As the loss of metal in the remelting process is such a small percentage, and the remelted material keeps the same quality, this allows the same metal to be used in the same product over and over again. (i.e. almost absolute recycling.)
The purpose of recycling is to produce new high quality material from waste and used products in an economical and environmentally friendly manner.
There are generally two kinds of raw material for recycling, process scrap and waste from the aluminium industry.
The process scrap is easy to identify and it has a well known composition, while on the other hand aluminium from used products is much more complex. However, both types of scrap can be processed and recycled to a high standard.
Finishes to the aluminium are simply burned away in the melting process and any noxious gas emissions are collected in efficient fume capture equipment. This gas is burned off providing heat to the furnaces. Non-metallic components end up in the salt slag, and an inert substance skimmed from the molten aluminium is used in the cement industry. Thermal breaks or resin are either mechanically separated or simply burned away in the process. Where aluminium is combined with other metals such as stainless steel screws and fixing lugs, this aluminium is fed into a special furnace that separates the iron thermally (i.e. iron and steel melt at a higher temperature than aluminium and are also heavier. As a result they fall to the base of the furnace, thus ensuring 100% aluminium can be accessed.)
Gasketry must be manually removed from the window as part of the deglazing process. Material is then sent to a rubber recycling plant where it can be re-smelted or ground into granules.
In many of these cases, the stainless steel has suffered little degradation and still contains a high value of the initial alloying elements such as chromium, nickel and molybdenum. This makes it a valuable source of those constituents to the stainless steel producer and a high proportion of material going into the melting furnace is usually recycled.