Hydrogen-based technologies are among the most promising solutions to fulfill the zero-emission scenario and ensure the energy independence of many countries. Hydrogen is considered a green energy carrier, which can be utilized in the energy, transport, and chemical sectors. However, efficient and safe large-scale hydrogen storage is still challenging. The most frequently used hydrogen storage solutions in industry, i.e., compression and liquefaction, are highly energy-consuming. Underground hydrogen storage is considered the most economical and safe option for large-scale utilization at various time scales. Among underground geological formations, salt caverns are the most promising for hydrogen storage, due to their suitable physicochemical and mechanical properties that ensure safe and efficient storage even at high pressures. In this paper, recent advances in underground storage with a particular emphasis on salt cavern utilization in Europe are presented. The initial experience in hydrogen storage in underground reservoirs was discussed, and the potential for worldwide commercialization of this technology was analyzed. In Poland, salt deposits from the north-west and central regions (e.g., Rogóźno, Damasławek, Łeba) are considered possible formations for hydrogen storage. The Gubin area is also promising, where 25 salt caverns with a total capacity of 1600 million Nm³ can be constructed.

Series of WO₃/TiO₂nanocomposites were obtained by hydrothermal method followed by calcination in the temperature range from 400°C to 900°C. The characteristics of photocatalysts by X-ray diffractometry (XRD), scanning electron microscope (SEM), and diffuse reflectance spectroscopy (DRS) showed that increasing the calcination temperature from 400 to 900°C resulted in change of photocatalytic activity under UV-Vis light. Moreover, the amount of WO₃crystalline phase and amorphous phase in WO₃/TiO₂aggregates, as revealed by XRD analysis, was dependent on the calcination temperature. The WO₃/TiO₂samples with 8 mol% load of WO₃in respect to TiO₂calcinated at 500 and 800°C possess the highest photocatalytic activity in reaction of phenol degradation, which is about 1.2 and 1.5 times that with calcination at 400°C. The increase in calcination temperature above 400°C resulted in increase of WO₃crystallinity and reduction of the amount of amorphous phase in the nanocomposite structure. Moreover, the annealing of nanocomposites above 700°C decreases the value of optical band gap energies of obtained WO₃/TiO₂nanomaterials.

This paper examines the influence of biomass directed to anaerobic digestion on the quality of digestate, specifically focusing on the presence of undesirable substances, such as plastics, including biodegradable ones. It analyses the susceptibility of selected bioplastics to degradation and addresses the problem of reliable identification of microplastics in both feedstock—directed to anaerobic digestion—and produced digestate. The review indicates the advantages of using kitchen waste as a feedstock for anaerobic digestion. The constant availability of kitchen waste as a raw material, its homogeneous composition, and the fact that it is not subjected to seasonal fluctuations, facilitates its management in the anaerobic digestion process. However, to ensure the desired quality of a digestate, it is important to carry the selective collection of waste at the source. The review refers to the issues of quality, materials, and regulations, and it may be useful for readers entering the subject of a material loop, as well as those already involved in the subject, including local government units. Anaerobic digestion of kitchen waste is an important part of a renewable economy, providing year-round constantly available substrate for energy production that is not seasonally dependent.