Aluminum cans are ubiquitous containers, widely recognized for holding beverages like soda and beer, and also used for various food products. These containers are primarily made of aluminum, a lightweight and malleable metal. Understanding their journey, from raw material to a recycled product, highlights their pervasive presence in daily life.
From Ore to Metal
The journey of an aluminum can begins with the extraction of bauxite ore. This reddish-brown rock serves as the primary source of aluminum, often found close to the surface, making open-cast mining a frequent retrieval method.
Once extracted, bauxite undergoes a refining process to separate the aluminum compounds. This involves crushing the ore and treating it with a hot caustic solution, which dissolves the aluminum compounds, forming a slurry. Impurities are then filtered out, and the purified alumina precipitates as a white powder.
Pure aluminum metal is then obtained from alumina through an energy-intensive smelting process. Alumina is dissolved in a molten salt bath, and a strong electric current separates the aluminum from oxygen. This primary production transforms the raw earth material into the usable metal.
Crafting the Can
The manufacturing of an aluminum can transforms flat aluminum sheets into the familiar cylindrical form. This process begins with large coils of aluminum, which are uncoiled and fed into presses. The aluminum sheet is first cut into circular discs, which are then drawn into shallow cups.
These cups then undergo a series of drawing and ironing steps, where they are stretched and thinned to create the can’s body. This process gives the can its characteristic height and reduces the metal’s thickness while maintaining its strength. The can body, including the bottom, is formed from a single piece of aluminum.
After the body is formed, the can is trimmed to a uniform height, and the top rim is necked and flanged to prepare it for the lid. Cans are then cleaned, and a protective epoxy lacquer or polymer coating is applied to the interior to prevent corrosion and maintain the product’s flavor. Finally, the exterior is printed with designs and branding, and a separate lid is sealed onto the can after filling.
The Recycling Process
When an aluminum can is collected for recycling, it rapidly returns to the manufacturing stream. The collected cans are first sorted from other recyclable materials, often by eddy current separators that repel the non-magnetic aluminum. Following sorting, the cans are shredded into small pieces, which helps in cleaning and prepares them for melting.
The shredded aluminum pieces then undergo cleaning to remove contaminants like labels, food residue, or internal coatings. This ensures the purity of the aluminum before it is melted, as impurities can affect the quality and properties of the new aluminum product.
After cleaning, the aluminum shreds are melted down in a furnace at high temperatures, around 660 degrees Celsius (1220 degrees Fahrenheit). The molten aluminum is then purified to remove any remaining non-aluminum elements. This purified molten metal can then be cast into large ingots or directly into new sheets, ready to be used again in can manufacturing. A recycled can can become a new can in as little as 60 days.
The Circular Economy of Aluminum
Aluminum recycling is a testament to circular economy principles, allowing the material to be reused repeatedly without significant loss of quality. Aluminum is considered infinitely recyclable, meaning it can be melted down and reformed into new products countless times. This characteristic positions aluminum as a highly valuable material in the recycling industry.
This continuous re-entry of recycled aluminum into the manufacturing stream offers substantial environmental advantages over producing aluminum from virgin ore. Recycling aluminum saves a considerable amount of energy, estimated to be up to 95% compared to primary production. This energy saving translates directly into a significant reduction in greenhouse gas emissions.
The high recycling rates of aluminum cans contribute to a lower carbon footprint for the packaging industry. This closed-loop system reduces the need for new raw material extraction and minimizes waste, underscoring the benefits of choosing aluminum for packaging.