Aluminium is a comparatively young metal and its commercial use dates back only about 150 years. However more aluminium is produced today than any other non-ferrous metal.
Aluminium is one of the most widely used metals in the transport (cars, trucks, buses, trains and aircraft), construction (roofing, wall cladding, windows and doors), packaging (cans, aerosols, foil and cartons) and electrical sectors. In all sectors, it is valued for being light, strong, durable, flexible, impermeable, thermally and electrically conductive and non-corrosive.
Bauxite, the natural ore used to make aluminium, is one of the most abundant minerals in the earth’s crust. Mined bauxite is refined into alumina, which is then smelted into aluminium. Approximately four tonnes of bauxite are required to refine two tonnes of alumina, which in turn are smelted to make one tonne of aluminium metal.
Aluminium and sustainability
In many of its applications, aluminium provides environmental benefits. Its light weight helps improve the fuel economy of cars and planes and reduces emissions. When those vehicles are eventually scrapped, 95 percent of the aluminium can be recycled.
Because aluminium can be infinitely recyclable, 75 percent of all aluminium ever produced is still in use, with no loss in quality. Recycling aluminium uses only 5 percent of the energy – and produces only 5 percent of the greenhouse gas emissions – of the average primary production rate. Beverage cans are among the most recycled aluminium products in the world, and can be back on the shelf just six weeks after their first use.
Despite these benefits, there are also a number of sustainability challenges specific to the aluminium industry. These include:
- energy and greenhouse gases;
- waste management;
- biodiversity and land management;
- resource efficiency and recycling; and
- indigenous rights and local communities.
Energy and greenhouse gases
Existing primary aluminium production processes are energy intensive by nature. The main source of energy consumption during production is the electricity used for the electrolysis process. During the refining of alumina from bauxite ore, a significant amount of energy is also required to produce the solution of bauxite in caustic soda, for the calcination process and for the recovery of caustic soda after use. As energy costs are a major part of overall production costs, improved energy efficiency is essential for the aluminium industry, both from an economic and environmental point of view. Improved energy efficiency will also reduce indirect emissions from production of the electricity used in the electrolysis process.
Primary aluminium production results in associated direct greenhouse gas emissions from the use of fossil fuels in the alumina calcination process, as well as indirect emissions from production of electricity used in the electrolysis process. Direct greenhouse gas emissions also arise from process-related conditions in electrolysis, such as consumption of anodes (CO2) and PFC emissions (PerFluoroCarbon) from anode effects. Reduction of greenhouse gas emissions from energy use and from the electrolysis processes is thus important to reduce the overall carbon footprint of primary aluminium.
Between two and four tonnes of bauxite are required to produce one tonne of alumina. Once the alumina is extracted from the bauxite, the remaining bauxite residue is stored in landfills. Disposal of the bauxite residue is a challenging aspect of alumina production due to relatively large volumes, occupation of land areas, and the alkalinity of the residue and the run-off water. The way of storing of bauxite residue and handling of run-off water is critical.
Aluminium smelters also generate significant quantities of solid waste. One of the main sources of waste production during the smelting process is from the relining of pots, which takes place every five-to-eight years. The carbon portion of the spent pot lining (SPL) is considered a hazardous waste because of its fluoride, cyanide, PAH and reactive metal content. The refractory materials are not considered hazardous. It is thus important both to minimise the generation of SPL by extending life times of the pots, as well as to ensure proper handling of SPL waste through treatment or use by other industries, such as the cement industry.
Biodiversity and land management
The vast majority of the world’s bauxite comes from surface mines in tropical areas, where bauxite occurs in horizontal layers, normally beneath a few meters of overburden. Because bauxite is located close to the surface and with relatively shallow thickness, bauxite mining involves disturbance of relatively large land areas, which can include natural and critical habitats. As a result, mining sites may overlap with, or be adjacent to, protected areas and/or areas of conservation value (particularly in tropical areas), and may result in significant deforestation. Effective mitigation of biodiversity impacts from bauxite mining will involve avoiding negative impacts (including avoidance of invasive species) to protected areas and areas with natural and critical habitats, as well as rehabilitation of mined areas.
