The cultivation of Volvariella volvacea generates a high amount of waste in the form of spent mushroom compost (SMC). Utilizing this by-product for sustainable agriculture, particularly as a plant substrate, can contribute to the sustainable management of the environment. This review highlights the application of SMC in vegetable crop production. SMC undergoes various treatment, especially using a biological process to improve the quality and adaptability of plants. Furthermore, an exemplary model using plant-growth-promoting bacteria for the improvement of SMC quality for okra cultivation is also presented.