Biogas, produced via anaerobic digestion of organic waste or landfill treatment, typically contains methane (CH₄) and carbon dioxide (CO₂). Smaller amounts of hydrogen sulfide (H₂S), residual oxygen (O₂), water vapor, and other trace compounds are also present. This variable composition makes assumptions about energy content or safety unreliable. Without precise measurement, you cannot accurately evaluate heating value, combustion behavior, or contaminant risk.

A dependable analyzer, such as an NDIR gas analyzer, is critical for monitoring key gases under real-world conditions. It supports safe, efficient, and compliant operation of biogas or digester-gas systems.

Which Gases Can an NDIR Gas Analyzer Detect in Biogas, and Which Gases Still Need Other Sensors?

An NDIR gas analyzer works best for gases that absorb infrared (IR) light at specific wavelengths. In the context of biogas or digester gas, it reliably detects the major gases produced by anaerobic digestion — especially methane (CH₄) and carbon dioxide (CO₂).

• Methane (CH₄) — the main combustible component of raw biogas. NDIR sensors configured for CH₄ can measure concentrations across the full typical biogas range (from near 0 % up to nearly 100 % by volume). This makes them ideal for estimating energy content or combustion potential of biogas.
• Carbon dioxide (CO₂) — the dominant non-combustible gas in most biogas mixtures. NDIR sensors tuned to CO₂’s specific absorption band (commonly around 4.26 µm) can reliably quantify CO₂ even at high concentrations.
• Other IR-active hydrocarbons or volatile organics (when configured) — in some analyzer designs, NDIR technology can target additional IR-absorbing gases or volatile organics, depending on the optical filters and calibration.

However, NDIR has intrinsic limitations. It cannot reliably detect certain gases or contaminants that do not absorb infrared light in a suitable way. For example: oxygen (O₂) does not absorb IR light effectively; thus, NDIR sensors cannot measure oxygen concentration. Meanwhile, hydrogen sulfide (H₂S), hydrogen (H₂), sulfur dioxide (SO₂), and many trace or toxic impurities often require other sensor technologies — such as electrochemical cells, UV-DOAS, or specialized detectors — because their IR absorption bands are weak or they interfere with IR measurements.

A comprehensive gas analyzer combines NDIR for bulk gases with complementary sensors (electrochemical, UV-DOAS, etc.) for O₂, H₂S, and trace gases. This ensures accurate measurement of energy content, safety hazards, and biogas quality, supporting both combustion and biomethane production.

Why Does Accurate Gas Detection by an NDIR Gas Analyzer Matter for Biogas and Digester Operations?

Accurate gas detection matters because biogas quality, safety, and plant performance all hinge on knowing exactly what gases you have. A reliable NDIR gas analyzer — ideally augmented with additional sensors — gives operators the clarity they need to make informed operational decisions. Below are critical use cases where precise detection plays a central role.

Assessing Biogas Quality & Calorific Value

Biogas derives its energy from methane (CH₄). When you measure CH₄ and CO₂ precisely, you can estimate how much usable energy the gas carries. A higher CH₄-to-CO₂ ratio signals stronger fuel quality. If measurement is poor or inaccurate, you may overestimate energy yield and end up with underperforming combustion systems — or underestimate yield and underutilize fuel potential. Either way, process efficiency and economics suffer. Reliable gas composition data also helps you decide whether the gas is suitable for combustion, upgrading, or injection into a fuel grid. Without that data, you risk misjudging gas quality and reducing plant return on investment.

Ensuring Safety and Protecting Equipment
Biogas can contain harmful or corrosive components, such as hydrogen sulfide (H₂S), residual oxygen (O₂), moisture, or other impurities. If you feed such untreated gas into engines, compressors, or pipelines, you face risks of corrosion, engine damage, or even toxic or explosive hazards under certain conditions. Accurate detection signals when gas fails to meet safety thresholds — enabling you to trigger cleaning, desulfurization, or to reject the batch altogether. Therefore, comprehensive gas detection safeguards personnel, extends equipment life, and helps avoid unplanned downtime or costly maintenance.

Process Control and Optimization
Biogas composition is not static. It shifts with feedstock type, digestion conditions, microbial activity — even temperature or mixing rate changes. By periodically or continuously analyzing gas output, operators can catch early signs of process imbalance — for instance rising H₂S, unexpected O₂ ingress, or declining methane yield. With that insight, they can adjust digester conditions (substrate mix, retention time, pH, temperature) to restore optimal performance — improving yield, stability, and throughput. This proactive approach helps a biogas plant evolve from a “set-and-forget” system into a responsive, fine-tuned operation.

