Bioconversion-Composting of Golden Needle Mushroom (Flammulina velutipes) Root Waste by Black Soldier Fly (Hermetia illucens, Diptera: Stratiomyidae) Larvae, to Obtain Added-Value Biomass and Fertilizer

Abstract

A new bioconversion-composting process of golden needle mushroom (Flammulina velutipes) root waste was established using black soldier fly larvae (BSFL) to produce added-value biomass and organic fertilizer. The entire process included two stages: BSFL conversion and conventional composting, which lasted 40 days. After a 26-day bioconversion, a considerable quantity of BSFL was obtained, which could be used to produce the protein feed, chitin, antibacterial peptide, biodiesel and so on. The bioconversion parameters of waste reduction rate and BSFL conversion rate were 54.8 ± 0.4 and 5.06 ± 0.27%, respectively. Following the 14-day conventional composting, the mushroom root waste turned into an organic fertilizer. The moisture, organic matter, total nitrogen, total phosphorus, and total potassium concentrations of the obtained fertilizer were 29.3 ± 0.9, 76.0 ± 1.7, 2.74 ± 0.09, 2.07 ± 0.06, and 1.34 ± 0.15%, respectively. The germination index was 65.7 ± 3.2% for Chinese cabbage and 52.9 ± 1.3% for rapeseed. To accelerate bioconversion, increase output of larvae biomass and shorten the developing time of BSFL, two auxiliary materials, nitrogen source, namely, bran and kitchen wastes, were mixed with mushroom roots. Both were significantly effective, and the recommended percentage was 40%. In that case, the developing time reduced to approximately 15–16 days, and the BSFL conversion rate increased by 31.2–172.7%. Accordingly, one simple process flowchart was drawn, and the output was estimated.