Let's have a look at the CO2 values if an SUV steel body was replaced by aluminum.
According to the German Federal Ministry of Economics and Climate Protection (2021), the steel industry is the sector with the largest share of greenhouse gas emissions in industry. It is responsible for around 30% of industrial emissions and around 6% of total emissions in Germany. This industry therefore has a special responsibility in climate protection. At the same time, it is clear that steel will remain a key basic material in the future, whether for wind turbines or in the automotive and construction sectors.
Therefore, we asked ourselves the question: What if steel is replaced by another metal, such as aluminum? What impact would this change have on the carbon footprint of car bodies and how relevant are recyclates in this comparison?
It should be noted that for 1 kg of steel, approximately 2.75 kg of CO2e is emitted, while for one kg of aluminum, almost three times that amount is generated. However, aluminum is lighter than steel and this affects the overall weight of the vehicle and therefore its fuel consumption and associated CO2e emissions.
In our SUV example, an aluminum body would save about 0.3 liters of fuel per 100 km compared to a steel body due to its lighter weight. On the other hand, fuel-related CO2 emissions would be 12.6 kg CO2 per 100 km for an aluminum body, compared to 13.5 kg CO2 per 100 km for an aluminum body. However, considering that the production of aluminum generates more CO2e than the production of steel, the result is not so clear-cut and depends strongly on the mileage.
Simplified, we can say that just as much CO2e is generated in the production of steel as in the case of aluminum from recyclate, or about 2 kg of CO2 per kg of aluminum or steel. This means that the recycled variant is more sustainable in any case.
Aluminum is significantly more expensive than steel, however, if steel is replaced by recycled aluminum, the CO2e balance of the SUV is better due to the lower weight. In addition, the use of recycled material is an important step for a circular economy and thus contributes to waste prevention. So, once again, the PCF analysis has enlightened us on the environmental impact of such changes.
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