Kinetic and thermodynamic studies on biodiesel production from Spirulina platensis algae biomass using single stage extraction-transesterification process

Biodiesel production from nonedible feedstocks is gaining attention in the recent years as they do not interfere with the global food economy. In this investigation, Spirulina platensis algae biomass was used as the feedstock for biodiesel production. Single stage extraction-transesterification was carried out with an aim to study the effect of reaction temperature, catalyst concentration, algae biomass to methanol ratio (wt:vol), stirring intensity and algae drying duration on the biodiesel yield. The optimum conditions for maximum biodiesel yield (75 ± 0.40%) were found to be 90 min duration for algae drying, 60% catalyst concentration, 1:4 algae biomass to methanol ratio, 450 rpm stirring intensity and 55 °C reaction temperature. The experimental data appeared to be a good fit with the first order reaction kinetics. For the reaction studied at different temperatures, values of rate constant and activation energy were found out to be 0.001 min−1 and 14518.51 J/mol respectively. The values of thermodynamic parameters such as Gibbs free energy (ΔG), enthalpy of activation (ΔH) and entropy of activation (ΔS) were also determined. The positive values of ΔG and ΔH and negative value of ΔS indicated the unspontaneous and endergonic nature of the reaction.