Algal Biomaterials From Recycled Wastewater Biomass

Abstract

Fabricating high-performance, binder-free biomaterials from microalgae grown during wastewater treatment is an opportunity in sustainable materials. However, the impact of strain morphology and mechanical preprocessing on material properties remains largely uncharacterized. This study investigates binder-free biomaterials fabricated from wastewater-grown, filamentous Tribonema minus and food-grade, unicellular Chlorella vulgaris. The impact of three mechanical comminution methods (ball mill, mortar-and-pestle, and speed mixer) on the mechanical properties is evaluated. The results demonstrate that feedstock morphology and processing are critical, interacting factors. Under gentle comminution (mortar-and-pestle), filamentous Tribonema biomaterials exhibit significantly higher flexural modulus and strength than unicellular Chlorella. Conversely, high-shear speed mixing diminishes Tribonema's structural advantage while enhancing Chlorella's particle packing, leading to a convergence in mechanical properties. All final biomaterials exhibit near-hydrophobic surfaces (contact angles > 85°). This research validates that non-food-competing wastewater algae can be transformed into high-performance biomaterials, yielding materials with densities of ≈1.0–1.1 g/cm³ and flexural moduli ranging from ≈0.3 to 1.0 GPa.