Ash Grove Dairy Began Making Renewable Gas from Manure, Producing up to 480,000 Gallon-Equivalents
Ash Grove Dairy operates on a 55-acre farm near Lake Benton, Minnesota. Its renewable natural gas facility processes as much as 60,000 gallons of cow manure per day and converts the waste into biomethane for commercial transport. Clean Energy Fuels said the plant had officially connected to the national pipeline network.
Dynamic Renewables built the facility through a $22 million joint venture led by Clean Energy Fuels Corp. Once operating at its stated capacity, the plant is expected to produce about 480,000 gasoline-gallon equivalents of fuel each year. The gas enters interstate pipelines and is distributed through Clean Energy Fuels’ refuelling network.
Manure is collected during the day and transferred to sealed anaerobic digesters. In the oxygen-free tanks, microorganisms break down the organic material while methane is captured instead of being released from storage ponds. The resulting biogas is treated to remove water, hydrogen sulphide, carbon dioxide and other impurities.
After purification, the biomethane has the same chemical properties as conventional natural gas. It is compressed and injected into the commercial pipeline system, from which Clean Energy Fuels supplies stations used by transit buses, municipal refuse trucks and long-haul freight vehicles across North America.
Ash Grove was the fifth renewable natural gas facility that Clean Energy Fuels brought online within nine months. Clay Corbus, the company’s senior vice-president, said: “Ash Grove is our fifth renewable natural gas facility to come online in the last nine months. With the growing demand for RNG, and interest really starting to take off as fleets realize how effective and immediate they can fuel cleanly, the RNG produced at Ash Grove will directly help with reducing carbon emissions across the country.”
Fuel made from dairy waste receives a negative carbon-intensity score under lifecycle standards, including California’s Low Carbon Fuel Standard, because the digesters capture methane that would otherwise escape into the atmosphere. The process also produces digestate, which is separated into solid and liquid fractions. Solids can be used as animal bedding or made into a soil conditioner, while the liquid fraction can be applied to fields as a more stable, lower-odour fertiliser.
Farm Progress reported that the system provides family-owned dairy farms with an additional income source and changes how nutrients are handled on farmland. Agriculture accounts for about 10% of greenhouse-gas emissions in the United States, while livestock-manure management contributes a portion of that total.
