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Skládky v Karibiku a Latinské Americe - situace dle UNEP

16.06.2003
Odpady
Skládky v Karibiku a Latinské Americe - situace dle UNEP
The use of landfills in Latin America and the Caribbean has increased significantly in the last decade. All capital and other large cities in South America, Mexico, Costa Rica, and Trinidad and Tobago have landfills of some sort. Many of these landfills, however, are more like controlled dumps: someone checks (but does not weigh) trucks entering the site, and waste pickers do not actually sleep on the site. In many cases, the wastes are covered daily. However, there is neither a clay nor a synthetic lining, often no leachate collection system, and no environmental monitoring. Altogether, approximately 60% of the waste generated in the region is disposed of in such \"landfills.\" Some large cities in the region (including Belo Horizonte, Buenos Aires, Guayaquil, Medellin, Mexico City, Santiago, and Sao Paulo) do have state-of-the art landfills. Landfill design in these cities typically consists of an initial clay layer, followed by a sand or ground stone layer. Synthetic liners are not usually used except for some new landfills in Argentina, Brazil, and Chile. Leachate collection systems are used, the landfills are subdivided into cells, and they have chimneys for gas ventilation. Wastes are covered daily with topsoil. When full, landfills are closed by covering with a clay layer and topsoil, then revegetated. To get a more rounded picture, one can look at a World Bank analysis of landfills in Mexico: a total of 97 controlled final disposal sites were identified, of which only 11, mostly located in the northern part of the country, had equipment and instrumentation features that could allow them to be considered landfills, rather than dumps. Many Mexican landfills face significant operational and environmental problems, as access and disposal are uncontrolled and leachates not contained, treated, or monitored. This analysis concluded that only 15% of the MSW generated in Mexico is disposed of adequately. In most landfills in the region, leachates go untreated, resulting in their infiltration into ground or surface water. Some notable exceptions are landfills in Santiago (where rainfall is very low) and in Brazil, which recirculate the leachate into the landfill, and one landfill in Buenos Aires, which has physical/chemical and biological treatment of leachates. Mexico City has also installed a treatment system in one of its landfills. Because of the high organic content of the region\'s wastes, landfilled wastes tend to produce methane relatively quickly. Nevertheless, this gas is only used in Chile (Santiago and Valparaiso), where three landfills have gas collection systems. The gas is used by the cities\' gas companies and reaches approximately 30% of the population in each of the cities. In Rio de Janeiro landfill gas was formerly used as fuel for trucks and in heavy machinery. With falling gas prices, however, it is now cheaper to use commercial gas. Central America (except for Costa Rica), the Guyanas, and most Caribbean countries do not have landfills. This is also the case for all non-capital cities in Bolivia, Ecuador, and Peru, and for many medium-sized cities with the exception of those in Chile, Cuba, Trinidad and Tobago, and Colombia. In the absence of landfills, wastes are disposed of in open-air dumps. These dumps pose significant environmental health risks, which, in some cases, have been documented. Waste pickers enter freely into the dumps, sometimes living there. These people gather a wide range of materials, including food residues to feed pigs. Though attempts are constantly made to prevent waste pickers from entering dumps, these efforts are usually unsuccessful. In one case in Colombia, however, both waste pickers and former guerrillas were trained and financed to start recycling and street cleaning enterprises when one dump was upgraded. Many landfills are operated by private enterprises, particularly in Argentina, Brazil, Chile, Colombia, and Mexico. Typically, the land is owned by the local government and is given to the enterprise, which works under a concession contract. There is no authorized disposal of MSW at sea. However, some of the poorer coastal cities do deposit MSW on river banks and by the ocean. The wastes are then washed into the ocean. There are also several cases where land is being gained from the ocean by filling with demolition wastes. MSW ends us in these places, too, causing serious odor problems. Manual landfills In cities with less than 50,000 inhabitants, manual landfills are being developed. Manual landfills are similar in design to mechanized landfills except for their size and the equipment they require. These landfills have the capacity to receive 10-50 tons per day of wastes. They sometimes require the use of heavy equipment, but only for periodic preparation of the terrain. Otherwise, landfill operation is carried out manually, including cell preparation, compaction, daily cover, and cell closure. The capital and operation and maintenance costs of these landfills are lower than a mechanized landfill. The most successful cases are in Colombia, although Chile, Costa Rica, Honduras, and Peru all have manual landfills, and Ecuador and Panama are planning to have them. Manual landfills are often the best option for small cities and towns. In Peru, a manual landfill in Cajamarca is working well, serving 80,000 inhabitants and processing about 40 tons/day. Those involved in manual landfills in Colombia believe that in general 20 tons/day is the maximum that such facilities can reasonably handle. Zdroj:UNEP
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