Biodiesel production using waste cooking oil: influence of catalysts on reaction parameters

Abstract

Over a century ago, Rudolf  Diesel tested the used of vegetable oil as fuel for his automotive engine, several years later, bio-based diesel obtain from trans-esterification of animal fats or vegetable oils in presence of catalyst have been used as alternative automotive fuels to safe guard the environment and avoid global warming. Cost of production process has limited the diversification and generalizes usage of biodiesel, thus exploring avenues for cost effective production process. One such approach is to use reusable or recycle substrates such as waste cooking oil (WCO). More so, applied experimental design by parameter manipulation is considered as one of the approaches for the process optimization. In this research, the influence of catalyst type and loading (0.5 -2.5g/100ml of oil) on biodiesel yield and quality was observed.  The study has demonstrated that both NaOH and KOH catalysts performed excellently in biodiesel production. We have observed that increasing catalyst loading beyond 0.5g/100ml of WCO, dramatically reduces biodiesel yield with KOH performing better compared to NaOH.  About 87% biodiesel yield was observed when NaOH was used  in contrast to KOH that catalyzed the production of > 90% biodiesel yield. Increasing catalyst loading resulted in biodiesel production with lower FFA and acid values and moderate specific gravity, with quality parameters similar to that of ASTM standards. The study established that the optimum catalyst loading which produced highest biodiesel in both yield and quality to be 0.5g/100ml of WCO. Furthermore, the study has demonstrated the feasibility of using WCO as substrate to reduce biodiesel production cost, it has also established that catalyst manipulation could be employed to optimize the process efficiently.