Effects of spent mushroom substrate biochar on growth of oyster mushroom (Pleurotus ostreatus)

China produces the largest amount of spent mushroom substrate (SMS) in mushroom production industry. The SMS are the residual compost waste that can lead to environmental pollution. Recycling the SMS as fertilizer is a growing opportunity for agriculture, but its efficiency is relatively low. In this study, we introduced a novel application strategy in mushroom production industry to turn the conventional SMS into a renewable biochar SMS. A cultivation experiment with oyster mushroom (Pleurotus ostreatus) was conducted to evaluate the benefits of renewable SMS in producing edible mushrooms. The results showed that the renewable SMS had greater mushroom yields (20%-25%) and faster fruiting time (4-6 days) than conventional SMS. Biochar increased mushroom yields by retaining substrate moisture and reducing nutrient loss. Further metabolomic and contaminant analyses showed that the renewable SMS could guarantee the food safety of oyster mushrooms. Economic analyses show that renewable SMS has a greater output-to-input ratio than conventional SMS. More importantly, the basic properties of renewable SMS and their effect on mushroom growth remained even after repeated uses. Our study demonstrates that the sustainable recycling of SMS can be achieved through the use of biocharred substrate, which exhibits great application potential in edible mushroom production and environmental security. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).