Anaerobic digestion  (energy & composting) facility

The MRWMD dry anaerobic digestion (AD) pilot project, commissioned in 2013, was the first of its kind in the U.S.  This 5,500 ton per year pilot project was a public-private partnership between MRWMD and Zero Waste Energy (ZWE) that ended in fall 2019.

The four shop fabricated steel digesters accepted 5,500 tons per year of a blend of 70% of food scraps and 30% of yard trimmings, mixed and loaded into an air-tight chamber where naturally occurring microorganisms are introduced via a liquid “percolate”. Over a 21 day process, these organisms broke down the biodegradable materials to produce methane gas with a minor amount of carbon dioxide. These biogases were then filtered and cleaned to power a combined heat and power engine that produces electricity. Waste heat was captured and reused to maintain a constant 130 degree percolate temperature.

Energy from the project supplied 10 percent of the electricity need for the neighboring Monterey Regional Water Pollution Control Agency. The “digestate” that came out of the digesters then underwent a complete windrow composting process by Keith Day Company to complete the decomposition process.

The success of the Organics to Energy compost program was attributable to the program participants: the commercial businesses that diligently separated food scraps, the haulers that collected it, and our public-private partnerships with Zero Waste EnergyKeith Day Company, and our neighboring public agency the Monterey Regional Water Pollution Control Agency who received the electricity produced through anaerobic digestion.

In addition to the environmental benefits of participating in Organics to Energy, state law AB 1826 is now requiring organics generators to sign up for compost service.

The District continues to accept food scraps for composting in windrows at Keith Day Company and is planning for the future of organics under SB 1383. It is possible that a larger anaerobic digestion facility will be built following the success of the initial pilot project.

“The AD pilot project is an important next step for our community in
utilizing “waste as a resource,” while maximizing the opportunity to realize
value from the materials we receive and helping businesses meet the
regulatory requirements of AB 1826.”

                                                                                 General Manager, Tim Flanagan

Links

Take A Virtual Video Tour of the AD Facility

Public Education:
Angela Goebel
agoebel@mrwmd.org
831-264-6382