Incineration is a process that involves the combustion of solid waste, which in turn will ... Incineration processes reduce the solid mass of the original waste.
CHAPTER 22
MUNICIPAL SOLID WASTE
Chern Wern Hong, Ngai Weng Chan and Ta Wee Seow Introduction Municipal solid waste (MSW) constitutes daily discarded items by the public and collected by the municipal. They are commonly known as thrash/garbage in the USA or rubbish/refuse in the UK. General composition of MSW can be divided into food waste, papers, plastics, glasses, aluminium cans, e-waste etc. However, industrial wastes, agricultural wastes, medical waste, radioactive waste or sewage sludge are mostly not included as part of composition of MSW. Though, composition of MSW varies from country to country depending on availability of types of waste management system and facilities. According to Figure 22.1, management of MSW spans from the least preferred option, which is via direct disposal to landfill to the most preferred option, which is via prevention of waste creation. Execution of preferred MSW management is based on the municipalities/countries‟ solid waste management, policy, and education system, which constitute the awareness of the general public about the importance to practice waste minimisation.
Figure 22.1: Solid Waste Management Hierarchy The least preferred option of MSW management which is via disposal method consists of solid waste collection process include collection of solid waste at point source (home, shophouse, etc.) by municipalities or private solid waste management company and to be transferred to a dumping site which is popularly known as landfill. Landfills are commonly divided into sanitary (engineered) landfill and non-engineered open dumping site. Sanitary landfills are equipped with leachate treatment technology and are often regarded as the most cost-efficient method especially for countries with vast open spaces or lands. Solid waste are dumped and covered cum compacted with soils to be degraded (Figure 22.2).
154
Figure 22.2: Source: Conventional Municipal Solid (Source: Waste Collection System of Patrick County Taxpayer Watchdog Group, 2015) Depending on the landfill size and „incubation‟ period, the landfill can be converted into parks or even small-scale housing development. For example, the Sai Tso Wan Recreation Ground in Hong Kong was the first ever landfill-based recreational park to be opened. The landfill held approximately 1.6 million tons of waste between 1978 and 1981 and was sealed off with soil only to undergo restoration work from 1995 to 2004 to transform the land into a recreational ground (Figure 22.3).
Figure 22.3: Sai Tso Wan Recreation Ground (Source: Ngchikit/Wikimedia Commons) Just above the least preferred option in solid waste management tier, is the energy recovery option. Energy recovery is a process of generating energy in the form of electricity and/or heat via incineration of waste. Incineration is a process that involves the combustion of solid waste, which in turn will convert the 155
waste into ashes, flue gases, and heat. Incineration processes reduce the solid mass of the original waste by 80-85% and the volume by 95–96% (Han, 2012). This process is particularly popular in land-scarce country such as Japan. In a developed country such as Japan, the heat generated via incineration is recovered for electricity generation. This energy recovery technology could in turn contribute towards offsetting greenhouse gases from fossil sources such as coal, oil and gas-fired power plants. However, as energy recovery is the second least preferred waste management option, incineration technique has its bane on the environment. Without adequate air pollution control technology, the flue gases may contain heavy metals, sulphur dioxide and the most publicized of all, dioxins. Apart from flue gases, the ashes must be carefully gathered and disposed at the landfill. Recycling as an Option in MSW Management Another concept towards promoting waste minimization is the popular 3R concept. „3R‟ simply stands for reuse, reduce and recycle which is based on the „cradle to grave‟ analysis. By practicing this concept, the process of disposing waste or incineration could be reduced apart from utilising of new raw materials. Based on the waste hierarchy, recycling option is preferred compared to energy recovery option followed by reusing, reducing (minimization) and ultimately prevention of waste. Recycling is defined as a process to modify waste materials into new product/material. This practice is to reduce consumption of fresh raw materials as well as reducing waste disposal rate (Murphy, P., 1993). The process of recycling includes collection, sorting and rinsing. Household recyclable items include paper, glass, plastic materials, aluminium and e-waste products. Rate of recycling in a municipality or country depends on the availability of technology, facilities, policy and public awareness. Another challenges faced in recycling process is on the ability to separate and breakdown a product into different parts of material. For example, a smart phone consists of plastic and steel casings as well as electronic components, which could pose challenges in separating them into different