The objective of this study was to examine the hydrothermal liquefaction of sugarcane bagasse using ethanol and black liquor (BL) in a pilot scale. Combinations of co-solvents (ethanol/ water, ethanol/BL) were studied at various concentrations and reaction conditions. The maximum oil yield of 61% was achieved with a reaction temperature of 300 °C for 30 min and using pure BL as a solvent, while the highest higher heating value (HHV) was obtained from a 50:50 ethanol-BL mixture. The oils contained alcohols, esters, phenolic compounds, aromatics, and heterocyclics. The O/C and H/C ratios of the oil were comparable with traditional biodiesel and commercial diesel. Although this study showed there are some improvements to be made to improve the chemical composition, the approach has potential for large-scale production of a substitute for fossil-fuel-based diesel.

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The stability of biocrude produced from the liquefaction of sugarcane bagasse in ethanol was observed. The degradation characteristics of biocrude and reference fuels, such as diesel, waste cooking oil biodiesel, and their blends, were studied under three different storage environments and temperatures over 24 weeks, namely, hot (43 °C), cold (4 °C), and outdoor (variable temperature) conditions. Higher Heating Values of biocrude had only small changes for all storage conditions, and this was similar to the behavior of the reference fuels. Density changes were significant in hot conditions for biocrude oil compared with outdoor and cold conditions. The change in chemical composition reflects changes in densities. Upon different storage conditions, the chemical composition of waste cooking oil biodiesel and biocrude changed considerably over the time period, whereas diesel and biodiesel blend B20 remained relatively stable. The instability of the biocrude was mainly due to oxygenated compounds, especially phenols forming cyclic and aromatic compounds. The degradation rate of biocrude was the slowest in cold conditions.

As a biofuel feedstock, microalgae has good scalability and potential to supply a significant proportion of world energy compared to most types of biofuel feedstock. Hydrothermal liquefaction (HTL) is well-suited to wet biomass (such as microalgae) as it greatly reduces the energy requirements associated with dewatering and drying. This article presents experimental analyses of chemical and physical properties of bio-crude oil produced via HTL using a high growth-rate microalga Scenedesmus sp. in a large batch reactor. The overarching goal was to investigate the suitability of microalgae HTL bio-crude produced in a large batch reactor for direct application in marine diesel engines. To this end we characterized the chemical and physical properties of the bio-crudes produced. HTL literature mostly reports work using very small batch reactors which are preferred by researchers, so there are few experimental and parametric measurements for bio-crude physical properties, such as viscosity and density. In the course of this study, a difference between traditionally calculated values and measured values was noted. In the parametric study, the bio-crude viscosity was significantly closer to regular diesel and biodiesel standards than transesterified (FAME) microalgae biodiesel. Under optimised conditions, HTL bio-crude's high density (0.97-1.04 kg·L −1 ) and its high viscosity (70.77-73.89 mm 2 ·s −1 ) had enough similarity to marine heavy fuels. although the measured higher heating value, HHV, was lower (29.8 MJ·kg −1 ). The reaction temperature was explored in the range 280-350 • C and bio-crude oil yield and HHV reached their maxima at the highest temperature. Slurry concentration was explored between 15% and 30% at this temperature and the best HHV, O:C, and N:C were found to occur at 25%. Two solvents (dichloromethane and n-hexane) were used to recover the bio-crude oil, affecting the yield and chemical composition of the bio-crude.