The Untapped Value of Poop and Food Waste

A waste bin full of vegetables (CC0 1.0 Public Domain)

An Article by Nettie Wallace and Ushnik Mukherjee

As the world’s population continues to grow, farmers are under increasing pressure to produce more food than ever before. Unfortunately, efforts to increase agricultural outputs has also led to a rise in waste generation – particularly manure and food waste. Current agricultural waste management strategies place a significant burden on the environment. 

Let’s begin with manure, which is typically stored on farms. The storage and handling of livestock manure releases greenhouse gasses such as nitrous oxide and methane, which have 300 and 30 times the global warming potential of carbon dioxide, respectively. Additionally, the high nutrient content of livestock manure can negatively impact water quality. In 2018, it was estimated that 35 million tonnes of nitrogen from livestock manure was transported to water systems worldwide. This excess of nutrients can cause harmful algal blooms and lead to the eutrophication of lakes.

Food waste also significantly impacts the environment. Typically, food waste is transported to landfills, where it decomposes . However, this process releases large amounts of methane – a potent greenhouse gas. Globally, food waste is estimated to contribute 8% of total greenhouse gas emissions. 

Despite their similarities, manure and food waste management are rarely discussed together. By recognizing their connection, we can view them as part of a unified system to develop innovative agricultural waste management solutions.

A potential solution for the joint management of livestock manure and food waste lies in the use of biodigesters. Biodigesters breakdown organic wastes in an oxygen-deficient environment through a process known as anaerobic digestion. During this process, the methane produced as the organic matter breaks down is captured by the digester rather than released into the environment. The captured methane can then be cleaned and converted into electricity, heat, or vehicle fuel, offering a sustainable energy solution. 

Another advantage of using biodigesters for agricultural waste management is the system's circularity. The valuable nutrients in livestock manure and food waste are preserved throughout the anaerobic digestion process. These nutrients are captured in a product known as digestate, which can be used as an organic fertilizer for cropland, providing a natural alternative to costly synthetic fertilizers. 

The sustainable use of biodigesters to manage food and manure waste is one of three priority research areas in the SOLUTIONSCAPES project. The Biogas Team is exploring the full potential of the biodigester system to determine how this industry could expand in Ontario, in a cost effective way, to reduce the greenhouse gas emissions and water quality impacts of current agriculture waste management practices. 

Learn more about some of the trade-offs that the research team is investigating.