From seashells to sustainable energy: Trailblazing the utilization of Anadara uropigimelana shells for sustainable biohydrogen production from leftover cooking oil

Abstract

The pressing planetary predicaments of sustainability, circular economy, and climate change have spurred the exploration of innovative tactics for waste management and sustainable energy production. This study presents an innovative approach for circular economy by utilizing biowaste bivalve shells to produce calcium carbonate (CaCO3), which is then used for biohydrogen production from waste cooking oil. The synthesized CaCO3 was characterized using various analytical techniques. The performance of the CaCO3 (e.g., 200, 400, and 800 mg/L) was compared with that of the surfactant Tween 20 (e.g., 0.5%, 1.0%, and 2.0%), commonly used in biogas production, with an optimized concentration of waste cooking oil at 25%. The results showed that the CaCO3 derived from bivalve shells significantly improved biohydrogen production and reduced process costs. The addition of 2% Tween 20 and 800 mg-CaCO3/L increased hydrogen production potential from 76.25 to 315 and 287 mL-H2, respectively. Carbon conversion efficiency also increased from 62.62 to 78.02% with the addition of 800 mg-CaCO3/L. Comparing with control samples (25% WCO), the treatability study displayed that an addition of 800 mg/L of CaCO3 and 2% Tween 20 has increased the treatment efficiency for COD tot (g/L) by 45.57% and 48.24%, COD sol (g/L) by 42.73% and 47.81%, Oil and grease (g/L) by 22.9% and 25%, respectively. Furthermore, the supplementation of 200 mg/L of CaCO3 and 1% Tween 20 enhanced lipase activity, giving 793 nmol/min and 1608 nmol/min, respectively, compared with 641 nmol/min recorded for the control sample (25% WCO). Overall, this study demonstrates the circular economy approach by repurposing waste materials to generate value-added products, thereby reducing reliance on non-renewable resources.