Technical guide
Components for biogas plants: a selection guide
Published 13 March 2026 · 8 min read
The biogas and biomethane sector is expanding rapidly in Italy, driven by PNRR funding and growing demand for renewable energy. But building a biogas plant requires components with very specific characteristics.
The specific challenges of biogas
Biogas composition — 50-70% methane, 30-50% CO2, plus traces of H2S, ammonia and water vapour — creates particularly aggressive operating conditions:
- H2S corrosion — Even at a few hundred ppm, H2S rapidly attacks brass, copper and many carbon steels
- High humidity — Condensed water combined with CO2 and H2S forms acids
- Low pressure — Biogas in the digester is at 20-50 mbar, requiring valves with guaranteed low-pressure sealing
- Explosion risk — Methane content makes the environment ATEX-classified
Valves: what to choose and what to avoid
Rubber-seated gate valves in ductile iron for digestate lines. Stainless or coated carbon steel ball valves with fire-safe design, antistatic feature and PTFE-filled or PEEK seats for gas lines. ATEX certification mandatory for electric actuators.
Never use brass or bronze valves on biogas lines — H2S attacks the copper content, causing rapid corrosion and seal failure.
The polyethylene alternative
PE 100 and PE 80 pipes are the preferred choice for many biogas plant sections: corrosion-proof, lightweight, flexible, with welded joints guaranteeing long-term sealing. Ideal for buried biogas transport lines.
Heat exchangers for the digester
Plate or shell-and-tube exchangers in 316L stainless maintain the digester at constant temperature (35-40°C mesophilic, 50-55°C thermophilic) using recovered CHP heat.
PNRR opportunities
PNRR funding is accelerating both new dedicated biomethane plants and conversions of existing biogas plants. Both create strong demand for certified, H2S-resistant components with ATEX compliance.