Coconut Shell as an Alternative Fuel for Hydrotalcite Catalyst Synthesis via the Combustion Method for Biodiesel Production from Waste Cooking Oil

Using saccharose (sugar) as fuel to synthesise hydrotalcite via the combustion method to produce biodiesel could potentially have social and economic benefits in the field of renewable energy. However, it could spark a debate on food vs fuel since a higher demand for saccharose in the energy sector while ensuring adequate supply for the food sector could increase the price of saccharose. Therefore, this study proposes utilising a new alternative material from agricultural waste, coconut shell, to synthesise the hydrotalcite catalyst and use it to produce biodiesel from waste cooking oil. This study found that the hydrotalcite synthesised using coconut shell as fuel and calcined at 650 ℃ (HT-CS 650) yielded 93.25% biodiesel compared to the 74.14% biodiesel yield when synthesising hydrotalcite using saccharose. The XRD showed that the synthesised hydrotalcite retained its layered double hydroxide structure up to 650 °C calcination temperature. The BET analysis showed that the HT-CS 650 has the highest surface area of 115.558 m<sup>2</sup>/g compared to the 28.326 m<sup>2</sup>/g surface area of the reference hydrotalcite (HT-SS 650). The HT-CS 650 can be reused for up to three cycles with a minimum biodiesel yield reduction of 9.09%. This study has demonstrated that agricultural waste is a more suitable fuel for synthesising hydrotalcite in the combustion method and using it to improve the transesterification reaction for biodiesel production.