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The exploration of effective utilization of greenhouse wastes is challenging. This paper demonstrates a hydrothermal treatment approach involving the co‐liquefaction of greenhouse wastes with agricultural residue in a mixed solvent of water and ethanol in the presence of a base catalyst, to convert greenhouse wastes and corn stalk into bio‐oil/bio‐polyol at a very high yield of 57.2%, accompanied by a very low yield of solid residue. This bio‐oil (hydroxyl number: 305 mg KOH/g) was successfully used as bio‐polyol to substitute up to 50% petroleum‐based polyol for the preparation of bio‐polyurethane (BPU) foams. The biodegradability of the BPU foams was also studied by incubation with Dyella sp. for a period of 8 weeks. The weight loss, Fourier‐transform infrared (FTIR) spectra, thermogravimetric analysis (TGA) results, and scanning electron microscopy (SEM) images of foam samples were collected and analyzed. The BPU foams exhibited much better biodegradability than the petroleum‐based polyurethane (PU) foam. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

Depleting petroleum reserves together with the associated environmental concerns have intensified the exploration of alternatives to petroleum. Wet food processing wastes present promising bioresources for liquid fuel production via hydrothermal liquefaction (HTL) followed by additional upgrading. In this study, tomato plant waste (TPW) was utilized as a feedstock for the production of bio-crude oils via HTL at medium-temperature (220–280 °C) in water or a water–ethanol (17/3, v/v) medium in a 600 mL autoclave reactor. Effects of various operating parameters, such as catalysts (H2SO4 or KOH), reaction time (15–60 min) and reaction temperature (220–280 °C) on product yields were investigated. This study showed that a high yield (45.1 wt%) of bio-crude oil was achieved from HTL of TPW in water–ethanol medium at 250 °C in the presence of acid catalyst H2SO4. The oil, gas and solid residue (SR) products were analyzed for their chemical and structural properties. [ABSTRACT FROM AUTHOR]

In this study, a novel two-stage hydrothermal liquefaction (HTL) process was employed to produce low-nitrogen bio-crude oils from microalgae, involving pre-treatment of the microalgae with a pre-cooled NaOH/urea solution or a dilute acid and HTL of the pre-treated algal feedstock at 250°C for 10–50 min. The results indicated that the pre-treatment with a pre-cooled NaOH/urea solution effectively removed carbohydrates and protein from the raw microalgae, leading to a decrease in carbohydrates and protein content by 12 wt% and 10 wt% (both absolute values), respectively, while retaining 70 wt% of the solid mass, corresponding to as high as 82% carbohydrates removal efficiency and 40% protein removal efficiency. The two-stage HTL process slightly increased the overall bio-crude oil yields relative to the conventional single-stage HTL process, and the bio-crude oils obtained from the two–stage HTL process have a better quality than those obtained from the single-stage HTL, in terms of lower nitrogen and oxygen levels and higher energy content. [ABSTRACT FROM AUTHOR]

High-energy and cost-intensive cell disruption processes represent one of the major techno-economic bottlenecks in the microalgae-based bio-refineries. Therefore, a feasible disruption method is required to ensure low energy input and operating cost, as well as high target-product (e.g., lipid) recovery. In this study, several different pre-treatment strategies for the disruption of Chlorella vulgaris were investigated, including NaOH/urea, sulfuric acid and ultra-sonication. Experimental results showed that the pre-treatment by NaOH/urea solution resulted in an average mass loss of 33.7 wt.%, and resulted in the removal of 77.2% of carbohydrates and 46.3% of protein (as N) from the original biomass. While these results were comparable to those obtained from the other cell disruption methods, the NaOH/urea method is believed to be more advantageous in terms of energy-efficiency and cost. Afterwards, all pre-treated microalgae samples were subjected to the liquefaction process towards bio-crude oil production. The bio-crude oils obtained from NaOH/urea solvent pre-treated microalgae resulted in higher yields and demonstrated better flow properties. [ABSTRACT FROM AUTHOR]

