Pyrolysis of macroalgal biomass: A comprehensive review on bio-oil, biochar, and biosyngas production

Aquatic biomass has garnered global attention for its potential as a renewable energy source and its environmental benefits. Among various conversion technologies, pyrolysis stands out as one of the most efficient, converting biomass into solid, liquid, and gaseous products with high potential for energy applications. This study provides a comprehensive analysis of different pyrolysis methods in the context of macroalgae processing. It explores how operating parameters, such as temperature, heating rate, and residence time, influence the yield and quality of pyrolysis products, biochar, bio-oil and gas. The findings demonstrate that slow pyrolysis, conducted at lower temperatures and longer residence times, yields higher biochar, while fast pyrolysis, with higher temperatures and shorter residence times maximizes bio-oil production. Intermediate pyrolysis balances biochar and bio-oil outputs, whereas flash pyrolysis favors biofuel production with faster heating rates. Catalytic fast pyrolysis demonstrates strong potential for producing high-value hydrocarbons. Microwave-assisted pyrolysis of macroalgae produces significant syngas and bio-oil with high heating values and lower oxygen content. Additionally, co-pyrolysis with suitable co-feedstocks further enhances bio-oil properties. This study highlights the potential of macroalgae as a renewable resource, emphasizing the versatile applications of pyrolysis products. Harvesting macroalgae during the peak growth, optimizing pyrolysis parameters, integrating complementary techniques, and using efficient catalysts can significantly enhance conversion and yields. Developing cost-effective, sustainable methods—by reducing energy use, minimizing emissions, and ensuring responsible feedstock management—is essential to improve reaction efficiency and product functionality.