The Serbian mining sector has historically played an important role in the country’s development, but it now faces challenges related to sustainable practices. Serbia is among Europe’s leaders in mining-related material consumption and waste disposal, resulting in significant environmental costs. The technical efficiency of mining activities is very low, funding is limited, and the sector struggles to gain public trust due to weak regulation enforcement and a lack of transparency. Statistical analysis shows that Serbia ranks third in Europe for material footprint per capita, indicating a high dependence on resources without sufficient economic benefits. Penalties for overexploitation are low and do not act as a significant deterrent. Current revenues from mining account for only 3–7

Urban drought is a climate-related challenge that threatens environmental sustainability, public health, and socio-economic stability in urban areas. With increasing climate variability, sustainable smart city planning requires reliable forecasting methodologies to facilitate adaptive water resource management and long-term climate resilience plans. This study proposes and evaluates a time series forecasting methodology for the climatic drivers of urban drought, using standard statistical approaches-Seasonal Autoregressive Integrated Moving Average ((S)ARIMA) and Holt-Winters exponential smoothing. The methodology includes systematic preprocessing of meteorological data, univariate time series modeling, and performance evaluation using recognized accuracy metrics (RMSE, MAE, and MAPE). Air temperature, precipitation, soil moisture, and wind speed are analyzed as key climatic variables affecting urban drought dynamics. The results indicate that forecast performance varies based on the statistical characteristics of each variable: (S)ARIMA models provide superior predictive accuracy for series with significant seasonality or stochastic fluctuations, whereas the Holt-Winters method is more appropriate for variables displaying sustained downward trends, particularly soil moisture. The forecasts provide a methodological foundation for calculating drought indices and classifying severity, enhancing early warning capabilities and supporting sustainable smart city planning under increasing climate uncertainty.

The distribution characteristics of 5-hydroxymethylfurfural (5-HMF) in solution significantly affect its yield and separation/purification during its production process from glucose, but there is currently a lack of quantitative correlation with the reaction kinetics. In this paper, a systematic kinetic study was conducted on the catalytic conversion of glucose to 5-HMF using a porous carbon catalyst that possesses both Lewis and Br & oslash;nsted acid sites in a biphasic solvent system composed of NaCl-H2O and Methyl isobutyl ketone (MIBK). The addition of NaCl was found to enhance the extraction of 5-HMF into the organic phase, with the highest yield of 84.5% achieved under 10 wt% NaCl concentration. Excessive NaCl increases the solubility of 5-HMF in the aqueous phase, thereby causing a reduction in yield. Kinetic study reveals that higher NaCl concentrations suppress glucose isomerization, humins formation, and direct dehydration to 5-HMF. Excess NaCl also facilitated side reactions, such as 5-HMF rehydration. Changes in solubility equilibrium constants and partition coefficient of 5-HMF were positively correlated, and sensitivity analysis highlighted the impact of NaCl on solubility equilibrium of 5-HMF between aqueous and organic phases. By introducing the parameter of polar activation energy (Ec), the impact of NaCl on the rate constants of various reaction pathways was quantified, confirming that NaCl altered the physicochemical properties of solvent and potentially catalyzed the reaction. These findings provide valuable insight into the mechanisms and kinetics of glucose isomerization and dehydration in biphasic solvent systems, laying the foundation for the design and regulation of solvent properties to optimize these reactions.

Practically all residential and commercial gas appliances installed within the EU today were designed for operation with natural gas. A clean and efficient solution for heating and hot water generation is the combustion of hydrogen in case of a gas condensing boiler. Safe and stable combustion of hydrogen is a complex issue, and several influence parameters must be understood for the safe design of hydrogen capable gas condensing boilers. In premixed hydrogen-air combustion, there are two physical problems that should be avoided at all costs: flashback through the burner to the premixing duct and ignition delay in the combustion chamber. Well mixing of reactants is therefore, very important to achieve stable and efficient hydrogen combustion. To evaluate the influence of commercialized mixing stages (fan-venturi combination), the impact of the rotational velocity on the degree of mixing in case of a venturi-fan combination used in domestic gas condensing boilers is presented in this paper. Transient, 3-D simulations with different turbulence modelling approaches were performed to assess the degree of mixing upstream the hydrogen capable multi-hole burner. It is shown that the lower angular velocities produce better mixing. It can also be assumed that a local variation of up to 17% in the adiabatic flame speed can be expected due to the mixing processes as the consequence of the local air-fuel equivalence ratio variation.

