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Hydrothermal carbonization (HTC) of dairy manure digestate (DMD) was explored in this study. Response surface methodology was used to investigate the influence of temperature, time, and DMD pH on hydrochar properties. Hydrochar obtained in the study exhibited higher heating value (HHV) in the range of 17.5–20.6 MJ kg−1, with energy and hydrochar yields 45.8–72.4% and 57.6–80.1%, respectively. It was demonstrated that temperature was the most significant factor. At higher temperature, the HHV of hydrochar was higher while both energy and hydrochar yields were lower. In particular, hydrochar obtained at temperature ≥ 260 °C had HHV ≥ 20.0 MJ kg−1, which was close to that of lignite and implied its potential as fuel. To gain insights about the fate of various elements during HTC and facilitate overall evaluation of hydrochar, a wide range of elements (30 in total, including macro- and micro-nutrients, as well as heavy metals) was analyzed. Hydrochar had carbon to nitrogen (C/N) ratio between 10 and 12, which was in the suitable range for nutrient availability as soil amendment. Half of the elements remained in the hydrochar, while most of Na, K, and half of S leached into process water, especially at temperature ≥ 260 °C, thus combusting hydrochar can potentially alleviate the slagging and fouling problems associated with direct combustion of dried DMD. The study provided insights for further rational utilization of DMD hydrochar, and integration of HTC into existing on-farm anaerobic digestion was a promising option for reduction disposal of DMD. [ABSTRACT FROM AUTHOR]

This study explores the hydrothermal carbonization (HTC) process applied to the exhausted chestnut produced by the tannin extraction industry, utilizing process water recirculation to enhance the efficiency and sustainability of the conversion process. Tannin extraction from wood typically involves hot water treatment, leaving behind residual wood biomass known as exhausted wood. These by-products maintain their renewable properties because they have only been exposed to hot water under a high pressure, which is unlikely to cause major alterations in their structural components. Hydrothermal treatment was carried out at temperatures of 220 °C and 270 °C for 1 h, with process water being recirculated four times. This investigation focused on analyzing the effects of recirculation on the yield and fuel properties of hydrochar, as well as characterizing the combustion behavior of the obtained hydrochar. The results indicated that recirculation of process water led to improvements in both the mass and energy yields of hydrochar. The mass yield of the hydrochar samples increased by 5–6%, and the ERE of the hydrochar samples increased by 5–8% compared to the HTC reference sample. However, alterations in the combustion characteristics were observed, including decreases in ignition temperature and combustion reactivity. The results indicate that, with PW recirculations, the combustion index decreased by about 14% and 18% for 220 °C and 270 °C, respectively. Overall, this research demonstrates the potential of utilizing HTC on chestnut tannin residue with process water recirculation to produce stable solid fuel and provides insights into the combustion behavior of the resulting hydrochar. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonization (HTC) has emerged as a pivotal technology in the battle against climate change and fosters circular economies. Operating within a unique reaction environment characterized by water as a solvent and moderate temperatures at self-generated pressures, HTC efficiently converts biomass residues into valuable bio-based products. Despite HTC's potential—from the management of challenging biomass wastes to the synthesis of advanced carbons and the implementation of biorefineries—it encounters hurdles transitioning from academic exploration to industrial implementation. Gaps persist, from a general comprehension of reaction intricacies to the difficulty of large-scale integration with wastewater treatments, to the management of process water, to the absence of standardized assessment techniques for HTC products. Addressing these challenges demands collaboration to bridge the many scientific sectors touched by HTC. Thus, this article reviews the current state of some hot topics considered crucial for HTC development: It emphasizes the role of HTC as a cornerstone for waste management and biorefineries, highlighting potentialities and challenges for its development. In particular, it surveys fundamental research aspects, delving into reaction pathways, predictive models, analytical techniques, and HTC modifications while exploring HTC's crucial technological applications and challenges, with a peculiar focus on combined HTC, wastewater integration, and plant energy efficiency. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonization (HTC) of wetland plant could achieve the recovery of phosphorus (P) via the production of P-enriched hydrochar to alleviate the crisis of phosphate resources, while the migration and transformation of P should be determined. In this study, Canna indica was derived into hydrochar through HTC at different temperatures (200°C-260°C) and liquid mediums (H2O, CaCl2, and NaOH). The P forms were systematically characterized using P K-edge X-ray absorption near edge structure (XANES), 31P liquid nuclear magnetic resonance (NMR), and sequential extraction. The total P content in hydrochar was up to 23 mg g−1 with mainly inorganic P (> 97.8%), and the recovery rate was almost 100% during NaOH-mediated HTC. The P species, monoester-P and soluble orthophosphate (ortho-P), in biomass were transformed to more stable ortho-P in hydrochars, which was highly dependent on temperature and liquid medium. With increasing temperature, Al/Mg-P was gradually replaced by Ca/Fe-P. The CaCl2 solution facilitated the transformation of Ca(H2PO4)2 into CaHPO4 by elevating the Ca/P ratio. While for the NaOH-mediated HTC, the CaHPO4 and Ca(H2PO4)2 were transformed to hydroxyapatite (74.3%-81.5%), and the proportion of MgHPO4 elevated with increasing temperature. The diffusive gradients in thin films (DGT) results implied that the addition of hydrochar greatly elevated the soil available P content, which was further promoted by high temperature and NaOH medium. These results indicate that the species and availability of P in hydrochar could be adjusted through varying liquid medium and reaction temperature, which provide guidance for the target design of P-enriched hydrochar and P reclamation. Highlight: • P-enriched hydrochar was prepared from the wetland plant by the modified HTC. • Liquid medium and reaction temperature affected the speciation dynamics of P. • P was stabilized with high temperature, Ca2+ addition, and alkaline liquid medium. • Hydrochar addition greatly elevated the soil available P content via DGT analysis. [ABSTRACT FROM AUTHOR]

