Tag Archives: spent coffee grounds

xxx E. Sermyagina, C. Mendoza and I. Deviatkin
Effect of hydrothermal carbonization and torrefaction on spent coffee grounds
Abstract |

Effect of hydrothermal carbonization and torrefaction on spent coffee grounds

E. Sermyagina¹*, C. Mendoza¹² and I. Deviatkin³

¹LUT University, Department of Energy Technology, PL 20, 53851 Lappeenranta, Finland
²Federal University of Minas Gerais, 31270-901 Belo Horizonte, MG Brazil
³LUT University, Department of Sustainability Science, PL 20, 53851 Lappeenranta, Finland
*Correspondence: ekaterina.sermyagina@lut.fi

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.

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923-935 L. Zihare, R. Soloha & D. Blumberga
The potential use of invasive plant species as solid biofuel by using binders
Abstract |
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The potential use of invasive plant species as solid biofuel by using binders

L. Zihare,* R. Soloha & D. Blumberga

Riga Technical University, Faculty of Electrical Engineering, Institute of Energy Systems and Environment, Āzenes iela 12/1, LV-1048 Riga, Latvia
*Correspondence to the author: lauma.zihare@rtu.lv

Abstract:

The aim of the current research is to find sustainable pellet resources that are not made from forestry, agricultural materials, or food products. Evaluation has been carried out by experimentally determining the biofuel parameters of two invasive plant species. In comparison to the process of finding a new application, their use in the production of solid biofuel pellets would not require additional investment for the construction of a new pellet production plant. The article’s hypothesis suggests that biofuel parameters for invasive plant species are sufficient for the production of solid biofuel and that their properties can be improved by binders that are available worldwide in the form of residues.
The experiment was carried out for two invasive plant species that are widespread in Latvia – Heracleum sosnowskyi Manden and Solidago canadensis L. The binders used include potato peel waste and spent coffee grounds. All of the tests have been carried out according to ISO standards on biofuel testing. Results show that H sosnowskyi is more suitable for solid biofuel than S canadensis as it has a higher calorific value and an ash content that is two times lower – 3 wt%. Coffee grounds are a suitable binder because they increase calorific value.
The type and amount of binders partly confirms the hypothesis, since both binders reduced the amount of ash in pellets. Further research is needed to carry out pellet durability tests. It is also necessary to carry out an economic analysis in order to evaluate how beneficial it may be to use H sosnowskyi as a solid fuel in existing pellet production plants, thereby avoiding large initial investments and not encouraging the cultivation of invasive plant species.

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