In the context of the escalating global demand for energy and the mounting environmental concerns associated with fossil fuels, bio-oil emerges as a promising candidate for renewable energy sources, exhibiting considerable potential for application and future development. It is evident that microalgae have become a pivotal feedstock for bio-oil production, owing to their rapid growth rate, substantial oil content, and non-competitive nature with cropland. The present study investigated the effects of feedstock loading (6–15 g), reaction pressure (9.9–19.7 MPa) on the bio-oil yield, elemental composition, boiling point, and constituent components of the hydrothermal liquefaction products from Chlorella vulgaris. As the reaction pressure increased from 9.9 to 19.7 MPa, the bio-oil yield increased from 36.97 to 43.28 wt%. Concurrently, the contents of N and O in the bio-oil decreased by 11.19 % and 25.26 %, respectively. The hydrocarbon content exhibited a decline in the low-boiling-point fraction (≤300 °C) of the bio-oil. It has been demonstrated that the presence of NO-containing compounds, including hexadecylamide and octadecylamide, is directly proportional to the increase in reaction pressure. It was observed that both increasing the load of feedstock and pre-filling with helium gas produced similar effects on bio-oil. However, it was found that increasing feedstock loading exerted a greater influence on bio-oil yield and quality. This study establishes a foundation for future exploration and optimisation of high solid content hydrothermal liquefaction of Chlorella vulgaris. © 2025 Elsevier Ltd

Pyrolysis oils with different effective hydrogen (H/Ceff) ratios are mixed with tetralin at a mass ratio of 1:1 and treated at 400 °C for 2 h under 6 MPa H2 over Pt/C and Ru/C, respectively, to examine the effect of H/Ceff ratio on the yield and quality of the upgraded oil. Pyrolysis oil with higher H/Ceff ratios results in an upgraded oil with higher yield and H/Ceff ratios. The highest S and O reduction ratios of 96.11% and 56.26% are achieved with added Pt/C at an H/Ceff ratio of 1.39 of the feedstock. In comparison, the highest N reduction ratios of 34.50% is achieved with added Ru/C at an H/Ceff ratio of 1.38 of the feedstock. The N and S poison the catalyst's active sites and reduce the deoxygenation efficiency. Thus, we view that the H/Ceff plays a vital role in improving the properties of the bio-oil. © 2022 Hydrogen Energy Publications LLC

The hydrothermal liquefaction reaction was carried out with Chlorella vulgaris as the feedstock, which has a high solid content (20-100 wt %). The effects of the reaction temperature (250-350 degrees C) and solid content on the characteristics of bio-oil (including yield, higher heating value (HHV), and elemental composition) were studied via central composite design (CCD) and response surface methodology (RSM) to model the relationships among these variables. This study reliably established a reaction model via response surface analysis, and the optimum reaction conditions calculated from the model were 350 degrees C and 59.04 wt % feedstock, resulting in a 37.94 wt % bio-oil yield, 37.36 MJ/kg HHV, 8.07 wt % N content, 0.375 wt % S content, and 6.69 wt % O content, respectively. Increasing the solid content under high-temperature conditions can effectively reduce the content of heteroatoms in bio-oil. GC-MS analysis of the bio-oil revealed a substantial increase in the concentrations of saturated hydrocarbons, unsaturated hydrocarbons, aliphatic alcohols, and aromatic compounds with increasing solid content. The most notable increase was observed for aromatic compounds, with a corresponding increase in content of up to 27.63%. The main condensation reaction occurs during the gradual increase in solid content, resulting in a hexadecanamide content of up to 10.84% at a solid content of 60 wt %. As the solid content increases beyond this point, the components in the bio-oil undergo a noticeable dehydration reaction, leading to a gradual increase in the hexadecanenitrile content to 4.33%, while the fatty acid content decreases. This change facilitates the subsequent hydrodesorption of heteroatoms.

