Biogas obtained by anaerobic digestion process from various organic fractions of waste is increasingly used as a renewable energy sources for the generation of electricity and heat. The quantity of biogas produced by anaerobic digestion depends on many factors: types and characteristics of organic waste, elemental composition of waste, C/N ratio, pH value, inhibitors, retention time, content of nutrients, etc. In addition to the selection of parameters that influence the process of anaerobic digestion, biogas yield can also be influenced by choosing the optimal combination and ratio of organic fractions of waste. In this paper, an analysis of the influential parameters in the process of anaerobic digestion was performed on biogas yields and an overview of the essential characteristics of waste (elementary composition, C/N ratio, lignin content, etc.) for different fractions of organic waste (organic municipal waste, various types of waste of animal origin, as well as agricultural waste). In order to choose the optimal mixing ratio of different fractions of organic waste for maximum biogas yield, a mathematical model has been developed using the multi-criteria optimization method. The boundary conditions set for the multi-criteria optimization was the C/N ratio in the range of 20 to 30 and the minimum content of the lignin in the substrate. The application of the developed model was carried out on the case study of the city of Nis, and the optimal mix of different types of organic waste was determined, as well as the optimal amount of each waste fraction and biogas yield.
The impact of information and communication technologies (ICT) is increasing in teaching, and practice shows that there is a need for individual work in the educational process. This paper gives an analysis of the attitudes of teachers about the use of ICT as a means for individualizing teaching in regular and special primary schools. The results showed that teachers’ attitudes toward ICT as a way of individualization are positive, but they are more pronounced among teachers from special primary schools. Individualized teaching encourages students to progress, but it can negatively affect students’ social behavior. Teachers must have a good knowledge of working with ICT, so seminars on the use of ICT should be organized. ICT affect the education of all students. Teachers from both regular and special primary schools think agree that ICTs are just for fun and that they have no place in the classroom, but at home.
Integration of nature, live, organic materials, in the design of built areas and building structure is an architectural response to environmental problems of dense urban areas. At the site where green space is limited, greening the building envelope is the solution for the issues such as heat waves, flooding, and noise and air pollution. The benefits could be predicted only using accurate simulation model of this technology. The energy balance of green living roof was researched through models developed over the years by various authors. Most models have been developed and validated with data from extensive roofs and more than 50% of the models were validated using data from warm temperate climatic zones. Ability to determine the impact of green living roofs at different stages of their architectural design process is of most importance if the incorporation this technology is planned due to the impact on building and urban level.
The organic fraction of municipal waste (MW) is a huge resource of nutrients and energy, primarily because of the high content of carbon as well as potassium and phosphorus. On the other hand, having in mind the problems that cities are faced with, such as energy supply, transportation, environmental pollution and many others, waste management has to be considered as an integral part of city management. Circular economy is a new concept of thinking which implies that all streams of a system should be considered as a possible resource, including waste. The organic part of municipal waste can be used in several ways. Anaerobic digestion (AD) that produces biogas and compost can be a part of the chain of circular economy of a city. This paper deals with the organic waste generated on the territory of the city of Nis with the focus on its potential in terms of carbon, hydrogen and mineral content. Based on the elementary analysis and quantity of waste, the streams of carbon and other elements that circulate through waste, biogas and compost have also been analyzed. Moreover, energy needs for AD function and transportation of both MW and compost are calculated. The analysis shows that the energy produced by AD can cover the energy needs for the proposed model, and the amount of produced compost is enough to recover nutrients on the majority of green yards in the city.
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