Assessment of the CO2 fixation capacity of Anabaena sp. ATCC 33047 outdoor cultures in vertical flat-panel reactors

•The efficiency of CO2 capture and conversion into biomass by cultures of Anabaena has been assessed both indoors and outdoors.•Outdoor cultures have been simultaneously operated in different reactor types throughout a full year.•The observed differential performance of the cultures depends upon the peculiarities of the particular reactor.•On a per area basis, cultures in flat-panel reactor performed better than in either open pond or tubular horizontal reactor.•The appropriate culture of Anabaena in flat-panel reactor represents a most suitable system for CO2 capture and conversion.

The extent of biological CO2 fixation was evaluated for outdoor cultures of the cyanobacterium Anabaena sp. ATCC 33047. Culture conditions were optimized indoors in bubble-column photochemostats operating in continuous mode, subjected to irradiance cycles mimicking the light regime outdoors. Highest values achieved for CO2 fixation rate and biomass productivity were 1 and 0.6 g L−1 day−1, respectively. The comparison among different reactors operating simultaneously – open pond, horizontal tubular reactor and vertical flat-panel – allowed to assess their relative efficiency for the outdoor development of Anabaena cultures. Despite the higher volumetric CO2 fixation capacity (and biomass productivity) exhibited by the tubular photobioreactor, yield of the flat-panel reactor was 50% higher than that of the tubular option on a per area basis, reaching values over 35 g CO2 fixed m−2 d−1. The flat-panel reactor actually represents a most suitable system for CO2 capture coupled to the generation of valuable biomass by Anabaena cultures.