Limited information is available about potential physicochemical changes that can occur in hydrochar post-production, e.g. during drying and storage. Understanding these changes is crucial not just for shaping future research plans, but also for future practical applications. Here we studied the effect of moisture (69.2% and 2.4%) and three storage temperatures (− 18, 4, and 20 °C) over a year on selected organic and inorganic compounds in hydrochar produced from the Hydrothermal carbonization (HTC) of digested cow manure. Comparison of the control wet hydrochars (WHs) and dry hydrochars (DHs) showed changes in organic compound composition due to drying. Overall, the total amount of the selected organic compounds was notably greater in WH (15.2 g kg−1 DM) compared to DH (11.8 g kg−1 DM), with variations observed in individual compound concentrations. Drying, however, had no significant influence on the identified inorganic compounds. Storage caused significant changes in both WH and DH, particularly in organic compounds after 12 weeks. Sugars (2–sevenfold), acids (36–371%), and aromatics (58–120%) in stored samples at week 52 were significantly higher than their control values. Changes in the inorganic elements (e.g., Co, K, Mg, Mn, P, S, Sr, and Zn) occurred faster in WH, with significant differences starting from week 1 compared to their control values, while DH showed fewer changes. Based on these changes in both organic and inorganic content, we recommend the optimal storage conditions for future HTC studies to preserve hydrochar properties. Finally, we discussed potential applications for stored hydrochars, with DH showing greater stability, especially at − 18 °C, making it suitable for various applications. Highlights: Drying of hydrochar and storage time affected concentrations of acids, aromatics, and sugars significantly Changes were observed at all storage temperatures—dried hydrochar stored at − 18 °C exhibited higher stability. Recommended storage conditions could be used for upcoming HTC research and hydrochar applications. [ABSTRACT FROM AUTHOR]

Silicon doped with boron is the most widely used material in modern microelectronic devices based on p-Si. Therefore, it is important to thoroughly understand boron's role in the processes of defect-impurity interaction in Si both on growing the material and during operation of devices. In this work, interactions of boron with oxygen in Si are investigated by studying boron absorption intracenter transitions, which are known to be highly sensitive to the local environment. In boron-doped Si, two lines with maxima at 228 and 261.3 cm−1 were detected. The linear dependence of lines intensity on boron concentration and the quadratic on oxygen content testifies that the defect responsible for the lines can be identified as BsO2i. The observed absorption lines correspond to the transitions from the ground to the excited states of boron, which are shifted toward lower frequencies relative to the main transitions due to a deformation perturbation from neighboring oxygen atoms. The activation energy of annealing and ionization energy of defect are determined. The properties of the registered ВsO2i defect differ from the known ВsO2 associated with the light-induced degradation of solar cells by local configuration. The data obtained testify that the ВsO2i defects with different properties can be formed in Si and must be taken into account when developing Si:B-based devices because they can play an important role in charge carrier transfer and affect the electrical and optical parameters of the material. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonization (HTC) was employed to convert cannabis waste into valuable solid fuel (hydrochar) under different operating conditions, including reaction temperature (170–230 °C), biomass-water ratio (1:10–1:20), and residence time of 60 min. The produced hydrochar was examined for their fuel properties including calorific value (HHV), proximate and ultimate analysis, thermal stability and combustion behavior, etc. The results revealed higher HTC temperature led to a higher degree of carbonization, which is beneficial for increasing carbon content and HHV of the hydrochar. The HHV of the hydrochar improved significantly up to 24.65 MJ/kg after the HTC compared to 17.50 MJ/kg for cannabis waste. The energy yield of hydrochar from the HTC process was in a range of 70.41–82.23%. The optimal HTC condition was observed at 230 °C and a biomass-water ratio of 1:10, producing high-quality hydrochar with 24.24 MJ/kg HHV and 72.28% energy yield. The hydrochar had similar fuel characteristics to lignite coal with significantly lower ash content. Additionally, recirculation of liquid effluent showed a positive influence on the HHV of hydrochar besides minimizing the release of wastewater from the HTC process. The study revealed that HTC is a promising technique for valorization of cannabis waste into high-value solid fuel, which can be potentially an alternative to coal. [ABSTRACT FROM AUTHOR]

Activated carbons (ACs) were developed from palm petiole via a new eco-friendly method composed of highly diluted H2SO4 hydrothermal carbonization and low-concentration KOH-activating pyrolysis followed by gamma-induced surface modification under NaNO3 oxidizing environment. The prepared graphitic carbons were subsequently used as an active material for supercapacitor electrodes. The physiochemical properties of the ACs were characterized using field emission scanning electron microscope–energy dispersive X-ray spectroscopy, N2 adsorption/desorption isotherms with Brunauer–Emmett–Teller surface area analysis, Fourier transform infrared spectroscopy, X-ray diffraction and Raman spectroscopy. The electrochemical performance of the fabricated electrodes was investigated by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. Even treated with extremely low H2SO4 concentration and small KOH:hydrochar ratio, the maximum SBET of 1365 m2 g−1 for an AC was obtained after gamma irradiation. This was attributed to radiation-induced interconnected network formation generating micropores within the material structure. The supercapacitor electrodes exhibited electric double-layer capacitance giving the highest specific capacitance of 309 F g−1 as well as excellent cycle stability within 10,000 cycles. The promising results strongly ensure high possibility of the eco-friendly method application in supercapacitor material production. [ABSTRACT FROM AUTHOR]

The present study investigates the use of hydrothermal carbonization (HTC) to upgrade agro-waste into solid biofuels and the use of citric acid (CA) as a catalyst capable of enhancing energy properties of hydrochars. HTC of pineapple waste (PA) was carried out at 180, 220, and 250 °C at a fixed 1-h residence time with and without the addition of CA. Contrarily to the current understanding with regard to the use of an acid catalyst during HTC, CA addition shows to appreciably increase hydrochar mass yields with HTC temperature, while increasing their degree of coalification and carbon retention. PA hydrochars produced with the addition of CA exhibit higher heating values (HHV) up to 29.7 MJ/kg dry basis (db), low residual ash (between 0.53 and 0.75 wt% db), and better combustion properties when compared to those of hydrochars obtained without CA addition. We show that the increase in mass yields and energy properties observed for hydrochars is due to CA catalytic effect toward back-polymerization of organics in the liquid phase to form secondary char. Secondary char formation and its role in influencing the hydrochar properties as solid biofuels are demonstrated by scanning electron microscopy, proximate, elemental analysis, and combustion reactivity. [ABSTRACT FROM AUTHOR]

