This guidance outlines the information needed in an odour management plan (OMP). An OMP is a plan to:

  • reduce the risk of potential odour emissions
  • address neighbour concerns from on-farm anaerobic digestion (AD) facilities

This document provides information for on-farm AD facilities who require an OMP through O. Reg. 267/03 made under the Nutrient Management Act, 2002, (NMA) and those on-farm AD facilities who wish to voluntarily develop an OMP.

Legal note

O. Reg. 267/03 (the “Regulation”) made under the Nutrient Management Act, 2002, (NMA) requires specified owners and controllers of regulated mixed anaerobic digestion facilities (RMADF) to ensure that an odour management plan is prepared with respect to the RMADF by a professional engineer. It further requires a professional engineer to prepare an odour management plan, to do so in accordance with the requirements of the Regulation and have regard to the most recent version of the documents known as “Best Management Practices for Industrial Sources of Odour” and “Odour Guidance for On-farm Anaerobic Digestion”. This is the Odour Guidance for On-Farm Anaerobic Digestion. You must ensure you have the most recent version of this document before starting work on an Odour Management Plan (OMP).

For on-farm AD facilities voluntarily developing an OMP, it is recommended that they work with a professional engineer or odour control specialist.

In the event of a conflict between this Guide and the Regulation or any other piece of applicable legislation, the legislation prevails.


The production of biogas at on-farm anaerobic digestion (AD) facilities is expanding in Ontario. On-farm AD facilities continue to grow in number and size, giving farmers more ability to increase revenue and participate in renewable energy markets. However, AD facilities can be a source of odour emissions.

Excessive odour can impact neighbouring properties and lead to complaints from nearby residents and businesses. Throughout the anaerobic digestion and biogas management processes there may be opportunities to reduce or eliminate odour production and impacts to neighbours.

An OMP integrates odour management activities into the daily routine of on-farm AD facility operations. The OMP identifies the main sources of odour from on-farm AD facilities and highlights opportunities to reduce odour production and emissions.

Description of the on-farm anaerobic digestion facility

Once the description of the facility has been set out in accordance with the regulation, a best practice is to provide a process flow for the on-farm AD facility that shows all the components of the facility, including material reception, treatment vessels, biogas handling equipment, odour control systems and anaerobic digestion output management. Use this process flow to identify potential sources of odour emissions.

Map or diagram of anaerobic digestion facility and other potential odour emission sources on the farm

When identifying potential sources of odour emissions from the on-farm AD facility, consider including the following items on the map or diagram:

  • anaerobic digestion materials reception system and related unloading areas
  • anaerobic digestion materials storage and transfer systems
  • anaerobic digestion pre-treatment systems
  • anaerobic digestion vessels
  • odour control systems, including negative air pressure systems and gas management equipment
  • flare and pressure relief valves
  • likely sources of fugitive emissions from buildings
  • general ventilation exhausts
  • storage, processing, loading and transport of anaerobic digestion output
  • land application of anaerobic digestion output

When identifying other odour sources on the farm unit, consider including on the map or diagram:

  • livestock buildings
  • manure storages
  • feed storages

Identification and description of potential odour emission sources from on-farm anaerobic digestion facility

When identifying the list of potential odour emission sources at the on-farm AD facility, consider both normal operating conditions and unusual circumstances that may cause higher than normal odour emissions (such as clean-out or upset conditions, failure of odour control systems, spills, etc.).

When describing the potential causes of changes to odour emissions, it is a best practice to consider conditions such as:

  • delivery of unusually odorous material
  • surplus material stored on site
  • upset digester conditions
  • equipment failure (for example, odour control technology, negative air pressure system, etc.)
  • adverse weather conditions (for example, freezing rain affecting equipment operation; hot weather causing increased feedstock offensiveness)
  • power outage
  • spills or over-filling of tanks
  • emission from pressure release valves
  • damaged or leaky roof, membranes, or corroded tanks
  • vent line blocked with condensate
  • storage tank lid or building doors or windows that are left open
  • leaks from material transfer systems

To prioritize odour reduction efforts, it is helpful to rank the sources of odour emissions in terms of their potential to cause concerns for neighbours. Rank the source of odour emissions by expected strength of the odour and frequency of occurrence.

