High Captured Carbon Content Bioplastic Film from Spirulina

Abstract Bioplastics offer a solution to the problem of increasing atmospheric CO₂ levels contributed by the linear production and consumption pattern of fossil‐derived plastics by closing the carbon loop with material sourcing from biomass and bioplastic's biodegradability. Spirulina, a genus of cyanobacteria that is capable of rapid CO₂ uptake, can be the key to realizing a circular plastic economy by converting atmospheric CO₂ to value‐added high protein content biomass, from which the protein can be extracted and processed to produce protein‐based bioplastics with high captured carbon content that is biodegradable, releasing CO₂ after decomposition to be returned to the cycle. To demonstrate the feasibility of utilizing the self‐assembling capabilities of Spirulina protein to fabricate bioplastics, a simple procedure is proposed that involves protein isoelectric point precipitation followed by solvent casting to produce an entirely Spirulina protein‐based bioplastic film containing glycerol as the plasticizer without blending with other types of conventional plastics. By further crosslinking with carboxymethylcellulose and Ca²⁺ cations, are able to obtain films with the highest average tensile strength of 5.5MPa. Additionally, the Spirulina protein films showed potential in UV‐blocking applications and exhibited good biodegradability.