Pyrolysis of Mushroom Cultivation Substrate for Sustainable Biochar Production within a Circular Economy Framework

Mushroom waste substrate is produced in large quantities, up to 5 kg per kg of mushroom. It contains fungal spores, making landfill disposal not allowed, thus it is currently accumulated. This thesis investigates the thermochemical valorization of mushroom cultivation substrate via pyrolysis, with biochar as the main product of interest due to its potential reintegration into mushroom growing cycles and its suitability for carbon sequestration. The experimental activity comprised eight pyrolysis tests in total: a preliminary batch phase with six experiments at 350, 450, and 550 °C using both fresh and spent substrate as feedstocks, and a subsequent continuous stage with two tests at 500 and 600 °C using spent substrate only. Results analysis of the batch setup focused on biochar quantification and characterization in order to identify the most suitable conditions for the following testing stage. In the continuous setup, all product streams were analyzed, considering the contribution of gases and liquids to the energy balance and the perspective of a self-sustained process. Overall, this study demonstrates that mushroom substrate is a valuable feedstock for producing high-quality biochar via pyrolysis, with promising potential for soil amendment and carbon sequestration.