Valorization of spent mushroom substrate for low-carbon biofuel production: Recent advances and developments

Due to the nutritional values and functional bioactivities of mushrooms, the global market value of the edible mushroom industry has been growing steadily. However, the production of 1 kg of fresh mushroom generates about 5 kg of wet byproducts (known as spent mushroom substrate; SMS). This necessitates proper waste management to mitigate potential environmental threats. Embracing the "waste-to-fuel" concept, SMS as lignocellulosic waste can serve as cheap and abundant feedstock for the production of a variety of biofuels, including biogas, biohydrogen, bioethanol, bio-oil, and solid-biofuels. Mushroom cultivation serves as efficient biological pretreatment for biofuel production, promoting biofuel yield and improving the overall economy. Therefore, integrated mushroom cultivation and biofuel production can simultaneously satisfy the rapidly rising food and energy demand. The article systematically reviewed the recycling and re-utilization of SMS in sustainable biofuel production, discussing the possible challenges and proposing future directions for the green development of the mushroom industry.