The valorization of food waste (FW) in municipal solid waste is a challenging task. Hydrothermal treatment (HTT) is a promising method to produce carbon-rich materials from biomass, including humus substances. In this research, FW containing cellulose, starches, and proteins was treated by HTT with different feedwater pH values (pH 1, 4, 7, 10, 13) to study the regulation of three kinds of humus (i.e., humin, humic acids [HAs], and fulvic acids [FAs]) and nutrient (N and P). The pH values were adjusted by HCl and KOH (1, 4, 7, 10, 13). Three kinds of humus were quantified and N and P were semi-quantified by XPS. Optimal settings of temperature (200 °C) and pH values (13) for production of HAs and absorbable N and P were determined based on HAs yield (19.90%), protein-N (PN) and inorganic phosphorus. In addition, different forms of nitrogen and phosphorus in the water phase were accurately measured and PN was almost completely hydrolyzed with acid. Formation and regulation of humin, HAs, FAs and different form of N/P was discussed according to the FTIR, GC–MS and XPS analyses. [ABSTRACT FROM AUTHOR]

To investigate the influence of carbonization process parameters on the characteristics of municipal sludge carbonization products, this study selected carbonization temperatures of 300-700 °C and carbonization times of 0.5-1.5 h to carbonize municipal sludge. The results showed that with an increase in temperature and carbonization time, the sludge was carbonized more completely, and the structure and performance characteristics of the sludge changed significantly. Organic matter was continuously cracked, the amorphous nature of the material was reduced, its morphology was transformed into an increasing number of regular crystalline structures, and the content of carbon continued to decrease, from the initial 52.85 to 38.77%, while the content of inorganic species consisting continued to increase. The conductivity was reduced by 87.8%, and the degree of conversion of salt ions into their residual and insoluble states was significant. Natural water absorption in the sludge decreased from 8.13 to 1.29%, and hydrophobicity increased. The dry-basis higher calorific value decreased from 8,703 to 3,574 kJ/kg. Heavy metals were concentrated by a factor of 2-3, but the content of the available state was very low. The results of this study provide important technological support for the selection of suitable carbonization process conditions and for resource utilization., Competing Interests: The authors declare there is no conflict., (© 2024 The Authors This is an Open Access article distributed under the terms of the Creative Commons Attribution Licence (CC BY-NC-ND 4.0), which permits copying and redistribution for non-commercial purposes with no derivatives, provided the original work is properly cited (http://creativecommons.org/licenses/by-nc-nd/4.0/).)

Hydrothermal carbonization (HTC) is a promising technique to convert biomass into valuable solid fuels. In this work, cellulose- and wood-derived hydrochars were synthesized under hydrothermal carbonization conditions with different temperatures (200–250 °C) and reaction times (6 h or 12 h). The content of fixed carbon in the cellulose-derived hydrochar is higher than that of the wood-derived hydrochar. Moreover, cellulose can be carbonized more easily during the HTC reaction than wood. O/C and H/C ratios of all hydrochars were similar to those of lignite and decreased with increasing reaction temperature. The composition of solids recovered after 12 h is similar at all temperatures, consisting primarily of sp2 carbons (furanic and aromatic groups) and alkyl groups. When a large amount of metal is introduced, except for part of the zinc combined with the energetic group, the remaining part will condense on the surface of the sample as zinc ions. [ABSTRACT FROM AUTHOR]

Biorefineries have been profiled as potential alternatives to increase biomass use at the industrial level. However, more efforts are required to improve the sustainability of these facilities through process improvement and product portfolio increase. The catalytic conversion of biomass to chemicals and energy vectors is one of the most studied research lines today. The open literature has described catalytic pathways for producing biofuels and platform molecules using this renewable resource. Nevertheless, few literature reviews have aimed to analyze the role of the catalytic conversion of biomass in biorefineries while considering the following items: (i) biocatalysis, (ii) carbon dioxide conversion, (iii) design based on catalytic biomass upgrading, and (iv) sustainability metrics. This paper reviews several processes where catalysis has been applied to improve yields and conversion to elucidate the potential of this research field to boost biomass implementation in different productive sectors. This paper provides an overview of the catalytic conversion of biomass into a series of biofuels and high-value-added products, involving key topics related to catalyst performance, use, applications, and recent trends. In addition, several research gaps and ideas are highlighted based on previous studies. In conclusion, the catalytic conversion of biomass has the potential to increase biorefineries' sustainability. Nevertheless, more studies focused on (i) the production of new catalysts using renewable resources, (ii) the techno-economic and environmental assessment of processes involving catalysis, and (iii) the influence of involving biomass valorization via heterogeneous catalysis in existing facilities are required to obtain a real understanding of catalytic upgrades' benefits. [ABSTRACT FROM AUTHOR]

Hydrochar derived from hydrothermal carbonization (HTC) has been recognized as a potential absorbent and horticultural substrate. However, its practical application has been limited due to its low adsorption capacity and negative effects on plant growth. To address these issues, three pre-treatment methods (water washing, microbial aging, and freezing-thawing aging) were employed to further improve the physical structure and chemical properties of hydrochar. A seed germination test with kale (Brassica oleracea var. acephala D.C) was conducted to evaluate the phytotoxicity of modified hydrochars. The results showed that microbial aging considerably enhanced the physicochemical properties of the hydrochar. Specifically, under microbial aging, the bulk density of microbial-aged hydrochar (MHC) decreased by 8.1%, the porosity increased by 24.8%, and the water-holding capacity increased by 36.54% compared to fresh hydrochar (FHC). Moreover, the surfaces of MHC and freezing-thawing aged hydrochar (FTHC) were observed with rough and cracked surfaces and macro pore structures. Fourier transform infrared (FTIR) spectroscopy revealed that the functional group's intensities of the four hydrochar materials varied, and that MHC and FTHC had more oxygen-containing groups than the others. Additionally, the surface areas of MHC and FTHC increased by 318.64% and 238.98% compared to FHC, respectively. The seed germination test indicated the strong inhibitory effect of FHC, while MHC significantly (p < 0.05) improved the seed germination rate and root development. These findings suggest that among the different pre-treatment methods, microbial aging demonstrated the greatest potential for practical application in improving the physicochemical properties of hydrochar and promoting seed germination. This study opens up new avenues for further research on improving hydrochar and suggests that future studies should focus on optimizing the aging process. [ABSTRACT FROM AUTHOR]

