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This study investigates the potential use of white lupine straw (WLS), an underutilized agricultural by-product, as a raw material to produce valuable biochemicals such as monosaccharides and 5-hydroxymethylfurfural (5-HMF) through hydrothermal pretreatment. The aim was to optimize mild reaction conditions to maximize the recovery of these products while minimizing degradation. The hydrothermal treatment of WLS in subcritical water with trace amounts of sulfuric acid was performed, followed by a two-step approach to evaluate the yields of hemicellulose and 5-HMF. The highest monosaccharide yield (163 g/kg) was achieved at temperatures between 174 and 181 °C and a holding time of 7–14 min, while the 5-HMF production was 139.9 g/kg at 199–203 °C and after 0.5–4.5 min. These results suggest that optimal 5-HMF production also increases the remaining solid residue. This study highlights the feasibility of WLS as a sustainable, low-cost biomass resource. It highlights the balance between temperature and time to maximize valuable product yields. The results contribute to advancing biorefinery processes by demonstrating that WLS can be effectively converted into bioethanol precursors and industrial chemicals, supporting circular bioeconomy principles and providing an environmentally friendly alternative to burning crop residues. [ABSTRACT FROM AUTHOR]

Positive roles of hydrothermal pretreatment and acidic hydrothermal pretreatment were researched in this study. Results of pyrolysis indicated that hydrothermal pretreatment not only significantly enriched levoglucosan (LG) content in bio-oil, but also increased specific surface area of bio-char. When acid was introduced into hydrothermal pretreatment process, the top-quality liquid and solid products acquired at a relatively low pretreatment temperature. For bio-oil, the LG content increased from 0% in rice husk (RH) to 32.68% in the sample hydrothermal pretreated in deionized water at 170 ℃ (TRH170). The highest LG content of 43.0% obtained from the sample hydrothermal pretreated in phosphoric acid solution at 115 ℃ (PTRH115). The BET of bio-char after activation increased from 2135.6 m2/g in RH to 2508.3 m2/g in TRH170. And acid addition optimized the pore distribution of activated bio-char. Both of the average pore size and efficient pore volume in micro-pore section were noticeably increased. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effect of chemical-free two-stage hydrothermal and mechanical refining pretreatment on improving the sugar yields during enzymatic hydrolysis of forest residue biomass (FRB) and optimize the pretreatment conditions. Hot-water pretreatment experiments were performed using a central composite design for three variables: temperature (160–200 °C), time (10–20 min), and solid loading (10–20%). Hydrothermally pretreated biomass was subsequently pretreated using three cycles of disk refining. The combined pretreatment was found to be highly effective in enhancing sugar yields during enzymatic hydrolysis, with almost 99% cellulose conversion for biomass pretreated at 213.64 °C, 15 min, and 15% solid loading. However, the xylose concentrations in the hydrolysate were found to be low under these conditions due to sugar degradation. Thus, less severe optimum pretreatment conditions (194.78 °C, 12.90 min, and 13.42% solid loading) were predicted using a second-order polynomial model. The response surface model optimized the hydrothermal pretreatment of FRB and predicted the glucan, xylan, and overall conversions of 94.57%, 79.78%, and 87.84%, respectively, after the enzymatic hydrolysis. The model-predicted biomass conversion values were validated by the experimental results. [ABSTRACT FROM AUTHOR]

Whether advanced biological waste treatment technologies, such as hydrothermal pretreatment (HTP) integrated anaerobic digestion (AD), could enhance the removal of different antibiotics remains unclear. This study investigated the outcome of antibiotics and methane productivity during pig manure treatment via HTP, AD, and HTP + AD. Results showed improved removal efficiency of sulfadiazine (SDZ), oxytetracycline (OTC), and enrofloxacin (ENR) with increased HTP temperatures (70, 90, 120, 150, and 170 °C). OTC achieved the highest removal efficiency of 86.8% at 170 °C because of its high sensitivity to heat treatment. For AD, SDZ exhibited resistance with a removal efficiency of 52.8%. However, OTC and ENR could be removed completely within 30 days. When HTP was used prior to AD, OTC and ENR could achieve complete removal. However, residual SDZ levels reduced to 20% and 16% at 150 and 170 °C, respectively. The methanogenic potential showed an overall upward trend as the HTP temperature increased. Microbial analysis revealed the antibiotics-induced enrichment of specific microorganisms during AD. Firmicutes were the dominant bacterial phylum, with their abundance positively correlated with the addition of antibiotics. Methanobacterium and Methanosarcina emerged as the dominant archaea that drove methane production during AD. Thus, HTP can be a potential pretreatment before AD to reduce antibiotic-related risks in manure waste handling. [ABSTRACT FROM AUTHOR]

Food waste (FW) biotransformation into bioenergy has garnered a lot of scientific interest as a way to address the energy crisis and trash disposal issues. FW is converted into biogas, a gaseous combination of biomethane and carbon dioxide. In order to valorize FW, anaerobic digestion (AD) with combined pretreatment (hydrothermal (HT) and ultrasonic (US)) is used as a potential method. Three digesters were investigated: the control (unpretreated), HT(121°C) + US, and HT(134°C) + US, respectively. Based on changes in the combined pretreatment conditions, the paper assessed the methane productivity. Furthermore, kinetic modeling was evaluated with six kinetic models. The results show that the HT pretreatment at 121°C combined with US improves the volatile solid (VS) removal to 73 ± 5% and the methane yield to 529.7 ± 11 NmL/gVS. Both the Transference model and the first order have the greatest fits in terms of R2, and they also have the best fits in terms of relative errors, and methane production rate, respectively. The combined pretreatment has a positive impact on increasing methane yield as well as stabilizing the anaerobic digestion process. [ABSTRACT FROM AUTHOR]

Paper sludge (PS) from paper mills has a significant potential for bioethanol production. In this study, waste-paper-containing PS is used as the raw material for bioethanol production because the annual waste paper utilization rate has increased globally. Although PS does not require delignification, the antiseptics and deinking agents in waste paper-containing PS inhibit enzymatic reactions such as saccharification and fermentation. Their removal is important, but it has not yet been reported. Using subcritical water pretreatment, the selective decomposition of enzyme inhibitors in PS is examined without the generation of other enzyme inhibitors. The optimum pretreatment conditions are identified as 240 °C, 3.3 MPa, 3 min, and pH 4.5. Glucose was obtained in 71% yield from pretreated 5 wt% PS using cellulase, which is 5.5 times higher than that from unpretreated PS. This is because the reactivity of the pretreated PS increases with increasing surface area of the cellulose fibers, and the cellulase inhibitors are decomposed by subcritical water. Next, semi-simultaneous saccharification and fermentation treatments are performed to produce bioethanol from waste-paper-containing PS. The bioethanol yield based on cellulose after 96 h is 68% for PS pretreated with subcritical water, whereas the bioethanol yield is 6% for unpretreated PS. Therefore, subcritical water pretreatment increases the bioethanol yield by 11 times. The proposed method may enable the use of large amounts of PS as ethanol feedstock in future. [ABSTRACT FROM AUTHOR]

