Calgary’s zero waste metabolism

Photo credit: City of Calgary

When one thinks of Calgary, the first thing that comes to mind has to be the world-renowned Calgary Stampede, never more so than this summer when it celebrates its centennial. A lesser-known fact about the city, but one that should give Calgarians as much pride as the annual rodeo, is the ‘zero waste’ metabolism exhibited by the city’s wastewater management scheme.

Urban resource consumption and waste disposal is widely seen as the root cause of many of the world’s environmental problems, such as climate change. Because much damage has already been done to the world’s ecosystems, and solutions need to be found to reverse it, we need to start thinking of regenerative rather than just sustainable urban development. Regenerative cities positively enhance the ecosystem services they receive. They strive to become a closed system in which outputs become inputs in a circular process. An important aspect of regenerative urbanism is a circular waste management that uses organic waste as a resource in a closed nutrient cycle.

The City of Calgary, with over one million residents, recycles and reuses all its wastewater. The process through which this is done not only reduces the amount of heavy metals and toxic material entering the ecosystem as waste and pollution, it creates organic fertiliser for nearby farms, returns treated water back to the Bow River, and produces biogas with which to fuel the treatment plants.

Biosolids thicken in the Shepard Lagoon. Photo credit: City of Calgary

Naturally-occurring bacteria break down complex organic materials into simple and stable substances, such as water, methane and carbon dioxide. The by-product of this treatment is biosolids, a nutrient-rich organic fertiliser and soil conditioner. This liquid fertiliser is transported to tankers on farms and then applied to the farmland in the form of a subsurface injection which reaches the roots of plants.

The city provides biosolids free of charge to Calgary farmlands through the ‘Calgro’ programme, initiated in 1983, which enriches crops such as alfalfa, canola, oats, wheat, and barley. Using biosolids this way recycles valuable nutrients back into the environment and supports peri-urban areas as food-growing land.

The programme operates within the framework provided on both the provincial level by Alberta Environment’s Guidelines for the Application of Municipal Wastewater Sludges to Agricultural Lands, released in 1982 and updated in 2001, as well as municipal level by Calgary’s Environmental Protection and Enhancement Act Approval for Operation of a Wastewater System. At the federal level, the Canadian Council of Ministers of the Environment has established a Biosolids Task Group to develop a Canada-wide approach for the management of wastewater biosolids.

Every year, approximately 20 million kiliograms of biosolids are produced and applied to 2000 hectares of farmland, most of which lies within 35 kilometres of the city.

280 kilometres north of Calgary, the City of Edmonton produces a comparable amount of biosolids through the city’s compost facility which is also applied to agricultural land. Other municipalities throughout Alberta operate similar programmes under the provincial guidelines.

Studies show that transforming biosolids into fertiliser is not only environmentally preferable to landfilling or incineration, it is also more cost effective than other alternatives.

Furthermore, over 172 billion litres of treated water is released into the Bow River. All the biogas emitted from the biogas at the treatment plant is captured and then used to power the processing plants, which ensures an efficient use of resources.

Turning waste into a resource is a key aspect of regenerative cities. When it comes to innovative and regenerative management of wastewater, the city of Calgary rides with the best of them.


Monday, May 7th, 2012