catalysts - catalysts

Recycling Metals

Steel

Steel is the world's most recycled material. In 2001 world production was about 850 million tonnes of steel. Almost 450 million tonnes of this was recycled scrap.

picture: steel cans are 25% recycled material

Steel in the UK is made from iron using either the Basic Oxygen Steel process (BOS) or the Electric Arc process. BOS-produced steel contains about 18% scrap added to freshly produced iron, but the Electric Arc process uses 100% scrap.

Aluminium

There is no loss of quality when aluminium is melted and re-cast, but the energy required is 95% less than for newly produced aluminium. Of the 900 thousand tonnes produced annually in the UK, 43% is made from recycled metal. The only obstacle to higher levels of recycling is the problem of effective collection and recovery of aluminium products.

graph: 42% of aluminium cans are recycled

Sources of Scrap

"New" scrap is obtained as off-cuts from the manufacture of aluminium ingots and products. This is 100% recycled. Old scrap is recovered from consumer products, and currently 63% of this is recycled.

One of the major aluminium producers, ALCAN, has invested heavily in developing recycling plants specifically to deal with aluminium cans used for drinks. This is significant because in the UK alone, over five billion cans are consumed each year. The proportion recycled is just over 40%, but is increasing as more collection schemes are introduced.

For a virtual tour of the ALCAN site visit
www.aluminium canrecycling.co.uk

Scrap Sources

Manufacturing scrap with known composition accounts for a significant proportion. Recovered steel from cars and other consumer products is also used, but as composition may vary, steps must be taken to maintain the quality of the steel.
Steel cans, increasingly being recovered by kerb-side recycling schemes, present a problem as they are internally coated with tin. After shredding and washing to remove labels and food residues, the layer of tin is dissolved using sodium hydroxide.