Green technologies for air pollution treatment by microalgae in tubular photobioreactor

Air pollution in general and motorcycle exhaust, in particular, is a big problem attracting a lot of attention from people and researchers worldwide because of the significant impacts it has on humans and the environment. The issue of air pollution is growing, and the impact is more evident than ever. Carbon dioxide represents a series of problems that we face daily but have not yet been effectively solved. Currently, microalgae are known to photosynthesize and use free CO2, bicarbonate ions as a source of nutrients to grow. Microalgae are developed under appropriate environmental conditions, which will bring admirable CO2 treatment efficiency and obtain biomass for other applications. The study approach was an inexpensive and natural air purification solution by microalgae, which is designed as a tubular photobioreactor. The study was conducted by evaluating the ability of Chlorella Vulgaris to grow and absorb CO2 emissions in the newly established system with exhaust gas supplied from a mini motorcycle engine. The results showed that microalgae grew stably in the tubular photobioreactor system with a biomass concentration of 6×106 cells/ml after 42 days of the experiment. Simultaneously with the stable growth of microalgae, the CO2 emission concentration was reduced with 26.59% absorption efficiency after 11 days of the experiment. Finally, establishing the tubular photobioreactor technology system has yielded impressive initial results in cultivating stable growing microalgae combined with CO2 emission treatment.

Investigating and modelling the effect of light intensity on Rhodopseudomonas palustris growth

Photosynthetic bacteria can be useful biotechnological tools – they produce a variety of valuable products, including high purity hydrogen, and can simultaneously treat recalcitrant wastewaters. However, while photobioreactors have been designed and modelled for photosynthetic algae and cyanobacteria, there has been less work on understanding the effect of light in photosynthetic bacterial fermentations. In order to design photobioreactors, and processes using these organisms, robust models of light penetration, utilisation and conversion are needed. This article uses experimental data from a tubular photobioreactor designed to focus in on light intensity effects, to model the effect of light intensity on the growth of Rhodopseudomonas palustris, a model photosynthetic bacterium. The work demonstrates that growth is controlled by light intensity, and that this organism does experience photoinhibition above 600 W/m2, which has implications for outdoor applications. Further, the work presents a model for light penetration in circular photobioreactors, which tends to be the most common geometry. The work extends the modelling tools for these organisms, and will allow for better photobioreactor design, and the integration of modelling tools in designing processes which use photosynthetic bacteria.

Perspective Design of Algae Photobioreactor for Greenhouses—A Comparative Study

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.

Tertiary treatment of dairy industry wastewater with production of Chlorella vulgaris biomass: evaluation of effluent dilution

Secondary wastewaters from the dairy industry may cause eutrophication of water bodies when not properly treated, mainly because they contain nutrients such as phosphorus and nitrogen. Tertiary treatment using microalgae could be an adequate solution for Minas Gerais State, the largest Brazilian milk producer, contributing to the reduction of environmental impacts, as well as providing biomass for oil extraction, and obtaining active compounds and inputs (including proteins) for animal feeding. In this work, dilutions (with distilled water) of the secondary wastewater from the dairy industry were evaluated to cultivate Chlorella vulgaris in a bench-scale tubular photobioreactor. The results indicate the feasibility of using wastewater from the dairy industry, after secondary treatment, to cultivate microalgae, showing cell growth like that obtained in control cultures (Bold basal medium). The secondary wastewater without dilution (100% wastewater) provided the best condition for biomass production. The biomass obtained in wastewater showed no differences from the biomass obtained in the Bold basal medium (control) in terms of protein, lipid content, or fatty acid profile.