In this study, the gasification performance of different kinds of lignocellulosic biomass, including corn straw (CS), soybean straw (SS), cotton straw (CTS), rice straw (RS), wheat straw (WS), bamboo wood (BW), maple sawdust (MS), and pine sawdust (PS), was studied in a tube furnace reactor system under identical conditions (temperature = 800 °C, oxygen flow rate = 30 mL/min, steam flow rate = 5 ± 1 mL/min, and time = 55 min). SS showed good gasification characteristics and delivered the highest H2 yield of 28.96 mol/kg. By using the SS, additional optimization was carried out by considering different temperatures (650, 700, 750, 850, 950, and 1050 °C) and different oxygen flow rates (10, 20, 30, 40, and 50 mL/min). After optimization, the initial temperature and oxygen concentration were reduced to 750 °C and 10 mL/min, respectively. An H2 yield of 30.86 mol/kg was achieved with an increase of 6.56 %. Finally, catalytic steam gasification employing three potassium-based catalysts, KCl, KOH, and K2CO3 was tested using SS. KOH and K2CO3 performed distinctly better than KCl. The utilization of KOH as a catalyst resulted in the greatest H2 yield, measuring 39.22 mol/kg, which represents a notable improvement of 27.09 %. © 2024 Elsevier Ltd

In this study, four crude bio-oils (CBOs) obtained from hydrothermal liquefaction of soybean straw (SS), peanut straw (PS), corn straw (CS) and rice straw (RS) were hydrotreated with various amounts of n-hexane. Then the obtained oil was separated into light oil (LO) and heavy oil (HO) by centrifugation. The LO yields increased from 53.89 to 59.15 wt% to 76.25–78.54 wt% when the mass ratio of n-hexane to CBO (wnH/wCBO) increased from 1:1–3:1. Despite containing the least asphaltenes, the hydrotreating of SS-CBO with n-hexane produced the lowest LO yield and the highest solid yield. The obtained LOs were mainly composed of saturated hydrocarbons, aromatics, and phenolic compounds, which showed obviously higher saturation and HHVs, also lower O and N contents than the corresponding HOs. Further hydrotreating of LOs resulted in significantly higher yields of upgraded light oils (ULO), falling in a narrower range of 92.04–93.48 wt%. The N and S content (26–503 ppm and © 2024 Elsevier B.V.

The environmental impact of production-use studies of calabash seed oil (CSO) biodiesel and its modeling with the adaptive neuro-fuzzy inference system (ANFIS) are scarce. Therefore, it is difficult to determine how much the production process and exhaust emissions together contribute to the total environmental footprint during CSO biodiesel synthesis and use. This study examines the environmental impacts of using a CSO biodiesel blend (B20) and low-sulfur diesel (LSB0) in a 15-kW test bed at full load. It employs a life cycle assessment (LCA) tool to evaluate and compare their effects. This study also utilizes ANFIS modeling to gain a better understanding of the production process. The results revealed a 38.5 wt% CSO content in the seeds, with an unsaturated fatty acid content of approximately 77.38%. The ANFIS model revealed that a high cetane number, purity, yield, and lower viscosity could be obtained using a methanol-oil ratio (10:1–12:1), temperature (55–60 °C) and catalyst dosage (5–6 wt%). The engine performance tests showed that CSO-derived B20 has a significantly better fuel economy of approximately 13.2% than LSB0, with an improved thermal efficiency of 41.6% and reduced CO and HC emissions of 60% and 31.4%, respectively. The LCA results show that the most significant environmental impacts were found in the global warming potential, ecotoxicity potential, acidification potential, and eutrophication potential categories, with impact reductions of 52%, 49%, 68%, and 58%, respectively. The LCA analysis shows that the CSO-derived B20 has the potential to promote sustainable, cleaner, and more efficient energy sources. © 2024 Elsevier Ltd

The integration of optimization techniques and deep learning models, which offer a promising avenue for improving the efficiency and sustainability of biodiesel production processes from baobab seed oil (BSO), is rare. This study utilized a multi-input-multioutput (MIMO) deep learning technique and the most recent central composite design (CCD) optimization tool to model and optimize the yield and properties of biodiesel produced from BSO. First, the baobab seed oil was extracted using a solvent extraction method. BSO was subsequently analyzed and converted to biodiesel by reacting CH3OH catalyzed by waste banana bunch stalk biochar activated by KOH. Multiobjective optimization and prediction of the biodiesel yield (Y) and several key fuel properties, including the cetane number (CN), kinematic viscosity (VS), and purity (P), were achieved. With better correlation coefficients of 0.9709, 0.9464, and 0.9714 for response training, response testing, and response validation, respectively, and a root-mean-square error of 0.00755, the MIMO model on the logsig transfer function accurately predicted the biodiesel yield and properties more than did the MISO and response surface methodology models. The optimum Y (96 wt %), CN (48), VS (3.3 mm2/s), and P (98.3%) were concurrently accomplished at a reaction temperature of 56 degrees C, a reaction time of 115 min, a CH3OH/BSO molar ratio of 15:1, a catalyst dosage of 6 wt %, and a stirring speed of 400 rpm with 98% optimal validation accuracy. CCD sensitivity analysis revealed that the CH3OH/BSO ratio was the most sensitive (50.9%) input predictor among the other input variables studied.

