초록
<P><B>Abstract</B></P> <P>This study aimed to improve methane content in biogas by feeding biogas through the culture of oleaginous microalgae. As oleaginous microalgae have ability to mitigate CO<SUB>2</SUB> into lipids and accumulate at the content >20%, this process not only contributes to CO<SUB>2</SUB> removal from biogas but also producing microalgal biofuel. Among the species tested, <I>Scenedesmus</I> sp. and marine <I>Chlorella</I> sp. are suitable for this purpose. However, <I>Scenedesmus</I> sp. was selected due to the higher CO<SUB>2</SUB> removal ability and the optimized conditions were as follows: gas flow rate of 0.3 L h<SUP>−1</SUP> per 1 L- microalgal culture inoculated with 10<SUP>7</SUP> microalgal cells mL<SUP>−1</SUP>, added with KNO<SUB>3</SUB> 0.8 g L<SUP>−1</SUP> as nitrogen source and illuminated at 5.5 klux light intensity. Under these conditions, methane content in biogas was increased from 60% up to >90% coupled with lipid productivity of 88.57 mg L<SUP>−1</SUP> day<SUP>−1</SUP>. With the strategy of stepwise-increasing gas flow rate to support the increasing biomass, the final biomass and lipid productivity were 1.25 and 1.79 folds increased. CO<SUB>2</SUB> removal rate was as high as 5.097 g-CO<SUB>2</SUB> day<SUP>−1</SUP> per 1 L-microalgal culture. Fuel properties calculated based on fatty acid composition indicated high oxidation stability and high ignition quality of the microalgal lipids-derived biodiesel.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CO<SUB>2</SUB> in biogas could be efficiently removed by oleaginous microalgae. </LI> <LI> After process optimization, methane content in biogas could be increased >90%. </LI> <LI> Stepwise-increased gas flow rate enhanced CO<SUB>2</SUB> removal rate and lipid productivity. </LI> <LI> Microalgal lipids-derived biodiesel showed good fuel properties. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>