Scott County planners recommend approval of Demcon anaerobic digester; Board of Adjustment OKs height variance

Scott County staff and planners recommended approval Monday of a proposal from Demcon HCI Bioenergy LLC to build an anaerobic digester and biochar production facility on a 26‑acre lot in Section 28 of Louisville Township, and the Board of Adjustment granted a related height variance for the site’s air‑quality control building.

The Planning Advisory Commission voted 6‑1 to recommend the preliminary plat and conditional use permit to the County Board after hearing a technical presentation from county staff and a detailed project presentation from Demcon. The county’s Board of Adjustment approved a separate variance to raise the maximum permitted building height from 45 feet to 65 feet to accommodate required air‑quality equipment tied to a Minnesota Pollution Control Agency (MPCA) air permit.

Why it matters: County planners and the applicant say the facility will divert organic waste from landfills, supply renewable natural gas to pipeline utilities and produce biochar as an industrial soil amendment and carbon‑sequestering product. Neighbors raised concerns about wetlands, stormwater, traffic, odors and long‑term changes to the hamlet of Lydia; township officials argued the change would help preserve the town’s tax base as other industrial areas are annexed by nearby cities.

Project overview and regulatory status Demcon proposes an anaerobic digester with associated gas upgrading and a high‑temperature biochar (gasification) stage on a reclaimed portion of an existing quarry site. Greg Wagner, principal planner for Scott County, told the commission the property is zoned I‑2 Heavy Industrial and described the parcel context: “To the west is land that’s part of the National Wildlife Refuge,” and Bridal Rock Quarry sits to the north. Wagner also noted the project team submitted an Environmental Assessment Worksheet (EAW) to the MPCA and received a negative declaration (no Environmental Impact Statement required) and that the MPCA issued an air permit in September 2024.

Demcon’s presentation (Mark Paul, company co‑owner) described the plant’s process and quantities. Paul said the facility would receive about 75,000 tons per year of organic feedstock and produce renewable natural gas and biochar. “We’re receiving 75,000 tons of organic material,” Paul said, and he outlined the proposed feedstock mix: about 30,000 tons of source‑separated organics (curbside food waste), 20,000 tons of organic‑rich screenings, about 15,000 tons of commercial “back‑of‑house” organics (restaurants, grocery waste) and roughly 10,000 tons of yard waste. Paul estimated product output at roughly 200,000 MMBtu of renewable natural gas and about 7,500 tons of biochar per year.

Air quality, stack height and variance County staff said the MPCA air permit and federal/state regulations drove the project’s air‑quality equipment design. Wagner explained the air‑quality control system requires vertically oriented scrubbers and a stack; the applicant asked a variance because the stack and equipment push the structure above the county’s 45‑foot height limit. The applicant proposed a 50‑foot building with a 15‑foot stack (total 65 feet). Wagner noted the facility will be set down below the adjacent roadway grade: finished floor elevation at about 751 versus Highway 169 at about 780, meaning the building will be largely depressed relative to the road.

Mark Paul and air‑permitting staff said the MPCA modeled emissions based on the selected stack height and issued the permit after public review; Paul and project engineer Bill Keegan described the air‑quality control system as multi‑stage (ozone/UV, carbon filtration and other scrubbing) and said there will be continuous monitoring, spare parts and 24/7 staffing to reduce the risk of odor events. Paul noted the project team visited operating facilities in climates similar to Minnesota and that the MPCA air permit is voluminous: “The air permit is 400‑plus pages,” Greg Wagner said.

Traffic, noise, stormwater and site layout Demcon said receiving hours would be 6 a.m.–7 p.m., Monday through Saturday; typical inbound truck loads of consolidated feedstock are expected to be in 20–30 truckloads per day, with an additional 10–30 employee/visitor trips per day. The applicant and staff emphasized that most handling of organic materials will occur inside an enclosed receiving hall to limit odor and dust, and that landscaping (rows of spruce and maples) and the site’s depressed elevation are planned to reduce visual impacts from Highway 169.

County staff and Louisville Township both recommended approval of the plat and conditional use permit, subject to the conditions listed in the staff report. Staff noted prior coordination with the Shakopee Fire Marshal and county building inspections and said natural resources and stormwater comments must be addressed before County Board consideration.

Public comment and township position At both the Board of Adjustment and the Planning Commission hearings, members of the public questioned wetland boundaries, floodplain mapping, traffic, odor and whether the proposal would change the character of nearby hamlets. Louisville Township representatives and Spring Lake Township representatives (for a separate comp‑plan item during the same meeting) attended. The township and Demcon said they held multiple informational open houses in 2024 as part of MPCA review and county outreach.

Votes at a glance - Board of Adjustment (variance): Motion to approve variance to increase maximum building height from 45 feet to 65 feet for the air‑quality control system (agenda item PO‑2020473). Outcome: approved (recorded as unanimous at the meeting; tally recorded as 7 yes, 0 no, 0 abstain). Motion and second were on the record; staff recommended approval. - Planning Advisory Commission (preliminary plat and conditional use permit for Demcon HCI Bioenergy LLC): Motion to recommend approval to County Board, subject to staff conditions. Outcome: recommendation approved 6–1.

What remains The Planning Commission’s approval is a recommendation to the County Board; final land use approvals, zoning actions and any required solid‑waste licensing will be taken by the County Board and other permitting agencies. Demcon said construction could begin later in 2025 if approvals proceed and estimated an 18–24 month construction schedule with operations anticipated in 2027 (applicant’s projection). County staff flagged remaining technical items — stormwater, civil‑plan comments and final building‑plan review — that must be resolved before County Board action.

Reporting details and clarifications - Project site: approximately 26 acres for the digester lot; a second 4‑acre lot has been shown for future landfill/stormwater uses and may be incorporated later. - Stack/building: proposed building 50 feet + 15‑foot stack = 65 feet; county code maximum for Heavy Industrial District is 45 feet (variance requested and granted by Board of Adjustment). - Feedstock and output (applicant estimates): ~75,000 tons/year input; ~200,000 MMBtu/year RNG; ~7,500 tons/year biochar. Sources: Mark Paul, Demcon; Greg Wagner, Scott County staff.

The Planning Advisory Commission record and county staff report note that the MPCA led the environmental review (EAW) and issued an air permit after a public comment period; both the EAW process and the MPCA air‑permit review included prior public meetings in 2024. The County Board will consider the Planning Commission recommendation at a future meeting; the applicant and staff will need to resolve technical stormwater and civil comments before that consideration.

Ending The Demcon project remains subject to additional county approvals and permitting steps. The MPCA air permit is in place and the Board of Adjustment has granted the height variance the project requested to comply with that permit; the Planning Advisory Commission recommended approval of the preliminary plat and conditional use permit to the County Board on a 6‑1 vote. County staff listed remaining civil and stormwater items that must be addressed before final County Board consideration.