Sustainable strategy for lignocellulosic crop wastes reduction by Tenebrio molitor Linnaeus (mealworm) and potential use of mealworm frass as a fertilizer

Abstract

Lignocellulosic crop wastes (LCW) are refractory solid wastes that are not biodegradable at appreciable rates in most environments, causing management of LCW been environmental concerns for years. This study investigated the feasibility of low waste emission complete LCW (rice straw (RS), rice husk (RH), and corn straw (CS)) recycling through feeding to Tenebrio molitor Linnaeus larvae (mealworms) using egested frass to produce organic fertilizers. For larvae fed RS, CS, and RH plus nutrients co-diets groups, the 48-day average specific rates of LCW consumption increased by 118.09%, 155.30%, and 87.14%, respectively when compared with that of sole diet groups. The order of the feed consumption rate and conversion rate in a mealworm farm fed on the three LCWs agreed with the trend obtained with lab-scale experiments, with RS＞CS＞RH. The forty-eight days cellulose, hemicellulose, and lignin biodegradation increased by 1.48–17.61%, 4.26–11.50%, and 4.20–15.75%, respectively, for co-fed larvae. Enterococcus sp. and Erwinia sp., which previous reports have indicated are strongly associated with lignocellulose degradation, were identified in the gut microbiome of mealworms fed with RS and CS co-diets. Furthermore, the RS-fed frass quickly formed a high-quality compost within 32 days of composting, which had a germination rate ratio of 8% and 17% higher than that of WB and CS-fed frass. LCA (life cycle assessment) proved a relatively promising environmental-friendly alternative to dispose of RS, using their excreted frass for composting with low waste emissions. This study provides new insight into insect-involved crop waste utilization, and economical strategies for sustainable in situ recycling of LCWs into high-value-added products.