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Hydrothermal liquefaction is a new, sustainable pathway to generate biogenic liquids from organic resources. The technology is compatible with a wide variety of resources such as lignocellulosic resources, organic waste, algae, and sewage sludge. The chemistry is complex and predictions of yields are notoriously difficult. Understanding and modeling of hydrothermal liquefaction is currently mostly based on a simplified biochemical analysis and product yield data. This paper presents a large dataset of 2439 experiments in batch reactors that were extracted from 171 publications in the scientific literature. The data include biochemical composition data such as fiber content and composition, proteins, lipids, carbohydrates, and ash. The experimental conditions are recorded for each experiment as well as the reported yields. The objective of this paper is to make a large database available to the scientific community. This database is analyzed with machine‐learning tools. The results show that there is no consensus on the analysis techniques, experimental procedures, and reported data. There are many inconsistencies across the literature that should be improved by the scientific community. Machine‐learning tools with a large dataset allow the generation of reliable yield production tools with a large application field. Given the accuracy of the data, the overall precision of prediction in an extrapolation to new results can be expected to be around 10%. [ABSTRACT FROM AUTHOR]

The main objective of the manuscript is to investigate mild hydrotreatment upgrading of hydrothermal liquefaction biocrude to improve its stability and energy content. To that end, biocrude hydrotreatment was performed, exploring three different operating windows in order to examine the effect of reaction temperature and hydrogen supply on deoxygenation reactions. A typical NiMo/Al2O3 hydrotreating catalyst was utilized while the experiments were performed in a continuous-flow TRL 3 hydrotreatment plant. The results show that the resulting product has a higher carbon content as compared to the raw feed. The oxygenated compounds were removed, leading to a product with almost zero oxygen and water content, with high energy density. The reaction pathways during the hydrotreatment upgrading of biocrude were investigated via GC-MS analysis and presented in detail in the manuscript. In general, the hydrotreating process was able to improve the quality of the initial biocrude, allowing easier handling and storing for further upgrading, or to be used as an intermediate refinery stream. [ABSTRACT FROM AUTHOR]

How to dispose heavy metal-rich plant harvest in a green, efficient and resource ・ based manner is an urgent technical problem for the industrial development of phytoremediation of heavy metal・containinated soil・ Using ramie as raw material and water as reaction solvent, the effects of reaction temperature, reaction time and acid-base catalysts on the oil yield and heavy metal migration of ramie were investiga・ ted. The results showed that the highest yield of ramie liquefied bio-oil was 20. 86% at 275 °C, 30 min and 5% HCOOH, and 让s calorific value was 30. 68 MJ/kg・ The organic components of bio・oil in blank group were mainly composed of alcohols, hydrocarbons, acids, ketones and N・containing compounds・ The contents of hydrocarbon and ester compounds in liquefied bio-oil in HCOOH group were increased, while the contents of hydrocarbon, alcohols and acids in bio・oil in NaCO2 group were decreased・ In addition, more than 85% of heavy metals (Cd, Pb, Cu and Cr) are retained in the solid phase residue, while As is mainly transferred to the aqueous phase, and the heavy metal content in bio-oil is less than 4%. [ABSTRACT FROM AUTHOR]

Mass Sargassum inundations have created opportunities for readily available biomass to be used as a crop enrichment application. However, the heavy metal contents of Sargassum pose serious concerns for crop administration and subsequent human consumption. Hydrothermal processing can break the feedstock components, allowing heavy metals to be partitioned, through the utilisation of high temperatures and pressures. As a result, seemingly nutrient-rich phases can be produced. Elemental analyses showed that Sargassum-derived fractions contain important macro- and micronutrients for plants, particularly ammonium, orthophosphate, and potassium, making them potential nutrient sources for plant growth. To date, no research has investigated the plant growth potential of hydrothermally processed Sargassum products from a bioavailability or biotoxicity perspective. We seek to determine if the aqueous phase products derived following Sargassum processing by hydrothermal carbonisation and liquefaction are toxic to higher plants, and if they can support plant growth. Aqueous phase products in ≥1% concentrations inhibit root growth and lateral root formation in Arabidopsis plants, likely from the presence of inhibitory compounds. However, aqueous phase products in ≤0.1% concentrations paired with an established nutrient mix may provide improved leaf and root growth. Both HTC and HTL were capable of eliciting improved foliage growth, while only HTC induced improved root growth. Conclusively, aqueous phase products lack nutrient potency to allow high dilutions for fertiliser application on their own and may contain inhibitory compounds that deter plant growth at high concentrations. However, they might have a purpose as an additive extract. The recovery of important elements needed for plant growth draws a promising path for future applications of hydrothermal processing with different feedstocks. [ABSTRACT FROM AUTHOR]

This study investigates the impact of NaF/Al2O3 catalysts on hydrothermal liquefaction (HTL) of cellulose. Three catalysts with varying NaF loadings were synthesized and characterized using XRD, FT-IR, BET, SEM, SEM–EDX, and SEM–EDS. HTL reactions were conducted at 300, 325, and 350 °C for 30 min. Elemental, GC–MS, FT-IR and 1H NMR analyses were performed on the liquid products. Results reveal that NaF/Al2O3 catalysts effectively enhance liquid product yield and generate high-energy-value products. NaF-2 and NaF-3 exhibit superior performance in fuel-specific liquid product yield, with increased aliphatics and reduced oxygen compounds. These catalysts display higher carbon content, lower oxygen-to-carbon ratios, and higher heating values, suggesting the production of bio-oils with favorable fuel properties and superior energy values. The findings contribute to understanding catalyst performance in biomass liquefaction, informing efforts to enhance process efficiency and sustainability. Optimum HTL conversion of cellulose occurs with 30% NaF loading. [ABSTRACT FROM AUTHOR]

This research study explores the influence of NaF/Al2O3 catalysts on the process of hydrothermal liquefaction (HTL) of Crambe Orientalis. Three distinct catalysts were prepared and examined through a multitude of methodologies including FT-IR, BET, XRD and SEM/EDX/EDS. The HTL were made at temperatures ranging from 275 to 350°C for a duration of 0 to 60 minutes. The liquid products obtained were subjected to elemental, GC-MS, FT-IR, and1 H NMR analyses. The findings of this study demonstrate that NaF/Al2O3 catalysts effectively enhance the yield of liquid products. The liquid products that were obtained displayed an exceptionally elevated carbon content, with a maximum value of 80.97% achieved at a temperature of 350°C. These liquid products exhibit superior heating values (HHV), which vary between 37.64 and 29.31 MJ/kg. The catalysts demonstrated efficacy in enhancing the liquid product yield, characterized by a heightened proportion of aliphatic compounds and a diminished ratio of oxygen constituents. It was determined that the obtained catalysts may have the potential to obtain liquid products with high carbon content and energy values. [ABSTRACT FROM AUTHOR]

In recent years, hydrothermal liquefaction (HTL) has gained attention as a means of enhancing and increasing the production of biofuels from biomass. Co-HTL involves the simultaneous processing of two or more feedstocks, with the potential for interactions that can affect the overall yield and quality of the resulting biofuels. This study investigates the bio-crude yield, chemical composition, and energy content of bio-crudes obtained through formic acid-assisted hydrothermal liquefaction of combined digested sewage sludge (DSS) and lignocellulose (LC). The bio-crude yields are in the range of 26.8–58.9 wt%, with a higher heating value (HHV) of approximately 32 MJ/kg. The best experiment shows that mixtures with more DSS and high levels of process condition variables (350 °C, formic acid present, and 50 wt% EtOH) give high bio-crude yields with a maximum value of 58.9 wt%. For comparison, pure DSS and LC run at these process conditions resulted in a bio-crude yield of 52.5 wt% and 48.3 wt%, respectively. Partial least squares (PLS) regression reveals a synergistic effect from mixing the feedstocks, as the quadratic term of the regression equation for mixture ratio shows a negative coefficient. GC–MS data show that combining feedstocks results in the formation of new compounds, mostly phenols, that are not present in the bio-crudes from the separate feedstocks. Thus, combining feedstocks will not only increase the resource availability for hydrothermal liquefaction and streamline the process but will also increase the overall production of bio-crude with its synergistic effect. [ABSTRACT FROM AUTHOR]

