WBLCA - eutrophication impacts of wood

I don't have any insight on how USGBC would address this, but this recent discussion on the CLF forum looks relevant: https://community.carbonleadershipforum.org/t/what-the-heck-is-a-kg-of-n...

We have seen similar results in our WBLCAs when comparing buildings that primarily use timber to those framed with other materials. We have seen this across multiple WBLCA programs, though to varying degrees. We have also seen increases in some of the other impacts. The total % increase, and if it becomes problematic to the language of the LEED credit, tends to depend on the specifics of the entire building and other assemblies.

I agree that the lack of specific data complicates this issue, but I’d also be surprised if reviewers saw it as reason to exclude an increase in a certain impact category.  Similar issues exist with other materials related to industry average data vs “best performers”, as well as with comparisons between assemblies. If exceptions are granted based on general trends but without specific data, then the question becomes where to draw the line.

Perhaps this issue can be used to help illustrate the need for more supply chain specific data that quantifies the benefit of specific forestry and manufacturing practices? I know that this may not help for the specific LEED points for a specific project, but with the 4.1 revisions the WBLCA would at least provide 1 point.

I am doing a WBLCA using Tally for a project that is primarily glulam and CLT. When compared to our baseline building that is concrete and steel, we are also seeing a large increase in eutrophication and acidification way above the 5% threshold limit for LEED. It mainly looks like this is due to the CLT during the end-of-life stages. Has anyone stumbled upon best practices for addressing how to lower eutrophication and acidification whether that is through changing our baseline model, or substituting in more accurate CLT data that reflects the specific EPD's we are using? So far, we have found the only way to meet the credit is to include CLT in our baseline model, or other materials that are high in eutrophication and acidification. In addition, has anyone found ways when specifying products to not only lower GWP impact but eutrophication and acidification as well if the results due conclude that timber products are much worse than concrete in these impact categories? Thanks, 

Hello Kate, Did you submit your WBLCA project for LEED Review? I am also working on projects that is using CLT and Glulam. When comparing  proposed wood based building with baseline concrete and steel, I am seeing a large incerase in eutrophication. As you said, this is coming mainly from end of life scenario. Can you share your learning from the project? 

Related question about Eutrophication: I got a comment from USGBC about a LEED submission about the etrophication reduction being more than 70%, that it is atypically high, and to provide a narrative explaining why or adjusting analysis. I know eutrophifcation generally increases when comparing a wood design with concrete/steel, but I am not comparing structures with any wood. I am using One Click LCA for the analysis/comparison and when I try to dig into it, I think I see it's coming from the rebar and metal deck. I did a test of using the same rebar and metal deck EPDs for both the baseline and the as-designed LCA and the reduction between the two got even greater! 80%! 

I am no scientist and don't understand what may or may not impact eutrophication directly, and/or how to justify to USGBC of the resutls. Do you have any thoughts? Any insight would be appreciated.

Hi Jaclyn,

I recommend you ask this to One Click LCA help desk as well, but it is really hard to say without looking at your inputs to find the culprit. There might be a typo in the numbers input somewhere or a material selection that looks like the same but is different.