Introduction Facing with the fossil fuel depletion and environmental issues, microalgae is one of the promising biofuel sources due to its high lipid content and growth rate. However, the microalgal biodiesel has not been commercialized yet due to the high cost of the production. To save the production cost, in-situ transesterification is applied by integrating extraction and transesterification steps. In this study, N.gaditana (12.05wt% of lipid content), ethanol, chloroform and sulfuric acid catalyst were mixed into a test tube and the tube was placed in a heating bath at a specific temperature range of 100 – 130 oC for 2 hours. After reaction, the tube was cooled down and neutralized by NaOH solution. 1 ml chloroform containing 0.5 mg standard reagent was added to the test tube for the GC analysis. The tube was centrifuged for 10 min to separate the phases and the organic phase was picked for GC/MS analyses. Result and Discussion In-situ transesterification is performed under the acid catalyst at high temperatures. Simultaneously, the hydrolysis of glucose from cellulose occurs with levulinic acid and formic acid generated. By esterification reaction of these acids with ethanol, EF and EL are by-products with fatty acid esters biodiesel product. Furthermore, ethanol dehydration can occur with DEE produced. The higher reaction temperature and higher ethanol amount, the more EF, EL and DEE are produced for higher acid concentration. Water can shift the reverse transesterification, therefore wet microalgae showed lower biodiesel yield. Also it discourages the dehydration of HMF which is necessary reaction to produce EF and EL. Reaction medium is a bi-phasic system. FAEE, EL and EF exist in the organic phase, while ethanol, DEE and glycerol exist in the water phase. Since chloroform can facilitate the mass transfer for FAEE, EL and EF, their yield was increased as more chloroform was added. Conclusions In-situ transesterification of N.gaditana integrates lipid extraction-conversion process allowing more economic feasibility of biodiesel production. Above 110oC, cellulose-derived by-product (EL and EF) and ethanol-derived by-product (DEE) are noticeably produced. The yield of biodiesel and by-products has been affected by the amounts of chloroform (co-solvent), ethanol, and sulfuric acid. This work can improve the biodiesel value chain with concurrent production of EF, EL and DEE.

Simultaneous production of biodiesel and valuable co-products from in-situ transesterification of wet microalgae

253rd National Meeting (2017)

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