by Jurgen Halbekath

Public awareness of environmental problems, including those connected with the disposal of domestic waste, is steadily increasing. It is not the total amount of refuse in absolute terms that is most alarming, but what it consists of: 50% of all waste from private households and small businesses consists of packaging material.

At first glance the proportion of plastics seems relatively modest in terms of weight: plastics account for only about 5% of the roughly 30 million tons of domestic waste collected each year in the Federal Republic of Germany. But that 5% by weight adds up to 20% of the volume, most of which (75%) is again packaging waste.

Good business for incinerator operators

It is no easy matter to dispose of plastic waste properly. With its various pigments and the diverse additives used to alter its material properties, it contributes considerable amounts of heavy metals to domestic waste. In landfills, where two thirds of all domestic waste is still disposed of in the Federal Republic of Germany, plastics take up a lot of room and resist decomposition over long periods of time.

Because of their high calorific values plastics are gladly accepted at incineration plants for domestic waste. The fact is that approximately one-fifth of the original production energy can be recovered in the form of heat. However, depending on the type of plastic and the incineration temperature, the combustion process might result in uncontrollable reactions that lead to the formation of highly toxic chlorinated hydrocarbons, e.g. dioxin, the infamous Seveso poison.

Other processes designed to recover raw materials (pyrolysis, hydrolysis) are still technically immature and are themselves major sources of pollution. Pyrolysis releases chlorine and PCB, while hydrolysis causes serious pollution by effluents.

It would therefore be desirable to prevent the generation of plastic waste altogether, particularly in the form of packaging material. Unfortunately, the opposite is the case: the proponents of plastics are projecting that the next decade will bring about more than twofold increase in plastics consumption for packaging purposes. As in the case of glass and paper since the 1970s, recycling is being propagated as a strategy with which to fight the resultant mountains of plastic waste.

More sorting needed

In principle, many plastics materials can be re-used; in particular thermoplastics such as polyethylene, polypropylene, polystyrene and PVC, which can be melted down and reshaped several times in succession. In fact this is precisely what is done with most industrial waste.

None the less, the recycling of household plastics involves major problems, e.g. the general lack of purity of materials. For example, more than 60 different kinds of plastics are used for making packaging materials, which often comprise several different plastics or a combination of plastic and other materials. The main problem here is that melting down even two different thermoplastics together is barely feasible. So it is obvious that the uncontrolled mixing of different kinds of plastics can only result in inferior material properties. Contamination with residue from the packaged product or other packaging material (paper, aluminium) is also a problem (particularly in the case of packaged food).

Even elaborate sorting and cleaning processes cannot solve those problems satisfactorily. Consequently, most recycled plastic is of inferior quality and is only suitable for products with low material standards (flowerpots, paving setts, etc.).

New approaches

The Berlin plastics recycling test aims to implement several new approaches at once.

To begin with, the scope of the experiment is essentially limited to a single kind of plastic: polyethylene (used in 66% of all plastic packages).

Only specific, labelled packages are to be collected: PE bottles for fabric softeners and liquid detergents, and PE paint buckets. Limiting the material to precisely defined products and labelling them with a special logo guarantees homogeneity and makes it possible to employ untrained personnel for quality control purposes. Additionally, the relatively large size of the bottles and buckets reduces the weightspecific salvage effort. Last but not least, limiting the range of items recovered to certain used products also keeps the contamination spectrum within controllable limits.

What really makes this recycling test different, though, is that no cost-intensive processes (screening, washing and/or drying) are used to remove the contaminants. Instead, they serve as fillers or additives in the secondary product. "It is therefore possible to selectively improve product quality by retaining or even supplementing various materials in the used plastic. Raising the quality of secondary plastics means improving their mechanical, electrical, chemical and other properties through the presence and/or addition of polymeric and/or nonpolymeric aggregates that stabilize or even upgrade the value of the reprocessed polymer, as compared to its original value as a used plastic." (H. Bonau, "Gezielte Aufwertung beim Wiederverwerten von Kunststoffen", in Verwertungskonzepte, [2], page 121).

