Biodiesel Production from Waste Cooking Oil, Using an Acid Modified Carbon Catalyst Derived from Cassava Peels

An investigation was carried out to study the feasibility of using synthesized acid-bearing carbonaceous catalyst (SO₃H–C and PO₄H₂–C) derived from cassava peel for biodiesel production from waste cooking oil (WCO). The catalyst activity was tested using an autoclave type reactor and three different oil to alcohol ratios (1 : 3, 1 : 5 and 1 : 7) at four different temperatures (50–80°C) for 4 h. Two types of alcohol (i.e. methanol (CH₃OH) and ethanol (C₂H₅OH) were used to understand the efficiency of using alcohol in the process. The study indicates that reaction using high ratio of alcohol (1 : 7) generally produced high yield of the biodiesel compared to other ratios. The yield of the biodiesel also increased with increasing temperature over all the reaction systems. The carbon modified with sulphuric acid catalyst showed the highest yield of ~ 90%, which was obtained at 80°C using a 1 : 7 ratio of WCO : alcohol. It was also observed that reaction with methanol produced better yields compared to ethanol reactions where significant differences were observed across both temperature and ratio. The catalysts were characterized using Fourier transform infrared spectroscopy, X-ray powder diffraction, surface area and pore volume analyses. The catalyst is of interest because it is green, non-toxic and synthesized using cassava peel waste.