Life-cycle assessment
A A 'cradle-to-grave' analysis of the impact of a manufactured product on the environment. Also known as a life-cycle analysis. or LCA is a 'cradle to grave' analysis of the impact of a manufactured product on the The immediate surroundings in which people live, or the natural world such as the land, air or water.. There are many detailed stages but the main ones are:
- extracting and processing the Basic material that goods are made from such as crops, metals, wood and animal products such as wool and leather. needed
- manufacturing the product and its packaging
- using the product during its lifetime
- 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 The capacity of a system to do work or the quantity required for mechanical work to take place. Measured in joules (J). For example, a man transfers 100 J of energy when moving a wheelbarrow., 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 The outer layer of the Earth on top of the mantle., The layers of gases that surround the Earth. The important gases in the atmosphere are nitrogen, oxygen and carbon dioxide. or oceans, or are due to living Living entity, eg animals, plants or microorganisms.. Obtaining these materials has an impact on the environment, including:
- using up limited A resource that is no longer being made or which is made extremely slowly, such as crude oil and metal ores. such as A rock containing enough quantities of a mineral for extraction to be possible. and Mixture of hydrocarbons, mainly alkanes, formed over millions of years from the remains of ancient dead marine organisms.
- damaging A place where plants, animals and microorganisms live. through The removal of rocks from the land., When natural resources are extracted from the ground., or felling trees
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 of 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:
- using up land for Places where refuse is buried underground.
- whether any or all of the product can be Used materials that have been reprocessed to make new materials. or reused
Question
The table shows some data about the energy needed in the lifetime of a pillow case.
| Life cycle stage | Lifetime energy use (%) |
| Raw materials | 10 |
| Manufacture | 15 |
| Use | 70 |
| Disposal | 5 |
| Life cycle stage | Raw materials |
|---|---|
| Lifetime energy use (%) | 10 |
| Life cycle stage | Manufacture |
|---|---|
| Lifetime energy use (%) | 15 |
| Life cycle stage | Use |
|---|---|
| Lifetime energy use (%) | 70 |
| Life cycle stage | Disposal |
|---|---|
| Lifetime energy use (%) | 5 |
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 bags | Paper carrier bags |
| Raw materials | Crude 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. |
| Manufacture | Cheaper to make large quantities of bags from plastic. | More expensive to make bags from paper because the handles must be glued on. |
| Use | Lower 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. |
| Disposal | Can 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. |
| Life cycle stage | Raw materials |
|---|---|
| Plastic carrier bags | Crude oil is a finite resource; fractional distillation, cracking and polymerisation all require a lot of energy. |
| Paper carrier bags | 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. |
| Life cycle stage | Manufacture |
|---|---|
| Plastic carrier bags | Cheaper to make large quantities of bags from plastic. |
| Paper carrier bags | More expensive to make bags from paper because the handles must be glued on. |
| Life cycle stage | Use |
|---|---|
| Plastic carrier bags | Lower impact on the environment because plastic bags are usually stronger so they can be reused many times. |
| Paper carrier bags | Relatively short lifetime; can only be reused a limited number of times. |
| Life cycle stage | Disposal |
|---|---|
| Plastic carrier bags | Can sometimes be collected and recycled; if disposed of as litter, they do not biodegrade; in landfill, may take decades or centuries to degrade. |
| Paper carrier bags | 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 is unfairness, for example, in a survey or a question. A biased die may be loaded to favour one particular number.. 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.