Techno-economic analysis of hydrothermal carbonization of sewage sludge for phosphorus retention and carbon sequestration.

Authors

Osama Khoury, Sabrina Spatari, Roy Posmanik

Published in

Waste management (New York, N.Y.). Volume 225. Pages 115780. Jul 31, 2026. Epub Jul 31, 2026.

Abstract

Sludge management is a challenging aspect in wastewater treatment plants (WWTPs). Hydrothermal carbonization (HTC) is a promising thermochemical process, converting wet biomass into a valuable hydrochar (HC), while improving environmental performance. This study evaluates the techno-economic feasibility of integrating HTC into a medium-size WWTP. Approximately 21,000 t yr⁻¹ of sludge could be converted into ∼ 3,066 t yr⁻¹ of HC, achieving a substantial reduction in transported material, while retaining valuable phosphorus. Approximately 73% of the initial sludge carbon was retained in the HC, of which an estimated 49% remained as stable carbon assuming a 67% carbon-stability factor. A techno-economic analysis was conducted considering capital expenditure, operating costs, heat integration, carbon-credit scenarios, and governmental incentives. The estimated capital investment was approximately €2.8 million, with equipment costs accounting for most of the expenditure. Heat integration based on pinch analysis enabled recovery of ∼ 414 kW from a total thermal demand of ∼ 489 kW, corresponding to a heat recovery efficiency of 86% and significantly reducing external energy requirements. The minimum selling price of HC was estimated at €246 t⁻¹, with strong sensitivity to HC production. A sensitivity analysis suggests that a minimum carbon-credit, discount rate and project budget subsidy of €60 t⁻¹ CO₂-eq, 7% and 40%, respectively, are together needed to reduce the dynamic payback-period to below 10 years. Overall, the results demonstrate that HTC can serve as a viable waste-to-resource strategy for WWTPs, supporting circular economy through phosphorus and carbon retention, and reduced management costs.

PMID:
42537262
Bibliographic data and abstract were imported from PubMed on 01 Aug 2026.

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