The main objective of the test is to develop a complex facility in which the preparation and processing of discarded plastics can be integrated.

The material should only be rough-crushed and cleaned to remove dirt, metal, etc. Then, depending on the design concept, the old material, together with any residual paint, detergent or the like and, as the case may be, colouring and quality-enhancing additives, will be melted down, mixed and dehydrated in a hot-air screw conveyor.

Any moisture contained in the batch should evaporate as a result of the high melting temperature. while the system's thermal energy is conserved by heat exchangers. Then the melt is extruded for further processing. A computer-controlled light-optical microscope is provided for continuous quality control. If the contamination of the plastic fluctuates beyond a certain level of tolerance, the batch in question can be removed and reprocessed - the aim being to obtain a closely defined grade of secondary plastic with a set of properties specific to certain applications. The integrated plastic preparation and processing system is still at the development stage. Test specimens from the collected plastic materials are currently being developed in order to ascertain the best material properties achievable for the given contamination levels.

The selective upgrading of used plastics has, however, at least in principle, already been successfully implemented in a test conducted at the Technical University of Berlin: a high-quality, fully reproducible secondary raw material suitable for use as a wheel-well liner was recovered from the polypropylene containers of lead batteries.

However, the extent to which the same principle could also be successfully applied to other domestic waste plastics, with their diversity of quality, composition and contamination, is at least questionable. Aware of such problems, the test team is calling for a reduction in the number of different kinds of plastic (and compound materials) in use.

Environmental policy problems

Notwithstanding technical matters and all prerequisites for broadening the scale of plastics recycling the Berlin test in question is open to criticism from the environmental standpoint.

Genuine pollution abatement can only be achieved by preventive measures that give due consideration to all direct and indirect environmental consequences arising in connection with certain products. Recycling, however, is oriented exclusively along the lines of waste disposal and can yield, at best, only short term environmental relief by postponing the production of refuse to some later date. Recycling also obscures the need for structural, political measures, e.g. taxation of particularly harmful products and over elaborate packaging. On the contrary, it provides an argument for even less restraint on increases in production and hence ultimately promotes yet more pollution:

Even the selection of products to be included in the Berlin test shows quite clearly how far that project is from being part of a comprehensive waste-prevention concept. Instead of propagating products that are known to be of low-level environmental impact, the recycling test effectively upgrades such admittedly superfluous and ecologically detrimental products as softeners and liquid detergents by attesting to their "recyclability". If the practice of plastics recycling actually does expand as planned, the same effect will spread to numerous other products as welI - thus inadvertently torpedoing efforts to avoid environmental pollution.

Consider for example the recycling of glass, which began in the early 1970s. The recovery and reutiIization of one-way bottles did lower the percentage of glass in domestic waste. But on the other hand, the amount of household waste augmented due to the increase of other throw-away packaging materials. Propagating recycling systems was taken as a sufficient strategy against the increase of household waste and thus the promotion of the existing returnable bottle system was neglected. For that reason and due to material-collection limitations (1984: 26% of disposable glass consumption, the amount of household refuse requiring disposal actually increased [2].

The fact that the recycling of non returnable packages has already weakened the existing refillable packaging system (and can be expected to continue doing so in the future) is aggravated by the circumstance that today's returnable bottles are refilled 40 times and are therefore recognized as the most environmentalIy - friendIy packages at all. Consequently, the intensified use of non-returnable glass would increase not only the volume of domestic waste, but also the environmental burden resulting from the glass production process.

Similarly, the recycling of plastic packages would ultimately also lead to more plastic rubbish.

Indeed, even the Arbeitspemeinschaft Kunststoff-Recycling-Test comes to the same conclusion. They expect the amount of plastic packages to increase from roughly 1.7 million tons in 1989 to approximately 4.8 million tons in the year 2000. Assuming that a full two million tons of old plastic could be recycled each year, 2.8 million tons would still have to be disposed of; this would result in an additional 1 million tons of throw-away packages more to be disposed of than at present without recycling. For the year 2000, the Work Group anticipates a nearly twofold increase in the incidence of plastic waste per se, from 8.5 million tons (present consumption without recycling) to 15.5 million tons (forecast consumption with recycling included) - this despite, or perhaps because of, the recycling test.