Hydrothermal liquefaction (HTL) represents a beacon of scientific innovation, which unlocks nature's alchemical wonders while reshaping the waste-to-energy platform. This transformative technology offers sustainable solutions for converting a variety of waste materials to valuable energy products and chemicals—thus addressing environmental concerns, inefficiencies, and high costs associated with conventional waste-management practices. By operating under high temperature and pressure conditions, HTL efficiently reduces waste volume, mitigates harmful pollutant release, and extracts valuable energy from organic waste materials. This comprehensive review delves into the intricacies of the HTL process and explores its applications. Key process parameters, diverse feedstocks, various reactor designs, and recent advancements in HTL technology are thoroughly discussed. Diverse applications of HTL products are examined, and their economic viability toward integration in the market is assessed. Knowledge gaps and opportunities for further exploration are accordingly identified, with a focus on optimizing and scaling up the HTL process for commercial applications. In conclusion, HTL holds great promise as a sustainable technology for waste management, chemical synthesis, and energy production, thus making a significant contribution to a more sustainable future. Its potential to foster a circular economy and its versatility in producing valuable products underscore its transformative role in shaping a more sustainable world. [ABSTRACT FROM AUTHOR]

Hydrothermal liquefaction (HTL) is a green technology for biocrude production from algae. The global reaction kinetic, component additivity model (CAM), and response surface methodology (RSM) of HTL from high-lipid microalgae (Aurantiochytrium sp.) were evaluated. Lipids, proteins, and carbohydrates of the microalgae cell reacted at different rates and produced the aqueous phase, bio-oil, and gas phase in the kinetic model. Performing global kinetic modelling, understanding the reactions, and the performance of algae for biofuel production by HTL were the main ideas and novelty behind this work. Also, the predictive ability of bio-oil yield was examined by kinetic, CAM, and RSM approaches. MATLAB was utilized to solve the system of ordinary differential equations and calculate the optimum values for Arrhenius kinetic parameters by minimizing the least-square differences between model and experimental yields. R-squared of 0.997 showed that the global kinetic modelling provides a great prediction of bio-oil yields. Activation energies were calculated at 32.31, 38.50, and 46.99 kJ/mol for the conversion of lipids, proteins, and carbohydrates to bio-oil. Furthermore, a maximum bio-oil yield of 53.43 wt% was predicted at 800 K in 2 min. Also, the result of bio-oil prediction by global kinetic modelling compared to CAM and RSM equations. In comparison with the CAM model, the RSM equations showed better adaption with the bio-oil yield at 350 °C and 40 min. However, the kinetic model had the best potential for bio-oil predicting yields of Aurantiochytrium sp. because of the minimum mean absolute error of 2.078%. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis and characterization of ion-dopped K/feldspar catalysts. • Optimisation of Fe/K-feldspar catalysed hydrothermal liquefaction of AD digestate. • Recyclability and selectivity of the WI-10 catalyst were identified. • Stability of the phenol-rich bio-oil was demonstrated. • Utilisation of the HTL solid residue as electrode in Li-ion battery was probed. Sustainable implementation of thermochemical conversion of biomass to targeted products is dependent on innovations in catalyst design and tuning of structure–property relationships. This study details the use of potassium feldspar (K-feldspar) as a support doped with different iron (Fe) concentrations via wet impregnation (WI) method for hydrothermal liquefaction (HTL) of sugarcane bagasse anaerobic digestate. The Fe/K-feldspar supported catalysts were synthesized and characterized using X-ray diffraction, Inductively Coupled Plasma Optical Emission spectroscopy, Brunauer-Emmet-Teller and Scanning Electron Microscopy analytical methods. Amongst all the catalysts, K-feldspar dopped with 10 wt% Fe (WI-10) was more effective, producing 51.2 wt% bio-crude. The catalyst's activity has been related to the balanced proportion of the microcline: sanidine: haematite (2.8:3.3:1) phases of Fe present on the catalyst, the surface area (porosity), and the surface functionality, thus conferring desirable activity properties. In addition, the WI-10 catalyst had a better selectivity towards substituted phenols that can potentially be used for higher-value applications such as the production of Nylons 6 and 66, and bioplastics. The bio-oil produced with WI-10 has also been demonstrated to be highly stable. The catalyst was reusable up to four times maintaining moderate catalytic performance, and a simple regeneration protocol was shown to restore the activity of the catalyst. The resulting solid residue also exhibited promise as a viable material for use in electrodes for Lithium-ion batteries (LiB). Therefore, this research has demonstrated a promising and sustainable resource recovery strategy for valorising wet biomass wastes into streams of useful products for valuable chemical production and energy application. [ABSTRACT FROM AUTHOR]

The conversion of biomass to biofuels as a renewable energy source is continuously gaining momentum due to the environmental concerns associated with using fossil fuels. Biomass is a cost-effective, long-term natural resource that may be converted to biofuels such as biodiesel, biogas, bio-oil, and biohydrogen using a variety of chemical, thermal, and biological methods. Thermochemical processes are one of the most advanced biomass conversion methods, with much potential and room for improvement. Among various thermochemical processes, hydrothermal liquefaction (HTL) is a promising technology that can convert higher water-content feedstocks into biofuel with significantly lower oxygen content and higher calorific value without requiring the biomass to be dried first. In HTL, temperature, pressure, residence time, catalyst, and solvent all play a vital role in bio-oil quality. This study provides a comprehensive review of the research and development on the effects of catalysts and the need to optimise existing catalysts for optimum biomass conversion into high-value bio-oil and other products. The catalyst of interest is ZSM-5, a heterogenous catalyst that has been seen to increase the hydrocarbon content and decrease oxygenated compounds and other unwanted by-products. The use and modification of this catalyst will play a vital role in generating renewable and carbon-neutral fuels. [ABSTRACT FROM AUTHOR]

• Chemicals or solvent free green reduction of bauxite residue to Fe0 was carried out. • MSW was used as reducing agent through one-step solid-state heating method. • Fe0-based catalyst showed excellent catalytic activity for the valorization of MSW. • Improved yield and quality of biocrude was achieved than other iron-based catalysts. Industrial and municipal wastes remain significant sources of air, soil, and water pollution, thus causing adverse climate and health impacts. EU faces challenges in developing green recycling processes and reducing GHG emissions. Innovation in green catalysis is a key driver toward the fulfilment of these goals. This study demonstrated a single-step "Green Recycling" route by which different wastes e.g., industrial and bioorganic wastes are treated to produce biochar/Fe(0) (BC-Fe(0)) material. Typically, three different biomass namely organic fraction of municipal solid waste (biopulp), wheat straw (WS), and microalgae (MA) were used as green reducing agents for reducing bauxite residue (BR). Among all biomass, the high reduction potential of amino acids present in biopulp facilitated the synthesis of BC-Fe(0). BC-Fe(0) material acted as an effective catalyst for HTL of biopulp as the results showed the highest bio-crude yield (44 wt%) at 300 °C for 30 min with 10 wt% BC-Fe(0) loading (containing 2.5 wt% Fe). Furthermore, BC-Fe(0) also assisted in-situ hydrogenation and deoxygenation of chemical compounds present in the bio-liquid product, therefore bio-crude exhibited a higher H/C ratio (1.73) and lower oxygen contents (9.78 wt%) in comparison to bio-crude obtained without catalyst. However, Raw BR and reduced BR (RED) as catalysts showed no significant effect on the yield and oxygen content of bio-crude, which confirms the high catalytic activity of Fe(0) containing BC-Fe(0). Therefore, this study demonstrates the greener path for the one-step valorization of industrial and organic wastes, as an alternative to existing chemical and high temperature-based waste recycling and catalyst synthesis technologies. [ABSTRACT FROM AUTHOR]

