Optimization of bio-oil production from macroalgae, caulerpa lentillifera via hydrothermal liquefaction

Abstract

An environmentally friendly method of producing bio-oil through the hydrothermal liquefaction (HTL) of algae has emerged, providing a path toward renewable energy and reducing greenhouse gas emissions. Algae is currently received a lot of interest as biomass feedstock due to its long growing season in warm climate area, does not require arable land, and relatively rapid growing rate. This study aims to optimize the HTL process of macroalgae (Caulerpa lentillifera) for bio-oil production, focusing on optimizing the bio-oil yield based on three parameters (operating temperature, the loading size of catalyst sodium hydroxide (NaOH), and algae-to-water ratio) using Box Behnken Design (also generally known as Response Surface Methodology). The results showed that an ideal reaction temperature of 277 °C, a 1:10 algae-to-water ratio, and 0.88 wt% catalyst loading led to an optimal experimental bio-oil yield of 11.65 wt%. Sensitivity study also revealed that the temperature is the second most important component, after the algae-to-water ratio. The difference in the catalyst loading showed low impact on the HTL of algae. Slight improvement to the bio-oil yield under the presence of NaOH is mainly due to the alkali environment provided by NaOH. The FTIR spectrum revealed the existence of various functional groups in the bio-oil. In summary, HTL has been effective in turning Caulerpa lentillifera into useful bio-oil. Overall, this study contributes to the growing body of research on algae-based bio-oil production. The results highlighted the potential of HTL as a promising technology for sustainable biofuel production, offering a pathway towards a greener and more energy-efficient future.