Composting is the natural, exothermic process where the huge amount of heat that is created is an issue of organic matter decomposition. However, too high temperature can reduce the microbial activity during the thermophilic composting phase. The aim of this study was to analyze the effect of heat excess removal from composted materials on the process dynamic. The experiment was performed in two parallel bioreactors. One of them was equipped with a heat removal system from the bed of the composted material. Three experiments were carried out with mixtures of different proportions: biological waste, wheat straw, and spent coffee grounds. The content of each option was determined based on a previous study of substrates to maintain the C/N ratio for the right composting process, provide adequate porosity composted material, and enable a proper degree of aeration. The study showed the possibility of receiving part of the heat from the bed of composted material during the thermophilic phase of the process without harm both to the course of composting and the quality of the final product. This shows that at a real scale, it can be possible to recover an important amount of heat from composted materials as a low-temperature heat source.

Due to the ever-increasing demand for clean energy derived from renewable sources, new options for obtaining it are being sought. The energy of water streams, compared to wind energy or solar energy, has the advantage that it can be supplied continuously. A relatively new solution used in hydro power plants is the AST (Archimedes screw turbine), which perfectly complements the possibilities of energy use of water courses. This solution can be used at lower heads and lower flows than is the case with power plants using Kaplan, Francis, or similar turbines. An AST power plant is cheaper to build and operate and has less negative environmental impact than traditional solutions. Accordingly, research is being conducted to improve the efficiency of the AST in terms of its environmental impact, efficiency, length, angle of inclination, and others. These studies revealed sources of losses, optimal operating conditions, and turbine design methods. They also showed the much lower environmental impact of Archimedes screw turbines compared to the others. In the course of compiling this review, the authors noticed some differences regarding the description proposed by different authors of the characteristic geometric dimensions of turbines and other quantities.

Due to the ever-increasing demand for clean energy derived from renewable sources, new options for obtaining it are being sought. The energy of water streams, compared to wind energy or solar energy, has the advantage that it can be supplied continuously. A relatively new solution used in hydropower is the AST (Archimedes Screw Turbine), which perfectly complements the possibilities of energy use of water courses. This solution can be used at lower heads and lower flows than is the case with power plants using Kaplan, Francis or similar turbines. An AST power plant is cheaper to build, operate, and has less negative environmental impact than traditional solutions. Accordingly, research is being conducted to improve the efficiency of the AST in terms of its environmental impact, efficiency, length, angle of inclination and others. These studies revealed sources of losses, optimal operating conditions, and turbine design methods. They also showed a much lower environmental impact of Archimedes turbines compared to the others. In the course of compiling this review, the authors noticed some differences regarding the description by different authors of the characteristic geometric dimensions of turbines and other quantities.