In this article, we performed catalytic supercritical water gasification (SCWG) of biomass to enhance hydrogen production. First we used glucose as a model compound to screen the best catalyst and then we used this catalyst to gasify biocrude from hydrothermal liquefaction of cattle manure. We introduced a novel dual metal (Ni, Ru)—dual support (Al 2 O 3 , ZrO 2 ) catalyst for the first time in SCWG in order to improve the H 2 yield. A continuous flow tubular reactor was employed to perform the experiments. Novel 10%Ni-0.08%Ru/Al 2 O 3 -ZrO 2 catalyst showed the highest H 2 yield (1.34 mol/mol of C for glucose and 1.01 mol/mol of C for biocrude) and highest carbon gasiifcation efficiency (88% for glucose and 92% for biocrude). It was found that Ru promoted Ni and ZrO 2 showed some catalytic activities towards hydrogen production. The pressure was 25 MPa for all experiments. Stability test showed that 10%Ni-0.08%Ru/Al 2 O 3 -ZrO 2 was highly stable for a 20 h run. Among the parameters studied, higher temperature favored H 2 yield, whereas higher concentration led to lower H 2 yield. We found that carbon gasification efficiency of cattle manure biocrude was independent of variation in temperature and concentration. Also the equilibrium condition was attained at lower temperature and concentration in terms of carbon conversion of the feed. An Eley–Rideal (ER) based mechanistic model was devised and tested against the obtained data. It was found the dissociation of adsorbed oxygenated hydrocarbon is the rate determining step with an average absolute deviation 6.65%. [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]

In order to determine the synergistic effects of the mixed additives of Fe and other catalysts on the yields and characteristics of bio-oil products, hydrothermal liquefaction (HTL) of pinewood sawdust (PW) was performed at 300 °C for 30 min (biomass/water mass ratio = 1:10) in the presence of metallic iron (Fe), other homogeneous/heterogeneous catalysts (Na 2 CO 3 , NaOH, FeSO 4 , MgO, Ru/C, FeS), as well as mixed additives. The results indicated that the metallic Fe could increase the yield and promote the degree of hydrodeoxygenation of bio-oil products. Noticeable synergistic effects on improving the bio-oil yields were found in the presence of mixed additives of Fe and an alkali catalyst (Na 2 CO 3 /NaOH) or FeS. The maximum bio-oil yield and the most energy recovery from bio-oil (81%) were obtained with Fe + Na 2 CO 3. In addition, the combination of Fe + Ru/C produced bio-oil with the highest carbon and hydrogen contents, the highest HHV (30.93 MJ/kg), as well as the lowest contents of oxygenated compounds and the largest amount of hydrocarbons. In summary, this work demonstrates the synergistic effects of the mixed additives of Fe and several catalysts (Na 2 CO 3 , FeS and Ru/C) in HTL of woody biomass, promoting both yields and quality of bio-oil products. • Mixed additives of Fe and other catalysts were applied during HTL of woody biomass. • Synergistic effects between Fe and catalysts on bio-oil yields/properties were found. • Maximum bio-oil yield and energy recovery was obtained with Fe + Na2CO3. • Hydrodeoxygenation of bio-oil was promoted by Fe + Ru/C or Fe + FeS. • Both yields and quality of bio-oil could be improved with Fe and suitable catalysts. [ABSTRACT FROM AUTHOR]

