Quaternary blend of Carica papaya - Citrus sinesis - Hibiscus sabdariffa - Waste used oil for biodiesel synthesis using CaO-based catalyst derived from binary mix of Lattorina littorea and Mactra coralline shell

Waste eggshell was investigated in triglyceride transesterification with a view to determine its viability as a solid catalyst for use in biodiesel synthesis. Effect of calcination temperature on structure and activity of eggshell catalysts was investigated. Reusability of eggshell catalysts was also examined. It was found that high active, reusable solid catalyst was obtained by just calcining eggshell. Utilization of eggshell as a catalyst for biodiesel production not only provides a cost-effective and environmental friendly way of recycling this solid eggshell waste, significantly reducing its environmental effects, but also reduces the price of biodiesel to make biodiesel competitive with petroleum diesel.