What can be done with waste plastic at end of life?

Questions around what to do with waste plastic at end of its life should be given increasing emphasis at the design stage. Engineering Materials takes a closer look at the options available to engineers.

Plastic materials play a major role in providing comfort, quality and safety to modern life. However, given the increase in global population, meeting the future needs of society is an increasing focus for those involved in product development. And, its this concept that is at the foundation of 'Sustainable Development'.

The term can be described as the development of commercial and industrial products that meet the needs of the present generation, without compromising the ability of future generations in meeting theirs.

Key factors include the need for design innovation, a rethinking of assumptions about the product lifecycle and reducing a products environmental impact.

Designing for end-of-life is an example that incorporates a need for easy disassembly. This, it is hoped, will lead to greater reuse of materials and make the recycling of products easier.

Another approach includes using recycled materials where possible, minimising the carbon footprint of products, and utilising more energy-efficient processes.
Here, embedded energy during production, material waste in products and overall packaging can be minimised.

The design life of a plastic component or product is defined as the period of time it's expected to work within specified parameters. After this, the product becomes waste. This can, however, represent a valuable resource.

Plastic waste comes from packaging, construction, agriculture, electrical components and automotive industries, among others. In the automotive sector, for example, demands for better fuel economy and lower emissions means manufacturers are incorporating increasing amounts of lightweight and non-metallic materials into vehicles. This approach has been heavily influenced by European legislation including the European Directive on End-of-Life Vehicles (ELV).

The main objectives of this Directive is making vehicle dismantling and recycling easier and more environmentally friendly by implementing clear and quantifiable targets around reuse, recycling and recovery of a vehicles materials. It also serves to encourage manufacturers to consider a design-for-disassembly imperative on any future vehicles.

This general philosophy is reflected in other European legislation relating to end-of-life recovery, for example, the Waste Electrical and Electronic Equipment (WEEE) directive. This places more responsibility for end-of-life with the producer of goods, incentivising end-of-life as an ever important factor to consider during product conception. Hence, end-of-life management is an increasing priority for designers, manufacturers, recyclers and Governments.

It's meant waste management targets and strategies have become key political issues, reflected by the high level of investment in both demonstrating and integrating existing technologies, and the fundamental research and development into new ideas.

Good practice for design-for-disassembly includes a reduction in the number of parts, a reduction in the number of different plastics used and clear labelling of different plastics with an identification symbol, a reduction in the number of assembly stages, using reversible fastenings and the elimination of adhesives.

Another approach being used to maximise the value of plastics at end-of-life is designing products specifically for reuse using the relatively new but little-used concept of re-manufacture.

A re-manufacturing system collects end-of-life products, returns them to their original condition, and then sell them at a similar price to the original. This results in the extension of a product's life and promotes reuse.

A further approach is source reduction, often called waste prevention. This can be considered as an activity that minimises the amount of material in a product and its packaging before it enters the municipal solid waste management system. Source reduction is gaining much more attention as an important conservation tactic and solid waste management option.

Cradle-to-cradle design
The lifecycle of a plastic product encompasses every step from material extraction and processing through to design and manufacture, consumer use (and then potential reuse) in the so-called 'cradle-to-cradle' lifecycle.

Across all lifecycle stages, design decisions influence the resulting cost and environmental impact of a product, but no more than at end-of-life where products or portions of products may be reused, serviced, re-manufactured, or recycled. These recovery strategies remove some burden from the associated lifecycle cost and reduce environmental impact by eliminating the need to use virgin materials and reproduce components on future products.

Assessing the impact
Lifecycle assessment (LCA) is a technique that most are now familar with; the analysis of potential environmental impacts associated with a product, process or service. The ISO 14040:2006 standard enables manufacturers and suppliers to demonstrate they are acting responsibly towards the environment from the design phase through to consumer use, and finally the disposal at the end-of-life.

Consideration of design-for-the-environment is one of the principle uses of LCA. It is used to improve environmental performance from the first stages of product development, using impact indicators in categories affecting ecosystems, human health and natural resources. By using this technique product designers are able to design better overall products, rather than just some physical components that take into account regulatory initiatives on issues covering producer responsibility.

When plastic recycling is required, sustainable development concepts should aim to achieve minimal end-of-life treatment costs against maximum environmental recovery. This requires all relevant technical, economic and environmental aspects to be addressed.

Three main areas can be considered with feedstock recycling the first. This is where plastics are turned back into basic chemicals. This is a potential option for difficult to recycle plastics as it allows them to be turned into valuable chemical building blocks.

More common, however, is mechanical recycling. This involves the recovery of materials from waste while maintaining the polymers' molecular structure, which leads to the reprocessing of materials into new products.

Least favoured is energy recovery. This is the recovery of energy from waste plastic through incineration.

For progress towards product sustainability, it is essential to remember that any manufactured product is the result of a complex chain of material and energy flows that are linked into a specific system that encompasses all sorts of resource and environmental burdens in various stages of the products lifecycle.
Consequently, design-for-end-of-life with respect to plastic product developments is an important consideration for the designer today, and this goes hand-in-hand with a "cradle-to-cradle" approach, and not cradle-to-grave.

This article is authored by Michael Lock, a principal consultant at Smithers Rapra, a specialist material selection, failure diagnosis and product testing consultancy.

Justin Cunningham

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The waste plastic can be perfectly used by melting it and by using it in making good quality of roads in such a way we can make good use of plastic and can save our environment from pollution...... Thnxxxx

Comment Kiran gahane, 18/12/2016

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