The bioactive materials in brown seaweeds hold great interest for developing new drugs and healthy foods. The oil content in brown seaweeds (Saccharina japonica and Sargassum horneri) was extracted by using environmentally friendly supercritical CO₂ (SC-CO₂) with ethanol as a co-solvent in a semi-batch flow extraction process and compared the results with a conventional extraction process using hexane, ethanol, and acetone mixed with methanol (1:1, v/v). The SC-CO₂ method was used at a temperature of 45 °C and pressure of 250 bar. The flow rate of CO₂ (27 g/min) was constant for the entire extraction period of 2 h. The obtained oil from the brown seaweeds was analyzed to determine their valuable compounds such as fatty acids, phenolic compounds, fucoxanthin and biological properties including antioxidant, antimicrobial, and antihypertension effects. The amounts of fucoxanthin extracted from the SC-CO₂ oils of S. japonica and S. horneri were 0.41 ± 0.05 and 0.77 ± 0.07 mg/g, respectively. High antihypertensive activity was detected when using mixed acetone and methanol, whereas the phenolic content and antioxidant property were higher in the oil extracted by SC-CO₂. The acetone–methanol mix extracts exhibited better antimicrobial activities than those obtained by other means. Thus, the SC-CO₂ extraction process appears to be a good method for obtaining valuable compounds from both brown seaweeds, and showed stronger biological activity than that obtained by the conventional extraction process.

Volatile fatty acids (VFAs) are produced by fermentation of various bio-sources and human wastes at minimal cost; sometimes, even sources having a prepaid processing fee were used. However, low concentrations of VFAs in water have prevented their commercial production, even with modern separation technologies, due to the high operating costs. We have applied newly developed solvents, selected by chemical structure similarity, to the separation of five different VFAs. Since most of the water was separated by extraction using hexyl acetate and nonyl acetate, the utilities necessary for solvent recovery and product purification were a fraction of those required by the existing VFAs’ separation processes. The solvents separated almost all the water in the feed at the extraction stage, consuming no energy. The energy use in this study is only 34% of the lowest case use among various processes of either distillation-only or combined extraction–distillation. The performance evaluation of the proposed VFAs separation process showed that product recovery was 99% and acid purity was 99.5% with eco-scores of 70% lower than those of the current processes.

Biomass conversion via pyrolysis has been regarded as a promising solution for bio-oil production. Compared to fossil fuels, however, the pyrolysis bio-oils from biomass are corrosive and unstable due to relatively high oxygen content. Thus, an upgrading of bio-oil is required to reduce O component while improving stability in order to use it directly as fuel sources or in industrial processes for synthesizing chemicals. The catalytic hydrodeoxygenation (HDO) is considered as one of the promising methods for upgrading pyrolysis bio-oil. In this research, the HDO was studied for various catalysts (HZSM-5, metal, and metal-phosphide catalysts) to improve the quality of bio-oil produced by fast pyrolysis of Saccharina japonica (SJ) in a fluidized-bed reactor. The HDO processing was carried out in an autoclave at 350 °C and different initial pressures (3, 6, and 15 bar). During HDO, the oxygen species in the bio-oil was removed primarily via formation of CO₂ and H₂O. Among the gases produced through HDO, CO₂ was observed to be most abundant. The C/O ratio of produced bio-oil increased when CoMoP/γ-Al₂O_3, Co/γ-Al₂O₃, Fe/γ-Al₂O₃, or HZSM-5 was used. The Co/γ-Al₂O₃ resulted in higher HDO performance than other catalysts. The bio-oil upgraded with Co/γ-Al₂O₃ showed high HHV (34.41 MJ/kg). With the use of catalysts, the kerosene-diesel fraction (carbon number C₁₂–C₁₄) was increased from 36.17 to 38.62–48.92 wt.%.