DNR public hearing April 9 for anaerobic digester at dairy in southern Dunn County
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By LeAnn R. Ralph
COLFAX — The Wisconsin Department of Natural Resources has scheduled an on-line public hearing for an air pollution control permit to construct a dairy waste anaerobic digester at a large dairy in southern Dunn County.
Brightmark C-Dairy RNG LLC is seeking an air pollution control permit for a facility located on 90th Avenue not far from Rock Falls.
The renewable natural gas facility will be operated in conjunction with Cranberry Creek Dairy.
The DNR approved re-issuing a Wisconsin Pollutant Discharge Elimination System (WPDES) permit for Cranberry Creek Dairy in July of 2017 that would allow the herd size to increase to 5,000 milking and dry cows, 500 heifers and 1,250 calves.
Before the DNR approved the re-issued WPDES permit, Cranberry Creek Dairy had approximately 1,205 milking and dry cows, 540 heifers and 250 calves.
About 150 people attended a public hearing held by the DNR in March of 2017 at the Rock Creek Town Hall pertaining to the nutrient management plan for the proposed expansion at Cranberry Creek Dairy.
Out of the 105 hearing appearance forms, one was in support, and the rest were either in opposition or did not indicate a position.
Recent water sampling by Dunn County Land and Water Conservation of nearly 1,000 water wells in the county shows that higher nitrate contamination is concentrated in southeastern Dunn County.
In the Town of Peru, 8 samples were over 10 mg/L out of 27 samples total.
In the Town of Rock Creek, 10 samples were over 10 mg/L out of 42 samples total.
In the Town of Spring Brook, 10 samples were over 10 mg/L out of 35 samples total.
Water quality standards indicate that infants under six months of age and pregnant women should not consume water that has a nitrate concentration above 10 mg/L, and everyone should avoid long-term consumption of water that contains a nitrate level above 10 mg/L.
Brightmark
Brightmark applied for a $500,000 Energy Innovation Grant from the Public Service Commission of Wisconsin for a $21.5 million project in 2022.
The Brightmark C-Dairy Renewable Natural Gas Project will be located at the milking facility. The production plant is expected to process 39.47 million gallons of manure each year from approximately 5,200 dairy cows, according to the application to the PSC.
Vacuum trucks will be used to remove the manure from the barn floors and then transport the manure to the digester reception pits. From the reception pits, manure will be pumped to the digester, where the slurry will be processed for 25 days.
The processed manure will be sent from the digester to a solid separation building, where the processed manure would be further processed and then recycled for fiber bedding, according to the application.
Methane will be separated from the manure in the digester, and the raw biogas will be diverted to a gas conditioning system and processed into pipeline grade renewable natural gas, the application states.
The Brightmark RNG facility at Cranberry Creek Dairy is expected to produce 121,545 MMBTU per year of renewable natural gas, according to the application.
Water quality
Two community anaerobic manure digester facilities (which means they take manure from multiple farms) were developed in Dane County more than 10 years ago.
The Vienna site in Dane County, which is now part of Brightmark’s Demeter RNG, was the first anaerobic digestion system in Wisconsin that was built for water quality reasons to remove phosphorus from the watershed, according to an article titled “Project Profile: Dane County Digester” published on the United States Environmental Protection Agency’s website.
Phosphorus from the 1,900 square-mile Red Cedar River Watershed is the nutrient that fuels the blue-green cyanobacteria blooms on Tainter Lake and Lake Menomin during the summer.
Clean Fuel Partners sold the digester in Dane County to Brightmark in 2019, and Brightmark completed a multi-million-dollar upgrade system in 2020 to produce renewable natural gas in an amount that replaces 50,000 MMBTU of natural gas produced each year in the conventional way. Prior to Brightmark’s purchase, the biogas was burned to generate electricity, according to the article on the EPA’s website.
The 50,000 MMBTUs of renewable natural gas is enough energy for a compressed natural gas bus to travel more than one million miles, according to the EPA article.
The Dane County anaerobic manure digester has reduced phosphorus runoff in the watershed by 60 percent, according to the article on the EPA website.
Over the past six or seven years, the Colfax school district has been replacing diesel buses with buses that operate on compressed natural gas. The CNG buses run quieter than diesel buses, are more fuel-efficient, and seem to have just as much power as diesel buses, according to school district officials.
At more than 100,000 MMBTU of renewable natural gas that is expected to be produced by Brightmark C-Dairy Renewable Natural Gas, that would amount to about 2.5 million miles for one natural gas bus.
Roberts
Nature Energy, a Denmark-based company, had proposed building a manure-digesting facility in Roberts in St. Croix County in 2022 to produce renewable natural gas from cow manure, turkey litter, food-processing by-products and food waste, according to an article published in the Hudson Star Observer.
Participating farms would have received the digestate as fertilizer for the specific soil profile of the farm, the article states.
At a public hearing in August of 2022 in Roberts, there was standing room only, and concerns included spills, explosions, hazardous chemicals, truck traffic, first responder training, noise, water contamination and nutrient management, according to the article.
The Village of Roberts tabled the application from Nature Energy for a conditional use permit, and in October of 2022, Nature Energy asked that all matters pertaining to the company be removed from the agenda for the Roberts Village Board, the article states.
Nature Energy also had proposed building an anaerobic manure-digesting facility in Minnesota.
Shell Petroleum purchased all of the shares of Nature Energy Biogas in 2023 and had announced the agreement to purchase Nature Energy in November of 2022, according to news releases from Shell Petroleum.
Public hearing
The DNR’s hearing to receive public comments on the air pollution control permit application for the construction of a dairy waste anaerobic digester for Brightmark C-Dairy RNG LLC in southern Dunn County will be held on-line Tuesday, April 9, at 11 a.m.
Participants can join the hearing on-line at www.us02web.zoom.us/i/86702216901. The meeting ID is 867 0021 6901.
Participants also can join the hearing by telephone at 1-312-626-6799. Enter 867 0221 6901 followed by #.
All comments received by the DNR at the hearing and all written comments received by the DNR at the hearing and prior to the close of the 30-day public comment period will be considered prior to making a final decision regarding the air pollution control construction permit and operation permit revision.
