Investigating Sodium Percarbonate for Upgrading Torrefied Spent Coffee Grounds as Alternative Solid Biofuel by Taguchi Optimization

Wei-Hsin Chen, Kuan-Ting Lee (), Ji-Nien Sung, Nai-Yun Hu and Yun-Sen Xu
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Wei-Hsin Chen: Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan 701401, Taiwan
Kuan-Ting Lee: Department of Chemical and Materials Engineering, Tunghai University, Taichung 407224, Taiwan
Ji-Nien Sung: Department of Chemical and Materials Engineering, Tunghai University, Taichung 407224, Taiwan
Nai-Yun Hu: Department of Chemical and Materials Engineering, Tunghai University, Taichung 407224, Taiwan
Yun-Sen Xu: Department of Chemical and Materials Engineering, Tunghai University, Taichung 407224, Taiwan

Energies, 2025, vol. 18, issue 20, 1-15

Abstract: Producing solid biofuels with high calorific value and high storage stability under limited energy consumption has become a crucial focus in the global energy field. Low temperature torrefaction below 300 °C is a common method for producing solid biofuels. However, this approach limits the carbon content and higher heating value (HHV) of the resulting biochar. Sodium percarbonate is a solid oxidant that can assist in the pyrolysis of organic molecules during the torrefaction to increase carbon content of biochar. Incorporating sodium percarbonate as a strategic additive presents a viable means to address the constraints associated with the torrefaction technologies. This study blended sodium percarbonate with spent coffee grounds (SCGs) to prepare torrefied SCG solid biofuels with high calorific value and high carbon content. Based on the Taguchi method with L9 orthogonal arrays, torrefaction temperature is identified as the most influential factor affecting higher heating value (HHV). Results from FTIR, water activity, hygroscopicity, and mold observation confirmed that torrefied SCGs blended with 0.5 wt% sodium percarbonate (0.5TSSCG) exhibited good storage stability. They were not prone to mold growth under ambient temperature and pressure. 0.5TSSCG with a carbon content of 61.88 wt% exhibited a maximum HHV of 29.42 MJ∙kg −1 . These findings indicate that sodium percarbonate contributes to increasing the carbon content and HHV of torrefied SCGs, enabling partial replacement of traditional coal consumption.

Keywords: spent coffee grounds; solid biofuel; sodium percarbonate; Taguchi method; higher heating value (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: 2025
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