Hydrogen Sulfide (H2S) Removal Systems for Biogas

Hydrogen sulfide (H₂S) is one of the most common — and most problematic — contaminants in biogas.

Present in virtually every anaerobic digestion and landfill gas stream, H₂S is corrosive and toxic. If left untreated, it will degrade downstream equipment, increase maintenance costs, and create compliance problems. Effective removal is critical to any biogas system.

Unison Solutions has designed and manufactured H₂S removal systems for more than 25 years, serving wastewater treatment plants, landfills, agricultural digesters, and food processing facilities across the U.S. and Canada. We offer multiple removal technologies and media options, and our in-house engineering team will evaluate your specific biogas chemistry to recommend the right solution for your application.

Why H₂S Removal Matters

Hydrogen sulfide causes problems at every stage of a biogas system.

• Equipment corrosion: H₂S reacts with moisture to form sulfuric acid, aggressively corroding compressors, heat exchangers, engines, and piping. Even moderate H₂S concentrations — in the range of hundreds of ppm — will shorten equipment life significantly.
• SO₂ emissions: When H₂S-laden biogas is combusted, it produces sulfur dioxide (SO₂), which is a regulated air pollutant. H₂S removal is often required to meet air permit limits.
• Siloxane/VOC removal interference: H₂S can compete with and reduce the effectiveness of removal media for siloxane/volatile organic compounds (VOC), making it important to address H₂S first.
• Pipeline and RNG quality standards: Natural gas pipeline interconnection requirements set strict limits on H₂S content. RNG producers must achieve consistent, reliable removal to meet these specifications.
• Worker safety: H₂S is acutely toxic. At concentrations above 100 ppm, it can cause immediate collapse and death. OSHA and other regulatory bodies set strict exposure limits that biogas facility operators must manage.

H₂S Concentrations Vary Widely by Source

H₂S concentration can vary dramatically depending on the feedstock and digester type. A solution that works well for one application may be undersized or over-engineered for another.

• Wastewater treatment (municipal digesters): Typically 500–3,000 ppm H₂S, though concentrations can spike with certain influent conditions or co-digestion of high-strength waste.
• Landfill gas: Generally lower H₂S levels than digesters — often 50–200 ppm — but highly variable depending on waste composition and landfill age.
• Agricultural (dairy, swine): Can range from a few hundred to typically 3,000-5,000 ppm. High-sulfur feed supplements or co-digested materials can push concentrations significantly higher.
• Food and beverage processing: Highly variable. High-protein or sulfur-rich feedstocks (e.g., brewery waste, food processing residuals) can produce elevated H₂S levels.

H₂S Removal Technologies: Matching the Solution to the Application

Unison offers multiple H₂S removal approaches. Our engineering team evaluates each project individually. We consider H₂S concentration, gas flow rate, target outlet concentration, and end-use application in order to recommend the most cost-effective solution.

Static Bed Media Systems (Fixed Bed Media Vessels)

Media systems are the most widely used approach for biogas H₂S removal. Biogas passes through a vessel containing a reactive or adsorptive media that captures and neutralizes H₂S. Unison designs and fabricates custom ASME and non-ASME stainless steel vessels for static bed applications, sized to the specific H₂S load and target outlet concentration of each project.

We offer a variety of media options for static bed systems, including iron oxide-based media and activated carbon products. Media selection depends on inlet H₂S concentration, gas flow rate, and moisture content. Our team maintains a large inventory of media products for quick delivery, and we provide media replacement services as part of ongoing customer support.

In-Digester H₂S Reduction

For applications where reducing H₂S at the source is preferred, Unison offers an iron oxide-hydroxide-based reduction powder that is added directly to the anaerobic digester. The powder binds hydrogen sulfide within the digester before it enters the gas stream, providing a cost-effective, non-corrosive approach to H₂S management — particularly well-suited for agricultural digesters and situations where upstream reduction can meaningfully reduce the burden on downstream treatment systems.

The Unison Approach: Engineered for Your Specific Biogas Chemistry

No two biogas streams are identical. H₂S concentration, gas flow rate, moisture content, and the target end use all influence which H₂S removal system is right for a given project. Unison’s in-house engineers and chemistry experts use biogas analysis data to specify the optimal technology and media combination.

Because we design, fabricate, assemble, and factory-test all systems at our Dubuque, Iowa facility, we maintain tight control over quality and performance. Custom vessel sizes, materials, and configurations are standard — not exceptions. And because we stock a large inventory of media products, customers can count on fast delivery when it’s time for media replacement.

Get a Custom H₂S Removal Solution

Tell us about your biogas source, flow rate, and H₂S concentration, and we will recommend the right removal approach for your application. Unison’s engineers are ready to help you protect your equipment, meet air permit requirements, and achieve your pipeline or RNG quality targets.