<P><B>Abstract</B></P> <P>This study has shown the strategies to upgrade biogas and produce lipids as biodiesel feedstocks by cultivation of oleaginous microalgae. Three important growth factors for microalgae including light intensity, nitrogen source and CO<SUB>2</SUB> supply, were strategically stepwise-increased during cultivation. The stepwise-increasing of CO<SUB>2</SUB> supply was suitable for cell growth and lipid production while the stepwise-increasing of light intensity was more suitable for CO<SUB>2</SUB> removal efficiency. Among the strategies attempted, the simultaneous stepwise-increasing of all three growth factors most effectively enhanced the performance of microalgae. Through this strategy, >96% of CO<SUB>2</SUB> was continuously removed from biogas and the CH<SUB>4</SUB> content in the purified biogas was >98%. This process also generated microalgal biomass at 4.40 ± 0.04 g L<SUP>−1</SUP> with a lipid content of 34.10 ± 2.26%. The CO<SUB>2</SUB> removal rate by this process was as high as 6.50 ± 0.21 g-CO<SUB>2</SUB> day<SUP>−1</SUP> per 1 L microalgal culture. The microalgal lipids contained long chain fatty acids (C16C18) >94% and their prospect fuel properties indicated their suitable use as biodiesel feedstocks. The integrated processes and strategies in this study would contribute greatly to the production of biogas and biodiesel feedstocks.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Oleaginous microalgae could purify biogas and simultaneously produce lipids. </LI> <LI> Stepwise-increasing of growth factors successfully enhanced microalgae performance. </LI> <LI> Simultaneous increasing of growth factors most enhanced biogas purification process. </LI> <LI> Estimated fuel properties of microalgal lipids meet the international standards. </LI> </UL> </P>