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This lesson covers the carbon footprint of products and manufacturing processes, as required by AQA GCSE D&T (8552), Section 3.2.3. Understanding carbon footprint is essential for making sustainable design decisions and is a topic that appears frequently in the exam.
A carbon footprint is the total amount of greenhouse gases (GHGs) produced directly and indirectly by a product, activity, or organisation, expressed as an equivalent amount of carbon dioxide (CO2e — "CO2 equivalent").
Greenhouse gases include:
A product's carbon footprint is not just about manufacturing. It covers the entire life cycle from raw material extraction to disposal.
| Life Cycle Stage | Carbon Sources | Typical Contribution |
|---|---|---|
| Raw material extraction | Mining, drilling, logging, farming; energy for extraction machinery | 10-40% depending on material |
| Processing and manufacturing | Smelting, refining, polymerisation, moulding, machining; factory energy use | 20-50% |
| Transport | Shipping raw materials and finished products by sea, road, rail, or air | 5-15% |
| Use phase | Energy consumed by the product during its lifetime (e.g. electricity for appliances) | 0-70% (highly variable) |
| End of life | Landfill (methane from decomposition), incineration (CO2), recycling (energy for reprocessing) | 2-10% |
For passive products (furniture, packaging, clothing), most of the carbon footprint is in extraction, processing, and manufacturing. For active products (appliances, electronics, vehicles), the use phase often dominates — a washing machine may produce 10 times more CO2 during its years of use than during its manufacture.
AQA Exam Tip: If asked about the carbon footprint of a product, consider ALL stages of the life cycle, not just manufacturing. The examiner wants to see that you understand the concept of "embodied carbon" (in the materials and manufacture) and "operational carbon" (during use). For a kettle, the electricity used to boil water over its lifetime produces far more CO2 than making the kettle itself.
Different materials have very different carbon footprints per kilogram produced. These values are known as embodied carbon.
| Material | Embodied Carbon (kg CO2e per kg) | Key Reason |
|---|---|---|
| Aluminium (primary) | 8-12 | Extremely energy-intensive smelting (electrolysis) |
| Aluminium (recycled) | 0.5-1.0 | 95% less energy than primary production |
| Steel (primary) | 1.5-2.5 | Blast furnace uses coke (carbon) to reduce iron ore |
| Steel (recycled) | 0.4-0.7 | Electric arc furnace uses much less energy |
| Concrete | 0.1-0.2 | Low per kg, but used in enormous quantities globally |
| Copper | 3-5 | Energy-intensive mining and smelting |
| Softwood timber | Negative to 0.5 | Trees absorb CO2 while growing; processing uses some energy |
| HDPE (polymer) | 1.5-2.0 | Derived from oil; energy for polymerisation |
| PLA (bioplastic) | 0.5-1.5 | Plant-derived; lower than petroleum-based polymers |
| Cotton fabric | 5-8 | Water-intensive farming, fertilisers, processing |
| Glass | 0.5-1.0 | High melting temperature requires significant energy |
Recycled materials almost always have a dramatically lower carbon footprint than primary (virgin) materials. This is one of the strongest arguments for designing products that are easy to recycle.
Different manufacturing processes have different energy requirements and therefore different carbon footprints.
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