Abstract
Nowadays, generating energy is discussed as a paramount option in waste management, because the share of energy from waste is increasing annually. The ever-increasing need for energy and limitations of using fossil resources, and also the increase in environmental pollution from consuming these resources have made the use of renewable energies of especial importance. In this research, we first studied renewable energies, followed by technologies related to the biogas system. Biogas systems have been referred to by landfill and discussed comprehensively in this scheme for utilization. For this purpose, the input source of this system is considered as the volume of garbage in the city of Germi as the study area. In the next step, the amount of garbage produced in this city was extracted and the Landfill software was used for methane production potential assessment from this system and the Homer software was used for economic analysis and reliability evaluation. The most important results are payback period, which is about 10 years, and the amount of electricity produced per year, which is 11658.265 MWh.
1. Introduction
Waste incineration is a process by which garbage or brown coal (sewage sludge) is ignited in the vicinity of the heat and produces materials such as ash and exhausted gases from the chimney as combustion products. During this process, most of the metals and metal compounds in the waste remain unchanged and can be extracted from the resulting ash. The most important advantages of the waste incineration method are the large reduction in the volume and weight of waste and sewage sludge without the need for a long time or a large area of operation, the elimination of most hazardous waste and consequently reduction of environmental degradation, and the possibility of energy recovery as electricity or heat from the heat released during combustion of these materials as well as the possibility of recycling metals (both ferrous and nonferrous metals) from combustion products [1, 2]. The minimum thermal value for waste generation is estimated at 7,000 kJ/kg. Today, the global waste incineration capacity for waste disposal, along with the generation of energy and recycling of metals from municipal solid waste, is about 130 million tons a year, with around 600 large waste-to-energy incineration plants in the world, which are often in the first world countries. The burning of solid municipal waste and sewage sludge is a controlled process in which solid waste is burnt and turned into ash, and the remaining is converted into safe or low risky gases [3–5]. In European countries due to strict environmental regulations, there are special filters in the exhaust outlet so that the harmful gas is filtered and added to the ash. In this method, the amount of waste is reduced by up to 90%. Waste incineration is one of the ways to dispose of solid municipal waste. This method is especially applicable in cities with a problem of land shortage. In addition to reducing volume, these devices can also be used to reduce or eliminate toxic substances. In general, materials such as municipal waste, organic chemicals, radiological materials, biological materials, fire-retardants, explosives, and sewage sludge from the wastewater treatment plants can be burned in waste incinerators. The benefits of burning waste can include reducing the volume of the plant, reducing the volume of waste, reducing the volume of the waste garbage, removing hazardous waste, reducing costs, eliminating the risk of contamination of surface water, reducing the odour, reducing greenhouse gas emissions, reducing the amount of air pollutants, and destruction of the habitat of vile animals. Among these technologies, there is also a kind of technology called biochemical in which the waste materials are buried and gases such as methane and ethyl alcohol derived from biodegradation are collected by buried pipes in the ground and are used for fuel use at the plant. Gases such as methane can also be obtained in another way called anaerobic digestion [6, 7].
Biogas is also one of the biomass products. The process of decomposing biomass resources is by bacteria in the absence of air, in which methane and secondary products with moderate thermal value (biogas) are produced. The most prominent example of this process is in landfill. In the past few years, digestion tanks have been significantly noticed. The anaerobic digestion takes place at a relatively wide temperature range of 10–60 Celsius. All materials used to produce biogas in the process of anesthetic digestion should be made up of organic materials that essentially contain proteins, lipids, and carbohydrates. This organic matter is decomposed by a group of bacteria in the absence of oxygen, and the digestion efficiency is also affected by digestibility, pH, carbon to nitrogen rate, time remaining, and the presence of toxic substances for bacteria.
The primary sources for the production of biogas are livestock feces, plant remains, food waste and corrosive organic materials, organic waste, sewage, and agricultural waste products. All these methods are somehow biogas [8, 9]. Biomass resources contain organic compounds with coarse chain molecules that break down molecules into simpler molecules during digestive processes (buried in the ground, in special tanks or abandoned in nature). The ultimate outcome of this flammable gas process is called biogas. Biogas is also called methane [10, 11]. Some studies in the field of biogas are mentioned.
Urbancl et al [12] presented the evaluation of heat production using municipal biomass coincineration within a thermal power plant. Santos [13] presented an energy recovery from municipal solid waste materials for boilers of incineration plants. Lee et al. [14] presented an energetic and economic feasibility analysis of utilizing waste heat from incineration facility and power plant for large-scale horticulture facilities. Petridis et al. [15] studied a DEA/Goal programming model for the performance of incineration plants. In the UK, Di Gianfilippo et al. [16] presented LCA of management strategies for RDF incineration and gasification bottom ash based on experimental leaching data. Costa et al. [17] presented CFD modelling of a RDF incineration plant. Toniolo et al. [18] assessed the “design paradox” with life cycle assessment, which is a case study of a municipal solid waste incineration plant. Walser and Gottschalk [19] presented stochastic fate analysis of engineered nanoparticles in incineration plants. Solheimslid et al. [20] presented calculation of first-law and second-law-efficiency of a Norwegian combined heat and power facility driven by municipal waste incineration, which was a case study. Li et al. [21] presented government responses to environmental conflicts in urban China, which was the case of the Panyu waste incineration power plant in Guangzhou. Huang et al. [22] presented public acceptance of waste incineration power plants in China, with comparative case studies. Wang et al. [23] presented characteristics and trends of research on waste-to-energy incineration, with a bibliometric analysis, 1999–2015. Tang et al. [24] presented energy analysis and environmental impacts of a MSW oxyfuel incineration power plant in China. Košnář et al. [25] presented investigation of polycyclic aromatic hydrocarbon content in fly ash and bottom ash of biomass incineration plants in relation to the operating temperature and unburned carbon content.