Salix psammophila was converted to value-added chemicals in the presence of 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) and water by the hydrothermal liquefaction method. [Bmim]Cl acted as both liquefier and catalyst, while water served as both co-solvent and reactant. The optimal reaction parameters for the highest liquefaction yield were determined by an orthogonal experiment. The possibility of application of the recycled [Bmim]Cl was investigated. FT-IR spectra results of the fresh used, the firstly reused, and the secondary reused IL [Bmim]Cl confirmed the high stability of [Bmim]Cl. Moreover, an explanation of the possible liquefaction mechanism for S. psammophila was also provided. This study may provide fundamental data for S. psammophila conversion and application. [ABSTRACT FROM AUTHOR]

The two-stage conversion of blackcurrant pomace as an industrial wet-type waste is presented. Firstly, the pomace was hydrothermally processed in a single solvent (water) and a binary solvent system (water mixed with isopropanol) at low and moderate processing temperatures (225 and 275 °C, respectively). More specifically, the focus was put on investigating the effect of operating conditions on the change in the yield distribution of bioproducts, particularly solid hydrochar. Also, the composition, textural properties, and morphology of hydrochars were examined by DRIFT and XRD, low-temperature nitrogen adsorption, and SEM, respectively. In the subsequent step, the upgrading of resultant hydrochars via fast pyrolysis by using microscale techniques (pyrolysis coupled with gas chromatography and mass spectrometry) and thermogravimetric analysis was done. The studies proved that the proposed approach allows to obtain alternative products exhibiting high energy density (21.9–29.3 MJ kg−1) that could be useful for power and heat generation. It was found that conversion in the binary solvent system involves a noticeably deeper decomposition of the pristine biomass structure. Furthermore, through two-stage processing, it is possible to obtain value-added chemicals, such as hydrocarbons, with the potential to serve as advanced biocomponents or reagents for the chemical industry. [ABSTRACT FROM AUTHOR]

Hydrothermal liquefaction is the process of liquefying biomass in an aqueous medium under high pressure and temperature. This process is recognized as an environmentally friendly method for energy and material conversion of biomass. The selection of suitable catalysts for the HTL process is very important. Catalysts make it possible to obtain higher quality products by increasing the efficiency of the HTL process and at the same time to provide an environmentally friendly process by reducing energy consumption. In the study, NaF/Al2O3 was used as a catalyst in the hydrothermal liquefaction of Crambe orientalis plant. Three different catalysts were synthesized according to the amount of NaF loaded on the alumina. The reaction temperature was determined as 325 oC and the holding time was 30 minutes. The effect of the amount by weight of the catalysts on the elemental content of the liquid product was investigated. The highest energy value was obtained at a rate of 25% by weight in the presence of NaF-2 catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrothermal carbonization (HTC) and liquefaction (HTL) convert food waste to fuels. • HTC and HTL treated as distinct processes in literature yet no clear delineation exists. • Solvent extraction of secondary char shows abrupt transition between HTC, HTL. • Unlike liquids, solid hydrochar characteristics evolve continuously with temperature. • Less severe HTL conditions yield a higher quality biocrude. Despite the ability to perform both processes in the same reactor, hydrothermal carbonization (HTC) and hydrothermal liquefaction (HTL) are considered two distinct processes differentiated by their reaction temperatures. As temperatures increase from the less severe HTC range into the HTL regime, the product distribution progressively favors an organic bio-oil phase relative to solid hydrochar. Solvents are commonly used to extract bio-oil from the solid residues produced during HTL, and to separate the amorphous secondary char from the coal-like primary char of HTC hydrochars. This suggests secondary char is a HTL biocrude precursor. Lipid-rich food waste was hydrothermally processed between 190 and 340 °C, spanning HTC to HTL conditions. Higher temperatures produce more gas, less liquid, and similar amounts of a progressively less oxygenated hydrochars, suggesting a gradual transition from HTC to HTL. However, analyses of ethanol-separated primary chars and secondary chars tell a different story. While the primary char is progressively more carbonized with temperature, the secondary char composition sharply changes at 250 °C. That is, lipid hydrolysis begins around 220 °C, but proceeds rather completely at 250 °C and above. A lower HTL temperature reduces the energy cost of the hydrothermal process, yet enables full lipid hydrolysis into long chain fatty acids while minimizing recondensation and repolymerization of fatty acids onto the primary char and their subsequent amidation. This maximizes the conversion of lipid-rich feedstocks into liquid fuel precursors with up to 70 % energy recovery. [ABSTRACT FROM AUTHOR]

In this work, the process parameters of batch hydrothermal liquefaction of kitchen residue were optimized with the yield of bio-oil as reference, including reaction temperature, residence time and initial pressure. According to the experimental results, the bio-oil yield of kitchen residue was the highest (39.73%) under the reaction conditions of 6 MPa, 300 °C and 30 min. The elemental content and components of bio-oil were characterized by organic element analyzer and gas chromatography/mass spectrometer. The surface and structural properties of biochar were detected and analyzed by Fourier transform infrared spectrometer, scanning electron microscope and surface area and porosity analyzer. [ABSTRACT FROM AUTHOR]

Biomass can be converted into more valuable forms of energy by many thermal, biological and physical methods. While energy can be obtained by direct combustion of biomass, solid, liquid and gaseous fuels can be obtained from biomass by various thermochemical conversion methods (Hydrothermal liquefaction, pyrolysis and gasification). Hydrothermal liquefaction is one of the thermochemical processes used to convert biomass into liquid products with high energy content. Various catalysts (homogeneous and heterogeneous) can be used in the hydrothermal liquefaction process. It has been stated in the relevant literature that heterogeneous catalysts have various advantages such as recovery and obtaining liquid products with low oxygen content. In this study, the stem of Glycyrrhiza glabra L. (Liquorice) plant is liquefied for the first time in the presence of Al and Fe metal powders catalyst. In the trials, 300, 325 and 350 °C temperature and 30 minutes waiting time parameters are determined. GC–MS and elemental analysis methods are used for the characterization of the products. For light bio-oil and heavy bio-oil, the optimum temperature was 325°C and the highest energy value was 32.01 Mj/kg in the presence of Fe catalyst. Heterogeneous catalyst is found to be effective in the liquefaction of Glycyrrhiza glabra L. plant. [ABSTRACT FROM AUTHOR]

One of the key pathways that can contribute to net‐zero goals is to enhance the use of renewable and sustainable biofuels. However, uncertainties remain owing to critical challenges to selecting the right sustainable biofuels technology most suitable for the longer term. These uncertainties can be partly addressed using a multidisciplinary perspective for scenarios and multicriteria decision‐making analysis. Multicriteria decision support tools (DSTs) are a powerful means to conduct the comparison of technology pathways at different technology readiness levels (TRLs). For this case study, a multidimensional DST was used to compare two technology pathways: (1) gasification combined with Fischer–Tropsch; and (2) hydrothermal liquefaction (HTL) to produce biofuels. The metrics available in the DST were examined, and five metrics related to evaluating profitability, robustness and capital efficiency as well as socio‐economic performance were selected. HTL was found to have a higher yield for renewable gasoline and diesel, largely due to higher economic performance and reduced environmental footprint as compared with the integrated gasification Fischer–Tropsch process. However, the TRL of 8–9 of biomass gasification was higher than that of HTL, which was still at 5–6, reflecting that the gasification process is essentially proven at a pre‐commercial scale. Based on sensitivity and scenario analyses, the importance of government support for capital cost and of biofuel price production incentives was identified as critical. From this comparison, HTL emerges as an attractive process for the future because of its outperformance from technical and environmental perspectives, but further demonstration efforts are still needed at the commercial scale. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Effective management is necessary due to the substantial environmental challenges arising from the significant annual biosolids production in wastewater treatment plants. Hydrothermal liquefaction (HTL) provides a viable solution for transforming biosolids into renewable crude oil. However, further investigation is required to understand the HTL of biosolids. An examination of HTL in a small-scale batch reactor revealed that both the HTL reaction conditions and biosolids content influence the yield of renewable crude oil, which ranged from 21% to 26%, where the highest yield was achieved at 250 °C, 20 min. However, the highest extractible renewable crude yields were achieved at 350 °C and 40 mins due to the high amount of the low boiling material at a low boiling point. The fractions of renewable crude oil were influenced by both the HTL reaction conditions and the biosolids content. Based on the boiling point, biosolids with a high-lipid content produced the maximum potential gasoline and naphtha-like yield, while high-carbohydrate biosolid content generated the highest potential kerosene-like yield. All biosolid samples demonstrated significant potential for gas oil-like, wax, and lubricating oil-like fractions. Additionally, A developed bulk kinetic model to predict the product fractions showed the trends in product fractions with various reaction times and temperatures. • The products' yields and quality affected by biomass type and HTL conditions. • Boiling point profiles of renewable crude determined by TGA analysis. • Biosolids with high lipid and protein content increase the renewable crude yield. • Desirable crude fractions depend on both biosolids composition and HTL conditions. [ABSTRACT FROM AUTHOR]

