Mechanical Reinforcement of Paper Biocomposites Using Filamentous Cyanobacteria

Rising concerns over plastic packaging and the growing demand for e-commerce have increased paper-based materials production, thereby intensifying environmental impacts of the paper industry, one of the most polluting industries worldwide. The need to source nonwood fibers to alleviate environmental pressure has brought microalgae into the spotlight as a sustainable and renewable resource. For the first time, this study proposes and evaluates replacing cellulose fibers in paper-like biocomposites with the cyanobacterium Leptolyngbya sp. SB090721. The effect of using cyanobacteria as a cellulose replacement (0%, 3%, 30% w/w) was evaluated. Addition of cyanobacterial biomass (3-30%) maintained or enhanced tensile properties. The standard biocomposite showed the highest tensile strength (4.8 kN·m^-1) and tensile energy absorption (195.63 J·m^-2). Both the standard and high biomass composites showed enhanced elasticity moduli of 997.1 and 903.4 MPa. Significant structural differences were observed on the SEM micrographs, with the high biomass specimen displaying a distinct structure, attributed to its elevated cyanobacterial content. In conclusion, the study confirmed the feasibility of using unprocessed cyanobacterial biomass as a nonwood fiber source for paper and paperboard materials. This reduces the amount of cellulose used in the paper industry, offering new properties and production routes that could potentially be more sustainable.