Life-cycle assessment

A life-cycle assessment or LCA is a 'cradle to grave' analysis of the impact of a manufactured product on the environment. There are many detailed stages but the main ones are:

  1. extracting and processing the raw materials needed
  2. manufacturing the product and its packaging
  3. using the product during its lifetime
  4. disposing of the product at the end of its useful life

The four main stages

At all stages, an LCA is likely to include information about the use of energy, transport of materials and the release of waste substances into the environment.

1. Raw materials

All the raw materials we need come from the Earth's crust, atmosphere or oceans, or are due to living organisms. Obtaining these materials has an impact on the environment, including:

2. Manufacture

The manufacture of products has an impact on the environment, including:

  • using up land for factories
  • the use of machines and people

3. Use

The impact of a product on the environment during its use depends on the type product. For example, a wooden chair has very little impact, unless it needs cleaning or repair. On the other hand, using a car will have a significant impact.

4. Disposal

The disposal of old products has an impact on the environment, including:

Circular line linking disposal, raw material, manufacture and use in a continuous loop.Four main stages of the life-cycle assessment

The table shows some data about the energy needed in the lifetime of a pillow case.

Life cycle stageLifetime energy use (%)
Raw materials 10
Manufacture 15

Discuss the use of energy during the lifetime of the pillowcase. Describe one way in which the energy use could be significantly reduced.

One quarter of the energy use is associated with making the pillowcase, and very little in disposing of it. The greatest use of energy happens when it is being used, probably because of washing, drying and ironing the pillowcase. Energy use could be reduced by drying it outside and without ironing it, and washing it at a lower temperature.

Comparative LCAs

Comparative LCAs can be used to evaluate which of two alternative products will have a lower negative impact on the environment. For example, we can compare plastic carrier bags and paper carrier bags:

Life cycle stage Plastic carrier bagsPaper carrier bags
Raw materialsCrude oil is a finite resource; fractional distillation, cracking and polymerisation all require a lot of energy.Can be made from recycled paper, or from trees. Making paper from trees requires more energy than recycling paper, but much less than making plastics.
ManufactureCheaper to make large quantities of bags from plastic.More expensive to make bags from paper because the handles must be glued on.
UseLower impact on the environment because plastic bags are usually stronger so they can be reused many times.Relatively short lifetime; can only be reused a limited number of times.
DisposalCan sometimes be collected and recycled; if disposed of as litter, they do not biodegrade; in landfill, may take decades or centuries to degrade.Can be recycled easily; if disposed of in landfill, they biodegrade quickly.

Criticisms of LCAs

It is sometimes easy to work out accurate numerical values for parts of a LCA. For example, we can measure the amount of energy needed to manufacture a product, or the amount of carbon dioxide produced by transporting raw materials. However, some parts of a LCA require judgements, such as the effect of pollutants. This means that completing a LCA is not a totally objective process, and different people might come up with different judgements.

It is important to consider who has completed the LCA and whether they have any bias. For example, if the LCA is completed by the company which is making and selling a product, they might only include some parts of the genuine environmental impact.