Valorization of Lignocellulosic Biomass Through Anaerobic Digestion after the Cultivation of the Edible Mushroom Lentinula Edodes and Enzymatic Pretreatment

The global scarcity of high-quality protein and food and the imminent effects of climate change have pushed forward scientific efforts to provide sustainable and efficient responses. The use of by-products at industrial facilities has been presented as the most promising alternative to mitigate these global problems. Agricultural byproducts as substrates for the growth of edible food and the subsequent valorization of the non-edible leftovers through anaerobic digestion fulfil this perspective.

The aim of this study was, for the first time, to assess the biomethanation potential of four lignocellulosic by-products (sugarcane bagasse, cocoa husks, coconut shells, and rice hulls) used as substrates mixed with an anaerobic digestate for the cultivation of Lentinula edodes. In addition, enzymatic pretreatment by Trichoderma spp. was also investigated.

The highest methane yield (129 ± 9 NLCH4 kg− 1VS) and the highest maximum methane production rate (9.8 ± 0.7 NLCH4 kg− 1VS d− 1) were observed for the substrate moistened with the anaerobic digestate and the subsequent enzymatic pretreatment. However, the highest kinetic constants of the first-order model were achieved without enzymatic pretreatment (0.090 and 0.091 d− 1). This study highlights the viability of a closed-loop process where otherwise wasted biomass is used to produce edible mushrooms and biogas, a process embedded in a circular economy model.