Cooked rice and the vegetables like lettuce are common kitchen waste, which are carbonaceous materials and have the potential as feedstock for the production of activated carbon. Cooking is similar to hydrothermal treatment (HTC), which might impact the subsequent activation of kitchen waste. In this study, the HTC of lettuce, rice, or their mixture and the activation of the resulting hydrochars were conducted. The results indicated that cross-polymerization between the N-containing organics from lettuce and the sugar derivatives from rice took place in their co-HTC, which significantly increased the hydrochar yield. Activation of the hydrochar from the co-HTC generated the AC with a yield of 2 times that from direct activation of mixed lettuce/rice. However, the co- HTC facilitated aromatization, reducing reactivity with K2C2O4 in activation and producing the AC with main micropores and low specific surface area. Activation of the hydrochar from HTC of rice followed the above trend, while that from lettuce was the opposite. The organics in lettuce were thermally unstable and could not undergo sufficient aromatization. The activation of hydrochar from HTC of lettuce thus generated the AC with the lowest yield, but the highest specific surface area (1684.9 m²/g), abundant mesopores, and superior capability for adsorption of tetracycline. However, the environmental impacts and energy consumption for the production of AC from the hydrochar of lettuce were higher than that from hydrochar of co-HTC. [ABSTRACT FROM AUTHOR]

The efficiency of anaerobic digestion of sludge can be significantly improved through a combination of acid or alkali hydrolysis with low-temperature hydrothermal (LTH) pretreatment. The impact of various agents in conjunction with LTH treatment on sludge properties and high-temperature anaerobic digestion (HTAD) systems was comprehensively examined in this study. Comparative analyses reveal that NaOH-LTH pretreatment surpasses HCl-LTH pretreatment in enhancing sludge organic matter solubilization and enhancing HTAD system. Contrary to expectations, the use of acetic acid (HAc) pretreatment does not further enhance organic matter solubilization in sludge. Instead, it inhibits gas production efficiency and diminishes the removal efficiency of total chemical oxygen demand (TCOD) during HTAD. Among the pretreatments, NaOH (pH 11, 24 h)-LTH (90 °C, 30 min) co-treatment emerges as the optimal condition. This configuration results in a 12.5-fold increase in sludge soluble chemical oxygen demand (SCOD) compared to untreated samples, a 34.1% improvement in methane yield in the HTAD system, and a remarkable TCOD removal efficiency of 36.8%. Notably, this combined pretreatment induces significant alterations in the microbial community structure of the sludge HTAD system. Following NaOH-LTH pretreatment, the total relative abundance of methanogenic archaea increases from 80.2 to 92.3% compared to untreated systems. [ABSTRACT FROM AUTHOR]

Abstract Background Lipids produced using oleaginous yeast cells are an emerging feedstock to manufacture commercially valuable oleochemicals ranging from pharmaceuticals to lipid-derived biofuels. Production of biofuels using oleaginous yeast is a multistep procedure that requires yeast cultivation and harvesting, lipid recovery, and conversion of the lipids to biofuels. The quantitative recovery of the total intracellular lipid from the yeast cells is a critical step during the development of a bioprocess. Their rigid cell walls often make them resistant to lysis. The existing methods include mechanical, chemical, biological and thermochemical lysis of yeast cell walls followed by solvent extraction. In this study, an aqueous thermal pretreatment was explored as a method for lysing the cell wall of the oleaginous yeast Rhodotorula toruloides for lipid recovery. Results Hydrothermal pretreatment for 60 min at 121 °C with a dry cell weight of 7% (w/v) in the yeast slurry led to a recovery of 84.6 ± 3.2% (w/w) of the total lipids when extracted with organic solvents. The conventional sonication and acid-assisted thermal cell lysis led to a lipid recovery yield of 99.8 ± 0.03% (w/w) and 109.5 ± 1.9% (w/w), respectively. The fatty acid profiles of the hydrothermally pretreated cells and freeze-dried control were similar, suggesting that the thermal lysis of the cells did not degrade the lipids. Conclusion This work demonstrates that hydrothermal pretreatment of yeast cell slurry at 121 °C for 60 min is a robust and sustainable method for cell conditioning to extract intracellular microbial lipids for biofuel production and provides a baseline for further scale-up and process integration. Graphical abstract

Abstract The production of date syrup yields a substantial amount of date press cake (DPC), fibrous and moisturising material with great potential for generating value through bioprocessing. However, the recalcitrant structure of DPC affects the yield of products in bioprocesses. To boost the accessibility of the structure as well as increase the soluble fraction of carbohydrates and facilitate further enzymatic hydrolysis, hydrothermal and dilute acid (0.5% (v/v) sulfuric acid) pretreatments as cost-effective and feasible methods were applied on DPC at relatively low temperatures (80, 100, 120 and 140 °C) and reaction times (60 and 90 min). The success in pretreatment was then evaluated by a post-enzymatic treatment using an enzyme cocktail of cellulases and hemicelluloses. Based on total accessible sugar with minimum produced inhibitors, an optimal operating condition was considered acid pretreatment at 120 °C for 90 min with a 55.02% increase in total sugar yield. To explore the potential use of pretreated DPC, an anaerobic digestion was conducted on untreated and acid-pretreated DPC at 120 °C for 90 min. The results showed that pretreatment increased the total bioproduct yield, including hydrogen, ethanol, and volatile fatty acid yields, by 59.75%. This demonstrates the significant impact of pretreatment on product yields in a bioprocess.

Background: Lipids produced using oleaginous yeast cells are an emerging feedstock to manufacture commercially valuable oleochemicals ranging from pharmaceuticals to lipid-derived biofuels. Production of biofuels using oleaginous yeast is a multistep procedure that requires yeast cultivation and harvesting, lipid recovery, and conversion of the lipids to biofuels. The quantitative recovery of the total intracellular lipid from the yeast cells is a critical step during the development of a bioprocess. Their rigid cell walls often make them resistant to lysis. The existing methods include mechanical, chemical, biological and thermochemical lysis of yeast cell walls followed by solvent extraction. In this study, an aqueous thermal pretreatment was explored as a method for lysing the cell wall of the oleaginous yeast Rhodotorula toruloides for lipid recovery. Results: Hydrothermal pretreatment for 60 min at 121 °C with a dry cell weight of 7% (w/v) in the yeast slurry led to a recovery of 84.6 ± 3.2% (w/w) of the total lipids when extracted with organic solvents. The conventional sonication and acid-assisted thermal cell lysis led to a lipid recovery yield of 99.8 ± 0.03% (w/w) and 109.5 ± 1.9% (w/w), respectively. The fatty acid profiles of the hydrothermally pretreated cells and freeze-dried control were similar, suggesting that the thermal lysis of the cells did not degrade the lipids. Conclusion: This work demonstrates that hydrothermal pretreatment of yeast cell slurry at 121 °C for 60 min is a robust and sustainable method for cell conditioning to extract intracellular microbial lipids for biofuel production and provides a baseline for further scale-up and process integration. Highlights: Hydrothermal pretreatment was evaluated as a method for lysing oleaginous yeast cell walls. Thermal lysis of a yeast slurry (7% w/v, dry cell weight basis) at 121 °C for 60 min. followed by solvent extraction yielded 84.6 ± 3.2% (w/w) of the total lipids. Hydrothermal pretreatment of a yeast slurry (7% (w/v, dry cell weight basis)) at 170 °C for 10 min yielded 35.6 ± 0.6% (w/w) of the total lipids. Conditioning yeast slurry at 121 °C for 60 min is proposed to be a green scalable method for cell lysis. [ABSTRACT FROM AUTHOR]

