Hydrothermal Carbonization of Sewage Sludge into Solid Biofuel: Influences of Process Conditions on the Energetic Properties of Hydrochar

Siti Zaharah Roslan, Siti Fairuz Zainudin, Alijah Mohd Aris, Khor Bee Chin, Mohibah Musa, Ahmad Rafizan Mohamad Daud () and Syed Shatir A. Syed Hassan
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Siti Zaharah Roslan: School of Chemical Engineering, College of Engineering, Universiti Teknologi MARA, Shah Alam 40450, Malaysia
Siti Fairuz Zainudin: Indah Water Konsortium Sdn Bhd, No.1 Jalan Damansara, Kuala Lumpur 60000, Malaysia
Alijah Mohd Aris: Indah Water Konsortium Sdn Bhd, No.1 Jalan Damansara, Kuala Lumpur 60000, Malaysia
Khor Bee Chin: Indah Water Konsortium Sdn Bhd, No.1 Jalan Damansara, Kuala Lumpur 60000, Malaysia
Mohibah Musa: School of Chemical Engineering, College of Engineering, Universiti Teknologi MARA, Shah Alam 40450, Malaysia
Ahmad Rafizan Mohamad Daud: School of Chemical Engineering, College of Engineering, Universiti Teknologi MARA, Shah Alam 40450, Malaysia
Syed Shatir A. Syed Hassan: School of Chemical Engineering, College of Engineering, Universiti Teknologi MARA, Shah Alam 40450, Malaysia

Energies, 2023, vol. 16, issue 5, 1-16

Abstract: Hydrothermal carbonization (HTC) is an attractive, green technology for the management of sewage sludge. In this study, low-value secondary sewage sludge was subjected to an HTC treatment in a 1 L batch hydrothermal reactor and transformed into a high-energy-density hydrochar under varying HTC conditions (temperature of 150–300 °C, carbonization time of 30–150 min and a solid loading of 10–30%). The resulting hydrochar fuel characteristics were analyzed for ultimate and proximate analyses, functional group composition and energetic parameters. It was found that the hydrochar yield decreased with the increasing HTC temperature and reaction time, primarily due to the loss of organic volatile matter and functional groups. Under the optimum conditions of 150 °C, 30 min of carbonization time and 30% solid loading, 80.56% of the hydrochar was recovered, providing a maximum energy yield of 90.32% and a high heating value of 18.49 MJ/kg. Compared to the raw sewage sludge (H/C ratio of 2.67 and O/C ratio of 0.51), the hydrochar also had lower H/C and O/C atomic ratios of 1.42 and 0.18, respectively. The results suggest that significant dehydration and decarboxylation during the HTC treatment of sewage sludge have resulted in the formation of carbonaceous hydrochar with energetic properties close to the sub-bituminous coals.

Keywords: hydrothermal; carbonization; sewage sludge; biofuel; hydrochar (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2023
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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