Waste-to-energy (WtE) is a key part of modern waste management. In the European Union, approximately 500 WtE plants process more than 100 million tons of waste yearly, while globally, more than 2700 plants handle over 500 million tons. Roughly 20% of the waste processed is bottom ash (BA). However, this ash can contain heavy metals in concentrations that may render it hazardous. This paper presents a study focusing on stabilizing municipal solid waste incineration BA using simple and industrially viable treatments. The Slovenian WtE plant operator wishes to install the stabilization process; thus, the samples obtained from the plant were treated (1) with a CO2 gas flow, (2) with water spraying, and (3) with a combination of water spraying and a CO2 gas flow under laboratory conditions. Thermodynamic calculations were applied to define potential reactions during the treatment processes in the temperature range from 0 to 100 °C and to define the equilibrium composition of the treated ash with additions of CO2 and water. The standard leaching test EN 12457-4 of treated ash shows a reduction of over 40% in barium concentration and over 30% in lead concentration in leachates.

This study addresses the urgent need for decarbonization of heating sector, focusing on the potential of hydrogen-air combustion in gas condensing boilers. In the field of gas condensing boilers, groups of holes or slits can be used in perforated burner surfaces, providing a possible solution to the challenge of hydrogen air combustion. Real burners are always adjacent to an area with non-existent combustion, which can lead to a disturbed flame pattern. For this reason, a comparison between single-slit and multi-slit perforated flame holders with a significantly reduced structure temperature with a hydrogen-air premix is carried out as part of this study. Using Ansys Fluent, a 2D simulation approach is employed to analyze laminar flame stability behind a perforated flame holder. Inlet conditions consider fully premixed and homogenous distributed mixtures as well as nonhomogeneous premixed mixtures, with variations in pressure, velocity, and mixing degree. The model examines various slit-burner configurations and flashback behaviors based on an actual geometric shape used in a gas heating device. It has been found that with finite multi-slit burners, the bulk flow rates at the critical flashback point are 30-50% higher compared to infinitely symmetrical burners. A further deterioration of 32% is to be expected due to real mixture quality fluctuations and inhomogeneous inflow conditions. Finally, the findings demonstrate the model's potential for designing efficient surface-stabilized burners and lay the groundwork for future 3D simulations in the pursuit of sustainable heating solutions.

The continuous rise in the global energy demand is coupled with increasing environmental pollution and greenhouse gas emissions. The need to minimize plastic waste accumulation has driven research into alternative and renewable fuel sources. Co-processing plastic waste and biomass through hydrothermal liquefaction (HTL) has emerged as a promising approach for biofuel production by leveraging the synergistic properties of these feedstocks. This review explores the potential of plastics and biomass for biofuel production, with a focus on recent advances in HTL techniques. The paper delves into the influences of various parameters, such as temperature, pressure, feedstock ratios, and the synergistic potential of combining various plastics with different biomass feedstocks on the bio-oil yield and quality. It also highlights the environmental and economic benefits of HTL, offering insights from life cycle assessments and techno-economic analyses. The review demonstrates that HTL not only unlocks new pathways for renewable energy but also offers an innovative strategy for managing plastic waste, paving the way for a circular and sustainable bio-economy.

