Farms and composting in Wisconsin
In Wisconsin, farmers may compost crop residues, manure and animal carcasses generated on their farm sites. Depending on the material and size of the farming operation, DNR wastewater and/or solid waste rules may apply. In most cases, a DNR composting license is not needed for on-farm composting of farm materials.
For information about large-scale farm animal manure or carcass composting, contact your regional DNR agricultural runoff specialist.
For smaller farms not subject to these confined animal feeding operation rules, composting is regulated by DNR solid waste rules.
Farm crop residue
Farm sites composting farm crop residue or manure from their operations need only meet minimum requirements, including the performance standards s. NR 502.04, Wis. Adm. Code and operating in a nuisance-free and environmentally sound manner.
If off-site source-separated compostable material other than farm crop residue and manure is accepted, the farm must meet the following additional requirements. The farm must:
- meet locational criteria;
- meet minimum operational and design standards;
- measure the temperature of compost piles and how frequently the pile is turned, and
- inspect the stormwater control measures used on-site during storm events.
Farm facilities accepting off-site material must limit the combined volume of off-site material accepted to 10,000 cubic yards unless they obtain a composting license.
For manure composting, a livestock operation that is a confined animal feeding operation must have a Wisconsin Pollution Discharge Elimination System (WPDES) wastewater discharge permit, administered by the DNR Wastewater Program, under s. NR 243.15(8), Wis. Adm. Code. Smaller farms that combine their manure for composting may be treated as a CAFO, if the combined manure is equivalent to the amount that would be generated by a CAFO.
Note that manure from deer or elk may not be used as a raw material in farm compost.
All farms, regardless of size, must manage carcasses in compliance with state law that prohibits carcass placement in any stream, lake or swale, and strictly limits the time a carcass may be left accessible to dogs or wild animals (24 hours in April to November, or 48 hours in December to March). All farms are also subject to the agricultural performance standards and prohibitions in subch. II of ch. NR 151, Wis. Adm. Code. Deer or elk carcasses may not be composted at unlicensed farm compost facilities
While rendering remains the preferred method for handling most routine farm animal mortalities, composting can provide an effective option for disposal and recycling if done properly. See the following publication for a step-by-step description of the process and tips on how to avoid problems such as odors and other nuisance conditions:
Farmers doing on-site carcass composting may accept yard materials and clean chipped wood from off-site without obtaining a DNR license if they take all three of the following actions:
- mix yard materials and/or clean wood chips with farm-generated wastes to increase the carbon to nitrogen ratio and porosity;
- ensure the total waste and compost on-site does not exceed 10,000 cubic yards on-site at any one time, and
- ensure that the site meets the minimum design and operation standards under s. NR 502.12, Wis. Adm. Code .
A farm composting operation is exempt from other state solid waste regulations if it meets the following conditions:
- the operation is composting on-site – that is, materials other than yard waste (described above) are generated by agriculture operations under common ownership or management; materials such as manure and carcasses are not accepted from other farmers;
- operates in a nuisance-free and environmentally sound manner;
- meets the performance standards in rule s. NR 502.04, Wis. Adm. Code; and
- landspreads the compost according to rule s. NR 518.04, Wis. Adm. Code.
If a farm composting operation does not meet these conditions of the exemption, it must follow the requirements of regular composting operations.