Guest essay by Eric Worrall
The pressure to conform to tightening vehicle emissions standards and fuel efficiency specifications is intense. Everyone knows about the recent Volkswagen Emissions Scandal, in which Volkswagen rigged the test to produce better results.
As part of the push for better fuel efficiency, which feeds through into a better emission profile, car manufacturers are replacing Steel components with Aluminium. Aluminium is lightweight, cheap, has good corrosion resistance, and has a low melting point, compared to steel – it is easy to cast, machine and weld.
The following graph shows the dramatic rise over the last few years, in the use of Aluminium for manufacturing cars.
There’s just one issue with this green triumph – refining Aluminium is incredibly energy intensive. Aluminium is smelted using Electrolysis. A pot of Aluminium salt is heated up to melting point, then a huge electric current is run through the molten salt for many hours, even days, to separate out the metallic Aluminium.
The following is a breakdown of the source of the electricity used to electrolyse the Aluminium. Note the surge in coal – the last column, for 2014, represents 400,572 gigawatt hours of electricity generated from coal, to smelt the world’s Aluminium.
World Aluminium also reports that in 2014, around 53.127 million metric tons of Aluminium were produced, up from 48.774 million tons in 2012.
Much of the rise from 48.774 million tons to 53.127 million tons can be accounted for by the rise in Aluminium used to manufacture cars, up from 5395 million pounds to 6886 million pounds. Converting to tons, Aluminium usage in cars surged from 2.6 million tons in 2012, to 3.4 million tons in 2015, a rise of 0.8 million tons. Aluminium production surged by 53.127 – 48.774 = 4.353 million tons. Therefore, if my calculation is correct, car manufacturing has consumed around a fifth of the rise in Aluminium smelting over the last few years. The electricity used by this increased smelting activity has mostly been produced from coal (note this calculation is using 2014 Aluminium production figures and 2015 automobile Aluminium manufacturing figures – so it is an approximation).
Obviously quite a lot of Aluminium is being used for goods other than cars – Aluminium is incredibly versatile and useful. But if you have already done the R&D, and tooled up to produce Aluminium components for cars, it is obviously also a lot easier to produce other useful Aluminium products.
While the rise in coal generated electricity to smelt Aluminium is dramatic, Aluminium smelting is only one of a range of factors driving the rise in global coal usage. The 400
GwH TwH used in Aluminium production is only a small portion of the rapidly growing multi-terawatt hours of electricity produced every year (40% of which is generated from coal, according to World Coal). But the rise in Aluminium car components, largely driven by stringent emission regulations, and pressure to improve fuel efficiency, is making a significant and increasing impact on global CO2 emissions.
Correction – in the last paragraph the electricity used for Aluminium production in 2014 should read 400 TwH, not 400 GwH (h/t Björn)