The increasing concentration of anthropogenic CO₂ in the atmosphere is causing a global environmental crisis, forcing significant reductions in emissions. Among the existing CO₂ capture technologies, microalgae-guided sequestration is seen as one of the more promising and sustainable solutions. The present review article compares CO₂ emissions in the EU with other global economies, and outlines EU’s climate policy together with current and proposed EU climate regulations. Furthermore, it summarizes the current state of knowledge on controlled microalgal cultures, indicates the importance of CO₂ phycoremediation methods, and assesses the importance of microalgae-based systems for long-term storage and utilization of CO₂. It also outlines how far microalgae technologies within the EU have developed on the quantitative and technological levels, together with prospects for future development. The literature overview has shown that large-scale take-up of technological solutions for the production and use of microalgal biomass is hampered by economic, technological, and legal barriers. Unsuitable climate conditions are an additional impediment, forcing operators to implement technologies that maintain appropriate temperature and lighting conditions in photobioreactors, considerably driving up the associated investment and operational costs.

Microalgal biomass can be used to derive many different types of biofuels. In order to widely commercialize this technology, its limitations and weaknesses must be eliminated. Many technical and economic issues also need to be clarified and unknowns answered. Microalgae-based technologies have been shown to be versatile, efficient and suitable for practical and commercial use. However, the current technological readiness level (TRL) of most microalgae-based bioenergy production systems precludes their quick and widespread implementation. Their development is limited by a combination of factors that must be precisely identified, after which their negative impact on scale-up prospects can be eliminated or minimized. The present study identifies the main barriers to the development of industrial microalgae-production and microalgae-to-biofuel systems. In addition, it proposes measures and efforts necessary to achieve a higher TRL, which will provide investors with sought-after performance and cost-efficiency data for the given project. The main barriers to the development of microalgae cultivation and processing systems have been identified to include: the complex nature of the cultivation process with multiple variables involved; lack of sufficient data from pilot-scale and near-full-scale plants, which often precludes reliable life cycle assessment (LCA); and insufficient legal assistance, advisory assistance, subsidies and funding for innovative projects. Potential ways of improving performance and competitiveness of microalgae-based systems include: process optimization techniques, genetic engineering, yield improvement through advanced process control and monitoring, use of waste as feedstock and dedicated support programs. The presented summary of the current stage of microalgal biofuel production technology development indicates the directions for further research and implementation work, which are necessary for the final verification of the application potential of these solutions.

The aim of the study was to determine the use of digestate from anaerobic digestion of dairy wastewater as a culture medium for microalgae to obtain bio-oil. The experiments were conducted at a small scale in a closed raceway pond. The efficiency of the microalgae biomass production, the digestate treatment efficiency as well as the content and properties of the bio-oil obtained from the microalgal cells were analyzed. The produced biomass concentration was about 3000 ± 10.5 mg dry biomass/L, with an average growth rate of 160 ± 6.6 mg_dm/L·d. The efficiency of organic compound and nutrient removal was above 90%. The bio-oil content in the biomass was about 20%. Based on the results of the study, a concept for technical-scale technology was developed.

The article presents a concept of a lunar base that would take advantage of the natural shape of an egg. Several versions of egg-shaped habitat structures characterized by different sizes are presented. Possible locations of habitats both on lunar surface and in craters were discussed. Advantages and disadvantages of particular locations were also pointed out. The proposed in the paper concept of an egg-shaped structure is characterised by a spatial character based on Voronoi diagram and would be implemented using a 3D-printed method. The presented 3D-printed structure was designed to be light and suitable to be covered by lunar soil. As a necessity in the developed concept, in situ resources utilization was addressed in order to generate products using local sources to reduce the number of materials that would be required to be transported from Earth. At the end of the paper, future areas of research and tests are highlighted.

Algae biomass is perceived as a prospective source of many types of biofuels, including biogas and biomethane produced in the anaerobic digestion process, ethanol from alcoholic fermentation, biodiesel synthesized from lipid reserve substances, and biohydrogen generated in photobiological transformations. Environmental and economic analyses as well as technological considerations indicate that methane fermentation integrated with bio-oil recovery is one of the most justified directions of energy use of microalgae biomass for energy purposes. A promising direction in the development of bioenergy systems based on the use of microalgae is their integration with waste and pollution neutralization technologies. The use of wastewater, another liquid waste, or flue gases can reduce the costs of biofuel production while having a measurable environmental effect.

Microalgae are considered to be very promising feedstocks for biomethane production. It has been shown that the structure of microalgal cell walls can be highly detrimental to the anaerobic digestibility of biomass. Therefore, there is a real need to seek ways to eliminate this problem. The aim of the present study was to assess the effect of ultrasonic disintegration of Scenedesmus sp. and Pinnularia sp. microalgal biomass on the performance and energy efficiency of anaerobic digestion. The pretreatment was successful in significantly increasing dissolved COD and TOC in the system. The highest CH₄ yields were noted for Scenedesmus sp. sonicated for 150 s and 200 s, which produced 309 ± 13 cm³/gVS and 313 ± 15 cm³/gVS, respectively. The 50 s group performed the best in terms of net energy efficiency at 1.909 ± 0.20 Wh/gVS. Considerably poorer performance was noted for Pinnularia sp., with biomass yields and net energy gains peaking at CH₄ 250 ± 21 cm³/gVS and 0.943 ± 0.22 Wh/gVS, respectively. Notably, the latter value was inferior to even the non-pretreated biomass (which generated 1.394 ± 0.19 Wh/gVS).