A preliminary techno‐economic assessment of a microalgae biorefinery plant is reported, with pulsed electric field treatment (PEF) hydrothermal liquefaction as core technology. The results indicate that standalone production of microalgae biofuel would lead to an annual loss of 2.615 M€. PEF treatment could improve this scenario by bringing the microalgae biofuel to a competitive level (0.78 € kg−1). Assuming that microalgae biofuel would be sold at the price of crude oil (0.44 € kg−1), the minimum price of the amino‐acid based product should be 7.56 € L−1 for positive capital returns. [ABSTRACT FROM AUTHOR]

Global energy demand and environmental concerns about limiting CO2 emissions have been growing recently. This is why fuel production from renewable resources has become a priority. In this context, microalgae represent an attractive alternative carbon source. In this work, different supported catalysts, including metal phosphide, nitride, and sulfide, were tested for the hydroconversion of bio‐oil issued from the hydrothermal liquefaction of microalgae. Supported Ni phosphide catalysts promoted the decarboxylation and decarbonylation route, while NiMo nitride promoted the hydrodeoxygenation pathway. NiW sulfide catalysts were the most performant, producing a hydrotreated oil with the best higher heating value (HHV), lower aromaticity degree, and lower average molar mass. Among sulfide catalysts, NiWS/SiO2−Al2O3 was the least active, probably due to the inhibition of acid sites by the nitrogen compounds. However, NiWS/Al2O3 performed better, showing high hydrogenation performances, which contributed to the conversion of refractory compounds. [ABSTRACT FROM AUTHOR]

In this study, the catalytic hydrothermal liquefaction technology was adopted to convert the Chinese herb residue (CHR) into liquid bio-oil. The effect of the reaction conditions was investigated including temperature, water/biomass mass ratio (W/B) and time. Different combinations of Fe, Ni and ZSM-5 molecular sieve catalyst were evaluated to improve the bio-oil quality. The optimized liquefaction parameters were determined through experiments, which were the reaction temperature of 320 °C, W/B of 15:1, and reaction time of 10 min; the yield and high heat value (HHV) of bio-oil were 24.7 wt% and 29.39 MJ/kg, respectively. There was a synergy between Fe and ZSM-5, and Fe/ZSM-5 can achieve in situ hydrodeoxygenation in the liquefaction process, increasing the HHV of bio-oil to 31.74 M J/kg at 10 wt% loading with the yield of 21.3 wt%. The enhancement of bio-oil quality by Ni/ZSM-5 was weak due to the cleavage of C–C bond by Ni, resulting in the poor HHV and a low yield; the catalytic performance of Fe–Ni/ZSM-5 was between the former two catalysts. Elemental analysis and GC-MS showed that Fe/ZSM-5 increased H/C and decreased O/C in bio-oil, and the content of aliphatic compounds in bio-oil increased to 72.96%. • Chinese herb residue can be efficiently utilized by hydrothermal liquefaction. • Reaction temperature and W/B have a significant effect. • The operating conditions were given for highest yields of bio-oil. • Fe/ZSM-5 exhibits synergistic effect of hydrodeoxygenation. • 10 wt% Fe/ZSM-5 increases the HHV of bio-oil to 31.74 MJ/kg. [ABSTRACT FROM AUTHOR]

The use of biofuels in the transport sector is one of the strategies for its decarbonization. Here, the LCA methodology was used for the first time to assess the environmental impacts of a biorefinery where hydrothermal liquefaction (HTL) and aqueous phase reforming (APR) were integrated. This novel coupling was proposed to valorize the carbon loss in the HTL-derived aqueous phase, while simultaneously reducing the external H 2 demand during biocrude upgrading. Corn stover (residue) and lignin-rich stream (waste) were evaluated as possible lignocellulosic feedstocks. The global warming potential (GWP) was 56.1 and 58.4 g CO 2 eq/MJ biofuel , respectively. Most of the GWP was attributable to the electrolysis step in the lignin-rich stream case and to the thermal duty and platinum use in the corn stover case. Other impact categories were investigated, and an uncertainty analysis was also carried out. A sensitivity analysis on biogenic carbon, electricity/thermal energy source and alternative hydrogen supply was conducted to estimate their influence on the GWP. Finally, the two scenarios were compared with the environmental impact of fossil- and other biomass-derived fuels, also considering fuel utilization. HTL-APR allowed a 37% reduction compared to fossil diesel, further reduced to 80% with the lignin-rich stream when green energy was used. • Environmental evaluation of a biorefinery coupling HTL and APR. • Electrolysis is the most impacting factor when lignin-rich stream is used as feed. • Using decarbonized electricity would result in a 72% GWP reduction. • Thermal power is the key factor when corn stover is used as feed. • The biofuel from HTL-APR plant has 37% lower emission than fossil diesel. [ABSTRACT FROM AUTHOR]

Bio-oil production from wastewater-treated duckweed by hydrothermal liquefaction (HTL) is a sustainable development mode. In this study, the effect of reaction conditions on nitrogen transformation during HTL of wastewater-treated duckweed for bio-oil production was investigated. GC-MS, FT-ICR-MS and XPS were used to characterize the nitrogen speciation in each product. The highest bio-oil yield of 34.7 wt% was obtained at 360 °C, 60 min. The maximum high heating value (HHV) and energy recovery of bio-oil separately reached 36.41 MJ/kg and 86.11%. As the temperature increased (240 °C–360 °C), more nitrogen (21.14%–35.50%) migrated to the bio-oil and mainly existed in the form of nitrogen-containing heterocycles and amides. Higher temperatures favored the acylation reaction to produce more amides, while the Maillard reaction was hindered resulting in a decrease in the relative content of nitrogen-containing heterocycles. N 2 species such as pyrazines, imidazole were the dominant organic nitrogen species. In the aqueous phase, the nitrogen recovery decreased from 44.7% to 39.3%, and pyridine, pyrimidine and pyrrolidine were the most abundant organic nitrogen forms. The nitrogen distributed to the solid residue decreased from 21.1% to 5.1%, with pyridine-N becoming the dominant nitrogen species at temperatures above 320 °C. [Display omitted] [ABSTRACT FROM AUTHOR]

Hydrothermal processing/liquefaction of biomass is the conversion of biomass in the presence of water at elevated temperature (> 200 °C) and autogenous pressure into functional chemicals and biofuels/hydrocarbons. The principal goal of the study is to understand the behavior of alkali-pretreated castor residue on product yield and conversion using hydrothermal liquefaction (HTL). The alkali pretreatment of castor residue was done using sodium hydroxide with variations in the pretreatment time. In this study, the hydrothermal liquefaction reaction was conducted at 260–300 °C for 60 min. The variation in alkali pretreatment time leads to change in the weight percentage of biomass components. The maximum yield of total bio-oil (TBO) observed at a temperature of 280 °C was 12.50 wt.%. The obtained products were analyzed using 1H NMR, FTIR, GC–MS, SEM, XRD, TOC, and elemental analysis. The formation of various chemical compounds was observed such as aldehydes, aromatics, phenolics, acids, and N- containing compounds. Phenolic compounds were found maximum in bio-oil and can be a useful feedstock in the chemical industry. The maximum heating value of bio-oil and biochar was 34.98 and 22.63 MJ/kg, respectively. [ABSTRACT FROM AUTHOR]

