# Mechanical Reinforcement of Paper Biocomposites Using Filamentous Cyanobacteria

## TL;DR

This study shows that using cyanobacteria in paper biocomposites can enhance strength and offer a sustainable alternative to traditional cellulose fibers.

## Contribution

The first use of unprocessed cyanobacterial biomass as a cellulose replacement in paper-like biocomposites.

## Key findings

- Cyanobacterial biomass at 3–30% improved or maintained tensile properties of biocomposites.
- The standard biocomposite achieved the highest tensile strength and energy absorption.
- SEM images revealed structural differences due to cyanobacterial content.

## Abstract

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.