MPCA Reviews Potential Environmental Impacts from Proposed Dem-Con HZI Bioenergy, LLC Anaerobic Digester Project in Scott County Public Comment DEADLINE August 15, 2024

August 01, 2024

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(Minnesota Pollution Control Agency) The Minnesota Pollution Control Agency (MPCA) today (July 16, 2024) released an environmental assessment worksheet (EAW) for a new facility proposed by Dem-Con that will process organic materials through anaerobic digesters at its environmental campus in Shakopee, Minnesota. The proposed facility includes two anaerobic digesters that will process up to 75,419 tons per year of organic materials including yard waste, food scraps, and other organics into natural gas and biochar, creating a sustainable alternative to landfilling these organics. The public is invited to comment on the EAW beginning today.

In addition to the digesters, the facility plans to construct an enclosed flare, separate buildings for operations and offices, a digester storage bunker, liquid digestate dispatch/biogas holder, biochar storage area, truck scale, and stormwater management system that includes a pond and infiltration basin.

The EAW is coupled with an air permit to thoroughly assess the potential for significant environmental effects and implement measures to protect the environment and nearby residents. The MPCA will release a draft air permit for the facility at a later date.

Environmental assessment worksheet

The EAW reviewed potential impacts on air, soils, groundwater, surface water, and other potential environmental impacts. Some key takeaways include:

The project will produce an estimated 8,600 tons per year of biochar, a form of charcoal that can be used to improve soil health, lower greenhouse gas emissions, and improve soil moisture. The biochar will be sold to a third party for use as a soil amendment or remediation purposes.
The project will use 3.5 million gallons of groundwater annually with the potential for using 8.8 million gallons.
Per- and polyfluoroalkyl substances (PFAS) may be present in materials received by the facility. The amount of PFAS present in the facility’s produced output waste streams depends on the amount of PFAS in the organic materials received. The processes at the facility do not add PFAS to the end products.
The project will produce renewable natural gas that will be compressed and sent to a pipeline (to be constructed) at the proposed gas interface station. This pipeline will be reviewed in an EAW at a later date.

Air emissions permit

Most air emissions will come from producing biochar. The air permit authorizes construction and operation of the facility and requires Dem-Con to install and maintain several controls to reduce air emissions including the following controls on the biochar process:

Activated carbon injection (for mercury and dioxins/furans).
A fabric filter baghouse (for particulate matter and heavy metals).
A liquid scrubber (for acid gases, particulate matter, heavy metals, and dioxins/furans).

The proposed facility will be located south of the existing Dem-Con landfill in Shakopee and will accept materials from Ramsey and Washington counties and other third-party sources.

There are existing permits tied to a landfill expansion for stormwater management (February 2023) and onsite mining (July 2020). Dem-Con would begin construction on the facility after mining operations are completed. Dem-Con expects mining activity to finish in the fall of 2024 with construction of the project to follow reclamation activity (e.g., grading within the site to drain and topsoil or surfacing application). The facility should be completed in 2026 or 2027. The useful life of the facility is estimated at 30 years.

Community meeting to discuss project

The public is encouraged to comment on the EAW and air permit. The EAW is open for public comment for 30 days, starting Tuesday, July 16, 2024. The air permit will also be open for 30 days, scheduled to begin later this month.

The MPCA will host a public meeting for community members on Monday, Aug. 5, 2024, from 6 to 8 p.m. in Jackson Town Hall (1091 130th St. W in Shakopee) to discuss the project in full detail. There will be an open house and brief presentation on the draft air permit and EAW.

The MPCA invites residents, area businesses, and other interested parties to provide valuable feedback during this public comment period. The agency encourages individuals to share their concerns, suggestions, and perspectives regarding the proposed anaerobic digestion project and its potential impacts. All comments received will be thoroughly reviewed and considered as part of the decision-making process.

The public can review the draft EAW and submit public comments by visiting www.pca.state.mn.us/public-comments or by mail to:

Minnesota Pollution Control Agency
c/o Katrina Hapka
520 Lafayette Rd.
St. Paul, MN 55155

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