For the foreseeable future, sustainable management of the environment will be one of the greatest challenges facing our planet. The aluminium industry is committed to reducing energy consumption and emissions through more efficient production and recycling.
Aluminium production, recycling and surface finishing
Gooding Aluminium believes in, and is therefore committed to, policies that provide for sustainable development which meets the needs of the present without compromising the ability of future generations to meet their own requirements.
There is a growing awareness within all of us of the many environmental issues that are developing our values and driving demand for ‘green’ products and services. More and more client specifications are calling for environmentally conscious material selection. The aluminium industry has appreciated for some time that today shapes tomorrow. Many advances in production technologies are being made that are helping to conserve resources, reduce emissions and eliminate disposal issues in the production of primary aluminium. Environmental issues are frequently complex and contested. We therefore only seek, in this part to provide a broad outline of the environmentally significant aspects that are at the heart of aluminium production. Information on life cycle performance and surface finishing technologies is also provided.
There is generally, particularly within the architectural industry, an increasing emphasis being placed on sustainability.
Nature has fortunately provided generous supplies of aluminium; it is the 3rd most common element and the most abundant metal. Only silicon and oxygen are more plentiful. Over 7% of the earth’s crust is made up of bauxite (from which aluminium is produced). Aluminium is considered harmless to animals and plants. It is reassuring to know that even based on current rising usage rates there are many hundred year’s worth of supplies remaining.
Bauxite is easy to mine, but extracting the aluminium from the bauxite is a complex and power intensive process. Production of aluminium takes place in two stages.
The first stage separates the alumina from the bauxite by means of a chemical process.
The second stage reduces the alumina to aluminium using an electrolytic refining process.
Electricity is essential to produce aluminium. Electrical power makes up about 1/3rd of the cost of producing a tonne of primary aluminium. The major incentive in continuing with these efficiency gains is that each saving in energy consumption translates immediately into significantly reduced costs of production.
More than 55% of the world’s aluminium production is powered by environmentally friendly renewable ‘white energy’. The largest national producers, Canada, China, Russia and the United States have located many of their production plants close to sources of cheap hydroelectric power.
During the past two decades producers have been improving their efficiency through better process control and operating practices. Advanced smelting technologies are being introduced, including the prebaked anode method, that are making major energy efficiency gains of up to 25%, by reducing the amount of electricity required to produce the aluminium.
As with every industrial process there are environmental considerations with the variousstages of aluminium production. The primary production processes of refining and smelting result in greenhouse gas emissions. However the global aluminium industry has become a leading pioneer in adopting new technologies that are successfully achieving a declining trend in overall emissions. PFC emissions have reduced by 60% per tonne since the early nineties. While overall production has increased by around 25% over the past ten years, total emissions to the atmosphere have successfully been reduced. Research is also ongoing into anode materials (these are used during the electrolytic process) that contain no carbon. These carbonless anodes, if successfully developed on a commercial basis, would completely eliminate PFC emissions. Currently the worldwide recycling of aluminium is estimated to annually save over 80 million tonnes of greenhouse gas emissions.
Life cycle performance
Life cycle performance is assuming increased importance. In aluminium, the real environmental benefit is in the recovery of the metal through recycling and looking towards the future.
Once produced, aluminium offers the clear ‘cradle to cradle’ advantage that it can be repeatedly and efficiently recycled without any loss of quality. It is considered, in this sense, the ‘greenest’ of
metals, being 100% recyclable. Landfill space is saved and the effects of this practice reduced by the production of aluminium from scrap.
When aluminium products reach the end of their useable life they can be transformed, by recycling, into new forms using only a fraction, about 5%, of the energy and emissions originally required in their initial production. Raw materials are therefore preserved and considerable energy savings made.
Over the past thirty years the importance of aluminium recycling has been underlined by a tripling in its output. Recycling aluminium drinks cans is an important material source. Domestic supplies of scrap account for about 40% of the aluminium recovered from recycled sources. It is the industry’s ambition to recycle all sources of aluminium scrap.
There is a growing recognition that this feature of recyclability results in the increasing reserves of aluminium stock acting much like a reserve of valuable stored energy, that can be repeatedlyused over time. Manufactured aluminium products can therefore be endlessly and economically recycled to produce new products. End of life (EOL) collection ratios are high for the building and construction industry. Significant aluminium recycling rates of around 85% are being achieved within this market.
The virtuous expanding circle of aluminium recycling represents an ever increasing proportion (currently over 35%) of total aluminium production. This can be viewed as a gilt-edged energy investment for the future.
Compared with the production of primary aluminium, recycling produces only about 5% of CO2 emissions. Recycling one kilogram of aluminium saves over 7 kilograms of bauxite, 4 kilograms of chemicals and 13 kilowatt hours of electricity.
There are many options for finishing aluminium. We include below a brief overview of two alternative technologies that satisfy thecriteria for environmental compliance and high performance.
Environmental friendliness and its relative safety are two of anodising strongest qualities. The process does not require the use of solvents nor does it contain volatile organic compounds (VOCs) and no heavy metals are involved.
Since anodising is a magnification of a naturally occurring oxide process it is considered nonhazardous. An anodised finish is chemically stable, doesn’t decompose and is non-toxic.
Anodising uses simple water-based chemicals that can be treated easily and that release no harmful by-products. The liquid by-products are recycled and returned to the process. A mixture of aluminium hydroxide, aluminium sulphate and water is created as a by-product of the anodising process. Due to the absence of any significant production of heavy metals this substance is considered harmless. Solid by-products can be isolated and diverted for use in the manufacture of various products including cosmetics, fertilizer and newsprint.
Polyester Powder Coating
Powder coating is a completely dry finishing process. The powder paint is pigment contained within a powdered resin and is considered as paint without solvents.
Powder coatings, unlike conventional liquid paint technologies contain no solvents and are virtually 100% free of volatile organic compounds (VOCs). One of the biggest advantages over liquid paints is the elimination of air and water pollution. No VOCs are emitted when powders are cured in an oven.
There are several energy saving benefits to be gained with the use of dry powders. Due to the absence of VOCs, exhaust and therefore power requirements for the curing ovens are lower than those for liquid paints. No drying is required with powder, therefore by stacking the items closer together better use can be made of the available oven space.
There is a uniquely high material utilization rate with sprayed powders as any overspray can be recovered and re-used, waste is virtually eliminated.