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Composting rules and regulations in Wisconsin

A typical windrow compost system
A typical windrow composting system.

Wisconsin’s composting rules include basic operating and location requirements to prevent composting from becoming a nuisance to neighbors and to ensure nutrients are not released to groundwater or nearby lakes and streams. The rules require most compost sites to turn the piles or windrows and to measure their temperature. Anyone managing a compost site, no matter the size, should operate in a nuisance-free and environmentally sound manner.

The Department of Natural Resources requires a facility to obtain a compost license for facilities that compost yard materials or food scraps if they have more than 50 cubic yards of material on-site at any time, with some exceptions for on-farm composting. Use the following links for information on small-scale home composting; requirements for composting on farms; or compost use, quality and marketing.

The most common type of large-scale composting involves placing the compostable materials directly on the ground in orderly rows or piles, called windrows. The material is turned periodically to mix and aerate it. Aeration helps the microorganisms digest the materials and eventually produce finished compost.

Other types of large-scale composting include static windrows that are aerated using perforated tubes or blowers instead of turning and "in-vessel" composting that uses a continuously turning vessel and blower to provide aeration in a building or other facility (used to compost sludge or mixed solid waste in addition to yard waste).

Specific compost rules and regulations

Yard materials

Rules and regulations for composting yard materials

Leaf composting
Leaf composting in windrows.

Facilities may compost between 50 and 20,000 cubic yards of yard materials with reduced regulatory requirements. A prospective site operator must provide site location information to the DNR. New or expanding sites accepting more than 1,000 cubic yards of yard materials must request that the DNR conduct an initial site inspection to review locational criteria. The one-time fee for an initial site inspection is $550. Use DNR Form 4400-209 to request an initial site inspection.

After DNR staff conduct the initial site inspection, the prospective operator should complete a Composting Facility Application (link below). After the application is reviewed by DNR staff, the DNR will send out a compost facility license application.

These sites do not have to submit a formal design and operating plan, but must comply with the minimum design and operation standards described in state rules. This includes turning the piles or windrows and taking temperatures. A facility must renew its license each year, but there is no fee for a composting license. See the links below for more information:

Food scraps

Rules for composting source-separated material

Leaf composting
Food scraps prior to being processed and incorporated into windrows.

Any compostable materials separated from non-compostable materials before trash, recycling and compost collection are called source-separated compostable material. These materials include:

  • food scraps;
  • yard, garden and greenhouse trimmings;
  • farm and non-farm crop residues;
  • aquatic plants;
  • fruit, vegetable and grain processing residues, like those produced in canning or brewing;
  • fish harvesting and processing leftovers;
  • farm and other manure from plant-eating animals, excluding deer and elk manure, and associated animal bedding;
  • clean chipped wood;
  • clean sawdust;
  • non-recyclable compostable paper; and
  • other similar materials approved in writing by the DNR.

Source-separated compostable material does not include domestic wastewater, sewage sludge or septage, high-volume industrial waste, rendering or slaughterhouse wastes, animal carcasses, biosolids (like sewage-based fertilizers), other solid waste or hazardous waste.

Composting sites that manage 5,000 cubic yards or less of source-separated compostable material on-site at one time may operate under reduced regulatory requirements. A prospective site operator must provide site location information to the DNR. New or expanding sites must request that the DNR conduct an initial site inspection to review locational criteria. The one-time fee for an initial site inspection is $550. Use DNR Form 4400-209 to request an initial site inspection.

After DNR staff conduct the initial site inspection the prospective operator should complete a Composting Facility Application (link below). The application must include a description of the site operations, a map of the site showing neighboring properties and a plan for controlling run-on to and run-off from the site. After the application is reviewed by DNR staff, and if a plan of operation approval is issued, the DNR will send out a compost facility license application.

Source-separated compostable materials composting facilities may also compost food-related containers and utensils that meet ASTM International standards for compostability—for example, cups and plates and cutlery.

It may be possible in some cases to combine source-separated compostable materials and yard materials composting operations. Discuss this with your regional DNR composting contact for the county where the compost facility will be located.

Large sites

Larger compost sites for yard materials or food scraps

Composting sites designed for more than 20,000 cubic yards of yard materials or more than 5,000 cubic yards of source-separated compostable material must have both an initial site inspection and a written plan of operation approval from the DNR.

To obtain approval, the prospective owner must prepare and submit to the DNR for review a plan describing how the facility will meet the specified design, operation and monitoring requirements. The DNR has developed a checklist to help develop a plan of operation.

For more details, see Composting Facility Application (Form 4400-282) [PDF]  The application form lists the steps needed to obtain a license and includes a checklist of what needs to be submitted.

If critical engineered features are necessary, the plan must also describe how the owner will ensure the use of proper construction methods, and the owner may be required to submit a construction documentation report.

Other solid waste

Rules and regulations for composting other solid waste

Use of a probe to test compost temperature
The typical probe used to measure windrow temperature.

A facility composting materials other than yard materials and source-separated compostable materials is regulated as a processing facility under s. NR 502.08, Wis. Adm. Code. This does not include some on-site farm composting.

This is true regardless of the composting facility size. For example, a facility composting a mixture including any industrial solid waste, such as paper mill sludge, mixed with yard materials or food scraps, is regulated as either a solid waste processing facility by the DNR's Waste and Materials Management Program or under a wastewater discharge permit by the agency's Watershed Program.

The processing facility rule allows the DNR to write a customized permit based on the type of solid waste to be processed, the proposed processing methods and site-specific conditions. For example, a facility composting slaughterhouse wastes is likely to have very different design and operating needs than one processing paper mill sludge and chipped wood.

Just as for large composting facilities, processing facilities must meet location criteria and have an initial site inspection. A facility must get DNR approval of a plan describing how the facility will be designed, constructed, operated and monitored. The facility will also need a solid waste processing license.

For assistance regarding proposed processing facilities, contact your regional DNR waste management specialist assigned to the county where your facility is located 

Resources

DNR publications

DNR forms

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Other publications and resources

Studies