“Cradle to Cradle”: Aluminum’s Green Value Proposition

This article was contributed by the Sustainability Working Group of the Aluminum Associaion in Arlington, Va. For more information, call 703-358-2960 or visit www.aluminum.org.

The Merriam-Webster Dictionary defines the word “sustainable” as “of, relating to, or being a method of harvesting or using a resource so that the resource is not depleted or permanently damaged.” A succinct definition, to be sure—and one that concisely captures the essence of aluminum’s green value proposition.

Aluminum is one of nature’s most plentiful metallic elements, comprising 8 percent of the earth’s crust by weight. Depletion is thus not an issue. Further, the metal’s essential properties make it resistant to the ravages of time, temperature and corrosion, giving it a virtually unparalleled life cycle as a product material. And, at the end of its product life, aluminum can be recycled infinitely, without degradation to its quality, and used anew.

What’s more, aluminum can be recycled using only 5 percent of the energy, and producing only 5 percent of the emissions, compared with aluminum made from virgin ore, providing “cradle-to-cradle” energy and environmental benefits that grow incrementally each time aluminum is recycled.

No doubt, aluminum makes a strong case as a green metal all by itself. So what has the aluminum industry done to enhance its environmental credentials?

Improved smelting practices
Reducing the energy intensity and emissions associated with primary operations has been a focus of the industry for many years. According to the International Aluminium Institute (IAI), the average energy consumption per ton of aluminum production has fallen worldwide by 70 percent over the past 100 years. A century ago, smelters took roughly 28,000 kilowatt hours to produce a metric ton of aluminum from alumina. Today’s smelters use only 13,000 kWh.

IAI further reports that in 2007, over 74 percent of North American primary aluminum was produced using electricity from clean, renewable hydroelectric plants. Worldwide, the figure was 57 percent.

As to reducing emissions, in 1995 12 U.S. primary aluminum manufacturers entered into the Voluntary Aluminum Industrial Partnership with the Environmental Protection Agency, committing to make reductions in two perfluorocarbons (PFCs): tetrafluoromethane and hexafluoroethane—both potent greenhouse gases.

Partners achieved PFC reductions through a mix of management and technological changes, employing the best options on a smelter-by-smelter basis to reduce the frequency and duration of anode effects—temporary electrochemical disruptions in the production process that are the source of PFC emissions.

In the first five years of the program, U.S. primary smelters reduced PFC emissions by 45 percent—equivalent to 2.2 million metric tons of carbon dioxide annually. By 2005, PFC emissions were reduced by 56 percent over 1990 levels.

Aluminum can recycling
Many are familiar with the hierarchy of waste—“reduce, reuse, recycle”—ranking the methods by which the environmental impact associated with production or use of a product can be mitigated. In this regard, makers of aluminum beverage containers have consistently reduced the amount of material and energy used to produce aluminum beverage cans by continually reducing the gauge used in their manufacture.

In the early 1970s, a pound of aluminum yielded 21.75 beverage cans. Today, one pound of aluminum produces 33 cans. Similarly, where a pound of aluminum once yielded 123 can ends, it now produces 165 ends. Notably, while the thickness of the can walls and the diameter of can ends were reduced, both can strength and performance were actually improved while reducing weight by over 30 percent.

While can makers were successfully reducing the amount of aluminum used in cans, the aluminum industry worked to promote the practice of aluminum can recycling. Rather than disposing of their used beverage cans in the trash, consumers were encouraged to collect and return their cans so that they could be routed to scrap processors. Aluminum can recycling quickly became an environmental and economic success. The diversion of cans from the trash preserved landfill space. Consumers were able to earn money for their returned cans. And manufacturers—of both cans and other products—were provided a larger supply of secondary aluminum.

Since 1972, the aluminum can recycling rate has risen from 15 percent to over 50 percent, and the gross tonnage of aluminum cans recycled has increased 35-fold. Today, the aluminum can is the most recycled beverage container, typically containing over 50 percent recycled content.

Aluminum today remains the only material in the consumer waste stream that historically more than covers its own cost of collection and processing. Easily the most valuable material among those commonly recycled by consumers, aluminum effectively subsidizes the recycling of other less-valuable consumer waste materials in curbside collection programs.

Moreover, recycling aluminum provides an “above-ground mine” that serves as a critical environmentally friendly metal supply for manufacturers of all kinds. One-third of all the aluminum on the U.S. market is recycled scrap, which offsets the need for two dozen 400,000-ton smelters that would be required to produce a like amount of the metal.

Lightening autos
Beginning in the mid 1970s, U.S. automakers have been required to meet government corporate average fuel economy standards—fleet-wide fuel efficiency benchmarks. Unsurprisingly, aluminum’s use in vehicles has since skyrocketed.

