Hennepin County exploring anaerobic digestion for organics

Hennepin County is exploring the potential of processing organic waste through anaerobic digestion.

The county is looking to find an entity that could process at least 25,000 tons of organic waste annually via anaerobic digestion. It’s requesting that potential vendors for the project submit their qualifications and preliminary plans for anaerobically digesting the waste by early September.

Anaerobic digestion is a series of processes in which microorganisms break down biodegradable material in the absence of oxygen, according to the American Biogas Council. The processes lead to the creation of biogas, which can be combusted to generate electricity and heat or can be processed into renewable natural gas and transportation fuels, according to the council.

The county’s request for information comes as it works toward the goal of recycling 75 percent of waste by 2030. The county specified the goal in its Solid Waste Management Master Plan, which the Board of Commissioners approved last November.

Organic materials comprise about 30 percent of the trash stream, according to the county, and about 30 percent of those materials are currently diverted from landfills. The county hopes to be diverting roughly half of all organic waste from landfills by 2030. It’s planning to require businesses that generate large quantities of food waste to implement food recycling by 2020 and for most cities to make curbside organics service available to residents by 2022. Those requirements are pending passage of an updated recycling ordinance later this fall.

Paul Kroening, recycling program manager for Hennepin County, said there’s currently enough capacity for cities in the county to process their organic waste. But he said the county will eventually need more capacity to process organics.

Kroening said the anaerobic digestion facility would take three to five years to get up and operating, at which point the county expects to be collecting more organic material. The county’s request for qualifications asks for vendors that can anaerobically digest a minimum of 25,000 tons of waste per year. But it says the county is open to additional capacity.

The county closed the public comment period for its revised recycling ordinance on Aug. 17, and it will present a version to the county board next month. Visit hennepin.us/solidwasteplanning to learn more about the ordinance.