Reducing greenhouse gases requires a life cycle approach

Posted on 19.01.17 by




With the North American auto show circuit underway, car enthusiasts are looking at a myriad of vehicle features. These include appearance, price tag, gas mileage, technology features and safety ratings. However, a consideration raising eyebrows among the environmentally conscious is a vehicle’s life cycle carbon footprint.

By Brad Davey, chief marketing officer, NAFTA and global automotive at ArcelorMittal

Government regulations have become more stringent in recent years. The 2025 vehicle fleet is required to improve fuel economy and greenhouse gas (GHG) emissions to about 50 mpg. Therefore, automakers have made a number of modifications to vehicles. One is incorporating materials to reduce weight, thereby reducing fuel needs and ultimately GHG emissions. These materials could include advanced high-strength steels (AHSS), aluminum or carbon fiber, among others. Each material contributes to vehicle lightweighting and improves fuel economy. However, each does so at a different cost to the manufacturer – and to the environment.

If we want to know how “green” a vehicle really is, we have to measure emissions over its entire life cycle. This is done using a process called Life Cycle Analysis, or LCA. LCA looks at total emissions generated during the three stages of a vehicle’s life – production, drive phase and disposal.

If we want to know how “green” a vehicle really is, we have to measure emissions over its entire life cycle.

Right now, regulations only consider tailpipe emissions generated during the drive phase of a vehicle. However, the production phase of a vehicle comprises nearly 20 percent of total GHG emissions for internal combustion engines. That figure more than doubles to 47 percent for battery electric vehicles. If we don’t consider production phase emissions when evaluating environmental impact, we may choose lightweighting materials that emit more GHGs during their production than they save during the vehicle’s drive phase. This will result in a huge and irreversible environmental mistake.

In collaboration with Steel Market Development Institute and outside experts, we conducted life cycle analyses on steel. As a matter of fact, there have been numerous scientific studies done in the last decade, including a 2016 Production Phase Emissions study. This study found aluminum produced in North America emits four to five times more GHGs than steel. Additionally, aluminum requires seven times more energy to produce than steel.

Dr. Roland Geyer developed the University of California Santa Barbara Automotive Materials GHG Comparison Model V4, or UCSB Model. This 2007 study calculated GHG emissions and energy over the entire life cycle of a vehicle. Peer-reviewed and publicly available, the study found the majority of aluminum-intensive vehicles result in higher overall lifetime GHG emissions and significantly higher production phase emissions in every vehicle class tested.

The steel industry, while confident with the realistic modeling assumptions employed in the UCSB Model, recognized some might question only using inputs from our industry. The study was therefore broadened in 2016 to include LCA model parameters that, frankly, favored aluminum-intensive vehicles. It also included a “Monte Carlo” assessment which ran the LCA analysis 5,000 times with different parameters, using assumptions from both the steel and aluminum industries. This was a big endeavor – a conclusive effort that hadn’t been run previously.

The findings show steel-intensive vehicles still had lower total emissions versus aluminum in approximately 70 percent of the potential scenarios.

The findings show steel-intensive vehicles still had lower total emissions versus aluminum in approximately 70 percent of the potential scenarios. When we take into account an entire annual fleet of sedans, SUVs or pickup trucks, the aluminum-intensive option versus AHSS results in about 1.5 billion kg more GHGs per vehicle class.


When we look at the disposal stage of a vehicle, steel is recognized as the most recycled material on the planet. One of the most amazing things about steel is that its properties allow it to be recycled continually into any number of products, with no loss of strength or performance. The physical properties of automotive aluminum, however, prevent it from being recycled the same way. Automotive aluminum must be sorted and recycled to the same grade, which is time consuming and expensive.

In their quest for materials to build lighter cars, automakers have grabbed headlines by replacing steel with aluminum. Fortunately for consumers and the environment, however, a wholesale shift to alternative materials is not occurring. Automakers are still capitalizing on the value and performance of advanced steel grades and other technologies to meet regulatory requirements. In fact, AHSS is the largest growing material to replace the traditional mild steels used in the early 2000s.

Sustainability remains a core value to ArcelorMittal and is led worldwide by our 10 sustainable development outcomes. One of these outcomes, “Products that create more sustainable lifestyles,” connects directly with our work in the automotive industry. ArcelorMittal is continuously innovating to release new steel products and solutions that provide strength and mass reduction, while helping to reduce GHG emissions. Steel also provides the best value by allowing automakers to maintain their existing manufacturing and repair infrastructure.

It would be wise for automakers and regulators alike to carefully reconsider alternative material solutions that would likely cause more harm than good to our global environment.