Given that 45 mg of waste is produced daily in urban areas of Germi, the dumping of this waste requires large areas away from food and water resources, and on the other hand, landfill is one of the most outdated and harmful ways to the environment. One of the drawbacks to this is the leachate produced from the waste that can easily penetrate to agricultural land and underground water resources. These leachate, due to the uncertain mix of different chemicals, have unknown properties and sometimes very toxic compounds.
The waste incineration plants, in addition to the very low cost of consuming fuel, contribute to the conservation of the environment. The enlargement and power output of these power plants and the prediction of the cost of constructing and operating these power plants requires precise economic assessment. This economic assessment will be carried out in the city of Germi based on the amount of waste produced and its growth rate.
In this research, contrary to the research studies conducted and mentioned above, first, the potential of municipal waste is measured and then for the realization of the present research, the estimation of urban waste is performed for a period of 20 years and then to objectify the present project, economic and energy analysis with the approach of supplying part of the electrical energy required by the building sector of the study area has been performed and then environmental analysis has been done to complete the research.
2. Materials and Methods
The waste incineration plants are one of the most polluting waste disposal methods, but if not designed properly, they will not have a good performance and will have environmental negative impacts. Due to the fact that the fuel consumed by the incinerator does not have a stable composition, Germi’s waste has been tested for its physical and chemical properties and its thermal value has been determined. Following technical, economic, and environmental studies of various waste incineration technologies, the appropriate technology is selected according to the characteristics of the waste and other effect parameters and the design of the waste incineration plant is based on the above information and environmental criteria. Generating power capacity and selecting the type of generator of these plants are designed according to each region and according to the type and volume of waste. Germi is a city in and the capital of Germi County, Ardabil Province, Iran. Germi is one of the old cities of Ardabil province of Iran and the center of Germi County and a part of Mughan plain. The county’s area is almost 1725 square kilometers (latitude: 39.02139, longitude: 48.08000).
2.1. Sources of Waste Produced in Germi
The sources of waste products in the city of Germi have been investigated, and the obtained information is summarized in Table 1.
2.2. Estimating the Electrical Energy Potential of Germi Biomass Sources
Today, energy extraction technologies (electrical and thermal) from biomass resources have become widespread, and these resources are the second largest source of nonfossil energy supply in the world. The prerequisite for energy extraction from these resources is the availability of appropriate information on the potential of resources and the amount of energy that can be extracted from them. In this project, we try to estimate the amount of energy extracted from biomass resources in the city of Germi based on the documentary information.
2.3. Biomass Resources Studied in Germi
2.3.1. Solid Waste (Garbage)
An important part of biomass resources is municipal solid waste. With high corrosive materials, these materials are capable of generating a large amount of greenhouse gases through biochemical interactions [26, 27]. Municipal solid waste includes solid materials from commercial, office, home, and in-town industries. In Iran, the corrosive rate of these materials is generally more than 60%, and its moisture content is higher than 65%. In order to estimate the amount of energy that can be extracted from Germi’s waste, there is a need for accurate information on the amount and composition of the produced waste, so that the amount of recoverable energy can be estimated by analysing information based on energy extraction technologies from urban dry waste.
In order to calculate the potential of urban waste, it should be theoretically noted that, each volume of biomass resources has its own energy potential, but it may not be economically feasible to extract this amount of energy. Therefore, in order to estimate the potential of solid wastes generated in Germi, it is more efficient and economical to consider waste collection (if possible) that will result in lower energy costs of electrical energy [28].
2.4. Determination of the Thermal Value of Garbage Waste
Regarding the governing relationships, the analysis of Germi’s garbage is carried out and the results of the analysis are presented in Table 2.
2.5. Analysis of Germi Waste
One of the notable negative characteristics in Germi waste is high humidity which is about 60%, and it reduces its thermal value. The average thermal value of Germi waste is 7.907 Mj/kg. According to the recommendation of the World Bank, in connection with the low minimum thermal value required for the construction of a waste incineration plant (7 Mj/kg), it can be concluded that the thermal value of the waste garbage is at a minimum and should be achieved by dehumidifying to the desired thermal value. Also, with the expansion of waste sorting and dividing waste into dry and wet, it can also significantly increase the thermal value.
