Plastics Waste Composition

F. Pinto, P. Costa, 1. Gulyurtlu and I. Cabrita, Pyrolysis of Plastic Wastes. 1. Effect of Plastic Waste Composition on Product Yield, J. Anal. Appl. Pyrol, 51, 39-55 (1999). 

Pinto, F., Costa, R, Gulyurtlu, I., and Cabrita, I. (1999) Pyrolysis of plastic wastes. 1. Effect of plastic waste composition on product yield. Journal of Analytical and Applied Pyrolysis, 51 39-55. 

TABLE 1. An example of typical plastics waste compositions from the packaging refuse... 

The origins and composition of plastics wastes and factors affecting their recycling are discussed. Partieular attention is paid to chemical recycling and incineration, with and without energy recovery, and a number of developments in chemical recycling techniques are examined. 19 refs. 

Additives often form a problem in recycling processes. Material recycling is often not possible or only with a considerable loss of quality. Plastics recycling is notoriously difficult due to the mixed composition of the plastics waste stream. The recycled material can only be used in certain applications that do not demand a pure material. Recycling of the additives themselves is theoretically possible only for metals, but in practice this type of recycling is not feasible. The metals occur only in low concentrations. Recovery from fly ash and bottom ash is possible, but expensive in view of growing scarcity problems it may become a viable options for at least some metals. 

Samples were taken from MSW in district Hai Ba Trung, Hanoi. Waste sources are mainly from households and small street restaurants without separation at source. In this district, waste composition contains high percentage of biowaste which accounts for 55-69%, and plastic and nylon bag are 4-5% and 1.5-2%, respectively [11, 12]. 

Energy production and consumption pose nature into pressure and make the energy sector becomes the largest contributor of greenhouse gas (GHG) emission in Vietnam since 2010, accounting for 67%. Several emission sources of GHG could be found in a waste treatment facilities it came from (1) emission of methane (CH4, GWP 25) at landfill of mixed waste, (2) from emission of fossil carbon dioxide through the combustion of plastics and composites or supported fuels (auxiliary), and (3) from emission of nitrous oxide (NOx) during incineration/ pretreatment process, etc. 

A plastic waste processor (from Carderock Division) has been developed to compress the Navy s plastic wastes into discs, solving the environmental and space problems from 600 kg daily plastic waste (20 m ) per ship. Seaward International Inc and Carderock Division are developing a marine piling (The SeaPile) in structurally reinforced composite with a core made of these discs. 

Table 7.6 (after Neste) displays some calorific properties of plastic wastes compared to coal. The laminates and sandwich composites are handicapped by the low heat value and carbon content. Moreover, the laminates have a high ash content. 

Plastics waste arises at the levels of production, conversion, and consumption. In the first two categories source separation, identification, and recycling, is straightforward. Such simple source separation concepts no longer hold for post-consumer recycling, where entropy is immense plastic products both geographically and functionally are widely spread, more often than not compounded with unknown additives, or mixed, soiled, composite, and difficult to collect at a reasonable cost. 

Two types of approach exist to study the behaviour of plastic mixtures during pyrolysis. On one hand, some authors [46] work on plastic waste mixtures while other authors [47] work on simulated mixed plastic waste prepared with a specific composition. The proportions of the different polymers are based on mean values related to real waste mixtures. 

The detailed analysis of the derived oil/wax and gas products from the pyrolysis of plastics in relation to process conditions and different types of plastic is essential in providing data for the assessment of the feedstock recycling process. In addition, the yields and composition of gases and oils from the pyrolysis of mixed plastic waste are important in assessment of the process and to determine the possibility of any interactions between the plastics during pyrolysis. 

A. M. Cunliffe, N. Jones and P. T. Williams Pyrolysis of composite plastic waste. Environmental Technology, 24, 653-663, (2003). 

Thus, for the development of polymer waste recycling technologies it is helpful to be aware of the chemical composition of the pyrolysis products of those polymers which are typical components of plastic wastes. 

A real plastic waste collected by the German Dual System (DSD) from municipal packaging waste was pyrolyzed in the laboratory plant as well as in the pilot plant. The composition of the mixed plastic wastes is shown in Table 17.4. 

Table 17.4 Different compositions (A and B) of the mixed plastic wastes nsed in wt% collected by the DSD system...

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