Comparative evaluation of microalgae strains for CO2 capture purposes

Abstract

In this paper we have compared eleven microalgae/cyanobacteria strains used for the development of a CO2 capture process. Firstly, we studied the tolerance of the selected strains to the water quality available at the production site. The results confirmed that no toxins were present in the water used; in addition, we confirmed that fertilizers could be utilised as the nutrient source instead of pure chemicals. Secondly, the strains were evaluated in terms of growth rate, biomass productivity and photosynthetic efficiency concluding that Scenedesmus almeriensis, Neochloris oleoabundans and bloom from the River Seine were the most productive, above 1.0 g·L−1·day−1. Thirdly, we determined the biochemical composition of the biomass with the results showing that most of the strains mainly accumulate carbohydrates in the stationary phase, over 60% d.wt.; the exceptions were Neochloris oleoabundans and Chlorella vulgaris, which accumulate lipids, above 20% d.wt. In any case, the performance of the microalgae strains was better than that of cyanobacteria both in terms of biomass productivity and the biochemical composition; consequently, using these types of microorganisms is recommended. By considering a fixed value for the main biomass components, we concluded that the most promising strains were Scenedesmus almeriensis, Neochloris oleoabundans and bloom from the River Seine, yielding a biomass value above 0.6 €·kg−1 and an economic value higher than 0.7 €·m-3·day−1. These figures confirm that, in order to obtain profitable CO2 capture processes and to develop more efficient production systems that reduce current production costs, coupling with wastewater treatment schemes is required.