Carbon Dioxide Removal Dilemma of Macroalgae Products: Evidence from Carbon Footprint and Profitability

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. [Display omitted] •“Cradle-to-grave” life cycle assessment is performed for macroalgae products•No existing macroalgae products can sequestrate CO2 if they are used in society•The product processing stage contributes most carbon footprint•Achieving emission-negative is possible with production improvement in future•Macroalgae products’ commodity utility and carbon offset utility are mutual-exclusive