For packaging purposes, polyethylene and polypropylene are by far the most frequently used plastics; of the 1.48 million tons of plastics consumed by the German packaging industry in 1984, PE and PP accounted for 66% and 10% respectively, a total of 1.124 million tons. By contrast, they accounted for only 26% of the plastics used in the production of other goods (0.8 million tons of PE and 3.0 million tons of PP)

So for a situation characterized by the comprehensive recycling of spent PE packages for use in the production of long-lived products, there is already an oversupply of polyolefines. To increase the use of these it would first be necessary to demonstrate that they are of higher quality than the plastics used at present. The question arises as to how far the recycling of plastic waste is and will remain solely confined to the packaging sector.

Priority for multi-trip,systems

Instead of investing research efforts and funds in the development of recycling processes that would ultimately promote the increased, careless production of plastic waste, existing reusable packaging should be protected, further developed and expanded into new areas. Appropriate environmental measures should be taken to help achieve this. As long as we keep hoping that preventive protection measures will eventually be engendered by the economic interests of the industry, it will be practically impossible to get fully developed, genuinely beneficial innovations implemented.

References

[1] Arbeitsgemeinschaft Verpackung und Umwelt e. V. (ed.): Verwertungskonzepte für gebrauchte Kunststoff-Verpakkungen. Bonn 1988

[2] Brahms, E.; Eder, G.; Greiner, B.: Papier- Kunststoff- Verpackungen, TU Berlin 1988.

[3] Institut für ökologisches Recycling e. V. (ed.): Abfall vermeiden. Frankfurt/M.1989

[4] Umweltbundesamt (ed.): Verpackungen fur Getränke 4. Fortschreibung. Berlin 1985 K

Abstract

While the percentage of plastic materials in household waste may be relatively low in terms of weight, their share of the volume is much higher. Most plastic waste consists of packaging material, the disposal of which can be quite problematic. In collaboration with the industry-affiliated Arbeitsgemeinschaft Verpackung und Umwelt e. V. (Work Group on Packaging and Environment), the Kunststofftechnikam (Institute for Plastics Research) at the Technical University of Berlin is conducting a plastics recycling test. Irrespective of how the experiment turns out technically it will still involve an inherent risk as regards environmental policy, because isolated waste recycling measures obscure the need for comprehensive preventive environmental protection including measures aimed at avoiding generation of waste in the first place.

Résumé

La part des plastiques dans les ordures ménagères est, de par son poids, relativement faible, mais non de par son volume. La plus grande partie des déchets en plastique provient des emballages. Leur élimination est problématique. L' Université Technique de Berlin, en collaboration avec le groupe de travail charge de l 'étude des emballages et de l'environnement (Arbeitsgemeinschaft Verpackung und Umwelt e. V.), procede actuellement un à test de recyclage des matiéres plastiques. Indépendamment du résultat eventuellement positif techniquement de ce test, cet état de fait comporte un risque en matière de politique de l'environnement. Des mesures isolees pour le recyclage de ce genre de déchets occultent la nécessité d'une vaste politique préventive en matière de protection de l'environnement qui consiste aussi à éviter la production de déchets.

Extracto

El porcentaje de plásticos en las basuras domiciliarias es relativamente reducido, en cuanto a su peso, pero su volumen es considerablemente superior. La mayor parte de los desechos de plástico procede del sector del envasado. Su eliminacion es problematica. El Departamento Técnico de P/asticos de la Universidad Técnica de Berlin esta realizando un test de reciclaje de plásticos en colaboración con el grupo de trabajo de en vasado y medio ambiente "Verpakkung und Umwelt e. V. ", cercano a la industria. Independientemente de que este ensayo tenga o no éxito desde el punto de vista técnico, no deja de encerrar un peligro de politica de medio ambiente. Las medidas aisladas pare el aprovechamiento de desechos materiales encubren la necesidad de una protección del medio ambiente complete y preventiva, que incluye la evitación de los mismos.