초록
<P>The influence of biogas flow rate (0, 0.3, 0.6, and 1.2 m<SUP>3</SUP> m<SUP>–2</SUP> h<SUP>–1</SUP>) on the elemental and macromolecular composition of the algal-bacterial biomass produced from biogas upgrading in a 180 L photobioreactor interconnected to a 2.5 L external bubbled absorption column was investigated using diluted anaerobically digested vinasse as cultivation medium. The influence of the external liquid recirculation/biogas ratio (0.5 < <I>L</I>/<I>G</I> < 67) on the removal of CO<SUB>2</SUB> and H<SUB>2</SUB>S, and on the concentrations of O<SUB>2</SUB> and N<SUB>2</SUB> in the upgraded biogas, was also evaluated. A <I>L</I>/<I>G</I> ratio of 10 was considered optimum to support CO<SUB>2</SUB> and H<SUB>2</SUB>S removals of 80% and 100%, respectively, at all biogas flow rates tested. Biomass productivity increased at increasing biogas flow rate, with a maximum of 12 ± 1 g m<SUP>–2</SUP> d<SUP>–1</SUP> at 1.2 m<SUP>3</SUP> m<SUP>–2</SUP> h<SUP>–1</SUP>, while the C, N, and P biomass content remained constant at 49 ± 2%, 9 ± 0%, and 1 ± 0%, respectively, over the 175 days of experimentation. The high carbohydrate contents (60–76%), inversely correlated to biogas flow rates, would allow the production of ≈100 L of ethanol per 1000 m<SUP>3</SUP> of biogas upgraded under a biorefinery process approach.</P><P><B>Graphic Abstract</B><BR><IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/esthag/2015/esthag.2015.49.issue-5/es5056116/production/images/medium/es-2014-056116_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/es5056116'>ACS Electronic Supporting Info</A></P>