Aluminum: A Sustainable Structural Choice

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Sponsored by CST Covers Industries, Inc.
Celeste Allen Novak, AIA, LEED AP

Sustainability — Industry Research

In September 2011, the Aluminum Association published “Aluminum: The Element of Sustainability” developed by its sustainability group to document the industry’s sustainability achievements over the past two decades. The research also offers a broad overview of the use-phase achievements of aluminum as a sustainable material. Using a life-cycle approach, the report investigates the overall costs and benefits to society of aluminum as a sustainable material. From resource extraction to recycling of a finished product, the report includes charts, tables and comparisons that document the commitment and progress of the North American Aluminum Industry toward sustainable initiatives. 

Among the findings of the report, “Aluminum: The Element of Sustainability,”4 are that since 1991:

  • Primary energy demand associated with primary aluminum production has been reduced 17 percent
  • Primary energy demand associated with secondary aluminum production has been reduced 58 percent
  • Cumulative greenhouse gas emissions associated with primary aluminum production have been reduced 72 percent
  • Cumulative greenhouse gas emissions associated with secondary aluminum production have been reduced 65 percent

This well-documented report quantifies aluminum’s sustainability contributions during the product and end-of-life phases. The Aluminum Association is continuing its research on the life-cycle assessment of semi-fabricated building products that it hopes to publish in the next year.

Aluminum is the third most abundant element on the planet. In the late 1800’s Charles Martin Hall discovered a method to process aluminum using an electrolic process that made aluminum a viable commercial metal. Because aluminum does not lose strength or durability, nearly 75 percent of the aluminum produced then is still in use today. Aluminum has extraordinary value as a building material. When mixed with small amounts of other elements, aluminum can be processed, cast, forged, rolled or extruded into numerous structural forms. It is lightweight and provides the strength of steel at a third to half the weight. Aluminum structural members can span longer distances with smaller profiles. Aluminum does not rust and is corrosion resistant providing a natural oxide coating as a protection against degradation from water, salt, air and temperature variation. According to the sustainability report, “once manufactured, aluminum can be recycled repeatedly, using only five percent of the energy and generating only five percent of the emissions associated with primary production.”5

 

Advances in Resource Extraction and Rehabilitation

In addition to the Aluminum Association reviewing the sustainability practices of it as an industry, the International Aluminium Institute released its Fourth Sustainable Bauxite Mining Report: IV 2008. Aluminum is one of the most abundant metallic elements in the world, the third most abundant of all elements after oxygen and silicon. The industry estimates the aluminum reserves to be able to supply another three hundred years. Most aluminum is a combination of hydroxides and bauxite minerals. Gibbsite, Boehmite and Diaspora are the base raw material for primary aluminum production created as part of a weathering product of low iron and silica bedrock in tropical climatic conditions. The industry has been surveying sustainability and mining practices since 1991. Survey data for the 2006 report covered 66 percent of all major bauxite-mining operations and the 2008 report shows continued substantial improvements in the environmental performance of the industry. 

Bauxite mining requires a small amount of energy when compared to the energy needed to refine aluminum. Diesel fuel (69 percent) and fuel oil (24 percent) are the primary use of energy. Mining operators have adopted several strategies to reduce energy consumption. They have purchased more efficient equipment and trucks, improved the maintenance of vehicles and reduced hauling distances. They have also changed to natural gas where possible from fuel oil as an energy source.

According to this research bauxite mining has a relatively small footprint in comparison to other types of mining. The land area used for Bauxite Mining in 2006 is half the size of Manhattan Island and the industry research shows that the amount of mined area is now equivalent to the amount of rehabilitated area demonstrating a  “land neutral footprint” to Bauxite mining operations. “Reporting mines have plans to rehabilitate more than 90 percent of the total area that was used for bauxite mining and infrastructure since operations commenced almost seventy years ago.”