The production of date syrup yields a substantial amount of date press cake (DPC), fibrous and moisturising material with great potential for generating value through bioprocessing. However, the recalcitrant structure of DPC affects the yield of products in bioprocesses. To boost the accessibility of the structure as well as increase the soluble fraction of carbohydrates and facilitate further enzymatic hydrolysis, hydrothermal and dilute acid (0.5% (v/v) sulfuric acid) pretreatments as cost-effective and feasible methods were applied on DPC at relatively low temperatures (80, 100, 120 and 140 °C) and reaction times (60 and 90 min). The success in pretreatment was then evaluated by a post-enzymatic treatment using an enzyme cocktail of cellulases and hemicelluloses. Based on total accessible sugar with minimum produced inhibitors, an optimal operating condition was considered acid pretreatment at 120 °C for 90 min with a 55.02% increase in total sugar yield. To explore the potential use of pretreated DPC, an anaerobic digestion was conducted on untreated and acid-pretreated DPC at 120 °C for 90 min. The results showed that pretreatment increased the total bioproduct yield, including hydrogen, ethanol, and volatile fatty acid yields, by 59.75%. This demonstrates the significant impact of pretreatment on product yields in a bioprocess. [ABSTRACT FROM AUTHOR]

Xylan is the most abundant constituent of hemicellulose fraction of lignocellulosic biomass. Short xylooligosaccharides (XOS), obtained via xylan hydrolysis, have well-known prebiotic and antioxidant properties that are beneficial for human and animal health. In this study, two alternative pretreatment strategies (alkali and hydrothermal) and three different enzymes were applied for enzymatic XOS production from sugarcane bagasse. The enzymatic hydrolysis was performed with nine different combinations of recombinant endo-xylanases from GH11 and GH10 families and GH11 xylobiohydrolase. Hydrothermal pretreatment followed by optimized enzymatic hydrolysis yielded up to 96 ± 1 mg of XOS per gram of initial biomass, whereas enzymatic hydrolysis of alkali-pretreated sugarcane bagasse rendered around 47.6 ± 0.2 mg/g. For both alkali and hydrothermal routes, the maximum yields of short-length XOS were obtained using the GH10 xylanase alone. Furthermore, differences in XOS profiles obtained by controlled mixtures of the enzymes have been evaluated. For both routes, the best yields of short-length XOS were obtained using the GH10 xylanase alone, which is consistent with the notion that sugarcane xylan substitutions partially hinder GH11 xylanase activity. The results presented here show that a green and cost-effective hydrothermal pretreatment path for xylooligosaccharides production, rendered considerably better XOS yields. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrothermal pretreatment of press mud (PM) improved resource recovery options. • The combustion properties of hydrochar (HC) were superior than PM. • No phytotoxicity was found with PM and HC for the germination of mung bean seeds. • Significant biogas generation from process water was observed. In the present study, press mud (PM), a major waste by-product from sugar industries, was subjected to hydrothermal pretreatment (HTP) to create resource recovery opportunities. The HTP process was performed with the PM samples in a laboratory scale high pressure batch reactor (capacity = 0.7 L) at 160 °C and 200 °C temperatures (solids content = 5 % and 30 %). The pretreatment resulted in separation of solid and liquid phases which are termed as solid hydrochar (HC) and process water (PW), respectively. High heating value (HHV) of HC was ∼14–18 MJ kg−1, slightly higher than that of PM (14 MJ kg−1). The thermogravimetric analysis showed about 1.5–1.7 times higher heat release from HC burning compared to that observed from combustion of PM. Apart from this, the HC and PM showed no phytotoxicity during germination of mung bean (Vigna radiata). Moreover, the biochemical methane potential test on the PW showed a generation of 167–245 mL biogas per gram of chemical oxygen demand added. Hence, the HTP offers several resource recovery opportunities from PM which may also reduce the risks of environmental degradation. [ABSTRACT FROM AUTHOR]

Microporous carbon adsorbents with high surface area and porosity were synthesized from lignin using an acrylic acid pretreatment strategy. Lignin was grafted with acrylic acid via hydrothermal treatment to introduce carboxyl groups, as verified by NMR and FT-IR spectroscopy. The incorporated carboxyls enabled ion exchange reactions between lignin and potassium during subsequent potassium hydroxide (KOH) activation. This optimized the dispersion of potassium, allowing effective activation even at low KOH levels. The effects of process parameters, including acrylic acid content, hydrothermal time, and KOH ratio, were investigated. Optimal conditions of 5 wt% acrylic acid and 6 h hydrothermal reaction produced a carbon adsorbent with exceptional Brunauer–Emmett–Teller (BET) surface area of 1708 m2/g and pore volume of 0.82 cm3/g at a lignin:KOH:acrylic acid ratio of 1:0.5:0.05. Characterization by FE-SEM, XRD, EDS, and Raman spectroscopy confirmed the successful synthesis of an optimized microporous carbon material. The carbon exhibited an outstanding lead ion adsorption capacity of 371 mg/g by Langmuir modeling. Adsorption kinetics followed pseudo-second-order, indicating chemisorption as the rate-controlling step. Thermodynamic analysis revealed the endothermic nature of lead adsorption, further enhanced at higher temperatures. Overall, the acrylic acid pretreatment approach enabled sustainable production of high surface area microporous carbon adsorbents from lignin using minimal KOH activation. The adsorbents demonstrated tremendous potential for removing lead ions via chemisorption mechanisms. [ABSTRACT FROM AUTHOR]

In this study, a nonionic surfactant (JFC-M) was used as an additive for hydrothermal pretreatment of crushed poplar wood. The pseudo-lignin extracted from holocellulose after hydrothermal pretreatment was characterized, and the composition of liquid and solid fractions obtained after pretreatment at different experimental conditions was analyzed. The results showed that the addition of JFC-M surfactant accelerated the dissolution of biomass cellulose and effectively inhibited the production of pseudo-lignin in hydrothermal processes, under the same hydrothermal pretreatment conditions. The pseudo-lignin yield for the control group was 14.2% (no JFC surfactant added), whereas when the JFC-M concentration was 2%, the pseudo-lignin yield was 9.8%.

Initial material characteristics were one of the decisive factors affecting the hydrothermal pretreatment of woody biomass with a dense structure. In this study, the effect of initial material particle size on poplar hydrothermal pretreatment and enzymatic hydrolysis was evaluated. The enzymatic hydrolysis yield and the accessibility of the enzymatic reaction were significantly increased with an initial material with an average particle size of initial material (D50) < 500 μm, because of the different pretreatment effects of initial material. SEM and compositional analysis indicated that the reduction of the initial particle size facilitated hydrothermal pretreatment with better depolymerization effects. The bulk density of D50 < 500 μm increased by 28.87%, and the SSA increased by 68.51% compared with 2000–2500 μm. In contrast, the water holding capacity decreased by 59.40%. In addition, there was almost no free water in D50 < 500 μm and had weak mechanical properties, which was more conducive to the stirring of the hydrothermal pretreatment. Compared with the particle size of initial material being less than 100 μm, the D50 of initial material between 100 and 2500 μm was more energy saving and economically feasible. The particle size of poplar powder in this study could reduce pretreatment intensity and energy consumption and improve pretreatment energy efficiency significantly. This study was meaningful in identifying the size effects and exploring the optimal properties of initial material for poplar on hydrothermal pretreatment. [ABSTRACT FROM AUTHOR]

