potent than carbon dioxide. The United States now has 532 operational landfill gas projects, which shows how this renewable energy source continues to gain traction.
Landfill methane makes up 45-60% of landfill gas and gives us a great chance to tackle both environmental and energy challenges. The right gas recovery systems can turn this waste product into renewable natural gas (RNG). The methane content reaches 96-98% when we inject it into natural gas pipelines. These projects do more than protect the environment – they boost economic returns and help meet regulatory requirements. The US currently has over 200 RNG production facilities. Most of these facilities use the gas to power compressed natural gas garbage trucks. This technology still has much untapped potential. This piece explores the engineering behind landfill gas treatment and the steps needed to turn this abundant resource into pipeline-quality renewable natural gas.
Landfill Gas Collection and Recovery Systems
Careful engineering plays a vital role in designing landfill gas collection systems that capture maximum gas and reduce environmental effects. These systems are the foundations for turning waste-generated methane into valuable renewable energy resources.
Landfill gas collection system design and layout
Engineers typically use vertical wells, horizontal trenches, or both throughout the landfill. The waste mass contains vertical gas extraction wells spaced 150 to 300 feet apart based on the landfill’s characteristics. These wells use perforated pipes that collect gas and connect through lateral piping to a central header system.
A well-laid-out system has these essential components:
- Extraction wells with perforated casings
- Network of lateral and header pipes for gas transport
- Blowers creating vacuum to pull gas through the system
- Condensate collection points to remove water
- Flares for combusting excess gas
The system works better when gas recovery planning starts during the original landfill design phase, which cuts operational costs. The core team places the blower/flare station away from nearby residents to alleviate odor complaints and safety concerns.
Methane concentration in landfill gas (45–60%)
Landfill gas makes an excellent candidate for energy recovery because it contains 45-60% methane and 40-60% carbon dioxide by volume. Nitrogen (2-5%), oxygen (0.1-1%), and trace amounts of hydrogen sulfide and non-methane organic compounds make up the rest.
These factors shape methane production and concentration:
- Waste composition (higher organic content produces more gas)
- Moisture content (optimal range 50-60% boosts bacterial decomposition)
- Temperature (anaerobic bacteria thrive at 30-41°C or 85-105°F)
- Waste age (peak production occurs 5-7 years after burial)
Gas flow rate estimation and monitoring
Gas flow rate estimation serves as the life-blood of successful landfill gas recovery projects. System design and economic feasibility of energy recovery initiatives depend on flow rate. A million tons of municipal solid waste produces about 300 cubic feet per minute (cfm) of landfill gas over 20-30 years.
Modern monitoring systems track these parameters to optimize collection:
- Methane content (target 48-52% for balanced system)
- Vacuum pressure (typically 30-60 inches water column)
- Balance gas ratio (2-10% nitrogen indicates proper balance)
- Flow rates at individual wells and system-wide
Collection efficiency changes with landfill cover type—ranging from about 60% for daily soil cover to 95% for final cover systems with active collection. Up-to-the-minute data analysis from automated wellhead tuning systems can boost these rates by adjusting extraction parameters.
Engineering Methods to Upgrade Landfill Gas to RNG
The conversion of landfill gas to renewable natural gas (RNG) needs special purification technologies. These technologies remove contaminants and boost methane concentration. Different methods target specific impurities to meet pipeline quality standards.
Water scrubbing for CO2 removal
Water scrubbing stands out as a popular technology that removes carbon dioxide from landfill gas. The process uses water’s natural ability to dissolve CO2 about 26 times more readily than methane at 25°C. The system works when pressurized landfill gas (4-6.5 bar) flows up through a column while water moves down. This counter-current contact removes CO2 selectively. The method removes over 98% of CO2 with methane losses between 1-2%.
Solvent scrubbing using amine or Selexol
Chemical absorption with amines works near normal pressure and uses less electricity than other methods. The systems commonly use monoethanolamine (MEA), diethanolamine (DEA), and methyldiethanolamine (MDEA). These amine solvents deliver impressive results with methane losses as low as 0.04%.
