Chapter 1
General Aspects

Economic, ecological, and technical aspects of plastic waste handling have been summarized in monographs (1-4).

Plastics have become an indispensable ingredient of human life. They are non-biodegradable polymers mostly containing carbon, hydrogen, and a few other elements such as chlorine, nitrogen, etc. Rapid growth of the world population has led to increased demand for commodity plastics (5).

The total plastics production in the world is shown in Table 1.1.

Table 1.1 Plastics production in the world (6).

A list of acronyms and initials used in the waste management industry has been published (7).

1.1 History of the Literature

The issue of recycling of plastics was not important for scientists before the 1970s. The amount of literature concerning plastics recycling is collected in Table 1.2.

Table 1.2 The literature with plastics recycling in the title of the papers found in Google Scholar in March 2018.

As can be seen from Table 1.2, the boom started in the mid-1980s.

1.2 Amount of Wastes

The plastic wastes produced in the European Union in 2007 was about 52.5 Mt (8, 9). In 2008, 60 Mt were produced in Europe and the global production in 2008 was 245 Mt (10). In 2007 the amount of post-consumer plastic wastes obtained in the EU that year was 24.6 Mt, which is similar to that in 2008 (8, 10).

The total waste generated per year in 2010 in Pakistan was about 31 Mt per. In big Pakistani cities such as Karachi, about 7 to 8 Mt of solid waste is generated. It is estimated that about 6% to 8% of solid waste is post-consumer plastic waste, while only 10% of this amount is recycled (11).

The quantities of recycled poly(vinyl chloride) (PVC) in Europe are shown in Table 1.3.

Table 1.3 Quantities of recycled PVC in Europe (12).

Also, the problems of plastics wastes in other countries have been highlighted, such as, in India (13) and Bangladesh (14, 15).

Consequently, there is a growing social concern related to the management of the plastic wastes, which should proceed according to a hierarchical approach in agreement with the following order: waste minimization, reuse, recycling, energy recovery and landfilling (16).

In 2014, nine countries in Europe reached a recovery ratio of more than 95% of the post-consumer plastic waste (6). The amounts are shown in Table 1.4.

Table 1.4 Plastics recycling in European countries (6).

1.3 Metal Content in Wastes

1.3.1 Waste Poly(ethylene) and Pure High Density Poly(ethylene)

The metal content of both waste poly(ethylene) (PE) and pure high density poly(ethylene) (HDPE) used in a specific study (9) is shown in Table 1.5.

Table 1.5 Metal content of poly(ethylene) samples (9).

In pure HDPE, the total metal content is very low and accounts for less than 0.03%. In contrast, the metal content in waste PE is much higher and accounts for roughly 0.4%. The main metals present are Cu and Ti with a share of 0.162% and 0.151%, respectively (9).

1.4 Analysis Procedures

1.4.1 Fluorescence Labeling

The demand for polymers in combination with their high durability following rather short life phases ensures the flow of plastic waste into landfills (17). Therefore, plastic recycling has become indispensable. In order to produce economically attractive products based on recycled plastics, mono-fractional compositions of waste polymers are required.

However, existing measurement technologies, such as near infrared spectroscopy used in sorting facilities, show limitations with regard to the separation of complex mixtures of plastic flakes, especially when dark and black plastics are part of them. An innovative approach to overcome these obstacles and provide high sorting purities is to label different types of plastics with unique combinations of fluorescence markers, also known as tracers, which can be considered as optical fingerprints. They are incorporated into the virgin plastic resins at ppm levels during the production process and do not affect either the visual appearance nor the structural and mechanical integrity of the materials.

The goal is to realize the practical use of this concept in industrial processes. An industrial applicable spectroscopic measurement system has been designed and implemented that can identify polymer flakes with a size of a few millimeters transported on a conveyor belt in real time based on the emitted fluorescence of incorporated organic markers. In addition to the implementation of the opto-electrical measurement system, a multi-threading software application has been developed and realized which controls the hardware and collects the measured data and finally classifies the data (17).

In recent years, great effort has been expended in the development of the automated identification and sorting methods for post-consumer plastics in the waste streams that are reaching recycling processes (18). The final properties of the recycled materials largely depend on the purity of the plastic residue.

The use of...