Of those, most are plug-flow digesters, complete-mix systems or covered lagoons. The U.S. swine industry accounts for the second-highest number of commercial anaerobic digesters, with 39.

Nearly six years in the making, the $9.5 million renewable energy project relies on manure piped from a dairy a mile away to an anaerobic digester ... The Pixley biogas digester is a two-stage, ...