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 what the size, should operate in a nuisance-free and environmentally sound manner.

The DNR regulates municipal and private compost facilities that compost yard materials or food scraps if they have more than 50 cubic yards of material on-site at any time. For information on small-scale home composting, requirements for composting on farms or compost use, quality and marketing, use the following links.

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

Land requirements

Land requirements

Three men stand in front of a pile of finished compost
Staff inspect a pile of finished compost.

Seven acres is the smallest possible area required for a 20,000-cubic-yard windrow composting facility. There are additional regulations for facilities larger than 20,000 cubic yards. This estimate assumes the finished compost is produced in one year or less and rapidly moved off-site. A much larger area would be needed if the materials were turned only infrequently, or if portions of the property were unsuitable for the composting operation.

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 minimal regulatory requirements. A prospective site operator must provide site location information to the DNR. New or expansion sites accepting more than 1,000 cubic yards of yard materials must request that the DNR conduct an initial site inspection to confirm that the site meets location criteria. The one-time fee for an initial inspection for sites handling up to 20,000 cubic yards of yard materials is $550. Use DNR Form 4400-209 to request an initial site inspection.

After DNR staff conduct the initial site inspection confirming the site meets the location criteria—for example, not located in a floodplain or too close to neighbors—the prospective operator should complete a Composting Facility Application (link below). After the application is reviewed and approved 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 similar minimal requirements that apply to yard material compost facilities of up to 20,000 cubic yards. Yard waste and clean, chipped wood may be added to the food scraps as long as the total amount of material on-site remains under 5,000 cubic yards.

In addition to complying with the minimum design and operation standards, operators of source-separated compostable material sites must submit a proposed plan of operation describing the site operations, providing a map of the site showing neighboring properties and including a plan for controlling run-on to and run-off from the site.

Source-separated compostable materials composting facilities may also compost food-related containers and utensils that meet ASTM International standards for biodegradability—for example, paper cups and plates and degradable cutlery. Facility operators should use caution in accepting these materials, however, and be sure their composting process meets the requirements for items such as biodegradable plastic bags and cutlery. These items do not readily biodegrade except under certain conditions and may cause problems with equipment and compost quality.

It may be possible in some cases to combine source-separated compostable materials and yard materials composting operations. Discuss this with your regional DNR recycling specialist 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
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 household composting and 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 recycling specialist assigned to the county where your facility is located 

Last revised: Thursday June 18 2015