The characteristics of bio-oil produced from the pyrolysis of three marine macroalgae

The pyrolysis of two brown macroalgae (Undaria pinnatifida and Laminaria japonica) and one red macroalgae (Porphyra tenera) was investigated for the production of bio-oil within the temperature range of 300-600°C. Macroalgae differ from lignocellulosic land biomass in their constitutional compounds and high N, S and ash contents. The maximum production of bio-oil was achieved at 500°C, with yields between 37.5 and 47.4wt.%. The main compounds in bio-oils vary between macroalgae and are greatly different from those of land biomass, especially in the presence of many nitrogen-containing compounds. Of the gaseous products, CO₂ was dominant, while C₁-C₄ hydrocarbons gradually increasing at 400°C and above. The pretreatment of macroalgae by acid washing effectively reduced the ash content. The pyrolysis of macroalgae offers a new opportunity for feedstock production; however, the utilization of bio-oil as a fuel product needs further assessment.