The importance of the cultivation of algae in various fields, including in the field of energy, is very high. Algae as a reserve type of renewable fuel are considered thanks to the rapid growth of algae and the ability of algae to store lipids.
It was much devoted to the capture of carbon dioxide. Now, scientists from all over the world are actively offering a completely different approach—not only to capture CO2 but also to immediately use it for energy reproduction. This approach to solving the greenhouse problem is very relevant because of the high cost and complexity of technologies for capturing CO2 emissions, the same CO2 storage facilities also need to be maintained, and they uselessly occupy a considerable area. Thus, the reproduction of biofuels together with the capture of carbon dioxide is an elegant and high-potential solution to the problem of global warming. CO2 accounts for 77% of all greenhouse gases. Thus, despite the content of nitrogen oxides, hydrocarbons, and sulfur dioxide in greenhouse gases, it is necessary to capture CO2. Therefore, if you defeat uncontrolled mass emissions of CO2, you can also defeat a whole host of environmental problems, such as the drying up of natural freshwater, disruption of food chains, and the extinction of entire animal species, and so on.
Carbon dioxide is a stable and inert compound, so increasing the value of biofixed carbon dioxide is a major challenge. It is a detailed and in-depth one about this topic [9]. It was considered a range of technologies to increase the value of carbon dioxide, such as mineralization of carbon dioxide as an inorganic carbonate or supercritical carbon dioxide as a solvent. It was [10] is to analyze the impact of carbon dioxide on the environment and to justify the use of CO2 the reproduction of biofuels. By their nature, greenhouse gases in some quantities are vital for organic existence on Earth, as they absorb the thermal radiation of the Earth and reflect it. That is, greenhouse gases help to maintain a normal temperature for all living things on the planet. However, excessive amounts of greenhouse gases are already having a disastrous effect on ourthe organic world, and their resulting amount must be reduced and constantly monitored. In addition to maintaining the number of greenhouse gases at an acceptable level, it is necessary to reduce the consumption of fossil irreplaceable natural resources, as this is also an urgent need for the survival of future generations of the planet. For some researchers [10][11][12], it was noted that the combustion of traditional fuel brings 56% of all CO22emissions in the world. Carbon dioxide is captured directly from the carbon source and transported to storage. Storage facilities must ensure safe storage of CO2 for hundreds of thousands of years, without dumping it into the atmosphere. Speaking about this method in more detail, the stages of CO2 capture should be distinguished: separation of the gas phase, dissolution into liquid, absorption into a solid. When dissolved in a liquid, carbon dioxide is absorbed by a special liquid solvent, then this medium is heated until CO2 is released and the cycle is repeated. Absorption into a solid is an adsorption process performed by decreasing pressure and increasing temperature. Capturing CO2 before direct fuel combustion is possible only when using a thermochemical gasification process. According to Rahman, Farahiyah Abdul, et al. [10], CO2 capture before combustion is more economical than after combustion. One of the problems of CO2 biofixation and safekeeping technology is also an insufficiently known base from the political side. It is not enough on the exact costs of capturing and general rules for storing CO22. Countries need to cooperate on these issues, and this is not happening properly at the moment. Therefore, the method of long-term storage of CO2 cannot be preferable and it must be useful to utilize it in biofuels. It was less known on the simultaneous capture of CO2 and the production of microalgae at present, although according to the authors, this is a promising area of modern science. Microalgae can actively absorb CO22from the exhaust gases for photosynthesis and self-reproduction. In Alami, Abdul Hai, et al. [13] presented a deep understanding on the use of algae as traps for CO2 from flue gases. The quality of such systems depends on many factors considered by the authors. In general, algae are resistant to external influences, so pure carbon dioxide for their high-quality cultivation may not be used. This means that flue gases are perfect as a source of carbon dioxide for micro and macroalgae. Under the right growing conditions, the degree of carbon dioxide capture by algae can reach 99%, and the slow supply of exhaust gases causes an increase in the growth rate of cultured organisms. Of the flue gases, only CO2 is necessary for the growth of algae; however, it is necessary to take into account that, in addition to carbon dioxide, flue gases contain at least 140 different chemical compounds [11]. Bhola, V., et al. [14] claim that microalgae can biofix carbon dioxide 50 times more than plants. Algae can generate an average of about 280 tons of already dry biomass per 1 ha per year, provided that solar energy is available 9% of the time. These microalgae can absorb about 513 tons of carbon dioxide during their growth. Given the composition of the flue gases, namely the carbon dioxide content of 3–30%, the most important task is the correct selection of algae that can withstand and absorb such high concentrations of2CO2. resistant algae, then it is necessary to constantly maintain the optimal pH level. Under these conditions, the crop will be able to multiply and effectively deal with CO2 emissions by absorbing them. Moreover, when choosing algae, you should give preference to species that are resistant to NOX and SOX, because they form acids when interacting with water, which is destructive to most crops. It is worth noting that, when cultivating algae in natural conditions (pond and sunlight), a pond with a volume of 4000m3can absorb about 2200 tons of CO2 /year.