Abstract

Mushroom cultivation in Thailand primarily uses rubber tree sawdust as a substrate in plastic bags, resulting in an annual production of approximately 120,000 tons. However, this method generates significant amounts of spent mushroom substrate (SMS), which is often discarded or minimally repurposed as fertilizer, contributing to environmental issues. This study was carried out to evaluate the potential of SMS, derived from oyster mushroom (Pleurotus ostreatus), as an alternative substrate for cultivating inky cap mushroom (Coprinopsis radiata) within a circular economy framework. Five substrate formulas with varying proportions of rubber tree sawdust (SD) and SMS (100:0, 75:25, 50:50, 25:75 and 0:100) were tested using a completely randomized design. The results showed no statistically significant differences in the number of mushrooms, stem length, or biological efficiency across treatments. However, treatments with balanced ratios of SD and SMS (SD 75%:SMS 25% and SD 50%:SMS 50%) produced the highest fresh weight yields during the initial 1–10 days of cultivation, with yields of 72.05 g and 72.16 g, respectively. The SD100%:SMS0% treatment produced the largest cap width at 1.31 cm. The findings underscore SMS's role in reducing production costs, minimizing waste, and supporting sustainable agriculture. Future research should explore SMS utilization under diverse environmental conditions and for other mushroom species to enhance its commercial viability in mushroom production. This study highlights SMS’s contribution to circular economy goals by transforming agricultural waste into a valuable resource.