This article examines the impact of financial support mechanisms and geopolitical factors on the profitability of investments in solar power plants within Slovenia. The European Union’s energy policy prioritizes increases in renewable energy sources, aiming to reduce dependency on unstable and volatile fossil fuel markets. Solar power plants play a vital role in this transition. The energy policy framework also includes mechanisms and support systems to operate such facilities. This article analyzes electricity price trends over the past decade and addresses which support type—guaranteed purchase or operational support—has proven more profitable for investments in solar power plants up to 50 kW in Slovenia, considering economic and geopolitical influences on the electricity market. Although the global energy market has been affected by various significant events in recent years, it was found that the COVID-19 pandemic had minimal impact on the electricity market. In contrast, the onset of the conflict in Ukraine has contributed to rising electricity prices and has influenced the support dynamics essential for the development and sustainability of renewable energy systems. Analyses from the past decade indicate a higher return on investment in solar power plants when operational support mechanisms are chosen over guaranteed purchase support.

Introduction: During the process of waste incineration, co -incine-ration and cement production, various emissions are released into the environment containing different pollutants. The aim was to assess a possible association between exposure to pollutants emitted from co-/incinerators and cement plants and cancer in occupationally exposed persons and residents living near these plants.Methods: Inclusion criteria for the umbrella review were meta -a-nalyses and systematic literature reviews, English, period 1980- 2023. Searches were performed in 4 databases (PubMed, Scopus, Web of Science, Cochrane Reviews). The quality of documents was assessed by AMSTAR-2 (methodology) and GRADE (evidence) tools. Results: Of 7 701 documents, 14 were finally included (5 meta--analyses,9 systematic reviews). There is some low to moderate evidence of an association between soft tissue sarcomas and non-Hodgkin lymphomas in population exposed to dioxins near I. generation incinerators, but there is no evidence for next generation incinerators. To date, there is no evidence for co-incinerators. There is moderate evidence for an association between incidence of all cancers, lung, prostate, stomach and oropharyngeal cancer and exposure to chromium in occupationally exposed persons at I.-II. generation cement plants. Most of the evidence is limited due to mixed results, differences in question' technique, heterogeneity, and potential bias.Conclusions: There is limited evidence for an association between cancer and exposure to pollutants emitted from I. generation incine-rators and I.-II. generation cement plants. To evaluate the possible association between pollutant emissions from the most modern co-incinerators, it seems reasonable to plan targeted epidemiologi-cal studies and human biomonitoring studies.

Wood biomass fuels have become increasingly important in terms of achieving future sustainability targets regarding RES, especially to reduce GHG and the use of domestic energy sources, on other hand with these fuels the pulutant air emissions have to be addressed with great attention. Nowadays, air staging and flue gas recirculation are often used as a primary emission reduction measure in large scale biomass fuel fired boilers, but their combined application in small scale commercial wood pellet boilers is not so common. The implementation of this approach to the small scale burning devices can enable further development of small boilers, in order to achieve a more complete combustion and reduction of pollutant emissions, especially CO, NOx, and PM. In the presented work a comprehensive numerical and experimental study on the combustion parameters is performed, in order to determine the overall combustion properties. A commercial 32 kW small-scale hot water wood pellet boiler was modified numerically from the operating point of view. The findings of this study, like different combinations of recirculated flue gases and secondary air amount, can serve as useful guidelines for the new innovative design and optimisation of the air and recirculated flue gas injection process parameters. The scenarios of this study, where recirculated flue gas was added to the secondary air, were beneficial. Optimally, a CO reduction of 63% was achieved by adding 30% of recirculated flue gas to the secondary air stream, and a 22% reduction was achieved for the NO emissions.

