Carbon dioxide removal dilemma of macroalgae products: Evidence from carbon footprint and profitability

Abstract

Macroalgae can bio-sequester atmospheric CO₂ into their biomass, thus it has been proposed and debated as a viable carbon dioxide removal strategy to mitigate climate change. We examine the carbon footprints of common macroalgae products through a “cradle-to-grave” life cycle assessment, and find carbon sequestration effect can only be accomplished by some specific macroalgae product types when they are properly stored rather than being used. We identify the product processing and usage stages in macroalgae’s life cycle contribute most carbon emissions, while the net primary production of macroalgae during growth only partially neutralizes its overall CO₂ emissions. A sensitivity test for such life cycle model indicates employing clean energy and improving technical efficiency can potentially achieve net-zero for some macroalgae products e.g., biochar. However, even considering macroalgae’s ecological values, our profitability investigation concludes that macroalgae products for carbon sequestration are extremely unattractive to practitioners under current carbon pricing level.