The properties of metals provide unique benefits and advantage for their recycling. Unlike other recycled materials, such as paper and plastic, metals can be repeatedly recycled without degradation of their properties. Metals from secondary sources are just as good as metals from the primary sources.
Practiced since ancient times, scrap metal recycling embodies the spirit of sustainable development. That is, "development, which meets the requirements of the present without compromising the ability of future generations to fulfill their own needs," as defined by the World Commission on Environment and Development. Recycling widens the efficient use of metals and minerals, reduces pressures on landfills and incinerators, which results in significant major energy savings compared to primary production.
Some of the important categories of scrap metal recycling include -
These recycled metals have found uses in the production of automobiles, structural steel, aluminum siding, and toys. According to experts, every time a ton of steel is recycled, 2500 pounds of iron ore, 1000 pounds of coal and 40 pounds of limestone are preserved.
To promote scrap metal recycling and to further promote the greater awareness of the industry's role in conserving the future through recycling, government in different countries have established industry associations representing companies that process, trade and industrially consume scrap commodities.
Types of Scrap Metals
Scrap metal can be categorized into two types, viz. - ferrous and nonferrous. Scrap iron and steel are referred as ferrous scrap that include - scrap from old cars, steel beams, household appliances, railroad tracks, ships, and food packaging and other containers.
Nonferrous scrap metals include scrap metals other than steel and iron. Some common examples of non-ferrous scrap, include - aluminum (including foil and cans), copper, zinc, lead, nickel, cobalt, titanium, chromium, and precious metals. Although there is less nonferrous scrap than ferrous scrap, it is often financially more worthy. Millions of tonnes of nonferrous scrap metal is recycled by processors and consumed by secondary smelter, refiners, fabricators, ingot makers, foundries, and other industries.
Scrap metal, ferrous as well as nonferrous, can be categorized as either "home scrap" or "purchased scrap."
Home scrap is scrap yielded at the mill, refinery, or foundry, and is usually remelted and used again at the same plant. Home scrap never leaves the plant.
Steel scrap is necessary in the process of making new steel and can be recycled several times without loosing its properties. Due to its magnetic characteristics, the metal is easy to recover even from unsorted waste and residual waste from waste plants.
Aluminum foil, laminates will oxidize in an incinerator and discharge energy similar to coal. Aluminum cans will generally melt releasing some energy and when cooled can be separated from the bottom ash.
Purchased scrap represents the fractions of the metals, which need to be collected before they can be recycled. Large goods, such as vehicles and fridges have historically been collected by scrap metal merchants because of the value of the metal recovered. New legislations concerning the recycling of fridges and of end-of-life vehicles is changing the specific role of the metals recyclers in the collection and processing of these goods, however their importance in recovering the metal components has not changed.
Savings From Recycling
The savings from scrap metal recycling stems from two common processes in primary metal reduction. First, the comminution (particle size reduction) of minerals, often hard rock minerals, is usually essential for subsequent chemical and physical treatment. About 60% of the total energy used in the production of most metals is absorbed when crushing and grinding the ores. Second, primary production is preceded on reducing the metals from their chemically stable oxide or sulfide mineral form, an inherently energy intensive exercise. Thermo chemical reduction (e.g. iron ore in the blast furnace) is typically less demanding than electrolytic reduction however it still needs higher temperatures than secondary smelting.
Electrolytic reduction, which is used for zinc and aluminum, is very energy intensive. To exemplify, energy savings made when metals are produced from secondary sources versus primary sources are - zinc, 60 %; steel, 74%; lead, 76%; copper, 85% and aluminum, 95%.
In addition, the reduction in pollution made from recycling can be significant.
- For aluminum, there is a 79 % material conservation, a 95 % reduction in emissions and a 97 % reduction of effluents through recycling.
- For steel, one sees a 90% savings in virgin materials, an 86% emissions reduction, a 40% effluent reduction, a 76% water pollution reduction and a 97% mining waste reduction through recycling.
- Of course, many of these advantages also transform into significant economic savings for producers.
When a recyclable metallic material makes up part of a stream emitted from an industrial facility, the material is pertained to as "new scrap," expressing that it never comprises part of a final product. Recycling such new scrap within the same facility, or to another facility as a raw material, is a typical example of waste minimization at source, widely recognized as the most efficient technique of pollution prevention. Reprocessing of "old scrap," material, which has come to the end of its beneficial life, diverts this metal from disposal in landfill.
The increasing cost and problems of landfilling, and the degrading grade and increasing complexity of mineral reserves, will persist to tip the scales in favor of increased recycling.
The recycling of metal is primarily market-driven across the world and this will continue to be the case for the foreseeable future. This strength, however, is largely a reflection of continuously increasing metals consumption and waste production. As long as this is the case, and as long as the prices of scrap metal remain high, the recycling rates are expected to see at least a marginal yearly improvement.