Introduction: During the process of waste incineration, co-incineration and cement production, various emissions are released into the environment containing different pollutants. The aim was to assess a possible association between exposure to pollutants emitted from co-/incinerators and cement plants and cancer in occupationally exposed persons and residents living near these plants. Methods: Inclusion criteria for the umbrella review were meta-analyses and systematic literature reviews, English, period 1980– 2023. Searches were performed in 4 databases (PubMed, Scopus, Web of Science, Cochrane Reviews). The quality of documents was assessed by AMSTAR-2 (methodology) and GRADE (evidence) tools. Results: Of 7 701 documents, 14 were finally included (5 meta- -analyses, 9 systematic reviews). There is some low to moderate evidence of an association between soft tissue sarcomas and non-Hodgkin lymphomas in population exposed to dioxins near I. generation incinerators, but there is no evidence for next generation incinerators. To date, there is no evidence for co-incinerators. There is moderate evidence for an association between incidence of all cancers, lung, prostate, stomach and oropharyngeal cancer and exposure to chromium in occupationally exposed persons at I.-II. generation cement plants. Most of the evidence is limited due to mixed results, differences in questionˊ technique, heterogeneity, and potential bias. Conclusions: There is limited evidence for an association between cancer and exposure to pollutants emitted from I. generation incinerators and I.-II. generation cement plants. To evaluate the possible association between pollutant emissions from the most modern co-incinerators, it seems reasonable to plan targeted epidemiological studies and human biomonitoring studies.

Introduction: During the process of waste incineration, co-incine-ration and cement production, various emissions are released into the environment containing different pollutants. The aim was to assess a possible association between exposure to pollutants emitted from co-/incinerators and cement plants and cancer in occupatio-nally exposed persons and residents living near these plants.Methods: Inclusion criteria for the umbrella review were meta-a-nalyses and systematic literature reviews, English, period 1980- 2023. Searches were performed in 4 databases (PubMed, Scopus, Web of Science, Cochrane Reviews). The quality of documents was assessed by AMSTAR-2 (methodology) and GRADE (evidence) tools. Results: Of 7 701 documents, 14 were finally included (5 meta--analyses,9 systematic reviews). There is some low to moderate evidence of an association between soft tissue sarcomas and non-Hodgkin lymphomas in population exposed to dioxins near I. generation incinerators, but there is no evidence for next generation incinerators. To date, there is no evidence for co-incinerators. There is moderate evidence for an association between incidence of all cancers, lung, prostate, stomach and oropharyngeal cancer and exposure to chromium in occupationally exposed persons at I.-II. generation cement plants. Most of the evidence is limited due to mixed results, differences in question' technique, heterogeneity, and potential bias.Conclusions: There is limited evidence for an association between cancer and exposure to pollutants emitted from I. generation incine-rators and I.-II. generation cement plants. To evaluate the possible association between pollutant emissions from the most modern co-incinerators, it seems reasonable to plan targeted epidemiologi-cal studies and human biomonitoring studies.

This paper focuses on the numerical analysis of the combustion of the liquid fuel Extra Light Fuel Oil (ELFO) in a small combustion device. The calculation was performed by ANSYS CFX computer code for experimental optimal air-fuel ratio (λopt) and the middle power of the oil burner Weishaupt WL5/1-A (37 kW). The goal of the numerical analysis was to establish, whether the experimentally determined λopt ensured the conditions for a complete combustion in each point of the combustion chamber. The comparison of numerical results and measured values confirm the suitability of the chosen numerical model.

This work is aimed at determining the impact of Secondary Air (SA) boundary conditions on CFD combustion simulation results in a small-scale wood pellet boiler. Two sets of boundary conditions are considered: (1) The SA inflow boundary conditions (i.e., the temperature, mass flow and turbulence distribution), and (2) The SA diffuser wall boundary conditions. First, a base simulation was prepared in which the flow distribution, preheating and turbulence parameters of the SA are included in the modelling approach. From the base case results the parameters of the SA inflow and heat transfer were derived and used as boundary conditions for cases where the SA diffuser is removed from the computational domain. In a parametric study the SA inflow and wall boundary conditions are varied from those estimated (e.g., by assuming the SA has room temperature) to more realistic (i.e. identical to the calculated parameters from the base simulation). By defining a realistic SA temperature and a realistic mass flow distribution between the upper and lower SA nozzles, results were obtained with a temperature Root Mean Square Error (RMSET) of 34 ℃ and a CO emission error of 27 mg/m3. Results with a RMSET of 21 ℃ and a CO emission error of 50 mg/m3 compared to the base case, were obtained by changing the wall boundary conditions from adiabatic to average temperature. The reduced computational mesh had 23% less elements, which reduced the time to achieve convergence by 29%.

