Sustainability–recycling and reuse
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The average carbon footprint of stainless steel (all grades, all countries) is estimated to be 2.90 kg of CO2 per kg of stainless steel produced, of which 1.92 kg are emissions from raw materials (Cr, Ni, Mo); 0.54 kg from electricity and steam, and 0.44 kg are direct emissions (i.e., by the stainless steel plant). Note that stainless steel produced in countries that use cleaner sources of electricity (such as France, which uses nuclear energy) will have a lower carbon footprint. Ferritics without Ni will have a lower CO2 footprint than austenitics with 8% Ni or more.
Carbon footprint must not be the only sustainability-related factor for deciding the choice of materials:
- over any product life, maintenance, repairs or early end of life (planned obsolescence) can increase its overall footprint far beyond initial material differences. In addition, loss of service (typically for bridges) may induce large hidden costs, such as queues, wasted fuel, and loss of man-hours.
- how much material is used to provide a given service varies with the performance, particularly the strength level, which allows lighter structures and components.
Stainless steel is 100% recyclable. An average stainless steel object is composed of about 60% recycled material of which approximately 40% originates from end-of-life products, while the remaining 60% comes from manufacturing processes. What prevents a higher recycling content is the availability of stainless steel scrap, in spite of a very high recycling rate. According to the International Resource Panel's Metal Stocks in Society report, the per capita stock of stainless steel in use in society is 80–180 kg in more developed countries and 15 kg in less-developed countries. There is a secondary market that recycles usable scrap for many stainless steel markets. The product is mostly coil, sheet, and blanks. This material is purchased at a less-than-prime price and sold to commercial quality stampers and sheet metal houses. The material may have scratches, pits, and dents but is made to the current specifications.citation needed
Stainless steel cycle
The stainless steel cycle starts with carbon steel scrap, primary metals, and slag.
The next step is the production of hot-rolled and cold-finished steel products in steel mills. Some scrap is produced, which is directly reused in the melting shop.
The manufacturing of components is the third step. Some scrap is produced and enters the recycling loop. Assembly of final goods and their use does not generate any material loss.
The fourth step is the collection of stainless steel for recycling at the end of life of the goods (such as kitchenware, pulp and paper plants, or automotive parts). This is where it is most difficult to get stainless steel to enter the recycling loop, as shown in the table below:
| End-use sector | Results | Use, global average | Estimates | |||||
|---|---|---|---|---|---|---|---|---|
| 2000 | 2005 | Average lifetime (years) |
Coefficient of variation |
To landfill | Collected for recycling | |||
| Total | Of which as stainless steel | Of which as carbon steel | ||||||
| Building and infrastructure | 17% | 18% | 50 | 30% | 8% | 92% | 95% | 5% |
| Transportation (total) | 21% | 18% | 13% | 87% | 85% | 15% | ||
| Of which passenger cars | 17% | 14% | 14 | 15% | ||||
| Of which others | 4% | 4% | 30 | 20% | ||||
| Industrial Machinery | 29% | 26% | 25 | 20% | 8% | 92% | 95% | 5% |
| Household appliances & electronics | 10% | 10% | 15 | 20% | 30% | 70% | 95% | 5% |
| Metal Goods | 23% | 27% | 15 | 25% | 40% | 60% | 80% | 20% |
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