Hydrothermal liquefaction (HTL) is an evolving technology that can convert waste with high moisture and low energy content to electricity, heat, hydrogen and other synthetic fuels more efficiently. The lee side is that the HTL process produces enormous amounts of wastewaters (HTWW), having high organic and nutrient load. The discharge of the HTWW would contaminate the environment and result in the loss of valuable bioenergy sources. The valorisation of HTWW has drawn considerable interest. Therefore, this review highlights the valorisation of wastewater during the HTL of biomass. The review paper begins with the discussion of the role of microalgae in valorizing the HTWW. The survey illustrates that the selection of appropriate technology is dependent on biomass characteristics of the microalgae. Finally, potential research opportunities are recommended to improve the viability of the HTL wastewater valorisation for bioenergy production. Overall, this review concludes that combining various processes, such as microalgae-anaerobic digestion, and bio-electrochemical system - microalgae-anaerobic digestion would be beneficial in maximizing HTWW valorisation. [ABSTRACT FROM AUTHOR]

Hydrothermal liquefaction (HTL) is an emerging method for thermochemical conversion of wet organic waste and biomass into renewable biocrude. HTL also produces an aqueous phase (HTL-AP) side stream containing 2–4% light organic compounds that require treatment. Although anaerobic digestion (AD) of HTL-AP has shown promise, lengthy time periods were required for AD microbial communities to adapt to metabolic inhibitors in HTL-AP. An alternative for HTL-AP valorization was recently demonstrated using two engineered strains of Yarrowia lipolytica, E26 and Diploid TAL, for the overproduction of lipids and the polyketide triacetic acid lactone (TAL) respectively. These strains tolerated up to 10% HTL-AP (v/v) in defined media and up to 25% (v/v) HTL-AP in rich media. In this work, adaptive laboratory evolution (ALE) of these strains increased the bulk population tolerance for HTL-AP to up to 30% (v/v) in defined media and up to 35% (v/v) for individual isolates in rich media. The predominate organic acids within HTL-AP (acetic, butyric, and propionic) were rapidly consumed by the evolved Y. lipolytica strains. A TAL-producing isolate (strain 144-3) achieved a nearly 3-fold increase in TAL titer over the parent strain while simultaneously reducing the chemical oxygen demand (COD) of HTL-AP containing media. Fermentation with HTL-AP as the sole nutrient source demonstrated direct conversion of waste into TAL at 10% theoretical yield. Potential genetic mutations of evolved TAL production strains that could be imparting tolerance were explored. This work advances the potential of Y. lipolytica to biologically treat and simultaneously extract value from HTL wastewater. Key points: • Adaptive evolution of two Y. lipolytica strains enhanced their tolerance to waste. • Y. lipolytica reduces chemical oxygen demand in media containing waste. • Y. lipolytica can produce triacetic acid lactone directly from wastewater. [ABSTRACT FROM AUTHOR]

Hydrothermal liquefaction (HTL) can convert wet biomass into biocrude, particularly with a comparable energy content with petroleum. The biocrude can be refined as fuel oils in farming machinery, cars, trains, ships, or planes. However, the biocrude from HTL is a complex mixture of oxygen and nitrogen, including phenols, alcohols, acids, esters, ketones, and amines. The biocrude is too tricky to be used, due to its high viscosity and low stability during storage. The extraction solvent is one of the most influencing factors to affect the biocrude yield and oil properties. Also, solvent extraction can serve as an efficient way to separate the biocrude. In this study, the multistep extraction was proposed to separate the biocrude into some components with different polarities, and then to analyze the effects of different components on the storage stability of biocrude. Spirulina was used as the feedstock for the HTL under the optimal reaction condition (reaction temperature: 260°C, retention time: 60 min, and total solid: 20%) from the previous study. Tetrahydrofuran, ethyl acetate, acetone, and n-hexane were used as the extraction solvents to separate the biocrude. Those solvents were chosen, depending on their polarity and ability to extract the biocrude yield. An accelerated aging test was carried out to investigate the effects of different extraction solvents on the storage stability of biocrude. The results showed that the multistep extraction performed the best to separate the biocrude into heavy, mild, and light oil. The BC12 extracted from ethyl acetate presented the lowest viscosity (316 mPa·s), the best fluidity, the lowest viscosity change rate (78.6%), and the best stability during storage. Once the n-hexane was used to separate the BC12 into M1 and L1, the viscosity of M1 was higher than that of BC12. There was a high viscosity change rate of M1, and then the fluidity was lost after four days of storage, even finally became the biochar was after seven days. The M2 also showed a higher viscosity and lower fluidity than the BC2 extracted by acetone. TG, GC-MS, and FT-IR analysis revealed that the solidification of M1 was closely related to the esterification, polymerization, and physical condensation. The better storage stability of biocrude was achieved in the absence of the high polar and heavy components. The biocrude aging was attributed to the severe polymerization in the components of heavy oil, including many macromolecular compounds, such as phenols and nitrogenous compounds. Element analysis indicated that the heavy oils were likely to contain more N, where the light oils contained more H. The higher heating value (HHV) changing rate of biocrude increased with the increase of N content, where the HHV of biocrude decreased by 0.44-6.62% after storage. The solvent extraction removed the macromolecular compounds, and reduced the heteroatomic content in the biocrude, leading to improve storage stability of the biocrude. The presence of small non-polar compounds significantly reduced the viscosity of biocrude for better fluidity and storage stability. From the perspective of the oil quality, the low polar and light components of biocrude shared better storage stability than the high polar and heavy components, which can be used as transportation fuels. The heavy component can be used as asphalt or boiler fuel. The biocrude can be separated by distillation to produce different products in future industrial production. [ABSTRACT FROM AUTHOR]

Depolymerisation of kraft lignin under hydrothermal conditions was investigated at short residence times (1–12 min) with glycerol being used as a capping agent. The weight average molecular weight (Mw) of the products decreased within the first minute of residence time, with the inter-unit ether linkages breaking accordingly. Furthermore, the Mw of the product fractions decreased at increasing residence times, while the char yield increased. Short residence times thus appear to be beneficial for mitigating the formation of char. Also, addition of NaOH reduced the yield of char. Although the addition of glycerol caused a decrease in the Mw of the products, it seemed to increase the yield of char and therefore might not be a suitable capping agent for kraft lignin depolymerisation. [ABSTRACT FROM AUTHOR]

This study followed a quantitative approach, with the purpose of converting municipal sewage to valuable bio-oils. The sewage sludge was subjected to hydrothermal liquefaction in 60 mL stainless steel batch reactors, where the effects of temperature, solvent composition and solvent content were investigated, and all the other process parameters were maintained at constant values. Temperatures were explored between 220 and 370°C. The two solvents investigated were de-ionized water (H2O) and ethanol (E) which were applied in the following compositions: 1:0, 1:1 and 0:1 (H2O:E). The five solvent contents (moisture contents) investigated were 75, 80, 85, 90 and 95 wt%. The temperature of 310°C emerged categorically as the optimal temperature across the various solvent contents. The best yield was achieved when H2O/E (1:1) performed as a co-solvent at 85% solvent content and 310°C, which amounted to 40.69 wt%. Bio-oils derived by the use of pure H2O solvent were overall the least effective in yielding high bio-oil quantities. The lowest bio-oil yield obtained was 6.42 wt% where pure H2O was the solvent at extreme conditions of 370°C and 95% solvent content. The order of efficiency of solvent content was as follows: 85% > 80% > 75% > 90% > 95%. Among the six temperatures investigated, the intermediate temperature, 310°C, gave the highest conversions. The highest conversion across all of the runs was 85.65% at 310°C with 90% solvent content using the co-solvent H2O/E. The order of superiority of solvent was H2O/E > pure ethanol > pure water. © 2022 The Authors. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

