Aluminium encyclopaedia

The extraction of primary aluminium using fused-salt electrolysis requires more energy than processes used to extract other metals. Energy costs are a significant part of the production costs. Thus, it is in the economic interest of the industry to reduce its energy requirements and its energy costs. Some facts and figures:

• Since 1950 the energy requirement for fused-salt electrolysis has been reduced by over 30 per cent thanks to a range of technical improvements.

• The recycling and remelting of aluminium scrap requires up to 95 per cent less energy than for primary production of the metal.

• Reducing the thickness (gauge) of many products saves material (in the case of beverage cans, about 40 per cent since 1980) and thus energy.

• Power generation is carried out using hydroelectric power instead of fossil fuels.

Many aluminium products are used from the outset to save energy or to use it rationally, for example heat exchangers in air conditioning systems or thermally insulating window frames and cladding panels in building construction.

Compared with other materials, aluminium can also save energy. Such a comparison has to be based on an energy balance: on the one hand there is the energy required to extract the metal and process it into products and to use them during their whole utilisation period, and on the other there are the savings in energy during the whole utilisation period.

Especially with rail and road vehicles, the use of aluminium instead of steel saves energy; this is because the vehicles can be made lighter thanks to the lower specific weight of aluminium compared with steel (2.7 grams per cubic centimetre against 7.8 grams per cubic centimetre) and the metal"s good constructional properties; they thus require less energy to move them. This is particularly marked with vehicles that have to accelerate frequently.

In order to reduce emissions, it is not only important to develop engines with low emissions but also to use them as economically as possible. Weight reduction using aluminium is a good way of achieving this goal.

Aluminium contributes to reducing carbon dioxide emissions in transport and transportation in a number of ways:

• When transporting heavy goods, more can be transported per trip. By saving one tonne in weight one saves about 1500 litres of fuel per 100,000 km.

• When transporting voluminous goods, the total weight is reduced and with it the fuel consumption. By saving one tonne in weight one saves about 600 litres of fuel per 100,000 km.

• The use of aluminium in local public transport also leads to considerable savings in vehicle weight and fuel consumption. A saving of one tonne in the weight of a bus leads to fuel savings of 1700 to 1900 litres per 100,000 kilometres.

If one considers the total energy used during primary production, the utilisation period and recycling at the end of a vehicle"s life, the following savings can be made:

• In modern articulated lorries, every kilogram of aluminium saves on average 28 kilograms of carbon dioxide.

• In an articulated lorry of the future, each additional kilogram of aluminium would save at least 20 kilograms of carbon dioxide.

• A kilogram of aluminium in a bus saves some 40 to 45 kilograms of carbon dioxide.

Underground train carriages are lighter than those made of steel so that after as little as three years the energy balance is at break-even point and is increasingly positive thereafter. With a utilisation period of some 35 years (long thanks to the corrosion resistance), the energy saving is equivalent to the amount used to manufacture a further ten carriages from primary aluminium.

As a result of using aluminium-containing packaging, less packaging is needed for transport and thus more contents can be moved than with conventional materials. With flexible packaging, such as drinks cartons or stand-up pouches with aluminium foil as a barrier layer, better use is also made of the shipping volume, which results in less trips being made.

Recycling and remelting tilts the energy balance further in aluminium"s favour.