New candidate for biofuel feedstock beyond terrestrial biomass for thermo-chemical process (pyrolysis/gasification) enhanced by carbon dioxide (CO2)

► Thermo-chemical process of macroalgae. ► Enhanced pyrolysis/gasification by utilizing CO2 as a reaction medium. ► Significant tar reduction under the presence of CO2. ► Modification of end products under the presence of CO2. The enhanced thermo-chemical process (i.e., pyrolysis/gasification) of various macroalgae using carbon dioxide (CO2) as a reaction medium was mainly investigated. The enhanced thermo-chemical process was achieved by expediting the thermal cracking of volatile chemical species derived from the thermal degradation of the macroalgae. This process enables the modification of the end products from the thermo-chemical process and significant reduction of the amount of condensable hydrocarbons (i.e., tar, ∼50%), thereby directly increasing the efficiency of the gasification process.