Property Information
Energy Content
Overview
- Energy is used to mine, refine and process materials - this is called the "energy content" of the material. The energy used has environmental implications (global warming, CO2 and other emissions).
- The energy content is just one of the environmental factors (disposal of wastes, final disposal of the product and transportation are others). It is relatively easy to measure and is therefore a simple indicator of "environmental friendliness" of a material.
- Naturally occuring materials such as wood are energy efficient because there are no refining or synthesis costs. Metals tend to have the highest energy contents as most metals are extracted from ores, and need a lot of refining, which uses a lot of energy.
Design issues
- All materials used for products have an environmental impact. This is of growing importance, so it is increasingly common to consider quantities such as energy content. Overall assessment of environmental impact over the whole lifetime of a product is very difficult to do with any certainty.
- Enviromental issues are particularly important in design for one-use products (e.g. packaging, drink containers, nappies) or large volume products which may consume energy in use (e.g. cars, domestic appliances).
- Energy content is closely related to recycling - high energy content materials are particularly attractive to recycle, particularly if the energy used in recycling is much less than is needed to make new material (e.g. aluminium).
Measurement
The energy content of a material is defined as the total energy necessary to make it into a form in which is can be used to manufacture a product. This includes mining, refining or synthesising, and forming it into usable sizes and shapes.
Units & Values
The energy content is given as energy per unit weight, Joules/kg
Precise numerical ranges are not given here for material classes as they are not useful - see material selection charts for individual materials.