parts of materials for recycling process. Ao and Kono (2011) have proposed that a product to be designed in such a way that could ease the process of breaking down into different parts of materials to ease product separation. Recycling, though promotes the reduction in new raw materials consumption, will consume energy for its process. Thus another preferred option is to „reuse‟ an item instead of recycling it. The term „reuse‟ literally means using an item (mostly non-degradable) again after it has been used. Item that is being reused could be in the form of same functionality or modified into different functionality. For example, in terms of same functionality, glass milk bottles are washed and refilled with milk again or rethreading car tires. An example of modified functionality could be in crushed bottles used to incorporate into wall design or reusing the discarded car tires as artificial coral reefs. By practicing „reuse‟, it will lead to savings in energy and raw material consumption as well as reducing disposable waste. This practice will also promote cost saving in economic activities. Some of the disadvantages of „reuse‟ are water is needed for cleaning as well as reduction in efficiency and toxicity especially in old automobiles or electrical appliances. At the pinnacle of waste hierarchy, efficient MSW management system is equivalent to promoting waste minimization and elimination of waste in best possible strategy. This ultimate aim aligns with the umbrella term sustainable consumption that minimizes consumption of new raw materials, energy as well as creation of waste. This strategy can only work with the presence of strong political-will in promoting good solid waste management, improving waste treatment and recycling technology. Inter-city and international cooperation are also possible in terms of resource circulation (for recycling and reusing) to promote zero waste generation.
156
Conclusion In conclusion, solid wastes should not be treated as wastes but should increasingly be looked upon by cities as “resources”. There are several ways in which city governments in developing countries can enhance solid waste reduction. Firstly, citizens should be kept informed and engaged the need for solid waste separation and recycling, and the needs of sold waste workers. Public campaigns are needed as well as extensive public education to develop the public‟s understanding and build the capacities in terms of the need for further source separation to improve the potential for composting and to remove the stigma of association with waste materials. Secondly, cities need to promote recycling industries and enterprises that are green. Green industries must be encuraged at the expense of dirty/polluting industries. Thirdly, composting of organic solid wastes has great potentials and must be encouraged. This is because organic wastes form a major portion of the household solid waste. When reduction of organic solid wastes are dealt with, via successful composting, half the battle is won. Keeping organics pure for composting will require more thorough source separation than is done at present. Fourthly, cities must advocate key areas for waste reduction for industrial sector, especially during the manufacturing stage (e.g., reduction of paper/plastic packaging; coding of paper/plastics to improve recycling). As waste generation and waste reduction reflect many complex economic, social and cultural factors, cosmopolitan cities must study these before implementing any solid waste management system. No one size fits all. It is the same with solid waste management. One strategy may work for one city but will backfire in another. Hence, no city may blindly adopt/adapt recommendations from another city. Each city must examine its own wastes, and the potential for extending waste reduction. Privitization of SWM should be carried out in a transparent manner. Waste reduction should, however, be the first principle of solid waste management. Questions for Discussion 1. With reference to your local city, identify the issues and challenges related to solid waste management. 2. What sort of disposal/treatment is used to manage your city‟s solid wastes? 3. Is treated solid wastes re-used in your city? If Yes, discuss how. If No, why not? Acknowledgements The authors would like to acknowledge funding from the project titled “Developing Optimization Model for Solid Waste Management in Johor Bahru City, Johor”. Research Acculturation Collaborative Effort (RACE) Fasa 2/2013. Grant provided by the Ministry of Higher Education Malaysia. Account Number 1001/PHUMANITI/AUPRM0058. References Ao, M and Kono, N. (2011) Model for Environmental Cooperation in Asia: Analysis of 3 Factors to Convert City to 5R Society Highlighting Yokohama and Kawasaki as a model case (http://siteresources.worldbank.org/INTURBANDEVELOPMENT/Resources/3363871296405826983/7699103-1296623042596/6AoKonoYCUBBL.pdf Accessed on 10 June 2015). Han, D. (2012). Concise Environmental Engineering. PhD and Ventus Publishing ApS ISBN 978-87-4030197-7 Murphy, P. (1993). In The League of Women Voters: The Garbage Primer. New York: Lyons & Burford. pp. 35–72. ISBN 1-55821-250-7. @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 157
