ABSTRACT
Microalgae have emerged as a potential feedstock for the production of biodiesel. The steps involved in the production of bio-oil and biodiesel from microalgae include cultivation, harvesting, dewatering and concentrating microalgae, extraction of oil/lipids from the microalgae, and separation of triglycerides and free fatty acids from the crude lipids (for the synthesis of biodiesel). The nal step consists of pyrolysis or thermochemical catalytic liquefaction for the production of bio-oil and esterication or
8.1 Introduction ....................................................................................................99 8.2 Esterication/Transesterication .................................................................. 101 8.3 Thermochemical ........................................................................................... 103 8.4 World Scenario on Production and Application of Biodiesel ....................... 108 8.5 Biofuel/Biodiesel from Microalgal Oil as a Potential Alternative to
Other Fuels.................................................................................................... 109 8.6 Conclusion .................................................................................................... 110 Acknowledgments .................................................................................................. 110 References .............................................................................................................. 110
transesterication for the synthesis of biodiesel. The species of microalgae employed for the production of biofuel include Chlorella vulgaris, Chlorella sorokiniana, Sargassum patens C., and Spirulina. The method of biodiesel production from algal biomass can be done either by direct transesterication or in two steps involving the extraction of oil from algae followed by transesterication. Economic in situ transesterication of the microalgae has been adopted that involves combining the two steps of lipid extraction and transesterication into a single step. Direct transesterication of the microalgae after cell disruption by sonication resulted in a high conversion of biodiesel (97.25%). The fuel properties of the biodiesel synthesized from the microalgal oil derived from Chlorella protothecoides showed high fuel quality with a cold lter plugging point of −13°C. A high composition of unsaturated fatty acid methyl ester content in the microalgal oil methyl esters (MOME) (i.e., 90.7 wt%) led to a low oxidation stability of the fuel (4.5 h). The chemical treatment, pyrolysis, or thermochemical catalytic liquefaction of microalgal oil for the synthesis of bio-oil eliminates the dewatering and drying steps. The major constituents of bio-oil obtained from brown microalgae Sargassum patens C. Agardh by hydrothermal liquefaction consist of carbon (64.64%), followed by oxygen (22.04%), hydrogen (7.35%), nitrogen (2.45%), and sulfur (0.67%).
