Comparative analysis of various waste cooking oils for esterification and transesterification processes to produce biodiesel

Abstract

This study is focused on the production of biodiesel from waste cooking oils to turn the waste into energy by biological means. Physicochemical analysis of the oil samples was performed by measuring their density, acid value and saponification value for evaluating their efficacy towards biodiesel synthesis. Metal catalyzed glycerolysis and acid catalyzed esterification was carried out to reduce the free fatty acid number of oils. Transesterification of treated oils was done by using different alkalis and lipase (free and immobilized) as catalysts. Furthermore, the impact of all the reaction parameters including time, temperature, catalysts and methanol concentration was observed. Biodiesel was purified by wet and dry washing. Maximum product formation was achieved with 1% potassium hydroxide (KOH) followed by 4% free lipase and 6% immobilized lipase. Chemical composition analysis by gas chromatography and mass spectrometry (GCMS) showed the presences of about 97 and 93% fatty acid methyl esters for KOH and lipase based biodiesel, respectively. Fuel properties including distillation temperature, kinematic viscosity, flash, fire, cloud and pour point of the final product were found in accordance with the standard American Society Testing and Materials biodiesel specifications.

Keywords

• distillation temperature
• fire point
• exhaust emissions
• immobilization
• pour point
• re-esterification