What is anaerobic digestion?

Anaerobic digestion, sometimes referred to as “AD,” is a natural, biological process that breaks down organic matter without oxygen. Watch our video to learn about the process of anaerobic digestion and the benefits the facility would provide.

The following video explains how organic waste collected from homes, schools, and businesses would be brought to the facility, shredded, and loaded into a digestion tank. In the tanks, microorganisms would work to break the materials into two products:

• Biogas, which can replace fossil fuels for heating or be converted into a vehicle fuel that has the lowest carbon footprint of any vehicle fuel.
• Digestate, which is separated into liquids that can be used to replace fossil-fuel-based fertilizers and solids that become a nutrient-rich compost to help plants grow.

The Hennepin County Anaerobic Digestion Facility and Eco-Center video also shares our vision to establish an Eco Center that provides educational experiences, houses a green jobs learning center, includes an on-site urban farm and greenhouses, and delivers healthy food to our hunger relief partners. These strategies would help advance our climate action, zero waste, and healthy community goals.

Infrastructure development needs to keep pace with organics collection programs

Minnesota law requires metro counties achieve a 75% recycling rate by 2030. Waste sort studies continue to show that organic materials are the largest proportion of our trash — about 30%. Organics recycling is our biggest opportunity to reduce our trash.

• Organics recycling continues to increase due to the recent Hennepin County requirements for certain businesses to recycle organics. The county also requires cities to make organics recycling service available to residents.
• The metro area is served by only two organics composting sites that are at or near capacity.
• Anaerobic digestion provides an opportunity to expand and diversify local organics infrastructure.

Anaerobic digestion is a higher and better use of material

• The EPA’s food waste hierarchy prioritizes anaerobic digestion over composting.
• AD transforms organic waste into two main products: 1) biogas, an energy source, and 2) digestate, a nutrient-rich fertilizer.
• Biogas from AD can displace dirty fossil fuels for heating and electricity generation. It can also be converted into biofuels for vehicles. The digestate can replace fossil fuel-based fertilizers.

Action on organics recycling is needed to meet our climate goals

• Food and organic material produces methane when it decomposes in landfills. Methane creates a warming effect 84 times greater than carbon dioxide over a 20-year period. Climate experts rank reducing methane from landfills as a top strategy for rapidly slashing greenhouse gas emissions.
• Diverting more organics from the trash through AD is one of the county’s foundational strategies in the Climate Action Plan to achieve net zero emissions by 2050.
• Methane created and captured from the controlled process of anaerobic digestion reduces greenhouse gas emissions effectively and creates beneficial products, such as renewable natural gas, fertilizer and compost.
• The proposed site's close proximity to the county's Brooklyn Park Transfer Station will also reduce emissions from transporting the material to composting sites and help reduce the cost of organics recycling by providing the opportunity to efficiently collect and process organics.

While anaerobic digestion is a great solution for inedible wasted food, the county is also advancing even better solutions — preventing food waste and rescuing edible food for people in need.

Ways the county supports residents, businesses and organization in preventing food waste:

• Provides funding to Second Harvest Heartland’s new Minnesota Central Kitchen program which employs restaurant staff who would otherwise be unemployed as a result of the pandemic to feed those in need
• Educates residents on the importance of food waste prevention through our Zero Waste Challenge and Community Recycling Ambassador (formerly Master Recycler/Composter) programs
• Participates in the City of Minneapolis’ Food Council, which supports a local food system with a focus on sustainability and is developing the Minneapolis Food Action Plan, which includes a segment on waste prevention and disposal
• Provides funding to food rescue organizations to purchase refrigerators and freezers to expand their capacity to rescue and redistribute food
• Supports food waste prevention projects at schools, multifamily properties, and county facilities
• Connects Community Recycling Ambassador volunteers to food rescue opportunities

2016

• Conducted board briefing with recommendations on how to increase recycling, which included exploring AD.

2017

• Updated the Solid Waste Management Master Plan – key engagement findings included the need for county leadership to develop organics infrastructure.

2018

• Revised the Recycling Ordinance – required businesses that generate large quantities of food waste implement food recycling and cities offer curbside organics recycling service.
• Released Request for Qualifications (RFQ) for AD

2019

• Board briefing on RFQ response

2021

May 4

Climate action plan adopted – AD included as an element of the foundational strategy to divert organics from trash

June 1

• Board action to add AD facility to the county’s 2021 capital budget and approve bonding request of $21M for State of Minnesota 2022 bonding bill.

June 7

• Request for Proposal (RFP) release

September 21

• House bonding tour

September/October

• Conversations with city and community groups
• Going green event in Brooklyn Park

November 17

• Governor’s Office and Department of Management and Budget bonding tour

December 9

• Presentation to Brooklyn Park Community Long-Range Improvement Commission

December 29

• Proposals due

2022

January 19

• Senate bonding tour

April

• Bonding presentations to legislators

November 1

• Board action to contract with Sacyr for design, value engineering, and cost estimation

To come

• Expand community engagement efforts with multiple stakeholders, including the cities of Brooklyn Park, Maple Grove, and surrounding communities.

David McNary

Assistant Director – Solid Waste Division
david.mcnary@hennepin.us
612-348-5906

Ben Knudson

Waste Reduction and Recycling Supervisor
ben.knudson@hennepin.us
612-596-1176

John Jaimez

Project Manager
john.jaimez@hennepin.us
612-348-5893