Waste composition, typical landfill

This example adapted from Bamicki Fair (1992) presents the separation and purification of a typical landfill gas produced by anaerobic decomposition of municipal waste. This contains approximately 200 kg organics/ton waste. The gas composition is 40-60 mol% CH4, 40-50 mol% CO2 and 5000 ppm various impurities. A medium-size plant can produce between 50000-60000 mVday methane. Table 7.14 shows the initial landfill gas composition, as well as product specifications. 

The pattern of gas production assumed to be typical of landfill is shown in Figure 6 and is based on that proposed by Farquhar and Rovers (1973). In this figure, no scale is included on the "x"-axis, for e length of time taken for each process will vary considerably from site to site, according to a number of factors including, waste composition and local environmental conditions. Therefore, the timescale over which pollution events can occur as a result of gas migration will also be site dependent and could vary between a few years and more than one hundred years. For effective pollution prevention, it will be necessary to monitor and exen control for a similar time period, with important cost implications. 

One recycling issue that is important throughout the developed world is what to do with the approximately 300 million TVs and computer monitors that are thrown out each year. The European Union Waste Electrical and Electronic Equipment Directive have banned them from being dumped in landfills because the screens contain PbO added to shield against the X-ray radiation released by the high anode voltage. Table 37.9 shows typical compositions of cathode ray tube (CRT) glasses. 

Within waste disposed to landfill, vegetable matter, paper and cardboard and to some extent, textiles are all biodegradable. Although, as shown in Table 6, the composition of municipal refuse varies from country to country and will vary from season to season. In the developed world it typically contains about... 

Construction and Demolition (C D) waste typically consists of concrete, bricks, asphalt, wood, glass, masonry, roofing, siding and plaster, alone or in combinations. Intermediate C D landfills must have a 3-foot-thick clay liner and a leachate collection system. The diameter of leachate collection pipes must be at least six inches. Engineered landfills for municipal and industrial waste are constructed with a base liner and a leachate collection system. The primary purpose of the liner is to prevent grormdwater pollution. The liner may consist of clay only or be a combination of geomembrane and clay (known as a composite liner). The liner is constructed with at least a 2% slope towards perforated leachate collection piping to direct leachate to a collection system. 

Combinations of PP with PE have also been reported. Arnold et al. reported the creation of an all-polymer composite by using woven PP tape fabrics or short PP tapes shredded from waste fabrics as the reinforcement in a LDPE matrix [69]. Fibre volume fractions of up to 61 % were achieved by consolidating PP tape fabrics between LDPE films. Although the mechanical properties of the final composites were not competitive compared to some of the other composites described in this review, the concept of using waste fabrics to enhance the properties of low stiffness LDPE is attractive since the materials used would otherwise typically be disposed of via landfill. 

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