Spent mushroom substrate: A review on present and future of green applications

The cultivation of edible mushrooms plays a significant role in revitalizing numerous rural regions in China. However, this process generates a large amount of spent mushroom substrate (SMS). Traditional methods for handling SMS, such as random stacking and incineration, lead to resource waste and environmental pollution. The content of organic matter in SMS can range from 40% to 60%, and it also contains various beneficial elements such as trace minerals, making it a valuable resource for biomass. This review initially explores the unique characteristics of SMS and then summarizes the main methods of utilizing its resources. Presently, common resource utilization techniques for SMS include using it as a second-generation cultivation substrate, preparing animal feed and soil fertilizer, producing methane, bioethanol, hydrogen, bio-oil, and electrodes of energy storage devices, extracting enzymes and polysaccharides, and creating bioremediation materials for heavy metals and organic pollutants removal. While research has been conducted on these utilization methods, there are still relatively few large-scale industrial applications. This review also highlights existing challenges and potential solutions in the SMS utilization. Upcycling SMS via innovative and practical technologies presents a promising approach to transforming organic waste into economic value.