Eco-toxicological and climate change effects of sludge thermal treatments: Pathways towards zero pollution and negative emissions
Artikel i vetenskaplig tidskrift, 2024

The high moisture content and the potential presence of hazardous organic compounds (HOCs) and metals (HMs) in sewage sludge (SS) pose technical and regulatory challenges for its circular economy valorisation. Thermal treatments are expected to reduce the volume of SS while producing energy and eliminating HOCs. In this study, we integrate quantitative analysis of SS concentration of 12 HMs and 61 HOCs, including organophosphate flame retardants (OPFRs) and per- and poly-fluoroalkyl substances (PFAS), with life-cycle assessment to estimate removal efficiency of pollutants, climate change mitigation benefits and toxicological effects of existing and alternative SS treatments (involving pyrolysis, incineration, and/or anaerobic digestion). Conventional SS treatment leaves between 24 % and 40 % of OPFRs unabated, while almost no degradation occurs for PFAS. Thermal treatments can degrade more than 93% of target OPFRs and 95 % of target PFAS (with the rest released to effluents). The different treatments affect how HMs are emitted across environmental compartments. Conventional treatments also show higher climate change impacts than thermal treatments. Overall, thermal treatments can effectively reduce the HOCs emitted to the environment while delivering negative emissions (from about −56 to −111 kg CO2-eq per tonne of sludge, when pyrolysis is involved) and producing renewable energy from heat integration and valorization.

Wastewater treatment



Anaerobic digestion


Heavy metals


Marjorie Morales

Norges teknisk-naturvitenskapelige universitet

Hans Peter H. Arp

Norges teknisk-naturvitenskapelige universitet

Stiftelsen Norges Geotekniske Institutt

Gabriela Castro

Norges teknisk-naturvitenskapelige universitet

Universidade de Santiagode Compostela

Alexandros G. Asimakopoulos

Norges teknisk-naturvitenskapelige universitet

Erlend Sørmo

Stiftelsen Norges Geotekniske Institutt

Norges miljø- og biovitenskapelige universitet

Gregory Peters

Chalmers, Teknikens ekonomi och organisation, Environmental Systems Analysis

F. Cherubini

Norges teknisk-naturvitenskapelige universitet

Journal of Hazardous Materials

0304-3894 (ISSN) 18733336 (eISSN)

Vol. 470 134242


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