Regulation of Composting Operations

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The State Water Resources Control Board and Regional Water Quality Control Boards (Water Boards) are required to protect the quality and beneficial uses of the waters of the state. The California Water Code requires that anyone who discharges waste that could affect waters of the state must submit a report of waste discharge. Current practice is to issue individual waste discharge requirements (WDRs), general WDRs, or waivers of WDRs. A conditional waiver for "green waste-only" composting facilities was in effect from 1994 until 2003, when a change in law required all waivers to be either renewed or replaced with WDRs. The State Water Board developed General Waste Discharge Requirements for Composting Operations (Composting General Order) that address water quality protection at composting facilities. The State Water Board certified the associated Environmental Impact Report (EIR) and adopted the Composting General Order on August 4, 2015.

Current Documents

General Order Frequently Asked Questions (FAQs)

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  • Why are there limitations on additives for Tier 1 and Tier 2 facilities?

    Additives are materials mixed with feedstocks or active compost to create favorable composting conditions. Generally, additives are incorporated at rates to consume or fix/immobilize constituents during active composting. A number of factors were considered during the development of additive limitations for each tier including the character and volume of material and potential threat to water quality, design specifications required for protection of water quality, additive limitations at existing facilities currently operating in the state pursuant to waste discharge requirements issued by the Regional Water Quality Control Boards, general standards of practice, and additive limitations imposed by other states.

  • Are there requirements for agricultural composting in the Composting General Order?

    The Composting General Order, describes composting activities that produce compost for use on site, including agricultural sites, as conditionally exempt in Finding 30. There are four criteria that describe this exemption: (1) the facility receives, processes, and stores less than 25,000 cubic yards of material on site at any given time; (2) feedstocks consist of vegetative agricultural materials, green materials, and/or manure, all of which are generated by agricultural and/or similar activities; (3) the resulting compost product is returned to the same site, or a property owned by the owner of the composting activity and applied at an agronomic rate; and (4) no more than 5,000 cubic yards of compost product is given away or sold annually. To remain exempt, best management practices must be implemented.

  • Are all farms that compost manure required to enroll under the Composting General Order?

    Agricultural facilities choosing to compost materials generated on site may be exempt from the requirements of the Composting General Order if the conditions specified in Finding 30 are satisfied. If the conditions specified for exemption from coverage under the Composting General Order are met, agricultural composting operations may still be required to obtain coverage under other permits such as stormwater permits or agriculture-specific waste discharge requirements.

  • Are all operations that compost manure required to enroll under Tier 2?

    The applicability of the Composting General Order to composting manure depends on the use of manure in the composting process, as well as the overall volume of material on site. If there is less than 25,000 cubic yards of material on site and manure is used as an additive (up to 10% of the total volume), manure is acceptable at Tier 1 facilities. If there is less than 25,000 cubic yards of material on site and manure used as a feedstock, manure is acceptable at Tier 1 facilities if a groundwater protection monitoring plan is implemented. At Tier 2 facilities, manure and other allowable feedstocks are acceptable at volumes greater than 25,000 cubic yards on site at any given time. If manure is composted in a manner that meets the criteria for conditional exemptions in Finding 30 (on-site composting or operations with less than 5,000 cubic yard annual throughput) or meets the exemptions in Finding 31 (operations within a fully enclosed vessel or operations with less than 500 cubic yards at any given time), those activities may be exempt from the requirements of the Composting General Order. Composting operations conducted in a manner other than those defined in the Composting General Order or as exempted may be subject to individual waste discharge requirements issued by the Regional Water Quality Control Boards.

  • Can you compare the conditional exemption in the Composting General Order to the agricultural exclusion in California Code of Regulations, Title 14?

    The conditional exemption in Finding 30(a) of the Composting General Order is similar to the agricultural exclusion in California Code of Regulations, Title 14 (Title 14), Chapter 3.1, Article 2, Section 17855(a)(1); both set limits on feedstock source and the amount of finished compost that may be sold or given away.

    Feedstocks: The agricultural exclusion in Title 14 limits feedstocks to "agricultural material" as defined in Title 14, Chapter 3.1, Article 1, Section 17852(a)(5) which results directly from the conduct of agriculture, animal husbandry, horticulture, aquaculture, silviculture, vermiculture, viticulture and similar activities and includes, but is not limited to, manures, orchard and vineyard prunings, grape pomace, and crop residues. The conditional exemption in the Composting General Order limits feedstocks to vegetative agricultural materials, green materials, and/or manure, all of which are generated by production of farm, ranch, agricultural, horticultural, aquaculture, silvicultural, floricultural, vermicultural, or viticultural products.

    Product use: Both the agricultural composting exclusion in Title 14 and the conditional exemption in the Composting General Order encourage use of the finished product on site. No more than an incidental amount of up to 1,000 cubic yards of compost product may be given away or sold annually under the exclusion in Title 14 and no more than 5,000 cubic yards of compost final product may be given away or sold annually under the conditional exemption in the Composting General Order.

    Agricultural composting operations not eligible for the conditional exemption may be required to comply with the requirements of the Composting General Order. Similarly, agricultural operations not eligible for the agricultural exclusion may be subject to the Agricultural Material Composting Operations requirements of Title 14 (Title 14), Chapter 3.1, Article 2, Section 17856.

Composting Operations Map and List

Click here or on the picture below for a statewide map and list of composting operations enrolled under the Composting General Order (Tier I and Tier II facilities) and operations with individual waste discharge requirements (WDRs). The map is continuously updated as operations enroll.

Compost Facility Location Map

Past Activities and Documents

State of California Resources

Financial Assistance Information

Water Boards

Regional Water Quality Control Boards

Department of Resources Recycling and Recovery

California Department of Food and Agriculture

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