Physical solvents like Selexol (polyethylene glycol) work best at higher pressures, usually above 34 bar. Selexol removes several impurities at once, including CO2, H2S, and heavier hydrocarbons.
Pressure swing adsorption (PSA) for nitrogen separation
PSA technology removes nitrogen, a tough contaminant that often sneaks in through air infiltration. The process uses special materials like zeolites or carbon molecular sieves in four steps: adsorption, depressurization, regeneration, and repressurization. Modern PSA systems reach methane purity above 99% and recover more than 99% of the gas.
Membrane separation for VOC and CO2 removal
Membrane systems separate gasses through specially designed polymer materials. Quality membranes can separate CO2 from CH4 at a ratio of about 3:1. These systems deliver the best results at pressures between 10-16 bar and recover more than 98% of methane.
Cryogenic distillation for methane purification
Cryogenic distillation offers an advanced way to separate nitrogen and oxygen from landfill gas. The process works by cooling the gas to very low temperatures, which separates components based on their different boiling points. Methane turns to liquid before nitrogen and oxygen, which leads to better recovery rates.
Catalytic oxidation for oxygen removal
Catalytic oxidation helps solve the challenge of removing oxygen. Pipeline gas regulations limit oxygen content to as low as 0.5%. The process uses catalysts – either precious metals like platinum or cheaper options – to combine oxygen with some methane. This creates CO2 and water. The reaction happens between 400-600°C, though newer catalysts can work at lower temperatures.
Pipeline Injection and Quality Compliance
Landfill gas must meet strict quality standards after successful upgrading to qualify for pipeline injection. Raw biogas has varying composition, but renewable natural gas needs exact specifications for safe and efficient distribution through pipeline networks.
Pipeline methane content requirements (96–98%)
Upgraded RNG needs methane concentrations between 96% and 98% to qualify for pipeline injection. This high purity makes it compatible with existing natural gas infrastructure and end-user equipment. Pipeline operators strictly limit contaminants such as carbon dioxide (typically <2%), oxygen (<0.4%), and total inerts (<4%). These limits protect the pipeline’s integrity and keep combustion properties consistent across the gas network.
Compression to 500–1400 psi for injection
RNG must be compressed to match pipeline pressure requirements, typically between 500 and 1400 psi before injection. Compression equipment makes up a large part of injection infrastructure and operating costs. The system’s compression energy and maintenance takes up 50-67% of total operating expenses. Companies can reduce these costs by 5-15% when they select injection points with lower pressure requirements.
Chain-of-custody metering and verification
A chain-of-custody metering system measures transferred gas volumes after injection. RNG mixes with conventional natural gas in pipelines, so strong tracking mechanisms play a vital role. The point-of-receipt equipment tracks quality parameters and blocks non-compliant gas from the system. Third-party verification organizations maintain system integrity through equipment inspections and administrative audits.
Partnering with Green Gas Inc. for RNG Projects
RNG projects from landfill gas need specific expertise across many technical fields. Green Gas Inc. gives detailed solutions to transform concepts into profitable operations.
Turnkey RNG project development services
Green Gas Inc. handles complete project development through their development Process. The company works on both M&A and Greenfield assets from concept to launch. Their approach uses Front-End Loading (FEL) methodology to direct projects from study phase through execution. The team starts with thorough feasibility checks to verify project viability. They create detailed development roadmaps based on each site’s landfill gas characteristics.
Custom technology selection and integration
Each landfill gas project comes with its own set of challenges that need customized solutions. Green Gas Inc. builds systems that match specific raw gas compositions. The team looks at key elements like Nitrogen, Siloxanes, Oxygen, VOCs, and Hydrogen Sulfide. Their integration services feature specialized processing systems. These include H2S removal, compression, activated carbon vessels, and advanced systems to remove carbon dioxide and nitrogen.