Although the addition of bran to bread makes it healthier and more functional, it brings with it some technological problems. One way to eliminate these problems is hydrothermal pretreatment of wheat bran. In this study, five different ratios (10%, 20%, 30%, 50%, and 100%) of hydrolysates from hydrothermal pretreatment of wheat bran (150°C, 30 min) were substituted with dough‐kneading water during dough kneading for bread making. The physical, chemical, functional, textural and important starch fractions of the bread produced were determined. The addition of hydrolysate in different amounts to the dough‐kneading water resulted in similar physical properties (height, specific volume, and crust color) as the control bread. While the addition of hydrolysate decreased the hardness of the breads, it positively improved important starch fractions (increasing the amount of slowly digestible starch and decreasing the amount of rapidly digestible starch). It also increased antioxidant capacity (iron (III) reducing antioxidant power, ABTS, and DPPH (2,2‐diphenyl‐1‐picrylhydrazyl) and reduced the starch hydrolysis index of the bread. It was shown that the hydrolysate obtained after the hydrothermal treatment of bran could be used in bread making to satisfy the demand for products preferred by consumers from both health and sensory points of view. [ABSTRACT FROM AUTHOR]

This study focused on the co-fermentation of food waste and tissue paper to produce ethanol, which will eliminate the need for additional nitrogen sources and nutrients, thereby reducing production costs. In response to the inhibitory effect of the high concentrations of glucose present in mixed-substrate hydrolysates on xylose fermentation, a co-fermentation process using Saccharomyces cerevisiae and Candida shehatae was proposed. This approach reduced the fermentation time by 24 h, increased the xylose utilization rate to 88%, and improved the ethanol yield from 41% to 46.5%. The impact of external conditions and corresponding optimization were also analyzed in this process. The optimum conditions were a 1:3 ratio of Saccharomyces cerevisiae to Candida shehatae, a pH of 5, and shaking at 150 r/min, and by employing dynamic temperature control, the ethanol production was increased to 21.98 g/L. Compared to conventional processes that only use Saccharomyces cerevisiae, this method enhanced the ethanol yield from 41% to 49%. [ABSTRACT FROM AUTHOR]

Burning corncob for energy requirements caused a huge waste of biomass resources and serious environment pollution. Herein, this study provided a high-value utilization strategy for corncob. Corncob was first pretreated by hydrothermal process. The collected hydrolysates were converted into furfural by a recyclable solid acid with a yield of 52.35%. The pretreated solid was disintegrated into fibers by disc grinding. When corncob fiber addition is below 15%, the ring crush index, tear index, and tensile strength index of the prepared handsheets increased by 1.43 N·m/g, 0.43 mN·m2/g, and 4.66 N·m/g, respectively, compared with that using pure softwood fibers. Besides, corncob fibers were hydrophilically modified with aminosulfonic acid. Water retention value of paper with the modified fiber addition increased by 48.35%. Therefore, this study provided a method of corncob utilization toward two purposes: furfural production and papermaking. [ABSTRACT FROM AUTHOR]

This study investigates the co-digestion of hydrothermally pretreated empty fruit bunches (EFB) at 190 °C for 5 min (HTP190-EFB) with decanter cake (DC) to improve biogas production in high solid anaerobic digestion (HSAD). The HTP190-EFB exhibited a 67.98 % reduction in total solids, along with the production of 0.89 g/L of sugar, 2.39 g/L of VFA, and 0.56 g/L of furfural in the liquid fraction. Co-digestion of HTP190-EFB with DC at mixing ratios of 5, 10, and 15 %w/v demonstrated improved methane yields and process stability compared to mono-digestion of HTP190-EFB. The highest methane yield of 372.69 mL CH4/g-VS was achieved in the co-digestion with 5 %w/v DC, representing a 15 % increase compared to digestion of HTP190-EFB (324.30 mL CH4/g-VS) alone. Synergistic effects were quantified, with the highest synergistic methane yield of 77.65 mL CH4/g-VS observed in the co-digestion with 5 %w/v DC. Microbial community analysis revealed that co-digestion of hydrothermally pretreated EFB with decanter cake promoted the growth of Clostridium sp., Lactobacillus sp., Fibrobacter sp., Methanoculleus sp., and Methanosarcina sp., contributing to enhanced biogas production compared to mono-digestion of pretreated EFB. Energy balance analysis revealed that co-digestion of HTP190-EFB with DC resulted in a total net energy of 599.95 kW, 52 % higher than mono-digestion of HTP190-EFB (394.62 kW). Economic analysis showed a shorter return on investment for the co-digestion system (0.86 years) compared to the mono-digestion of HTP190-EFB (1.02 years) and raw EFB (2.69 years). The co-digestion of HTP190-EFB with 5 %w/v DC offers a promising approach to optimize methane yield, process stability, and economic feasibility, supporting the palm oil industry for producing renewable energy and sustainable waste management.

This work presents a new sequential approach to the sugarcane bagasse autohydrolysis process in a way that the liquor from the previous reaction was reused in the next one, and the makeup water for the next batch was used to wash the solid fraction before being added to the liquor in the next batch. This approach was suggested first as a way of reducing the water usage in the process, and second as a way of concentrating the liquor in any interesting component, working with the possibility of losing efficiency towards the glucose production through a cellulose loss to the liquor or enzymatic efficiency loss from a higher inhibitor concentration. Two sets of five sequential batches were performed: one washing the solids with the makeup water prior to the enzymatic step (Set 2), and the other one without the washing step (Set 1), looking forward to the effects of the water reuse over the glucose production and the liquor composition. Autohydrolysis pretreatment removed most of the hemicellulose (∼94 %), with liquor recycling improving its removal until the third batch and stabilizing after that. Although the washing step showed little impact on the composition of the solids, it was determinant to the success of the enzymatic hydrolysis, since it was possible to maintain the cellulose to glucose yield around 53% throughout the batches. There was a 64 % reduction in the water used in the sequential reactions without interfering in the glucose production, which indicates that the proposed strategy could be successfully used to reduce costs and environmental impacts associated with the pretreatment of lignocellulosic biomass.

This study investigates the potential use of white lupine straw (WLS), an underutilized agricultural by-product, as a raw material to produce valuable biochemicals such as monosaccharides and 5-hydroxymethylfurfural (5-HMF) through hydrothermal pretreatment. The aim was to optimize mild reaction conditions to maximize the recovery of these products while minimizing degradation. The hydrothermal treatment of WLS in subcritical water with trace amounts of sulfuric acid was performed, followed by a two-step approach to evaluate the yields of hemicellulose and 5-HMF. The highest monosaccharide yield (163 g/kg) was achieved at temperatures between 174 and 181 °C and a holding time of 7–14 min, while the 5-HMF production was 139.9 g/kg at 199–203 °C and after 0.5–4.5 min. These results suggest that optimal 5-HMF production also increases the remaining solid residue. This study highlights the feasibility of WLS as a sustainable, low-cost biomass resource. It highlights the balance between temperature and time to maximize valuable product yields. The results contribute to advancing biorefinery processes by demonstrating that WLS can be effectively converted into bioethanol precursors and industrial chemicals, supporting circular bioeconomy principles and providing an environmentally friendly alternative to burning crop residues.

Suitable fermentation substrates and fermentation modes can effectively improve the fermentation ethanol yield. In this study, we optimised the hydrothermal pretreatment conditions by orthogonal optimisation using waste tissue paper as substrate. These conditions consisted of 50 min duration in a high-pressure reactor with pure water as solvent at a temperature of 160 °C. The biomass to water ratio was maintained at a constant level. The cellulose content of the pretreated TP was 81.19 ± 4.06%, which was an increase of 21.59% compared to the blank control. The 72 h reducing sugar yield of pretreated TP was 0.61 g sugar/g paper, which was 38.64% higher than that of untreated TP. Subsequently, the pretreated TP was fermented under optimal conditions. The mixed group of Saccharomyces cerevisiae and Candida shehatae (SC) showed a distributed saccharification fermentation pattern, with an ethanol yield of 28.11 g/L in 72 h. On the other hand, the single Saccharomyces cerevisiae (S) exhibited a homobloc saccharification fermentation pattern, with an ethanol yield of 35.15 g/L in 72 h.

