Introduction
Aluminum has emerged as the ultimate solution in enhancing eco-efficiency in beer and soft drinks packaging. Aluminum’s expanded use in making of cans is owed to its properties. These include ability of its thin walls to withstands up 90 pounds of pressure, its shiny surface after finishing which facilitates easy decoration process, its cheap costs due to ease of smelting, and its light weight. Most importantly, aluminum has been able to fit into the ideal modern day dream of creating sustainable manufacturing practices through its ease of recycling. Aluminum is remarkably one of the highest recycled packaging materials in the recent times (WBCSD, 2000). In developed countries, industries have created collection points for used cans. One such case is Pepsi in America (Reid & Miedzinski, 2008: 34).
Raw Materials
Aluminum beverage can is primarily made of aluminum. Unlike, in the past where only the top was aluminum today the whole can is made from aluminum. However, small amounts of other metals are also present including 1% Mg, 1% Mn, 0.4% Fe, 0.2% Si, and 0.15% Cu. It is traditionally derived from bauxite which is smelted to produce molten aluminum ingots. Considerably large percentage of cans manufactured, are a product of recycling. In America, up to 95% of beer and soft drink cans are a product of aluminum recycling and a total of 25% of total American aluminum are obtained through recycling. Significantly, a considerable amount of energy saving is attained through recycling of aluminum cans. It has been proved that for every pound of aluminum recycled, a total saving of energy resources required to produce approximately 7.5 kilowatt-hours of electricity is achieved.
Manufacturing Process
Aluminum cans undergo a process known as two-piece drawing and wall ironing (Hwang, Huang & Xu, 2006). The aluminum ingot, about 76cm thick is rolled into a thin metal sheet, after which it’s cut into a circle through blanking. The blanks form the bottom part of the can. The blanked pieces typically have 14 cm diameter. The lost material during this process is re-used as scrap (up to 14%). The circular blank is then drawn to form a cup of 8.9 cm diameter. The drawn cup is moved to another machine where a sleeve is used to hold the cup in a specific position; punch is then used to redraw the cup to attain a diameter of 6.6cm. This results into an instantaneous rise in the cups height from initial 3.3 cm to 5.7 cm (Hosford & John, 1994: 51). It is then subjected to punching against ironing rings which stretch and thin its walls. At this point, the cup attains a height of 13 cm. another punch is used to press the cup base resulting into its inward-bulging shape. The bulge is meant to counteract pressure resulting form the carbonated liquid it’s intended to hold (Singh, 2003). The lower and the bottom can parts are made slightly thicker than the other can parts for purposes of enhancing strength.
After drawing and ironing, the cup is left rather wavy at the top. This is a characteristic common with aluminum’s crystalline structure. To achieve a straight upper wall, trimming is done and some material is also lost at this stage, which is recycled for use. The aforementioned processes leave the outer part of the can smooth and shiny and hence no need for additional finishing. The can is cleaned and redecorated then squeezed to produce an outward neck flange at the top part. This part is later to be folded after addition of the lid (Larson, 2003).
The lid is slightly made differently from the rest of can. This is due to its specification requirement that it be stiffer and stronger as compared to the base. More magnesium and reduced manganese are therefore used for this process. The lid, which is a stronger metal, is cut to produce a diameter of 5.3 cm. The center is then stretched outwards in order to produce a rivet. This is where the pull lid is inserted. For ease detachment when pulled by the consumer, the lid is scored. The cans are evaluated for cracks prior to usage (Hosford & John, 1994). The can is then ready to be filled and sealed and hence destined for the larger market.
Byproducts/Waste
From the manufacturing process described, some aluminum is lost at various production stages. However, due to the can eco-efficiency, no actual loss is recorded as the pieces are re-used (WBCSD, 2000: 24). The ultimate can, after use by consumer is also fed back into the system for recycling. Re-used can require lesser processing energy and saves a lot to the manufacturing in addition to preservation of the environment (Boulanger, 2010). The cans eco-efficiency can generally be summarized by the flow diagram below:
As shown by the diagram, the system re-admits most of the waste which would have otherwise found its way to the environment negatively impacting on the same (Schlesinger, 2006). Additionally, the recorded energy savings could be directed fro other purposes within society (Lovins, 2008).
References
Boulanger, P.M. (2010). Three strategies for sustainable consumption”. Journal of Sustainable Development, 45(3), pp. 234-256.
Hosford, W. F. & John, L. D. (1994). The Aluminum Beverage Can. Scientific American, 12(4), pp. 48-53.
Hwang, J.Y., Huang, X. & Xu, Z. (2006). Recovery of Metals from Aluminium Dross and Salt cake, Journal of Minerals & Materials Characterization & Engineering, 5 (1), pp 47-62
Larson, M. (2003). New Ideas Come In Cans. Packaging, 12, pp. 30-31.
Lovins, L. H. (2008). Rethinking production in State of the World. Geneva: International Standards Organization, p. 34.
Reid, A. & Miedzinski, M. (2008). Eco-innovation: Final Report for Sectoral Innovation Watch (Brighton: Technopolis Group), Web.
Schlesinger, M. (2006). Aluminum Recycling. CRC Press, p. 248
Singh, S. P. (2003). Internal Gas Pressure on the Compression Strength of Beverage Cans and Plastic Bottles. Journal of Testing and Evaluation, 32(7), pp. 129-31.
WBCSD (2000). Eco-Efficiency: Creating more value with less impact. World Business Council for Sustainable Development.
WBCSD (2000). Measuring Eco-Efficiency: A guide to reporting company performance. World Business Council for Sustainable Development