Alkaline and Acid Catalyzed Transesterification Bioprocess in Biodiesel Preparation from Fresh Water Algae

Abstract

The study was carried out to investigate the biodiesel yield and quality with different alkaline and acid catalysts from algae. Algal species, Spirogyra was used to produce biodiesel applying the alkaline and acid transesterification process. A single homogenous catalyst (KOH) and heterogenous mixture of catalysts (KOH+NaOH+H2SO4) were treated to obtain a high quality biodiesel fuel that complied with the specifications of the American Standard Testing and Material, ASTM D 6751 and European Norm, EN 14214 standards. The biodiesel yield and the physical and chemical properties of produced biodiesel were evaluated. The highest biodiesel yield of 96.9% was achieved dealing 1:3 volumetric oil-to-methanol proportions by 1.5% mixture of catalysts (NaOH+KOH+H2SO4) at 40°C reaction temperature and a stirring speed of 320 rpm. Biodiesel formation yielded a lower at the rate of 94.9% biodiesel in a single catalyst than in the mixture of catalysts (96.9%). There was no significant difference in the viscosity of the biodiesel produced between the single and mixture of catalysts. However, the total acid number and metal (Na, Ca, Mg, Cu) content differed significantly between the homogenous and heterogenous catalysts of produced biodiesel. There was more methyl ester (biodiesel yield) of biodiesel produced in the mixture of catalysts compared to the biodiesel formed applying a single catalyst. The results showed that biodiesel obtained from Spirogyra sp., under optimum conditions through alkaline and acid bioprocess transesterification was of good quality that could be practiced as a source of diesel fuel.