This study aimed to investigate the effect of chemical-free two-stage hydrothermal and mechanical refining pretreatment on improving the sugar yields during enzymatic hydrolysis of forest residue biomass (FRB) and optimize the pretreatment conditions. Hot-water pretreatment experiments were performed using a central composite design for three variables: temperature (160–200 °C), time (10–20 min), and solid loading (10–20%). Hydrothermally pretreated biomass was subsequently pretreated using three cycles of disk refining. The combined pretreatment was found to be highly effective in enhancing sugar yields during enzymatic hydrolysis, with almost 99% cellulose conversion for biomass pretreated at 213.64 °C, 15 min, and 15% solid loading. However, the xylose concentrations in the hydrolysate were found to be low under these conditions due to sugar degradation. Thus, less severe optimum pretreatment conditions (194.78 °C, 12.90 min, and 13.42% solid loading) were predicted using a second-order polynomial model. The response surface model optimized the hydrothermal pretreatment of FRB and predicted the glucan, xylan, and overall conversions of 94.57%, 79.78%, and 87.84%, respectively, after the enzymatic hydrolysis. The model-predicted biomass conversion values were validated by the experimental results.

Lignocellulosic biomass is a promising raw material for energy production due to its low cost and sustainability. In this work, Egeria densa, Typha domingensis,Eichhornia crassipes, and Cyperus papyrus 'Nanus' aquatic macrophytes were evaluated as a potential to produce methane, and their biochemical transformations were investigated. All substrate produced biogas by anaerobic fermentation. The values obtained to methane yield were 170.47, 132.42, 121.90, and 180.57 mLCH4 gSV−1, respectively. The hydrolysis rate was higher using E. densa biomass. Total volatile acid concentrations were 32.56 mg L−1 (E. densa), 77.35 mg L−1 (T. domingensis), 22.8 (E. crassipes), and 12.4 mg L−1 (Cyperus papyrus 'Nanus'). The more significant microbiological activity was observed in the reactors using E. densa (RE) and T. domingensis (RT). The total and volatile solids removal order was RE > RT > Rec (E. crassipes) > RP (Cyperus papyrus 'Nanus'). So, for recovery of the bioenergy step, the E. densa biomass obtained the most promising results, and it was selected for hydrothermal pretreatment (HPT). After HPT, the biomass was more suitable for bioprocessing, increasing the carbohydrates available. There was a reduction in the crystallinity index due to the low lignin content and increased type II cellulose amorphous fraction. Also, the samples increased thermal stability (374 °C and 388 °C) and showed morphology with fibers partially disorganized. The methane yield was 4.2% higher as the time increased of the HPT. And the material became more vulnerable to attack by methanogenic microorganisms, resulting in greater energy production, with a potential of E. densa to generate methane. [ABSTRACT FROM AUTHOR]

Hydrothermal methods are commonly applied in pretreatment of lignocellulose for conversion to biofuels and chemicals. This pretreatment partially disassembles and solubilizes hemicelluloses and lignin, releasing sugars and phenolic compounds, which are potential inhibitors for the subsequent enzymatic saccharification step. In this work, the inhibitory effect of soluble phenolics in hydrothermal pretreatment liquor on canonical Trichoderma reesei enzymes was investigated, using purified cellobiohydrolases, endoglucanases, a xylanase, and a lytic polysaccharide monooxygenase, as well as commercial enzyme cocktails Cellic Ctec2 and Celluclast. The pretreatment liquor was fractionated to enrich the phenolics, and thoroughly analyzed. The most sensitive to phenolics inhibition were cellobiohydrolases, the major enzymes in crystalline cellulose degradation and the primary component in cellulolytic mixtures. These were inhibited by the oligophenolics and phenol-carbohydrate complexes (lignin-carbohydrate complex type of compounds), the latter of which could be mitigated by other enzymes, i.e., xylanases and endoglucanases. Addition of lytic polysaccharide monooxygenase to the hydrolysis reactions was found to relieve the negative effect of phenolics. Similarly, hydrolytic activity of a commercial enzyme cocktail Cellic Ctec2 was enhanced in the presence of low concentrations of phenolics. [ABSTRACT FROM AUTHOR]

This document is a compilation of references related to the synthesis, characterization, and applications of activated carbon derived from various biomass sources. The references cover a wide range of topics, including the removal of pollutants from water, CO2 capture, and the use of activated carbon in supercapacitors. The papers provide valuable insights into different activation methods, pore structure development, and the performance of biomass-based activated carbon in various applications. Overall, the references highlight the potential of biomass-based activated carbon as a sustainable and effective material for environmental and energy-related applications. [Extracted from the article]

Overcoming key bottlenecks for 2G ethanol production, such as the most suitable biomass pretreatment, process layout, and appropriate microorganism, is crucial to achieve a technically and economically feasible technology. The consolidated bioprocessing (CBP) is an approach that embodies one single step of enzyme production, biomass hydrolysis, and sugars fermentation. In this work, the CBP using S. cerevisiae AC14, a recombinant strain capable of secreting 7 different lignocellulosic enzymes and ferment xylose and glucose, was investigated in synthetic medium (cellobiose, corncob xylan, glucose, and xylose) and in industrial medium consisting of the solid fraction of hydrothermally pretreated sugarcane bagasse and its liquor. Results obtained were promising, with ethanol productivity of 4.46 g/L/h and complete hydrolysis of cellobiose and corncob xylan. In real industrial medium, 1.86 g/L/h of ethanol was reached, with partial conversion of both solid and liquid fractions. Further strategies to enhance enzymes access to complex substrates can improve process feasibility. [ABSTRACT FROM AUTHOR]

Solid and liquid fractions of hydrothermally pretreated sugarcane bagasse (SCB) were simultaneously used as substrate of a novel continuous compartmentalized reactor. The effect of four (56, 42, 28, and 14 h) hydraulic retention time (HRT) and three (0.5, 3.0, and 9.0 g L-1) chemical oxygen demand (COD) levels were evaluated on hydrogen (H2) and organic acids production. Higher H2 production and yield (686 mL and 1.63 mol mol-1 carbohydrate, respectively) were obtained under an HRT of 28 h, probably due to the Clostridium and Thermoanaerobacterium metabolisms, which accounted for almost 60% of the microbial relative abundance. Under lower and higher HRT (14 and 56 h, respectively) lactic acid prevailed without hydrogen production. Other value-added chemicals such as citric, valeric and caproic acids were also obtained according to the HRT. From the functional point of view, enzymes from the glycoside hydrolases group (GHs) potentially performed important roles in the lignocellulosic biomass bioconversion.