For the calculation of multiphase reactive processes in computational fluid dynamics (CFD), detailed chemical kinetics and simplified combustion models are commonly applied. An appropriate modelling approach to overcome the high computational demand of chemical kinetics is the flamelet generated manifold (FGM), which prescribe the calculation of chemical kinetics in preprocessor for the generation of the look-up databases that are used during CFD simulations with interpolation procedure. For the calculation of the chemistry kinetics in processor, combustion models are commonly applied, such as Three-zones extended coherent flame model (ECFM-3Z) that features calculation of flame speed in turbulent conditions. The primary goal of the research is to investigate and validate FGM and ECFM-3Z models on the multiphase reactive process inside a compression ignition engine for single and multiple injection strategies. Additionally, an overview of the modelling methodology and capability of FGM and ECFM-3Z models is presented, where the impact of their features is analysed on the results inside a compression ignition engine. For the numerical simulations, CFD code AVL FIRE™ was used, where the calculated results such as in-cylinder pressure, temperature, rate of heat release, and nitric oxide emissions are computed. The FGM modelling approach showed higher ignition delay compared to the ECFM-3Z model for single-injection strategy, which can be attributed to the pretabulated autoignition conditions in three zones of the ECFM-3Z model. For the multi-injection strategy, such an ignition delay difference between FGM and ECFM-3Z is not observed since the small amount of injected fuel in pilot injections tends to have quicker ignition, which then creates better conditions for combustion of the more significant amount of injected fuel in the main injection. The experimental nitric oxide emission trend is achieved with both combustion modelling approaches, where the CFD calculation time for cases with FGM is reduced approximately by half. In comparison against the experimental values, both FGM and ECFM-3Z combustion modelling approaches showed the capability of predicting the influence of fuel injection strategy on the combustion process in passenger car compression ignition engines.

An effective air staging strategy is of great importance for achieving low emissions and sensible heat losses through flue gas extraction. In cases where a commercially available system needs to be optimised, often the only viable measure is the modification of process parameters. In this work, the aim is to (1) Discover a combination of the most suitable process parameters based on a multi-criteria decision-making method and (2) To unveil relevant correlations between the two process parameters under study (PA/SA ratio and excess air), emissions and combustion temperatures. A modified commercial small-scale hot water wood pellet boiler was installed into a laboratory heating system. Nine different cases have been addressed within a parametric study, differing in the PA/SA ratio and overall excess air. Emissions, temperatures inside the combustion chamber and the flow rate of air entering the combustion chamber were measured. A low PA/SA ratio of 0.53 (54.7% reduction from factory settings), combined with a low O2 concentration in the flue gases of 5.26% (39.8% reduction from factory settings), and the elimination of infiltration air resulted in a simultaneous reduction of NOx and CO emissions by 14.4% and 93.9% respectively and a flue gas sensible heat loss reduction of 31.6%.

Emissions of nitrogen oxides from the aviation sector, contrary to the land-based sources, have doubled compared to 1990. Aircraft unique location in the upper atmosphere and daily growth of air-based traffic require particular attention to the effects of these emissions. One way to cope with this problem is to develop and design more efficient combustion systems. In this research, the numerical modelling of combustion process inside a jet engine combustion chamber is presented. The investigated chamber is a theoretical can type chamber mounted with a double stage radial swirler. The advanced k-zeta-f turbulence model was utilised to model the turbulent behaviour, while the spray process was described by the Euler Lagrangian spray modelling approach. Two different modelling approaches for describing the combustion process were employed: reduced chemical mechanism and the 3-zone extended coherent flame (ECFM-3Z) combustion model. Considering the analysis of relevant physical quantities and taking into account the reduction of computational costs while using the ECFM-3Z combustion model, it was employed for analysis of the influence of spray and emission processes by varying number and positioning of fuel introduction nozzle holes. Increase in the number of nozzle holes and their correct positioning can result in emission reduction up to 60%. Such behaviour could be addressed to the specific spray cloud formation and smaller high-temperature regions. Results showed that the presented model can be used as a modern design tool in the early stage of the combustion chamber development.Y

