While primary aluminium production more than doubled over the period 1990 – 2010, total direct greenhouse gases from the production process increased by only 20%.
In 1990, direct emissions (that is to say the emissions from the aluminium production process, not from generation of the electricity used in the process) were dominated by the potent greenhouse gases perfluorocarbons or PFCs.
PFCs can be produced in the primary aluminium reduction process, during events referred to as anode effects. An anode effect is a process upset condition, where an insufficient amount of alumina is dissolved in the electrolyte bath. This causes the voltage in the pot to be elevated above the normal operating range, resulting in the emission of gases containing the PFCs tetrafluoromethane (CF4) and hexafluoroethane (C2F6).
Reduction in the number and duration of anode effects since the early 1990s, through effective controls of alumina and anodes, but perhaps more importantly through the growth in production using state of the art, low PFC emitting technology, has seen PFC emissions per tonne of aluminium production fall by almost 90%. A reduction in total PFC emissions of over 70%. The aluminium industry has a voluntary objective to reduce further its PFC emissions per tonne of aluminium by 50% between 2006 and 2020.
This means that today, the sector’s direct greenhouse gas emissions are predominantly from the consumption of carbon anodes and from fuel combustion in the refining, anode production and casting processes, both of which are a function of production, with only limited opportunity for reduction, over and above incremental efficiency improvements. The industry has an objective to improve the energy efficiency of alumina refining by 10% between 2006 and 2020, a target which has almost already been met.
Indirect emissions from electricity supply have increased as a function of production increases and due to the fact that the industry’s global power mix has shifted towards thermal power sources. The industry reduced the electrical energy required to smelt one tonne of aluminium by 10% between 1990 and 2010 and has an objective to improve energy efficiency by a further 5% by 2020.
Materials in general, and aluminium in particular, have a unique role to play in sustainable development, as enablers of eco-efficient services: transporting people further and faster with lower energy inputs; bringing power to new, growing, productive communities with fewer energy losses; building green cities and preserving nutritional and pharmaceutical resources.
The potential benefits of using aluminium in such applications can be more significant than the potential for improvement in process efficiencies during production and at end of life.
The reduction of greenhouse gas emissions, for instance, through the use of aluminium intensive efficient machinery in industry; efficient cabling, turbines, solar panels, consumer durables and intelligent control systems in energy supply networks; lightweight vehicles; green buildings and protective aluminium packaging that preserves agricultural outputs is far greater than improvements in energy efficiency within aluminium industry processes.
“Driven by a quest for continuous improvement and ongoing innovation, over the past 25 years DUBAL has developed advanced reduction cell technologies that not only increase productivity but also reduce our operations’ impact on the environment through improved energy efficiency and reduced emissions.”