Hydrothermal pretreatment (HTP) can be used to decompose the sulfadiazine (SDZ) during continuous anaerobic digestion (AD) of pig manure. This study aims to explore the effect of HTP on the SDZ degradation and performance of AD system. Pig manure with SDZ was taken as the research object. A comparison was made on the degradation regular, SDZ paths and products, as well as the gas production performance of pig manure with/without HTP during AD. The results showed that the HTP (150 °C) significantly increased the comprehensive removal rate of SDZ in the mesophilic continuous AD reactor (P <0.05), particularly from 40.5%~58.5% to 54.4%~75.2%. Moreover, the biodegradation paths of SDZ were inferred through intermediate degradation products, including SDZ hydrolysis, hydroxylation, thiodeoxidation, amino oxidation, nitroation, amidation and pyrimidine ring cleavage. HTP enhanced the degradation products and paths of SDZ, biodegrade SDZ from different degradation paths, and the removal rate of SDZ. There were four paths of degradation in pig manure with HTP, while there was only one degradation path without HTP. In terms of AD performance, the system was stabilized after 25 days, the daily gas production in the R0 reactor was stable at 5.14 L/d, and the cumulative VS gas production rate was 16.64 L/g; In the R0h reactor, the daily gas production was stable at 6.89 L/d, and the cumulative VS gas production rate was 22.31 L/g. The daily biogas yield of the reactor and the volume production rate increased by about 34.05% (P<0.05), and 34.00%, respectively, after stable operation with HTP. There was little difference in the methane content between the two reactors after two SRTs. The average contents of methane in R0 and R0h reactors were 61% and 59%, respectively. Thus, the AD process was stable in the two groups of reactors over the whole operation stage, according to the biogas production rate and methane content. The degradation of organic matter was also enhanced for the high concentration of VFAs after HTP. The substrate was provided for the subsequent stage of methane production, in which the acetic acid content accounted for 25.3%~46.1%. In addition, the microbial communities showed that Firmicutes and Bacteroidota were the dominant phylum bacteria in the reactors during anaerobic fermentation. Their relative abundance was beneficial to the degradation of antibiotics. A comparative analysis was also made on the microbial community at the class level. It was found that Clostridia and Bacteroidia were the main microorganisms in the two reactors. The relative abundance of Proteiniphilum increased after HTP. The full hydrolysis of pig manure was also realized for the better performance of methane production. Meanwhile, it was found that Syntrophomonas and Sedimentibacter were highly correlated with the degradation of SDZ, and the relative abundance of Sedimentibacter after HTP was significantly higher than that without HTP, indicating the better degradation of antibiotics. Therefore, the HTP coupled with the AD process can be expected to simultaneously improve the degradation of SDZ and AD performance, particularly for the ecological safety of biogas liquor. [ABSTRACT FROM AUTHOR]

Papyrus (Cyperus papyrus L.) is a lignocellulosic plant suitable for many applications when properly pretreated. This study explores the potential of a two-stage pretreatment (combining hydrothermal and chemical methods) on the characteristics of cellulose fibers derived from papyrus. One-stage and two-stage pretreatments were compared, utilizing sodium hydroxide (NaOH) and ferric chloride (FeCl3) chemical solutions at a 3% (w/v) concentration. Chemical pretreatment was employed for one-stage processing, while hydrothermal pretreatment was introduced prior to chemical pretreatment. As the liquid hot-water process intensified, significant changes in chemical composition and morphology occurred. Hydrothermal pretreatment partially eliminates hemicelluloses and lignin, while increasing the cellulose content and enhancing fiber crystallinity. Following the pulping and bleaching stages, it was determined that the FeCl3-based two-stage pretreatment exhibited the greatest potential for cellulose recovery and hemicelluloses and lignin removal, yielding the highest crystallinity index. [ABSTRACT FROM AUTHOR]

Lignocellulosic biomasses have a very important role as raw materials to produce biobased chemicals. However, a sustainable, efficient, and economically competitive way to convert lignocellulosic biomass into these chemicals has still not been achieved. This study is related to the selective separation and conversion of birch wood C5 carbohydrates into furfural during the H3PO4–NaH2PO4-catalyzed hydrothermal pretreatment simultaneously preserving cellulose in the lignocellulosic leftover for glucose production by the enzymatic hydrolysis. The ratio of H3PO4–NaH2PO4 in the catalyst solution was changed (3:0, 2:1, 1:1, and 1:2). Results show that around 64.1 to 75.9% of available C5 carbohydrates were converted into furfural. The results of birch wood lignocellulosic leftover chemical composition analysis show that cellulose losses during the pretreatment stage did not reach more than 10% of the initial amount. Based on the enzymatic hydrolysis screening experiments, a suitable catalyst for pretreatment was selected and an in-depth study was carried out. Enzymatic hydrolysis experiments were organized based on the three-factor central composite face-centered design. The variable parameters were treatment time (24–72 h), enzyme load (10–20 U/g cellulose), and substrate amount in reaction media (10–20%). At optimal conditions, 49.9 ± 0.5% of available cellulose in lignocellulosic leftover was converted into glucose. [ABSTRACT FROM AUTHOR]

Objective The purpose of this study was to analyze the effect of the hydrothermal pretreatment of anaerobic digestion sludge cake (ADSC) of cattle manure on the solubilization of organic matter and the methane yield to improve the anaerobic digestion efficiency of cattle manure collected from the sawdust pens of cattle. Methods Anaerobic digestion sludge cake of cattle manure was thermally pretreated at 160°C, 180°C, 200°C, and 220°C by a hydrothermal pressure reactor, and the biochemical methane potential of ADSC hydrolysate was analyzed. Methane yield recovered by the hydrothermal pretreatment of ADCS was estimated based on mass balance. Results The chemical oxygen demand solubilization degree (CODs) of the hydrothermal hydrolysate increased to 63.56%, 67.13%, 70.07%, and 66.14% at the hydrothermal reaction temperatures of 160°C, 180°C, 200°C, and 220°C, respectively. Considering the volatile solids content obtained after the hydrothermal pretreatment, the methane of 10.2 Nm3/ton-ADSC was recovered from ADSC of 1.0 ton, and methane yields of ADSC hydrolysate increased to 15.6, 18.0, 17.4, and 17.2 Nm3/ton-ADSC. Conclusion Therefore, the optimal hydrothermal reaction temperature that yielded the maximum methane yield was 180°C based on mass balance, and the methane yield from cattle manure containing sawdust was improved by the hydrothermal pretreatment of ADSC.

This study focused on the co-fermentation of food waste and tissue paper to produce ethanol, which will eliminate the need for additional nitrogen sources and nutrients, thereby reducing production costs. In response to the inhibitory effect of the high concentrations of glucose present in mixed-substrate hydrolysates on xylose fermentation, a co-fermentation process using Saccharomyces cerevisiae and Candida shehatae was proposed. This approach reduced the fermentation time by 24 h, increased the xylose utilization rate to 88%, and improved the ethanol yield from 41% to 46.5%. The impact of external conditions and corresponding optimization were also analyzed in this process. The optimum conditions were a 1:3 ratio of Saccharomyces cerevisiae to Candida shehatae, a pH of 5, and shaking at 150 r/min, and by employing dynamic temperature control, the ethanol production was increased to 21.98 g/L. Compared to conventional processes that only use Saccharomyces cerevisiae, this method enhanced the ethanol yield from 41% to 49%.

