End-of-life vehicle process flows with process-specific product outputs. Click to enlarge.

We set out to detail exactly how aluminum is separated and recovered at the end of a vehicle’s service life and findings show it is highly recyclable and is recovered and reused at very high rates. With an eye toward reducing the nation’s energy consumption, lowering carbon emissions and increasing fuel economy, this study confirms that as aluminum use continues to grow in the automotive sector it also enhances energy security and environmental protections.

—Professor Diran Apelian, founding director of WPI’s Metal Processing Institute

The researchers used a grave-to-gate process material flow analysis (PMFA) approach to determine the recycling rate of automotive aluminum/aluminum alloy metal units. Three operations contribute to the total aluminum metallic loss to the landfill after an automobile enters a dismantling operation:

• shredding;
• downstream separation; and
• scrap melting.

The amount of material processed through this system reaching the gate of a new life cycle is not compared to an input value to the PMFA system because end-of-life vehicles and automotive aluminum scrap are exported so frequently and these values are not monitored accurately for the entire market in the US. In other words, this study does not utilize a mass-balance analysis. The amount of end-of-life vehicles that retire on an annual basis is only used in this study to determine the market share covered by each survey respondent and the market share of the respondents as a whole. The recycling rate is determined by combining a material collection rate with the recovery process efficiencies as applicable to the material that flows through each step in the recycling process.

—“Automotive Aluminum Recycling at End of Life”

Aluminum use in cars and trucks continues to rise and has seen consistent growth during the last 40 years, in part, because of its consumer and environmental benefits. Recycled aluminum helps automakers improve the sustainability of their operations and products, while also providing supply chain security. Once produced, aluminum can be recycled repeatedly without any degradation while maintaining significant economic value. As a result, automakers can tap an endlessly renewable supply of aluminum through closed-loop recycling operations. (Earlier post.)

Among the more specific findings of the study was that the weighted average material collection rate for end-of-life vehicles that flow through a dismantling operation and a downstream separation system is 99.7%.

The major detriment on the automotive aluminum recycling rate derives from the recovery processes. When a heavy gauge scrap class is charged, referred to in this study as a heavy recovery process, a metal yield of 95% is attained. Light gauge scrap melting is estimated to result in a metal yield of 91%. The majority of automotive aluminum is charged as a light gauge, mixed, shredded scrap. It has been estimated that 86% of obsolete auto-aluminum is charged in this form.

Current data commissioned by the Aluminum Association confirms the energy needed to produce primary aluminum is down more than a quarter since 1995 with carbon emissions down nearly 40% due to expanded use of hydroelectric power sources for aluminum production.

In an independent life cycle assessment conducted by the US Department of Energy’s Oak Ridge National Laboratory, use of aluminum in new vehicles to boost fuel economy was found to offer the smallest total carbon footprint among competing materials. (Earlier post.) A similar assessment conducted by Ford Motor Company and Magna International arrived at the same conclusion.