The number of on-farm anaerobic digester systems in the United States has been steadily rising since 2000, according to [1]AgSTAR, a collaborative program sponsored by the Environmental Protection Agency and USDA. As of June 2024, there were 400 operational manure-based projects across the country, converting farm waste into valuable resources while reducing greenhouse gas emissions. USSA had the opportunity to visit one such site with a group of EU officials for first-hand insights into the environmental benefits of anaerobic digestion.
Established in 1873, Sievers Family Farms in Stockton, Iowa, exemplifies sustainable agriculture through its closed-loop approach. The fifth-generation farm grows corn, soy, hay, winter wheat, and cover crops, and operates a beef feedlot on approximately 1,000 hectares of land.
Over a decade ago, a decision to grow the business led husband-and-wife team Bryan and Lisa Sievers to take a new, more circular path.
They planned to add two new barns to increase their feedlot capacity from 400 to more than 2,400 head of cattle. However, they were concerned about the additional animal waste this six-fold expansion would bring, not to mention its carbon footprint.
Their solution was to install two anaerobic digesters, each with a volume of 970,000 gallons, to manage the waste and reuse it in their operation. The digesters process manure and other organic waste, including food waste from local food processors, corn stover and wheat straw harvested from the surrounding fields, and, more recently, biomass from their cover crops, to capture methane and generate biogas. This biogas powers a Combined Heat and Power Plant (CHP) unit.
The system produces enough electricity to run the expanded feedlot, and the farm sells any surplus electricity to the local grid. In addition, the solid byproduct from the anaerobic digesters is used for animal bedding and compost, and the liquid byproduct serves as fertilizer, which has significantly improved soil quality on the farm.
Highlighting the environmental benefits, Bryan Sievers said, “The impact we’ve seen already on soil health and air and water quality has been tremendous. We have the ability to sequester carbon while enhancing yields and having a positive impact on the resources we’re blessed with.”
[1] https://www.epa.gov/agstar/agstar-data-and-trends#adfacts