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Effect of hydrothermal carbonization and torrefaction on spent coffee grounds.
- Source :
-
Agronomy Research . 2021 Special Issue, Vol. 19, p928-943. 16p. - Publication Year :
- 2021
-
Abstract
- Coffee is one of the most tradable commodities worldwide with the current global consumption of over 10 billion kilograms of coffee beans annually. At the same time, a significant amount of solid residues, which are known as spent coffee grounds (SCG), is generated during instant coffee manufacturing and coffee brewing. Those residues have a high potential in various applications, yet they remain mostly unutilized. The current work presents the experimental comparison of two pretreatment technologies - hydrothermal carbonization (HTC) and torrefaction - for converting SCG into a valuable char. The results showed that low-temperature torrefaction (< 250 °C) has a negligible effect on feedstock properties due to initial pre-processing of coffee beans. However, the energy conversion efficiency of torrefaction at higher temperatures is comparable with that of HTC. The average energy yields for high-temperature torrefaction (> 250 °C) and HTC were on the level of 88%. Devolatilization and depolymerization reactions reduce oxygen and increase carbon contents during both processes: chars after torrefaction at 300 °C and HTC at 240 °C had 23-28% more carbon and 43-46% less oxygen than the feedstock. Both pretreatment methods led to a comparable increase in energy density: the highest HHV of 31.03 MJ kg-1 for torrefaction at 300 °C and 32.33 MJ kg-1 for HTC at 240 °C, which is similar to HHV of anthracite. The results showed that both processes can be effectively used to convert SCG into energy-dense char, even though HTC led to slightly higher energy densification rates. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 1406894X
- Volume :
- 19
- Database :
- Academic Search Index
- Journal :
- Agronomy Research
- Publication Type :
- Academic Journal
- Accession number :
- 151635125
- Full Text :
- https://doi.org/10.15159/AR.21.023