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The Journal of the Royal Society of Thailand Vol. 41 No. 3 July-September 2016 118 Abstract Hydrochar Production from Faecal Sludge by Hydrothermal Carbonization Process Chongrak Polprasert Fellow of the Academy of Science, The Royal Society of Thailand Krailak Fakkaew Asian Institute of Technology Thammarat Koottatep Asian Institute of Technology Faecal sludge (FS) contains high concentrations of organic matters and pathogens. Currently, the FS collected from on-site sanitation systems by the municipalities in Thailand is disposed of in landfills, agricultural fields and waterways, which causes environmental pollution and health risks. Approximately 30% of FS is treated by anaerobic digestion and sand drying beds; this is insufficient to overcome the problems. Hydrothermal carbonization (HTC) is a thermo-chemical process which has been found to be effective in converting high moisture biomass into carbonaceous solids, called hydrochar, using a high-pressure reactor (20-60 bar) at a relatively low temperature (180-250 ํC). The hydrochar produced from HTC can be used as solid fuel, energy storage, soil amendment, absorbent in water purifica- tion, and catalyst. The objective of this study was to investigate the technical feasibility of applying the HTC to treat FS. The experimental results of the HTC treatment of FS show the optimum temperature and reaction time to be 250 ํC and 5 h, respectively. The hydrochar yields were 70-75 % of the dried FS, and energy contents of the produced hydrochar were 19-20 MJ/kg, comparable to natural coal such as lignite. Thus, the produced hydrochar can be used as a solid fuel in combustion processes. A case study of the Nontaburi municipality treatment plant showed that about 9,000 m 3 /year of FS is being treated in fermentation tanks and sand drying beds, and the dried sludge (bio-solids) of 72 tons/year is sold for 216,000 Baht/year. If the HTC process is applied for treating the FS, the hydrochar produced of about 337 tons/year could yield a revenue of 1,000,000 Baht/year. Therefore, the HTC is considered as a potential alternative for treating FS and producing valuable hydrochar. Keywords: hydrochar, faecal sludge, hydrothermal carbonization การผลิตถ่านไฮโดรจากสิ่งปฏิกูล โดยกระบวนการไฮโดรเทอร์มัลคาร์บอไนเซชัน