Platanus orientalis Linn is widely distributed as a famous street tree, and its fallen leaves are a rich biomass resource. The fallen leaves of Platanus orientalis Linn (FLPOL) can be resourcefully treated by generating biogas through anaerobic digestion. This study aimed to assess the anaerobic digestion (AD) performance of FLPOL under different hydrothermal pretreatment (HTP) conditions (solid–liquid ratio 2–10%, residence times 0.5–2.5 h, and temperatures 120–200°C). The solid–liquid ratio, residence time, and temperature determined by energy balance calculation were 6%, 2.0 h, and 180°C, respectively, and the energy balance was 1.823 kJ/g biomass. Under these conditions, the methane yield of the process water was 56.85 mL/g·VS. The methanogenic potential, hydrolysis rate, maximum methanogenic rate, and the lag period obtained by the Fitzhugh first-order kinetic model and the modified Gompertz model were 101.803 mL/g·VS, 0.130 d−1, 14.207 mL/(g·VS·d) and 1.332 d, respectively. The research results suggest that HTP has an important role in promoting the large-scale AD application of FLPOL. [ABSTRACT FROM AUTHOR]

The present study aimed to evaluate an available process for production of ferulic acid (FA) and p-coumaric acid (pCA) that could be potentially used as functional agents in food processing. The hydrothermal pretreatment combined with enzymatic hydrolysis (HP-CEH) was explored for efficient production of phenolic acids from reed straws. The results indicated that HP-CEH significantly increased production of phenolic acids. The recovery yield of ferulic acid and p-coumaric acid was respectively found to be 0.69 and 0.81 mig/g dry reed straw when performed by HP-CEH for 16 h. The degradation of hemicellulose, lignocellulose and lignin, and disruption of cell walls or cellulose fibers contributed to phenolic acids production from reed straws. Moreover, the scavenging activity of hydroxyl radical and DPPH radical of the phenolic acids extracted by HP-CEH was respectively obtained to be 77.32% and 86.77%. [ABSTRACT FROM AUTHOR]

The recalcitrance nature of agricultural and forest wastes limits their enzymatic degradation and reduces biogas production. The objective of this study is to compare the effects of H2O2 + NaOH and H2O2 + H3PO4 as combined pretreatments and H3PO4, NaOH and H2O2 as individual ones on lignin removal and structural changes of spruce wood wastes. The results showed that H2O2 and NaOH with a lignin removal rate of 28.43 and 12.49%, respectively were the most powerful substances. The lignin removal power of H3PO4 in combination with H2O2 (11.20%) and NaOH (12.49%) increased compared to single H3PO4 (1.58%). The Hydrogen Bond Intensity crystalline index of all pretreatments was lower than the untreated samples. The amount of Cross-Linked Lignin ratio in H2O2 was higher than other pretreatments. Overall, although H2O2 and NaOH were the most powerful pretreatments in lignin removal, respectively, when placed in a combined pretreatment, their degradation power (7.65%) was even lower than individual treatments for each. [ABSTRACT FROM AUTHOR]

Four parameters affecting hydrothermal pretreatment (HTP) of municipal sludge prior to anaerobic digestion and fermentation were investigated. Partial factorial design including several key HTP parameters at two distinct levels, including temperature (170 and 190 °C), retention time (RT) (10 and 30 min), pH (4 and 10), and solid content (SC) (4% and 16%), were studied. Further, the impact of HTP parameters on mesophilic and thermophilic fermentation was explored and compared. Results revealed a significant effect of all HTP parameters on COD solubilization, VFA, and methane yield. There were correlations between HTP parameters and process responses such as VFA yield and methane yield. HTP was found to increase COD solubilization and VFA production between 15 and 20% during thermophilic fermentation in relation to mesophilic treatment. All parameters, including SC, temperature, pH, and RT, were important contributing factors affecting methane production during anaerobic digestion. The highest methane production yield of 269 mL CH4/g TCOD added was observed at the highest SC (16%) and pH (10) and at the lower temperature (170 °C) and RT (10). HTP is expected to be combined with other intensification routes to treat waste with high solid contents improving the fermentation and anaerobic digestion processes. [ABSTRACT FROM AUTHOR]

Anaerobic digestion and fermentation processes in wastewater sludge treatment are limited by several factors, including the slow breakdown of complex organic matter and solubilization of solids. In this study, thermochemical pretreatment of thickened waste activated sludge using high temperature (>170 °C) was investigated to understand the impact of the pretreatment on the volatile fatty acids (VFA) production and its fractions during the fermentation process. Furthermore, the influence the thermochemical pretreatment on sludge disintegration and methane recovery was investigated. A range of acidic and alkaline conditions over the pH range of 4.5–10 was examined. Sludge (pH adjusted) was exposed to hydrothermal pretreatment (HTP) at a temperature of 170 °C for 30 min. Pretreated samples were then subjected to batch fermentation and methane potential tests which revealed that acidic and alkaline conditions resulted in increased sludge solubilization during HTP. Acidic conditions were associated with a higher VFA production yield of up to 185 mg chemical oxygen demand/g total chemical oxygen demand. Alkaline conditions led to a higher methane production yield where the maximum yield (276 mL CH4/g total chemical oxygen demandadded) was found to occur at pH 10. Therefore, alkaline sludge used for fermentation has shown technical and economic feasibility for sludge carbon recovery. HIGHLIGHTS Effect of pH on thermal pretreatment, fermentation and digestion was investigated.; Acidic and alkaline pH had positive effect on thermal pretreatment performance.; Acidic conditions resulted in higher volatile fatty acids production.; Alkaline conditions resulted in higher methane production.;

The hydrothermal pretreatment (HTP) characteristics and the fate of phosphorus (P) and anaerobic digestion (AD) performance of dewatered sewage sludge (DSS) were investigated at different hydrothermal conditions. The maximum methane yield reached 241 mL CH4/g COD when the hydrothermal conditions were 200 °C-2 h-10% (A4), and the yield was 78.28% higher than that without pretreatment (A0) and 29.62% higher than that of the initial hydrothermal conditions (A1, 140 °C-1 h-5%). Proteins, polysaccharides, and volatile fatty acids (VFAs) were the main hydrothermal products of DSS. 3D-EEM analysis revealed that tyrosine, tryptophan proteins, and fulvic acids decreased after HTP, but the content of humic acid-like substances increased, and this phenomenon was more noticeable after AD. Solid-organic P was converted into liquid-P during the hydrothermal process, and nonapatite inorganic P was converted into organic P during AD. All samples achieved positive energy balance, and the energy balance of A4 was 10.50 kJ/g VS. Microbial analysis showed that the composition of the anaerobic microbial degradation community changed as the sludge organic composition was altered. Results showed that the HTP improved the anaerobic digestion of DSS. [ABSTRACT FROM AUTHOR]

