Life cycle assessment: extracting and processing raw materials

The idea

Every product begins with raw materials taken from the Earth, and this stage of a life cycle assessment (LCA) covers getting them out and turning them into something usable. Extraction includes quarrying limestone, mining metal ores, drilling for crude oil and felling trees. Processing then refines these: crushing and heating limestone for cement, extracting metal from ore by reduction or electrolysis, and fractional distillation plus cracking for crude oil. Both steps use energy, often from burning fossil fuels, and can release pollutants, use water and disturb habitats. For example, making aluminium needs bauxite ore, and electrolysis of purified alumina consumes large amounts of electricity. In an LCA you weigh these impacts against the benefits of the finished material, and compare alternatives fairly by using the same functional unit, such as one kilogram of material.

What earns the marks

• Identifies extraction as obtaining raw materials from the Earth, such as quarrying limestone, mining metal ores, drilling crude oil or harvesting timber.
• Describes processing as converting extracted material into a usable form, for example crushing and heating limestone, reducing metal ores or fractionally distilling crude oil.
• Recognises that extraction and processing need energy, commonly from burning fossil fuels, and so contribute to resource use and emissions.
• Links these stages to specific environmental effects such as habitat destruction, land use, water use, noise, dust or release of carbon dioxide and sulfur dioxide.
• Uses the idea of a functional unit, such as one kilogram of material, so that comparisons between products are fair.
• Places extraction and processing as the first stages of a life cycle assessment, before manufacture, transport, use and disposal.
• Evaluates trade-offs, for example a material that is energy-intensive to process but light and long-lasting in use.

Common mistakes and how to put them right

• Treating extraction and processing as the same stage.

  Put it right: Extraction removes material from nature, while processing changes it chemically or physically into a usable substance.

• Assuming all raw materials are renewable.

  Put it right: Metal ores and fossil fuels are finite, whereas timber can be regrown if managed sustainably.

• Ignoring the energy and pollution from processing and focusing only on the digging or drilling, which understates the impact of this stage.

Exam tips

• Name a specific material and its extraction method, then state one processing step, to show understanding rather than generalising.
• When comparing materials, state the functional unit you are using so the comparison is valid.
• Use comparative language such as 'more energy-intensive than' and support it with a reason, rather than just listing impacts.