When organic materials like manure or agri-food wastes break down in the absence of oxygen, they release biogas containing methane, a potent greenhouse gas that contributes to climate change. An anaerobic digestion system, or biodigester, can be used to efficiently convert organic matter into biogas that can then be used to generate electricity, heat, or renewable fuel.
Anaerobic digesters are commercially available systems that not only capture methane but also produce nutrient-rich byproducts that can improve soil health and support sustainable fertilization. Using anaerobic digesters can offer several different opportunities for a farm, including:
- renewable energy production
- digestate production and soil health
- environmental benefits
- odour reduction
Photo of an anaerobic digester at Agriculture and Agri-Food Canada’s Sherbrooke Research and Development Centre.
Renewable energy production
The captured methane from anaerobic digestion can be used as biogas to generate on-farm electricity and heat or can be further upgraded to renewable natural gas (RNG). RNG can be compressed and used as vehicle fuel or used on a day-to-day basis to power industry or heat homes.
Digestate production and soil health
Anaerobic digesters also produce a circular byproduct called digestate. Digestate is the nutrient-rich byproduct left over after organic material is broken-down during anaerobic digestion. This byproduct is made of organic matter and contains nutrients including nitrogen (N), phosphorus (P), and potassium (K). It can be used as fertilizer, soil amendment, animal bedding, or be turned into other products such as seed planters.
Application of digestate presents benefits for soil and animal health and may also reduce weed seeds compared to applying raw manure. When used as fertilizer, soil amendment, or animal bedding, it can reduce the risk of disease to people, animals, and crops. Compared to using raw manure, treating manure through anaerobic digestion greatly reduces pathogens including bacteria and viruses.
Environmental benefits
The use of anaerobic digesters significantly reduces on-farm methane emissions from liquid manure by capturing released methane and converting it into biogas, which can be further upgraded to RNG. Once converted to RNG, it is interchangeable with conventional natural gas and could offset carbon emissions from fossil fuels. Anaerobic digesters can also be an important tool for nutrient management, especially on farms with an excess of manure, as it reduces nutrient run-off that can cause water quality issues.
Odour control
Digesters can reduce odours up to 90% from livestock waste and other organic waste. This can help strengthen relationships between nearby towns and farms as it reduces concerns over strong odours.
For more information
The Canadian Biogas Association is an industry association dedicated to supporting the diverse needs of the biogas and RNG sector in Canada, and has resources for farmers who are interested in learning more about anaerobic digestion and biogas: Farming Biogas – Farming Biogas Microsite.
For provincial resources and information related to anaerobic digestion and biogas: