WELTEC BIOPOWER Completes Dairy RNG Plant in Barron County, Wisconsin, USA

In February 2025, the German biogas expert WELTEC BIOPOWER announced the successful 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 now produces 2.36 million standard cubic meters of RNG annually (86,600 MMBTU per year). This RNG, which exceeds gas grid specifications, is processed using advanced membrane-based gas upgrading technology to produce 272 standard cubic meters per hour (159 SCFM). The gas is then compressed, bottled, and transported to a grid injection point, providing a highly carbon-negative fuel source. This RNG is used elsewhere on the gas grid, helping to reduce the carbon footprint of transportation fleets.

Sustainable Agricultural Practices

The dairy farm is home to 3,400 cattle, primarily Holsteins with a few Swiss cows. The farm's owners have a long history with biogas, having previously operated an anaerobic digestion (AD) plant to generate electricity for the farm’s own use. “For years, we’ve been using cattle manure to produce biogas, which supplies electricity and heating to the farm while also fertilising our fields with digestate,” said the farm’s owner. “With the new RNG facility, we’ve expanded our digestate utilisation and now store it in a dedicated lagoon for optimal land application.”

Modular Design Ensures Quick Construction

WELTEC BIOPOWER built three 6,850 cubic meter (1.8 million USG) duplex stainless steel digesters for the new plant, located near Rice Lake. “We used a ring-by-ring assembly technique, finishing with the installation of a gas-tight membrane storage roof,” explained Carsten Hesselfeld, COO of WELTEC BIOPOWER North America. Each tank, with a diameter of 31.48 meters and a height of 8.8 meters, has a gas storage volume of 3,320 cubic meters. “Our modular construction method, refined over more than 20 years worldwide, helped to minimise the plant’s construction time,” added Hesselfeld. The facility is designed to process 207,000 metric tonnes of cattle manure annually (150,000 USG per day) and has room for future expansion as the herd grows.

Efficient Biomass Processing and Energy Output

The plant uses an efficient process flow: manure is fed from barns into a 1,543 cubic meter (408,000 USG) stainless steel pre-storage tank before being pumped into the digesters. The digestion process lasts 34 days, after which the biogas is upgraded in a membrane-based system (specified, purchased, and integrated into the SCADA system by WELTEC BIOPOWER) to meet gas grid specifications. The digestate is then pumped to existing lagoons. Key components for the project, including digesters, a prefabricated pump-block system, heating and boiler containers, and a control container, were designed and supplied by WELTEC BIOPOWER, ensuring efficient construction and optimal operational performance.

Environmental and Financial Benefits

By using biomethane as a fuel, the farm significantly reduces its carbon emissions by approximately 11,200 tonnes of CO2 equivalents annually. Additionally, the plant owners benefit from financial incentives like RNG tax credits and fuel tax allowances. This project, with its highly negative carbon footprint, rapid construction, and relatively low capital expenditure, exemplifies the enormous potential for biogas and RNG development at smaller dairy farms across the U.S. Initiatives like this are crucial in reducing the carbon footprint of North American agriculture and truck fleets. Through this successful dairy RNG project, WELTEC BIOPOWER continues to lead in innovation, providing high-quality and cost-effective solutions for dairy RNG developers while expanding expertise in the co-digestion market.

You can also watch the video about the biomethane plant in Barron County, Wisconsin here.