3.12 Re-use Materials at End of Life

Normally design engineers only consider the life of their product up to its use. Some will consider maintenance and servicing during its life, but most assume their responsibility will stop once the product has finished its useful life time. To reduce waste and the energy required in building a new product, it is possible to design certain components of a machine so they can be used for another purpose, or in fact the whole product can be reused.

Examples of this include:

1. Shipping containers re-used as lock-ups for storage

2. Car dismantle companies breaking up old cars to re-use components

3. Ship breaking in India – panels are oxyacetylene torched into segments and re-rolled into sheets

In the case of concrete, if moulds were standardised (like lego bricks), then once the structure was de-constructed, the individual brick could be re-used for other applications. The energy to transport the old piece of concrete would be much less than that to make new concrete from scratch.

For plastic, new plastic products are cheap, so there is often little motivation for reusing plastic at end of life, so it is just thrown away. However, industrial packaging is a big contributor of waste and emissions in the plastics game; there is scope here for large savings by designing packaging that can be re-used. Again there is little financial incentive for companies to do this so it's unlikely this will happen. Unfortunately plastic is often used in low value applications because it is cheap and versatile. This means there are few options for re-use or life extension.

One way of saving energy and waste can be to divert manufacturing scrap before it is sent to be melted down for recycling. Manufacturing scrap can come from yield losses as described above, over ordering, or defects. An example of this can be found in the sheet metal business. “Blanking skeletons” are the sheets left over that have had shapes cut out of them. Normally they are cut up and sent for recycling, but some companies take the blanking sheets and cut smaller shapes out of what's left – reducing the energy used in recycling and producing components out of what would have been thrown away. Another example is extruding aluminium swarf into new sheets of aluminium for reuse.

In the aerospace industry, where reducing component weight is essential, 90% of the aluminium is cut away from a big block and ends up as swarf. However, these two examples are the exception rather than the norm. Currently most manufacturing scrap is sent straight for recycling due to lack of awareness, the current design of the waste handling systems and alloy mixing in waste streams which tend to inhibit efforts to divert manufacturing scrap from recycling.

Design features to increase re-use of components at the end of their lives include:

Design to be adaptable

• standardised part spacing and connections
• speciaised parts only at exterior locations (easy to remove)
• Anticipate possible future needs and design for upgrades

 

Design for easy repair and deconstruction

• avoid mixed materials and coatings
• enable easy and quick part replacment or separation
• develop deconstruction plan