Optimisation of biodiesel production from waste vegetable oil and eggshell ash

Abstract

While biodiesel has potential in resolving current energy crisis, its production is hampered by both feedstock and catalyst availability. The aim of this study is to investigate the production of biodiesel from waste vegetable oil (WVO) characterised by high free fatty acid (FFA) as feedstock with heterogeneous catalysis via transesterification reaction. The catalyst used was obtained from eggshell calcined at 800 °C. The properties of the catalyst were assessed using XRD, XRF, BET and SEM. The catalyst prepared was characterised to have large pore diameter of 91.2 Å and high surface area of 30.7 m2 g−1. The optimisation study was carried out by using a central composite response surface methodology with reaction conditions of methanol to oil ratio, catalyst loading and reaction temperature. The result showed at 95% confidence level that all the three factors affected the methyl ester yield. Significant yield of 91% was obtained at optimal operating conditions of temperature (65 ± 5 °C), methanol to oil molar ratio (22.5:1) reaction time (5 h 30 min) and catalyst loading (3.5 wt%). The catalyst showed sustained activity after being recycled and reused for 10 times. The properties of the biodiesel produced were within the biodiesel standard specifications.