Hydrothermal processing of biomass may be able to overcome a series of problems associated with the thermochemical conversion of lignocellulosic material into energy and fuels. Investigating the process parameters and an adequate process description is one of the first steps to being able to design and optimize a certain treatment concept. In the present article, we studied process evolution with respect to reaction time in order to evaluate structure changes and kinetics of corn stover decomposition in a hydrothermal reactor. The effect of the biomass-to-H2O ratio was also investigated. A pilot-scale reactor of 18.75 L was used to conduct hydrothermal processing runs at 250 °C at different reaction times (60, 120 and 240 min) and biomass-to-H2O ratios (1:10, 1:15 and 1:20). Solid phase products were characterized by thermogravimetry (TG), scanning electron microscopy (SEM), elemental composition (EDX), crystalline phases by X-ray diffraction (XRD) and surface area (BET). For the experiments with a constant reaction time, the yields of hydro-char, aqueous and gaseous phases varied between 31.08 and 35.82% (wt.), 54.59 and 60.83% (wt.) and 8.08 and 9.58% (wt.), respectively. The yields of hydro-char and gases tend to increase with higher biomass-to-H2O ratios, while aqueous phase yields are lower when using lower ratios. As expected, the yields of liquid and gases are higher when using higher reaction times, but there is a reduction in hydro-char yields. TG showed that 60 min was not enough to completely degrade the corn stover, while 120 and 240 min presented similar results, indicating an optimized time of reaction between 120 and 240 min. SEM images, elemental composition and XRD of hydro-char showed that higher biomass-to-H2O ratios increase the carbonization of corn stover. The surface area analysis of hydro-char obtained at 250 °C, 2.0 °C/min, a biomass-to-H2O ratio of 1:10 and 240 min showed a surface area of 4.35 m2/g, a pore volume of 18.6 mm3/g and an average pore width of 17.08 μm. The kinetic of corn stover degradation or bio-char formation was correlated with a pseudo-first-order exponential model, exhibiting a root-mean-square error (r2) of 1.000, demonstrating that degradation kinetics of corn stover with hot-compressed H2O, expressed as hydro-char formation, is well described by an exponential decay kinetics. [ABSTRACT FROM AUTHOR]

This review comprehensively examines biochar, an essential material in an era of climate change for reducing carbon dioxide (CO2) emissions into the atmosphere. It is inconspicuous, black, lightweight, and very porous, and is produced through the thermal conversion of biomass. Our literature review highlights biochar's expansive application possibilities. Firstly, its potential to improve soil quality and sequester CO2 has been examined, as well as its utilization in iron and steel manufacturing to minimize the quantity of coke and ultimately reduce CO2 emissions. In industrial manufacturing, the complete elimination of coke can promote environmental neutrality, which is achieved using biochar from biomass for its extrusion. Furthermore, biochar is becoming increasingly significant in modern energy storage technologies and as an important additive in Pickering emulsions, which are also employed in energy storage systems. Additionally, the use of carbon black is a broad topic, and this review illustrates where it can be successfully utilized, especially in environmentally sensitive areas. [ABSTRACT FROM AUTHOR]

A key factor restricting the application of biochar in the steel industry is its high-quality upgrading. This paper evaluated the characteristics of hydrochar produced by HTC (hydrothermal carbonization) process of corncob to be used as a solid fuel. HTC temperatures (240-300 °C) and HTC water-reused times (1-3 times) were examined for their effects on hydrochar yield, physicochemical characteristics, and combustion properties. The results showed hydrochar yields, O/C, and H/C parameters decreased as HTC temperature and water-reused times increased, while its high heating value increased. Due to dehydration and decarboxylation, hydrochar showed similar characteristics to those in bituminous coal. The removal efficiency of alkali metal K reached 99% after HTC treatment. Carbonaceous hydrochar had become more compact, orderly, and stable with increasing amounts of aromatic functional groups, C = C, and C = O. Hydrochar, as a biofuel, has higher ignition energy and is more stable than corncob due to its high carbonaceous order degree. To calculate combustion kinetic parameters, the Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods were applied. The results revealed that E α (average activation energy) was quite similar between the two models. HC-300 had an E α of 262 kJ/mol. HTC could be an efficient way to reutilize corncob biomass into clean biofuels with high calorific value., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Hydrothermal carbonization (HTC) is the method of choice to convert wet waste biomass to hydrochars. Their porous structure can serve as a microenvironment to plant-growth-promoting rhizobacteria (PGPR), supporting their growth, survival, and activities. As published work lacks the systematic compilation of pore characteristics of hydrochars related to bacterial colonization, we collect available data and elaborate on their dependence on the carbonization process conditions, feedstocks, and methodology of pore system characterization. Our analysis indicates a high abundance of pores sized between 1 and 20 μm relevant for the protection of PGPR from predators, and of nutrients and labile C in hydrochars supporting bacterial growth. In addition to the selection of optimized process parameters and feedstocks (240–260 °C, low feedstock pH, non-lignocellulosic biomass), adding mineral amendments prior to HTC offers opportunities for engineering hydrochars with an even larger share of pore space suited for bacterial colonization. Using the comprehensive literature on biochars, we demonstrate that the interior pore space in chars determines the potential to serve as an inoculum carrier to PGPR, thereby enhancing nutrient acquisition and protecting plants from diseases and abiotic stresses. The pore characteristics of hydrochars are comparable to biochars, and hydrochars are generally superior in providing a labile C reservoir that PGPR can readily access. We argue that HTC provides a cost-effective conversion route to produce PGPR vectors/carriers from wet (waste) biomass serving various environmental management objectives (waste recycling, soil fertility, soil remediation technologies) and circular bioeconomy (sustainable agriculture, substituting non-renewable carrier materials and fertilizers). We review the role of pore characteristics of hydrochars for bacterial colonization We identify opportunities for engineering hydrochars to provide favorable habitat conditions to PGPR 240–260 °C, low pH, non-lignocellulosic feedstocks, and adding mineral amendments increase the habitable pore space Hydrochars offer suitable pore characteristics and high labile C amounts and are promising PGPR carriers/vectors [ABSTRACT FROM AUTHOR]

