As we seek to reduce the EC content of our buildings and structures, one of the target areas that structural engineers must work with the whole design team to address is that of materials specifications. There is much we can do to leverage the way we specify materials sourcing, refining, and manufacturing to make a big impact. This, of course, requires ‘buy-in’ from other members of the process - manufacturers, contractors, and Owners among others.
How are you specifying your materials to reduce carbon content? Are you, for instance, requiring steel from EAF’s as opposed to, say, Blast Furnaces. What about SCM’s in grout for CMU?
Are you finding the supply chain and other design and construction team members are responsive? What challenges have you encountered in changing your specifications and/or making them more stringent?
The first step towards reduction is measurement, so short of getting material reductions (more optimized spans to reduce total material, specify maximum cement content for concrete, hot-rolled steel from EAFs rather than HSS’s from BOFs, FSC certified wood), structural engineers can track material quantities and ask for product-specific EPDs of the structural materials.
EPDs: Even if the material supplier is unable to produce an EPD, it’s at least worth bringing up. I’m currently in a policy-focused role where I’m talking to suppliers about EPDs and they’re hesitant about the importance of EPDs because nobody’s asking for them! Structural engineers can ask for EPDs in their specs, and if they can’t be produced then ask for a letter explicitly saying they cannot produce an EPD. Gotta start the conversation somewhere
Quantities: If you’re tracking quantities, you’re a hop, skip, and a jump away from an LCA. But with just quantities you can get (rough) embodied carbon assessments with something like SE 2050’s ECOM tool. This is often more internally focused, but it’s a great step in the right direction.
@martintorres - Thank you for your response! I agree, and our company (the one I’m with) needs to get going on calculating quantities and doing takeoffs, ideally in conjunction with our Architectural clients to get a whole-building view of the matter.
EPD’s are a great thing to put into the specifications for your projects. I firmly believe that if we, as an industry, start asking, we will start a trend. As you say, “nobody’s asking for them.” But we as an profession now know better.
Beyond EPD’s, has anyone on this Forum had contact with suppliers about specific manufacturing processes and emerging technologies for concrete, masonry, and steel production that can reduce EC?
@brian.mcsweeney Others on this thread may be able to comment on specific manufacturing processes and emerging technologies for cement, masonry and steel. But for energy efficiency opportunities ENERGY STAR Energy Guides have a lot of content. Here are the links:
@martintorres and others: In practice, how common is it for an EPD to differentiate between steel originating from a plant that uses an EAF versus one that uses BOF? If the EPD is produced by a steel fabricator (for example, the plant that transforms the steel to rebar, plate, etc.) the steel input could have come from a separate plant. Is it common to just include the industry average, which may mask the environmental attributes of steel from an EAF vs. BOF, or have EPDs included a more precise value?
Ideally you’re getting product-specific EPDs, so it’d be specific to that plant and supply chain, though industry-average EPDs or material baseline values are commonly used in LCA. I haven’t looked at many steel EPDs, but I suspect if it’s coming from an EAF they would want to brag about that in their product description in the EPD.
We’re lucky in the US that EAF’s are the dominant producers of steel (about 2/3). Regardless, an easy proxy for EAF vs BOF is specifying certain shapes that typically come from EAFs (hot rolled shapes like W’s, L’s, channels, rebar) vs shapes that come from BOFs (HSS, deck).
For steel from a manufacturing perspective, there are a lot of strategies in the works - hydrogen or biofuel replacement of fossil fuels, carbon capture and storage retrofits of steel production, more electrification (EAFs) and decarbonizing the grid, early retirement of BOFs and biomass substitution for coke for existing BOFs/DRI. But these are often costly or difficult, so without strong policy incentive and pending further R&D, it may be tough to shift the practice. Using higher grade steel is also great because it doesn’t really increase impacts and you can use less total material!
For concrete since it’s all about reducing cement, there are definitely some low hanging fruit without needing a product-specific EPD (though that’s still an important ask) - use portland limestone cement rather than portland cement, be more conscious about your cure times and don’t just use 28 days arbitrarily (foundations can often sit there for a while), specify maximum cement content lower than the NRMCA baseline in your region, use CarbonCure, SCM replacement (but keep in mind it’s not about % replacement but about total cement content). There’s also exciting new stuff like blue planet aggregate, but I don’t think that’s been used on a very wide basis beyond a small handful of projects in the Bay Area where they’re located. Not sure if that’s the answer you were looking for, but those are common strategies for reducing concrete impacts.
Yes, emerging technology is driving change for structural materials and reducing embodied carbon in that process. Adoption is a large disconnect from where I stand. Innovative technology like PrimX reduces portland demand in the overall design by 8-12% on top of harnessing the full thickness of a slab for strength by eliminating shrinkage and curling. End results achieve greater strength, thinner profile, and an average of 40% reduction in carbon emissions when compared to a traditional 7"+ slab on grade design. Is reducing the required quantity of high carbon materials not as good as reducing the carbon content of those materials? Obviously, reducing both is the long-term goal but an existing solution capable of a 40% reduction seems like tremendous progress. See attached for a more in-depth analysis of the carbon reduction via Technology (PrimX). Destree+X.+and+Pease+B.+2013.+In+proceedings+of+ICCS13.pdf (366.1 KB)