As global energy consumption continues to grow, countries are rapidly transitioning toward cleaner, greener, and locally available energy alternatives. Among these, Compressed Biogas (CBG) or biomethane has emerged as a promising fuel, especially in agrarian economies like India, where abundant biomass waste exists. Upgrading raw biogas (typically 55–65% methane and 35–45% CO₂ with traces of H₂S and moisture) to pipeline-grade methane (above 95% CH₄) is essential for it to be used as a vehicle fuel or injected into gas grids.

Over the years, several biogas upgrading technologies have been developed, including Amine Scrubbing, Water Scrubbing, Pressure Swing Adsorption (PSA/VPSA), and Membrane Separation. This blog explores how these technologies compare—and why membranes have emerged as the most popular choice in modern CBG plants.

1. Biogas Upgrading Technologies at a Glance

1.1 Amine Scrubbing

Amine scrubbing is a chemical absorption method primarily used for large-scale CO₂ removal, especially in natural gas processing. In this method, biogas is passed through an aqueous amine solution that chemically binds CO₂. The CO₂-rich amine is then regenerated by heating, releasing CO₂ for disposal or utilization.

Pros: High purity methane (>99%), effective even at low methane concentrations.

Cons: High energy requirement for regeneration, complex design, chemical degradation over time, not suitable for small or medium-scale plants.

1.2 Water Scrubbing

A physical absorption method, water scrubbing exploits the fact that CO₂ and H₂S are more soluble in water than CH₄. In this method, biogas is washed with water in a column under pressure.

Pros: No chemicals involved, relatively simple design, effective at removing both CO₂ and H₂S.

Cons: High water consumption or need for recirculation systems, less efficient methane recovery, high-pressure compressors needed.

1.3 Pressure Swing Adsorption (PSA/VPSA)

PSA uses adsorbent materials such as activated carbon or zeolites to selectively adsorb CO₂, H₂S, and moisture under pressure. The adsorbent is regenerated by reducing the pressure (and sometimes purging with gas).

Pros: Modular, dry process, no chemicals, proven technology.

Cons: Methane loss in off-gas (5–10%), cyclic operation means uneven flow, complex valve systems, higher CAPEX for large-scale operations.

2. Membrane-Based Separation – The Modern Choice

Membrane technology uses semi-permeable polymer membranes to separate CO₂ from methane based on differences in molecular size and solubility. CO₂ permeates through the membrane faster than CH₄, enriching the methane on the retentate side.

2.1 How It Works

In a typical 2- or 3-stage configuration, membranes allow staged purification of biogas:

Stage 1: CO₂-rich permeate removed.

Stage 2: Residual methane recovered.

Stage 3: Optional polishing stage to meet >96% CH₄.

2.2 Advantages of Membrane Systems

✅ Energy Efficient: Operates at moderate pressures (7–15 bar), no regeneration heat needed like amine systems.

✅ Compact & Modular: Skid-mounted systems, easily scalable, faster installation.

✅ Low Methane Loss: Advanced systems achieve <2% methane slip.

✅ Dry Process: No water or chemicals involved—zero liquid waste.

✅ Simple Operation: Fewer moving parts than PSA, lower maintenance.

✅ Environmentally Friendly: No effluent or amine degradation issues.

2.3 Membrane Material Innovation

With manufacturers like Airrane (South Korea) introducing high-performance hollow fiber membranes, selectivity and durability have significantly improved. Modern membranes can sustain thousands of hours of operation with minimal fouling and high gas throughput.

*Microscopic view of hollow fiber membranes*

Parameter	Amine Scrubbing	Water Scrubbing	PSA/VPSA	Membrane Separation
CH₄ Purity	Up to 99%	92–98%	90–96%	95–98%
Methane Loss	<1%	2–5%	5–10%	<2%
CAPEX	High	Moderate	Moderate	Low–Moderate
OPEX	High (heat, chemicals)	High (water use)	Moderate	Low
Footprint	Large	Medium	Medium	Compact
Automation Potential	Moderate	Moderate	Moderate–High	High
Suitable Scale	Large	Medium–Large	Medium–Large	Small–Large (modular)
Environmental Impact	Waste amine	Water disposal	Off-gas loss	Minimal

4. The Future of Biogas – Where Membranes Fit In

India’s SATAT (Sustainable Alternative Towards Affordable Transportation) initiative by the Ministry of Petroleum and Natural Gas aims to roll out 5,000 CBG plants by 2025, promoting decentralized clean energy and rural employment. In this landscape, membrane-based systems offer an ideal balance of cost, efficiency, and simplicity, particularly for projects that must go from concept to commissioning quickly.

The Ministry of New and Renewable Energy (MNRE) is also emphasizing green technologies that are environmentally sound and easy to maintain, making membrane technology highly aligned with national priorities.

5. Conclusion – Why Membranes Lead the Way

While traditional technologies like amine and water scrubbing still hold relevance in specific contexts, they are often constrained by high operating costs, complex maintenance, and environmental burdens. PSA systems, though dry and proven, suffer from higher methane loss and operational complexity.

Membrane technology, on the other hand, has emerged as the front-runner in the biogas upgrading race—particularly for small and medium-scale CBG projects. Its energy efficiency, low maintenance, compact design, and environmental friendliness make it the preferred choice for new-age entrepreneurs and EPC players looking to deploy reliable, fast-to-commission, and future-ready biogas upgrading plants.

As membranes continue to improve in performance and affordability, their dominance in the biogas space is only set to increase—helping nations meet renewable energy targets while creating sustainable rural economies.

Wish to advance towards more reliable biogas upgrading system – Membrane Based?

At Daltech, we offer advanced membrane solutions for biogas upgrading that are reliable, efficient, and built for long lasting period.

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