Holsum Dairies completed Wisconsin’s first anaerobic digester 20 years ago. The digester, which was part of a combined heat and power system, combined cow manure with heat and bacteria to create biogas, which was used to power a generator. At the moment, it was a new experiment. The digester, as well as another one built a few years later by the dairy, helped to minimise the size of open manure lagoons that released methane into the atmosphere.
The energy was purchased by Wisconsin Public Service, the local utility. Holsum Dairies, on the other hand, changed course last year, upgrading the two digesters and starting to produce renewable natural gas for California’s burgeoning renewable fuels market. Dr. Robert Nagel, the Holsum Dairies owner, said, “California’s market is the biggest driver, for sure.”
Renewable natural gas would be used to offset pollution from current natural gas-fueled vehicle fleets including transit buses, trucks, vans, and other multi-passenger vehicles under the programme. Refineries, importers, and wholesalers in California earn credits for purchasing renewable fuels that reduce the total carbon intensity of the fuels they supply. The controlled parties monitor the deficits and credits from fuel purchases using a complex reporting method.