title: Microalgal-biotechnology as a platform for an integral biogas upgrading and nutrient removal from anaerobic effluents.
abstract: The potential of a pilot high rate algal pond (HRAP) interconnected via liquid recirculation with an external absorption column for the simultaneous removal of H2S and CO2 from biogas using an alkaliphilic microalgal-bacterial consortium was evaluated. A bubble column was preferred as external absorption unit to a packed bed column based on its ease of operation, despite showing a comparable CO2 mass transfer capacity. When the combined HRAP-bubble column system was operated under continuous mode with mineral salt medium at a biogas residence time of 30 min in the absorption column, the system removed 100% of the H2S (up to 5000 ppmv) and 90% of the CO2 supplied, with O2 concentrations in the upgraded biogas below 0.2%. The use of diluted centrates as a free nutrient source resulted in a gradual decrease in CO2 removal to steady values of 40%, while H2S removal remained at 100%. The anaerobic digestion of the algal-bacterial biomass produced during biogas upgrading resulted in a CH4 yield of 0.21-0.27 L/gVS, which could satisfy up to 60% of the overall energy demand for biogas upgrading. This proof of concept study confirmed that algal-bacterial photobioreactors can support an integral upgrading without biogas contamination, with a net negative CO2 footprint, energy production, and a reduction of the eutrophication potential of the residual anaerobic effluents.
authors.affiliation: Department of Chemical Engineering and Environmental Technology, University of Valladolid , C/Dr. Mergelina s/n, 47011 Valladolid, Spain.
authors.forename: Melanie
authors.initials: M
authors.lastname: Bahr
authors.forename: Ignacio
authors.initials: I
authors.lastname: Díaz
authors.forename: Antonio
authors.initials: A
authors.lastname: Dominguez
authors.forename: Armando
authors.initials: A
authors.lastname: González Sánchez
authors.forename: Raul
authors.initials: R
authors.lastname: Muñoz
mesh_terms: D065966:Absorption, Physicochemical; D000693:Anaerobiosis; D056804:Biofuels / Q000032:analysis* / Q000592:standards; D018533:Biomass; D001709:Biotechnology / Q000295:instrumentation / Q000379:methods; D002245:Carbon Dioxide / Q000302:isolation & purification*; D006862:Hydrogen Sulfide / Q000302:isolation & purification*; D058086:Microalgae / Q000737:chemistry* / Q000254:growth & development; D058433:Photobioreactors; D061005:Ponds / Q000382:microbiology; D053545:Spirulina / Q000737:chemistry / Q000254:growth & development
chemical_list: D056804:Biofuels; D002245:Carbon Dioxide; D006862:Hydrogen Sulfide