For logistical reasons, most alumina refineries are located close to a bauxite mine, or at the nearest harbour from which the alumina can be shipped out. Thus, there may be similar biodiversity challenges at refinery sites, landfills for bauxite residue deposits or bauxite slurry pipelines.
Resource efficiency and recycling
Minimising losses of aluminium wherever they might occur in the value chain is a high priority for the aluminium industry. The concept of resource efficiency is a guiding principle, and actions to minimise losses can include optimisation of material use in the first place, tailoring the material use to specific applications, design for environment and recycling, or recycling of scrap.
In most cases, recycling of aluminium is economically and environmentally beneficial. Aluminium can be recycled an infinite number of times with no loss of quality. As a result, there is a very large and growing global aluminium material pool, and a well-developed global refining and recycling capacity, which itself creates a strong demand for scrap.
While minimisation of process scrap in the production and fabrication stages is the first step towards improving environmental performance (energy consumption and emissions per tonne of product), the minimisation of post-industrial and post-consumer scrap and waste is also a priority. Collection and recycling of process as well as post-industrial and post-consumer scrap is also important to minimise waste and bring scrap back to useful products. This is relevant for all process steps, from primary aluminium production, through to production of end-user products and end-of-life management. Post-consumer aluminium scrap is generally recycled very successfully, with significant energy and emissions reductions compared to primary metal production. In addition, recycling of post-consumer products helps to significantly minimise resource use and reduce waste going to landfill.
Overall aluminium recycling rates are impressive and growing: The International Aluminium Institute (IAI) reports end-of-life recycling rates for aluminium used in building and transportation at 90 percent. In Europe, consumer packaging recycling/recovery rates are at about 60 percent, with some packaging forms such as beverage cans as high as 70 percent, while other forms are below 50 percent. Robust data on material collection and recycling are not available in many countries, however.
In order to optimise and improve collection and recycling of post-consumer aluminium scrap, products need to be designed in a way that enables and supports efficient collection and recycling. This is especially challenging for complex products that utilise combined materials (such as composites used in buildings and transportation or multi-material laminated packaging), as these products need to be dismantled into separate material streams before re-melting.
The majority of aluminium is used in products with very long use phases, for example transportation products that have a typical lifetime of 20 years or buildings with lifetimes of approximately 50 years. The IAI reports that 75 percent of aluminium ever produced is still in circulation. Even with growing volumes of aluminium recycling and increasing end-of-life recycling rates, the strong overall global demand for aluminium means that the production of primary aluminium is required to support this growth.
Recycling of post-consumer scrap and waste requires a number of conditions, including the availability of systems to collect and sort used materials, and the adequate design of products that enable classification and recycling, among others. Collection infrastructure is not available everywhere in the world or for all types of products. Millions of people depend on collecting recyclable materials from streets, dumps, abandoned sites and even landfills. It will be a challenge to maintain the vital role they perform while supporting them with improvements to the health and safety conditions of their work.
Indigenous rights/local communities
Mining and mining-related activities (exploration, development, resource extraction, processing, transportation and waste disposal) often take place on, or near, indigenous lands. Mining or large-scale industrial development requires access to land and water that is often the basis of livelihoods for local communities.
Major industrial developments can have significant adverse impacts on indigenous groups and/or vulnerable groups and individuals, affecting their rights to self-determination, infringing on their lands, territories and resources, and threatening their ability to maintain their culture, including their cultural heritage and recognition of their distinct identities.
The possibility of project-related resettlement holds the potential for human rights infringements. It is important to ensure that indigenous groups be given sufficient opportunity and resources to be able to offer their free, prior and informed consent (FPIC) in decisions that may affect them, particularly in relation to projects that may impact their lands, territories and natural resources.
At the same time, mining and industrial activities can have positive benefits for local communities, creating both direct and indirect employment and wage-earning opportunities, and can also generate government revenue and net foreign exchange earnings.
Closure or major restructuring of a mine or large industrial facility can have major impacts on the livelihood of affected employees, suppliers and local communities.
In areas of political instability and conflicts, the manner in which security of assets and employees is maintained can also pose risks to the rights of local people.
Upholding the rights of indigenous peoples and local communities, and supporting shared benefits from resource developments, remains an important priority for upstream producers.