Abstract Microalgae have been widely considered as the potential sources for bio-fuel production without affecting the environment. Hydrothermal liquefaction (HTL) is a suitable technology for converting high water-containing feedstocks (e.g., microalgae) to liquid fuel. However, the structural diversity and rigidity of the microalgal cell wall remains as the major techno-economic bottlenecks for the recovery of intramolecular compounds (e.g., lipid) from microalgae. In this paper, the recent developments in cell disruption technologies and HTL for various microalgae strains are reviewed. The available literature investigating the effect of microalgal pre-treatment on the production of microalgae-derived bio-crude oil are presented. Furthermore, this article provides an extensive review of the recent studies on the HTL of microalgae, including the influences of feedstock characteristics and various operating conditions, underlying reaction mechanism, and physicochemical properties of liquefaction products. Highlights • Recent developments in cell disruption for microalgae are reviewed. • Effect of pre-treatment on oil formation are presented. • HTL operating conditions and reaction pathways for microalgae are discussed. • Physical and chemical properties of HTL products from microalgae are covered. • Challenges and future directions are outlined. [ABSTRACT FROM AUTHOR]

This study aimed to develop a global kinetic model to predict product yields from hydrothermal liquefaction (HTL) of lignocellulosic biomass based on its chemical compositions (contents of cellulose, hemicellulose, and lignin). HTL experiments were carried out with biomass model compounds (cellulose, xylan, and lignin) and lignocellulosic biomass (bamboo, cornstalk, and pinewood) at various temperatures (225–300 °C) and reaction times (10–60 min) with K 2 CO 3 catalyst. Out of the three major components of lignocellulosic biomass, lignin was found to be the main contributor to bio-oil formation. A universal reaction network was proposed, and a kinetic model was developed based on the experimental results obtained from HTL of biomass model compounds. The kinetic parameters were determined by the lease-squares method using a MATLAB optimization function. Assuming no interactions among the components (cellulose, hemicellulose, and lignin) of lignocellulosic biomass during HTL, a global kinetic model was developed based on the chemical compositions of lignocellulosic biomass and the kinetic parameters obtained from the model compound. The developed model was validated with our experimental results from HTL of bamboo, cornstalk, and pinewood and the publicly available HTL data in literature obtained with lignocellulosic biomass feedstocks. [Display omitted] [ABSTRACT FROM AUTHOR]

Laboratory- and pilot-scale hydrothermal liquefaction (HTL) of biomass has predominantly been carried out in batch reactor systems. However, the development of continuous-flow reactor systems is critical for industrial deployment of HTL technology in a cost-competitive manner. In this study, a continuous-flow HTL system (with a feed capacity up to 6 kg/h) was developed and employed to convert various types of bio-feedstocks (wood sawdust, cornstalk, and black liquor) into biocrudes in the presence of K 2 CO 3 catalyst at 300 °C for 12 min. The produced biocrude oils were characterized in detail by using GC-MS, FT-IR, GPC, and elemental analysis. This work compared the performance of the continuous-flow HTL process with that of a batch HTL process under the same conditions in terms of the yields and chemistry of the biocrude products as well as the energy recovery potential. The results indicated that HTL of different bio-feedstocks, particularly cornstalk and pinewood, in the continuous-flow reactor led to a higher yield of biocrude (32.4 and 34.5 wt %, respectively) with lower molecular weights and less solid residue (2.9 and 4.6 wt%, respectively) as well as a higher energy recovery rate (53.3 and 52.0%, respectively) compared with those in the batch reactor (Cornstalk: 23.8 wt%, 6.2 wt% and 46.5%; Pinewood: 28.5 wt%, 10.3 wt% and 50.8%, respectively). These promising results shall advance the future development and deployment of the HTL technology in Canadian and global bioenergy sectors. [Display omitted] • A continuous-flow reactor was developed & tested for HTL of various bio-feedstocks. • Performance of the continuous-flow reactor was compared with that of batch reactor. • Continuous-flow reactor with lignocellulosic biomass produced higher oil. • Continuous-flow reactor with lignocellulosic biomass led to better energy recovery. • Biocrude oils from the continuous-flow reactor have lower Mw but higher O content. [ABSTRACT FROM AUTHOR]

