Low-Temperature Anaerobic Digestion of Agricultural Organic Wastes: Performance Evaluation, Influencing Factors, and Nutrient Recovery for a Circular Economy

Intensification of agricultural activities leads to a greater waste generation. Efficiently dealing with organic waste can benefit the environment and be lucrative for all. Organic matter left on land emits greenhouse gases that accelerate the global warming. These emissions can be captured and converted to biogas using anaerobic digestion (AD) biotechnology. Moving towards a circular economy, different techniques can be combined to improve sustainability. This research work investigates the potential of AD to treat different kinds of agricultural wastes at a low temperature, using adapted inoculum and different modes of operation. Starting from inoculum preparation, this thesis covers the details about the AD of mixed agri-wastes like manure and crop residues, biogas production, nutrient recovery and circular economy. A thorough review of the integration of a nutrient recovery option, microalgae cultivation, with AD is conducted. A corresponding outlook for Canada considering regional weather and agricultural conditions is provided. A preliminary study is also carried out on microalgae cultivation using a digestate created post-AD treatment