Landfill Degradation

The use of biodegradable shopping and waste bags may have the potential to increase the rate of food degradation in landfills, and therefore has the potential to enhance methane harvesting potential where infrastructure is in place and decrease landfill space usage. The use of biodegradable plastic film as daily landfill covers has the potential to considerably extend landfill hfe, as they could replace traditional soil cover material which uses approximately 25% of landfill space. 

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Nonylphenol ethoxylates (NPEOs) are extensively used as surfactants in industrial products (see Chap. 1). NPEOs are a mixture of polyethoxylated mono-alkylphenols, predominantly para-substituted, and are used in the manufacturing of paints, detergents, inks, and pesticides [435, 446]. Surfactants are common water pollutants because of their use in aqueous solutions, which are discharged into the environment in the form of wastewater from treatment plants or sludge stored in landfills. Degradation products of alkylphenol polyethoxylates, i. e., nonylphenol (NP), have the potential to be bioaccumulated, thereby becoming toxic to aquatic [447] and soil microorganisms [435,448]. 

Figure 8. Landfill Degradation of Plastic Films. Control samples on left, experimental samples on right, before (top) and after (bottom 10 months in a UK landfill at 2 meters depth.

The original chemical is therefore either converted into another chemical substance or into products containing the chemical. These products ultimately require disposal. This may be accomplished, for example, by landfilling, degradation, incineration, or as in the case of solvents, they may escape into the atmosphere. 

LLDPE can be disposed of by landfill or incineration. In landfill, the material is completely inert, degrades very slowly, does not produce gas, and does not leach any pollutants into ground water. When incinerated in commercial or municipal faciHties, LLDPE produces a large amount of heat (the same as heating fuel) and should constitute less than 10% of the total trash. 

It is also not tme that vinyl plastics decompose in landfills and give off vinyl chloride monomer, because like all plastics, vinyl is an extremely stable landfill material. It resists chemical attack and degradation, and is so resistant to the conditions present in landfills that it is often used to make landfill liners. On those occasions when vinyl chloride monomer is detected in landfills, it typically can be traced to the presence of other chemicals and solvents. 

In Europe, interest has centered particularly on polyhydroxybutyrate, which can be made into films for packaging as well as into molded items. The polymer degrades within 4 weeks in landfills, both by ester hydrolysis and by an ElcB elimination reaction of the oxygen atom p to the carbonyl group. The use of polyhydroxybutyrate is limited at present by its cost—about four times that of polypropylene. 

Another study (Mersiowsky et al., 1999) also undertook laboratory-scale landfill simulations of PVC products, with leachate and landfill gas as well as PVC degradation analysed. It was found that some of the plasticized PVC products exhibited a partial loss of additives into the leachate. Furthermore, Mersiowsky et al. (2000) also monitored a number of actual landfill... 

Some landfills practice leachate recycling in the fill area, where leachate percolates through the waste cell and undergoes further degradation. The treatment process or processes selected will depend to a large extent on the contaminants to be removed.4... 

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