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Energy and Nutrient Recovery by Hydrothermal Treatments
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Energy and Nutrient Recovery by Hydrothermal Treatments

A special issue of Resources (ISSN 2079-9276).

Deadline for manuscript submissions: closed (31 October 2023) | Viewed by 14750

Special Issue Editors

Prof. Dr. Angel F. Mohedano

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Guest Editor
Department of Chemical Engineering, Autonomous University of Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
Interests: waste management; waste to energy; hydrothermal treatments; wastewater treatment; anaerobic digestion; advanced oxidation processes; environmental catalysis
Prof. Dr. Elena Diaz

E-Mail Website
Guest Editor
Department of Chemical Engineering, Autonomous University of Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
Interests: waste management; waste to energy; hydrothermal treatments; wastewater treatment; advanced oxidation processes; environmental catalysis
Prof. Dr. M. Angeles de la Rubia

E-Mail Website
Guest Editor
Department of Chemical Engineering, Autonomous University of Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
Interests: waste management; waste to energy; hydrothermal treatments; wastewater treatment; anaerobic digestion

Special Issue Information

Dear Colleagues,

Hydrothermal processing of biowaste has been recently recognized as a promising technology to efficiently reduce waste volume, recover bioenergy and nutrients, destroy organic contaminants, and eliminate pathogens. This Special Issue is focused on all of the technologies that are able to carry out nutrient and energy recovery from any kind of waste (animal manure, municipal waste, organic waste from the industrial food sector, sewage sludge, green waste, among others). Particular emphasis is placed on to those technologies that are currently at a high technological readiness level, thereby including their applicability through techno-economical and life cycle analysis.

Prof. Dr. Angel F. Mohedano
Prof. Dr. Elena Diaz
Prof. Dr. M. Angeles de la Rubia
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Resources is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • waste management
  • waste to energy
  • hydrothermal treatments
  • anaerobic digestion
  • dark fermentation
  • circular economy

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Published Papers (4 papers)

