Weltec Biopower builds biomethane plant in Wisconsin, US
Credit: Weltec Biopower
In February 2025, the German biogas specialist Weltec Biopower has completed the commissioning and handover of a dairy RNG (renewable natural gas/biomethane) plant in Barron County, Wisconsin in the US. After four months of construction, the dairy farm produces 2.36 million standard cubic metres of RNG/biomethane annually. This RNG, above gas grid specifications, is processed using advanced membrane-based gas upgrading technology to deliver 272 standard cubic metres per hour, which is compressed, bottled and transported to a gas grid injection point. This strongly carbon-negative RNG is drawn off the gas grid elsewhere, significantly enhancing the sustainability of the transportation fleets of the buyers, the company says.
The farm currently has a herd of 3,400 cattle, primarily Holsteins along with a select number of Swiss cows. The owners previously operated an AD plant producing electricity for on-site use, so the concept was not new for them. “For years, we have been utilising cattle manure to generate biogas, meeting our farm’s electricity and heating needs while also fertilizing our fields with digestate,” said the owner. “With the new RNG facility, we have expanded our digestate utilisation on a larger scale and now store it in our dedicated lagoon for optimal land application.”
Weltec Biopower built three 6,850 cubic metre duplex stainless steel digesters for the new biomethane plant near Rice Lake. “We constructed the tanks using a ring-by-ring assembly approach, with the final step involving the installation of a gas-tight membrane storage roof,” according to Weltec Biopower North America COO Carsten Hesselfeld. With a diameter of 31.48 metres, the 8.8 metre high, insulated stainless steel tanks each have a gas storage volume of 3,320 cubic metres. “Our modular construction method contributed significantly to the short construction time of the plant,” says Hesselfeld. The plant is designed to process 207,000 metric tonnes of cattle manure annually, with some flexibility to incorporate future increases in herd size.
The facility employs a streamlined process flow, with manure fed from the barns into a 1,543 cubic metre stainless steel pre-storage tank before being pumped into the digesters. The digestion system has a retention time of 34 days, before the biogas is upgraded in a membrane-based system (specified, purchased and integrated into the central SCADA system under a Weltec Biopower contract) into RNG at gas grid specifications.
Digestate is pumped from the RNG plant to the existing lagoons. The company designed and supplied key components for the project, including digesters, a prefabricated containerised pump-block system, heating and boiler containers and a prefabricated factory-tested control container to simplify works on site, enhance the fast construction time and ensure optimal operational efficiency.
By using biomethane as a fuel source, the dairy achieves substantial environmental benefits, reducing carbon emissions by approximately 11,200 tonnes of carbon dioxide equivalents annually. Additionally, the plant owners capitalise on financial incentives such as RNG tax credits and fuel tax allowances.
Projects such as this have a key part to play in de-carbonising North American agriculture, and de-carbonising US truck fleets, the firm notes.
You can also see a video about the biomethane plant in Barron County, Wisconsin here.
