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Contact angles measured with the Wilhelmy plate method. (a) Advancing and (b) receding contact angles, and (c) hysteresis for poultry litter and hydrochar generated at 180˚C, 220˚C, and 250˚C after 60 min of treatment. Bars indicate standard error.
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Detailed assessment of hydrochar wetting properties, which could provide an essential understanding of underlying mechanisms during its application to soils, is lacking. We characterized hydrochar produced from hydrothermal carbonization (HTC) performed on poultry litter at various temperatures and for different times in terms of hydrophobicity and...
Citations
... Among these, different research works focused on the toxicity of AHL on seed germination. In some of these studies, AHL was mixed with other substrates as the hydrochar itself [32][33][34][35]. Most recently, Celletti et al. [23] tested the effects on the growth of a whole Zea mays plant using diluted AHL solutions as a hydroponics medium. ...
Seaweeds are considered a biomass for third-generation biofuel, and hydrothermal carbonization (HTC) is a valuable process for efficiently disposing of the excess of macroalgae biomass for conversion into multiple value-added products. However, the HTC process produces a liquid phase to be disposed of. The present study aims to investigate the effects of seed-priming treatment with three HTC-discarded liquid phases (namely AHL180, AHL240, and AHL300), obtained from different experimental procedures, on seed germination and plant growth and productivity of Phaseolus vulgaris L. To disentangle the osmotic effects from the use of AHL, isotonic solutions of polyethylene glycol (PEG) 6000 have also been tested. Seed germination was not affected by AHL seed-priming treatment. In contrast, PEG-treated samples showed significantly lower seed germination success. AHL-treated samples showed changes in plant biomass: higher shoot biomass was recorded especially in AHL180 samples. Conversely, AHL240 and AHL300 samples showed higher root biomass. The higher plant biomass values recorded in AHL-treated samples were the consequence of higher values of photosynthesis rate and water use efficiency, which, in turn, were related to higher stomatal density. Recorded data strongly support the hypothesis of the AHL solution reuse in agriculture in the framework of resource management and circular green economy.
... Recent research has been dedicated to studying the effect of HTC temperature on hydrochar characteristics and thermal behaviours. In contrast to the reaction time, the HTC temperature was found to have a significant impact on the heating value and elemental composition of the solid hydrochar [18,19]. At higher HTC temperature, solid hydrochar with a lower H/C and O/C ratio with higher heating value was produced as more water and volatile matter were removed [18,20]. ...
The ignition properties of solid hydrochars and their slurries derived from the hydrothermal carbonisation (HTC) of grape marc were evaluated and compared using radiation heating methods. Solid hydrochar samples produced at 180 °C , 220 °C and 260 °C with median particle sizes of 10 – 14 μm were mixed with water to prepare the hydrochar slurries for ignition experiments. The 260 °C solid hydrochar exhibited the shortest ignition delay time (0.2 s) and the lowest ignition temperature (179 °C). It might be due to the presence of secondary char, which was evident by a unique peak appearing in both thermogravimetric and radiation heating profiles of the 260 °C solid hydrochar. This property also demonstrated a significant impact on the combustion characteristics of its slurry. The 220 °C solid hydrochar was ignited after the 260 °C solid hydrochar (0.28 s) while its slurry experienced the longest ignition delay time among the rest (2.38 s). These observations could be related to the hydrophilic content on the outer layer of 220 °C solid hydrochar. This hydrochar and its slurry, however, ignited at the similar temperature with the 180 °C solid hydrochar and its slurry respectively, indicating that the volatile matter content had a more significant effect on the ignition temperature of the 220 °C solid hydrochar than its hydrophilic components. Results from this study further demonstrated that the hydrochar slurry derived from grape marc is highly ignitable which might provide an alternative pathway to recycle grape marc into a sustainable liquid fuel.
... The filter cake is built from polydisperse hydrochar particles. These particles are generally relatively small and have a hydrophobic surface [17,18]. Filter cake washing is optional to displace remaining suspension liquor by the washing liquor (commonly water). ...
... The cake washing pressure was set to 2.0 bar. The leaching steps L1 and L2 were performed at 0.5 bar using 40 g of oxalic acid solution of different concentrations (18,36 and 72 g l − 1 H 2 C 2 O 4 ). The oxalic acid solutions were prepared by the dissolution of the corresponding amount of oxalic acid hexahydrate (per analysis quality, p.a.) in deionized water. ...
