Composting and Pyrolysis Strategies to Manage Flammulina velutipes Residue and Base Waste Based on the Biodegradability and Carbon Sequestration Potential

Spent mushroom substrate waste, including Flammulina velutipes base and residue waste are separately produced after harvesting fruiting bodies. Composting was performed for both two wastes. The total carbon (C) content gradually decreased during both composting processes. More C content had degraded in the Fv -residue treatment (12.4%) than in the Fv -base treatment (6.5%). Dissolved organic carbon (DOC) in residue compost decreased by 79.4% compared with 45.3% by base composting. SUV 254 /DOC ratios were increased by 123.5% and 80.0% in residue and base composting. The N + P 2 O 5 + K 2 O contents were in the range of 10.7–11.0% for Fv -base and Fv -residue treatments. Pyrolysis treatments were conducted at 300 and 500 °C, respectively. The yield (29.4–45.5 wt%), the degree of aromatization and MRT (273–1330 year) was changed with respect to pyrolysis temperature and feedstock. Higher TC (66.2–74.8 wt%) level was identified in base biochar samples. The base biochar at 300–500 °C generated a higher MRT (273–1283 year), lower DOC/TC (0.1–0.2) and DN/TN (0.3) ratios. Thus, composting was more appropriate for residue waste, whereas pyrolysis was optimal for disposing of base waste. The pyrolysis of base biochar samples at 300 °C is recommended to provide better carbon stability. Graphical Abstract