July 16, 2012 Biosolids

For some people, the mere mention of the word ‘biosolids’ is enough to make them swallow hard and try to quickly change the subject. For others, however, discussion about the responsible treatment and use of biosolids and their potential role in today’s society is extremely important and anything but hard to stomach.

What Are Biosolids? 

In order to have any kind of dialogue about biosolids, it is first necessary to understand what they are. Biosolids refers to the residual, semi-solid, organic material that is primarily derived from municipal and/or commercial wastewater treatment processes.

Once upon a time, this “waste” was predominantly dumped straight into our rivers, lakes, oceans and other natural habitats. Thankfully, this environmentally questionable practice is being eliminated over time in favour of more advanced, responsible and sustainable treatment and disposal methods. However, believe it or not, it does still occur in some areas.

Biosolids Production

In Ontario, it’s estimated that around 300,000 metric tonnes of municipal biosolids are produced every year. Of that amount, most are generated in the southern part of the province, around the Golden Horseshoe. The Golden Horseshoe is an area that stretches from Durham Region, just east of Toronto, all the way to the Niagara Region. It moves along the shore of Lake Ontario in a horseshoe shape, hence the name.

The biosolids that are created at treatment plants in Ontario and all around North America are generally used for a few different applications.

Agricultural Uses

Currently, just over 30% of the biosolids that are produced in Ontario end up being applied to agricultural fields. Biosolids are added to the soil as a fertilizer or as a soil conditioner to help fertilize crops. Since corn requires the most fertilization, biosolids are often applied prior to corn fields.

In some cases, farms that deal in livestock receive a portion of biosolids to use as a supplement to manure, but the vast majority goes to cash crops that don’t have any source of manure to use as fertilizer. Biosolids are beneficial to agriculture because they provide a wide array of nutrients, including nitrogen, phosphorus, zinc and copper. Biosolids also enhance the soil structure and moisture retention which contributes to a reduction in soil erosion.

The use of biosolids in agriculture is often called ‘recycling’ because it allows us to return much-needed nutrients and organic matter back to the soil; nutrients that were originally depleted during the natural, crop growth process. Due to exciting, recent advances in science, partially-treated biosolids that aren’t directly applied to crops are now being further processed into true fertilizer products or other soil amendments.


Unfortunately, good portions of the biosolids that aren’t used in agricultural fields for fertilizer are still sent to landfills. With land filling, large quantities of biosolids can be disposed of quickly and cheaply. However, this is not considered a sustainable practice.

Many people no longer support this because landfill capacity is quickly diminishing and it is viewed as being wasteful of a potentially valuable resource that is both wanted and needed.

Today’s producers of biosolids are becoming more aware of the significant potential for the beneficial use of this potentially valuable material. Mankind is coming to understand that when biosolids are properly treated and responsibly managed, we can further reduce the overall need for land filling while replenishing our soils in a safe, responsible, sustainable manner.