The present paper examines the co-conversion of waste activated sludge and birchwood sawdust to bio-oil via hydrothermal liquefaction. The purpose of using the sawdust with sludge was to increase the solids concentration using another waste material for possible resource recovery. The operating conditions including reaction temperature, reaction time and solids concentration were optimized based on the response surface methodology for the maximum bio-oil production. A maximum of 33.7 wt% bio-oil yield was obtained at optimum operating conditions of 310 °C, 10 min, and 10 wt% concentration. Comparison of this oil with the oil produced from only sawdust showed a significant improvement in the molecular weight of the bio-oil by having lower molecular weight (hence less viscosity), indicating the presence of lighter components, with a slight decrease in bio-oil yield. The optimized operating condition could be used to effectively co-liquefy waste activated sludge and sawdust with the advantage of producing higher quality bio-oil with respect to molecular weight. The water-soluble product which is the largest fraction of by-products from the co-conversion was tested as a feedstock for biogas production through anaerobic digestion and resulted in 800 ml bio-methane production per 0.816 g of TOC or 2.09 g of COD of this waste stream. [ABSTRACT FROM AUTHOR]

In this study, the aqueous phase obtained from catalytic/non-catalytic hydrothermal liquefaction (HTL) of Chlorella vulgaris was recycled as the reaction medium with an aim to reduce water consumption and increase bio-crude oil yield. Although both Na 2 CO 3 and HCOOH catalysts have been proven to be effective for promoting biomass conversion, the bio-crude oil yield obtained from HTL with Na 2 CO 3 (11.5 wt%) was lower than that obtained from the non-catalytic HTL in pure water at 275 °C for 50 min. While, the HCOOH led to almost the same bio-crude yield from HTL (29.4 wt%). Interestingly, bio-crude oil yield obtained from non-catalytic or catalytic HTL in recycled aqueous phase was much higher than that obtained from HTL in pure water. Recycling aqueous phase obtained from catalytic HTL experiments resulted in a sharp increase in the bio-crude oil yield by 32.6 wt% (Na 2 CO 3 -HTL) and 16.1 wt% (HCOOH-HTL), respectively. [ABSTRACT FROM AUTHOR]

Liquid product from white birch bark liquefaction in water/ethanol (50:50, v/v) mixture was successfully applied in substituting 50 wt% of phenol in the synthesis of bark based phenol formaldehyde (BPF) resole (i.e., 50% HTL-oil BPF resole). Besides, eHTL-oil from liquefaction of the bark extracted in 70 vol% aqueous acetone, and fHTL-oil obtained after HTL-oil fractionation in water, were also used to substitute 50% of phenol for BPF resoles synthesis. The results showed that all the three BPF resoles contained more free formaldehyde than the neat PF resole, and bark extraction before liquefaction and HTL-oil fractionation after liquefaction led to higher free formaldehyde contents in the resulted 50% eHTL-oil BPF resole and 50% fHTL-oil BPF resole. Furthermore, bark extraction before liquefaction retarded the curing of the resulted 50% eHTL-oil BPF resole, while HTL-oil fractionation after liquefaction slightly promoted the curing of the resulted 50% eHTL-oil BPF resole. All the three BPF resoles displayed less thermal stability than the neat PF resole, but the effects of bark extraction before liquefaction and HTL-oil fractionation after liquefaction on the thermal stability of the resulted BPF resoles were negligible. All the three BPF resoles could meet the bond strength requirements as adhesives for plywood in accordance to the JIS standard. Bark extraction before liquefaction led to less water resistance for the resulted 50% eHTL-oil BPF resole, while HTL-oil fractionation after liquefaction improved the water resistance of the resulted 50% fHTL-oil BPF resole. [ABSTRACT FROM AUTHOR]