The rehabilitation objectives can be summarized as follows: “The bauxite mining operations aim to restore pre-mining environment and the respective conditions; this can be a self-sustaining ecosystem consisting of native flora and fauna or any other land-use to the benefit of the local community.”6 Environmental management planning is based on local, national and international standards, practices as well as community expectations.

The respondents to the survey engage an average of twenty-one full time rehabilitation and environmental experts ranging from soil scientists to botanists to provide expertise toward best practice reclamation of mined areas. According to the survey, mining operations generated net social benefits that included:

  • Paid employment under conditions that complied with accepted local labor standards. 75 percent of the total surveyed paid wages at the mines equal to or higher than the national wage average.
  • Education and training programs for employees.
  • Development of local industries and businesses.
  • Support of community initiatives and social activities.
  • Investment in infrastructure.
  • Provision of health and sanitation programs that include malaria prevention and vaccinations.

Approximately 60 percent of the entire workforce is recruited locally. Only three of the fourteen companies surveyed reported any displacement of citizens. Most bauxite operations occur in areas of the world with low density. All of these companies have resettlement programs. Almost eighty percent of the surveyed mines are ISO 14001 certified for environmental management. The International Aluminium Industry (in 1925, the American Chemical Society changed the spelling to Aluminum, and both spellings are in use today) is a strong proponent of sustainable initiatives and continues to document progress by its members for best environmental practices.

Photo courtesy of CST COVERS

Aluminum frame for large solar collector in Arizona.

Engineering, Design and Environmental Benefits

Not every aluminum system will work on every project. The key to engineering and designing aluminum structures is the early involvement of the fabricator. Typical engineering services include preliminary models, renderings, calculations of the reaction loads, etc. In many instances, the fabricator will provide value-engineering services providing insights to the architect as to how to reduce the members of the structural system without impeding the design intent. Sometimes a change as simple as slightly increasing the modular grid to maximize the spanning capacity of the cladding materials can reduce the amount of structure, use less materials, finishes and decrease the cost of the overall structure.

To summarize, the sustainable advantages of aluminum are many and include the following environmental benefits.

  • Design of lightweight clear-span structures that are easy to assemble. 
  • Creation of open and column free flexible spaces that maximize daylight transmittance.
  • Strength to weight ratios that will not decrease when aluminum is recycled into new products.
  • Effective use of geometric properties to reduce material waste.
  • Elimination of secondary framing members.
  • Reduction of maintenance and increase in longevity because of the non-corrosive properties of aluminum.

The use of aluminum is increasing throughout the world for many uses. It is ideal for beverage containers and has contributed to the reduction of emissions and transportation costs as a component in automobile manufacturing. As a building material, aluminum provides many benefits to the designer, particularly the designer who uses geometry as a design element. Choosing aluminum as the structure for these new geometric forms and spaceframes reduces material consumption and has numerous environmental benefits. As more and more designers learn how to design for disassembly, aluminum products will continue to evolve and be re-used for centuries as a sustainable, durable building material.

ENDNOTES

1 http://www.aluminum.org/Content/NavigationMenu/TheIndustry/SheetPlate/
LEEDFactSheetForAluminuminBandC/LEED_Fact_Sheet_8_13_08.pdf
2 http://leedcasestudies.usgbc.org/overview.cfm?ProjectID=1721
3 Ambrose, James and Tripeny, Patrick. Building Structures, John Wiley & Sons, p.36.
4 http://aluminum.org/Content/ContentFolders/Miscellaneous/
Aluminum_The_Elemen.htm
5 Ibid. Pg. 5.
6 http://www.world-aluminium.org/cache/fl0000292.pdf

 

Architect Celeste Allen Novak AIA, LEED AP specializes in sustainable design and planning in Ann Arbor, Michigan.

CST COVERS INDUSTRIES, INC. CST Covers is a global design/build firm with expertise in high-strength aluminum signature solutions such as spaceframes, domes, environmental enclosures, canopies, large span, and specialty lightweight structures designed for unique eco-friendly vertical and overhead applications.  www.cstcovers.com

 

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