How PSB Industries Optimizes RNG Projects with Catalytic Oxidation
As renewable natural gas (RNG) projects at landfills and dairies scale up, operators are discovering that methane is only part of the value story. The CO₂-rich off-gas stream that follows methane recovery can either drag down carbon intensity scores, or become a high-purity product that unlocks new revenue when it is properly purified.
PSB Industries helps RNG developers make that pivot, using catalytic oxidation-based VOC removal to transform CO₂ off-gas from a compliance obligation into a strategic asset.
Why CO₂ Off-Gas Can’t Be an Afterthought
Most landfill and dairy RNG facilities were originally designed around one primary goal: capture methane, upgrade it, and deliver pipeline-quality gas or transportation fuel. Membranes, PSA, and amine systems do this effectively, but they leave behind a CO₂-rich stream that has often been vented, reused for regeneration, or fed to thermal oxidizers when VOCs are present.
That approach is becoming harder to justify because CO₂ venting can worsen a project’s carbon intensity (CI) score, while purified CO₂ can be sold into beverage-grade and industrial markets where local supply is tight. At the same time, CO₂ off-gas from RNG sites is rarely clean enough for direct reuse and typically carries oxygen, moisture, siloxanes, hydrogen sulfide, and variable VOC levels that must be driven to single-digit ppm to meet strict specifications.
VOC Removal with Catalytic Oxidation
Traditional VOC removal methods such as temperature swing adsorption (TSA) or other media-based systems can capture contaminants, but they introduce added complexity and recurring media changeouts that increase long-term operating costs.
Catalytic oxidation takes a different approach by converting VOCs directly into CO₂ and water via reaction with oxygen in a precious-metal catalyst bed. Because the process is continuous and once-through, VOCs are destroyed rather than stored, and the primary byproduct, additional CO₂, aligns with the desired product stream.
Engineering an Integrated CO₂ Purification Train
Designing catalytic oxidation for RNG CO₂ requires careful control of flow rate, pressure, VOC loading, oxygen availability, temperature, and residence time to achieve high VOC destruction while minimizing methane loss and capital cost. Upstream H₂S and siloxane removal protects the catalyst, while downstream drying removes water generated during oxidation to meet tight moisture specifications in the 15–20 ppmv range.
When properly integrated, catalytic oxidation works as part of a broader purification train alongside front-end contaminant removal and back-end drying to deliver high-purity CO₂.
Environmental and Economic Upside
Treating and capturing CO₂ off-gas instead of venting it supports better carbon accounting and can help projects move closer to carbon-negative performance in certain configurations. Compared to thermal oxidizers, catalytic systems typically run at lower temperatures, reducing fuel use and enabling heat integration that lowers total cost of ownership over time.
Lifecycle economics also favor catalytic oxidation. While media-based systems may appear inexpensive at commissioning, frequent media replacement over four to five years can drive operating expenses steadily higher. Properly engineered catalyst beds often deliver multi-year lifetimes, reducing consumables and simplifying operation.
From Byproduct to Strategic Asset
PSB Industries specializes in integrated systems for dehydrating and purifying gases and liquids, tying catalytic oxidation to upstream impurity removal and downstream drying in cohesive process trains. This approach protects catalyst life, maintains moisture compliance, preserves methane recovery, and supports stable multi-year operation.
As landfill, dairy, and other CO₂-focused RNG projects mature, CO₂ off-gas is shifting from nuisance stream to revenue-generating product. With catalytic oxidation-based VOC removal and integrated CO₂ purification solutions, PSB Industries helps operators turn CO₂ off-gas into a cleaner, more valuable component of the overall project.