Environmental Management: Principles and practice
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5 2020 03 04!03 12 11 PM
Domestic refuse
Refuse (trash or garbage) disposal can be based on self-help, which cuts the cost and may benefit poor people. Such an approach includes street corner skips which are collected and taken to the tip or recycling plant by a rota of local people. An alternative is to offer an incentive to people to collect waste and bring it to a recycling plant, composter or incinerator. Recycling waste can provide employment, and local authorities or aid agencies could assist by providing protective clothing, supervision, healthcare and refuse handling and processing equipment (where informal and less healthy garbage picking would probably develop anyway). Cities generate large quantities of refuse: in developed countries this can be 500 to 800 tonnes per day per million people. This may be landfilled, incinerated, dumped at sea, recycled or composted. Domestic waste is a mixture: in the UK it is typically (approximately): 7 per cent plastics; 8 per cent metals; 10 per cent glass; 10 per cent fines (dust); 12 per cent miscellaneous textiles; 20 per cent waste food and other easily decomposed material; and 33 per cent paper products (The Times 14 June 1993:32). The trend in developed countries has been towards a greater proportion of packaging materials, much of it non-degradable plastics and metal foil, and a decline in the use of reusable glass bottles since the 1960s, matched by an increase in plastic disposable bottles. This mixture can make sorting and treatment a problem. Tin and steel can be recovered with magnets, and aluminium cans are fairly easy to recycle, but plastics are more of a challenge. In developing countries refuse is likely to contain less packaging and more organic matter, so it may be easier to compost or generate methane from, but more difficult to compress or incinerate. Over 90 per cent of UK refuse was disposed of by landfill in the mid-1990s (North, 1995:164); at the same time in the USA over 70 per cent was similarly disposed of. Landfill sites should be located to avoid nuisance and the risk of contaminating streams or groundwater: a minimum of a layer of clay should be put in place before tipping, and after completion used to cap and seal the tip (Figure 11.1). Many redundant tips and some of those at present in use meet none of those standards and present a serious future hazard because they are poorly sealed. Sometimes domestic refuse is mixed with industrial wastes (co-disposal), power-station flue-ash or sewage POLLUTION AND WASTE MANAGEMENT 213 for convenience or in the hope that it will assist breakdown of harmful materials. Whether it is wise is debated. It is important to locate landfill sites to avoid nuisance to surrounding areas, to reduce the risk of ground and surface water contamination, to minimize damage from escaping methane or underground fires, and to ensure that vermin are not a problem. Houseflies and rodents can cause difficulties some distance from landfill sites if they are allowed to breed, and scavenging birds may pose a serious threat to airports within a few miles (Clark et al., 1992). Provided that decomposition of organic matter is vigorous, a refuse tip should generate enough heat to kill most harmful organisms. However, ‘tip archaeology’ in the USA suggests that paper products may be a major source of contamination of groundwater, streams and surrounding environments because of the printing inks, waxes and sealants used on them. Landfill generates methane, which presents an explosion and fire risk for decades after tipping. Methane, heat from spontaneous combustion, toxic compounds and subsidence limit the future land use of tip sites, although in some cases the gas can be collected and used for power generation or combined heat and power (biotechnology might improve methane production). (For an objective discussion of waste disposal and recycling see North, 1995:164–186.) Plastic waste is a problem in landfill, as litter on land and adrift in the oceans. Some plastics degrade slowly and can cause considerable harm to wildlife (for FIGURE 11.1 Landfill refuse disposal site in Belgium. This is a state-of-the-art facility with geosynthetic clay and high-density polyethylene lining to prevent leaching. Each pit can hold ca. 250,000 tonnes of waste. The gas generated during decomposition will be captured for electricity generation Source: Press release photo from Bitumar N.V. Belgium, 1998 CHAPTER ELEVEN 214 example marine turtles are injured by eating floating polythene bags) and equipment like pumps. Phantom fishing—lost or discarded plastic nets and long-lines—do tremendous damage to wildlife. This might be reduced if biodegradability could be built in. Unfortunately, fishermen do not want equipment to deteriorate before it is lost. What is needed are degradable plastics which quickly rot once lost or discarded. There has been some progress, and laws in the USA, Sweden and Italy insist on biodegradable plastics for certain types of packaging. Germany requires manufacturers to arrange for proper disposal of the packaging materials around their products, and The Netherlands has a covenant with manufacturers which aims to reduce and simplify packaging to aid recycling. About 60 per cent of the world’s shipping should be covered by a 1989 treaty requiring no dumping of plastics at sea (Annex V of the International Convention for the Prevention of Pollution from Ships). However, a glance at any strandline confirms that compliance is lax, and much plastic also gets into the sea from rivers and sewers. Download 6.45 Mb. Do'stlaringiz bilan baham: |
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