Seaweed can be a desirable source of renewable energy or fuel after it has been processed by combustion, thermochemical conversion by gasification, pyrolysis, or hydrothermal liquefaction (HTL) or biochemical conversion routes like anaerobic digestion (AD). This work explores how well the measured properties of seaweed pellets match the specifications for the various fuel and energy conversion options listed. Blends of hay, wood chips, sawdust, and seaweed were pelletized. Eight pellet blends with dominant seaweed content and minimum acceptable mechanical strength and stability were produced and their physical and chemical properties were reported. The seaweed pellets had an energy content of around 14 MJ/kg, and each pellet could withstand almost 200 N of compression force. Their water content was around 5% or less and their ash content was around 20–34%. According to the results, a higher wood content increased the energy content of the pellets. Among those properties measured in this project, none of them contradicted the typical specifications of combustion, HTL, and AD. However, the low water content and low strength of some pellet types were unable to meet the specifications for certain types of gasification and pyrolysis. [ABSTRACT FROM AUTHOR]

Although the whole microalgal biomass is typically used as a feedstock for hydrothermal liquefaction (HTL), the conversion of a primary metabolite (i.e., carbohydrate) to biocrude is very low. In this study, a self-settling cyanobacterium (i.e., Chroococcidiopsis sp.) was used to understand the effect of carbohydrate removal, as a pretreatment, on the net energy recovery from the residual biomass. The optimum biocrude yields from pretreated and control biomass were 50.2% (350 °C) and 41.3% (300 °C), respectively. For the temperature range studied, the biocrude yield from the pretreated biomass was higher compared to that obtained from the control feedstock. Further, maximum alkane formation of 42.7 and 23.3% occurred for pretreated and control biomass, respectively, at 325 °C. Total organic carbon and total nitrogen values in the aqueous phase liquid obtained from pretreated biomass were at least 1.31 and 1.23 times lower when compared to the corresponding values obtained from control biomass. When APL was recycled as a source of nutrients, it reduced the biomass yield (24.1%) and pigment content (68.4%) in Chroococcidiopsis sp. Further, a model was developed to understand how the cellular carbohydrate content would affect the net energy recovery for the proposed biorefinery route. A schematic of microalgal bio-oil production from Chroococcidiopsis sp. using a biorefinery-approach. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, the Ammi visnaga plant was liquefied in the presence of Mo, Al and Co metal powder catalysts and without catalyst. Liquefaction trials were carried out at 225, 250, 275 and 300 °C reaction temperatures and reaction times of 0, 15, 30 and 45 min. The highest liquid product yield was determined as 42.31% in the experiment without catalyst and 39.42% with Mo catalyst at 300 °C. GC-MS, XRD, TOC, SEM-EDX and Elemental analysis methods were used to characterization of solid and liquid product. The highest energy values were determined as 25.34 MJ/kg for light oil and 29.69 MJ/kg for heavy oil with Co catalyst. In order to investigate the agricultural application potential, the effects of the wastewater obtained at the end of the trials on Trichoderma harzianum , Clonostachys rose and Rhizoctonia solani fungi were investigated. It was determined the bioagent fungi developed and pathogen growth was inhibited. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, black cumin seed cake was converted to liquid and solid products with catalyst (Al2O3, Ca(OH)2, SnCl4.5H2O) and without catalyst at 300°C, 325°C, and 350°C by using the hydrothermal liquefaction method. The obtained products were analyzed by GC-MS, FT-IR, SEM, elemental analysis, and the 1H NMR method. The highest light bio-oil yield was determined as 3.18% at 350°C with the catalyst SnCl4.5H2O and the highest heavy bio-oil yield was found to be 37.37% at 300°C with the catalyst Al2O3. According to the results of the elemental analysis, the energy values of the liquid products (Light, Heavy bio-oil) varied between 21.87 and 31.78 Mjkg−1 and the energy values of the solid products ranged between 16.22 and 18.28 Mjkg−1. In the GC-MS analysis of the liquid products gained at 300°C and 350°C, a large number of different compounds, generally composed of monoaromatic, aliphatic, polyaromatic, and oxygenated compounds, were obtained. [ABSTRACT FROM AUTHOR]

Algae are a diverse group of aquatic organisms and have a potential to produce renewable biofuel via hydrothermal liquefaction (HTL). This study investigated the effects of reaction environments on biocrude production from "Tetraselmis sp." algae strain by HTL process using red mud (RM) based catalyst. The inert (N2), ethylene (C2H4), reducing (10% H2/90% N2), and oxidizing (10% O2/90% N2) environments were applied to the non-catalytic as well as catalytic HTL treatments with two forms of RM catalysts: RM reduced at 500 °C (RRM) and nickel-supported RM (Ni/RM). Under nitrogen, ethylene and reducing environments, the biocrude yield increased by the following trend: No Catalyst < RRM < Ni/RM. The Ni/RM catalyst produced the highest biocrude yield (37 wt.%) in an ethylene environment, generated the lowest total acid number (14 mg KOH/g) under inert atmosphere, and lowered sulfur (33–66%) and oxygen (18–30%) from biocrude products irrespective of environments. The RRM catalyst maximized the biocrude carbon content (61 wt.%) under a reducing environment and minimized the heavy metal and phosphorus transfer from the feedstock to biocrude in studied ambiences. The reducing environment facilitated mild hydrotreatment during HTL reaction in the presence of RRM catalyst. Among the non-catalytic experiments, the reducing atmosphere optimized carbon content (54.3 wt.%) and calorific value (28 MJ/kg) with minimum oxygen amount (27.2 wt.%) in biocrudes. [ABSTRACT FROM AUTHOR]

The use of algal biomass as a renewable source of energy is potentially promising. The literature on biofuels derived from Sargassum is limited compared to other macroalgae. The unusual seaweed bloom of Sargassum from 2011 to date can be caused by the following factors: eutrophication of the sea, climate change, and other oceanographic patterns. The atypical invasion has had great ecological and economic effects in the affected regions. Traditionally, Sargassum has been recovered from coasts and beaches for use as fertilizer, but new markets need to be found to exploit the large volumes produced by the seaweed influx and mitigate its impact. The biochemical composition of Sargassum biomass defines it as a potential feedstock for biofuel production. However, the high moisture and ash content constitute the limitations for the development of some energy extraction methods. On the other hand, the costs associated with the removal of high volumes of accumulated Sargassum from coasts and beaches, transportation, cleaning, and storage are relatively high. Therefore, the production of biofuels from Sargassum seaweed is still a technical, economic, and energy challenge. This review proposes a multifactorial approach to the potential use of Sargassum biomass as feedstock for energy production, especially by thermochemical conversion (combustion, gasification, pyrolysis, and hydrothermal liquefaction). The survey analyses the chemical composition, biomass productivity and coastal impact, energy output, thermochemical conversion processes, techno-economic challenges, and future perspectives. In addition, a Sargassum biomass biorefinery approach with a circular bioeconomy approach is proposed. [ABSTRACT FROM AUTHOR]

This study shows the effect of reintegrating the aqueous phase to the hydrothermal liquefaction process of microalgae to obtain biocrude. The company Cementos Argos has developed CO2 capture processes through microalgae farming to mitigate the environmental impact of the cement industry. Microalgae are transformed into biocrude through hydrothermal liquefaction processes that use a large amount of water, generating liquid discharges. The results show that it is possible to recirculate these residues into the process and increase biocrude yield. It is shown that when the aqueous phase reaches a high content of dissolved organic material (COD > 1,200,000 mg O2/l), part of this material is transformed into biocrude, increasing its yield to about 10-15%. It is concluded that there are no liquid discharges in this process, favoring its viability and its potential for producing higher value-added fuels such as diesel and gasoline. [ABSTRACT FROM AUTHOR]

Sugarcane is both food and energy crop providing sugar and energy products. Hydrothermal liquefaction (HTL) is gaining importance for the conversion of sugarcane bagasse to bio-oil, whose yield depends on the deoxygenation activity of the catalyst employed and process parameters. In this study, mesoporous Fe-MCM-41 catalysts were synthesized with crystallization time varied from 12 to 72 h, characterized by X-ray Diffraction (XRD), textural analysis, Scanning Electron Microscope (SEM), Energy Dispersive X-ray (EDX), and evaluated for the HTL of sugarcane bagasse. All the Fe-MCM-41 catalysts gave higher bio-oil yield with lower oxygen content compared to noncatalytic HTL, confirmed their deoxygenation activity. Among them, Fe-MCM-41 synthesized after 24 h of crystallization was found to have the highest crystallinity, and surface area thus gave the highest bio-oil yield of 56.2% containing the least amount of oxygen of 15.3 wt% at 250 °C, initial CO pressure of 45 bar, reaction time of 120 min, Water/Biomass weight ratio of 28, Catalyst/Biomass weight ratio of 0.4 and 0.2, respectively. Overall process of HTL of sugarcane bagasse was found to involve two consecutive equilibria, first conversion of lignocellulose of sugarcane bagasse by hydrolysis to water soluble organics (WSO) followed by its deoxygenation to bio-oil. [ABSTRACT FROM AUTHOR]

