Siloxane and VOC Removal Systems for Biogas

Siloxanes are among the most damaging contaminants in biogas.

When biogas containing siloxanes is combusted in engines, turbines, or boilers, those compounds oxidize into silicon dioxide that deposits on internal surfaces. The result is accelerated wear, increased maintenance costs, shortened equipment life, and, in severe cases, catastrophic engine failure.

The challenge: Siloxanes are present in virtually all biogas derived from municipal wastewater and landfill sources. They originate from consumer products, such as soaps, shampoos, cosmetics, and personal care items, that enter the waste stream and volatilize during anaerobic digestion or decomposition.

You can’t eliminate them at the source. You have to remove them from the gas.

Volatile organic compounds (VOCs) frequently co-occur with siloxanes, adding emissions concerns and potential interference with downstream equipment and catalytic systems. Like siloxanes, they require treatment at the gas conditioning stage.

Unison Solutions designs and builds siloxane and VOC removal systems for biogas applications of all sizes and contamination levels.

Every system is engineered to match your specific gas composition, flow rate, and end-use requirements. Contaminant profiles vary widely, so a one-size-fits-all solution often isn’t a solution at all.

Why Siloxane Removal Matters

Siloxane compounds convert to silicon dioxide (SiO₂) during combustion. This abrasive white powder deposits on:

• Engine cylinder heads and pistons, causing scoring and accelerated wear
• Turbine blades, reducing efficiency and requiring costly refurbishment and recuperators
• Spark plugs and valves, leading to misfires and reduced engine performance
• Catalyst surfaces in oxidation systems, reducing catalytic effectiveness
• Coat boiler tubes, reducing thermal efficiency

Even relatively low siloxane concentrations can cause meaningful damage over time. Facilities that skip siloxane treatment often find themselves facing repair and downtime costs that dwarf the cost of a proper removal system.

Unison’s Siloxane and VOC Removal Solutions

Unison offers two proven approaches to siloxane and VOC removal, selected based on your contaminant loading, gas flow rate, and operational priorities.

Non-Regenerable Media Systems

For applications with low to moderate siloxane and VOC concentrations, activated carbon-based static bed media systems provide reliable, cost-effective removal.

Biogas passes through vessels packed with high-performance adsorption media, where siloxanes and VOCs are captured before the gas reaches downstream equipment.

Unison’s media systems are designed for straightforward operation and minimal operator interface. When the media reaches capacity, it is replaced. Our service team can support that process through our media supply and replacement program.

Best suited for: Applications with manageable siloxane and VOC concentrations where repeated media replacement is an acceptable operating model.

Regenerative Siloxane/VOC Reduction

For high-siloxane applications, which are common at larger landfill and wastewater sites, Unison’s regenerative Temperature Swing Adsorption (TSA) systems offer a more economical long-term solution.

Rather than replacing media when it becomes saturated, TSA systems regenerate the adsorbent bed in place using a thermal cycle, restoring removal capacity with media replacement required in longer intervals.

This approach significantly reduces ongoing operating costs at sites where siloxane loading would otherwise require frequent media changeouts.

Best suited for: Higher-flow applications, facilities with elevated siloxane concentrations, or operations where minimizing ongoing media costs is a priority.

VOC Removal

Volatile organic compounds (VOCs) frequently co-occur with siloxanes in biogas, particularly at municipal wastewater treatment plants, landfills, and industrial digesters. VOCs contribute to emissions, affect gas quality, and sometimes interfere with downstream equipment and catalytic systems.

The activated carbon media used in Unison’s static bed and TSA systems is effective at capturing a broad range of VOCs in addition to siloxanes. For sites with significant VOC loading, Unison’s engineers can select and configure media specifically to target your VOC profile alongside siloxane removal.

Engineered for Your Application

No two biogas streams are identical. Siloxane and VOC concentrations at a food processing digester can differ dramatically from those at a municipal wastewater plant or landfill.

Unison’s engineering team analyzes your gas composition data to size and configure the right system for your conditions.

Every Unison siloxane and VOC removal system is:

• Custom-engineered for your gas flow, contaminant loading, and end-use application
• Manufactured in-house at our facility in Dubuque, Iowa, with no subcontractors or outsourced fabrication
• All media vessels are designed per ASME and hydrotested.
• Designed to integrate with broader biogas conditioning systems, including H₂S removal, compression, drying, and upgrading

If you’re building a complete biogas conditioning system or upgrading an existing one, siloxane and VOC removal is typically one component of a larger treatment train. Unison can design and supply the full system.

Siloxane, H2S, and VOC Removal Media Supply

Unison can provide a range of activated carbon, silica-based, and iron-based media for siloxane, VOC, and H₂S removal, including media for systems we didn’t manufacture.

Learn more about our removal media here.

Not sure which system is right for your application?

Not sure what’s in your gas stream? Start with a biogas test.

Unison’s engineers can review your gas analysis data and recommend the appropriate siloxane and VOC removal approach. If you don’t yet have gas analysis data, our biogas testing service(LINK) can establish a baseline.

For biogas with high levels of siloxanes or VOCs, we offer Regenerative Siloxane Removal  systems.