Study of the Reuse of Eggshells in the Production of Bioplastics with Soil Enrichment Potential

Abstract

This comprehensive study investigated the significant potential of eggshell, a readily available calcium-rich bio-waste, as an effective and sustainable additive in bioplastics. This innovative approach aims to substantially improve soil fertility during the material's biodegradation, while concurrently mitigating the environmental impacts associated with conventional limestone mining, the traditional source of calcium, as well as addressing the disposal of fossil-derived plastics. The robust methodology involved preparing plant-based raw materials, developing prototypes with systematic variations in composition and concentration, and comprehensively characterizing the formulated biomaterial. Analyses included precise thickness measurements and rigorous soil biodegradation tests through mass loss coupled with calcium carbonate equivalent (CaCO₃) quantification and carbon dioxide (CO₂) emission monitoring. The formulations were systematically studied at concentrations of 0%, 0.25%, 0.5%, and 1% eggshell, with thicknesses ranging from 0.37846 mm to 0.53594 mm. The biomaterials demonstrated promising average soil biodegradation rates of 52.42%, 51.26%, 52.94%, and 57.64% for concentrations of 0%, 0.25%, 0.5%, and 1%, respectively. During the 16 days of biodegradation, the samples released an average of 102.36, 117.55, 128.87, and 138.84 g kg⁻¹ of CaCO₃. These values disregard the baseline CaCO₃ (g kg⁻¹) value found in the soil without the presence of the samples, and it is possible to observe a consistent growing trend in the quantity of this essential nutrient that directly accompanies the increase in eggshell concentration in the formulation. The average aerobic biodegradability rate corresponded to 44.70% within a 14-day interval. Thus, eggshell presented itself as a strong potential additive in bioplastics, enabling formulations that are simultaneously biodegradable and capable of fertilizing the soil.