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Biosolids Management Program

What are biosolids?

Biosolids are a nutrient-rich organic material recovered through our advanced wastewater treatment process. They contain nitrogen, phosphorus (a finite resource), potassium and essential micro-nutrients.

These properties make them a valuable natural nutrient source, soil conditioner for agricultural land and a high-quality component of compost.

Benefits of biosolids

  • Improve the quality of soil for farming, reduce the need for chemical fertilizers and are a high-quality component of compost.

  • Ensure that nutrient cycles continue and that valuable, finite resources (such as phosphorus) are not wasted.

  • Land application of biosolids enhances soil health by improving physical, chemical, and biological properties of the soil, ensuring nutrient cycles continue and increasing crop productivity by the addition of moisture and organic matter to soil.

  • Sequester carbon, reducing the release of carbon dioxide (a greenhouse gas) to the atmosphere.

How The City uses biosolids

The City of Calgary beneficially uses biosolids in three main ways:

Calgro™ land application program

Since 1983, local farmers have been fertilizing their fields with biosolids by participating in our Calgro™ land application program. At its inception, this innovative program was the result of a joint initiative between the Government of Alberta and The City to establish best management practices for land application. Since then, Calgro has grown and maintained positive relationships with the local agricultural community.

From April to late October, Calgro works on farmlands near the Shepard Lagoons in southeast Calgary. Biosolids are transported from the Shepard Lagoons to pre-approved agricultural land, where specialized equipment is used to subsurface inject biosolids 5 to 10 centimetres (2 to 5 inches) below the ground surface into the soil.

Following provincial guidelines, soils that receive biosolids can be used to grow cereal grains, small oilseeds, dried legumes, forage crops, trees, and sod.

If you are interested in participating in our Calgro program, call 311.

Biosolids Demonstration Projects

Since 2013, the two Biosolids Demonstration Projects have used dewatered biosolids to improve the quality of soils considered “marginal” for agriculture and as a nutrient source for a willow tree farm.

The City’s willow farm is the largest willow plantation in North America. Harvested willow whips and woody biomass have many uses but are primarily used as feedstock material at the Calgary Composting Facility and forage material for the Calgary Zoo’s ruminant animals.

These two projects have received prestigious awards between 2018 and 2023 for their innovation in creating a circular economy and promoting greenhouse gas reductions through carbon capture.

Calgary Composting Facility

Since 2017, the Calgary Composting Facility has been composting dewatered biosolids produced at the Bonnybrook Wastewater Treatment Plant into Category A compost that is sold commercially. 

Biosolids safety

Biosolids have been used for land application in Canada and around the world for decades. Biosolids are regulated by the province. In Alberta, our advanced wastewater treatment process and the land application of biosolids are regulated by Alberta Environment and Protected Areas (AEPA). 

The federal government (Canadian Council of Ministers of the Environment (CCME)) has a Canada-wide approach that also supports the beneficial use of biosolids within Canada. The CCME has documented biosolids land application as a means to safely treat and return beneficial products back to the land in a protective way which is important for public and environmental health.

The City applies biosolids in accordance with the strict land application guidelines set by AEPA. To ensure the quality of the biosolids produced and the receiving soils meet all Provincial regulatory requirements, the biosolids are sampled and analyzed at all stages of the advanced wastewater treatment process and an elaborate annual soil sampling program is completed.

Biosolids usage regulations for The City of Calgary


As part of The City's biosolids management program, we are committed to pursuing research into the best ways to manage biosolids and increase program resiliency.

The City has been proactively participating in biosolids research since 2011 to address information gaps and help answer fundamental questions that are relevant to our operations and our customers. This includes partnerships with AEPA, the University of Waterloo, McGill University, Ryerson University and the Canadian Water Network.

Frequently asked questions

How are biosolids produced?

Biosolids are produced through an approximately month-long, multi-step advanced wastewater treatment process.

During this time, wastewater solids are microbially digested, settled and thickened/dewatered resulting in biosolids.

What do biosolids look like?

A portion of produced biosolids is thickened at the Shepard Lagoons and have a similar consistency to ketchup.

Another portion is dewatered at the Bonnybrook Dewatering Facility and is initially almost jelly-like, with a surface texture like wet coffee grounds or moist cookie crumbs

What is the difference between biosolids and sewage sludge?

Sewage sludge is an untreated, semi-solid material not suitable for reuse without treatment.

At The City of Calgary, biosolids are created when sewage sludge undergoes proper treatment to convert complex organic material in the sludge into methane, carbon dioxide and biomass, and to reduce solids.

During this process, disease-causing microorganisms are also considerably reduced, producing a safe, nutrient-rich material suitable for recycling in agricultural lands.

Do biosolids have an odour?

Not all biosolids are the same. The odour from biosolids can vary depending upon the type of treatment employed and the way biosolids are delivered and applied.

For stockpiled and surface applied dewatered biosolids, a faint initial musty, ammonia odour may be noted. Odour generation is strongest during two times: when biosolids are delivered and stockpiled (before the biosolids have formed a dry crust layer), and during applications to the project site. Biosolids that are subsurface injected have little to no odour throughout the application process. 

How does industrial wastewater impact our biosolids?

The City’s Wastewater Bylaw defines substances that are prohibited from release to the sewer and identifies substances with concentration limits (must not exceed) if released into the wastewater system. Prohibited substances include, but are not limited to, any substance that would interfere with the beneficial reuse of biosolids.

The City can request a wastewater report and may require a wastewater agreement, wastewater pre-treatment system and/or control of the composition and/or flow rate of a release from/by a specific industry member. We assess wastewater quality at specific access points throughout the city to monitor bylaw compliance. The chemical and physical properties of the biosolids produced by The City are monitored to ensure that regulatory requirements are met prior to land application or composting.

What if I have more questions about how The City of Calgary uses biosolids?

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