Current advances in ionic liquid-based pre-treatment and depolymerization of macroalgal biomass

Macroalgae are promising renewable energy resources due to their high biomass production rate, high photosynthetic efficiency, faster growth rate, low lignin content, and higher CO₂ fixation capability. The conventional methods for macroalgae pre-treatment involve energy-intensive processes that require high pressure and elevated temperatures, often requiring alkali or acidic compounds. Recently, ionic liquids are gaining interest as environmentally benign solvents due to their ability to deconstruct the biomass cell wall under relatively milder conditions. In this review, current developments involving IL-based pre-treatment technologies are discussed. A brief background about macroalgae and its traditional pre-treatment methods are presented. Different IL pre-treatment approaches are then discussed, highlighting the dissolution mechanism and selection criteria for an effective IL. Unique pre-treatment strategies, such as acidic ILs, IL blends, task specific ILs and bio-ILs are also explored. Finally, challenges and opportunities related to macroalgae processing using ILs are addressed.