From ancient civilisations to present times, metal of many types has often been collected and recycled (especially when it was needed for a new supply of weapons). The Romans for instance used to recycle bronze coins and convert them into statues which had a higher monetary value.
Metals perceived as very valuable have been and continued to be recycled as well, although mainly for profit and less for ecological concerns – for instance gold. One of the early accounts of that can be found in the Bible, when in the absence of Moses, Aaron gathered gold items (such as jewellery) and ordered their melting so a Golden Calf could be made for the people to worship. In our times, the hunt for gold is carried out by specialised gold scrapping companies.
A plethora of such companies emerged after the start of the global recession, offering to buy people’s used gold. Overall, whatever their use, valuable metals will undergo a continuous recycling process and will never be wasted.
Metals are a favoured category of materials for re-processing as basically any kind of cast-off metal can be used again, with a resulting recycled variation of very high quality.
However, some are used and recycled more widely than others, on criteria such as availability, processing costs, physical and chemical properties, demand by certain industries and so forth.
The food and drink industry customarily uses aluminium and steel, aluminium for drink cans and steel for food cans, although combinations and variations do occur.
When intending to recycle daily use products, one can usually find specifications on the label regarding the type of metal the products are made from.
One can also use a magnet to determine whether a can is made from steel or aluminium, as unlike steel, aluminium is not magnetic. Like other recyclables, metal must be free of contaminants, which means emptying drink cans completely and rinsing food cans under the tap before placing them in a recycling bin.
This complex operation, which involves many steps, always starts with the collection phase, which involves collection sites, council initiatives and other schemes. The metal is then sorted (as the general population deposits various metallic objects into a single container) and weighed. This involves a series of participants such local authorities, businesses, independent organisations and so forth. Sorting is either done manually, with the aid of magnets or more sophisticated methods. In order to facilitate transportation to the recycling units, large pieces of metal are often sheered (cut into smaller pieces), compacted or shredded.
Due to its properties (a very lightweight yet sturdy, reliable material), aluminium is widely used in the production of containers for the food and drink industry, predominantly beverage cans, such as those for soft or alcoholic drinks. The mass production is followed by mass consumption and impressive numbers of aluminium cans are emptied on a daily basis in consumerist societies. A great percentage still goes to landfill, which is a waste as this material can be easily recycled.
The recycling process: The same progression applied to raw materials initially used for obtaining aluminium is applied to scrap aluminium, namely the Hall-Heroult process. After collection and sorting from other metals, aluminium (usually in the form of cans) is taken to a recycling plant, where it is shredded and melted with the aid of an electric arc furnace.
After melting, it can be turned into ingots, rods, powder etc. according to its further use. In order to transform it into ingots, reverberatory furnaces are used. The ingots are then turned into other shapes, commonly aluminium sheets, such as those used for making beverage cans. The final step is obtaining the desired products and placing them on the market, only to be recycled again after consumption and collection.
Recycled aluminium products: The most prevalent use of aluminium today is in the food and drink industry, as packaging, in the form of cans. Aluminium cans are heavily used for soft drinks as well as alcoholic drinks (mostly beer), and since these are usually bought in bulk, the demand and resulting waste is considerable. The process can be used over and over again at a fast pace, to keep up with the pace of consumption, therefore it is important to keep recycling these items.
A vast number of everyday use machinery and appliances are made from or contain steel, such as vehicles or household devices.
Vehicle and machinery parts: A significant part of the recycled steel comes from vehicle parts, mainly car bodies, but also engine blocks and industrial scrap steel obtained from dismembering a variety of machines.
Domestic scrap: Many items within a household are wholly or partially made from steel, for instance white goods, such as washing machines, water tanks refrigerators and freezers. They are commonly recycled into new steel products. Cast iron items such as baths undergo the same process.
Construction materials: The use of steel is prevalent in the constructions industry due to its physical qualities, the most important being its resilience. It is used for making mesh and reinforcing bars, which strengthen the structure of concrete buildings.
Machinery: Heavy machinery, such as that used in the constructions industry and mining industry (which often uses a non- magnetic variation called manganese steel), is often made from steel. Some of it is referred to as heavy melting steel, if the sheets are of considerable thickness.
The recycling process: In order to recycle steel the first step is to separate it from other materials, which commonly takes place in steel mills. One such process is referred to as de-tinning, which is the separation of steel from tin, followed by recycling both metals disjointedly. The two are frequently combined in the manufacturing of steel cans. Steel is highly magnetic, therefore the purification process, whatever the other material involved, is usually done with the use of magnets (except the case of manganese steel, which is non-magnetic).
The steel (which consists of various types of scrap) is then placed into a furnace and melted at very high temperatures. Two types of furnaces can be used, depending on the type and quantity of steel to be meted – the electricarc furnace is predominant yet the blast furnace is sometimes used as well. From the furnace, the melted steel is poured into casters and undergoes a rolling process, in order to obtain steel sheets of various thicknesses. From these sheets, new products will be manufactured.
Recycled steel products: There is no limit to the number of times the recycling procedure can be used - the resulting steel always maintains its initial quality and endurance. That is why recycled steel needn’t go into inferior products and can be used for making the same types of items it originated from. It is very common for food cans to contain high percentages of recycled steel. It is also employed in making car parts, construction materials, household goods and any type of object new steel is used for.
Copper: Another commonly recycled metal is copper, which is deemed quite valuable and has been since its early use, in ancient times. Copper wire is widely used nowadays in electrical cables as it has excellent conductivity; when used for that purpose, it requires the highest purity. There are lower grades of copper (with lower purity) as well. Copper mining involves high costs and a substantial amount of energy, therefore recycling helps save both. Scrap copper either comes from old domestic appliances or from factories, in the form of trimmings and offcuts.
Zinc: In a variety of industries, zinc is used for galvanising steel, to which it provides protection against deterioration, significantly increasing its durability and thus its lifespan. Since it is mostly found as a coating, it is recovered from galvanised steel scrap when the steel is recycled.
The benefits of recycling metal: Compared to using new metal, using recycled metal puts less of a strain on production costs as well as the environment, as is saves energy (often needing lower temperatures for processing – for instance aluminium), uses less water and results in a lower level of air and water pollution as well. Manufacturing new items takes less time as well, as the metals have already undergone some essential processing which needn’t be repeated. As technology progresses and people replace their out-dated appliances with new ones, it is essential not to waste those which are no longer in use.
Did You Know?
According to Defra, each person in England produced an average of 457 Kilograms of waste in 2009-10. Of this, an average of about 181 Kilograms per person was recycled. That left 60% of un-recycled waste, at an average of 276 kilograms per person.