Regardless of the increasingly intensive application of vehicles with electric drives, internal combustion engines are still dominant as power units of mobile systems in various sectors of the economy. In order to reduce the emission of exhaust gases and satisfy legal regulations, as a temporary solution, hybrid drives with optimized internal combustion engines and their associated systems are increasingly being used. Application of the variable compression ratio and diesel fuel injection timing, as well as the tribological optimization of parts, contribute to the reduction in fuel consumption, partly due to the reduction in mechanical losses, which, according to test results, also results in the reduction in emissions. This manuscript presents the results of diesel engine testing on a test bench in laboratory conditions at different operating modes (compression ratio, fuel injection timing, engine speed, and load), which were processed using a zero-dimensional model of the combustion process. The test results should contribute to the optimization of the combustion process from the aspect of minimal particulate matter emission. As a special contribution, the results of tribological tests of materials for strengthening the sliding surface of the aluminum alloy piston and cylinder of the internal combustion engine and air compressors, which were obtained using a tribometer, are presented. In this way, tribological optimization should also contribute to the reduction in particulate matter emissions due to the reduction in fuel consumption, and thus emissions due to the reduction in friction, as well as the recorded reduction in the wear of materials that are in sliding contact. In this way, it contributes to the reduction in harmful gases in the air.

Waste collection and transport can generate up to 70% of the total costs of the system. Separated collection of recyclables implies additional costs for which the sale of recycled waste often does not compensate, but there is increased pressure to reach the long-term recycling objectives set by law. The proper estimation and monitoring of waste collection costs are essential to define the most cost-effective waste collection system. The aim of this study is to propose and implement a management tool to determine waste collection costs for different waste collection schemes. Based on input data, such as waste quantity and composition, the number of waste bins, the location of collection points, the type of collection vehicle, crew, collection route, etc., the developed tool can calculate the time and costs of waste collection (per vehicle, collection point or tonne of collected waste). This tool uses Excel spreadsheets and it was tested on a district in the central area of the city of Kragujevac to calculate the costs of waste collection for two scenarios: Collecting all waste as mixed waste, and collecting separately recyclables and residual waste. The developed tool can be useful for municipal solid waste management companies, since it allows benchmarking and variance analysis.

Collection and transportation within the system of solid waste management may account more than 60% of the overall budget, most of which is for fuel costs. Furthermore, municipal vehicles have great environmental impact through exhaust gases emissions. The aim of this research was to estimate the potential for reduction of fuel consumption and thus the emission of CO2 through the communal vehicles route optimization. General methodology for route optimization is also presented. For the area under study, detailed field experimental research in the City of Kragujevac was conducted. Using GIS and GPS technology, whole municipally infrastructure for waste collection was scanned and all paths of communal tracks was recorded and allocated in developed database. Based on experimental and numerical results, one typical municipal vehicle route was analyzed by using ArcGis software. The obtained result indicates 2700 km of possible savings per year concerning one communal vehicle. In addition, the most fuel-economical route was extracted and compared with the original route, and with the routes extracted from criterions concerning the traffic time and shortest distance. According to available information for the City of Kragujevac and the results from this study, it was estimated that the total savings could be 20% in costs and the associated emissions.

Multi-criteria decision making (MCDM) is a relatively new tool for decision makers who deal with numerous and often contradictory factors during their decision making process. This paper presents a procedure to choose the optimal municipal solid waste (MSW) management system for the area of the city of Kragujevac (Republic of Serbia) based on the MCDM method. Two methods of multiple attribute decision making, i.e. SAW (simple additive weighting method) and TOPSIS (technique for order preference by similarity to ideal solution), respectively, were used to compare the proposed waste management strategies (WMS). Each of the created strategies was simulated using the software package IWM2. Total values for eight chosen parameters were calculated for all the strategies. Contribution of each of the six waste treatment options was valorized. The SAW analysis was used to obtain the sum characteristics for all the waste management treatment strategies and they were ranked accordingly. The TOPSIS method was used to calculate the relative closeness factors to the ideal solution for all the alternatives. Then, the proposed strategies were ranked in form of tables and diagrams obtained based on both MCDM methods. As shown in this paper, the results were in good agreement, which additionally confirmed and facilitated the choice of the optimal MSW management strategy.

This paper concerns the development of a methodology aimed at determining the optimal number of waste bins as well optimizing the location of collection points. The methodology was based on a geographic information system, which handled different sets of information, such as street directions, spatial location of objects and number of inhabitants, location of waste bins, and radius of their coverage. The study was conducted in a district in the central area of the city of Kragujevac. Due to a lack of information about the existing situation, all necessary data was collected by fieldwork and by using GPS equipment. By using the developed methodology, the results indicated a reduction of 24% in the number of collection points and 33.5% in the number of waste bins, without reducing the quality of the provided services. It has led to cost and time savings for waste collection and environmental benefits. All users of the services were covered within a 75-m radius, and the usage of bins is more efficient. According to the reduction in the number of waste bins, a total amount of €26 000 may be achieved. In addition, the time for waste collection was reduced, resulting in a €1700 saving per year in fuel costs, as well as 4.5 tons of emitted CO₂ into the atmosphere.