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Fuel properties of biochar from torrefaction of ground coffee residue: effect of process temperature, time, and sweeping gas


Ground coffee residue (GCR) was torrified under nitrogen or carbon dioxide atmosphere. Effect of torrefaction parameters on fuel properties of biochar was investigated by varying process temperature, residence time, and sweeping gas flow rate over the range of 200–300 °C, 30–60 min, and 50–250 mL/min, respectively. Severe torrefaction (300 °C) short residence time (30 min) under low carbon dioxide flow rate (50 mL/min) was determined as a promising condition to produce biochar as solid fuel. H/C and O/C atomic ratios, HHV, and energy yield of the obtained biochar were 0.94 and 0.14, 31.12 MJ/kg, and 48.04%, respectively, which were comparable with the properties of sub-bituminous coal. The calculated decarbonization (DC), dehydrogenation (DH), and deoxygenation (DO) indicated that torrefaction led to major losses of oxygen and hydrogen. The analysis of thermal decomposition properties and surface chemical functional groups revealed that temperature substantially affected biochar properties, while the effect of sweeping gas was only marginal.

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This research project is supported by the Mahidol University and Nanomaterial for Energy and Catalyst Laboratory, National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA). This study was partially supported for publication by the China Medical Board (CMB), Center of Excellence on Environmental Health and Toxicology (EHT), Faculty of Public Health, Mahidol University, Thailand.

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Correspondence to Kamonwat Nakason.

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Pathomrotsakun, J., Nakason, K., Kraithong, W. et al. Fuel properties of biochar from torrefaction of ground coffee residue: effect of process temperature, time, and sweeping gas. Biomass Conv. Bioref. 10, 743–753 (2020).

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  • Sweeping gas flow rate
  • Torrefaction
  • Solid fuel
  • Biocoal
  • Waste biomass