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Three years after the initial consultation, Ontario now has new rules for composting and the use of compost

Composting remains controversial

despite its many benefits, including waste diversion, soil enhancement and water protection. The US EPA notes 

  • Compost enriches soils and prevents erosion
  • Compost helps cleanup (remediate) contaminated soil
  • Compost helps prevent pollution
  • Using compost offers economic benefits

See also the Composting Council of Canada. However, the Ministry of the Environment has struggled to manage odour complaints near composting sites, and issues relating to contaminants in compost, especially when sewage biosolids are used as feedstock. Pulp and paper biosolids have also generated considerable concern in some quarters. The new rules address both issues.

The new rules are found in three parts (1) Ontario Compost Quality Standards (Standards) and (2) Guideline for the Production of Compost in Ontario (Guideline), and (3) supportive amendments to Regulation 347 under the Environmental Protection Act (EPA) and O. Reg. 267/03 under the Nutrient Management Act, 2002 (NMA).

The Standards document includes three new compost standards – AA, A and B:

Category AA


  • Highest quality standards; similar to former Ontario standards but with some modifications.
  • May not contain sewage biosolids, pulp & paper biosolids or septage as feedstock.
  • Continues the use of former zinc and copper standards, which are more stringent than Category A.

Restrictions on Use:

  • Category AA may be used without restrictions or approvals (both on and off farm).

Category A


  • Consistent with the CCME Category A quality guidelines.
  • Category A allows for slightly higher concentration of zinc and copper.
  • May use biosolids as feedstock (maximum 25% of total feedstock), but must meet the metals standards on input feedstock.

Restrictions on Use:
Category A must include the following labelling information:

  • maximum application rates;
  • identification of any biosolids and domestic septage used as feedstock;
  • warning that product should not be used on soils with elevated copper or zinc concentrations.

Category A compost may be used without an Environmental Compliance Approval (ECA) (both on and off farm).

Category B


  • Meet the CCME Category B quality guidelines plus Ontario’s Cadmium and Copper standards; less restrictive metals and foreign matter standards than Category AA and A.
  • May use biosolids, but must meet the same metals standards for feedstock as Category A.

Restrictions on Use:

  • Category B compost would continue to require government approval for use and transportation (i.e., ECA off-farm or an approved NASM Plan on-farm).

Waste or product?

The “retail sale” exception from waste regulation no longer applies to compost. Compost must therefore be handled as “waste” unless it meets specified quality standards, normally Category AA or Category A. Facilities with approvals issued before January 1, 2013 can sell, as a product, compost that meets Category AA requirements for metals, quality of feedstock and pathogens, if its environmental compliance approval sets quality standards for other issues.

Guideline on Composting Facilities

The Guideline on composting facilities includes best practices guidance for composting facilities, including:

  • Land use planning and site selection
  • Site and facility design considerations
  • Operating procedures during each stage of material handling
  • Feedstock management
  • Operational flexibility and optimization
  • Operational controls such as compost recipe development and composting process monitoring
  • Prevention and control of potential adverse effects, such as odour

Key revisions to the Guideline since consultation include more detailed guidance on odour issues, including:

  • Negative air pressure to control fugitive emissions
  • Minimum separation distance from sensitive receptors and buffer zones
  • Controversial feedstocks, such as plastic bags, compostable plastic bags and disposable diapers and sanitary items

Existing compost facilities can expect to be pressed to meet the new Guidelines, to the extent practicable.


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