Biosolids: The Underutilized Resource

By: Claire Williams,
University of Saskatchewan AgBio Student

As a student, I am by no means an agriculture expert. Proof of this comes from a few weeks ago when I became confused by a concept I probably should have heard of before. Yet, until sitting down to write this, I had no clue what the concept of ‘biosolids’ really implied, let alone what it was.

It turns out biosolids are a heavily regulated form of fertilizer, in which the solid by-products of treated wastewater and sewage can be applied to land. Granting there are concerns over the use of human waste on agricultural land, I found that biosolids are an excellent source of essential nutrients, beneficial for crop growth. Upwards of 33% of Canada’s sewage has been used in the process for the last half-century.

Biosolids are divided into Classes A and B, which dictate its uses. Class A is unrestricted in its application as it is virtually free of pathogens (i.e. undetectable). Biosolids designated as Class B, on the other hand, are more strictly managed due to the presence of pathogens. As a result, all biosolids are inspected for quality, not only to categorize the material into the appropriate class, but also to ensure safety for the land.

Regulations

Seeing as biosolids are derived from human waste products, their usage as fertilizer is heavily controlled in Canada by the Fertilizer Program Mandate under the Fertilizer Act. The main goals involve environmental and human, as well as proper labelling and market access. The mandate also creates restrictions as to which farms can use biosolids on their land, taking into account physical attributes such as nearby water source, natural slope, and the potential of run-off.

As mandated under a federal act, biosolids must adhere to the criteria laid out by the Fertilizer Act. The issue is that each province has their own allowance and utilization of biosolids, and municipalities can further restrict application, making each location unique to public perception and local legislation. While federal government makes recommendations based on available technology, treatment type, and disposal, resulting in guidance outlines, use is ultimately left open for local legislation to decide. For example, biosolids are prohibited from land use in Newfoundland and Labrador, whereas British Columbia implements both restrictions on production (via the Organic Matter Recycling Regulation) and a three-step Land Application Plan for Class B biosolids. Despite this allowance, Victoria has chosen to ban biosolid land use due to public pushback.

Effects of Biosolid Land Use

Are the public’s concerns founded on anything? Contamination and safety come to mind when considering agricultural innovations that directly affect food supply, such as land application of fertilizers. In the case of biosolids, existing pathogens such as E. coli¸ Listeria, hepatitis A, and parasites, pose serious health risks for humans when high levels are detected, leading to further concerns about the safety of biosolid use. For this reason, the risk assessment by the Canadian Food Inspection Agency is more rigorous than the process for other fertilizers. With decades worth of research, biosolids are proven to improve soil, crop, and air quality, due to reducing both the bioavailability of toxic substances and methane emissions in landfills. Through the land application, the efficiency of crop growth is improved, reducing the requirement of supplemental fertilizers. The economic impact for farmers goes further, allowing farmers to spend money on a more efficient fertilizer source (Table 1).

Table 1: Summary of average land application costs for a selection of fertilizers.

The Water Environment Association of Ontario estimates that each tonne of dried biosolids has a value of nearly $250/hectare due to present N and P. Canada produces around 660,000 tonnes of dried biosolids, a value of over $13 million that could contribute to Canada’s agriculture. This could reduce both the costs of food production ($167/tonne for biosolids vs. average $443/tonne for fertilizers based on the combination of fertilizer costs and land application costs) and the carbon footprint of the industry (approximately 300 mg CO₂ for upgraded biosolid composting vs. 1 kg CO₂/50kg fertilizer). The use of biosolids provides an opportunity to improve the efficiency and cost of crop production. I believe increasing biosolid use is an important contribution to improving agriculture and the environment, and municipalities should be encouraged to increase the use of this resource.