In today's world, due to population increase, there are many alarming and potential catastrophic problems like climate change, environmental pollution and an enormous mass of wastes constantly produced by humankind to find innovative solutions for the management, recycling, and valorization of biowaste from agricultural production, food processing, and organic household residues. The search for sustainable and efficient wastewater treatment technologies has gained scientific interest recently; particular focus is on using biowaste to produce hydrochars (HCs) via the hydrothermal carbonization (HTC) process used as adsorbent materials for dye, heavy metal, and emerging pollutant removal. HTC materials derived from renewable resources are an environmentally friendly and adequate way to adsorb pollutants such as organic and inorganic molecules from wastewaters. This review focuses on the advantages of the HTC process which lead to improved properties of the materials obtained, making them highly efficient in wastewater treatment. The information presented in this paper was derived from the most recent publications in the field. Future perspectives of HC materials should consider the possibilities of scale-up, pretreatment of biowastes, and the optimal parameters of the HTC process to produce HCs applied for pollutant removal from wastewaters. [ABSTRACT FROM AUTHOR]

BACKGROUND: Sugar cane bagasse (SB) is a by‐product of the sugar cane industry, and is obtained on a large scale. In this paper, SB was used as a source of carbon for preparing a magnetic carbon nanocomposite (MCN‐SB) through one‐step hydrothermal carbonisation (HTC), in the presence of iron (III) nitrate. By way of comparison, SB was replaced by glucose in HTC (MCN‐GLU), and a thermal treatment of this material was then performed under an N2 atmosphere (MCN‐GLU‐HT). The physical and chemical properties of the nanocomposites were assessed, and the magnetic samples were applied as adsorbents. RESULTS: MCN‐SB and MCN‐GLU are composed of iron oxide nanoparticles embedded in carbonaceous matrix which also contain oxygenated groups. The MCN‐SB sample was already magnetic after HTC, showing a magnetization saturation (Ms) of 5.0 emu g−1, due to the presence of magnetite, whereas MCN‐GLU consisted of hematite and required additional thermal treatment (HT) to acquire magnetic properties, with MCN‐GLU‐HT showing an Ms of 30.5 emu g−1. In turn, the mesoporous structure and higher specific surface area (SSA) of MCN‐GLU‐HT (SSA 90 m2 g−1) than MCN‐SB (SSA 53 m2 g−1) was a causative factor for its higher capacity of hexavalent chromium [Cr (VI)] removal (939 μg g−1), when compared to MCN‐SB (768 μg g−1), which has a nonporous structure. CONCLUSION: The results suggest that SB can be reused, by means of HTC, for the preparation of a magnetically recoverable adsorbent, showing good adsorption properties. © 2022 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Ferromagnetic insulators play a crucial role in the development of low‐dissipation quantum magnetic devices for spintronics. Epitaxial LaCoO3 thin film is a prominent ferromagnetic insulator, in which the robust ferromagnetic ordering emerges owing to epitaxial strain. Whereas it is evident that strong spin‐lattice coupling induces ferromagnetism, the reported ferromagnetic properties of epitaxially strained LaCoO3 thin films are highly consistent. For example, even under largely modulated degree of strain, the reported Curie temperatures of epitaxially strained LaCoO3 thin films lie in a narrow range of 80–85 K, without much deviation. In this study, substantial enhancement (≈18%) in the Curie temperature of epitaxial LaCoO3 thin films is demonstrated via crystallographic orientation dependence. By changing the crystallographic orientation of the films from (111) to (110), the crystal‐field energy is reduced and the charge transfer between the Co and O orbitals is enhanced. These modifications lead to a considerable enhancement of the ferromagnetic properties (including the Curie temperature and magnetization), despite the identical nominal degree of epitaxial strain. The findings of this study provide insights into facile tunability of ferromagnetic properties via structural symmetry control in LaCoO3. [ABSTRACT FROM AUTHOR]

This paper shows the results of hydrothermal carbonization of biomass from seven different crops used as biofuel: wheat straw, soybean straw, corn cob, corn stalk, sunflower stalk, walnut shell, and hazelnut shell. The hydrothermal carbonization process was investigated at 200 and 250°C reaction temperatures, a pressure of 8.0 MPa, and 120 minutes of process duration. The obtained dry hydrochar was characterized. The hydrothermal carbonization process increased carbon and decreased oxygen and, to a lesser extent, hydrogen. Higher heating value of hydrochar increased compared to the feedstock. The hydrothermal carbonization process influenced the increase in the share of ash and bulk density. At lower process temperature, a higher mass yield of hydrochar was obtained. The color of the hydrochar correlated with carbon content; lower process temperatures gave brown lignocellulosic color, and higher temperatures resulted in charcoal black. Depending on the raw material, hydrochar was improved in terms of its basic composition and heating value, and it showed to have the potential to be used in coal dust combustion plants. [ABSTRACT FROM AUTHOR]

Solid hydrochar (HC) produced by hydrothermal carbonization (HTC) of tomato plant biomass from a greenhouse (GH) was assessed for different inhouse applications, including fuel, seed germination, and leached GH nutrient feed (GNF) wastewater treatment. Completed experiments showed encouraging results. HC was revealed to be an efficient renewable fuel, having peat-like characteristics with high heating value of about 26.0 MJ/kg and very low clinker forming potential. This would allow the use of HC as fuel for GH heating as a substitute to costly natural gas, or it could be commercialized after pelletizing. Experiments with soil application showed substantial potential for the produced HC in better seed germination of tomato plants. Another benefit from use of the produced HC is as a soil additive, which would also contribute to environmental emission reduction. Results suggest that the generated HC can remove about 6–30% of nutrients from leached-GNF wastewater. This would be an essential treatment in the reduction of nutrients from leached water from GH operations, and thus could prevent/reduce eutrophication. The exhausted HC after treatment application could then be reused for soil remediation. Overall, the paper highlights the potential applications of hydrothermal treatment in valorization of low-valued GH TPB waste, resulting in a circular economy. [ABSTRACT FROM AUTHOR]

