Efficient bioconversion of organic wastes to value-added chemicals by soaking, black soldier fly (Hermetia illucens L.) and anaerobic fermentation

Abstract

Corncob degradation is an issue that needs to be address for it to be further utilized as bioenergy. We explored a new comprehensive degradation strategy for corncob. First, restaurant wastewater was used to improve the corncob biochemical characteristics and partly degrade the lignocelluloses. After the restaurant wastewater treatment, the residue was converted using black soldier fly larvae (BSFL), and the supernatant was utilized for biogas production by anaerobic fermentation. The highest product rates of glucose, xylose, and arabinose were obtained at the optimal corncob soaking condition at 75 °C, 5 h, and 60 g/L from lignocellulose. The soaking residue was converted using BSFL for 10 days, and 24.34% grease yield was extracted. The soaking residue can be utilized by BSFL and produce grease, which is similar to other wastes such as rice straw and pig manure. The corncob soaking supernatant was utilized for biogas production by anaerobic fermentation. The degradation of cellulose, hemicellulose, and lignin reached about 27.34%, 45.14%, and 29.33%, respectively. A total of 500 mL supernatant mixed with 30% anaerobic sludge under 35 ± 2 °C produced about 7.52 L of biogas with about 3.22 L methane. In conclusion, the above comprehensive process can effectively degrade lignocellulose in corncob and obtain two bioenergy products, namely insect grease and biogas.

Keywords: Anaerobic fermentation; Bioconversion; Bioenergy; Black soldier fly; Corncob; Restaurant wastewater.