The mycelial waste generated during the production of mycelium-based leather composites presents both opportunities and challenges in maximizing biomass resource efficiency. In this study, we synthesized mesoporous biochar (AGLM-5) with a specific surface area of 3151.9 m2/g through the KOH activation method using Ganoderma lucidum mycelium waste as the precursor material. AGLM-5 exhibited exceptional performance in a three-electrode system test, demonstrating a specific capacitance of 303.5 F/g. In a two-electrode system test, it achieved an energy density of 45.5 Wh/kg at a power density of 450.7 W/kg. The symmetric supercapacitor assembled using AGLM-5 demonstrated outstanding cycling stability over 10,000 cycles, exhibiting a capacitance loss of less than 4 % throughout the entire testing period. Additionally, we employed a hydrothermal method to synthesize composite electrode sheets (δ-MnO2/AGLM-5), which not only supported the layered structure of δ-MnO2 but also significantly improved the cycling stability and electrical conductivity of aqueous zinc ion batteries (AZIB). This study presents an environmentally friendly and sustainable approach for utilizing Ganoderma lucidum mycelial biomass, with particular emphasis on the potential application of mycelial carbon materials in battery energy storage.