Volume 18, Issue 3 (12-2025)
ijhe 2025, 18(3): 447-474 |
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Sajadi A, Shekoohiyan S, Moussavi G. Evaluation of hydrochar quality and high heating value derived from spent coffee grounds. ijhe 2025; 18 (3) :447-474
URL: http://ijhe.tums.ac.ir/article-1-7062-en.html
URL: http://ijhe.tums.ac.ir/article-1-7062-en.html
1- Department of Environmental Health Engineering, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
2- Department of Environmental Health Engineering, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran ,s.shekoohiyan@modares.ac.ir
2- Department of Environmental Health Engineering, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran ,
Abstract: (467 Views)
Background and Objective: The increasing accumulation of spent coffee grounds (SCG) has raised serious environmental concerns. This study aimed to evaluate the efficiency of the hydrothermal carbonization process in converting SCG into a valuable solid fuel..
Materials and Methods: An experimental study was conducted using the design of experiments (DOE) approach and response surface methodology (RSM). The effects of key independent variables—including temperature (180–290 °C), reaction time (30–90 min), and liquid-to-solid ratio (L:S, 1:1–15:1)—on the properties of the produced hydrochar were investigated. A total of 20 experiments were carried out, and physicochemical analyses were performed on both the hydrochar and the process water.
Results: The results indicated that the quadratic model demonstrated strong predictive capability for hydrochar yield (HY) and higher heating value (HHV) (R² > 0.98). Analysis of variance showed that all three independent variables had significant effects on HY and HHV. The produced hydrochar showed HHV of 17.9–28.5 MJ/kg and HY of 17.5–77.2%. Response surface methodology identified 235 °C, 180 min, and L:S 4:1 as optimal for desirable HY and HHV. Optimization indicated 229 °C, 160 min, and L:S 4:1 yielded hydrochar with 27.8 MJ/kg HHV, 67.9% HY, with 0.891 desirability. CHNSO analysis showed a decrease in H/C and O/C ratios and an increase in surface area from 2.4 to 12.6 m²/g.
Conclusion: Given the favorable HHV of the produced hydrochar, it can be concluded that the proposed process is an effective method for converting biomass into solid fuel.
Materials and Methods: An experimental study was conducted using the design of experiments (DOE) approach and response surface methodology (RSM). The effects of key independent variables—including temperature (180–290 °C), reaction time (30–90 min), and liquid-to-solid ratio (L:S, 1:1–15:1)—on the properties of the produced hydrochar were investigated. A total of 20 experiments were carried out, and physicochemical analyses were performed on both the hydrochar and the process water.
Results: The results indicated that the quadratic model demonstrated strong predictive capability for hydrochar yield (HY) and higher heating value (HHV) (R² > 0.98). Analysis of variance showed that all three independent variables had significant effects on HY and HHV. The produced hydrochar showed HHV of 17.9–28.5 MJ/kg and HY of 17.5–77.2%. Response surface methodology identified 235 °C, 180 min, and L:S 4:1 as optimal for desirable HY and HHV. Optimization indicated 229 °C, 160 min, and L:S 4:1 yielded hydrochar with 27.8 MJ/kg HHV, 67.9% HY, with 0.891 desirability. CHNSO analysis showed a decrease in H/C and O/C ratios and an increase in surface area from 2.4 to 12.6 m²/g.
Conclusion: Given the favorable HHV of the produced hydrochar, it can be concluded that the proposed process is an effective method for converting biomass into solid fuel.
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