The continued expansion of cities in economic, population and geographical terms leads to significant environmental and infrastructural pressures, including the need for efficient municipal solid waste (MSW) management. This research focuses on the characterization of MSW generated in the city of Skopje and the investigation of its thermo-physical properties and energy utilization potential. The analyses cover physical and chemical properties, including density, moisture content, volatile matter, ash, and higher heating value, using adequate testing methods. The results indicate that MSW has a relatively high gross calorific value, surpassing typical MSW ranges comparable to those of solid fossil fuels. With approximately 79.42% volatile matter and a low ash content of 7.76%, the considered MSW demonstrates excellent combustibility. Chemical analysis reveals high carbon (53.12%) and hydrogen (7.69%) levels, supporting high energy value, while low nitrogen (0.84%) and sulfur (0.26%) levels ensure minimal NOx and SOx emissions. These characteristics position MSW as a suitable feedstock for energy production in incineration facilities. However, the heterogeneous composition of MSW presents challenges to process stability, necessitating prior waste preparation. The research concludes that harnessing waste energy potential could contribute to sustainability, reduce reliance on fossil fuels, and improve the environmental conditions in large urban areas.

The growing demand for sustainable and circular construction materials has increased interest in reusing by-products from municipal solid waste incineration. Due to the variability in the chemical composition of bottom ash (BA) between different plants, sampling seasons, and particle sizes, an individualized approach depending on its origin is essential. This study examines the potential of BA as a binding material in composite structures. Composites were prepared from BA fractions of different granulometries, including ground and thermally treated material. Compressive strength tests and structural analyses of density, porosity, and water permeability were performed to evaluate the influence of particle size and heat treatment on binding activity. The results show that smaller particle sizes significantly improved compressive strength, while the highest strength was obtained for samples calcined at 1000 °C, with an average increase of 84% compared to untreated material. Thermal treatment enhanced binding activity through the mobilization of hydration-active compounds bound in non-reactive mineral phases formed during water cooling and also increased water permeability due to the breakdown of porous structures. These findings confirm the potential of BA as a secondary binder in construction materials; however, further research is needed to improve its reactivity and mechanical performance.

The study focuses on the analysis of pore structure and the determination of CO2 adsorption properties of different rank coals originating from the Upper Silesian Coal Basin. Measurements were performed using a low-pressure volumetric apparatus ASAP 2020, Micromeritics, for sample porosity characterisation, and a gravimetric analyser IGA-001, Hiden Isochema, for gas adsorption measurements in the range of elevated adsorbate pressures. CO2 adsorption isotherms were determined in the CO2 pressure and temperature, 0-100 kPa at 0°C and 0-1200 kPa at 30°C, respectively. Coal investigations were complemented by microscopic, technical and densimetric analyses. CO2 adsorption studies showed the absence of a universal model that adequately describes both low-pressure and elevated-pressure processes. Adoption of the Langmuir-Freundlich model proved appropriate for most coals (5 of 6), while for one sample (CR2), a better fit was obtained with the Freundlich model. The analyses confirmed differences in the pore structure and CO₂ adsorption properties of coals with different rank. With increasing degree of coalification, an increase in specific surface area and micropore volume was observed. All coals exhibited narrow micropores with sizes <0.7 nm (ultramicropores). Analysis of pore size distributions by the DFT method showed that the porous structure of the coals was crucial for assessing CO2 adsorption performance and the transport properties of coal. The diffusion rate was not limited by the high rank of coal but rather by the structural heterogeneity of the pores, which could be detected by analysing the pore size distribution.