ABSTRACT

Landfilling is the ultimate disposal technology which is relevant even when other advanced options are being used for recycling and/or volume reduction. It is the method of choice in developing nations because it is the lowest cost disposal option. Indeed, most industrial nations, including many European Union countries and the USA, still rely on landfilling as an integral part of solid waste management infrastructure. The steady increase in per capita waste generation since the 1970s, and the total quantity of waste, has sustained and expanded the demand for waste disposal capacity and increased the potential for releases of landfill gas and leachate in the absence of properly designed, installed, and operated emission control measures.

The amount and composition of municipal solid waste generated in a community depends on the levels and patterns of consumption. However, the quantity and quality of waste that finally enters the landfill is influenced by many factors including national waste management strategy, volume reduction measures, such as incineration, in place, and the availability and efficiency of waste recycling programmes. The latter is at a very low level (informal recycling excluded) in most developing nations, or due to lack of transparency, accurate data is not available. Informal recycling is the norm in several developing countries, particularly at the larger dumps serving urban areas. An estimated 2% of the urban population in Asia and Latin America depend on waste picking. There are about six million waste pickers in China, whereas the third largest economy in Asia, India, has one million people involved in waste picking.

These informal waste pickers undeniably contribute directly towards the quantity and composition of waste that ends up in the landfill. When waste recycling rates are high, landfilled waste is mainly the organic component, as in India, whereas the recyclables are diverted for better income to middle men. Recycling undoubtedly would enhance the lifespan of landfills, since it is estimated that in Mexico, waste scavengers remove 10% of the waste, while in Bangalore (India) 15% of the waste is reduced due to recycling. Materials diverted away from landfills via recycling means resources are saved.

Emissions from landfills, mainly landfill gas (LFG) and leachate, are directly related to the quantity and quality of waste disposed. Almost 65 to 80% of collected municipal solid waste is disposed of into landfills in developing nations. The bulk of the waste materials disposed of (40 to 70%) are organic in nature. As a consequence, landfills are a significant source of greenhouse gas (GHG) emissions, as at present 90% of the world’s landfills are dumpsites without proper LFG collection systems. Indeed, landfills are considered the largest human-caused source of methane in the atmosphere.

The methane fraction of LFG is a potent GHG as its global warming potential (GWP, 100 years horizon) is around 25 times higher than carbon dioxide. Thus, landfills are identified as a significant contributor to global warming. However, due to the growing international concern on climate change, the move from landfill-based to resource recovery-based waste management is becoming increasingly important. For example, anthropogenic methane emissions can be collected and used as fuel to generate electricity. Alternatively, organic wastes can be composted to produce a high-quality soil amendment that is valued by farmers and gardeners. These types of projects create both economic and environmental benefits for environmental sustainability. The sale of certified emission reduction (CER) credits [created through application of the Clean Development Mechanism (CDM) under the United Nations Framework on Climate Change Convention] can generate revenue streams that support waste emission reduction projects. Each CER is equivalent to 1 tonne of CO2, traded by industrialized countries to meet their emission reduction obligation under the Kyoto Protocol. However it is most likely that the installation of CDM LFG recovery projects in developing countries will come to a halt in 2013 when the Kyoto Protocol will end. Currently the number of CDM projects is declining due to the financial constraints in developed nations.