Techno-economic and life cycle assessment of an integrated hydrothermal carbonization system for sewage sludge

Mass and energy integration study of hydrothermal carbonization with anaerobic digestion of sewage sludge

“…Wang, Chang and Li [37] reported a positive overall energy recovery from the HTC of sewage sludge coupled with AD (668 MJ per tonne treated), where hydrochar contributed to 59% of the potential energy recovered. Medina-Martos, Istrate, Villamil, G alvez-Martos, Dufour and Mohedano [9] reported in their study a contribution of 77% (562 MJ) from hydrochar to the total potential energy production of a HTC þ AD system.…”

“…The potential economic benefit from the hydrochar production is slightly higher compared with the biogas production. Some studies have found that the hydrochar production can represents up to 55% of the total revenue [9]. Hydrochar yield played a key role on the economic benefit showing higher benefits for those scenarios with 160 C thermal treatment.…”

“…HTC main objective is to transform biomass into a carbon-rich product applying heat (180e250 C) and pressure during a certain period of time [9,18e21]. The main advantage of HTC is that it is carried out in presence of water avoiding the energy-intensive drying step required for thermal processes [3,9,21,22]. Furthermore, the resulting products from the HTC are a solid hydrochar that can be used as a soil amender or fuel source and a process water rich in carbon and organics that can be used for enhanced biogas production [3,12e15,20,23e29].…”

“…This makes the integration of hydrothermal treatment as post-treatment a promising option to harness the energy from sewage digestate. Medina-Martos et al [9], made a techno-economic and life cycle assessment of an integrated HTC system for sewage sludge. They found that the integration of the HTC system helps to reduce environmental impact compared with the conventional WWT configutarion with AD integrated.…”

Hydrochar derived from municipal sludge through hydrothermal processing: A critical review on its formation, characterization, and valorization

“…Consequently, the volume of remaining solids (hydrochar) for management could be significantly reduced. Many studies have suggested that HTC at mild conditions (e.g., 180-250 °C for < 1h) could compromise between energy consumption, dewaterability, hydrochar production, and methane production (92-356 mL CH 4 /g COD) from HTC aqueous (Ahmed et al, 2021a(Ahmed et al, , 2021bAragón-Briceño et al, 2017Ferrentino et al, 2020b;Gaur et al, 2020;Medina-Martos et al, 2020). Danso-Boateng et al (2015) found that Maillard reactions between monosaccharides and amino acids initiated at HTC of 180 °C for over 15 min, which could form non-biodegradable and/or AD inhibitors (e.g., aldehydes, furans, pyrroles, pyrazines, and pyridines) in the aqueous.…”