In this study, the crude bio-oil (CBO) obtained from hydrothermal liquefaction of peanut straw was separated into light oil (LO) and heavy oil (HO) by molecular distillation at 130 ℃ and different pressures (0.5, 1 and 3 kPa). With process variables fixed, the CBO and its distillates were subjected to catalytic hydrotreating to probe the behavior characteristics of CBO from straws during this process. The LO yield fluctuated between 29.8 and 34.8 wt% with the change of distillation pressure. LO presented lower C content and higher H and O content than the corresponding HO. The LO obtained at 1 kPa showed a significant content difference between ketones (34.50%) and phenolic compounds (5.84%), indicating the differential distribution of these chemical components in CBO and the possibility of component separation by molecular distillation. Hydrotreating of LO gained obviously higher yield of upgraded oil (82.1–89.7 wt%) and lower yield of solid (6.1–9.1 wt%) than the corresponding HO (61.2–69.4 wt% and 21.3–24.6 wt%, respectively). The addition of n-hexane in the hydrotreating of HO led to an increase in hydrocarbon content and a decrease in content of phenolic compounds in the upgraded oil, although it did not contribute to increasing the upgraded oil yield. © 2023 Elsevier B.V.

In this study, soybean straw (SS) was subjected to a steam explosion to produce pretreated soybean straw (PSS). Food waste was used to make a liquor with a lower layer (LL) and an upper layer (UL). Hydrothermal liquefaction (HTL) of SS and PSS was performed in deionized water (DW), LL, and UL at 320 °C for 30 min. The highest bio-oil yield was obtained by conducting HTL in the UL, with SS accounting for 31.30 wt% yield and PSS accounting for 31.77 wt% of the bio-oil yield; this result may be due to the high gas content of the UL. Moreover, conducting HTL in the LL produced lowest bio-oil yield, which was only 15.30 wt% bio-oil yield for PSS. Bio-oil is not suitable for direct use as a fuel because of its high nitrogen content. However, bio-oil consists mainly of ketones and phenols and is therefore a promising feedstock for the production of high-value-added chemicals. PSS is high in lignin and therefore produces more hydrochar than SS. The hydrochar produced from PSS has a higher heating value (HHV) ranging from 27 to 28 MJ/kg and can be used as green biocoal. PSS could also be used as a feedstock to reduce the gaseous product yield, especially the water-soluble product yield. The gaseous products mainly consisted of CO2, CO, H2, N2, CH4, and C2H6, among which CO2 and CO accounted for more than 95 %. Compared to the products obtained by HTL from PSS, there were more acetic acid, ketones and fewer phenolic substances in the water-soluble products obtained by HTL from SS. © 2023 Elsevier Ltd

This work examined the effects of reaction solvent (water/ethanol) and nitrogen source (pyridine/pyrrole) on synthesising N-doped carbon material via a hydrothermal process. The presence of water favored the carbonization of cellulose and doped the nitrogen of pyridine in the form of pyridinic-N and graphitic-N via Maillard reaction, while almost no carbonization and nitrogen doping were observed either in pure pyridine or in pyridine and ethanol mixture. Increasing temperature and the water/pyridine ratio enhanced the carbonization of cellulose and the Maillard reaction between cellulose and pyridine. The N-doped carbon (NC1) derived from the activation of the hydrochar produced at 240 °C for 1 h with a pyridine:water ratio of (5 mL:35 mL) exhibited a significant specific surface area of 544.91 m2/g and a specific capacitance of 214.1 F/g (at 1 A/g) under the three-electrode system. With employing the aqueous phase derived from the above reaction, the derived N-doped carbon (NC2) exhibited a specific surface area of 534.29 m2/g and a specific capacitance of 189.7 F/g. The time constant of NC1 (0.5 s) was higher than that of NC2 (0.28 s), suggesting NC2 operates more quickly in the process of reversible charge-discharge. Over 10,000 cycles at 5 A/g, NC1 maintained 97.82 % of the capacitance, while for NC2, the capacitance retention reached 106 %. Exploring pyrrole in the place of pyridine provided a high yield and high N content of the hydrochars and NCs, but the electrochemical performances were significantly lowered. This work suggests a low-cost and sustainable method for the preparation of N-doped carbon materials for supercapacitors. © 2023 Elsevier Ltd