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Title: Minimisation of waste via the valorisation of spent coffee grounds into high-value products
Authors: Singh, Nikita 
Chetty, Manimagalay 
Deenadayalu, Nirmala
Keywords: Spent coffee grounds (SCG);Valorisation;Minimisation
Issue Date: 30-Nov-2023
Publisher: Italian Association of Chemical Engineering - AIDIC
Source: Singh, N., Chetty, M. and Deenadayalu, N. 2023. Minimisation of waste via the valorisation of spent coffee grounds into high-value products. Chemical Engineering Transactions. 106: 427-432 (5). doi:10.3303/CET23106072
Journal: Chemical Engineering Transactions; Vol. 106 
Spent coffee grounds (SCG) valorisation can produce high-value products to supply cosmetics, petroleum and
pharmaceutical industries among others. An overview of the various products achievable from spent coffee
grounds valorisation are established, while the effect of temperature, reaction time and solid-to-liquid loading
ratio on the yield of caffeine extracted from SCG was investigated. The best extraction solvent between (i)
dichloromethane, (ii) 1-ethyl-3-methylimidazolium chloride (IL) and (iii) water was established. Characterisation
of SCG using Technical Association of the Pulp and Paper (TAPPI) methods was carried out. Variations of
parameters were established using the Box-Behnken design of experiment (DOE) which varied the investigated
parameters; (i) temperature (88 – 120 ºC), (ii) reaction time (15 - 35 min) and (iii) solid-to-liquid loading ratio (5
g SCG per 10 -25 mL). The conventional extraction method used dichloromethane as the extraction solvent,
whereas the green method used the ionic liquid and water in a Parr pressure reactor. High performance liquid
chromatography (HPLC) quantified the yield of extracted caffeine. Recrystallised caffeine is analysed using
scanning electron microscopy (SEM), transition electron microscopy (TEM) and energy dispersive spectroscopy
(EDS) for its structural properties, crystalline structure and physical analysis, while differential scanning
calorimetry (DSC) established the purity of extracted caffeine achieved from each extraction solvent.
The expected yield of caffeine is between 4.67 and 8.0 mg/g SCG. According to this experimental methodology,
at 120 ºC, 25 min reaction time and 25 mL solvent volume the extraction yield ranged from 2.83 to 3.67 mg/g
ISSN: 2283-9216
DOI: 10.3303/CET23106072
Appears in Collections:Research Publications (Engineering and Built Environment)

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