Thermochemical Co-Valorization of Sewage Sludge and Plastic Waste: Co-Processing and Sludge-Derived Catalysis
- 1Center of Physical-Chemical Methods of Research and Analysis, Farabi University, Almaty 050012, Kazakhstan
- 2Laboratory for Chemical Technology, Industriele Scheikunde, Ghent University, Technologiepark-Zwijnaarde 125, 9052 Gent, Belgium
Abstract
Plastic waste and sewage sludge (SS) are abundant, heterogeneous waste streams whose utilization and recycling are constrained by contamination, variable composition, and limited resource recovery. This review evaluates their integrated thermochemical conversion, focusing on co-incineration, co-pyrolysis, co-gasification, hydrothermal co-carbonization, hydrothermal co-liquefaction, and the use of SS-derived char (SSC) and sewage sludge ash (SSA) as catalytic materials. Co-processing benefits arise from complementary feedstock properties: plastics provide high carbon, hydrogen, volatile matter (VM), and heating value, whereas SS contributes oxygenated intermediates and mineral phases containing Si, Al, Fe, Ca, Mg, and P. Among the reviewed routes, co-pyrolysis shows the strongest evidence of non-additive interactions, including hydrogen transfer, altered decomposition kinetics, and changes in liquid composition. Co-gasification can enhance H2 formation and tar conversion, while hydrothermal routes are especially attractive for wet SS but remain comparatively underexplored. The review further distinguishes SSA, dominated by mineral acid–base and redox functionality, from SSC, which combines these mineral effects with adsorption and surface reactions on a porous carbon matrix. Key barriers include catalyst deactivation, chlorine and sulfur poisoning, heavy-metal migration, feedstock variability, and limited pilot-scale validation. Future development requires mechanistic controls, catalyst stability testing, techno-economic analysis, life-cycle assessment, and integrated nutrient recovery to establish practical circular waste-management systems.
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BibTeX
@article{zabara2026thermochemical,
title = {{Thermochemical Co-Valorization of Sewage Sludge and Plastic Waste: Co-Processing and Sludge-Derived Catalysis}},
author = {Nazar Zabara and Diyar Tokmurzin and Aigerim Kaiaidarova and Fedor Pogorov and Akezhan Balgarayev and Valeriy Panyukov and Yelena Vitoshnova and Sergey Efremov and Sergey Nechipurenko},
journal = {Polymers},
year = {2026},
month = oct,
doi = {10.3390/polym18202548},
url = {https://www.mdpi.com/2073-4360/18/20/2548},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Thermochemical Co-Valorization of Sewage Sludge and Plastic Waste: Co-Processing and Sludge-Derived Catalysis
AU - Nazar Zabara
AU - Diyar Tokmurzin
AU - Aigerim Kaiaidarova
AU - Fedor Pogorov
AU - Akezhan Balgarayev
AU - Valeriy Panyukov
AU - Yelena Vitoshnova
AU - Sergey Efremov
AU - Sergey Nechipurenko
PY - 2026
DA - 2026/10/01
JO - Polymers
DO - 10.3390/polym18202548
UR - https://www.mdpi.com/2073-4360/18/20/2548
AB - Plastic waste and sewage sludge (SS) are abundant, heterogeneous waste streams whose utilization and recycling are constrained by contamination, variable composition, and limited resource recovery. This review evaluates their integrated thermochemical conversion, focusing on co-incineration, co-pyrolysis, co-gasification, hydrothermal co-carbonization, hydrothermal co-liquefaction, and the use of SS-derived char (SSC) and sewage sludge ash (SSA) as catalytic materials. Co-processing benefits arise from complementary feedstock properties: plastics provide high carbon, hydrogen, volatile matter (VM), and heating value, whereas SS contributes oxygenated intermediates and mineral phases containing Si, Al, Fe, Ca, Mg, and P. Among the reviewed routes, co-pyrolysis shows the strongest evidence of non-additive interactions, including hydrogen transfer, altered decomposition kinetics, and changes in liquid composition. Co-gasification can enhance H2 formation and tar conversion, while hydrothermal routes are especially attractive for wet SS but remain comparatively underexplored. The review further distinguishes SSA, dominated by mineral acid–base and redox functionality, from SSC, which combines these mineral effects with adsorption and surface reactions on a porous carbon matrix. Key barriers include catalyst deactivation, chlorine and sulfur poisoning, heavy-metal migration, feedstock variability, and limited pilot-scale validation. Future development requires mechanistic controls, catalyst stability testing, techno-economic analysis, life-cycle assessment, and integrated nutrient recovery to establish practical circular waste-management systems.
SN - 2073-4360
ER -