Aluminium recycling
[1] It involves re-melting the metal, which is cheaper and more energy-efficient than the production of virgin aluminium by electrolysis of alumina (Al2O3) refined from raw bauxite by use of the Bayer and Hall–Héroult processes.
Once collected, aluminium scrap is sorted based on alloy type, grade, impurity levels, and other factors.
Pre-treatment improves the density of the scrap charge and removes contaminants, resulting in faster melting, cleaner metal, reduced dross formation, and lower energy consumption.
As the scrap melts, fluxes are added to bind and absorb impurities which are scraped off the top as dross.
[12] The molten recycled aluminium is cast into solid forms such as ingots, sows, or directly into sheets or extrusion billets.
Direct-chill casting is commonly used to solidify the liquid aluminium into large cylindrical billets for extrusion or rolling.
The Hall-Héroult process for aluminium production from alumina was invented in 1886 by Charles Hall and Paul Héroult.
[17] Carl Josef Bayer created a multi-step process to convert raw bauxite into alumina in 1888.
[21] Over the long term, even larger national savings are made when the reduction in the capital costs associated with landfills, mines, and international shipping of raw aluminium are considered.
The vast amount of aluminium used means that even small percentage losses are large expenses, so the flow of material is well monitored and accounted for financial reasons.
[27] Many countries now seek to decarbonize aluminium not only as it is the second most used metal in the world, but also because it would heavily address the total greenhouse gas emissions in an effort to slow climate change.
Since 1991, greenhouse gas emissions from aluminium cans have dropped about 40%, similar to energy demand levels.
On the other hand, Canada sources roughly 90% of its primary aluminium production using hydroelectric power, considering it to be the most sustainable in the world.
In fact, the Environmental Protection Agency considers recycling a "critical" part of the United States economy, contributing to tax revenue, wages, and job creation.
[32] This type of economy focuses on minimizing the extraction of natural resources, leading to a reduction of consumer and industrial waste.
A few examples of countries that have adopted the shift to a circular economy include the European Union, Finland, France, Slovenia, Italy, Germany, and the Netherlands.
[33] A recent study conducted within the United States has highlighted some ways that aluminium recycling has proven to have economic benefits, including: As countries take note of the various economic and environmental benefits of aluminium recycling, increased efforts are expected to improve the efficacy of this process.
Due to the levels of impurities found after refinement, the applications of recycled aluminium alloys are limited to castings and extrusions.