The integration of hydrothermal carbonisation (HTC) and anaerobic digestion (AD) can overcome some of the disadvantages of thermal or biological processing alone. This study aims to investigate integrated HTC-AD across a range of integration strategies and HTC processing temperatures (150 °C, 200 °C and 250 °C) to improve the energy conversion efficiency (ECE) of grass, compared to AD alone. The separation of hydrochars (HCs) for combustion and process waters (PWs) for digestion appears to be the most energetically feasible HTC-AD integration strategy, compared to HC or HTC-slurry AD. Hydrochars represent the greater energy carrier with between 81–85% of total energy output. The ECE of grass was improved from 51% to 97% (150 °C), 83% (200 °C) and 68% (250 °C) through integrated HTC-AD. Therefore, lower HTC processing temperatures yield more favourable energetics. However, higher HTC temperatures favour more desirable HC properties as a combustion fuel. The hydrochar produced at 250 °C (HC-250) displayed the highest HHV (25.8 MJ/kg) and fixed carbon: volatile matter ratio (0.47), as well as the greatest reduction in slagging and fouling potential (ash flow temperature > 1550 °C). Overall, integrated HTC-AD is an effective energy valorisation strategy for grass. A compromise exists between the quality of hydrochar and the energetic balance. However, at 250 °C the process remains energetically feasible (EROI = 2.63). [ABSTRACT FROM AUTHOR]

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In the present study, the olive stones (OS) filter bed used for the filtration of olive mill wastewater (OMWW), named OMWW/OS-FR, was converted via hydrothermal carbonization (HTC) into solid biofuel. HTC was operated at three different temperatures (180, 240, and 300 °C) and the chemical and combustible characteristics of the produced hydrochars were investigated. The hydrochars prepared at 240 and 300 °C HTC temperatures exhibited high carbon recovery (80.1–84.2%) and fixed carbon content (45.8–46.8%), reduced volatile matter concentration (49.9–52.2%), low hydrogen to carbon (H/C) and oxygen to carbon (O/C) ratios (0.91–0.98 and 0.18–0.22, respectively) and high heating value (29.7–31 MJ/kg). The characteristics of the HTC-hydrochars were compared to those of biochar prepared by low temperature pyrolysis (LTP) at 400 °C. The results highlighted the improved fuel properties of HTC-hydrochars as compared to those of LTP-biochar in term of energy yield and energy content; this indicates the adaptability of HTC for OMWW/OS-FR upgrading. The temperature of 240 °C was selected as the optimal HTC temperature for the production of hydrochar with enhanced biofuel properties and with lower energy consumption for the thermal treatment of the water contained in the OMWW/OS-FR. Consequently, the use of HTC at 240 °C instead of dry LTP allowed for an energy saving over 49%. Accordingly, it can be concluded that HTC, in term of energy consumption, is more appropriate than LTP to manage the moisture in the OMWW/OS-FR. [ABSTRACT FROM AUTHOR]

The replacement of traditional and non-renewable resources by shifting towards renewable-based strategies is a strategy implemented by the European Union for a circular economy-based society. Among the various methods to produce renewable biofuels, hydrothermal carbonization is promising in terms of waste management. This technology involves thermochemical treatment of wastes at lower emperatures than other common thermal treatments such as pyrolysis or gasification. Here we review hydrothermal carbonization for managing a wide variety of biomass–wastes and obtaining value-added products. Three types of products are obtained: gases, liquids and solids. The solid carbonized product is the main product, which can be used for many applications, highlighting its use as substitute for fossil coal. Nonetheless, actual commercial plants hardly reach profitability by considering only the solid products. Therefore, this review focus on the integration of other processes. For instance, anaerobic digestion, catalytic conversion of gaseous streams and membrane technology for liquid concentration appear as the most interesting options to valorize all the products generated during hydrothermal carbonization. [ABSTRACT FROM AUTHOR]

Malaysian oil palm industry produces a significant amount of oil palm residue as solid wastes. These solid wastes are comprised of oil palm residue which contains the stem, fronds from the farms, empty fruit bunch (EFB), mesocarp fibre (MF), and palm kernel shell (PKS) from the oil palm–processing factories. These residues are not successfully reused for other purposes, and the current dumping methods can possibly trigger unfavourable effects to the environment. As oil palm residues are a readily available waste biomass, it has a high potential to be converted into valuable energy-derived products. Hydrothermal carbonization (HTC), which is a thermochemical process, is a method used to treat biomass to produce hydrochar under hot-compressed water. Oil palm residues (palm leaves, palm fronds, and palm shell) were used as the feedstock for producing carbonaceous hydrochar. The key objective of this study is to examine the effect of the reaction temperature, residence time, and acid catalysts on the HTC process. HTC of oil palm residues was optimized at different operating temperatures from 140 to 300 °C and different reaction times between 30 and 240 minutes with a biomass-to-water ratio of 1:10 wt%. Acid catalysts such as citric acid and ascorbic acid were used for the HTC process. The hydrochar produced is further characterized using heating value and elemental and Fourier transform infrared (FTIR) analysis. The yield of hydrochar reduces with the rise of temperature and time but it increases in the presence of acid catalysts. The carbon content of hydrochar is observed to be between 44.36 and 49.50%. The FTIR analysis showed that a high intensity at 1423 cm−1 indicates a high content of lignin and cellulose in the hydrochar. A considerable decrease in the H/C and O/C atomic ratio shows that the dehydration and decarboxylation take place during the HTC process. [ABSTRACT FROM AUTHOR]

Activated carbons (ACs) were developed from palm petiole via a new eco-friendly method composed of highly diluted H 2 SO 4 hydrothermal carbonization and low-concentration KOH-activating pyrolysis followed by gamma-induced surface modification under NaNO 3 oxidizing environment. The prepared graphitic carbons were subsequently used as an active material for supercapacitor electrodes. The physiochemical properties of the ACs were characterized using field emission scanning electron microscope-energy dispersive X-ray spectroscopy, N 2 adsorption/desorption isotherms with Brunauer-Emmett-Teller surface area analysis, Fourier transform infrared spectroscopy, X-ray diffraction and Raman spectroscopy. The electrochemical performance of the fabricated electrodes was investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. Even treated with extremely low H 2 SO 4 concentration and small KOH:hydrochar ratio, the maximum S BET of 1365 m 2  g -1 for an AC was obtained after gamma irradiation. This was attributed to radiation-induced interconnected network formation generating micropores within the material structure. The supercapacitor electrodes exhibited electric double-layer capacitance giving the highest specific capacitance of 309 F g -1 as well as excellent cycle stability within 10,000 cycles. The promising results strongly ensure high possibility of the eco-friendly method application in supercapacitor material production., (© 2023. Springer Nature Limited.)

