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.