Membrane Biogas Upgrading System
Membrane-based biogas upgrading to >99.5% biomethane for CBG, RNG, and grid injection
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Compact, dry-process upgrading to >99.5% biomethane
CRA's Membrane Biogas Upgrading System separates CO₂ from raw biogas to produce high-purity biomethane (RNG) at over 99.5% methane, using a multi-stage membrane process with no water or solvents. Because membrane life and methane recovery depend on clean, stable inlet gas, we engineer the upstream gas train — H₂S scrubbing (chemical and biological), dehumidification, and compression — in-house and integrate it with the membrane skid as one package. The result is a compact, modular, low-OPEX system delivered containerized or skid-mounted for grid injection, Compressed Biogas (CBG / Bio-CNG), Bio-LNG, and industrial use.
Methane Recovery
>99.5% CH₄
CO₂ in Product
<0.5%
Biomethane Purity
>95%
Process
Dry membrane
What is a Membrane Biogas Upgrading System?
A membrane biogas upgrading system separates CO₂ from methane using hollow-fiber membrane modules, producing high-purity biomethane suitable for grid injection, compressed biogas (CBG/Bio-CNG), Bio-LNG, or industrial fuel — without water, solvents, or chemicals.
How it works
Compressed, dried, and desulfurized biogas enters the membrane module under pressure, where CO₂ and methane separate based on how fast each permeates through the hollow-fiber walls.
Biogas is compressed, dried, and desulfurized before it enters the membrane module, since membrane performance depends on clean, stable inlet gas.
CO₂ permeates through the hollow-fiber walls faster than methane and exits as a permeate stream, while methane-rich gas exits as the retentate.
Multi-stage configurations recirculate methane from intermediate permeate streams, pushing recovery above 95%.
Key Benefits
Achieves >99,5% methane with <0.5% CO₂, enabling direct grid injection or vehicle fuel use
Dry membrane process minimizes energy, water, and chemical consumption
Upgrading, H₂S scrubbing, and compression engineered under CRA’s roof
Containerized or skid-mounted for easy deployment and scalability
Supports RNG, Bio-CNG, and Bio-LNG pathways for decarbonization goals.
The CRA Edge
Decades of gas processing experience with reliable project delivery
End-to-end design, R&D, and manufacturing under one roof for speed and quality
ISO 9001, ASME Standards, API certification, and CE marking
Customized designs meet your exact process needs and strictest regulations
Applications
Built to help you specify.
Sizing tools, decision guides, and technical references. Use them before, during, and after your evaluation.
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Frequently Asked Questions
How does membrane-based biogas upgrading work?
Selective membranes separate CO₂ from CH₄ achieving >99.5% purity. CRA designs, manufactures, and supplies the full upgrading skid and the upstream gas train feeding it. Process: Multi-stage membrane separation | CO₂ permeates through | CH₄ retained as product | Dry process (no water/chemicals) Advantages: Compact footprint | Low OPEX | Modular/scalable | Minimal utilities
What are the key differences between biogas upgrading technologies?
Membrane: >99.5% CH₄ | Dry process | Compact | Low opex | Designed and manufactured by CRA PSA: >98% CH₄ | Dry process | Higher capex | Good for large scale Water scrubbing: >97% CH₄ | Wet process | Water consumption | Wastewater treatment needed Chemical scrubbing: >99% CH₄ | Chemicals required | Higher opex
When is a Biogas Upgrading System necessary and what purity can it achieve?
Necessary for grid injection (RNG) or vehicle fuel (Bio-CNG) requiring >98% CH₄ purity. Applications: Pipeline injection | CNG vehicles | High-value energy sales | Carbon credits CRA-manufactured membrane upgrading: >99.5% CH₄ | <0.5% CO₂ | <4 ppm H₂S | Compact modular design
What is the typical treatment train for biogas-to-Bio-CNG or RNG production?
Step 1: H₂S Removal - Chemical or biological scrubber to <10 ppm Step 2: Polishing - Activated carbon to <0.1 ppm H₂S, remove siloxanes Step 3: Dehumidification - Remove moisture to -20°C dewpoint Step 4: Upgrading - Multi-stage membrane to >99.5% CH₄, or PSA to >98% CH₄ Step 5: Compression - To pipeline pressure (100-1000 psig) or CNG (3600 psig) CRA manufactures and supplies complete integrated systems from digester to dispensing.
What determines reliability in a membrane-based biogas upgrading system?
Membrane life and output purity depend on the condition of the gas entering the module, not the membrane alone. CRA is Air Products' recognized Integration Partner for membrane biogas upgrading and engineers the full upstream train, H₂S scrubbing, dehumidification, and compression, in-house around the membrane skid rather than supplying it as a standalone unit. Systems are designed to deliver greater than 99.5% methane concentration, with CO₂ held below 0.5% and H₂S below 4 ppm, and methane recovery above 95% through multi-stage membrane configurations.