Potential of Lipids from Polymer-Based Dewatered Sewage Sludge as Feedstock for Biodiesel Production

Nor Afifah Khalil, Mohd Faizar Banjar, Fatin Najwa Joynal Abedin, Ahmad Noor Syimir Fizal, Norkhairi Ahmad, Muzafar Zulkifli, Wirach Taweepreda (), Md Sohrab Hossain and Ahmad Naim Ahmad Yahaya ()
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Nor Afifah Khalil: Polymer Science Program, Division of Physical Science, Faculty of Science, Prince of Songkla University, Hat-Yai 90110, Songkla, Thailand
Mohd Faizar Banjar: Branch Campus Malaysian Institute of Chemical and BioEngineering Technology, Universiti Kuala Lumpur, Alor Gajah 78000, Melaka, Malaysia
Fatin Najwa Joynal Abedin: Branch Campus Malaysian Institute of Chemical and BioEngineering Technology, Universiti Kuala Lumpur, Alor Gajah 78000, Melaka, Malaysia
Ahmad Noor Syimir Fizal: Centre for Sustainability of Mineral and Resource Recovery Technology (SMaRRT), Universiti Malaysia Pahang Al-Sultan Abdullah, Lebuh Persiaran Tun Khalil Yaakob, Gambang 26300, Pahang, Malaysia
Norkhairi Ahmad: Student Development Section, Universiti Kuala Lumpur Business School, Kuala Lumpur 50250, Malaysia
Muzafar Zulkifli: Green Chemistry and Sustainability Cluster, Branch Campus Malaysian Institute of Chemical and BioEngineering Technology, Universiti Kuala Lumpur, Alor Gajah 78000, Melaka, Malaysia
Wirach Taweepreda: Polymer Science Program, Division of Physical Science, Faculty of Science, Prince of Songkla University, Hat-Yai 90110, Songkla, Thailand
Md Sohrab Hossain: HICoE-Centre for Biofuel and Biochemical Research, Institute of Sustainable Energy and Resources, Fundamental and Applied Sciences Department, Universiti Teknologi PETRONAS (UTP), Seri Iskandar 32610, Perak, Malaysia
Ahmad Naim Ahmad Yahaya: Green Chemistry and Sustainability Cluster, Branch Campus Malaysian Institute of Chemical and BioEngineering Technology, Universiti Kuala Lumpur, Alor Gajah 78000, Melaka, Malaysia

Sustainability, 2025, vol. 17, issue 7, 1-20

Abstract: Municipal wastewater treatment plants produce vast amounts of sewage sludge as waste, with more than 80% dewatered sludge (DS). DS is a polymer-based sludge containing flocculant and extracellular polymeric substances, including lipids. Lipids can be converted into biodiesel as an alternative energy that reduces dependency on fossil fuels while helping cities manage waste more sustainably. Past studies explored the potential of lipids from various sewage sludges in biodiesel production. However, the potential of DS remains largely unexplored. This study evaluates the lipid extracted from DS and the potential of its fatty acid methyl ester (FAME) to be used as biodiesel. Lipid extraction was conducted under varying parameters, including temperatures of 70, 80, and 90 °C, extraction time of 2, 4, 6, and 8 h, and sludge-to-solvent (S/L) ratios of 0.05, 0.075, 0.1, 0.125, 0.15, and 0.175 g/mL. The optimal extraction conditions of 70 °C for 4 h at S/L of 0.175 g/mL yielded 1.71 ± 0.10% lipid. FTIR and TGA revealed that the DS lipids contain triglycerides, fatty acids, glycerol, and proteins. Transesterification of DS lipids produced DS FAME with a fatty acid profile ranging from C4:0 to C22:0. The evaluation of DS FAME revealed a high ester content (94.7%) of fatty acids ranging from C14:0 to C24:1, surpassing the minimum standard of 90% for biodiesel. The elevated proportion of unsaturated fatty acids in DS FAME is expected to result in a low melting point, reducing the solidifying effect and enhancing its performance as biodiesel.

Keywords: polymer-based sludge; secondary raw materials; biowaste valorisation; lipid extraction; biodiesel feedstock; sustainable energy; circular economy (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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