A diversified energy company partnered with two dairy farms to help them turn dairy manure into renewable natural gas (RNG). We provided engineering, procurement, and construction (EPC) for this multi-farm RNG facility in South Dakota. Two miles of piping move manure from the dairy farms—with approximately 12,000 cows combined—to a central location for anaerobic digestion. Our design included adaptability to accept manure trucked in from a third farm and the ability to return digestate to the third farm, as needed. Four anaerobic digesters, two million gallons each, convert the manure waste stream into raw biogas. Biogas treatment consists of two feed compressors with aftercoolers, a two-stage membrane system, a gas dryer, a final compressor, a flare, and a thermal oxidizer. We custom fabricated a skid-mounted boiler system, which supplies heat to the digesters. We utilized a temporary heat source and purchased seed sludge to expedite digester start-up and start producing gas faster.
Eight miles of custom-installed pipeline transports upgraded RNG to the Northern Natural Gas Co. utility pipeline injection point. The RNG facility converts 990 SCFM of biogas into 575 SCFM of pipeline-ready RNG.