Featured Application: Hydrothermal carbonization process can be efficiently used for the simultaneous production of value-added chemicals, including furans and levulinates, and carbon-based materials. In this study, a simple and green protocol to obtain hydrochar and high-added value products, mainly 5-hydroxymethylfurfural (5-HMF), furfural (FU), levulinic acid (LA) and alkyl levulinates, by using the hydrothermal carbonization (HTC) of orange peel waste (OPW) is presented. Process variables, such as reaction temperature (180–300 °C), reaction time (60–300 min), biomass:water ratio and initial pH were investigated in order to find the optimum conditions that maximize both the yields of solid hydrochar and 5-HMF and levulinates in the bio-oil. Data obtained evidence that the highest yield of hydrochar is obtained at a 210 °C reaction temperature, 180 min residence time, 6/1 w/w orange peel waste to water ratio and a 3.6 initial pH. The bio-products distribution strongly depends on the applied reaction conditions. Overall, 180 °C was found to be the best reaction temperature that maximizes the production of furfural and 5-HMF in the presence of pure water as a reaction medium. [ABSTRACT FROM AUTHOR]

Hydrochar a carbon-rich material resulting from hydrothermal carbonization of biomass, has received substantial attention because of its potential application in various areas such as carbon sequestration, bioenergy production and environmental amelioration. A series of hydrochars were prepared by metal chloride-assisted hydrothermal carbonization of rice husk and characterized by elemental analysis, zeta potential, X-ray diffraction, Brunauer–Emmett–Teller measurements, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and scanning electron microscopy. The results reveal that the prepared hydrochars have carbon contents ranging from 45.01 to 58.71%, BET specific areas between 13.23 and 45.97 m2/g, and rich O-containing functional groups on the surfaces. The metal chlorides added in the feedwater could improve the degree of carbonization and show significant effects on the physical, chemical and adsorption properties of the hydrochars. The adsorption of the selected organics on the hydrochars is a spontaneous and physisorption-dominated process. The hydrochars possess larger adsorption capacities for 2-naphthol than for berberine hydrochloride and Congo red, and the modeling maximum adsorption capacities of 2-naphthol are in the range of 170.1–2680 mg/g. The adsorption equilibrium could be accomplished in 10, 40 and 30 min for 2-naphthol, berberine hydrochloride and Congo red, respectively. These results suggest metal chloride-assisted hydrothermal carbonization a promising method for converting biomass waste into effective adsorbents for wastewater treatment. [ABSTRACT FROM AUTHOR]

Pyrolysis (Pyr) and hydrothermal carbonization (HTC) of corn stalk (CS) catalyzed with sewage sludge salts were investigated as a comparison of two biomass refining processes to produce char. The influence of the following salt-catalysts (SC)- NH4H2PO4, KH2PO4, Na2HPO4, and CaCl2- on the higher heating value (HHV), char yield (CY), energy yield (EY), and energy densification (ED) as well as an elemental analysis (C, H, N, S, O) of the produced chars were determined. Besides, ATR–FTIR spectra were made from the resulting biochar (BC) and hydrochar (HC). For each processing method, two temperatures were set: HTC 180/210 °C and Pyr 400/500 °C. CS had an HHV of 19 MJ/kg, and the catalyst-free HC and BC came out with 22 MJ/kg. The NH4H2PO4-catalyst demonstrated the maximal efficiency in advancing the HHV for the HTC with 27 MJ/kg (23 MJ/kg for the Pyr), as the Mixed catalysts for the Pyr with 24 MJ/kg, the Pyr-BC increased 2–5 MJ/kg, and the HTC-HC 5–7 MJ/kg. The HC ended up with higher results compared with the BC: HHV 2–3 MJ/kg, CY and EY 5–10%, and ED 0.1–0.2. On the opposite BC marked a higher level of coalification than the HC, the BC came close to that of coal while the HC ranged in the area of peat. Both processing methods were improved by most SC and the Mixed catalysts. Especially the chars of the Mixed SC reached the same carbonization level at lower processing temperature. [ABSTRACT FROM AUTHOR]

To enhance the hydrothermal carbonization (HTC) process on biomass waste and improve the quality of biomass solid fuel. Corn straw was pretreated with acid washing and subsequently hydrothermally carbonized at 180–270 °C. The solid product obtained (hydrochars) was compared with the solid product produced from untreated hydrothermally carbonized straw. The results show that the acid pretreatment removed 7.9% of the ash from the straw. ICP and XRD analysis show that most of the alkali and alkaline earth metals have been removed. This addresses the defect of high ash content as the HTC temperature increases. The HHV of hydrochars produced by HTC after acid washing can reach 27.7 MJ/kg, which is nearly 10% higher than that of hydrochars prepared without acid washing pretreatment, and nearly 70% higher than that of straw raw materials. Elemental analysis and FTIR analysis show that the acid washing pretreatment changed the content and structure of the biomass components in the straw, resulting in a more complete HTC reaction and higher carbon sequestration. The decrease of H/C and O/C deepened the degree of coal-like transformation of hydrochars, with the lowest approaching the bituminous coal zone. The combustion characteristics of the hydrochars prepared after acid washing were significantly upgraded, the comprehensive combustion index and thermal stability of hydrochars both increased. Therefore, HTC after acid washing pretreatment is beneficial to further improve the high heating value and combustion characteristics of hydrochar. [ABSTRACT FROM AUTHOR]

