The present study introduced an integrated method for the production of biodiesel from microalgal oil. Heterotrophic growth of
Chlorella protothecoides resulted in the accumulation of high lipid content (55%) in cells. Large amount of microalgal oil was effi-
ciently extracted from these heterotrophic cells by using n-hexane. Biodiesel comparable to conventional diesel was obtained from
heterotrophic microalgal oil by acidic transesterification. The best process combination The use of renewable energy sources is becoming increasingly necessary to mitigate global warming. Recently much research
has been focused on identifying suitable biomass species, which can provide high-energy outputs, to replace conventional fossil
fuels. This paper reports an approach for increasing the yield of bio-oil production from fast pyrolysis after manipulating the
metabolic pathway in microalgae through heterotrophic growth. The yield of bio-oil (57.9%) produced from heterotrophic
Chlorella protothecoides cells was 3.4 times higher than from autotrophic cells by fast pyrolysis. The bio-oil was characterized
by a much lower oxygen content, with a higher heating value (41 MJ kg−1), a lower density (0.92 kg l−1), and lower viscosity
(0.02 Pa s) compared to those of bio-oil from autotrophic cells and wood. These properties are comparable to fossil oil. The
research could contribute to the creation of a system to produce energy from microalgae, and also could have great commercial
potential for liquid fuel production