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The continued growth and evolving lifestyles of the human population require the urgent development of sustainable production in all its aspects. Microalgae have the potential of the sustainable production of various commodities; however, the energetic requirements of algae cultivation still largely contribute to the overall negative balance of many operation plants. Here, we evaluate energetic efficiency of biomass and lipids production by Chlorella pyrenoidosa in multi-tubular, helical-tubular, and flat-panel airlift pilot scale photobioreactors, placed in an indoor environment of greenhouse laboratory in Central Europe. Our results show that the main energy consumption was related to the maintenance of constant light intensity in the flat-panel photobioreactor and the culture circulation in the helical-tubular photobioreactor. The specific power input ranged between 0.79 W L−1 in the multi-tubular photobioreactor and 6.8 W L−1 in the flat-panel photobioreactor. The construction of multi-tubular photobioreactor allowed for the lowest energy requirements but also predetermined the highest temperature sensitivity and led to a significant reduction of Chlorella productivity in extraordinary warm summers 2018 and 2019. To meet the requirements of sustainable yearlong microalgal production in the context of global change, further development towards hybrid microalgal cultivation systems, combining the advantages of open and closed systems, can be expected. [ABSTRACT FROM AUTHOR]

The increasing CO 2 emissions have a massive impact on the environment causing global warming due to the greenhouse effect. This leads to the effort of the society to minimize CO 2 production as well as CO 2 emissions mitigation by secondary measures to achieve sustainable and cleaner industrial production. Currently, research focuses on various methods for CO 2 capture or mitigation from stationary industrial emission sources, such as waste-to-energy plants (WTEP), fossil fuel power plants, steel mills, cement plants, or refineries. One of the promising potential methods is the use of microalgae for biological CO 2 fixation from flue gas through photosynthesis. With this vision, a vertical photobioreactor with elliptical tubes was developed, designed and implemented. This novel type of bioreactor using oval-shaped tubes, thus avoiding self-shading limitation, was used for experimental pilot-scale flue gas CO 2 abatement verification. Flue gas composition was selected according to pollutants (CO, CO 2 , NO, SO 2) on the outlet of the waste-to-energy plants. According to the suitable algae screening results, Chlorella pyrenoidosa Chick was used for cultivation. The biomass yield and CO 2 fixation efficiency were experimentally obtained for optimal conditions and this new photobioreactor type. The results were compared to the available publications for Chlorella sp. and flue gas as the source of CO 2. The best-achieved biomass productivities were 0.51 and 0.13 g L−1 d−1 with corresponding CO 2 biofixation rates of 0.95 and 0.25 g L−1 D−1, respectively, for laboratory and pilot-scale. The results of this study allowed us to expand knowledge about high CO 2 WTEP flu gas utilization as the carbon source for algae cultivation using novel PBR tubing. Also data about other minor flue gas pollutants (CO, NO, SO 2) absorption in the cultivation medium contributes to an expansion of knowledge for algae cultivation using waste gas sources. [Display omitted] • Novel vertical tubular photobioreactor using oval-shaped tubes. • Pilot cultivation provided high value of biomass growth rate (0.13 g L−1 D−1). • CO, NO and SO 2 absorption into the cultivation medium was observed. • Successful waste-to-energy plant simulated flue gas CO 2 mitigation. • Flue gas CO 2 mitigation contributes to sustainable and cleaner production. [ABSTRACT FROM AUTHOR]