Optimizing chlorella vulgaris cultivation in an airlift photobioreactor using coconut oil mill effluent (COME) for biodiesel production

Abstract

Energy sources have become intertwined with human survival because of our dependance on them for our basic needs. Of these, hydrocarbon fuels are regarded as the most essential source of energy, owing to their ease of transportation and wide range of applications. The majority of biofuel research is now focused on algae. Since algal biofuel doesn't contain any hazardous materials, the environment may be kept clean after burning these fuels. In this work, biodiesel is produced using the microalga Chlorella vulgaris. The goal of this study is to employ coconut oil mill effluent (COME), as a substrate for the development of algae and the generation of lipids. An airlift bioreactor was developed for the productive growth of Chlorella based on the output specifications and design standards for an efficient gas-liquid mass transfer capability. The amount and quality of microalgal lipid content can be affected by modifications to the growth environment or the composition of the medium. It was carried out to improve the physical surroundings and media for efficient lipid production in algae. The effects of COME, dissolved oxygen, photoperiod, and pH were evaluated during its growth. The conditions that resulted in the fastest growth rate were pH 3, a temperature of 25 °C, flow rate 0.6 L/L/min and illumination with a white light-emitting diode (LED) at 7000 lux. On day 10, the highest lipid content is achieved at 25.78%. 1.5 ml of biodiesel were generated from 5 g of dried C. vulgaris algal biomass. The widely used Folch method, used to extract lipid from various sources and produce biodiesel, can be combined with the transesterification procedure to produce biodiesel. The compounds that are present in the biodiesel's composition are identified, and their quantities were calculated using the GC-MS technique. Several characterization tests, including the pH test, iodine test, flame test, acid value test, and saponification value test, were carried out. These tests' findings show that the produced biodiesel satisfied ASTM specifications.