Biomass pelletizing treatment can enhance the energy density and decrease the transportation and storage cost of the resulted fuel. In the study, wood sawdust (WS) pretreated by hydrothermal and hydrothermal oxidation process at 170～260 ℃ was used to prepare biomass pellet. The effects of the hydrothermal and hydrothermal oxidation pretreatment on the mechanical property and combustion performance of the wood pellet were investigated using Van Soest method, X-ray diffraction (XRD), thermogravimetric analysis (DTG), industrial analysis and oxygen bomb calorimeter. The results showed that the hemicellulose and amorphous cellulose decomposed rapidly at 170～230 ℃, the crystalline cellulose began to decompose at 260 ℃ and the relative mass fraction of lignin gradually increased with an increase of temperature because of the decomposition of hemicellulose and cellulose after hydrothermal pretreatment. While the hemicellulose was completely decomposed before 230 ℃ and the temperature of crystal cellulose decomposition was advanced to 230 ℃ after hydrothermal oxidation pretreatment. Compared with hydrothermal pretreatment, the relative mass fraction of lignin increased more obviously. The pyrolysis characteristics of wood sawdust pretreated by hydrothermal and hydrothermal oxidation were analyzed. It was found that the samples after hydrothermal pretreatment, the height of hemicellulose pyrolysis peak gradually decreased and completely disappeared at 230 ℃. The pyrolysis peak of cellulose first increased and then decreased with the increase of pretreatment temperature, and the peak of lignin was positively correlated with the increase of pretreatment temperature. Compared with hydrothermal pretreatment, with the increase of hydrothermal oxidation temperature, the pyrolysis peak of hemicellulose disappeared obviously； the pyrolysis peak of cellulose showed a downward trend and the peak was significantly advanced while the pyrolysis peak of lignin continued to rise. The hydrothermal and hydrothermal oxidation pretreatments can greatly enhance the mechanical properties of the resulted biomass pellets compared with that of the unpretreated WS pellets. After hydrothermal pretreatment, the apparent density increased from 1 110.2 to 1 381.6 kg/m3 and the compressive strength increased from 16.2 to 38.9 MPa at 230 ℃, which increased by 24.4% and 140.1%, respectively. The apparent density increased to 1 429.2 kg/m³, and the compressive strength increased to 41.1 MPa at 200 ℃ after hydrothermal oxidation pretreatment, which increased by 28.7% and 153.7%, respectively. Compared with hydrothermal pretreatment, hydrothermal oxidation pretreatment can promote the degradation of the hemicellulose and cellulose contained in WS and enhance its mechanical property, thus, the pretreatment intensity can be alleviated. In the process of hydrothermal and hydrothermal oxidation pretreatment, the crystallinity of samples increased first and then decreased with the increase of pretreatment temperature. After hydrothermal pretreatment, the crystallinity of cellulose increased from 41.4% to 50.7% at 230 ℃. The crystallinity of cellulose reached the maximum value at 200 ℃ after hydrothermal oxidation pretreatment which was higher than the maximum value of hydrothermal pretreatment. When the temperature of hydrothermal oxidation pretreatment rose to 260 ℃, the crystallinity finally decreased to none. The mechanical property of the pellets is found to be positively correlated with the change trend of the cellulose crystallinity and the crystalline cellulose is the key component for the biomass pelletizing process. The hydrothermal and hydrothermal oxidation pretreatments can significantly enhance the heating value, the comprehensive combustion characteristic index and combustion stability index of the resulted WS pellets. Compared with hydrothermal pretreatment, the hydrothermal oxidation pretreatment can promote the carbonization degree of the resulted samples. In sum, the quality and combustion performance of the fuel pellet can be improved by the pretreatment. These results can supply some support for the production of good quality WS pellets. [ABSTRACT FROM AUTHOR]

BACKGROUND: Chicken feather (CF), pig bristle (PB), and pig hoof (PH) are substantial keratin wastes from slaughterhouses. They are generated in large quantity, are almost totally unexploited protein resources, and are potential substrates for value‐added products. RESULTS: In this study, Thermoactinomyces vulgaris TK1‐21 showed a good ability to produce keratinases for the degradation of all three keratin wastes within 5 days at pH 8.5 and 45 °C. Maximum keratinase activities of 5.72, 4.21, and 4.89 U mL−1 were obtained for CF, PB, and PH, respectively. T. vulgaris TK1‐21 secreted two types of extracellular enzymes (keratinase_TK1‐21), which were purified and characterized as thermitase (keratinase‐I) and carboxypeptidase T (keratinase‐II) with estimated molecular weights of 28 and 36 kDa, respectively. Dialyzed crude keratinase_TK1‐21 could efficiently hydrolyze the hydrothermally treated CF, PB, and PH into keratin hydrolysate (KH). Soluble protein concentrations of 6.94, 3.87, and 6.32 mg mL−1 were obtained at pH 9.0, 55 °C, and 72 h, which were three times higher than those of untreated substrates. In addition, this hydrothermal–enzymatic method showed high KH productivity (60–70%) with a production cost of 16.24 USD kg−1. The ferric‐reducing antioxidant power assay and radical scavenging activities of KH derived from CF, PB, and PH were 19–42, 2.5–4.9, and 608–1314 μmol TE gprotein−1. Bioplastic starch blended with these KHs showed improved tensile strength (2.55–4.40 MPa) and elongation at break (40–54%) when compared to bioplastics without KH blending. CONCLUSIONS: Based on our results, we suggest an alternative valorization approach with techno‐economic feasibility for keratin waste bioconversion into a potential active ingredient for bioplastics via hydrothermal–enzymatic processing. © 2023 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Hydrogen (H2) production, acidification performance, and kinetic modeling of dark fermentation (DF) of food waste (FW) with hydrothermal pretreatment (HTP) and addition of oyster shell (OS) were investigated in this study. A cumulative H2 yield of 52.5 mL g VS−1 with an improvement of 147.9% was obtained in the DF of FW with HTP and the addition of OS. Acidification performance analysis showed an upward trend of volatile fatty acids (VFAs) from the start-up to day 3 or day 6, and then an opposite trend was observed for the remaining time of the DF process. Butyric and acetic fermentation dominated DF. Moreover, the DF process could be well fitted by the five kinetic models, and its quantitative rank was first-order > monomolecular > modified Gompertz > logistic > Fitzhugh. Correlation analysis indicated that the H2 yield was affected by both pH and VFAs. This study demonstrated a novel strategy by combining HTP and OS addition for enhancing H2 production from FW using DF. [ABSTRACT FROM AUTHOR]

Hydrothermal pretreatment (HPT) followed by anaerobic digestion (AD) is an alternative for harvesting energy and removing organic contaminants from sewage sludge and animal manure. This study investigated the use, in an energetically sustainable way, of HPT and AD, alone or combined, to produce methane and remove tylosin and antimicrobial resistance genes (ARG) from poultry litter (PL). The results showed that HPT at 80 °C (HPT80), followed by single-stage AD (AD-1S), led to the production of 517.9 ± 4.7 NL CH4 kg VS−1, resulting in 0.11 kWh kg PL−1 of electrical energy and 0.75 MJ kg PL−1 of thermal energy, thus supplying 33.6% of the energy spent on burning firewood at a typical farm. In this best-case scenario, the use of HPT alone reduced tylosin concentration from PL by 23.6%, while the process involving HPT followed by AD-1S led to the removal of 91.6% of such antibiotic. The combined process (HPT80 + AD-1S), in addition to contributing to reduce the absolute and relative abundances of ARG ermB (2.13 logs), intI1 (0.39 logs), sul1 (0.63 logs), and tetA (0.74 logs), led to a significant removal in the relative abundance of tylosin-resistant bacteria present in the poultry litter. [ABSTRACT FROM AUTHOR]

Rice straw (RS) is the most potentially renewable agricultural waste resource widely distributed in nature. Considering the complex recalcitrant structure and components of RS, three pretreatment methods, including high-temperature hydrothermal, medium-temperature microwave, and low-temperature cryocrushing pretreatment were performed. The components and structure of RS residues were examined and analyzed after the pretreatments. Pretreatment with hydrothermal yielded the lowest rice straw recovery (59.0%); after being pretreated at 180 °C for 10 min, the hemicellulose recovery was only 14.1%, and the removal efficiency of lignin was the largest (41.3%), which was 32.2% and 18.8% higher than that achieved from cryocrushing and microwave pretreatment, respectively. Pretreatment with cryocrushing yielded the highest recovery rates of rice straw (92.9%), hemicellulose and cellulose (88.8% and 90.4%, respectively). Results of scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and the analysis of specific surface area and apertures demonstrated that all three pretreatments could effectively disrupt the structure of RS and reduce its cellulose crystallinity. The three pretreatments were found to enhance the hydrodepolymerization of RS residues. Furthermore, cryocrushing pretreatment yielded the highest cellulose conversion rate (56.8%), and the yields of glucose, xylose, and arabinose were 29.6%, 56.2%, and 17.8%, respectively. Apart from the use of acids and enzymes, hydrodepolymerization of RS was among the few methods that can effectively degrade cellulose, presenting an ideal solution for the degradation of biomass. [ABSTRACT FROM AUTHOR]