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The utilization of renewable fuel alternatives holds promise for reducing the financial burden of regulatory compliance and the social responsibility associated with greenhouse gas emissions. Hydrothermal liquefaction (HTL) is one of the most versatile technologies for converting renewable biomass feedstocks (especially in the wet state) into biofuel (biocrude oil) in a compact plant. Therefore, this review is devoted to thoroughly reviewing and critically discussing biocrude oil production from biomass feedstocks through the HTL process. This review starts by discussing the principles of biomass HTL processing and product upgrading, aiming to provide a grounded and broad understanding of current developments in this domain. The data reported in the published literature are analyzed and visualized in order to scrutinize the effects of the main process parameters on the quantity, quality, cost, and environmental impacts of resultant biofuels. Higher biocrude oil yields are obtained at temperatures, pressures, and residual times between 300 and 350 °C, 24–27 MPa, and 15–25 min, respectively. Concerning yield and calorific value, biocrude oil derived from homogeneous catalysts demonstrates figures of 23.6 % and 32.1 MJ/kg, whereas that from heterogeneous catalysts exhibits percentages of 66.8 % and 40 MJ/kg, respectively. The challenges and prospects for the future development of biocrude oil are also discussed. HTL has a long way to go before being used for biofuel production on a large scale. Future studies appear to be directed towards the use of HTL technology under the biorefinery framework to maximize the exploitation of biomass into value-added products, while minimizing waste generation. [Display omitted] • Biocrude oil production from biomass by hydrothermal liquefaction is reviewed. • The principles of hydrothermal liquefaction and biocrude oil upgrading are discussed. • The effects of the main parameters on various aspects of biocrude oil are investigated. • The higher biocrude oil yields are obtained at 300–350 °C, 24–27 MPa, and 15–25 min. • Environmental and economic aspects of biocrude oil production are thoroughly discussed. [ABSTRACT FROM AUTHOR]

The current study examines the efficiency of double metals (Cd and Mn) impregnated montmorillonite clay (Cd-Mn-Mmt) catalyst for the cleaner synthesis of biodiesel from novel non-edible seed oil of Prunus Cerasoides D. Don. (seed oil content 54.5%, and FFA content 0.45 mg KOH/g). X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX) and Fourier Transform Infrared Radiation Spectroscopy (FTIR) were used for characterizing the newly synthesized catalyst. The highest (85%) fatty acid methyl ester yield (FAME) of Prunus Cerasoides D. Don. biodiesel was obtained at optimized transesterification reaction conditions; 5 h of reaction time at 120 °C, 12:1 M ratio of methanol to oil and 4% catalyst loading. Synthesized biodiesel was further characterized via FTIR, Gas Chromatography/Mass spectroscopy (GC/MS), and Nuclear magnetic resonance (NMR (1H, 13C)). Additionally, the determined fuel properties, such as density (0.8612 kg/L), kinematic viscosity (4.11 mm2/s), flash point (73 °C), cloud point (−9 °C) and pour point (−10 °C), of synthesized biodiesel, agreed with International Standards of China GB/T 20828 (2007), American (ASTM-951, 6751) and European Union (EU-14214). Pseudo-first-order kinetics fitted well with the experimental data (R2 = 0.9172). The study findings recommended that the modified montmorillonite clay catalyst is a cleaner, cheaper, and easy to use along with high stability and catalytic performance in the transesterification process. • Potential of novel Prunus cerasoides seed oil as renewable energy. • Maximum biodiesel yield of 85% was obtained at reaction temperature of 120 °C. • The optimum methanol/oil ratio of 12:1 at 4.0% catalyst loading for 5 h was observed. • Pseudo-first-order kinetics was found fit with experimental data (R2 = 0.9172). • Clay-based catalyst exhibited cost effectiveness and high stability during the reaction. [ABSTRACT FROM AUTHOR]

Liquid transportation biofuel production is a promising strategy to reduce greenhouse gas emissions. Hydrothermal gasification (HTG) has shown great potential as an effective method for valorizing wet biomass. The high-quality syngas produced using the HTG process can be chemically/biochemically converted to liquid biofuels. Therefore, this paper aims to comprehensively review and critically discuss syngas production from biomass using the HTG process and its conversion into liquid biofuels. The basics and mechanisms of biomass HTG processing are first detailed to provide a comprehensive and deep understanding of the process. Second, the effects of the main operating parameters on the performance of the HTG process are numerically analyzed and mechanistically discussed. The syngas cleaning/conditioning and Fischer-Tropsch (FT) synthesis are then detailed, aiming to produce liquid biofuels. The economic performance and environmental impacts of liquid biofuels using the HTG-FT route are evaluated. Finally, the challenges and prospects for future development in this field are presented. Overall, the maximum total gas yield in the HTG process is obtained at temperature, pressure, and residence time in the range of 450–500 °C, 28–30 MPa, and 30–60 min, respectively. The highest C 5+ liquid hydrocarbon selectivity in the FT process is achieved at temperatures between 200 and 240 °C. Generally, effective conversion of biomass to syngas using the HTG process and its successful upgrading using the FT process can offer a viable route for producing liquid biofuels. Future studies should use HTG technology in the biorefinery context to maximize biomass valorization and minimize waste generation. [Display omitted] • Syngas production from biomass using hydrothermal gasification is thoroughly reviewed. • Conversion of syngas into liquid biofuels using Fischer-Tropsch synthesis is discussed. • The mechanisms of hydrothermal gasification and Fischer-Tropsch synthesis are detailed. • The economic and environmental aspects of biofuel production from syngas are evaluated. • The challenges and prospects for future development in this field are highlighted. [ABSTRACT FROM AUTHOR]