Integrated carbon capture and methanation for valorisation of sludge : process development, optimization and performance evaluation

Abstract

Recent reports indicate that total sludge production in China has exceeded 14 million tons of dry sludge annually. With growing concerns regarding environmental protection and energy sustainability, increased attention has been directed toward sustainable sludge treatment and disposal methods. Traditional approaches, such as combustion, continue to face challenges related to pollutant emissions. The development of integrated carbon capture and methanation (ICCM) technology offers a promising solution by combining carbon capture and conversion processes within a single reactor and employing bifunctional catalysts, thereby reducing both costs and energy consumption. This study aims to investigate the application and potential of integrating sludge incineration with ICCM for the co-production of electricity and methane. To achieve this, a multi-objective optimization framework based on Gaussian Process Regression (GPR) and the Non-dominated Sorting Genetic Algorithm II (NSGA-II) is developed. Both economic (levelized cost of methane, LCOM) and environmental indicators (global warming potential, GWP; ozone formation potential, OFP; and terrestrial acidification potential, TAP) are considered. Five key variables that significantly influence system performance have been identified. The results highlight the importance of enhancing catalyst performance and the availability of cheap and clean hydrogen.