By Dr. Solmaz Rezaei
Head of research and consulting department
Urban waste management is one of the issues that has a direct impact on different economic, social, cultural and environmental dimensions in cities, and today the management policies of countries in areas such as culture and citizenship education, use of modern methods of collecting and transporting waste, special attention to recycling from the origin, move toward less waste generation, and the use of waste recycling technologies are among the definitive principles of such a management. In the available definitions, waste refers to all waste from human activities, which based on the source of production, includes ordinary, industrial, medical and agricultural wastes. In addition to environmental pollution such as water pollution and soil contamination, waste is the main source of global greenhouse gas emissions. For example, waste is the source of more than 37% of greenhouse gas emissions released in the United States. Research has also shown that more than 30 human diseases are directly and indirectly related to the destructive effects of waste management. Currently in cities of Iran, more than 34 billion rials per day is invested for collecting and disposing of waste, which, in addition to the environmental damages caused by the production of urban wastes, necessitates serious attention to this issue.
Since the composition of wastes varies according to the type of culture and lifestyle from one country to another and even in different cities of a country in different seasons of the year, there is not a completely identical solution for the problem of urban waste. However, today in leading cities, the priorities of municipal waste management include avoiding production, reducing production, recycling materials and energy, and eventually landfilling of waste.
Municipalities, contractors and citizens are the three pillars of urban waste management, so informing citizens about urbanization tasks and creating a sense of commitment to participate in urban waste management is an essential element of the success of such a management. The incorrect recognition of waste management by some citizens as a tool that eliminates waste from the personal environment and the lack of awareness on the effectiveness of reducing waste generation and the separation of waste at source will reduce the returns of related measures in this area. As an international experience in Hong Kong in 2005, the first phase of waste separation project began with more than one million households, which, with increasing citizen participation, recovered domestic waste by around 23% in 2007.
Until 1950, in many parts of the world, urban waste was largely eliminated in open pits, but today, waste management involves new technologies based on waste collection, transportation, processing and disposal. In addition to preventing harmful environmental effects of wastes, such as the production of dangerous leachate and greenhouse gases, these measures produce recycled products that are usable. One of these technologies in the collection and processing sector is the use of RFID or radio frequency identification, in the dispensing section, sanitary landfill, biogas and compost, and in energy production sector, the production of plasma gas, production of fuel from waste (RDF) and waste incinerator can be mentioned, which we will look more closely at some of them in the following:
Radio Frequency Identification: In this method, the microchip tags are attached on the waste bins according to the type of waste, and the readers are installed on the garbage truck and the data associated with the central system. This system tracks the position of the garbage truck, the time of garbage collection and the transportation route and optimizes the process of garbage collection.
Radio Frequency Identification: In this method, the tags of the microchips are transmitted according to the type of waste on the waste bins and the readers are installed on the garbage truck and the associated data are transmitted to the central system. This system tracks the position of the garbage truck, the time of garbage collection and the transportation route and optimizes the process of garbage collection.
Compost: One of the best methods for recycling urban waste is to collect organic waste and purify it in a way that the product can be used as soil modifier.
Waste Incineration Plants: In this system, urban waste is mixed in the waste incinerator and used to generate heat energy. Today in the world there are about 600 waste incineration plants with an energy production capacity of 7,000 megawatts. At present, according to EU rules, the landfill of waste is very limited.
Power generation from waste landfill: By waste disposal from households and in the absence of oxygen after the decomposition of waste, a mixture of methane, carbon dioxide, hydrogen, and other compounds is produced. After certain steps, gas capable of running various generators for power generation is produced. This method has lower initial investment and maintenance costs than other existing technologies. The power generation capacity of this method was more than 9,000 megawatts by 2010.
Alternative fuel or RDF: In this method, the fuel-containing components of the waste are completely dried after a suitable process, for proper combustion. RDF has the ability to burn in a power plants or in cement furnaces and reduce up to 50% of fossil fuel consumption in these furnaces.