Since 1974, the aluminum content of U.S. cars has increased in absolute terms each and every year, helping automakers improve gas mileage while increasing the size and safety of their vehicles. Aluminum is now commonly used in a wide range of auto applications—from engine blocks and cylinders to body panels, bumpers and more.

The reasons are obvious. A 6 to 8 percent fuel savings can be realized for every 10 percent reduction in weight from substituting aluminum for steel in auto applications. Further, each pound of aluminum replacing two pounds of iron or steel can save 20 pounds of carbon dioxide equivalents over a vehicle’s lifetime.

With continuing uncertainties over fuel prices, and the prospect of climate legislation, so-called “light-weighting” has become ever more urgent. Announcing the automaker’s “Blueprint for Sustainability” last year, Ford CEO Alan Mulally commented, “Substantial vehicle weight reductions will enable us to use smaller-displacement engines that provide secondary efficiencies, such as lighter chassis and suspension components. They, in turn, will lower vehicle weight even further.”

Via the use of lightweight metals such as aluminum, Ford aims to improve the fuel economy of its vehicles by 40 percent by 2020. To that end, it intends to reduce vehicle weight between 240 and 750 pounds per model between 2012 and 2020.

Automakers such as Ford seeking to light-weight their vehicles received a boost last year when the EPA amended its F019 regulations to encourage

the use of aluminum in vehicles. Announcing the rule change, the EPA noted, “Using aluminum parts produces light vehicles capable of increased gas mileage and decreased exhaust air emissions, including a reduction in the emission of greenhouse gases.”

What is the magnitude of these emission reductions? An IAI study concluded that aluminum applications in light vehicles manufactured in 2006 alone will lead to potential savings of 154 million tons of carbon-dioxide-equivalent emissions and energy savings equivalent to 16 billion gallons of crude oil over these vehicles’ lifetimes.

So great are aluminum’s emission-reduction contributions in transportation applications that the aluminum industry has forecast it will become “greenhouse gas neutral” within the next decade. That is, the global warming impacts of aluminum production will be fully offset by the carbon dioxide saved by its use in transportation applications.

Building a new construction industry
While automobiles’ fuel efficiency has received much attention over the years, the green building movement has been slower to take hold in the United States. That has begun to change with the advent of programs such as the U.S. Green Building Council’s Leadership in Energy and Environmental Design rating system and Energy Star, which promote sustainable building design and manufacturing practices.

LEED evaluates building and site performance using a system in which projects earn points for satisfying specific green building criteria. Given their high recycled content, aluminum building products are routinely used with other recycled materials to earn points toward “LEED certification.”

Just how high is the recycled content of aluminum building materials? A survey of aluminum producers in mid-2008 by The Aluminum Association indicates that the total recycled content of domestically produced flat-rolled aluminum building products is approximately 85 percent. The survey also concluded that, on average, 60 percent of the total product content is from post-consumer sources.

Not only does the aluminum used in the building and construction industry contain a high percentage of both post-consumer and post-industrial recycled content, at the end of its long life it is 100 percent recyclable. Aluminum building components can be repeatedly recycled back into similar products with no loss of quality.

Beyond its recyclability, aluminum stacks up well against competing construction materials in other ways: Its light weight, durability, corrosion resistance and reflectivity all give it an edge in the sustainability stakes.

Consider aluminum roofs. The aluminum shingle—the most common aluminum roof product in residential construction—although generally more expensive than traditional asphalt shingles, offers significant benefits. The lightweight aluminum shingle is easy to install, is typically warranted for two to three times longer than asphalt shingles and, because of its reflectivity (95 percent of all sunlight) can significantly reduce summer air-conditioning use.

Comprised of up to 98 percent recycled material, aluminum shingles, unlike wood shingles, do not dry, split, rot or attract insects. Unlike steel, aluminum shingles do not rust. And unlike asphalt shingles, aluminum shingles do not curl, dry, lift or host moss or fungus. Perhaps most importantly, aluminum roofs are 100 percent recyclable at the end of their lives. Used asphalt shingles, in contrast, are dumped into landfills at the rate of 20 billion pounds per year, according to the National Association of Home Builders.

A sustainable future
These are just a few of aluminum’s sustainable features and applications. Many other aluminum technologies and projects are in the works that will further contribute to sustainable global development.

The Aluminum Association’s Sustainability Initiative, launched last year, is driving a number of these projects. Among them is the expanded Curbside Value Partnership, now in a strategic partnership with Keep America Beautiful, under which the aluminum industry is working with the paper, glass, plastic and steel industries to increase curbside recycling collections. The Aluminum Association has set as its goal the boosting of the aluminum can recycling rate to 75 percent by 2015.

The association is also benchmarking with the IAI and the European Aluminium Association to demonstrate the energy and environmental savings available from the use of auto aluminum.

Perhaps most important, the sustainability initiative aims to communicate the tremendous cradle-to-cradle benefits that aluminum can contribute to help the United States and the world foster ever greater environmental stewardship.

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