In recent years aluminium alloys have been favoured by the automotive manufacturing industry for their lightweight properties and lower cost. The ongoing evolution of production processes has increased the speed in which manufacturers, especially automotive manufacturers, have shifted from steel to aluminium. While the lightweight properties of aluminium is a key reason for this shift, the automotive industry is also interested in its durability, corrosion resistance, and easier maintenance thanks to new tools and techniques. When converted to an aluminium alloy it can enable even higher strength and ductility.
However, a study, conducted by Cranfield University’s Sustainable Manufacturing Systems Centre, compared three different alloys (Aluminium-A380, Magnesium-AZ91D and Zinc-ZA8) and discovered that switching from aluminium to zinc alloys in the production of automotive parts could greatly enhance their longevity and sustainability.
The study, published in the ‘International Journal of Sustainable Manufacturing’, suggests that aluminium is frequently chosen ahead of other alloys because of a failure to fully factor the sustainability of the end-product into consideration. When examining sustainability alongside traditional factors such as time, cost and flexibility, Cranfield’s research demonstrated that zinc alloys offered a better choice for automotive manufacturers over the aluminium or magnesium alloys.
Why Zinc is more sustainable
The zinc alloy proved to be a more sustainable and higher-performing option, when considering measures such as the environmental impact caused by the extraction of the metal and the quality of the parts it produces. Despite the aluminium alloy being a lower cost option, the study found that the zinc alloy also offered better value for money as the parts it creates are likely to have a much longer life than the other alloys.
“A zinc alloy can be better value for money as well as being more sustainable.”
Professor Konstantinos Salonitis
Energy efficiency, although only part of the consideration, is also important for the metal casting process and therefore a key consideration of sustainable manufacturing. A paper - Metal casting energy-efficient metrics for material selection of automotive parts - co-authored by Dr Emanuele Pagone, Dr Michail Papankiolaou, Professor Konstantinos Salonitis and Professor Mark Jolly highlighted that the process based on the Zinc-ZA8 alloy also has the potential to be the most energy-efficient.
The move to sustainable manufacturing
The automotive sector is one of the main end-use markets for metal casting worldwide. The strong competitive pressure typical of this industry has been influenced in recent years by sustainability as a new factor promoted by legislation, increased societal awareness of relevant instances and resource scarcity.
The pressing needs of water, energy and natural resources is a major challenge, and this has come to the fore with the current coronavirus pandemic highlighting reductions in emissions and energy. You may have seen the NASA satellite images of pollution reduction in China. The unprecedented lockdown in China led to an estimated 25 percent reduction in energy use and emissions over a two-week period compared to previous years (mostly due to a drop in electricity use, industrial production and transport), according to a ScienceAlert article.
“With the pressing climate crisis, consumers are becoming ever more interested in the impact that the products they purchase have on the environment.”
Professor Mark Jolly, Director of Manufacturing
Manufacturers are investing in, and developing, green technologies. Sustainable manufacturing innovation is needed, along with a deeper understanding of the manufacturing environmental burden so that we can ensure a total life cycle impact reduction.
Previous Cranfield research has demonstrated that the automotive industry’s focus on increasingly lighter weight cars to increase fuel efficiency, often through the use of lightweight aluminium, may not actually be a more environmentally sustainable option. The conclusion is based on a ‘cradle-to-grave’ study of the total energy and CO2 impact of passenger vehicle engine production, interviewing more than 100 manufacturers and industry experts, from mining through to engine production and on-the-road use.
In the study, the Sustainable Manufacturing Systems Centre found that the sole focus on tailpipe emissions as a measure of environmental impact has led to serious unintended consequences. In order to cut fuel use and emissions, the automotive industry has been pushed into using lightweight aluminium in the manufacture of vehicles with a far higher cost to the environment than any savings achieved through reduced tailpipe emissions.
The aluminium industry has argued that the highest energy consumption occurs during the production of ‘virgin’ aluminium from ore, and that cylinder block production primarily uses recycled aluminium. The Cranfield study took this into account, adopting the best-case scenario for aluminium via infinite recycling.
The research conducted by Cranfield’s Sustainable Manufacturing Systems Centre has wide-ranging implications for automotive manufacturers and highlights the narrow view of what makes a car environmentally friendly. It’s critical that governments and consumers start to look at the whole life cycle of what is involved in manufacturing vehicles if we are to #BuildBackBetter.