H₂S Monitoring in Biogas & Renewable Natural Gas

Verifying Desulfurization Performance from Digester to Pipeline Injection — H2S-625

Raw biogas from anaerobic digesters and landfills can contain hydrogen sulfide ranging from a few hundred to several thousand ppm, far above what pipeline injection or engine-generator use will tolerate. Desulfurization systems, from biological scrubbers to activated carbon or iron sponge media, are used to bring H2S down to acceptable levels before the gas is used or upgraded to renewable natural gas.

The H2S-625 supports this process by monitoring H2S at the raw gas inlet and again after treatment, confirming the scrubber system is performing and the gas meets pipeline injection or equipment protection requirements.

Why H₂S Monitoring in Biogas Systems Matters

High H2S in raw biogas is corrosive to combined heat and power engines and generators, and it poses a health hazard to personnel working around digesters and gas handling equipment. Renewable natural gas injected into a pipeline must meet the same strict H2S specification as conventional pipeline gas, often just a few ppm, making reliable monitoring of desulfurization performance essential before injection.

Where It's Used

Raw digester gas monitoring — establishing baseline H2S entering the treatment system
Scrubber and desulfurization outlet verification — confirming treatment media is performing
RNG pipeline injection quality checks — verifying gas meets pipeline H2S specification
Biogas CHP engine protection — monitoring fuel gas quality ahead of engines and generators

Recommended Analyzer

H2S-625 Continuous H₂S Process Analyzer

The H2S-625 is available in configurations suited to both high-ppm raw biogas monitoring and low-ppm verification of treated, pipeline-ready gas, making it adaptable across a biogas upgrading facility.

Continuous output lets facility operators trend desulfurization performance over time and identify media replacement or scrubber maintenance needs before treated gas quality is affected.

Key Specifications

Range: high-ppm option for raw digester gas, low-ppm option for treated/RNG verification
Wetted materials: selected for resistance to wet, corrosive biogas conditions
Sensor technology: electrochemical sensor rated for continuous sour gas duty
Output: 4-20 mA and HART for integration with facility control systems
Enclosure: suitable for outdoor digester and gas upgrading skid installation

Frequently Asked Questions

How much H₂S is typically present in raw digester or landfill gas?

Trace oxygen measurement provides a direct indication of oxygen contamination or crossover into the hydrogen stream. Trending the oxygen concentration can help operators identify changes in electrolyser or purification system performance.

What H₂S level is required before RNG can be injected into the pipeline?

A common measurement point is the hydrogen product stream downstream of the electrolyser stack. Additional measurement points may be used before or after drying and purification equipment depending on the process design and monitoring objectives.

Can the same analyzer platform monitor both raw and treated biogas?

Alarm and control limits should be determined based on the electrolyser manufacturer’s specifications, process conditions, applicable standards, and the facility’s safety requirements rather than using a universal oxygen alarm value.

NEED HELP SPECIFYING AN ANALYZER FOR YOUR OPERATION?

Our application engineers can help confirm the right model for your process conditions.

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