Compliance, Documentation, and Reporting
Many biogas facilities must meet environmental, safety, or fuel-quality standards — especially if they supply biomethane for grid injection, vehicle fuel, or cogeneration. Accurate, timestamped gas composition records (CH₄, CO₂, H₂S, trace gases) are often required for audits and regulatory compliance. A well-configured analyzer with data logging, export functions, and reliable calibration history helps you maintain traceability and transparency. When inspectors arrive or certification audits occur, you’ll already have robust evidence of gas quality and compliance.

Biomethane Upgrading & Grid Injection / Fuel Quality Assurance
When raw biogas is upgraded into biomethane — for pipeline injection or as vehicle fuel — standards become stringent. High methane content, minimal CO₂, and very low contaminant levels (H₂S, moisture, O₂, trace gases) are mandatory. Accurate detection forms the foundation for any gas-cleaning, scrubbing, or upgrading process. Without precise gas composition data, you risk producing sub-standard biomethane, damaging downstream equipment, or failing to meet regulatory injection requirements. Thus, NDIR (for bulk gases) plus complementary sensors (for impurities) proves indispensable for quality control, acceptance testing, and safe distribution or use of biomethane.

Final Thoughts on Use-Case Impact
Overall, accurate gas detection is far more than a convenience in biogas operations — it’s essential. It affects energy yield, safety, equipment longevity, process stability, and regulatory compliance. Whether you run a small digester or a full-scale biogas-to-biomethane plant, investing in comprehensive gas analysis pays off. It transforms raw gas streams into actionable insights: you can optimize digestion, protect assets, ensure compliance, and maximize the value of your biogas.

Conclusion

Accurate and comprehensive gas measurement is not optional in modern biogas operations. When you combine an NDIR gas analyzer (for CH₄, CO₂ and other IR-active gases) with complementary sensors (for H₂S, O₂, moisture, trace contaminants), you obtain reliable data that underpins energy quality, safety, process control, and compliance.

To summarize, a properly configured and maintained NDIR-based analyzer serves as the central toolset for any serious biogas or digester-gas operation. It converts raw gas streams into actionable data — data that protects safety, optimizes performance, ensures regulatory compliance, and unlocks the full value of your biogas output. If you want to know more details, contact with us please!

Frequently Asked Questions (FAQ)

Q1: What is an NDIR gas analyzer, and why is it widely used in biogas applications?
A: An NDIR (NonDispersive Infrared) gas analyzer detects gases by measuring how much infrared (IR) light a gas absorbs at specific wavelengths. It is widely used in biogas plants because it reliably measures the main components of biogas — especially methane (CH₄) and carbon dioxide (CO₂). 

Q2: Which gases in biogas can be reliably detected with NDIR sensors?
A: NDIR sensors can reliably detect:

• Methane (CH₄): covering the full typical biogas range (near 0 % to ~100 % volume). 
• Carbon dioxide (CO₂): even at high concentrations typical in digester gas. 
• Some other IR-active hydrocarbons or volatile organics, if the analyzer is specifically configured for them.

Q3: Why can’t NDIR alone detect all relevant gases in biogas?
A: Because NDIR relies on infrared absorption, it only works for gases that absorb IR light at distinct wavelengths. Some important gases and contaminants — such as oxygen (O₂), hydrogen sulfide (H₂S), hydrogen (H₂), and certain trace or toxic gases — either do not absorb IR strongly or require different detection mechanisms.

Q4: Which additional sensors are commonly used along with NDIR in biogas analyzers, and what do they detect?
A: Typical analyzers combine electrochemical sensors (ECD) or UV/DOAS detectors with NDIR. These additional sensors handle nonIR-active or weakly IR-active gases:

• O₂ (oxygen) — to check residual oxygen levels. 
• H₂S (hydrogen sulfide) — a common corrosive and toxic contaminant in raw biogas. 
• Sometimes trace gases or other impurities that IR detection cannot handle reliably. 

This multimodal sensor approach ensures a comprehensive gas profile.

Q5: Why is accurate gas composition measurement essential before using biogas for combustion or upgrading?
A: Because methane concentration and CO₂ ratio directly determine the biogas’s calorific value and suitability for combustion or injection. If you over or under estimate these values, you risk poor combustion, reduced energy output, or safety hazards. Accurate measurement helps optimize performance and avoid costly mistakes.

Q6: What safety and equipment protection benefits come from using an analyzer that combines NDIR with other sensors?
A: Such an analyzer can detect contaminants like H₂S, residual O₂, moisture, or trace toxins. This helps prevent corrosion, engine damage, toxic exposure, or explosive hazards when biogas is sent to engines, pipelines, or storage. It also supports timely corrective actions like scrubbing or gas rejection.