In this work, the influence of temperature on textural, morphological, and crystalline characterization of bio-adsorbents produced by hydrothermal carbonization (HTC) of corn stover was systematically investigated. HTC was conducted at 175, 200, 225, and 250 °C, 240 min, heating rate of 2.0 °C/min, and biomass-to-H2O proportion of 1:10, using a reactor of 18.927 L. The textural, morphological, crystalline, and elemental characterization of hydro-chars was analyzed by TG/DTG/DTA, SEM, EDX, XRD, BET, and elemental analysis. With increasing process temperature, the carbon content increased and that of oxygen and hydrogen diminished, as indicated by elemental analysis (C, N, H, and S). TG/DTG analysis showed that higher temperatures favor the thermal stability of hydro-chars. The hydro-char obtained at 250 °C presented the highest thermal stability. SEM images of hydro-chars obtained at 175 and 200 °C indicated a rigid and well-organized fiber structure, demonstrating that temperature had almost no effect on the biomass structure. On the other hand, SEM images of hydro-chars obtained at 225 and 250 °C indicated that hydro-char structure consists of agglomerated micro-spheres and heterogeneous structures with nonuniform geometry (fragmentation), indicating that cellulose and hemi-cellulose were decomposed. EDX analysis showed that carbon content of hydro-chars increases and that of oxygen diminish, as process temperature increases. The diffractograms (XRD) identified the occurrence of peaks of higher intensity of graphite (C) as the temperature increased, as well as a decrease of peaks intensity for crystalline cellulose, demonstrating that higher temperatures favor the formation of crystalline-phase graphite (C). The BET analysis showed 4.35 m2/g surface area, pore volume of 0.0186 cm3/g, and average pore width of 17.08 μm. The solid phase product (bio-adsorbent) obtained by hydrothermal processing of corn stover at 250 °C, 240 min, and biomass/H2O proportion of 1:10, was activated chemically with 2.0 M NaOH and 2.0 M HCl solutions to investigate the adsorption of CH3COOH. The influence of initial acetic acid concentrations (1.0, 2.0, 3.0, and 4.0 mg/mL) was investigated. The kinetics of adsorption were investigated at different times (30, 60, 120, 240, 480, and 960 s). The adsorption isotherms showed that chemically activated hydro-chars were able to recover acetic acid from aqueous solutions. In addition, activation of hydro-char with NaOH was more effective than that with HCl. [ABSTRACT FROM AUTHOR]

A myriad of resources and efforts have been devoted to assessing the possibilities of using locally sourced biomass to produce energy, reduce CO2 emissions, and, in turn, lower dependance on petroleum. Grape pomace (GP) and walnut shells (WS) are organic waste generated in Chile. Within the last decade, the potential benefits and application of biomass have received significant attention, both in terms of producing functionalized carbon materials, and the various potential applications in the field of energy storage and environmental protection. The proposed research motivation is on the development of carbonous materials through thermal decomposition processes. Few researchers have addressed the idea of developing a multipurpose carbonaceous matrix from hydrochar, and there remains a need for an efficient method to obtain hydrochar specially from grape pomace. Hence, the general objective of this research is to study the potential of grape pomace and walnut shells treated with hydrothermal carbonization (HTC) as an alternative low-cost and efficient carbonous matrix. Proximate and elemental analysis was determined to distinguish the nature of the feedstock along with the hydrochar produced. Yield and reaction severity were also studied to study the impacts of temperature and residence time for both feedstocks. Successful results from the proposed work have broad applications for increasing the sustainability biomass applications, contributing to a positive economic impact. [ABSTRACT FROM AUTHOR]

This work aims to systematically investigate the influence of process temperature, biomass-to-water ratio, and production scales (laboratory and pilot) on the chemical composition of aqueous and gaseous phases and mass production of chemicals by hydrothermal processing of Açaí (Euterpe oleraceae, Mart.) seeds. The hydrothermal carbonization was carried out at 175, 200, 225, and 250 °C at 2 °C/min and a biomass-to-water ratio of 1:10; at 250 °C at 2 °C/min and biomass-to-water ratios of 1:10, 1:15, and 1:20 in technical scale; and at 200, 225, and 250 °C at 2 °C/min and a biomass-to-water ratio of 1:10 in laboratory scale. The elemental composition (C, H, N, S) in the solid phase was determined to compute the HHV. The chemical composition of the aqueous phase was determined by GC and HPLC and the volumetric composition of the gaseous phase using an infrared gas analyzer. For the experiments in the pilot test scale with a constant biomass-to-water ratio of 1:10, the yields of solid, liquid, and gaseous phases varied between 53.39 and 37.01% (wt.), 46.61 and 59.19% (wt.), and 0.00 and 3.80% (wt.), respectively. The yield of solids shows a smooth exponential decay with temperature, while that of liquid and gaseous phases showed a smooth growth. By varying the biomass-to-water ratios, the yields of solid, liquid, and gaseous reaction products varied between 53.39 and 32.09% (wt.), 46.61 and 67.28% (wt.), and 0.00 and 0.634% (wt.), respectively. The yield of solids decreased exponentially with increasing water-to-biomass ratio, and that of the liquid phase increased in a sigmoid fashion. For a constant biomass-to-water ratio, the concentrations of furfural and HMF decreased drastically with increasing temperature, reaching a minimum at 250 °C, while that of phenols increased. In addition, the concentrations of CH3COOH and total carboxylic acids increased, reaching a maximum concentration at 250 °C. For constant process temperature, the concentrations of aromatics varied smoothly with temperature. The concentrations of furfural, HMF, and catechol decreased with temperature, while that of phenols increased. The concentrations of CH3COOH and total carboxylic acids decreased exponentially with temperature. Finally, for the experiments with varying water-to-biomass ratios, the productions of chemicals (furfural, HMF, phenols, cathecol, and acetic acid) in the aqueous phase is highly dependent on the biomass-to-water ratio. For the experiments at the laboratory scale with a constant biomass-to-water ratio of 1:10, the yields of solids ranged between 55.9 and 51.1% (wt.), showing not only a linear decay with temperature but also a lower degradation grade. The chemical composition of main organic compounds (furfural, HMF, phenols, catechol, and acetic acid) dissolved in the aqueous phase in laboratory-scale study showed the same behavior as those obtained in the pilot-scale study. [ABSTRACT FROM AUTHOR]