A review of wastewater sludge-to-energy generation focused on thermochemical technologies: An improved technological, economical and socio-environmental aspect

Abstract

In response to increasing global waste generation due to population growth, urbanization, and industrialization, wastewater treatment operations should shift from being solely energy consumers to becoming energy producers by harnessing energy from wastewater sludge (WWS). This approach holds great potential for meeting energy demands and addressing the challenges of waste treatment. The recovery of heat and electrical energy from WWS offers a viable solution to reduce costs within WWTPs. Thermochemical treatment technologies such as pyrolysis, gasification, and combustion hold the potential for energy recovery due to their efficiency, reaction times, and energy retrieval capabilities. These technologies demonstrate feasibility in terms of operational costs, circular economy principles, and socio-environmental impact, thanks to ongoing advancements in waste-to-energy research. This review aims to explore the feasibility of recovering bioenergy (biogas or syngas) from WWS to generate energy, including heat, electricity, and other innovative products. The article provides a critical and comprehensive examination of thermochemical technologies, taking into account technological, economic, and socio-environmental factors. It then presents potential integration techniques that effectively combine anaerobic digestion with other energy conversion technologies to enhance the recovery of syngas, biogas, and flue-gas energy. The results of this study underscore the significant energy potential in wastewater sludge-to-energy generation schemes.