Evaluation of Calcium Oxide (CaO) from Oyster Shell Waste: A Sustainable Heat-Generating and Antimicrobial Agent

Oyster shell waste is a source of calcium carbonate (CaCO3) that has the potential to be processed into calcium oxide (CaO) through a calcination process. CaO has various applications, including as a heat-generating agent and antimicrobial. However, proper calcination temperature optimization is needed to obtain CaO with optimal physical and chemical properties. This study aims to optimize CaO production from oyster shell waste and to produce its potential in exothermic and antimicrobial applications The method used involves a calcination process at temperatures of 750, 900, and 1000 °C. The CaO produced was characterized at 750, 900, and 1000 °C. CaO characterization was carried out using Scanning Electron Microscopy (SEM) for morphological analysis, X-Ray Diffraction (XRD) for crystallinity, Fourier Transform Independent Spectroscopy (FTIR) for functional groups, and thermogravimetry (TGA) for thermal stability. The pH test was carried out to determine the basicity, while the antibacterial test used the disc diffusion method against Escherichia coli and Staphylococcus aureus. The results showed that calcination at 1000 °C produced CaO with high purity and porous structure that increased the surface area. The pH stability in the range of 12.5 indicated strong basic properties. CaO produced at 1000 °C exhibited significant exothermic reaction when reacting with air, proving its potential as a heat generating agent (T = 100 °C at 12 min with ∆H = −64.9 kJ/mol). It is also revealed great inhibition against E. coli (1.32 mm) and S. aureus (1.36 mm). In conclusion, oyster shell waste-derived CaO is a highly promising sustainable solution for both heat generation and antimicrobial applications, which strongly supports a circular economy approach in biogenic waste management. HIGHLIGHTS Oyster shell waste is successfully utilized as a sustainable raw material to produce high-purity calcium oxide (CaO). Optimized calcination at 1000 °C yielded CaO with a porous structure and high basicity (pH 12.5), ideal for industrial applications. Produced CaO demonstrated strong exothermic properties (ΔH = −64.9 kJ/mol), reaching 100°C in 12 min upon exposure to air. Exhibited significant antibacterial activity against coli (1.32 mm) and S. aureus (1.36 mm). Supports circular economy by converting biogenic waste into valuable multifunctional materials.