Application of Calcined Clamshells as Natural Adsorbents in the Refining of Used Cooking Oil

Abstract

The disposal of waste cooking oil (WCO) poses significant environmental challenges due to its contribution to water pollution and greenhouse gas emissions. This study evaluates the potential of calcined clamshells as a sustainable, low-cost natural adsorbent for refining WCO. Bleaching earth was prepared from untreated clamshells (CS) and furnace-calcined clamshells (FCS) through thermal treatment and applied during the bleaching stage of oil refining at dosages of 0.5%, 1.0%, and 1.5%. The refined oil was assessed based on free fatty acid (FFA) content, moisture content, and colour. The results demonstrated that FCS exhibited superior adsorption performance compared with untreated clamshells. The optimum treatment reduced FFA to 0.06% and achieved moisture content as low as 0.08%, meeting Malaysian Palm Oil Board (MPOB) quality standards, while also improving the colour of the refined oil. The findings indicate that thermally activated clamshells provide an environmentally friendly alternative to conventional bleaching earth by converting seafood waste into a value-added material for oil purification. This approach supports sustainable waste management, resource recovery, and circular economy initiatives while offering a promising solution for improving the quality of recycled cooking oil.