Simultaneous biogas upgrading and centrate treatment in an outdoors pilot scale high rate algal pond

• DOI: 10.1016/j.biortech.2017.01.071
• Publication Date: 2017-02-11T06:31:32Z
• Authors: Esther Posadas; David Marín; Saúl Blanco; Raquel Lebrero; Raúl Muñoz
• Keywords: Biogas; Bioconversion; Alkalinity

The bioconversion of biogas to biomethane coupled to centrate treatment was evaluated in an outdoors pilot scale high rate algal pond interconnected to an external CO2-H2S absorption column (AC) via settled broth recirculation. CO2-removal efficiencies ranged from 50 to 95% depending on the alkalinity of the cultivation broth and environmental conditions, while a complete H2S removal was achieved regardless of the operational conditions. A maximum CH4 concentration of 94% with a limited O2 and N2 stripping was recorded in the upgraded biogas at recycling liquid/biogas ratios in the AC of 1 and 2. Process operation at a constant biomass productivity of 15gm-2d-1 and the minimization of effluent generation supported high carbon and nutrient recoveries in the harvested biomass (C=66±8%, N=54±18%, P≈100% and S=16±3%). Finally, a low diversity in the structure of the microalgae population was promoted by the environmental and operational conditions imposed.