As shown in Table 3, reducing the moisture content of the waste can increase the thermal value and therefore the amount of electrical energy produced. The landfill waste input for Germi from 2014 to 2016 is given in Table 4
2.6. Estimation of Input Landfill Waste
Assuming that there is no limitation in Germi landfill in 2014 and considering the 20-year plan for using it, the amount of landfill waste input from 2014 to 2033 is estimated considering population growth, waste per capita per person, waste amount in previous years (according to extracts from the Department of Municipal Affairs and Provincial Governor Councils), and according to the physical analysis and the percentage of waste generated in the production of methane in the landfill area using the EViews software and the following equation.where Y is the landfill waste input and X is the year of landfill waste input.
The EViews software uses the constants C1 and C2 to establish a linear relationship between the variables X and Y.
Software considers the C1 and C2 constants as factors such as population growth rates and other factors that influence this. The EViews software and waste estimation equation are shown in Figure 1. Figure 2 shows the result of estimating the amount of waste generated in EViews software analysis.
2.7. Analysing the Produced Gasses from Wastes after Being Buried by Landfill Method Using LandGEM
One of the most important methods for disposal of waste in the world, including in the city of Germi, is the method of disposal of solid waste by sanitary landfill. At landfills, as a result of biodegradation of organic matter in the waste, a variety of gases are produced, most of which are methane and carbon dioxide. These gases are polluting the environment due to the greenhouse effect. Therefore, careful studies are needed in order to know more about how these gases are released from landfills and their effects in order to create useful strategies for their proper control and management.
2.7.1. Input Information of Germi Landfill
The methane production potential has been obtained according to the standards that the software was designed for, so the calculated low value for urban waste is 170 grams per m3/mg. In methane generation rate (k), factors such as humidity of the environment are of particular importance, since waste with a mean moisture content of about 60% is considered as a city with semihumid waste. The value of 0.05/y is obtained for k. In this software, the production of four major pollutants of methane, carbon dioxide, total gas, and organic compounds without methane will be calculated and expressed in terms of charts and tables.
Landfill’s other information, such as the landfill open year, landfill closure year, capacity, and weight of existing and estimated waste, is included in the LandGEM software.
3. Results
3.1. Results of LandGEM Software Analysis
The results obtained by analysing the software for the gases from landfill are shown in Table 5 and Figures 3 and 4.
After estimating the extraction of methane and other gases from landfill over the course of the 20 years studied by using the LandGEM software, the obtained information analyzed through technical, economic, and environmental aspect using the Homer software.
According to the average electric power generation during the studied period which is 8502157.9 kWh, the estimated power plant is 1 MW. It means that, based on the potential of urban waste of Germi, this waste is capable for building a power plant with a capacity of 1 MW.
3.2. Economic Analysis of a Landfill with Capacity of 1 MW
Among renewable energies, biomass energy, especially gas extraction technology from landfill sites, is one of the most economical methods of generating electricity. To analyze the economics of landfill with capacity of 1 MW, simulation was carried out to estimate investment costs using the Homer software. The landfill simulation with capacity of 1 MW is shown in Figure 5.
According to the results of simulation of this process, the investment cost will be 1544400256$ and the variable cost will be 5446428.57$. Each unit of electrical energy produced by this system will cost about 14.3$. The result of 1 MW landfill simulation by Homer is shown in Figures 6 and 7.
According to the simulation, the electric power produced by this plant will be 11658.265 MWh/year, equivalent to 1.3 MW.
3.3. Environmental Analysis
In energy extraction from landfill gas, reliable technologies are used for landfill gas trapping. Environmental analysis of the biomass power plant using the Homer software is shown in Table 6.
According to the results of the Homer software, the environmental analysis shows that with setting up of this plant, the emission of carbon dioxide can be reduced by 7433850 kg/year and carbon monoxide gas by 25052 kg/year and other toxic gases to a specified extent.
4. Conclusions
Increasing population, increasing energy consumption, pollution of fossil fuels, environmental pollution, and declining resource resources have prompted researchers to research alternative fuels. Alternative fuels that do not have the mentioned problems can be sources such as solar, wind, biomass, geothermal, and hydropower, among which biomass resources seems to be a good option due to its presence in all areas. Biomass energy is available in all places where there is population, and the larger the population, the higher the amount of this resource, so it is suitable for cities with high population. With this method, in addition to producing energy and supplying part of the energy required by the area, pollution caused by this type of source can also be prevented. In order to supply the required electrical energy of the study area from biomass energy, first, the amount of biomass production estimated for 20 years has been done using the LandGEM and EViews software and then, the Homer software has been used for economic, environmental, and energy analysis. From the results of this research, it can be said that(1)Nonreliance on fossil fuels due to their high and rising costs and the expiration of their content(2)Diversification of energy sources in order to ensure its security(3)Reduce fuel consumption, export, storage, or production of more value-added oil derivatives(4)Reducing greenhouse gas emissions and eliminating environmental pollutants
Data Availability
The data used to support the findings of this study are included within the article.
Conflicts of Interest
The authors declare that there are no conflicts of interest.
Acknowledgments
This project was approved in the Germi Branch of Islamic Azad University, so the authors thank all the staff of this institution.