Hydrothermal liquefaction of Caulerpa sertularioides: Optimized biocrude production and characterization with pretreatment techniques

Hydrothermal liquefaction (HTL) is presented as an eco-friendly method for producing biocrude from algal biomass, specifically macroalgae, which are abundant resources but often overlooked for biofuel production. This research aimed to create sustainable fuel from macroalgae and explored HTL product yields alongside ultrasonic and microwave pretreatments. Focusing on the green macroalga Caulerpa sertularioides in a batch reactor, the study used response surface methodology to analyze operational parameters like temperature (250-350 degrees C), pressure (50-150 bar), and feedstock concentration (3-10 wt%). Optimal conditions were identified at 350 degrees C, 150 bar, and 9.75 wt% feed concentration, achieving a biocrude yield of 22.15 wt%. The biocrude showed a high heating value of 39.17 MJ/kg with energy recovery at 73.19 %. Predominantly consisting of complex cyclic compounds such as acids and ketones, about 35.79 % of biocrude components have boiling points similar to standard diesel oil. However, an upgrading process is necessary due to the high oxygen content. Pretreatment using microwave and ultrasonication at 350 degrees C did not enhance biocrude yield.