Odour control measures

Odour control measures can range from good housekeeping practices to complex odour control technologies.

Apply good housekeeping practices to both indoor and outdoor areas at an on-farm AD facility including properly cleaning on-site material spills and regularly cleaning indoor and outdoor areas to avoid accumulation of older AD materials. For certain sources of odour emissions, it may be necessary to use more complex odour control technologies, such as an enclosed building maintained under negative air pressure.

It is a best practice to identify any additional measures that could be implemented to control each odour emission. This list provides the operator of the AD facility with implementable solutions if sources of odour emission concerns arise once the on-farm AD facility begins operations.

Inspection, monitoring and maintenance procedures

In many cases, routine site inspections allow for site personnel to identify sources of odour emissions and initiate responsive actions to prevent the odour emissions from having off-site impacts. It is a best practice to prepare a facility inspection checklist and maintain records of the inspections.

Maintaining odour control systems is critical to prevent equipment malfunctions and maintain optimal odour control conditions. It is a best practice for the OMP to include an inventory of odour control equipment and standard operating procedures (SOPs) for equipment inspections or maintenance activities. The operator of the on-farm AD facility should maintain records of maintenance activities.

Odour contingency plan

The purpose of an odour contingency plan is to identify procedures that allow for a rapid response to unexpected odour emissions that avoid or limit potential odour impacts on neighbours.

It is a best practice for the odour contingency plan to describe or include:

  • a record of operational or maintenance problems that could lead to sources of odour emissions
  • how staff will investigate new causes of odour emissions
  • a requirement for short-term actions to immediately reduce the odour impact, if possible
  • a requirement for long-term actions, if needed, to reduce odours to an acceptable level

Training program

It is a best practice for a training program to include:

  • orientation for new and existing employees,
  • Standard Operating Procedures (SOP) for activities that could be a source of odour emissions
  • SOPs for maintaining and monitoring equipment, and requirements in the complaint response plan process
  • outline of Odour Contingency Plan
  • outline of Complaint Response Plan
  • expectation that the operator of the on-farm AD facility should take all reasonable efforts to reduce odour impacts on neighbours.
  • record keeping, including who has been trained and training topics

It is a best practice to provide refresh training to all employees on an annual basis. Refresh training should include any changes to odour control equipment, SOPs for inspection and maintenance, odour contingency plans or odour response processes.

Complaint response plan

It is a best practice for the complaint response plan to include an orderly process for documenting complaints, such as using an odour complaint form. A sample complaint response form is found in the Best Management Practices for Industrial Sources of Odour.

It may be beneficial for the operator of an on-farm AD facility to establish an open dialogue with the local community or a “Good Neighbour Policy”. This is achieved through identifying ways for the community to contact the operator of the on-farm AD facility and/or hosting an open house. Community awareness of the site operations can assist in their understanding of the farm operation, the sources of odorous emissions and the impacts on neighbours. There are successful programs where on-farm AD facility operators have encouraged local residents to log odours and report back to the facility to help with odour control efforts.

Significant odour emission

The main goal of an OMP is to avoid significant odour emissions and their impact on neighbours and other odour receptors. The occurrence of a significant odour emission is assessed on a case by case basis by an Agricultural Environmental Officer (AgEO). An AgEO could consider the following factors when assessing if an odour is a significant emission:

  • strength, intensity and offensiveness of the odour emissions
  • number of odour receptors affected
  • size of geographic area affected
  • frequency and duration of the odour emissions


This is a list of resources that cover best management practices for managing odours from farm-related and industry activities: