Plastics in solid waste

Standard practice for preparing residual solids obtained after biodegradability standard metiiods for plastics in solid waste for toxicity and compost quality testing... 

Trends in solid waste generation have changed in some important ways over the past four decades. As the table on pages 136-137 shows, the contribution to the total solid waste volume for most constituents stayed about the same between 1960 and 2000 (the last year for which data are available). The two exceptions are metals, whose share of the MSW had dropped from about 12 percent in 1960 to less than 6 percent in 2000, and plastics, which made up only 0.4 percent of all MSW in 1960 and now constitute nearly 11 percent of all such wastes. 

A great proportion of plastics end its lifetime as a part of the overall solid waste stream where they represent roughly 10 wt%. The typical distribution of plastics in household wastes is shown in Figure 3.1 [3]. The main components are polyolefins low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE) and polypropylene (PP), accounting for about 67% of the total amount of plastic wastes. Other important components in plastic wastes are polystyrene (PS), poly (vinyl chloride) (PVC) and poly (ethylene terephthalate) (PET). 

Although electrostatic separation (static or high intensity) has not been applied widely in solid waste treatment at the industrial level, it is expected to be of wider use in the future in certain sectors of applications. This separation has been successfully applied to separate plastics from paper, plastics from each other, shredded copper wires from their plastic insulation, glass from plastic, nonferrous metals from plastic, or glass, for example. 

Thayer A (1990) Degradable plastics generate contreversy in solid waste issues. Chemical and Engineering News 68 7-24... 

In general, the empirical test methods developed over the years for traditional fossil friels (coal, oil and natural gas) are not applicable to waste materials because they have been developed to match the expected impurities in the fossil fiiels rather than those that may be present in the waste. Assessment is further complicated by the diflflculty of obtaining a representative and reliable sample of the waste for testing. The problem is acute in solid wastes such as domestic refuse, where considerable variations in consistency can occur. Sampling of other solid wastes such as plastic offcuts (from a particular source) or straw, are likely to be more reliable. Ultimately it will be necessary for the operator to determine optimum operating conditions in the light of empirical experience as described in Chapter 17. 

It is now January 1993, and the public is perceiving that the United States is burying itself in solid waste materials. ConAgra, Inc., has approached DuPont with a proposal for a joint venture to produce lactic acid for conversion to biodegradable polylactide plastics to be used in packaging and other markets that might help to alleviate the solid waste problem. 

Of the 200 million tons of municipal solid waste collected in the United States in 1993 (1), 22% was recycled while 62% was placed in landfills and 16% incinerated (2). Plastics comprised 9.3% of these materials. The number of U.S. residential collection programs increased from 1,000 in 1988 to more than 7,000 involving more than 100 million people in 1993 (2). Approximate 1994 U.S. recycling rates are given in Table 1. 

R. S. Magee, Plastics in Municipal Solid Waste Incineration A Eiterature Study, Hazardous Substance Management Research Center, New Jersey Institute of Technology, Mar. 1989. 

Materials-Recovery Systems Paper, rubber, plastics, textiles, glass, metals, and organic and inorganic materials are the principal recoverable materials contained in industrial solid wastes. 

Applicability Most hazardous waste slurried in water can be mixed directly with cement, and the suspended solids will be incorporated into the rigid matrices of the hardened concrete. This process is especially effective for waste with high levels of toxic metals since at the pH of the cement mixture, most multivalent cations are converted into insoluble hydroxides or carbonates. Metal ions also may be incorporated into the crystalline structure of the cement minerals that form. Materials in the waste (such as sulfides, asbestos, latex and solid plastic wastes) may actually increase the strength and stability of the waste concrete. It is also effective for high-volume, low-toxic, radioactive wastes. 

With new plastics and processing techniques always becoming available, the design challenge becomes easier, even when taking today s solid-waste problem into account. Today s plastics and processes allow designers to incorporate and interrelate all the aspects of success. In products such as electronics, medical devices, transportation controls, and many others where user-friendly design is required, it has to be obvious to all that plastics play an important role. 

Geomembrane These liners chiefly provide impermeable barriers. They can be characterized as (1) solid waste containment hazardous landfill, landfill capping, and sanitary landfill (2) liquid containment canal, chemical/brine pond, earthen dam, fish farm, river/coastal bank, waste-water, and recreation (3) mining, leach pad and tailing ponds and (4) specialties floating reservoir caps, secondary containment, tunnel, erosion, vapor barrier, and water purification. Plastics used include medium to very low density PE, PVC, and chlorosulfonated PE (CSPE). (The Romans used in their land and road constructions what we call geomembrane.)... 

Municipal solid waste incinerators (MSWIs) are a robust treatment method for very different mixed waste types of different origin. The typical MSWI handles waste of a calorific value between 9 and 13 MJ/kg. They are the key technology for the treatment of integral household waste in countries such as Denmark, Sweden, the Netherlands and Germany. Some 7% of this integral household waste consists of plastics. Treatment of... 

Note MPW is Mixed Plastic Waste MSW ca is municipal solid waste and comparable material Typical capacities considered are 50 ktpa to 200 tpa Theoretical potential if most blast furnaces and cement kilns in the EU start to replace regular fossil resources by MPW ... 

Combustion of plastics waste with energy recovery is discussed as one approach to the recycling and waste management of waste plastics. Their role in municipal solid waste combustion is examined, and the importance of refuse derived fuel pellets. Facts supporting the importance of waste to energy projects are reported, and details of some projects currently examining MSW combustion with energy recovery are detailed. 

An Ecoprofile is an assessment of the environmental and resource impacts of a waste disposal process. This paper describes ecoprofiles for six different ways of disposing the plastic fraction in municipal solid waste -two material recycling processes that include separation of the plastic waste, material recycling without separation of the plastic waste, pyrolysis, incineration with heat recovery, and landfill. 17 refs. 

---