WELTEC BIOPOWER hands over dairy RNG plant in Wisconsin, USA  

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In February 2025, the German biogas specialist WELTEC BIOPOWER has successfully completed the commissioning  and handover of a dairy RNG (Renewable Natural Gas / biomethane) plant in Barron County, Wisconsin. After  just four months of construction, the dairy farm produces 2.36 million standard cubic meters of RNG/biometha ne annually (86,600 MMBTU per year). This RNG, above gas grid specifications, is processed using advanced  membrane-based gas upgrading technology to deliver 272 standard cubic meters per hour (159 SCFM), 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. 

Sustainable agricultural practices  

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 utilizing 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  utilization on a larger scale and now store it in our dedicated lagoon for optimal land application.”  

Four months construction time thanks to modular design  

WELTEC BIOPOWER constructed three 6850 cubic meter (1.8m USG) 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,” explains responsible WELTEC BIOPOWER North  America COO Carsten Hesselfeld. With a diameter of 31.48 meters, the 8.8 meter high, insulated stainless steel tanks  each have a gas storage volume of 3320 cubic meters. “Our modular construction method, tried and tested worldwide  over the past 20+ years, contributed significantly to the short construction time of the plant,” emphasizes Hesselfeld.  The plant is designed to process 207,000 metric tonnes of cattle manure annually (150,000 USG per day), with some  flexibility to incorporate future increases in herd size.  

Efficient Biomass Processing and Energy Output  

The facility employs a streamlined process flow, with manure fed from the barns into a 1,543 cubic meter (408,000  USG) 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 WELTEC BIOPOWER contract) into high-quality RNG at gas grid specifications.  Digestate is pumped from the RNG plant to the existing lagoons. WELTEC BIOPOWER 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.  

Savings through CO2 equivalents and tax benefits  

By utilizing biomethane as a fuel source, the dairy achieves substantial environmental benefits, reducing carbon  emissions by approximately 11,200 tonnes of CO2 equivalents annually. Additionally, the plant owners capitalize on  financial incentives such as RNG tax credits and fuel tax allowances. This project (particularly the strongly negative  RNG, the fast construction time and the relatively low CAPEX for such a project) is a great example of the huge  potential that still exists for biogas/RNG development at some of the smaller dairy farms in the USA. Projects like  this have a key part to play in de-carbonising North American agriculture, and de-carbonising US truck fleets. With  the successful implementation of this dairy RNG project, WELTEC BIOPOWER continues to drive innovation, quality  and cost-effective solutions for dairy RNG developers, as well as continuously developing market-leading expertise  in the co-digestion market.

Forward-looking statements

Although the forward-looking statements contained in this presentation are based on what the Company‘s management believes to be reasonable assumptions, there can be no assurance that the forward-looking statements will prove to be accurate, as actual results and future events could differ materially from those anticipated in such statements. The Company undertakes no obligation to update forward-looking statements should circumstances or management‘s estimates or opinions change, except as required by applicable law. Readers are cautioned not to place undue reliance on forward-looking statements.

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