Spent coffee grounds (SCG) were liquefied in hot-compressed water to produce crude bio-oil via hydrothermal liquefaction (HTL) in a 100 cm 3 stainless-steel autoclave reactor in N 2 atmosphere. We investigated the effects of operating parameters such as retention times (5 min, 10 min, 15 min, 20 min and 25 min), reaction temperatures (200 °C, 225 °C, 250 °C, 275 °C and 300 °C), and water/feedstock mass ratios (5:1, 10:1, 15:1 and 20:1) and initial pressure of process gas (2.0 MPa and 0.5 MPa) on the yield and properties of the resulting crude bio-oil. The highest yield of the crude bio-oil (47.3% mass fraction) was obtained at conditions of 275 °C, 10 min retention time and water/feedstock mass ratio of 20:1 with an initial pressure of 2.0 MPa. The elemental analysis of the produced crude bio-oil revealed that the oil product had a higher heating value (HHV) of 31.0 MJ kg −1 , much higher than that of the raw material (20.2 MJ kg −1 ). GC–MS and FT-IR measurements showed that the main volatile compounds in the crude bio-oil were long chain aliphatic acids and esters. [ABSTRACT FROM AUTHOR]

Hydrothermal liquefaction of woody biomass (birchwood sawdust) with and without catalyst was investigated at 300 °C for 30 min. The activities of KOH, FeSO 4 ·7H 2 O, K 2 CO 3 , MgO, synthetic hydrotalcite (HT), and ground colemanite (calcium borate mineral) as catalysts were compared. The alkaline catalysts (KOH, K 2 CO 3 and colemanite) showed the best performance considering the oil yield and solid residue yield. The bio-crude oil yield with KOH was increased to around 40 wt%, more than double the yield of the un-catalyzed operation (∼18 wt%). It also reduced the solid residue yield from approx. 33 to 12 wt%. Among all catalysts tested, the least active catalysts for bio-crude oil production are FeSO 4 and MgO. The bio-crude oil products were comprehensively characterized using an elemental analyzer, GC–MS, FT-IR, GPC and TGA. Occurrence of phenol derivatives (mainly 2-methoxy-phenol) and aliphatic compounds increased significantly in presence of catalysts, especially the alkaline ones such as HT and KOH. The GPC results indicate that the oils produced in the presence of catalysts have very similar molecular weights and distribution, which are slightly greater than the oil produced in absence of any catalyst, suggesting that the presence of a catalyst promoted certain condensation/polymerization of the reaction intermediates during the HTL process. The TGA results show that all bio-crude oils are similar with respect to thermal stability, irrespective of the presence or type of catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two most common biofuels production techniques including fast pyrolysis and HTL arecovered. • The proposed crude bio-oil upgrading approaches are discussed. • Effects of various upgrading parameters on bio-oil HDO are described. • The mechanism for catalyst deactivation and possible solutions are provided. • Chemistry of major bio-oil model compounds during HDO is thoroughly reviewed. Fast pyrolysis and hydrothermal liquefaction (HTL) have been regarded as the most promising thermochemical conversion technologies for liquid bio-fuels production. However, the poor quality of generated crude bio-oils, such as high O and water contents, low thermal stability, and high corrosivity, limits their direct applications as the alternative transportation fuels. Thus, a number of upgrading techniques mainly including chemical and physical methods have been developed. Among them, hydrotreatment like hydrodeoxygenation (HDO) as a well-established technology at petroleum refinery plants has been widely adopted for upgrading of the crude oil obtained from pyrolysis or HTL. In this review, the effects of various upgrading reaction conditions (temperature, H 2 pressure, solvents, residence time, and catalyst) of HDO treatment of real bio-oil and its mode compounds are thoroughly reviewed. In which, the underlying mechanisms for bio-oil HDO are elucidated with a wide range of its model compounds (lignin-derived oxygenates and carbohydrates-derived oxygenates) and the interaction between these model compounds. Moreover, a discussion regarding the HDO of real bio-oil from pyrolysis and HTL is provided, and the technical/operating problems for the catalytic HDO and the possible solutions are presented. Finally, the important knowledge gaps and future directions are addressed for further investigations. [ABSTRACT FROM AUTHOR]