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Research

14 pages, 3023 KiB  
Article
Preparation of Adsorbent Materials from Rice Husk via Hydrothermal Carbonization: Optimization of Operating Conditions and Alkali Activation
by Jhosué Naranjo, Evelyn Juiña, Carlos Loyo, Michelle Romero, Karla Vizuete, Alexis Debut, Sebastian Ponce and Herman A. Murillo
Resources 2023, 12(12), 145; https://doi.org/10.3390/resources12120145 - 12 Dec 2023
Cited by 8 | Viewed by 3348
Abstract
Hydrothermal carbonization (HTC) of rice husk was optimized in terms of the adsorption capacity at equilibrium (qe) and hydrochar mass yield (MY). The studied variables were reaction temperature, residence time, and biomass-to-water ratio by means of response surface methodology. In both [...] Read more.
Hydrothermal carbonization (HTC) of rice husk was optimized in terms of the adsorption capacity at equilibrium (qe) and hydrochar mass yield (MY). The studied variables were reaction temperature, residence time, and biomass-to-water ratio by means of response surface methodology. In both cases, reaction temperature resulted the most significant parameter promoting high qe values at higher temperatures when treating methylene blue (MB) as the target pollutant. Nevertheless, MY was low (~40%) when focusing on a possible industrial application. Hence, maximizing qe and MY simultaneously by optimization of multiple responses emerges as a promising solution to improve MY values (>60%) with no significant differences regarding the qe response. Furthermore, additional activation was conducted on optimal hydrochars to further investigate the enhancement of qe. As a result, no statistical differences between non-modified and activated hydrochars were observed for qe; however, the pseudo-second-order constant (k2) seemed to be increased after alkali activation, mainly due to a larger surface area. Non-modified and activated hydrochars were characterized via SEM, FTIR, XRD, and BET, resulting in two significant effects contributing to MB adsorption: increased surface area and functionalized hydrochar surface. Consequently, this work provides valuable insights on subsequent application of this HTC optimization scheme at an industrial scale. Full article
(This article belongs to the Special Issue Energy and Nutrient Recovery by Hydrothermal Treatments)
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14 pages, 4073 KiB  
Article
Co-Hydrothermal Carbonization of Grass and Olive Stone as a Means to Lower Water Input to HTC
by Rocío García-Morato, Silvia Román, Beatriz Ledesma and Charles Coronella
Resources 2023, 12(7), 85; https://doi.org/10.3390/resources12070085 - 21 Jul 2023
Cited by 7 | Viewed by 1974
Abstract
One drawback of biomass hydrothermal treatment (HTC) is the need of a water supply, which is especially important in the case of lignocellulosic biomass. This study has investigated the synergy resulting from co-HTC of two residual biomass materials that significantly differ in their [...] Read more.
One drawback of biomass hydrothermal treatment (HTC) is the need of a water supply, which is especially important in the case of lignocellulosic biomass. This study has investigated the synergy resulting from co-HTC of two residual biomass materials that significantly differ in their physico-chemical compositions: (a) olive stone, OS, a hard and high-quality biomass, with low N content, whose potential to give a high heating value briquette by HTC has been proven, and (b) fresh grass pruning, GP, as it is gathered from gardens, with a high water content, moderate N fraction, and low calorific value. The work specifically focuses on the water saving that can be attained when the liquid product produced by one of them (grass, with 80% of moisture) can supply part of the water needed by the other (olive stone) when both are subjected to HTC simultaneously. It was found that, when instead of water, an additional amount of fresh GP is added (in particular 40 out of 110 g of water was provided by 54 g of GP), and a more basic processing water is obtained (pH of co-HTC increased by 40%, in relation of single OS processes). This in turn did not have a remarkable effect on OS final SY at any of the two temperatures studied (200 and 220 °C), not on the C densification. Other features such as N content of resulting OS hydrochars showed a rise in the case of hybrid processes, from 0.2% to 3.3%. Other features that were affected on OS HTC products because of the presence of the GP in co-HTC were the HC surface structure, hydrophobicity, and the presence of surface functionalities and their thermal stability towards pyrolysis; processing water also showed changes on mineral content when both biomasses there blended. Proving that a biomass like OS can be hydrothermally treated by a hybrid process involving less water, without being detrimental in terms of final SY and energy densification, can open a field of research aimed to make HTC processes more efficient in terms of hydric balance. Full article
(This article belongs to the Special Issue Energy and Nutrient Recovery by Hydrothermal Treatments)
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20 pages, 8073 KiB  
Article
Fluoride Removal from Aqueous Medium Using Biochar Produced from Coffee Ground
by Hellem Victoria Ribeiro dos Santos, Paulo Sérgio Scalize, Francisco Javier Cuba Teran and Renata Medici Frayne Cuba
Resources 2023, 12(7), 84; https://doi.org/10.3390/resources12070084 - 17 Jul 2023
Cited by 11 | Viewed by 3506
Abstract
Low concentrations of fluoride (F−) in drinking water are beneficial for oral health, but the natural occurrence of high F− content has been reported in various groundwater sources, posing a continuous ingestion threat to humans. The utilization of biochar (BC) [...] Read more.
Low concentrations of fluoride (F−) in drinking water are beneficial for oral health, but the natural occurrence of high F− content has been reported in various groundwater sources, posing a continuous ingestion threat to humans. The utilization of biochar (BC) produced from residual biomass has emerged as a technically, economically, and environmentally sustainable alternative for fluoride removal through adsorption. Therefore, this study aimed to investigate the physicochemical characteristics of BC derived from coffee grounds and the influence of various factors on the adsorption process of F− in aqueous media, including pH, adsorbent dosage, contact time, temperature, and initial F− concentration. The BC exhibited a surface area of 12.94 m2·g−1 and a pore volume of 0.0349 cm3·g−1. The adsorption process was strongly pH dependent, demonstrating a significant decline in performance as pH increased from 2.0 onwards. The majority of F− removal occurred within the first 5 min, reaching adsorption equilibrium after 1 h of testing, regardless of the initial F− concentration employed. The data fitting to the Webber–Morris model indicated a two-step adsorption process on BC, with the first step being external surface sorption and the second step being intra-articular diffusion. The process was determined to be endergonic, and the data satisfactorily matched both the Freundlich and Langmuir models, with a qm of 0.53 mg·L−1 (T = 55 °C), indicating the predominance of physisorption. The findings suggest the potential of coffee grounds for BC production; nevertheless, surface structure modifications are necessary to enhance F− affinity and subsequently improve adsorption capacity. Full article
(This article belongs to the Special Issue Energy and Nutrient Recovery by Hydrothermal Treatments)
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13 pages, 1400 KiB  
Article
Activated Carbons from Hydrothermal Carbonization and Chemical Activation of Olive Stones: Application in Sulfamethoxazole Adsorption
by Elena Diaz, Ines Sanchis, Charles J. Coronella and Angel F. Mohedano
Resources 2022, 11(5), 43; https://doi.org/10.3390/resources11050043 - 28 Apr 2022
Cited by 22 | Viewed by 4611
Abstract
This work focuses on the production of activated carbons by hydrothermal carbonization of olive stones at 220 °C, followed by chemical activation with KOH, FeCl3 and H3PO4 of the hydrochar obtained. In addition, N-doped hydrochars were also obtained by [...] Read more.
This work focuses on the production of activated carbons by hydrothermal carbonization of olive stones at 220 °C, followed by chemical activation with KOH, FeCl3 and H3PO4 of the hydrochar obtained. In addition, N-doped hydrochars were also obtained by performing the hydrothermal carbonization process with the addition of (NH4)2SO4. All hydrochars, N-doped and non-doped, showed low BET surface areas (4–18 m2 g−1). Activated hydrochars prepared using H3PO4 or KOH as activating agents presented BET surface areas of 1115 and 2122 m2 g−1, respectively, and those prepared from N-doped hydrochar showed BET surface area values between 1116 and 2048 m2 g−1 with an important contribution of mesoporosity (0.55–1.24 cm3 g−1). The preparation procedure also derived inactivated hydrochars with predominantly acidic or basic groups on their surface. The resulting materials were tested in the adsorption of sulfamethoxazole in water. The adsorption capacity depended on both the porous texture and the electrostatic interactions between the adsorbent and the adsorbate. The adsorption equilibrium data (20 °C) fitted fairly well to the Langmuir equation, and even better to the Freundlich equation, resulting in the non-doped hydrochar activated with the KOH as the best adsorbent. Full article
(This article belongs to the Special Issue Energy and Nutrient Recovery by Hydrothermal Treatments)
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