Integration of biogas derived from dark fermentation and anaerobic digestion of biowaste to enhance methanol production by methanotrophs

Abstract

Biowaste-derived sugars or greenhouse gases, such as methane (CH4) and carbon dioxide (CO2), can be used to generate eco-friendly biofuels, such as hydrogen (H2) or methanol. In the present study, enzyme-based rice straw (RS) hydrolysate was used to produce dark-fermentative (DF) biogas (H2 and CO2), which was subsequently integrated with biogas (CH4 and CO2) derived from anaerobic digestion (AD) to generate methanol via methanotrophs. First, DF of RS hydrolysate yielded 2.82 mol of H2/mol of hexose. Second, the integration of biogas derived from DF and AD in the presence of CH4 vectors yielded 13.8 mmol/L of methanol via methanotrophs. Moreover, under the repeated batch mode, 64.6 mmol/L of methanol was produced. This is the first report on the integration of biogas derived from AD and DF of biowaste to produce biomethanol. These findings may facilitate the development of a sustainable biowaste-based circular economy for producing biofuels.