Hydrothermal carbonization is a promising pretreatment for the energetic utilization of municipal sewage sludge. However, the carbonized slurry must be dewatered and the valuable compound phosphate recovered. This article reveals a new approach of combined slurry filtration and subsequent phosphate leaching using oxalic acid (18–72 g l⁻¹) in a single apparatus for the first time. A slurry of hydrothermally carbonized sludge was filtered, washed, leached twice with oxalic acid and washed again. A thorough characterization of the filtration performance and the process products was conducted. The suspension is difficult to filter, but the permeability of the filter cake increases during acidic leaching. The specific filter cake resistance of (4.5 ± 2.2) · 10¹⁵ m⁻² indicates poor filterability of the hydrochar slurry. 41–83% of phosphate and sodium are leached from the hydrochar, while all other investigated inorganics are leached to a lower extent. 12–31% of iron, calcium and manganese are removed from the hydrochar. The relative contents of carbon, hydrogen and oxygen increase in the residual hydrochar after leaching. After leaching, oxalic acid accounts 10.5–16.9% of the dry hydrochar due to adsorption and poor cake washing. Co-leached calcium, bivalent iron and magnesium precipitate from the leachate as oxalate salts. In conclusion, combined filtration and phosphate leaching enables efficient phosphate removal and generates an ash-reduced hydrochar for energetic utilization. However, to enable its technical application, the filtration performance and system integration need to undergo further development.
... At elevated temperatures, the hydroxyl ions of the activation agent are able to react with heteroatoms in the carbonaceous structure. This leads to the release of heteroatoms from the structure in the form of volatiles or easy soluble compounds and consequently increases the carbon content in the processed material (Mau et al., 2018). Silica-alumina can be one of the major compounds that are part of the mineral matter of PL (Shankar Pandey et al., 2019). ...
The increase in volume in bio-waste is inseparable from the production of biomass derived commodities. To reduce the use of conventional resources, the valorization of waste streams is gaining importance, and the valorisation of poultry litter fits perfectly into such scheme. This study shows a possible valorization of wet torrefied (300 °C) poultry litter (WTPL) through activation and its further use as a fertilizer, and as a wastewater micro-pollutant absorbent. The WTPL was activated thermally, physically (CO2) and chemically (KOH) at two different temperatures (600 °C and 800 °C) and 30 min residence time. The properties of ACs were evaluated based on results of the elemental and proximate analysis, suspension pH measurement, ICP-OES, FT-IR, N2 and CO2 adsorption and quantity of absorbed methylene blue (MB). The yields in thermal and physical ACs were comparable, but much higher than ACs from chemical activation (c.a. 50% and 15% at 600 °C and c.a. 47% and 6.5% at 800 °C). The thermal and physical ACs showed good suitability for application as a fertilizer due to their high macro- and micro-nutrients and low heavy metals concentration. Carbons activated with KOH proved their usefulness as wastewater pollutant absorbers through high MB's absorption (675.8 mg/g for 600 °C and 872.8 mg/g for 800 °C). Results state that the valorization of PL through activation is possible, and the selection of the activation method affects the final application of obtained material.
... The energy rentation rate of the solid phase product was similar to that of the 60 min group at the reaction temperature of 230°C-260°C under the conditions of 90 min. These results showed that since the reaction began for 60 min, the hemicellulose degradation was substantially completed (Mau et al., 2018;Qadi et al., 2019;Wu et al., 2017). The slow degradation of cellulose mainly happened in the 60-90 min interval. ...
This study provided a detailed observation on microwave-assisted hydrothermal carbonization of phoenix tree leaves. The effect of microwave and the influence of different factors on the product were analyzed by comparison and experiment separately. As the reaction severity increased, higher heating value of hydro-char increased (17.70–22.42 MJ/kg), but mass yield had the opposite trend. It was found microwave-assisted heating can economize more than 50% in time. Elemental analysis showed the highest energy rentation rate of hydro-char was obtained at 220 °C, 60 min, and pH = 7, whose higher heating value was about 27.7% higher than that of feedstock. Based on the analysis of the properties and van Krevelen diagrams of hydro-char, the reaction process was proposed. Morphological change analysis showed the surface morphology of hydro-char was partially destructed suggesting OH- can effectively promote the destruction of wood structure, and make cellulose components contact with reaction medium faster.
