Genoa, Italy
Landfill Gas Upgrading to Grid Biomethane
Project details
Technology: Two-stage PSA and balance of plant
Commissioned: 2020
Biogas Source: Landfill
Pipeline: Snam
Specifications
Capacity: 1,500 Nm³/h / 934 SCFM
Raw Gas Composition: 43.9% CH₄, 34.5% CO₂,
14.8% N₂, 2.3% O₂, 200 ppm H₂S, 100% RH
Design Specifications RNG / Biomethane: >96% CH₄, <2.5% CO₂,
3.7% N₂, <0.6% O₂
Power Consumption of Biogas Upgrading Plant:
< 0.354 kWh/Nm³ raw biogas (wet basis)
Italy’s first landfill-gas-to-grid biomethane plant runs on IVYS two-stage PSA
At the Monte Scarpino landfill above Genoa, a two-stage IVYS kinetic PSA system upgrades lean, nitrogen-rich landfill gas to >96% CH4 biomethane, which is injected into Italy’s Snam gas transport network. Asja Ambiente Italia developed, built, and operates the plant under a concession from AMIU Genova, the city’s waste management company and landfill operator.
The Challenge: Turning Lean, Nitrogen-Rich Landfill Gas into Grid-Quality Gas
For about 15 years, Asja generated electricity from Monte Scarpino landfill gas under an AMIU Genova concession. The 11.2 MW plant was later converted to biomethane, reducing emission points from five to two, which also reduced testing, paperwork, and risk of a breach, and additionally extended gas monetization. A small generator remained to power the biomethane plant.
The landfill gas itself presented a challenge. Under nominal conditions, it contains only 43.9% CH4, along with 14.8% N2 and 2.3% O2 originating from air drawn into the collection wells. Digester biogas typically contains less than 1% N2 and O2, making a single CO2-removal stage sufficient. At Scarpino, however, N2 and O2 must also be removed to meet grid specifications.
The plant also had to handle:
- Wide swings in composition:
- Contaminants, including VOCs, H2S, siloxanes, and ammonia
- Declining flow rates:
- Very limited space
The Solution: A Two-Stage Fast-Cycle Rotary Valve PSA Upgrading Plant
IVYS (then Xebec Adsorption) supplied a complete, modular upgrading plant based on two pressure swing adsorption (PSA) stages. The first stage removes CO2, while the second rejects N2 and O2 and recovers methane that would otherwise be lost in a single-stage system.
The rotary-valve speed determines the balance between purity and recovery, enabling the plant to adjust to variations in gas quality and flow.
Performance: From 43.9% to >96% CH4
The plant takes landfill gas with less than half methane and delivers biomethane that meets Italian grid standards UNI/TR 11537:2016 and EN 16723.
Results in the field
Six months after start-up, the plant had injected more than 2 million m³ of biomethane into the Snam network by June 2021. In 2021, it produced more than 3.5 million m³—enough to supply 2,400 households and equivalent to saving about 2,870 tonnes of oil.
