Tetraselmis suecica culture for CO 2 bioremediation of untreated flue gas from a coal-fired power station N. R. Moheimani 1 Received: 11 October 2015 /Revised and accepted: 16 December 2015 # Springer Science+Business Media Dordrecht 2015 Abstract The accumulation of atmospheric CO 2 , primarily due to combustion of fossil fuels, has been implicated in po- tential global climate change. The high rate of CO 2 bioreme- diation by microalgae has emerged as a favourable method for reducing coal-fired power plant emissions. However, coal- fired power station flue gas contains other chemicals such as SO x which can inhibit microalgal growth. In the current study, the effect of untreated flue gas as a source of inorganic carbon on the growth of Tetraselmis in a 1000 L industrial-scale split- cylinder internal-loop airlift photobioreactor was examined. The culture medium was recycled after each harvest. Tetraselmis suecica grew very well in this airlift photobioreactor during the 7-month experiment using recycled medium from an electroflocculation harvesting unit. Increased medium SO 4 2- concentration as high as 870 mg SO 4 2- L -1 due to flue gas addition and media recycling had no negative effect on the overall growth and productivity of this alga. The potential organic biomass productivity and carbon sequestration using an industrial-scale airlift PBR at International Power Hazelwood, Gippsland, Victoria, Australia, are 178.9 ± 30 mg L - 1 day - 1 and 89.15 ± 20 mg ‘C’ L -1 day -1 , respectively. This study clearly indi- cates the potential of growing Tetraselmis on untreated flue gas and using recycled medium for the purpose of biofuel and CO 2 bioremediation. Keywords Airlift photobioreactor . Recycled medium . Microalgae . Chlorophyta . SO x . Productivity . Biofuel Introduction Atmospheric CO 2 concentration has been increasing rapidly for the past several decades. Carbon dioxide is a contributing factor responsible for over 50 % of the total warming potential of all greenhouse gases (Cox et al. 2000). Current trends in climate change are leading to a series of problems for future generations. Several biological and chemical methods have been proposed for removing atmospheric CO 2 . Photosynthesis is the main biological method for recycling CO 2 while keeping it in the carbon cycle. Microalgae have received an increasing interest in relation to CO 2 recycling and bioremediation due to their ability to grow in saline water and on non-agricultural land (Moheimani et al. 2012). Due to their small size, microalgae are also the fastest growing photosyn- thetic organisms. The microalgal biomass produced in the process of CO 2 bioremediation can be used for making high- value products (e.g. pigments and nutraceuticals; Borowitzka 2013) or low-value commodities (e.g. food and biofuel; Wijffels and Barbosa 2010; Benemann 2013). Closed photobioreactors and open ponds are the two main types of microalgal cultivation systems. Closed photobioreactors are mainly used for producing high-value products, and open ponds constitute the usual cultivation sys- tems used for large-scale outdoor microalgae production (e.g. Dunaliella salina, Arthrospira (Spirulina) platensis, Chlorella vulgaris) (Benemann 2013; Borowitzka and Moheimani 2013a). However, open ponds are not efficient in many loca- tions and they are not suitable for all species of microalgae. Closed photobioreactors (e.g. plate or tubular) require higher capital expenditure, but (at least in theory) they are capable of much higher biomass and lipid productivity and have fewer problems with contamination. Irrespective of the cultivation system to be used (open or closed), there is a need for reliable long-term production for assessing the growth potential of * N. R. Moheimani n.moheimani@murdoch.edu.au 1 Algae R&D Centre, School of Veterinary and Life Sciences, Murdoch University, Murdoch, WA 6150, Australia J Appl Phycol DOI 10.1007/s10811-015-0782-3