Although hydrochar and biochar have been used as soil conditioners, there is not a clear understanding of how their properties changes due to aging impacts their colloidal particles behavior on the soil system. From this premise, we produced hydrochar and biochar from the same feedstock (cashew bagasse) and aged with different chemical methods: (i) using hydrogen peroxide, (ii) a mixture of nitric and sulfuric acids, and (iii) hot water. It was analyzed the effects of aging on the stability of the carbonaceous materials (CMs) colloids in aqueous medium with different ionic strength (single systems), as well as the stability of the natural-soil colloid when interacting with biochar and hydrochar colloids (binary systems). A chemical composition (C, H, N, and O content) change in CMs due to the chemically induced aging was observed along with minor structural modifications. Chemical aging could increase the amount of oxygen functional groups for both biochar and hydrochar, though in a different level depending on the methodology applied. In this sense, hydrochar was more susceptive to chemical oxidation than biochar. The effectiveness of chemical aging treatments for biochar increased in the order of water < acid < hydrogen peroxide, whereas for hydrochar the order was water < hydrogen peroxide < acid. While the increase in surface oxidation improved the biochar colloidal stability in water medium at different ionic strengths (single systems), the stability and critical coagulation concentration (CCC) slightly changed for hydrochar. Natural-soil clay (NSC) interactions with oxidized carbonaceous material colloids (binary systems) enhanced NSC stability, which is less likely to aggregate. Therefore, the aging of carbonaceous materials modifies the interaction and dynamics of soil small particles, requiring far more attention to the environmental risks due to their application over time.
Using aquatic biomass as a solid fuel is limited by its low energy density, low lignin content and high moisture content. This study investigated upgrading aquatic biomass as a solid fuel using hydrothermal carbonization with temperatures in the moderate temperatures range for a reaction time of 30 min. Thermogravimetric analysis (TGA) tests were used to study the combustion behavior of the raw aquatic biomass and its derived hydrochar during the combustion process. Chemical composition analysis indicated that compared to the raw aquatic biomass, the fuel quality of the derived hydrochar had been improved by increasing the carbon contents with a substantial decrease in the volatile matter and ash content. Furthermore, higher fuel quality of the derived hydrochar was observed with increasing hydrothermal temperature. Similarly, based on the TGA test, the hydrochars had increased ignition temperatures, higher combustion temperatures and higher burnout temperatures compared to the raw aquatic biomass. The combustion characteristic index values for all hydrochar samples derived from water hyacinth and cattail leaves were appropriate for combustion.
The conversion of poultry litter to hydrochar has been proposed for stabilization of the soils and to eliminate pathogens. Still, research on the hydrochar's effect on soil properties as a function of production temperature, and its direct use with plants is limited in general and even less so on poultry litter. We characterized poultry litter hydrochar as an amendment for sandy soils in terms of changes to the soil's bulk density, porosity, water-retention capacity, and fertility. Soil bulk density, porosity and water-retention capacity were determined in a pneumatic tension plate system for sand with hydrochar-amendment rates of 0.5, 1 and 2%, and hydrochar-production temperature of 180, 220, and 250 � C. Soil fertility was assessed by growing lettuce seedlings in a randomized block design planter experiment, consisting of 16 blocks that were sampled every 10 days. The addition of poultry litter hydrochar resulted in decreased soil bulk density. Soil porosity increased with hydrochar generated at a temperature of up to 220 � C, and decreased with hydrochar generated at 250 � C. Soil water content increased as compared to unamended sand, but decreased with increasing hydrochar-production temperature, probably due to increasing hydrophobicity of the poultry litter hydrochar. The addition of hydrochar at concentrations of 0.5 and 1% resulted in improved plant growth despite an initial delay. While increased soil moisture due to increased soil water-retention capacity was confirmed, it did not seem to be responsible for the improved plant growth. It was also demonstrated for the first time that hydrochar decreases nitrate leaching from soils. Therefore, poultry litter-derived hydrochar seems to be an adequate amendment for sandy soils.
The conversion of poultry litter to hydrochar has been proposed for stabilization of the soils and to eliminate pathogens. Still, research on the hydrochar's effect on soil properties as a function of production temperature, and its direct use with plants is limited in general and even less so on poultry litter. We characterized poultry litter hydrochar as an amendment for sandy soils in terms of changes to the soil's bulk density, porosity, water-retention capacity, and fertility. Soil bulk density, porosity and water-retention capacity were determined in a pneumatic tension plate system for sand with hydrochar-amendment rates of 0.5, 1 and 2%, and hydrochar-production temperature of 180, 220, and 250 � C. Soil fertility was assessed by growing lettuce seedlings in a randomized block design planter experiment, consisting of 16 blocks that were sampled every 10 days. The addition of poultry litter hydrochar resulted in decreased soil bulk density. Soil porosity increased with hydrochar generated at a temperature of up to 220 � C, and decreased with hydrochar generated at 250 � C. Soil water content increased as compared to unamended sand, but decreased with increasing hydrochar-production temperature, probably due to increasing hydrophobicity of the poultry litter hydrochar. The addition of hydrochar at concentrations of 0.5 and 1% resulted in improved plant growth despite an initial delay. While increased soil moisture due to increased soil water-retention capacity was confirmed, it did not seem to be responsible for the improved plant growth. It was also demonstrated for the first time that hydrochar decreases nitrate leaching from soils. Therefore, poultry litter-derived hydrochar seems to be an adequate amendment for sandy soils.
