Optimisation and characterisation of hydrochar production from spent coffee grounds by hydrothermal carbonisation

Afolabi, Oluwasola O.D.; Sohail, M.; Cheng, Yu-Ling

doi:10.1016/j.renene.2019.09.098

Cited by 123 publications

(65 citation statements)

References 57 publications

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“…One of the most used mechanisms for the synthesis of a carbonaceous precursor, which is used in this work, is hydrothermal carbonization. This mechanism is suitable for residues with high moisture content (>50% weight) -such as spent coffee grounds- obviating the need for energy drying before or during the process 34 . In addition, after the process, a liquid is obtained that contains compounds of value-added such as polyphenols and the use of a relatively low temperature (80 °C with the typical processing temperatures ranges for biomass from 270 °C to 370 °C) 35 and low pressure (11 MPa), avoids degradation of the phenolic compounds present in the sample 36 .…”

Section: Introductionmentioning

confidence: 99%

Extraction of polyphenols and synthesis of new activated carbon from spent coffee grounds

Ramón-Gonçalves

Alcaraz

Pérez-Ferreras

et al. 2019

Sci Rep

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A valorization process of spent coffee grounds (SCG) was studied. Thus, a two-stage process, the first stage of polyphenols extraction and synthesis of a carbonaceous precursor and a subsequent stage of obtaining activated carbon (AC) by means of a carbonization process from the precursor of the previous stage, was performed. The extraction was carried out with a hydro-alcoholic solution in a pressure reactor, modifying time, temperature and different mixtures EtOH:H2O. To optimize the polyphenols extraction, a two-level factorial experimental design with three replicates at the central point was used. The best results were obtained by using a temperature of 80 °C during 30 min with a mixture of EtOH:H2O 50:50 (v/v). Caffeine and chlorogenic acid were the most abundant compounds in the analysed extracts, ranging from 0.09 to 4.8 mg∙g−1 and 0.06 to 9.7 mg∙g−1, respectively. Similarly, an experimental design was realized in order to analyze the influence of different variables in the AC obtained process (reaction time, temperature and KOH:precursor ratio). The best results were 1 h, 850 °C, and a mixture of 2.5:1. The obtained activated carbons exhibit a great specific surface (between 1600 m2∙g−1 and 2330 m2∙g−1) with a microporous surface. Finally, the adsorption capacity of the activated carbons was evaluated by methylene blue adsorption.

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Section: Introductionmentioning

confidence: 99%

Extraction of polyphenols and synthesis of new activated carbon from spent coffee grounds

Ramón-Gonçalves

Alcaraz

Pérez-Ferreras

et al. 2019

Sci Rep

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“…Recently, Afolabi et al [100] presented a DoE-RSM method to investigate and optimize the combined effect of time and temperature (the "factors") on the hydrochar yield and HHV (the "responses") of spent coffee grounds. They adopted a faced-center central composite factorial design to fit the two responses with the two factors.…”

Section: Design Of Experiments: Response Surface Methodologymentioning

confidence: 99%

“…Response surface plot of the effects of temperature and time on hydrochar yield. Reprinted with permission from Afolabi et al[100]…”

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confidence: 99%

Hydrothermal Carbonization of Organic Waste and Biomass: A Review on Process, Reactor, and Plant Modeling

Ischia

Fiori

2020

Waste Biomass Valor

140

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Hydrothermal carbonization (HTC) is an emerging path to give a new life to organic waste and residual biomass. Fulfilling the principles of the circular economy, through HTC “unpleasant” organics can be transformed into useful materials and possibly energy carriers. The potential applications of HTC are tremendous and the recent literature is full of investigations. In this context, models capable to predict, simulate and optimize the HTC process, reactors, and plants are engineering tools that can significantly shift HTC research towards innovation by boosting the development of novel enterprises based on HTC technology. This review paper addresses such key-issue: where do we stand regarding the development of these tools? The literature presents many and simplified models to describe the reaction kinetics, some dealing with the process simulation, while few focused on the heart of an HTC system, the reactor. Statistical investigations and some life cycle assessment analyses also appear in the current state of the art. This work examines and analyzes these predicting tools, highlighting their potentialities and limits. Overall, the current models suffer from many aspects, from the lack of data to the intrinsic complexity of HTC reactions and HTC systems. Therefore, the emphasis is given to what is still necessary to make the HTC process duly simulated and therefore implementable on an industrial scale with sufficient predictive margins. Graphic Abstract

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“…Hydrothermal carbonization is a thermochemical technology that carries out biomass conversion in an aqueous inert environment under high pressure, with residence time being in the form of hours to days (Afolabi et al 2020;Malghani et al 2013;Sharma et al 2019). Generally, hydrothermal carbonization can be categorized into low temperature, carried out below 300 °C and high temperature, carried out in the range of 300-800 °C.…”

Section: Hydrothermal Carbonizationmentioning

confidence: 99%

“…According to the European biochar certificate, chars produced via hydrothermal carbonization are not classified as biochar (EBC 2012). Hydrothermal carbonization may be more suitable for producing biocarbon for energy production, since the chars produced possess superior characteristics in terms of low ash content and high calorific value (Afolabi et al 2020).…”

Section: Hydrothermal Carbonizationmentioning

confidence: 99%

Industrial biochar systems for atmospheric carbon removal: a review

et al. 2021

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In the context of climate change, there is an urgent need for rapid and efficient methods to capture and sequester carbon from the atmosphere. For instance, production, use and storage of biochar are highly carbon negative, resulting in an estimated sequestration of 0.3–2 Gt CO2 year−1 by 2050. Yet, biochar production requires more knowledge on feedstocks, thermochemical conversion and end applications. Herein, we review the design and development of biochar systems, and we investigate the carbon removal industry. Carbon removal efforts are currently promoted via the voluntary market. The major commercialized technologies for offering atmospheric carbon removal are forestation, direct air carbon capture utilization and storage, soil carbon sequestration, wooden building elements and biochar, with corresponding fees ranging from 10 to 895 GBP (British pounds) per ton CO2. Biochar fees range from 52 to 131 GBP per ton CO2, which indicates that biochar production is a realistic strategy that can be deployed at large scale. Carbon removal services via biochar are currently offered through robust marketplaces that require extensive certification, verification and monitoring, which adds an element of credibility and authenticity. Biochar eligibility is highly dependent on the type of feedstock utilized and processing conditions employed. Process optimization is imperative to produce an end product that meets application-specific requirements, environmental regulations and achieve ultimate stability for carbon sequestration purposes.

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Optimisation and characterisation of hydrochar production from spent coffee grounds by hydrothermal carbonisation

Cited by 123 publications

References 57 publications

Extraction of polyphenols and synthesis of new activated carbon from spent coffee grounds

Extraction of polyphenols and synthesis of new activated carbon from spent coffee grounds

Hydrothermal Carbonization of Organic Waste and Biomass: A Review on Process, Reactor, and Plant Modeling

Industrial biochar systems for atmospheric carbon removal: a review

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