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Article

Pyrolysis of Solid Digestate from Sewage Sludge and Lignocellulosic Biomass: Kinetic and Thermodynamic Analysis, Characterization of Biochar

1
Faculty of Chemistry and Chemical Engineering, University of Maribor, Smetanova ul. 17, 2000 Maribor, Slovenia
2
IKEMA d.o.o., Institute for Chemistry, Ecology, Measurements and Analytics, Lovrenc na Dravskem polju 4, 2324 Ptuj, Slovenia
3
Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Ul. Ivana Lučića 5, 10000 Zagreb, Croatia
*
Author to whom correspondence should be addressed.
Academic Editor: Idiano D’Adamo
Sustainability 2021, 13(17), 9642; https://doi.org/10.3390/su13179642
Received: 21 July 2021 / Revised: 24 August 2021 / Accepted: 24 August 2021 / Published: 27 August 2021
(This article belongs to the Topic Actions for Bioenergy and Biofuels: A Sustainable Shift)
This study investigates the pyrolysis behavior and reaction kinetics of two different types of solid digestates from: (i) sewage sludge and (ii) a mixture of sewage sludge and lignocellulosic biomass—Typha latifolia plant. Thermogravimetric data in the temperature range 25–800 °C were analyzed using Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose kinetic methods, and the thermodynamic parameters (ΔH, ΔG, and ΔS) were also determined. Biochars were characterized using different chemical methods (FTIR, SEM–EDS, XRD, heavy metal, and nutrient analysis) and tested as soil enhancers using a germination test. Finally, their potential for biosorption of NH4+, PO43−, Cu2+, and Cd2+ ions was studied. Kinetic and thermodynamic parameters revealed a complex degradation mechanism of digestates, as they showed higher activation energies than undigested materials. Values for sewage sludge digestate were between 57 and 351 kJ/mol, and for digestate composed of sewage sludge and T. latifolia between 62 and 401 kJ/mol. Characterizations of biochars revealed high nutrient content and promising potential for further use. The advantage of biochar obtained from a digestate mixture of sewage sludge and lignocellulosic biomass is the lower content of heavy metals. Biosorption tests showed low biosorption capacity of digestate-derived biochars and their modifications for NH4+ and PO43− ions, but high biosorption capacity for Cu2+ and Cd2+ ions. Modification with KOH was more efficient than modification with HCl. The digestate-derived biochars exhibited excellent performance in germination tests, especially at concentrations between 6 and 10 wt.%. View Full-Text
Keywords: digestate; pyrolysis; kinetics; thermogravimetric analysis; biochar characterization; germination test; biosorption digestate; pyrolysis; kinetics; thermogravimetric analysis; biochar characterization; germination test; biosorption
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MDPI and ACS Style

Petrovič, A.; Vohl, S.; Cenčič Predikaka, T.; Bedoić, R.; Simonič, M.; Ban, I.; Čuček, L. Pyrolysis of Solid Digestate from Sewage Sludge and Lignocellulosic Biomass: Kinetic and Thermodynamic Analysis, Characterization of Biochar. Sustainability 2021, 13, 9642. https://doi.org/10.3390/su13179642

AMA Style

Petrovič A, Vohl S, Cenčič Predikaka T, Bedoić R, Simonič M, Ban I, Čuček L. Pyrolysis of Solid Digestate from Sewage Sludge and Lignocellulosic Biomass: Kinetic and Thermodynamic Analysis, Characterization of Biochar. Sustainability. 2021; 13(17):9642. https://doi.org/10.3390/su13179642

Chicago/Turabian Style

Petrovič, Aleksandra, Sabina Vohl, Tjaša Cenčič Predikaka, Robert Bedoić, Marjana Simonič, Irena Ban, and Lidija Čuček. 2021. "Pyrolysis of Solid Digestate from Sewage Sludge and Lignocellulosic Biomass: Kinetic and Thermodynamic Analysis, Characterization of Biochar" Sustainability 13, no. 17: 9642. https://doi.org/10.3390/su13179642

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