Development of biodegradable and vermicompostable films based on alginate and waste eggshells

The development of biofilms to replace plastics is urgent, due to the high environmental pollution caused by the non-biodegradable packaging. The objective of this study was to develop and understand the behavior and properties of biodegradable films based on an alginate/glycerol matrix with eggshell waste. Eggshells were transformed to eggshell powder (EP) and this ingredient used to obtain EP biodegradable films (EPBFs) using the casting method. EP contributed opacity and whitish coloration to the EPBFs. Stress-strain curves show that EP content significantly influences mechanical properties; resulting in harder, firmer and less elastic EPBFs with increasing EP content. The EPBFs had heterogeneous and rough surfaces with crystalline forms provided by EP with a particle size distribution ranged from 20.7 to 26.6 μm, arranged as a monolithic pattern with very low porosity. EPBFs were amorphous materials and WAXS analysis indicated that CaCO3 content ranged 18–50% in the EPBFs. Thermal decomposition processes of the EPBFs, was not affected by the EP addition at concentrations below 6%. The addition of EP increased the hydrophobicity of EPBFs, slowing solubilization in water; however, the water solubility percentage was high (82.9% for EPBF-2%–75.2% for EPBF-6%). EPBFs completely biodegrade in vermicomposting in short periods of time (between 14 and 21 days). In conclusion, EPBFs, derived from waste, constitute an interesting new material with desirable mechanical properties for potential use as food coatings or packaging. The biodegradable properties of EPBFs allow easy disposal by dissolving in water or by vermicomposting.