Long-term Impact of Excessive Solid Waste Generation on the Environment
The world's accelerated economic development in recent decades has led to a rapid urbanization and an uncontrolled population growth in urban centers such as Tokyo, Seoul, Hong Kong, Taipei, and Shanghai. Changes in the consumption patterns of the region’s urban dweller have resulted in an excessive generation of municipal solid waste (MSW) (Figure 1).
Figure 1. Open Dumps of MSW in Developing Countries
So far, landfill is the most widely employed for MSW disposal worldwide. Landfill can be in the form of an uncontrolled open dump or of a full containment site engineered to protect aquatic environment. Unlike engineered landfills, open dumps do not have bottom liners to prevent the seepage of leachate. Nor do these traditional landfills have a top cover or other preventive measures to reduce methane emission into the atmosphere.
Methane and carbondioxide are two major gases produced from the decomposition of the organic fraction of solid waste in the landfill. Methane gas (CH 4) has a 21-fold global warming potential (Figure 2) as compared to carbon dioxide (CO 2). According to the Intergovernmental Panel on Climate Change, such emissions contribute to 18% of the total methane emissions to the atmosphere, ranging from 9 to 70 Tg (megatonnes) annually. Therefore, landfills have been implicated as the largest source of atmospheric methane in the world, leading to a natural phenomenon called "global warming" (Hansen, 2005a).Due to global warming, changing temperature and rainfall patterns will bring a variety of pressure upon plant and animal life. If temperature rises as projected, one-third of species will be lost from their habitat, either by moving elsewhere or by becoming extinct (Hansen, 2005b).
Figure 2. Phenomena of Global Warming
Apart from global warming, traditional landfills like open dumps pose serious threats to aquatic environment. One of the greatest environmental concerns associated with MSW landfilling is the generation of leachate. During degradation process, one tonne of landfilled solid waste generates about 0.2 m3 of leachate, depending on the type of waste and seasonal climate. This wastewater primarily results from the degradation of the organic portion of the waste in combination with percolating rainwater and moisture that leaches out organic and inorganic constituents through the waste layer in the landfill Depending on rainfall conditions, the color of leachate varies from black to brown.
A landfill site may still produce leachate (Figure 3) with a high concentration of NH 3-N for over 50 years after filling operations have ceased. If not properly treated, leachate seeping from a landfill can enter the underlying groundwater, posing potentially serious hazards to the environment and to public health. For this reason, the generation of leachate has become a worldwide environmental concern in recent years.
Figure 3. Landfill Leachate Generation
Considering the consequence of excessive MSW generation worldwide, an integrated solid management plan and its implementation needs to be undertaken consistently. The outcomes of the scheme may provide inputs for local government and relevant stakeholders such as landfill operators to formulate and implement integrated MSW in a holistic manner. These strategies may provide a policy framework to accomplish the target of reducing MSW generation worldwide by 1% annually. Overall, the proposed approach above aim at facilitating wayes to achieve an environmental sustainability, one of the UN Millennium Development Goals (MDG), by 2015.
References
Hansen J (2005a). A slippery slope: How much global warming constitutes “dangerous anthropogenic interference”? Climatic Change 68(3): 269-279.
Hansen J, et al. (2005b). Earth's Energy Imbalance: Confirmation and Implications. Science 308(5727): 1431-1435.
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