Biogas from anaerobic digestion is already a valuable energy source, but in many cases, it is still underutilized. Simply using raw biogas in a CHP unit limits its potential, especially as demand for renewable natural gas (RNG) continues to grow.

Biogas upgrading changes that. By removing CO₂, H₂S, and moisture, the gas can be upgraded to biomethane that meets natural gas standards. This allows plant operators to inject gas into the grid, use it as vehicle fuel, or supply industrial applications—while improving overall project value and efficiency.

What is Biogas Upgrading?

Biogas upgrading is the process of refining raw biogas into high-purity biomethane by removing carbon dioxide (CO₂), hydrogen sulfide (H₂S), moisture, and other trace impurities.

Raw biogas typically contains 50–70% methane (CH₄), with the rest mainly made up of CO₂ and small amounts of unwanted gases. These impurities lower the energy value of the gas and limit how it can be used.

After upgrading, the methane concentration can reach 90–99%, making the gas comparable to natural gas and suitable for grid injection, vehicle fuel, or industrial applications.

Biogas Upgrading Process: From Raw Gas to Biomethane

Gas Pretreatment and Compression

In a typical biogas upgrading process, raw biogas is first cleaned to remove H₂S, moisture, and solid particles. This protects downstream biogas upgrading equipment and ensures stable operation. The gas is then compressed to the required pressure, which improves separation efficiency in the following stage.

Gas Separation and Biomethane Production

The core of biogas upgrading is gas separation, where CO₂ is removed to increase methane concentration. In membrane biogas upgrading, CO₂ passes through the membrane faster, while CH₄ is retained. After this step, the gas is upgraded to high-purity biomethane, completing the biogas upgrade to biomethane.

Overview of Biogas Upgrading Technologies

Water Scrubbing

Water scrubbing is a widely used method in biogas upgrading technologies, where CO₂ is absorbed into water under pressure. It is a proven solution for large-scale projects, but it requires a continuous water supply and additional treatment for the process water.

Pressure Swing Adsorption (PSA)

PSA is a dry biogas upgrading system that separates gases based on adsorption properties. CO₂ is captured on adsorbent materials, while methane passes through. The system operates in cycles, making it suitable for medium-scale biogas upgrading plants.

Chemical Absorption

Chemical absorption uses solvents such as amines to remove CO₂ from biogas. It can achieve high methane purity, but the process involves higher operating costs due to chemical consumption and system complexity, especially in large biogas upgrading equipment setups.

Membrane Biogas Upgrading

Membrane biogas upgrading separates gases based on different permeation rates. CO₂ passes through the membrane faster, while methane is retained. This method is compact, modular, and does not require chemicals or water, making it a practical choice for modern biogas upgrading systems.

Membrane Biogas Upgrading: Why It Matters

Membrane biogas upgrading is widely used for its simple process and stable performance. It separates CO₂ from methane based on different permeation rates, allowing the gas to be upgraded to biomethane without chemicals, water, or heat. Compared with other biogas upgrading technologies, membrane systems require less infrastructure and are easier to operate, making them a practical option for modern biogas upgrading plants.

At Biowatt-Biogas, the biogas upgrading system is built around a 3-stage membrane design with thousands of hollow-fiber modules. The system operates at room temperature and does not require process water or chemical additives. It can achieve methane recovery of up to 99.6%, while keeping energy consumption low and operation stable. With a modular, containerized structure, the entire biogas upgrading equipment can be installed quickly on site and scaled from 80 to 12,000 Nm³/h depending on project size.

Biogas Upgrading Equipment and System Design

Pretreatment and Gas Conditioning

A complete biogas upgrading system begins with pretreatment. Raw biogas is first desulfurized, dried, and filtered to remove H₂S, moisture, and particles. These steps are essential to protect downstream biogas upgrading equipment and ensure stable long-term operation.

Compression and Membrane Separation Unit

After pretreatment, the gas is compressed and sent to the core upgrading unit. In a membrane biogas upgrading system, CO₂ passes through the membrane faster while methane is retained, increasing gas purity. Biowatt-Biogas’s system uses a 3-stage membrane configuration with hollow-fiber modules, allowing efficient CO₂ removal and high methane recovery under stable operating conditions.

Containerized System Integration

Modern biogas upgrading equipment is typically designed as a fully integrated, containerized system. Key components—including pretreatment units, compressors, and membrane modules—are pre-assembled in a compact structure. This reduces on-site installation work and allows faster commissioning, while making it easier to scale capacity for different biogas upgrading plants.

Applications: What Can You Do With Upgraded Biomethane?

Grid Injection

One of the main uses of upgraded gas is grid injection. After biogas upgrading to biomethane, the gas meets natural gas standards and can be fed directly into existing pipeline networks.

Vehicle Fuel (Bio-CNG / Bio-LNG)

Upgraded biomethane can be used as a clean transportation fuel, reducing emissions while using existing gas infrastructure.

Industrial and On-Site Energy Use

Biomethane can also be used for industrial heating, boilers, or as a replacement for natural gas in manufacturing processes, improving overall efficiency.

Conclusion: Choosing the Right Biogas Upgrading System

Selecting the right biogas upgrading system depends on factors such as gas flow rate, required methane purity, and project application. Among available technologies, membrane-based solutions are increasingly preferred for their simple operation, modular design, and lower operating requirements. With the right biogas upgrading equipment, operators can reliably upgrade biogas to biomethane and improve overall project efficiency and return.