Study of Valorisation Routes of Spent Coffee Grounds
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ORIGINAL PAPER
Study of Valorisation Routes of Spent Coffee Grounds Konstantinos Passadis1 · Vassileios Fragoulis1 · Vasileia Stoumpou1 · Jelica Novakovic1 · Elli Maria Barampouti1 · Sofia Mai1 · Konstantinos Moustakas1 · Dimitris Malamis1 · Maria Loizidou1 Received: 17 February 2020 / Accepted: 18 May 2020 © Springer Nature B.V. 2020
Abstract Purpose The energy crisis is an eminent problem that needs to be dealt with urgently. Thus, alternative routes for the production of biofuels are sought. This paper investigated experimentally the possibility of biodiesel and bioethanol production from spent coffee grounds (SCG), aiming at the same time to manage an emerging waste stream. Methods SCG have oil and cellulose contents of 12.89% and 9.87%, respectively that may be valorized accordingly. Having chosen the Soxhlet method as an extraction method for oils and fats and by examining two different solvents: methanol as a polar compound and hexane as a nonpolar, the effect of the Soxhlet extraction cycles (time of experiment) and the ratio of solvent to raw material was studied. Furthermore, enzymatic saccharification and alcoholic fermentation were chosen as the means to valorise cellulose. Results It was proved that hexane is a more efficient solvent with oil extraction yields ranging from 73.15 to 97.21%. The highest yield was obtained for 20 extraction cycles and solvent to raw material ratio equal to 20. As far as enzymatic hydrolysis is concerned, the maximum saccharification yield for SCG was 44.20% which was achieved under the following conditions: NaOH 0.3 M and CellicCTec2 75 µL/g cellulose. Conclusion It is thus technically feasible to recover and extract the oil content from spent coffee grounds as well as to achieve moderate saccharification yields and to this direction an integrated biorefinery was proposed. Estimating the potential of SCG as feedstock for biodiesel and bioethanol production at global level, it was evident that SCG can contribute to the energy strategy through biofuels promotion. Graphic Abstract
Keywords Alkaline delignification · CellicCtec2 · Hexane · Methanol · Spent coffee grounds * Maria Loizidou [email protected]
Statement of Novelty
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SCG, from coffee brewing, are highly available worldwide. The SCG quantities suggest huge quantities of lignocellulosic waste that may be valorised towards the increase of the
School of Chemical Engineering, Unit of Environmental Science Technology, National Technical University of Athens, 9 Heroon Polytechniou Str., Zographou Campus, 15780 Athens, Greece
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energy matrix. Yet, this application is just limited. SCG are good substrate for enzymatic hydrolysis and transesterification by which they can be converted to various added-value products via diverse platforms. This study was conducted to recover sugars and oil from SCG aiming to set up a SCG biorefinery, integrating the experimentally validated possible valorization routes. Thus, this paper demonstrates a technical assessment of biofuels production wit
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