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ORNL study finds aluminum-intensive vehicles can deliver up to 29% reduction in CO2 emissions compared to typical steel-bodied vehicle

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Lifecycle energy findings. Source: Sujit Das, ORNL. Click to enlarge.

A lifecycle study of aluminum-intensive vehicles by Sujit Das at Oak Ridge National Laboratory (ORNL) found that an aluminum-intensive vehicle can achieve up to a 32% reduction in total lifecycle energy consumption, and up to a 29% reduction in CO2 emissions, compared to a typical vehicle on the road today which uses traditional and high-strength steel in the body construction.

The study, underwritten by The Aluminum Association, performed a full cradle-to-grave analysis (primary metal production; autoparts manufacturing and assembly; use; semi-fabrication material production; transportation; and end-of-life metals recycling) on three modeled vehicle types: a baseline steel vehicle; a lightweight steel vehicle (LWSV); and an aluminum intensive vehicle (AIV).

Although a lightweight steel vehicle has a lower production phase environmental impact, those initial gains are erased by higher energy use and carbon emissions during the steel vehicle’s use phase, the study found. More than 90% of automobile energy consumption and carbon emissions occurs during the use phase, with the mining, production and manufacturing phases accounting for just 10% or less.

For an aluminum intensive vehicle, the breakeven point in its use phase for making up the energy consumed during the initial production phase is 9,300 miles (15,000 km), when compared to the baseline vehicle—a milestone most automobiles on US roads would reach in their first year of operation. Compared to a lightweight steel vehicle, the breakeven point is at 27,340 miles (44,000 km)

For the AIV, the breakeven point in CO2 emissions comes even sooner: at 1,864 miles (3,000 km) compared to the baseline vehicle and at 21,748 miles (35,000 km) for the LWSV.

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Source: Sujit Das, ORNL. Click to enlarge.

As the US works to reduce dependence on foreign oil, promote clean energy and combat climate change, this report definitively documents why aluminum offers the most promise for cutting total automotive-related carbon emissions and energy use.

—Sujit Das

The ORNL study modeled a typical 2012 crossover SUV reflective of the average on-the-road vehicle in the US in terms of weight, performance, fuel economy and materials mix of steel, high-strength steel and aluminum.

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Lifecycle environmental impacts for a baseline SUV, a lightweight steel vehicle, and an aluminum-intensive vehicle. Source: Sujit Das, ORNL. Click to enlarge.

Building on an earlier crossover SUV study by the United States Environmental Protection Agency (Light-Duty Vehicle Mass Reduction and Cost Analysis — Midsize Crossover Utility Vehicle, Aug 2012), ORNL researchers analyzed a baseline SUV (a comprehensive mix of mild and high- strength steel); a lightweight steel vehicle (optimized for maximum use of high-strength and advanced high-strength steel); and a lightweight aluminum intensive vehicle (including currently available body, doors, trunk and hood applications).

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LCA functional unit materials for each of the three configurations. Source: Sujit Das, ORNL. Click to enlarge.

The modeling for this study conforms to internationally recognized standard practices (ISO 14040 and 14044). Comparative data sets used in the study were provided directly to ORNL researchers by the US steel and aluminum industries respectively, both sets of which are current, peer-reviewed and publicly available.

The ORNL study is consistent with an earlier independent study by the magnesium industry which also concluded that aluminum has the smallest carbon footprint of competing materials when examining total lifecycle CO2 emissions.

In addition:

  • Using aluminum to reduce vehicle weight across the world’s overall transportation fleet could reduce greenhouse gas emissions by 660 million tons annually, representing 9% of transportation-related emissions.

  • Recycling aluminum saves 95% of the greenhouse gas emissions associated with primary aluminum production, and requires only 5% of the energy.

  • Nearly 90% of automotive aluminum is recovered and recycled.

  • Aluminum is recycled without degradation to the material.

Comments

HarveyD

This is even better than the claimed 15% to 20%.

Aluminum + light composites could do even better whenever the cost is right?

Trevor Carlson

Then again... steel is a moving target and has by no means run out of innovations keeping it relevant and very competitive.

http://news.thomasnet.com/green_clean/2013/09/06/advanced-materials-for-lightweighting-cars-whats-new-in-steel/

ai_vin

Now who would have ever thought that a study, underwritten by The Aluminum Association, would come to such conclusions?

I'm not saying it's wrong, in fact there are very good reasons to believe it's all true, but I'd still like to know that safeguards were in place against confirmation bias.

HarveyD

Very good point ai_vin.

Most paid studies (100%?) are biased towards the hand who pays the bill? Those that are not, are never published?

Lucas

Good point guys; I thought the same thing.

There are a number of good reasons for not using Aluminum. One is its strength to weight ratio. Another is the cost.

I strongly suspect that autos are evolving in the direction of composites. I've been wasting my time trying to get auto builders to think of how the bodies of animals are built and to design autos using natures well established principals.

Innovation; That's what we need. Build a car skeleton out of Carbon Fiber. Flesh it out with EPP and cover it with a tough, lightweight skin.

Unfortunately, Automotive Engineers aren't capable of even thinking in those terms. Since they hold the reins, we'll just have to squirm and wait.

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