1. A. Feedstock Categories.

   1. 1. Feedstock Category One.

      1. a. Yard trimmings, leaves, and grass clippings;
      2. b. Land-clearing debris;
      3. c. Wood, woodchips, and sawdust, from untreated and unpainted wood that has not been in direct contact with hazardous constituents;
      4. d. Agricultural crop field residuals;
      5. e. Compostable bags commonly used for collecting and transporting yard trimmings, leaves, and grass clippings; and
      6. f. Similar materials as specifically approved in writing by the Department.

      Category One feedstocks have a high Carbon-to-Nitrogen ratio and pose limited risk of contamination from pathogens, trace metals, hazardous constituents, or physical contaminants that are not compostable. These feedstocks also have low moisture content. Grass clippings have a lower Carbon-to-Nitrogen ratio than other Category One feedstocks, but are included in this category because they are commonly collected with leaf and limb debris. This category includes only:

   2. 2. Feedstock Category Two.

      1. a. Non-meat food processing wastes, including marine shells and dairy processing wastes;
      2. b. Produce and non-meat food preparation residuals generated by wholesale or retail sales establishments or food service establishments;
      3. c. Plate scrapings including cooked meats generated by food service establishments;
      4. d. Manufactured compostable products and waste paper products that are otherwise unsuitable for recycling;
      5. e. Animal manures and materials incidental to its collection as defined in this regulation;
      6. f. Residual organics from anaerobic digesters or other waste-to-energy conversion processes utilizing only Category One or Category Two feedstocks; and
      7. g. Industrial wastes/sludges that meet the waste characterization requirements found in R.61-107.19, Part IV, Section A for disposal into a Class II Landfill; and
      8. h. Similar materials as specifically approved in writing by the Department.

      Category Two feedstocks have a lower Carbon-to-Nitrogen ratio than Category One feedstocks, have a high moisture content, and are more likely to contain pathogens, trace metals, or physical contaminants that are not compostable. This category includes only the following source-separated materials:

   3. 3. Feedstock Category Three.

      1. a. Sewage sludge;
      2. b. Industrial sludges, except as specifically identified in Section A.2 of this Appendix;
      3. c. Drinking water treatment sludge;
      4. d. Fats, oils, and greases (FOG);
      5. e. Animal-derived residuals except as specifically identified in Section A.2 of this Appendix;
      6. f. Residual organics from anaerobic digesters or other waste-to-energy conversion processes utilizing Category Three feedstocks;
      7. g. Other industrially produced non-hazardous organic residuals not previously categorized in this Appendix; and
      8. h. Other organic materials not prohibited below, as approved by the Department.

      This category includes feedstocks that have the most risk from trace metals, source variability, physical contaminants, pathogens, and other properties that may be detrimental to plants, soils, or living organisms in high concentrations. These feedstocks require more intensive analysis and monitoring prior to being incorporated into the active composting area and require approval for composting by the Department on a case-by-case basis. This category includes:

   This Appendix defines categories of common organic feedstocks for composting. The feedstock characteristics of Carbon-to-Nitrogen ratio, moisture, pathogen content, source variability, non-compostable contaminants, trace metals, and toxic metals content are considered when assessing appropriate facility design features and quality assurance monitoring necessary to produce beneficial products in an environmentally protective process. The Department will use these characteristics to assign the category and level of risk posed for any feedstock not listed here. Any mixture of feedstocks for composting shall assume the level of risk for the most problematic feedstock in the mixture.

2. B. Prohibited Feedstocks. Composting of materials containing the following items is not allowable under this regulation:

   1. 1. Municipal solid waste, except those activities under which after a two-year period of operation in compliance with a permit issued under authority of R.61-107.10, SWM: Research, Development, and Demonstration Permit Criteria, have been determined by the Department to have adequately achieved their objectives and satisfactorily protected public health, safety, and the environment;
   2. 2. Friable and non-friable asbestos as defined by R.61-86.1, Standards Of Performance For Asbestos Projects;
   3. 3. Biomedical or infectious wastes as defined by R.61-105, Infectious Waste Management;
   4. 4. Hazardous waste as defined by Resource Conservation and Recovery Act (RCRA), Public Law 94-580, and R.61-79, Hazardous Waste Management Regulations, promulgated pursuant to the South Carolina Hazardous Waste Management Act (SCHWMA), as amended, S.C. Code Ann. Sections 44-56-10 et seq.;
   5. 5. Materials for compost or mulch production that contain or are contaminated with Polychlorinated biphenyl (PCB) where concentrations are greater than quantifiable detection limits;
   6. 6. Source, special nuclear, or by-product material as defined by the Atomic Energy Act of 1954, as amended;
   7. 7. Radioactive material managed pursuant to R.61-63, Radiological Materials (Title A); and
   8. 8. Materials resulting from coal combustion, including but not limited to, fly ash, bottom ash, boiler slag, and flue gas desulfurization materials.

HISTORY: Amended by State Register Volume 38, Issue No. 6, Doc. No. 4432, eff June 27, 2014; SCSR 45-5 Doc. No. 5003, eff May 28, 2021; SCSR 49-5 Doc. No. 5328, eff May 23, 2025.