Methods of solid waste management
For the proper management of solid wastes different methods have been adopted. Some of those measures are very simple and easy where as some are very complex. Some of those measures are discussed below:
1. Preparation of compost
Organic matter constitutes 85%-90% of the municipal solid waste generated in Nepal. This waste can be recycled by the method of composting, one of the oldest forms of disposal. It is the natural process of decomposition of organic waste that yields manure or compost, which is very rich in nutrients. Composting is a biological process in which micro-organisms, mainly fungi and bacteria, convert degradable organic waste into humus like substance. This finished product, which looks like soil, is high in carbon and nitrogen and is an excellent medium for growing plants. The process of composting ensures the waste that is produced in the kitchens is not carelessly thrown and left to rot. It recycles the nutrients and returns them to the soil as nutrients. Apart from being clean, cheap and safe, composting can significantly reduce the amount of disposable garbage. The organic fertilizer can be used instead of chemical fertilizers and is better specially when used for vegetables. It increases the soil’s ability to hold water and makes the soil easier to cultivate. It helps the soil retain more of the plant nutrients.
|For the purpose of compost preparation, first step is the separation of biodegradable and non-biodegradable wastes. After separation, biodegradable wastes are kept in a pit. The size of the pit and process of preparation depends upon the amount of waste and need of people. The compost preparation is supposed to be suitable method in the context of our country.|
- Aerobic Method: Aerobic composting takes place in the presence of ample oxygen. In this process, aerobic micro-organisms break down organic matter and produce carbon dioxide (CO2), ammonia, water, heat and humus, the relatively stable organic end product. Although aerobic composting may p produce intermediate compounds such as organic acids, aerobic micro-organisms decompose them further. The resultant compost, with its relatively unstable form of organic matter, has little risk of phytotoxicity.
- Anaerobic Method: In anaerobic composting, decomposition occurs where oxygen is absent or in limited supply. Under this method, anaerobic micro-organisms dominate and develop intermediate compounds including methane, organic acids, hydrogen sulphide and other substances. In the absence of oxygen, these compounds accumulate and are not metabolized further. Many of these compounds have strong odours and some present phytotoxicity. As anaerobic composting is a low-temperature process, it leaves weed, seeds and pathogens intact. Moreover, the process usually takes longer than aerobic composting. These drawbacks often offset the merits of this process, viz. little work involved and fewer nutrients lost during the process.
- Vermi-composting: Vermi-composting is the process of using worms and micro-organisms to turn kitchen waste into black, earthy-smelling, nutrient-rich humus. While composting refers to the biological degeneration of organic wastes like yard and food waste by micro-organisms, in vermi-composting, earthworms are used to break down organic wastes into nutrient-rich manure.
2. Sanitary Land fill
Sanitary landfills are sites where waste is isolated from the environment until it is safe. It is considered when it has completely degraded biologically, chemically and physically. A sanitary landfill is a waste disposal facility where layers of compacted garbage are covered with layers of earth. When the facility reaches capacity, a cap is applied to close the site. Sanitary landfills are one of the most popular methods for disposing waste although they have some distinct drawbacks. This technique for waste management was developed in the 1930s, in response to growing pressures created by growing population. Kathmandu valley has been searching for better landfill sites as Sisdol and Okharpauwa are inadequate and there has been political and local pressure. Pokhara valley has also a good sanitary landfill site.
It is the burning of solid waste without the benefit of a device to adequately control combustion, such as those found in solid waste incinerators. We can burn household waste, trees, logs, bushes, papers, twigs, leaves and stumps so as to reduce the volume of the waste as well as we can obtain ashes which can be used as fertilizers.
Incineration is a waste treatment process that involves the combustion of organic substances contained in waste materials. Incineration and other high temperature waste treatment systems are described as “thermal treatment”. Incineration of waste materials converts the waste into ash, flue gas and heat. The ash is mostly formed by the inorganic constituents of the waste and may take the form of solid lumps or particulates carried by the flue gas. The flue gases must be cleaned of gaseous and particulate pollutants before they are dispersed into the atmosphere. In some cases, the heat generated by incineration can be used to generate electric power.
5. Waste to Energy
Waste is the resource at wrong place at wrong time. We can use waste to generate energy and economy. In Europe, the solid waste is used in central heating system and thy also generate hot water to the people. This again can be used to generate electricity. So, Waste-to-Energy (WtW) or Energy-to-Waste (EtW) is the process of creating energy in the form of electricity or heat from the incineration of waste source. It is a form of energy recovery. Most WtE processes produce electricity directly through combustion, or produce a combustible fuel commodity, such as methane, methanol, ethanol or synthetic fuels.