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  • S-in motion

    Steel solutions for lightweighting

S-in motion: A lifetime of savings

When it comes to greenhouse gas emissions, steel is the right choice for vehicles – and the planet!

By 2015, carmakers in the European Union will need to ensure their vehicles meet strict new carbon dioxide emission targets or they will face the threat of heavy financial penalties. However, the limits only consider the emissions from a vehicle during the use phase of its life. A study carried out by the University of California at Santa Barbara (UCSB) on behalf of the WorldAutoSteel group, shows that when the production and recycling phases of a vehicle’s life are included, steel has significantly less environmental impact than competing materials.

The findings of the UCSB/WorldAutoSteel study confirm the results from a life cycle analysis (LCA) of ArcelorMittal’s S-in motion project. The LCA study showed that the use of ultra high strength steels (UHSS) in a typical C-class car would lead to a 15% reduction in greenhouse gases (GHG) emitted during the vehicle’s production and end-of-life (EOL) phases. Emissions are reduced by 14.5% over the vehicle’s entire life, with a drop of 6.2 grams of CO2/kilometre during the use phase (see Figure 1).

 

Figure 1: Contribution of body-in-white and hang-on parts to CO2-equivalent emissions from a baseline C-class vehicle and the S-in motion vehicle (Source: ArcelorMittal)


The UCSB/WorldAutoSteel study found that advanced high strength steels (AHSS) offer considerable reductions in the mass of the body-in-white (BIW) when compared to conventional automotive steels. Over the life of the vehicle, GHG emissions would be 5.1% lower, at little or no additional cost.

When compared to aluminium, AHSS offer savings in both GHG emissions and cost. Over the life of an aluminium vehicle, GHG emissions are 2.6% higher than when AHSS is used and costs are up to 65% higher. Figure 2 shows the variations in costs and emissions between a baseline AHSS solution and an aluminium one.

Figure 2: GHG emissions and costs increase if aluminium is used instead of advanced high strength steels. The baseline for the comparison is the emissions and costs of AHSS. (Source: WorldAutoSteel)


Flawed strategy

Both studies highlight the flaws in the European Union’s strategy to reduce greenhouse gas emissions from vehicle transport. From 2012, a defined percentage of each OEM’s new vehicles must meet emission targets set by the EU. This target will rise each year until 2015, when EU fleet-average emissions must be lower than 130 g of CO2/km for all new cars. Emission reduction targets have already been set through to 2020, by which date the EU expects average emissions to drop to 95 g of CO2/km.

If cost is not an issue, it is relatively easy to meet these targets by using lighter materials such as aluminium and carbon fibre-reinforced polymers (FRP). However, such low-density, GHG-intensive materials may have the unintended consequence of increasing GHG emissions during the vehicle’s total life cycle.

Steel production creates relatively low levels of emissions and, at the end of its life, the steel in the vehicle can be completely recycled without loss of properties. The use of recycled steel to create new steel lowers emissions even further.

Types of emissions

By comparison, emissions from other materials are quite high during the production phase (see Figure 3). Producing one kilogram of aluminium for example, creates between 4.5 and 6.3 times the greenhouse gases emitted during the production of the same quantity of steel. For carbon FRP, emissions are between 8.4 and 11.5 times higher, while for magnesium, emissions are between 7.2 and 22.5 times higher.

Figure 3: CO2-equivalent emissions from the production of materials used in vehicle manufacture (Source: WorldAutoSteel)


The types of emissions are also important. The only GHG emitted during the production of steel is carbon dioxide. Producing aluminium on the other hand contributes perfluorocarbons to the atmosphere, while magnesium is responsible for the emission of sulphur hexafluoride. A full LCA study captures these environmental costs and is the responsible approach to measuring the environmental impact of a vehicle over its entire lifetime.

In an effort to limit the amount of waste going to landfill or incineration at the end of the vehicle’s life, the EU has set a minimum reuse and recycling rate of 85% per vehicle (End-of-Life Vehicles Directive – 2000/53/EC) as from 2015. That target is easy to achieve using steel which is 100% recyclable. However, some materials used for car production are difficult to recycle and must be incinerated or placed in landfill sites.

Using a full LCA approach is the only way for carmakers to accurately measure, and reduce, the total energy consumed during the production, use and recycling of their products. It enables them to implement effective, global solutions rather than quick fixes. Regulatory bodies would do well to adopt the same LCA approach to ensure that their goal of reducing emissions effectively is actually achieved.

The results of these studies confirm that steel has both a bright future in the automotive sector, and an active and vital role to play in preserving the future of our planet.


About WorldAutoSteel

WorldAutoSteel is a consortium of steel companies, established by the World Steel Association, to explore innovative steel solutions for future, low-carbon vehicles. For more information on the consortium and the studies mentioned in this article, please visit www.worldautosteel.org

Source: Update client magazine - November 2011


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