Due to the overuse of fossil energy, fossil energy is facing exhaustion. Agricultural biomass such as wheat straw waste is a kind of clean energy which can replace fossil energy and has important scientific research value and broad application prospect. In this paper, wheat straw was used as raw materials, and the straw was converted into lactic acid, oxalic acid and fumaric acid under alkaline hydrothermal conditions. Improve the yield of organic acid by optimizing the reaction conditions such as NaOH concentration, reaction time and reaction temperature. The optimum reaction conditions were as follows: NaOH concentration 1.5 mol/L, reaction temperature 250ºC, reaction time 3 hours, total organic acid yield 13.5%, lactic acid yield 12.1%. The results can provide a new way for the green production of organic acids, and realize the efficient utilization of agricultural waste, reduce environmental pollution. At the same time, can produce good economic benefits, ecological benefits and social benefits. [ABSTRACT FROM AUTHOR]

In this study, we investigate the hydrothermal liquefaction (HTL) of PET separated from a densified postconsumer plastic mix, with the aim of recovering its monomer. This second raw material is made up of 90% polyolefin, while the remaining 10% is made up of PET, traces of metals, paper, and glass. After preliminary separation by density in water, two batch experiments were performed on the sunken fraction (composed mainly of PET) in a stainless steel autoclave at 345 °C for 30 and 20 min. Both trials resulted in similar yields of the three phases. In particular, the solid yield is around 76% by weight. After a purification step, this phase was analyzed by UV–Vis, 1H-NMR, and FTIR spectroscopy and resulted to be constituted by terephthalic acid (TPA), a product of considerable industrial interest. The study proved that the hydrothermal liquefaction process coupled with density separation in water is effective for obtaining TPA from a densified postconsumer plastic mix, which can be used for new PET synthesis. [ABSTRACT FROM AUTHOR]

In this work, hydrothermal liquefaction of wood chips was studied for biocrude production using a mix of Ni–Mo nitrides and carbides. The catalytic materials were synthesized by a temperature-programmed reaction method at 800 °C under a hydrogen atmosphere with nickel loads from 0 to 20 wt%. Lignin contained in the lignocellulosic biomass was successfully release via Kraft process. Hydrothermal liquefaction was carried out in a batch reactor at 320 °C with an initial pressure of 1000 psi of H 2. According to characterization results, nanostructured catalysts with a mix of Ni 2 Mo 3 N/Mo 2 C compo4unds were obtained. NiMo series catalysts composition varies with nickel loads. The catalytic activity shows a reduction in the amount of solid products and an increase in the production of gaseous products as a function of the increase Ni loadings on the catalyst. The most optimal production of biocrude was obtained with the NiMo-10 catalyst, since 81.43% of the total product corresponded to water soluble products (WPS) fraction and the oil fraction, while the solids fraction represented the 6.43% of the total product. Hydrothermal liquefaction catalytic processes were selective towards WSP fraction, improving biocrude quality and favoring biocrude conversion into advanced biofuels. • Nanostructured catalysts with mixtures of Mo 2 C and Ni 2 Mo 3 N were obtained. • Ni 2 Mo 3 N composition in NiMo series increase with the increment of nickel load. • Lignin contained in the biomass was successfully release via Kraft process. • NiMo series catalysts exhibited high selectivity towards WSP fraction. [ABSTRACT FROM AUTHOR]

Biomass is one of the most promising renewable resources, and biomass energy is also recognized as the zero-carbon emission energy. Over the past decade, thermochemical conversion technologies have been well developed to convert different types of biomass feedstocks into solid biochar, liquid fuels, and gas, in which catalysts are commonly applied. This review summarizes the types of catalysts used in three common thermochemical conversion pathways (pyrolysis, hydrothermal liquefaction and gasification), while focusing on the most recent progress in the applications of catalysts in these processes. The catalytic reaction mechanisms, catalysts deactivation and regeneration, industrial utilization, as well as the challenges and knowledge gaps for applications of catalyst in these processes are analyzed and discussed. [Display omitted] • Recent applications of catalysts in pyrolysis, HTL and gasification are summarized. • Pyrolysis, HTL and gasification conversion technologies of biomass are introduced. • Catalytic mechanisms and catalysts deactivation and regeneration are discussed. • Challenges and knowledge gaps for the applications of catalysts are identified. [ABSTRACT FROM AUTHOR]

Slow pyrolysis and gasification reactivities of waste biochar samples, produced after hydrothermal treatment of spent coffee grounds, were determined using a thermogravimetric analyser (TGA) at 900 °C under CO2. Biochar samples were prepared by wet oxidation treatment in 30 vol.% hydrogen peroxide at room temperature for 2, 6, and 24 h and at 80 °C for 0.5, 1, and 2 h. NMR results showed that the samples treated at 80 °C showed a slight decrease in the amount of aromatic carbons and a significant reduction in the number of aliphatic carbons. The wet oxidation-treated biochar was thermally treated at 900 °C (10 °C min−1) under N2 for 2 h to produce a coke substitute. Results showed that the wet oxidation treatment of the samples at room temperature did not show much degradation, but samples treated at 80 °C showed higher mass losses. The temperature at which wet oxidation is performed has a significant effect during the process. The pyrolysis chars were investigated for their CO2 or gasification reactivities. CO2 isothermal gasification was used to determine the reactivities of the produced substitute coke char samples and industrial coke sample. The prepared substitute coke chars and the industrial coke samples were subjected to thermogravimetric analyses at an isothermal temperature of 900 °C in a CO2 atmosphere. Characterization of the prepared substituted coke samples was carried out using nuclear magnetic resonance (NMR). The CO2 gasification results showed that the average initial reactivities, the reactivities at 50% conversion, and the average final reactivities of the prepared samples were up to three times that of the industrial coke sample. The pyrolysis char of the coke substitute sample prepared for 2 h at 80 °C with a wet oxidation method has an average initial reactivity of 6.59 × 10–3 min−1, reactivity at 50% conversion of 15.73 × 10–3 min−1, and 9.6 × 10–3 min−1 for average final reactivity. The coke substitute samples produced from the waste coffee ground biochar subjected to a wet oxidation treatment method may be utilized as a coke substitute, with similar or higher gasification reactivity than industrial coke. [ABSTRACT FROM AUTHOR]

Water pollution is one of the major environmental challenges in contemporary times. Biochar from hydrothermal processes (known as hydrochars) has been explored as adsorbents for the removal of pollutants from wastewater. Hydrochars are a special class of biochar that is obtained from hydrothermal processes such as hydrothermal carbonisation (HTC) and hydrothermal liquefaction (HTL). Because of its good pore volume, surface area, high efficiency, and regeneration ability, hydrochar is an appealing choice for the remediation of a wide range of contaminants. This review aimed to focus the uniqueness of hydrochar properties and evaluate their performance on the adsorption of different pollutants from wastewater. It was observed that hydrochars can be effectively applied to a wide variety of pollutants including heavy metals, dyes, Pharmaceutically Active Compounds (PhACs), Endocrine Disruption Chemicals (EDCs), nitrates, phosphates and sulphate. The utilisation of hydrochar in water treatment solves constraints such as lack of regeneration, environmental friendliness, commercial feasibility, and disposal, handling or management concerns. [Display omitted] • Hydrochars are a special class of biochar obtained from hydrothermal processes. • The adsorption of various pollutants from wastewater by hydrochar is reviewed. • The use of hydrochar will contribute to the reduction of solid wastes and promote the circular economy. [ABSTRACT FROM AUTHOR]

