Cooling System Design For Biogas-To-Rng Production Facilities August 4, 2026 Renewable natural gas (RNG) production — upgrading raw biogas to pipeline-quality biomethane — represents the highest-value end use for biogas. The upgrading process that separates methane from CO2 and contaminants also introduces cooling requirements that go beyond standard biogas facility needs. Facilities targeting RNG production must design their cooling systems to support both the anaerobic digestion process and the more demanding thermal management requirements of gas upgrading equipment. What Changes When You Add Upgrading to a Biogas Facility A basic biogas facility that burns gas in a CHP engine has relatively straightforward cooling requirements: digester temperature control and engine heat management. RNG upgrading adds: Gas compression upstream of upgrading: raw biogas must be compressed before entering upgrading systems. Multi-stage compression generates heat at each stage that must be removed by intercooling and aftercooling. Feedgas conditioning cooling: moisture must be removed from the gas before upgrading. Cooling the gas below its dew point condenses water — direct cooling application. Upgrading technology cooling: pressure swing adsorption (PSA), water scrubbing, amine scrubbing, and membrane systems all have specific thermal operating requirements. Product gas compression: biomethane leaving the upgrader typically requires compression to pipeline pressure — another heat generation source. Cooling Requirements by Upgrading Technology Upgrading Technology Cooling System Requirement Pressure Swing Adsorption (PSA) Feedgas cooling for moisture removal; no significant process cooling during separation High-Pressure Water Scrubbing (HPWS) Chilled water injection (35-45 degrees F) improves CO2 absorption efficiency; heat exchanger cooling for recirculated water Amine Scrubbing Significant cooling required for absorber column and amine regeneration heat management; large-scale applications may require dedicated process chiller Membrane Separation Temperature-sensitive membranes require controlled feedgas temperature (typically 50-95 degrees F); cooling may be needed in warm climates to stay within membrane operating range Cryogenic Separation (large scale) Most cooling-intensive; requires refrigeration down to -160 to -170 degrees C for liquefaction; not typical at project scale "RNG projects that aren't designed for the full cooling load — including compression and upgrading — end up with systems that underperform or require expensive retrofits. We see it regularly with facilities that started as biogas-to-power and converted to RNG after the fact."— Andy Backer, VP of North American Sales, G&D Chillers The Compression Cooling Load Gas compression is often the largest single cooling load in an RNG facility's process system. Key calculation parameters: Compression ratio and number of stages: multi-stage compression with intercooling is standard; each stage raises gas temperature substantially Gas flow rate: scales directly with production volume Inlet and outlet temperature targets: intercooler outlet temperature affects compressor efficiency and downstream equipment performance Aftercooler requirement: product gas must be cooled to near-ambient temperature before metering and pipeline injection Integration with Digester Cooling and CHP RNG facilities that also operate CHP engines (for internal power generation) can integrate cooling loads more efficiently: Engine waste heat can offset digester heating requirements, as in standard biogas-to-power design In summer, surplus engine waste heat plus upgrading process cooling requirements may together justify a larger chiller plant than either load alone would require Facilities that sell all gas to pipeline (no CHP) lose the heat recovery benefit and must provide digester heating from a dedicated source Frequently Asked Questions Does RNG upgrading increase total facility cooling load significantly? Yes, meaningfully. Gas compression and conditioning typically add 20-50% to the cooling load of an equivalent biogas-to-power facility, depending on throughput, upgrading technology, and compression ratio. Facilities planning to add upgrading to an existing system must evaluate whether existing chiller capacity is adequate. What coolant is used for high-pressure water scrubbing systems? HPWS systems typically use chilled water at 35-45 degrees F, produced by a dedicated process chiller, to cool the scrubbing water before the absorber column. The chiller must reliably maintain this temperature range across variable ambient conditions — air-cooled chillers with capacity for the hottest summer conditions are required. > Design cooling infrastructure for your RNG upgrading facility -> Contact us