Construction and Operation of the ABEC #3 Covered Lagoon Digester and Electrical Generation System

ABEC #3 LLC, DBA Lakeview Farms Dairy Biogas installed and demonstrated an innovative covered lagoon digester system that processes dairy manure into biogas to generate renewable electricity for export to the electricity distribution grid.
This project documented the construction and one year of operation of the ABEC #3 LLC (ABEC #3) covered lagoon digester, which has a volume of 18.5 million gallons, along with a 1-megawatt engine-generator. Construction of the digester was completed in 2017 along with start-up and commissioning using flushed manure from 4,168 “manure equivalent milkers” as influent (one manure equivalent milker represents 100 percent of the manure from a Holstein cow weighing 1,360 pounds). Full operation commenced in February, 2018.
Through the end of December 2018, ABEC #3 averaged 374,000 cubic feet per day of biogas containing 61 percent methane, approximately 90 cubic feet of biogas per cow per day. The monthly gross electrical production over this period averaged 607,000 kilowatt-hours for 614 hours of operation (out of a possible 720 hours), averaging 985 kilowatts. The parasitic load was 43 kilowatts or 4.3 percent, and the net monthly energy sold to Pacific Gas and Electric Company averaged 580,000 kilowatt-hours.
The average monthly income for the project was approximately $116,000, with a simple payback of 7.5 years based on $7.925 million total installed capital cost and average monthly operating costs of $27,500. The project provided the additional benefit of producing an average of 99 tons per day of fiber bedding and fertilizer.
The environmental benefits of the project included reduction of nearly 11,000 metric tons of carbon dioxide equivalent greenhouse gases, principally methane, along with keeping exhaust emissions at 2.3 parts per million (ppm) of oxides of nitrogen and 10 ppm carbon monoxide, well under California Air Resources Board limits. Progress was made in limiting hydrogen sulfide emissions, thus prolonging the life of the engine-generator. Levels ranged from a high of 1,000 ppm to a low of 193 ppm, averaging 582 ppm for the year while using only the air injection system, and a final iron sponge scrubbing resulted in hydrogen sulfide levels of 5 ppm going into the engine-generator.