• Mark Thimons, President, Sustainability, American Iron and Steel Institute
• Brandie Sebastian, Senior Director, Sustainability, Energy and Environment, American Iron and Steel Institute
• Tim Hill, General Manager, Commercial, Sustainability, Nucor
• Terence Satchell, PE, SE, Commercial Director, Vulcraft/Verco Group

Our experts began by underscoring the sustainability of steel manufacturing, which constitutes around 90% of the cradle-to-gate global warming potential of products made from steel. Brandie says, “The American steel industry has fully embraced the concept of sustainability and made significant progress to reduce energy consumption and the intensity of greenhouse gas emissions for decades now.”

All steel is not created equal, however. Tim says, “Seventy percent of the steel made in the United States uses what we call the circular process, which uses recycled content, scrap and electric arc furnace technology.” The other 30% is made via the extractive process, which has a much higher carbon impact because it begins with mining raw materials and requires far more energy.

The inherent recyclability of steel is another key to its sustainability. Mark says, “All U.S. steel contains some recycled content. When you use scrap to produce steel, you’re displacing virgin iron. One other aspect that gets overlooked is that steel is inherently magnetic, which makes it really simple to recycle.” As a result, steel is recycled at very high rates in the U.S.

Because of the sustainability of steel, using open web steel joists to support long spans or heavy loading with less weight naturally lowers a project’s carbon footprint. Additionally, Brandie says, “We’re starting to see environmental product declarations (EPDs) that summarize life cycle impacts for steel joists. This follows the trend we’re seeing across steel construction products for increased disclosure of company- and facility-specific environmental impact data.”

Even when you’re using steel joists, you need to analyze each steel product separately to get an accurate picture of the project’s carbon footprint. Tim says, “Where the steel’s coming from and all of the steel items that are going into a project, that’s where your carbon savings really add up. Steel joists are one product in a project that could contain a lot of other components with a huge carbon footprint.”

Joist manufacturers are also pursuing other Earth-friendly practices. Terence says, “They’re pursuing efforts like using renewable energy options in production facilities, updating fabrication equipment with more energy-efficient models, and using water-based primers for joists.”

EPDs at the product level and whole-building life cycle assessments at the building or project level are typically used to evaluate the impacts of building materials or products. Brandie says, “Carbon offsets are not currently included in the calculation approaches that are allowable per the ISO standards that govern those approaches. They’re more often used at a corporate level for those purposes.”

Mark adds, “The continued and increased use of facility-specific EPDs is important because they provide a comprehensive understanding of the environmental impacts of specific products.”

It’s important to understand that while there are carbon offsets to address scope one and scope three emissions, there are also renewable energy credits for scope two emissions. Tim cautions, “Sometimes these all get lumped together in the same bucket, and we’re really talking about two very different things.” Consulting with your supplier is the best way to understand how a material’s source influences your carbon footprint.

Architects and engineers should also be aware that European companies do not allow carbon offsets. Tim says, “Renewable energy credits are very acceptable, and, in fact, European companies can even use those as part of how they create an EPD.” EPDs are also approached differently in Asia, so it’s important to understand the guidelines of the market you’re dealing with.

Wood may seem like a good bet for lowering a project’s carbon footprint, but it’s best to proceed with caution. Mark says, “There are a lot of questions being asked about the carbon emissions benefits of wood construction. The claims become especially difficult when you look at significant increases in the use of wood because it’s becoming harder to regenerate forests at a sustainable rate.”

Other considerations include the limitations around recycling wood, which often result in it ending up in landfills, and the cost of the material. Many times, a building scenario using more wood than steel in an effort to lower a project’s global warming potential results in unsustainable costs.

Our experts had one final watchout on the role of wood as part of a sustainability strategy. Tim says, “During COP27, there was a lot of chatter about the legitimacy and the auditability of carbon offsets for scope one, particularly around forestry offsets that have been created and introduced into the market.”

While LEED has been a driving force for over a decade, green procurement frameworks at the state and federal level are becoming more impactful. Brandie says, “These frameworks are setting greenhouse gas emissions thresholds for public procurement of building materials, and there are increasing efforts to incorporate embodied carbon requirements into building codes and standards.”

LEED isn’t disappearing though, and version 5 is expected to contain significant changes. Brandie says, “We anticipate that the latest version is going to focus heavily on embodied carbon and the circularity of building materials. And we believe it’s important for building product manufacturers to begin planning for the development of EPDs for their products that reflect supply chain specificity using data from their key suppliers. Considering LEED and other construction sector activities, these will only increase in importance.”

Aside from keeping up to date on changes to LEED, it’s important to lean on the expertise of your supplier. Terence says, “From our perspective, the key factor we consider in sustainability of construction materials is the transparency of carbon accounting. It’s important to know that the carbon footprint of your building is based on sound assumptions surrounding the carbon emissions of that product.”

Regardless of whether you’re using  LEED or another framework, estimating carbon footprints with an online tool like EC3 can be tricky. Terence says, “There are some hidden nuances. It could be using industry averages, it could be using different rules from different countries, and it may not include all considerations. Speaking directly with your manufacturer is often your best source of information”

While Buy Clean originated in California, the thinking behind it is influencing policies across the country. Tim says, “One of the message points we’re utilizing is it’s not just California anymore, and it’s not just Colorado and New York, but counties and municipalities across the country.”

Steel joists are not covered in any known Buy Clean programs; however, the Environmental Protection Agency included them in a December 2022 interim determination about defining low embodied carbon materials for the United States General Services Administration and the Federal Highway Administration. Brandie says, “We could reasonably expect to see joists included in future green procurement programs.”

Factors in sustainability innovation

Increased funding from public and private sources is helping increase the pace of sustainability innovations, like converting plants to run on hydrogen in place of natural gas. Brandie says, “We’ve heard from our member companies that the money becoming available through the Inflation Reduction Act has helped them expand the scope of projects they already had planned or maybe accelerate the timeline.”

Manufacturers are moving independently to push for innovation as well. Tim says, “Nucor formed a nonprofit group called the Global Steel Climate Council, which includes Nucor, Steel Dynamics and others, calling for policy and standards around a global green steel standard.”

To further boost the use of greener steel, manufacturers would like to see embodied carbon requirements included in future trade agreements and tariffs. Tim says, “We’ve got trade laws that need to be respected and upheld, and embodied carbon content should be included in them.”

What architects and engineers should keep in mind

We wrapped up by asking our experts for their final thoughts.

• Mark: Almost every low-carbon technology, like wind towers, solar arrays and electric vehicles, requires steel. So not only is steel sustainable on its own but it also contributes significantly to the overall decarbonization of society as a whole.
• Brandie: We’re seeing a really exciting amount of innovation as new decarbonization technologies are being developed and becoming viable.
• Tim: The green economy is being built with steel, and the steel it’s built with matters. Really having people understand what we mean by that is very important.
• Terence: When you choose steel, you are investing in an industry that has goals to reduce their carbon footprint long-term.