Optimisation of biodiesel production from Eisenia fetida earthworms oil using the transesterification method

ABSTRACT The current study was performed for the optimisation of the biodiesel production from E. fetida earthworms oil using the transesterification method. Rice husk was sulphonated by sulphuric acid and it was identified by the Fourier Transform Infrared Spectrometer (FTIR) technique and Scanning Electron Microscope (SEM) image. The effects of reaction temperature (50–70°C), alcohol-to-oil molar ratio (9:1–15:1), catalyst amount (3–5 wt%) and residence time (1–3 h) on fatty acid methyl esters (FAME) yield were assessed. Response Surface Methodology (RSM) was used to assess the actual and predicted FAME values. The results of the FTIR technique showed the presence of different surface functional groups (silanol, hydroxyl, etc.) on the silica-based catalyst. The results for SEM image showed fine spherical particles. A good agreement between actual and predicted values for FAME yield was observed. The optimal conditions of the parameters for FAME yield obtained from the software were as follows: reaction temperature = 68.53°C, methanol to oil molar ratio = 13.73:1, catalyst amount = 3.43 wt% and residence time = 3 h. Under optimal conditions, FAME yield reached to 93.2%. The theoretical FAME yield predicted under the above conditions was 94.68%. GRAPHICAL ABSTRACT