Potential of Torrefied Coffee Grounds to Be Used as Fuel in Thermal Power Plants

• Published in: Journal of biosystems engineering Vol. 49; no. 2; pp. 112 - 119
• Main Authors: Park, Sunyong, Kim, Seok Jun, Kim, Ha Eun, Kim, Seon Yeop, Oh, Kwang Cheol, Cho, Lahoon, Jeon, Young Kwang, Kim, DaeHyun
• Format: Journal Article
• Language: English
• Published: Singapore Springer Nature Singapore 01-06-2024; 한국농업기계학회
• Subjects: Agriculture; Control; Engineering; Environmental Engineering/Biotechnology; Mechatronics; Original Article; Robotics; 농학; Torrefaction; Coffee spent waste; Volatile ignitability; Combustibility index
• ISSN: 1738-1266; 2234-1862
• DOI: 10.1007/s42853-024-00220-5

Purpose
To replace coal used in thermal power plants, this study was conducted to investigate the potential of torrefied coffee spent waste (CSW) as a fuel source.
Methods
Approximately 102 ± 2 g of CSW pellets was torrefied using electric furnaces and stainless-steel containers. The torrefaction of CSW pellets (SCG) was performed at 230 to 310 °C in 20 °C temperature increments for 1 h. To avoid oxygen reactions, a 30-min chilling period was allowed before the subsequent elemental and thermogravimetric analyses (TGA). Furthermore, decarbonization, dehydrogenation, and deoxygenation were evaluated and combustibility was observed using the combustibility index (CI) and volatile ignitability (VI).
Results
Results revealed a calorific value of 22.22–29.39 MJ/kg and mass yield rates ranging between 47.16 and 89.81%. The energy yield was 62.97–90.67%, while decarbonization, dehydrogenation, and deoxygenation were 2.99–33.85%, 12.34–74.79%, and 18.22–76.99%, respectively. No combustion issues were detected as indicated by the VI and CI values which were 19.09–26.71 MJ/kg and 30.61–82.57 MJ/kg, respectively. Compared with coal, CSW can be substitute lignite or sub-bituminous coal.
Conclusion
Torrefaction improves CSW energy properties and might be a promising alternative to wood chips as fuel. When designing a standard torrefaction boiler, temperatures of 270 ℃ or greater must be considered for optimal results.