3.10 Design for Sustainable Material Use

We have discussed sustainability issues surrounding the major materials used for engineering, how they are used and how much of them we are currently consuming. Also highlighted were some of the environmental problems with the current production of the materials we use for engineering projects. At current consumption rates, it is obvious that at some point we will eventually run out of the natural resources we require for producing materials, the pollution caused by their manufacture and disposal will reach a critical level, and waste levels of used products will reach an unsupportable high.

The rest of the chapter will suggest concepts for sustainable material use. An engineer when working on any project that requires or uses materials should have these implications of material use in mind, and have these tools for sustainable material use ready to be implemented if at all possible.

The following hierarchy for dealing with waste can be applied to material selection and usage:

The waste hierarchy

The waste hierarchy is a management system for waste, which has three key objectives which are embodied in the hierarchy. These are minimising waste produced, making best use of waste that is produced and minimising any immediate or future risk of pollution from waste management practices. We could view the hierarchy as five levels:

• Reduce waste – don’t create waste in the first place.
• Reuse ‘waste’ – use products for a purpose more than one time.
• Recycle waste – reprocess waste materials to be used for new products.
• Recover waste – incinerate waste and recover energy for heat and power generation.
• Dispose of waste – place waste in landfill which is not suitable for recovery, recycling or reuse.

(Source: Open University Open Learn [see reference 6])
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The hierarchy demonstrates measures to reduce the effects of material usage, and the order of the measures is key. Although the above figure is aimed primarily at household waste, the same principals can be applied to industrial waste, and the engineering design process concerning material use.