Landfill gas upgrading solutions FAQ

Landfill gas is extracted under vacuum, drawing air through the cover, side slopes, and wellfield. As a result, it contains nitrogen and oxygen—unlike gas from sealed digesters. It also contains siloxanes, VOCs, and halogenated compounds, and its composition changes over the site’s life. An upgrading plant must handle all three issues.

IVYS’s fast-cycle rotary-valve Pressure Swing Adsorption PSA technology separates gases by adsorbing CO₂, N₂, and O₂ onto customized adsorbents at pressure, letting methane pass as product, then releasing the adsorbed gas at low pressure. Learn more about how our PSA’s work here.

Yes. IVYS landfill upgrading units reject N₂ and O₂ together with CO₂ in a single-stage, two-stage, or with a dedicated nitrogen rejection unit (NRU) following the PSA. A single-stage handles feed nitrogen under about 4%; a two-stage system with a recycle step handles 4–8%; above 8%, a dedicated nitrogen rejection unit (NRU) follows the PSA train to remove the higher N₂.

As a screening guide, a single IVYS PSA stage meets typical pipeline specs when feed nitrogen is under about 4 mol% (dry). The final call depends on feed methane, oxygen, and the total-inert and heating-value limits in your interconnect agreement — SoCalGas Rule 30, for example, caps total inerts at 4% and requires at least 990 Btu/scf.

IVYS systems deliver RNG at 97%+ methane purity. A Secondary Recovery Unit (SRU) captures methane from the PSA off-gas that would otherwise be lost, raising overall recovery. Every recovered percentage point is revenue over a 20-year project.

The IVYS PSA removes oxygen by adsorption during upgrading. Where feed oxygen exceeds what the PSA can carry, catalytic deoxygenation is integrated into the upgrading train. Typical limits are 0.2% O₂ under SoCalGas Rule 30 and 0.1% or lower on some U.S. systems.

IVYS designs the complete upgrading solution, including chilling and regenerative drying to achieve a stable dew point; activated carbon or iron-based media to remove H₂S, sized to measured loading and pipeline specifications; and specialty adsorbent beds to remove siloxanes and halogenated compounds. This protects the PSA adsorbents and downstream compression. Pipeline operators set limits for landfill-specific constituents in RNG injection into pipelines.

Fast-cycle rotary valve PSA systems handle CO₂, N₂, and O₂ in one modular step, tolerate swings in landfill gas (LFG) composition, and scale by adding units—making it the best fit for small and mid-sized sites. Membranes remove CO₂ effectively but let most nitrogen pass, so they require a separate N₂ step. Cryogenics can handle high nitrogen levels but involve higher capex and are better suited to larger, steady flows.

Since 2006, the first IVYS (then Xebec or Questair) landfill gas upgrading PSA, an M-3100, was selected for the Rumpke Sanitary Landfill in Ohio. It upgraded 6.0 MMSCFD of feed gas to more than 96% methane for Duke Energy’s pipeline and was never shut in due to off-spec gas.

IVYS PSA systems are built to serve for 20+ years, in line with the 20–30-year gas-generation lifespan of a typical landfill. Unlike conventional PSA systems, which use large valve banks prone to failure, IVYS systems use rotary valves, significantly reducing unplanned maintenance. Under specified operating conditions, adsorbents typically last 10 years or more.

Yes, when the upgrading plant is sized to the site rather than scaled down from a large design. IVYS PSA systems for upgrading LFG are modular, and capacity grows by adding units. These are ideal for sites with gas flows of 250-1500 scfm.

A single Biostream container is rated about 280 scfm and turns down to 40% of capacity (20% optional), so it holds spec at low and declining flows. For comparison, cryogenic build-own-operate offerings typically start at 250–500 scfm.

Three reasons. First, one PSA step removes CO₂, N₂ and O₂, so a well-managed site under 4% N₂ needs no separate nitrogen rejection unit — the lowest capex, parasitic load and footprint. Second, skid or container modules arrive pre-assembled and pre-tested. Third, trains can be added or moved as the wellfield grows or declines. Our units are designed with a single control, making them extremely easy to operate and requiring no specialized training or operator.

IVYS plants are configured for the wellfield’s projected trajectory, not just its day-one gas. Turndown accommodates declining flow; additional PSA stages or a Nitrogen Rejection Unit (NRU) can be added if nitrogen levels rise; and modules can be relocated to another site at end of life. A plant designed only for year-one gas may underperform by year five, so IVYS designed the solution with that in mind.

Reduce air intrusion first. NRUs are the most expensive equipment in an LFG-to-RNG upgrading plant, both in capital cost and parasitic power. Cover repairs, wellhead rebalancing, tighter vacuum control, and short-circuiting fixes can move a site from the over-8% nitrogen band to a less expensive PSA-only configuration, removing the need for an NRU. Before specifying equipment, IVYS reviews wellhead N₂/O₂ data with your GCCS operator to identify effective solutions across the site’s entire gas flow and reduce total project capex.

Yes. IVYS supplies owner-operated equipment, allowing the landfill or its developer to retain the RNG and environmental-attribute revenue (RINs, LCFS credits) instead of sharing it under a long-term BOO contract. A right-sized PSA lowers capex, making ownership practical for smaller sites.

The PSA ships as a skid or standard container. Rotary-valve, fast-cycle design needs far less adsorbent than conventional PSA, so the upgrading step occupies a fraction of the space for a typical small-site train, including pretreatment and compression.

The full system, from landfill-gas collection through pipeline injection, includes moisture and H₂S removal; siloxane and VOC polishing; deoxygenation where needed; fast-cycle, rotary-valve PSA upgrading; optional two-stage PSA, SRU, or NRU; and product injection with metering, odorization, pressure regulation, and gas-quality monitoring.

Specifications are set by each utility. SoCalGas Rule 30, a common benchmark, caps total inerts (CO₂ + N₂ + O₂) at 4%, limits oxygen to 0.2%, and requires a minimum heating value of 990 Btu/scf. California also limits 17 landfill-specific trace constituents. IVYS process engineers configure the upgrading plant to meet your interconnect agreement.

Current and projected flow, along with measured levels of CH₄, CO₂, N₂, O₂, H₂S, siloxanes, and VOCs. The Environmental Protection Agency’s (EPA) New Source Performance Standard (NSPS) and similar agencies in Canada already require monthly wellhead monitoring for N₂ or O₂, so most sites have this key data. IVYS’s team of engineers uses these data to select a configuration and can help assess whether wellfield fixes can reduce capex.

RNG is sold to utilities and corporate buyers through long-term offtake agreements, alongside existing tipping fees. Landfill RNG also generates environmental attributes, including most cellulosic (D3) RINs under the U.S. Renewable Fuel Standard and credits through low-carbon fuel programs such as California’s LCFS and Canada’s Clean Fuel Regulations.