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• Protaetia brevitarsis larvae effectively converted spent mushroom substrate from Auricularia auricula (SMS-AA) and Lentinula edodes (SMS-LE). • The larvae produced nutrient-enriched organic fertilizer with a phytotoxicity-free. • The larvae were able to efficiently digest and thus utilize lignocellulose. • We present a new strategy for the use of woodchip-derived spent mushroom substrates. The edible mushroom industry produces massive amounts of spent mushroom substrate (SMS). Thus, there is an urgent need for high-value utilization technology to process the SMS, especially SMSs originating from woodchips. Protaetia brevitarsis larvae (PBL) can feed on various types of organic matter and can produce organic fertilizer and insect protein. In this study, we investigated the potential of PBL to utilize and convert SMSs from Auricularia auricula (SMS-AA) and Lentinula edodes (SMS-LE) cultivation. The results showed that the PBL were able to feed on SMS-AA and SMS-LE and form nutrient-enriched organic fertilizer with a low phytotoxicity and high humic acid content. Further analysis of the organic carbon dynamics suggested that PBL can efficiently digest and utilize lignin. This study demonstrates a new strategy for the utilization of SMSs originating from woodchips, and provides a new model for further investigations on the mechanism of lignin decomposition. [ABSTRACT FROM AUTHOR]

Highlights • P. brevitarsis larvae can convert agricultural residues to organic manure. • Maize and sawdust were converted to manure by larvae. • Larval digestion produced non-phytotoxic manure with high quality humic acids. • Manure humic acids shared structural similarities with soil humic acids. • P. brevitarsis offers a solution to the buildup of agricultural residues in China. Abstract Utilization of the organic residues produced after crop harvesting is currently an important issue across the world. The edible insect Protaetia brevitarsis larvae can feed various organic matters. In this paper, we investigated the potential to utilize the insect to convert herbaceous and ligneous plant residues. We feed the insect larvae with maize straw and sawdust and analyzed the produced insect manure. P. brevitarsis larval was found to be able to digest both herbaceous and ligneous straw and insect manure extract shown no phytotoxicity. The mass fractions of humic acids (HAs) in the insect manure derived from maize straw and sawdust digestion were 24.37% and 14.46%, respectively. The 13C cross-polarization magic-angle spinning nuclear magnetic resonance (CP–MAS NMR) spectra data indicated that the HAs in the insect manure were similar to those found in the soil. These data suggested that P. brevitarsis larvae can be used to convert agricultural residues and produce organic fertilizers. [ABSTRACT FROM AUTHOR]