The use of organic residues and waste for production of biogas as an energy source is a viable option for waste management and reduction of greenhouse gas emissions. However, before any eventual utilization of biogas, hydrogen sulfide (H 2 S) and carbon dioxide (CO 2 ) must be removed since those contaminants are highly undesirable in combustion systems. This work deals with the construction and examination of a laboratoryscale, low-cost test stand for quick evaluation of the existing and new methods for H 2 S and CO 2 removal from biogas. The test stand consists of two sections: one based on absorption in liquid phase (barbotage process) and the other adsorption in a bed of solid reagent. Seven different reagents of various concentrations were used in the experiment: sodium hydroxide (NaOH), ethylene glycol (EG), ethanoloamine (EA), diethanoloamine (DEA), and distilled water (H 2 O) in the barbotage section of the test stand, and bog iron ore (BIO) and activated carbon (AC) in the adsorption column. In the absorption tests, treating biogas with 1M NaOH solution and 100% EA resulted in complete removal of H 2 S and CO 2 . For 100% DEA, high H 2 S and moderate CO 2 absorption efficiency were achieved. EG and H 2 O allowed the removal of H 2 S only to a very limited extent. Both reagents used in the tests with adsorption in a bed, BIO and AC, were able to eliminate H 2 S from biogas, but practically did not change the concentration of CO 2 .

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Among the factors influencing tourist trail network development are political issues, including the presence of state borders, the possibility of crossing them and the accessibility of border zones. In the article, it was decided to look at changes in the offer of tourist trails (hiking and cycling) along the entire border of the Czech Republic after the extension of the Schengen area (within this area, crossing the border is possible anywhere, and not only at official border crossings). It should be emphasized here that the borders of the Czech Republic over most of their length run through mountainous areas and, apart from political factors, natural features should have a major impact on the development of tourist routes. In order to determine the coherence of the current network of trails on both sides of the Czech Republic state border, modern tourist maps have been analyzed, determining the number of places where it is possible to cross the state border with the help of a marked tourist trail. Based on that, two indicators were introduced to determine the degree of openness with all neighboring countries as regards the opportunity to cross on a tourist trail. Changes in the historical situation, a comparison of the accessibility of the border area before entering the Schengen area and 2019, were analyzed for two study areas using archival maps. Over a decade after the extension of the Schengen area, the number of places where tourist trails of neighboring countries approach the border has clearly increased. Crossing is more often made possible using hiking trails than cycling routes (trails of the first type cross the border every 7.91 km, while the latter every 13.3 km), but considering the speed of movement, it can be assessed that the openness for cyclists is higher than for hikers. Moreover, in many places there is still significant potential for further integration of tourist trail networks as trails created in one country often do not have a continuation on the other side of the border.

In recent years, a considerable development of the network of hiking trails has taken place in selected parts of the Sudetes. This has occurred both in areas of hitherto poorly developed tourist infrastructure (for example the Orlickie Foothills) as well as in traditional tourist regions with a quite good base (for example the Sowie Mountains). It was decided to analyse more precisely the changes which occurred in 2005-2017 in selected parts of the Middle Sudetes. For this purpose, changes in the density and connectivity of the networks of hiking trails were assessed using elements of the graph theory and, drawn from it, indices used in the topological analysis of spatial structure. A comparative analysis of maps was the basis for these works. Important factors deciding about the validity of marking new hiking trails are: their role in the network of trails and their tourist attractiveness. Those were evaluated using field works and an analysis of maps and tourist (sightseeing) literature. An additional aim was to examine ways of tracing new trails and changing routes of those already existing, taking into account the guidelines for hiking trails presented in literature. Marking new trails has undoubtedly enabled the development of networks, but not necessarily resulted in their higher connectivity (new sections of trails resulted in a higher number of nodes). However, new tourist values have been made accessible (especially scenic and cultural ones) and planning hikes has become simpler, which is particularly important in the vicinity of spas. New hiking trails and changes of routes of those existing earlier must be assessed positively in terms of the relation between natural and artificial (hard) surfaces.