Globally, approximately 600-700 million tons/yr. of solid waste and 250-300 million tons/yr. of fecal sludge (FS) are not managed in an environmentally safe manner which is a major concern for global warming and climate change. Another environmental concern for global warming is wetlands that globally emit approximately 5 % of total greenhouse gases through organic biomass decomposition. To mitigate these environmental impacts, this study explored the waste-to-energy approach through a thermochemical conversion named hydrothermal liquefaction (HTL). While HTL has been extensively investigated for wet-feedstock valorization, less attention has been paid to enhancing the lighter fraction and heating value improvement. This study optimized the co-HTL process mechanism of organic solid waste (OSW) with Fecal sludge (FS) and peat at different mixing ratios (1:0, 1:3, 1:1, 3:1, and 0:1) and temperature variations (280 to 340 °C) for enhancing lighter biocrude production. The synergistic effect was observed during co-liquefaction of OSW with FS and peat for a mixing ratio of 3:1 at 320°C. The maximum biocrude yield of 51 - 52% was observed for co-liquefaction, of which 60 - 64 % was lighter-fraction. The light biocrude contained 45 - 60 % ester, 12 - 18 % organic acids, and 12 - 26 % fuel hydrocarbon fractions with a small amount of phenol, heterocyclic compounds, and amine derivatives. The findings demonstrated that the decarboxylation, deamination, and esterification mechanism was enhanced during co-liquefaction. The ester-hydrocarbon-rich biocrude exhibited a heating value of 37.4 - 42.7 MJ/kg, suggesting that the produced biocrude would be a potential alternative to fossil fuel (gasoline ~ 43.4 MJ/kg). This energetically feasible process would provide a revenue stream of $ 467 - 568 per metric ton of feedstock, validating the high economic prospects of the waste to energy approach.
Sadib Bin Kabir is a Lecturer at the School of Engineering, Presidency University, Bangladesh. He had worked as a research assistant on Waste to Energy project for three years in the Department of Civil Engineering, Khulna University of Engineering & Technology, Bangladesh. His research interests include global warming and climate change mitigation, anaerobic wastewater treatment, biohythane production, hydrothermal liquefaction, biological pretreatment processes, and transesterification of waste feedstocks. He invests in the development of individuals and build up a strong team spirit about engineering and research by regularly taking engineering, project management, and leadership courses. Recently, he worked on two conversion processes i.e., the co-hydrothermal liquefaction and the anaerobic digestion process of waste to biofuel conversion and published one review paper in Biotechnology Advances, eight Scopus indexed journal articles as well as six international conference proceedings. He is currently looking for opportunities to study Doctor of philosophy in renewable energy.
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