Coupling hydrothermal carbonization with anaerobic digestion: an evaluation based on energy recovery and hydrochar utilization

Abstract

This work evaluates the effect of hydrothermal carbonization (HTC) as a pretreatment and post-treatment technique to anaerobic digestion (AD) of dairy sludge. HTC's effect on AD was evaluated based on energy recovery, nutrient transformation, and hydrochar utilization. The first approach was executed by performing HTC under a range of temperatures before mesophilic AD. HTC optimal pretreatment temperature was 210 °C for 30 min residence time. HTC pretreatment significantly increased the methane yield potential by 192%, the chemical oxygen demand removal by 18%, and the sludge biodegradability during AD by 30%. On the other hand, the application of HTC after AD (post-treatment) increased the total energy production, i.e., in addition to methane, a hydrochar with a caloric value of 10.2 MJ/kg was also obtained. Moreover, HTC post-treatment improved the steam gasification performance of the AD digestate. From the fertilizer quality point of view, HTC implementation generally boosted the concentrations of macro, micro, and secondary nutrients, suggesting its suitability for use as a liquid fertilizer. Overall, the findings of the present study indicate that if bioenergy production were the main target, HTC post-treatment following AD would lead to the most promising outcomes.

Exergetic sustainability analysis of municipal solid waste treatment systems: A systematic critical review

“…The evolved syngas can be used to synthesize liquid transportation fuels and fine valuable chemicals using chemical and biological routes. The generated hydrochar can be utilized for soil amendment, carbon sequestration, wastewater pollution remediation, and energy carriers production [223,224]. The main advantage of hydrothermal processing over other thermochemical methods is the lower emissions of harmful gases to the atmosphere (particularly SOX) [225].…”

Enhancing biomethane production from citrus waste: An integrated approach of hydrothermal carbonization and anaerobic digestion for sustainable waste management

“…Efficient management of organic waste is a global imperative, posing challenges to both environmental sustainability and resource utilization. Addressing this challenge, innovative approaches, such as the integration of hydrothermal carbonization (HTC) with anaerobic digestion (AD), have been explored in recent studies (Li et al, 2023;Zhu et al, 2021;Al Ramahi et al, 2021). HTC, involving the carbonization of organic materials is a process where biodegradable wastes are treated in hot water at temperatures between 180 and 250 °C in closed reactors with residence times between 0.5 and 9 hours and steam pressures between 10 and 50 bar.…”