Mass transfer between the phases is a cornerstone of many technological processes and presents a topic whose understanding and modelling is of high importance. For instance, absorption of gases in liquid droplets is an underlying phenomenon for the desulfurization of flue gases in wet scrubbers. Wet scrubbing is an efficient cleaning method where the liquid is sprayed in a stream of rising gases, removing pollutants due to the concentration difference between the gas phase and droplets. A model for absorption in water droplets has been developed to describe the complex physical and chemical interactions during the exposure to flue gases. The main factors affecting the absorption are the mass transfer of pollutants through the gas–droplet interface and the aqueous phase chemistry in a droplet. The mass transfer coefficient, which has been modeled with several approaches, is the most significant parameter regulating the absorption dynamic into the droplet, while the in-droplet chemistry controls the maximum quantity of dissolved pollutants. Dissociation of sulfur dioxide and the chemical reactions in seawater have been described by the equilibrium reactions. Afterward, the influence of the mass transfer coefficient has been investigated, and the model has been validated against the literature data on a single droplet scale. Obtained results are comparable with the experimental measurements and indicate the applicability of the model for the design and development of industrial scrubbers.

The common combustion disturbances in the fuel bed in a grate-fired boiler pose a great challenge to accurate modelling of the fuel bed conversion. Therefore, it is difficult to describe the lengthwise profiles of the combustibles leaving the fuel bed into the freeboard accurately. This paper investigates how different fuel bed models or grate inlet profiles will affect the Computational Fluid Dynamics simulation of combustion in the freeboard in industrial grate boilers. Two grate inlet conditions, which are very different in the profiles along the grate but yield the same total mass, momentum, species and energy fluxes into the freeboard, are used in the freeboard simulation of a 13 MWth grate boiler, respectively. The key findings from the comparison between the simulation results and measurement data are as follows. Firstly, the fuel bed model or grate inlet condition accounting for the realistic lengthwise biomass conversion pattern can be used reliably for the simulation of a grate boiler and simulation-based boiler optimisation. Secondly, the impacts of different fuel bed models or different profiles of the grate inlet conditions are virtually restricted only to the vicinity of the fuel bed or in the primary combustion chamber. After the secondary combustion chamber in which up-flowing gas is mixed well with the secondary and tertiary air jets, the simulation results are close to each other. For more general and reliable applications, a comprehensive bed model resolving the mixing, reactions, heat and mass transfer in the fuel bed, is needed and under development.

Optimal geometric and process parameters related to air staging, which ultimately lead to lower pollutant formation and a higher thermal efficiency, can be found by utilisation of the CFD simulation method. Simplified and computationally efficient methods for the simulation of complex phenomena which occur in a biomass boiler can, therefore, be of great use, provided they offer reliable and reasonably accurate predictions. A previously developed and validated Computational Fluid Dynamics combustion simulation methodology for largescale waste to energy grate-fired boilers is modified and implemented for the case of a commercial 32 kW wood pellet hot water boiler. An experimental investigation is performed in order to determine process parameters used in the fuel conversion modelling, case setup and, finally, to enable the validation of the numerical modelling approach. The solid fuel conversion is modelled by a coupled empirical 1D bed model which predicts the composition of the combustible gas mixture released from the fuel bed into the freeboard. Compared to the originally proposed fuel bed conversion model, the modified model includes partial char and volatile oxidation, and relies on gas temperatures measured above the fuel bed. Using the modified fuel bed conversion model, several cases were simulated in order to find the most appropriate parameters of the combined finite rate - eddy dissipation combustion model. Results show that by implementing the modified fuel bed conversion model that relies on measurements, reasonably accurate predictions can be achieved of the gas temperature in the combustion chamber and CO concentration at the flue gas outlet.