Regulatory compliance and permitting support
RNG projects must deal with complex regulatory frameworks. Green Gas Inc. helps guide permit applications, environmental compliance needs, and incentive programs. The team makes sure projects meet safety standards during development and operation. This approach reduces delays from regulatory issues.
Ongoing operations and maintenance services
Project success depends on proper operation and maintenance. Green Gas Inc.’s services include monitoring, optimization, and regular performance checks. Their expertise helps maximize landfill gas collection and methane capture. This process cuts greenhouse gas emissions and creates valuable renewable energy.
Conclusion
Landfill gas conversion offers a great chance to produce renewable energy and tackle major environmental issues at the same time. Our piece explores how methane—with its warming potential 28 times greater than carbon dioxide—can transform into valuable renewable natural gas. Waste management operations across America find these landfill gas projects appealing because of their dual benefits.
The process starts with well-designed collection systems that use vertical wells and horizontal trenches to capture gas. Several upgrading technologies work together after collection to purify the gas. Water scrubbing takes out CO2, and PSA technology handles nitrogen contamination. On top of that, membrane separation removes VOCs, cryogenic distillation delivers advanced purification, and catalytic oxidation gets rid of oxygen. These steps help achieve pipeline-quality gas.
Meeting pipeline injection standards poses technical challenges. The final RNG product needs 96-98% methane and must compress to 500-1400 psi before entering distribution networks. Expert knowledge plays a vital role in successful implementation.
Green Gas Inc. serves as a trusted partner with complete solutions for landfill gas projects. They provide custom technology selection, help with regulatory compliance, and maintain services regularly. Their expertise helps projects run at peak efficiency while creating valuable renewable energy.
Landfill gas shows promise as more facilities see its value. Converting this resource into pipeline-quality renewable natural gas cuts greenhouse gas emissions and creates economic benefits for waste facilities nationwide. Without doubt, advancing technology will bring better efficiency and wider use of these engineering solutions across the United States.
FAQs
Q1. What is the typical methane concentration in landfill gas?
Landfill gas typically contains 45-60% methane by volume, making it a valuable resource for energy recovery. The remaining composition primarily consists of carbon dioxide, with small amounts of nitrogen and trace gasses.
Q2. How is landfill gas collected?
Landfill gas is collected through engineered systems that use vertical wells, horizontal trenches, or a combination of both. These systems include perforated pipes, lateral and header piping networks, blowers to create vacuum, and condensate collection points.
Q3. What are the main methods for upgrading landfill gas to renewable natural gas?
The main upgrading methods include water scrubbing for CO2 removal, pressure swing adsorption for nitrogen separation, membrane separation for VOC and CO2 removal, cryogenic distillation for methane purification, and catalytic oxidation for oxygen removal.
Q4. What are the requirements for injecting renewable natural gas into pipelines?
For pipeline injection, renewable natural gas must have a methane content between 96-98%. It also needs to be compressed to 500-1400 psi and meet strict quality standards for contaminants like carbon dioxide, oxygen, and total inerts.
Q5. How can partnering with specialized companies benefit landfill gas projects?
Partnering with specialized companies can provide comprehensive solutions, including turnkey project development, custom technology selection and integration, regulatory compliance support, and ongoing operations and maintenance services. This expertise helps maximize efficiency and ensure project success.
References
- ttps://www.epa.gov/sites/default/files/2020-03/documents/pdh_chapter7.pdf
- https://www.kindermorgan.com/ETV/KM-RNG/Resources/Insights/Upgrading-Landfill-Gas-to-Renewable-Natural-Gas
- https://downloads.regulations.gov/EPA-HQ-OAR-2024-0453-0008/content.pdf
- https://www.sciencedirect.com/science/article/pii/S1364032120308728
- https://www.researchgate.net/publication/349605944_Nitrogen_rejection_from_landfill_gas_using_Pressure_Swing_Adsorption
- https://americanbiogascouncil.org/wp-content/uploads/2021/02/ABC-RNG-Pipeline-Purity-Recommendation-FINAL.pdf
