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<Municipal Solid Waste Management> Asia 2.2 Topic c: Composting East Asia/Pacific Backyard composting is a longstanding tradition in countries like Australia, Japan, and New Zealand, especially in rural towns. Now it is being promoted by local governments, with inexpensive compost bins being made available, along with "how-to" leaflets and demonstrations. Garden and park waste are also being composted by solid waste authorities to reduce wastes for landfilling. A large portion of the household organic wastes in Asia is eaten by animals or fed to pets. In cities like Hong Kong, Bangkok, Manila, Cebu, and most cities and towns of China and Vietnam, pig and poultry farmers routinely collect food wastes from households and restaurants for animal feed. In some small Chinese cities, pigs are released on garbage dumps to reduce organic wastes. However, pig keeping itself often leads to pollution of streams and rivers and has been banned, for example, in Singapore. Almost all the large cities of the developing countries in the region in the past installed imported mechanical composting plants (for instance, built six). Most are now defunct and the remaining ones are not operating at full capacity (e.g., Bangkok, Hanoi, Shanghai, and Tokyo). The reasons why centralized mechanical MSW composting plants are not functioning effectively, are underutilized, or are closed down include: (a) high operating and maintenance costs compared to open landfilling (including foreign exchange costs for replacement parts of imported plants); (b) the cost of compost is higher than commercial fertilizers (both cost to purchase, and labor cost to apply to the fields); (c) incomplete separation of materials such as plastic and glass, making the compost poor for agriculture application; and (d) poor operation and maintenance of the facilities. The forced-air plant in Hanoi is typical in operating at only 20% capacity. The city has not even been able to persuade farmers to take the product free, as it is too contaminated with plastics. Instead, it is used on city parks. The traditional open-air windrow process is used in some countries, especially China. In many Chinese cities and towns, there are no garbage dumps, the wastes being delivered directly by collection vehicles to peri-urban farms. The farmers are instructed to compost the waste in windrows or pits for a prescribed period of time, but they often do not do this if they are in urgent need of the organics. It is difficult for the authorities to monitor the farmers' practices. The compost is also increasingly contaminated with plastics and broken glass. It is a common practice for farmers to go to garbage dumps and remove compost in China and Myanmar. The Beijing Sanitation Department is facilitating this practice by supplying sifting machines at the main dump site. Both Ho Chi Minh City and Medan are allowing the mining of compost from dump sites for fees. With recent rapid increases in industrialization, these practices will require greater scrutiny unless there is effective control of toxic substances in the waste stream. Small-scale, neighborhood composting is being promoted through research and pilot projects, especially in Java. There have been experiments for over a decade, and now some small private enterprises have been established in Jakarta that are supplying compost to estate gardens and golf courses. In Bandung there is a type of box windrow composting at one garbage dump. Co-composting with sludge from municipal sewage treatment plants is gaining acceptance at least in cities of industrialized countries where lands are available. High operation and maintenance and transportation costs, along with incomplete separation of waste materials, are major constraints for the adoption of co-composting. There are many technical and aesthetic problems to be solved in the composting of MSW. As one small example, an important, privately run vermiculture experiment in Indonesia failed when toxics in the MSW killed the earthworms. Basic training and education of workers in technical, health, and safety aspects is essential. With better understanding of the process, improved processes, and public education, composting should increase at least in cities where sites and skilled manpower are available, and markets can be developed. The cost of compost, whether used as fertilizer or soil conditioner, is still problematic when compared to costs of synthetic fertilizer/soil conditioner, and this has become a major factor for decision makers. Composting can be viable, especially for smaller cities with intensive agricultural areas near cities. Many international agencies and environmental consulting firms are offering Asian cities technology for composting as the process is increasingly gaining importance in all parts of the world. An issue here is whether the equipment offered is appropriate for the wastes of that particular place. Biogas technology is well known in smaller towns in rural areas in China through government policies of comprehensive utilization of wastes. However, these biogas digesters use human and animal feces as the main feedstock. Some agricultural wastes may be added. The number of biogas digesters in rural towns is declining with the breakup of communes. Household-level digesters have not proved practical. The potential remains for anaerobic digestion of wastes, but organizational problems need to be overcome. South and West Asia Since the organic fraction of the waste stream is high in most places, there is considerable interest in composting of MSW in the region, and a long history of experiments with composting. Large-scale centralized composting (as distinct from neighborhood composting) has had little success; pure anaerobic digestion has been tried rarely and only in pilot projects in the region. In the 1960s many mechanical compost plants were constructed, often promoted by foreign firms. In India, the central government gave grants to eight cities to install plants (of foreign design, with imported parts) and the principal cities in the northern and central countries of the region built similar plants. Almost all of these are now not operating or are producing at a fraction of capacity, because they were unsuitable for the local wastes, parts and skilled operators were not available, and/or the product was too expensive or not good enough to secure markets. Although one of New Delhi's plants has been closed, another is still operating. The compost is absorbed by the city's parks department, an example of how city procurement policies can help the marketing problem. In Kathmandu, the compost from a municipal plant was in high demand by local farmers in the late 1980s and early 1990s, and the plant continued with a simple windrow system after the machinery broke down. It was forced to close recently when residents of new housing estates protested. Recently, however, private firms, alone or in public-private partnership, have revived centralized composting in a few places. Bangalore's windrow compost plant is reported to be cost-effective since privatization, although there are now NIMBY ("Not In My Back Yard") pressures at the site. There are experiments with new techniques for producing compost by processing partly decomposed wastes at dump sites (being done by a private company subsidized by the Bombay and Ahmedabad municipal corporations). In some middle- and high-income economies, private firms are also reported to be operating effectively and are and able to market the compost locally or to other countries. In Sharjah, UAE, a compost plant is run by the municipality; there are, however, marketing constraints. In Israel, the Ministry of Environment reports that 20,000 metric tons of organics are converted into compost annually. Analysis of the compost from some plants in these areas, however, has shown high levels of contaminants, especially from nickel-cadmium batteries. Backyard composting is casually practiced in areas where there are home gardens, the bulk of the input material being yard waste. This practice has been strongly discouraged by city health officers (for instance in Bangalore) after complaints about rodents. Consequently, backyard composting has declined in the past twenty years. In the past decade, several projects have been initiated for small-scale, neighborhood-level composting. In Bangalore, the Waste Wise Project of the Mythri Foundation and the Centre for Environmental Education are both combining worm culture with composting on a small scale on land provided in local parks by the City. Bangalore University is giving advice on worm culture. Pilot research and development projects for the region are included in the current UNCHS project on small-scale digestion and composting of MSW. The natural process of decomposition at waste disposal sites is commonly exploited by farmers and sometimes by the municipal corporations in cities and towns of the Indian subcontinent. Farmers go to dumps to remove compost, thus extending the life of the dumps. The Corporation of Calcutta leases out dump land at the city's main dump for vegetable farms. Small dumps near squatter settlements are regularly farmed. There are no studies of possible health risks from these practices. The subcontinent has wide experience with anaerobic digestion of cattle dung, and it was assumed that similar digesters could be adapted to ferment MSW, but producing animal-dung-like slurries from urban organic waste proved energy-intensive and the product was poor. A major problem with anaerobic digestion is that MSW used as feedstock tends to float. A number of design changes have to be achieved to produce small-scale digesters. Research is being done in Bangalore at the Indian Institute of Science, but there are no reports of successful large-scale anaerobic digestion.
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