The development of technologies to produce fuels from non-fossil sources is of great importance. One of the alternatives is the use of organic biomass feedstock. Hydrothermal liquefaction (HTL) is a technology that enables the transformation of organic matter into bio-crude by means of a reaction in aqueous medium and at high temperature and pressure conditions, although below the critical point of water. Among the different types of organic matter that can be used, marine macroalgae are a very promising feedstock as they are found in abundance within the oceans; in particular, some populations of invasive species cause environmental problems due to their excessive growth beyond their original niche. In fact, large uncontrolled proliferations of algae of the genus Sargassum are found on the coasts of many countries, causing a significant imbalance that affects both the native ecosystems and the tourism sector, which is of great economic importance in the affected areas.
Although there are many variables that influence the process, the objective of this study is to carry out preliminary HTL tests of the mentioned macroalgae specie, without being subjected to previous pre-treatment. In the experimental design, operating variables were temperature, reaction time and initial loading of algal biomass. The objective was to find the highest yield and calorific value of bio-crude produced from this raw material. MODDE® Pro 13 was the software employed for both experimental design and results processing.
All experiments were carried out in a 300 mL volume PARR stirred high pressure reactor. 150 mL of deionized water were used as reaction medium and an inert nitrogen atmosphere was applied. Bio-crude extractions were performed over the solids obtained in the reaction using dichloromethane as solvent. Among the experiments performed, the yields and high heating values (HHV) were compared at different reaction times at a temperature of 300°C and 95 bar pressure, in a time range from 0 to 60 minutes with an initial biomass load of 15 g (10% w/v). The best result obtained was a crude yield of 10.25% and a crude HHV of 9,240 kcal/kg for the 60 minutes HTL test.