Pretreatment of waste frying oil with high levels of free fatty acids for biodiesel production

The decrease of fossil fuel resources and the awareness of the impact of greenhouse gases emissions on the environment have created a need to find alternative energy sources to replace traditional ones. Thus, recent years have seen the development of several sectors of renewable energy production with the government incentives. The production of biodiesel is an alternative of production of non-toxic, clean, renewable and biodegradable fuels. The aim of this work was to investigate the optimum conditions of the biodiesel production from waste frying oil in two-step catalyzed process and the optimization of methanol and acid concentration during its pretreatment. The oil had an acid value of 32.82 mg KOH/g. The first step, an acid was used as a catalyst for the esterification reaction to reduce the free fatty acid content in waste frying oil under 2% that was, with different dosages of the acid. The next base catalyzed transesterification processes converted the pretreated frying oil to biodiesel with the optimum combination. The highest yield of biodiesel after transesterification and purification process was 98% ester content with 0.214% of free fatty acid. The results showed that the acid catalysis a promising pretreatment to acidic oils or fats as they led to the production of an intermediary material with a low content of free fatty acid that can be directly used in the transesterification reaction for the production of biodiesel.