Processed and stacked redwood lumber at mill in northern California
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Structural engineers play a large role in material development and specification. Currently, third-party sustainability certification systems are available for wood. However, there are no comparable systems for other building materials. The industry is moving toward a more sustainable approach to building design and reviewing the overall lifecycle impact of buildings. Therefore, it is important that we review all aspects of our building’s environmental impacts. As more sustainable building materials are introduced into the market, it is important that we provide a proper vetting system for these materials. A third-party certification system similar to what is currently in place for the wood industry, would provide this tool.

Wood certification
Currently the United States has two primary certification systems for wood, the Forest Stewardship Council (FSC) and the Sustainable Forestry Initiative (SFI). The wood certification process generally includes third-party auditors, a chain of custody standards, independent governance, and on-product labeling. Some of the positive changes that resulted from third-party certification of wood products are that the wood industry has created a more sustainable future for itself, improved public opinion and provided differentiation opportunities for sustainable suppliers. While the wood industry provides one example of certification, other building materials should be individually evaluated to determine the best approach for a certification system.

Concrete
Concrete is one of the most widely used building materials in the world – its use has doubled in the last decade. Cement is by far the biggest contributor in terms of energy and CO2 emissions, accounting for 90 percent of energy consumption. However, in addition to the cement that is used in concrete, the environmental impacts of the aggregates, sands and admixtures that make up the concrete mix must be included. Often, aggregates and sands are be transported large distances, which must be considered as part of the material’s environmental impact. Finally, concrete mix plants need to be considered as well, as they are the final step in the chain of custody. Through use of more supplemental cementitious materials, improved quality control and use of renewable energy, plants can improve their total environmental impact.

Table 1: Concrete fuel consumption per cubic yard.

Material

MBtu/yd3

% of Total

Cement manufacture

0.622

87%

Aggregate production

0.021

3%

Transportation

0.054

7%

Plant operations

0.020

3%

Initially, it is expected that upgrading to newer technologies would have a financial impact on the industry. However, a study conducted at Lawrence Berkeley National Lab found that concrete mix plants could reduce their energy consumption by as much as 65 percent and save roughly $1.1 billion annually. So while initial investment is required, the final product would have positive results – both financially and environmentally.

Steel
Steel is a largely recycled material, a concept that is generally used to promote steel as a "green" material. However, the production of steel, both international and domestic, is very energy-intensive and has a big environmental impact. There are two common types of steel production used in the world today: The blast oxygen furnace (BOF) and the electric arc furnace (EAF), which is more common in North America. The BOF process requires about 21 MMBtu per ton of steel, while the EAF process, which uses mostly scrap material, uses about 9 MMBtu per ton of steel. Studies have shown that through increased maintenance and implementation of newer technologies, as much as 3 MMBtu can be reduced per ton of steel, a total of a 10 to 30 percent reduction for the EAF process. There is also much room for improvement in energy efficiency of fabrication plants. Additionally, it is important to consider that the recycled content of steel is largely dependent on the availability of scrap material. As scrap materials become scarcer, more reliance will be placed on virgin ore, a material that requires intensive mining and heavy processing, which has a large environmental impact.

Multiple trade organizations in existence could partner to develop a third-party certification system, including AISC and the World Steel Organization. Perhaps the biggest advantage of steel certification is that it would provide manufacturers with the opportunity to differentiate themselves from their competitors. Certification would allow producers to be recognized for their commitment to sustainable practices and allow them to price their product in a manner that reflects the increased cost of implementing green practices.

Conclusion
In addition to traditional design decisions, structural engineers can play a large role in reducing the environmental impact of building materials, provided the appropriate tools are available. As has been shown in the wood industry, LEED and other green building codes can adopt and encourage these systems, creating a demand and having a positive impact on the industry, while advancing environmental stewardship goals. By enabling owners, structural engineers and builders to select and specify products that meet stricter environmental protection requirements, an independent third-party certification system will bring us one step closer to true sustainable design.

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For additional information on this topic, please see the full version of the committee’s paper on the committee’s web page at www.seaonc.org The SEI Sustainability Committee website is http://www.seisustainability.org/.

Lindsey Maclise, P.E., LEED AP, is a project engineer at Forell/Elsesser Engineers in San Francisco. Maclise is also a member of the SEI Sustainability Committee. She can be reached at L.Maclise@forell.com.
Allen Nudel, S.E., LEED AP, is a principal with Forell/Elsesser Engineers in San Francisco. He is the co-chair of the Structural Engineers Association of Northern California Sustainable Design Committee with Maclise. He can be reached at A.Nudel@forell.com
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