These projects extract landfill gas under a high vacuum, typically ranging from -40” w.c. to -80” w.c. to the gas collection system. The gas is collected from multiple above-ground or below-ground wells through horizontal trenches. New landfills implement a gas collection and flare system that includes dehydration equipment, centrifugal blowers, and enclosed flares. The configuration of landfill gas tie-ins varies, typically involving either a Ring Header design, Herringbone design, or a combination of both, achieving around 75% gas recovery.
The technologies used for converting landfill gas to renewable natural gas (RNG) are tailored to the specific composition of the raw gas and its key components, such as Nitrogen (N2), Siloxanes (SiO), Oxygen (O2), Volatile Organic Compounds (VOCs), and Hydrogen Sulfide (H2S). Common processing systems include solid media vessels for H2S removal, compression systems, activated carbon vessels, or temperature swing adsorption (TSA) systems for VOC and Siloxane removal. For removal of carbon dioxide and nitrogen, various systems are employed such as vacuum pressure swing adsorption (VPSA) vessels or VPSA with membrane separation system, water wash systems, amine scrubbing, and organic solvent scrubbing. Additionally, a thermal oxidizer and/or an enclosed flare is typically required to manage tail gas exhaust and any product gas that fails to meet sales gas specifications.
