Enhancing Wastewater Treatment Sustainability Through Integrated Anaerobic Digestion and Hydrothermal Carbonization: A Life-Cycle Perspective

Kayode J. Taiwo, Andrada V. Oancea, Nithya Sree Kotha and Joseph G. Usack ()
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Kayode J. Taiwo: Department of Food Science and Technology, University of Georgia, 100 Cedar Street, Athens, GA 30602, USA
Andrada V. Oancea: Environmental Biotechnology Group, Department of Geosciences, University of Tübingen, 94–96 Schnarrenbergstr, 72076 Tübingen, Germany
Nithya Sree Kotha: Department of Food Science and Technology, University of Georgia, 100 Cedar Street, Athens, GA 30602, USA
Joseph G. Usack: Department of Food Science and Technology, University of Georgia, 100 Cedar Street, Athens, GA 30602, USA

Sustainability, 2025, vol. 17, issue 16, 1-20

Abstract: Wastewater treatment plants (WWTPs) are critical infrastructure that lessen the environmental impacts of human activity by stabilizing wastewaters laden with organics, chemicals, and nutrients. WWTPs face an increasing global population, greater wastewater volumes, stricter environmental regulations, and additional societal pressures to implement more sustainable and energy-efficient waste management strategies. WWTPs are energy-intensive facilities that generate significant GHG emissions and involve high operational costs. Therefore, improving the process efficiency can lead to widespread environmental and economic benefits. One promising approach is to integrate anaerobic digestion (AD) with hydrothermal carbonization (HTC) to enhance sludge treatment, optimize energy recovery, create valuable bio-based materials, and minimize sludge disposal. This study employs an LCA to evaluate the environmental impact of coupling HTC with AD compared to conventional AD treatment. HTC degrades wastewater sludge in an aqueous medium, producing carbon-dense hydrochar while reducing sludge volumes. HTC also generates an aqueous byproduct containing >30% of the original carbon as simple organics. In this system model, the aqueous byproduct is returned to AD to generate additional biogas, which then provides heat and power for the WWTP and HTC process. The results indicate that the integrated AD + HTC system significantly reduces environmental emissions and sludge volumes, increases net energy recovery, and improves wastewater sludge valorization compared to conventional AD. This research highlights the potential of AD + HTC as a key circular bioeconomy strategy, offering an innovative and efficient solution for advancing the sustainability of WWTPs.

Keywords: wastewater treatment; anaerobic digestion; hydrothermal carbonization; life-cycle assessment; environmental sustainability (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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