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Ryerson Urban Water
Biosolids applied to agricultural land
Courtesy of Western Virginia Water Authority

Do you ever think about what happens to your poo after it is flushed down the toilet? Where should it go and how well is it treated? These are the questions the municipalities and scientists across the country are asking themselves every day. Canadians produce almost 6 billion kilograms of excrement a year and increasing populations means that there is a rapidly growing amount of human waste that municipalities have to manage.

Biosolids are treated, nutrient-rich, organic residual arising from municipal wastewater treatment and in many provinces across Canada, including Ontario, there are several ways in which municipalities are disposing of biosolids. One management practice, used by more than 80 per cent of Canadian municipalities, is the application of biosolids on agricultural lands as an organic fertilizer, a legal and heavily regulated process by the Ontario Ministry of Environment and Climate Change and the Ontario Ministry of Agriculture, Food and Rural Affairs. This particular application has raised concerns among some scientists. 

Dr. Lynda McCarthy

On March 1, 2016, four scientists called for a moratorium on the agricultural application of biosolids citing the dangers of lingering toxins in biosolids after land application. An Open Letter, written by Drs. Sierra Rayne, John Werring, Richard Honour, Steven R. Vincent, cited concerns that there is insufficient scientific evidence that toxins remaining in biosolids after the treatment process will not pose a threat to human and environmental health once applied to agricultural lands. Instead, they suggest that biosolids should be disposed of in landfills until a more responsible alternative can be offered.

This, according to Dr. Lynda McCarthy, Professor in the Department of Chemistry and Biology at Ryerson University, is not a responsible nor sustainable solution to Canada’s growing biosolids dilemma. Dr. McCarthy, an expert in biosolids research, has been leading a scientific team to investigate the existence of toxins in biosolids and their effects on living organisms through a program sponsored by the Canadian Council of Ministers of the Environment. On August 12, 2016, Dr. McCarthy and fellow scientists Drs. Paul Sibley, Chris Metcalf, and J.E. Loyo released a rebuttal to the Open Letter stating that biosolids are treated through sophisticated, engineered processes to meet strict government regulations that assure health and environmental safety before they can be applied to agricultural lands. They cite the disposal of biosolids through land application as a sustainable, cost-effective solution that adds nutrients to the soil, benefiting crop production and reducing the need for chemical fertilizers.

Biosolids for land application
Courtesy of Aaron Harris, Toronto Star

What is agreed on, is the growing pressure that municipalities face about biosolids management, from increasing volume and costs for landfill disposal, to public distrust of land application methods. Dr. McCarthy cites that public discourse and education is a critical component of the discussion. 

To support public discourse and education, Dr. McCarthy has been an invited speaker at several events in the US and in Canada in the last year. Dr. McCarthy has spoken about her own biosolids research, in addition to, her extensive knowledge of the scientific literature to date. Most recently, Dr. McCarthy was seen at the MetroVancouver offices during two interactive information sessions. Invited participants included representatives of the 21 municipalities that comprise MetroVancouver. The sessions were well attended, live streamed, and highly dynamic. One participant was quoted as saying, “Dr. McCarthy's talks were fantastic, folks were hanging on every word. In addition to being highly informative, Dr. McCarthy’s talks were engaging and entertaining.”

Stay tuned for more updates on biosolids.



Risks Associated with Application of Municipal Biosolids to Agricultural Lands in a Canadian Context ~Canadian Water Network, March 2015

Scientists’ open letter on the dangers of biosolids ~Hamilton Spectator, March 1, 2016

Canadian Researchers Responds to Biosolids Hysteria ~Water Canada, August 12, 2016

Scientists are dueling over whether waste from human excrement should be disposed of on farm land, a common practice in parts of Southwestern Ontario ~The London Free Press, Simcoe Reformer, Tillsonburg NewsIngersoll Times, Delhi News Record, Paris Star Online, Norwich Gazette, Brantford Expositor, Chatham Daily News, St. Thomas Times Journal, Stratford Beacon HeraldThe Observer, Woodstock Sentinel Review, August 28, 2016