• Effect of Fe on HTL of cornstalk in ethanol–water mixed solvents was investigated. • Maximum oil yield of 50.46 wt% was obtained with Fe at the optimal conditions. • Hydrogenation and deoxygenation were promoted by Fe and mixed solvents. • Oil derived from Fe/mixed solvents mainly consist of phenolics, esters and hydrocarbons. • Effect of Fe in mixed solvents was primarily due to the reaction between Fe and water. In this article, effects of metallic Fe on biocrude oil production from cornstalk via hydrothermal liquefaction (HTL) in ethanol–water mixed solvents were investigated under various conditions. Experiments were conducted in single solvent of water or ethanol using Fe 3 O 4 catalyst to explore the role of metallic Fe in the liquefaction process. The physiochemical properties of the liquefaction products were comprehensively characterized by elemental analysis, GC–MS, FT-IR and XRD. The results showed that the maximum biocrude oil yield (approx. 50 wt%) and higher heating value (HHV) of 30.86 MJ/kg were obtained in ethanol–water mixed solvents (50/50, v/v) at 300 °C for 30 min with 10 wt% Fe loading. It was found that the presence of Fe also promoted the hydrogenation and deoxygenation of liquid products, obtaining biocrude oils mainly consisted of phenolic, ester and hydrocarbon compounds. The positive role of metallic Fe in HTL of biomass in ethanol–water mixed solvents, simultaneously improving the yield and quality of biocrude oil, was believed to be due to in-situ hydrogen formed from the reaction of metallic Fe and water, while the generated Fe 3 O 4 exhibited negligible catalytic effect in the process. [ABSTRACT FROM AUTHOR]

Lignocellulosic biomass is a promising alternative to petroleum oil for producing energy and chemicals, owing to its abundance and sustainability. In the past decades, extensive research has applied a wide range of thermo-chemical technologies for converting biomass into value-added products. Among them, hydrothermal liquefaction (HTL) is regarded to be one of the most effective techniques to produce bio-fuels and bio-based chemicals. However, there are still several technical barriers that must be addressed before the industrialization of HTL technology. Although many previous reviews have summarized the reaction mechanism, properties of liquefaction products, and various operating parameters, few articles have discussed the potential applications of HTL products and the techno-economic problems facing by the industrialization of HTL. Therefore, in this review, the possible applications of HTL products (bio-crude, aqueous phase, solid residue, and gas) were thoroughly discussed. In addition, the current challenges of HTL treatment, especially for the continuous operation, to produce bio-based fuel and chemicals is reviewed. Finally, the possible future directions and the main conclusions are covered. • The benefits and weaknesses of using water as the reaction medium are presented. • The characteristics and potential applications of HTL products are discussed. • Beside bio-crude, by-products from HTL could bring value to HTL. • Critical challenges to the continuous operation of HTL are identified and discussed. [ABSTRACT FROM AUTHOR]

In this work, hydrolysis lignin, as a low-value feedstock, was liquefied in ethanol/water co-solvents (50:50, v /v) at 350 °C for 30 min, with or without the use of hematite ore as the catalyst. Following this, the resulting bio-crude oil was applied as the feedstock for the preparation of neat phenol formaldehyde (PF) resole and bio-phenol formaldehyde (BPF) resoles. The net PF resole was prepared by using the whole bio-crude oil, while, the phenolic extracts from the crude oil together with 50% of phenol were employed for the preparation of BPF resoles. The results displayed that although the BPF resole contained a higher free formaldehyde and less thermally stable than neat PF resole, a lower curing temperature was adopted for BPF resole compared to neat PF resole. By analyzing their physical properties, it was observed that the dry bonding strength of BPF resoles was higher than that of neat PF resole. Most importantly, the dry and wet strengths of BPF resole met the requirements for using as an adhesive for plywood bonding. Overall, it can be concluded that the bio-crude oil-derived phenolic extracts from HTL of hydrolysis lignin is a suitable feedstock for producing value-added BPF with potential use as a wood adhesive. [ABSTRACT FROM AUTHOR]