This work evaluates the effect of feedstock type and composition on the conversion of lignin to liquid by solvolysis with formic acid as hydrogen donor (LtL), by analyzing the yields and molecular composition of the liquid products and interpreting them in terms of both the type and the preprocessing of the lignocellulosic biomass using chemometric data analysis. Lignin samples of different types and purities from softwood, hardwood, and grasses (rice straw and corn stover) have been converted to bio-oil, and the molecular composition analyzed and quantified using GC-MS. LtL solvolysis was found to be a robust method for lignin conversion in terms of converting all samples into bio-oils rich in phenolic compounds regardless of the purity of the lignin sample. The bio-oil yields ranged from 24–94 wt.% relative to lignin input and could be modelled well as a function of the elemental composition of the feedstock. On a molecular basis, the softwood-derived bio-oil contained the most guaiacol-derivatives, and syringol was correlated to hardwood. However, the connection between compounds in the bio-oil and lignin origin was less pronounced than the effects of the methods for biomass fractionation, showing that the pretreatment of the biomass dominates both the yield and molecular composition of the bio-oil and must be addressed as a primary concern when utilization of lignin in a biorefinery is planned. [ABSTRACT FROM AUTHOR]

[Display omitted] • EFB was subjected into hydrothermal liquefaction in the presence of bimetallic modified HZSM-5. • Bimetallic modified zeolite affected the degradation of EFB and yield of bio-oil. • HTL of EFB using Ba1La2/CHZSM5 exhibited the highest EFB conversion and bio-oil yield. • Chemical composition of bio-oil was influenced by bimetallic modified HZSM-5. • Bimetallic modified HZSM-5 catalysts promotes the generation of bio-oil with less oxygenated compounds. Catalytic hydrothermal liquefaction of empty fruit bunch (EFB) with no added H 2 effectively produces biomass derived fuel or known as bio-oil. In this study, a bimetallic modified zeolite (BaNi, BaLa and BaCe/CHZSM5) catalyst with a series of dosage ratio (1:1, 1:2 and 2:1) was used for the EFB conversion to bio-oil. Ni, La and Ce addition to the Ba/CHZSM5 showed significant changes on the physicochemical properties of catalysts and exhibited enhanced catalytic performance. The activity-structure correlation revealed that EFB conversion and bio-oil yield were favoured on bimetallic modified CHZSM5 and the most effective catalyst was Ba1La2/CHZSM5. Brunauer–Emmett–Teller (BET) surface area measurement and temperature programmed desorption of ammonia (TPD-NH 3) results confirmed that high surface area and rich acidic sites of Ba1La2/CHZSM5 catalyst eventually enhanced the catalytic activity in HTL of EFB. Comparing to other bimetallic modified catalyst, the desirable aromatic and aliphatic hydrocarbon also predominated over Ba1La2/CHZSM5 catalysed reaction which demonstrated that this catalyst have a good ability in produce high quality of bio-oil with less oxygenated compounds. [ABSTRACT FROM AUTHOR]

Biofuel and bioenergy production from diverse biomass sources using thermochemical technologies over the last decades has been investigated. The thermochemical conversion pathways comprise dry processes (i.e., torrefaction, combustion, gasification, and pyrolysis), and wet processes (i.e., liquefaction, supercritical water gasification, and hydrothermal carbonisation). It has been found that the thermochemical processes can convert diverse biomass feedstocks to produce bioenergy sources such as direct heat energy, as well as solid, liquid and gaseous biofuels for instance biochar, bio-oil and syngas. However, some of these processes have limitations that impede their largescale utilisation such low energy efficiency, high costs, and generation of harmful chemicals that cause environmental concerns. Efforts are being made extensively to improve the conversion technologies in order to reduce or solve these problems for energy efficiency improvement. In this review, the emerging developments in the thermochemical techniques for producing biofuel and bioenergy from biomass are presented and evaluated in terms of their technological concepts and projections for implementation. It is suggested that an integration of torrefaction or hydrothermal carbonisation with combustion and/or gasification may optimise biomass energy use efficiency, enhance product quality, and minimise the formation of noxious compounds. [ABSTRACT FROM AUTHOR]

• UF fractionation of hydrothermal liquefaction aqueous product from sludge applied. • In molecular weight range of 1-300 kDa, most organics are fractionated into <1 kDa. • Cumulative specific methane yield is not affected by molecular weight distribution. • Methane production rate is the highest for less than 1 kDa molecular weight range. • Compared to theoretical yield, all fractions yielded 45 % lower specific methane. Hydrothermal liquefaction (HTL) is a promising thermo-chemical technology for municipal sludge treatment due to its potential for biocrude oil recovery and minimizing biosolids management costs. However, the process generates a high volume of an aqueous byproduct that needs to be treated due to its high chemical oxygen demand (COD) and various organic and inorganic compounds. Although the aqueous phase is known to contain recalcitrant and potentially inhibitory substances that may affect its biological treatment, their molecular weight distribution (MwD) and its impact on anaerobic biodegradability are poorly understood. Ultrafiltration (UF) was conducted to fractionate HTL aqueous into different molecular weight (Mw) fractions using 300, 100, 10, and 1 kDa membranes. Mesophilic biochemical methane potential (BMP) assays were conducted to assess the anaerobic biodegradability of each fraction, and the first-order model was used to calculate the degradation kinetics of potential inhibitory compounds. The highest percentage of organics (65 %) was found in the Mw<1 kDa range, whereas the 10>Mw>1 kDa had the lowest percentage (8 %). There was no significant difference in the cumulative specific methane produced from various Mw fractions (p>0.05). The Mw<1 kDa fraction had the highest first-order specific methane production rate (0.53 day−1), whereas the unfiltered HTL had the lowest (0.38 day−1). Although UF fractionation increased the rate of anaerobic degradation of HTL aqueous for the Mw<1 kDa fraction, the observed methane potential was only 55 % of the theoretical value. This implies that 45 % of COD remains undegraded even after permeation through the lowest Mw cut-off membrane. Therefore, further characterization of HTL aqueous is needed for compounds with molecular weights below 1 kDa to fully understand the nature of inhibitory organics and their impact on anaerobic digestion. Furthermore, pretreatments utilizing techniques such as adsorption and advanced oxidation may be necessary to enhance the specific methane yields from various HTL aqueous fractions, thereby bringing them closer to the theoretical yield. [Display omitted] [ABSTRACT FROM AUTHOR]

Wastewater resulting from hydrothermal liquefaction (HTL-AP) of biowaste is gaining attention as an emerging hazardous material. However, there is a lack of specific and systematic ecotoxicity studies on HTL-AP. This study addresses this gap by conducting acute toxicity tests on HTL-AP using typical aquatic species and integrating these results with predicted toxicity values from interspecies correlation estimation models to establish aquatic life criteria. HTL-AP exhibited significant toxicity with LC 50 of 956.12–3645.4 mg/L, but demonstrated moderate toxicity compared to common freshwater pollutants like commercial microbicides, personal care products, and insect repellents. The resulting hazardous concentration for 5 % of species (HC 5), the criterion maximum concentration, and the short-term water quality criteria for aquatic were 506.0, 253.0, and 168.7 mg/L, respectively. Notably, certain organisms like Misgurnus anguillicaudatus and Cipangopaludina chinensis showed high tolerance to HTL-AP, likely due to their metabolic capabilities on HTL-AP components. The significant decrease in HC 5 values for some HTL-AP substances compared to pure compounds could indicate the synergistic inhibition effects among HTL-AP compositions. Furthermore, according to the established criteria, HTL-AP required significantly less diluted water (13 t) than carbendazim (1009 t) to achieve biosafety, indicating a safer release. This research establishes a preliminary water quality criterion for HTL-AP, offering a valuable reference for risk assessment and prediction in the utilization of HTL-AP within environmental contexts. [Display omitted] • The ecotoxicity of HTL-AP was first systematically evaluated. • Water life criterion for HTL-AP was first derived based on testing and model. • A synergistic toxicity of compounds in HTL-AP was confirmed. • The metabolic effects of organisms contributed to the varied tolerances. • The biosafety of HTL-AP was estimated in different application scenarios. [ABSTRACT FROM AUTHOR]