Non-GWP environmental impacts - issues with CLT/Glulam?

Hi Jeremy, We’ve seen similar issues in our studies, and while I can’t offer a definitive answer on this, I can offer how we’ve come to look at the problem. The issue stems from the wildly different processes involved in the creation of these materials – farming vs mining, different types of manufacturing. I admit we haven’t been able to find at what point the additional impacts are caused in the CLT process – if it’s the glue part of the process or the growing portion – but my hope would be regardless of where the impacts occur, we can push for better alternatives. Better farming practices and better glues. Something else to consider is that there’s no inherent equivalent to the impacts. There’s can be orders of magnitude difference in the results, and there’s no great way of comparing what a kilogram equivalent of one type of impact will have over the kg equivalent of another impact. Some of these have global effects, some of these have local effects. Comparing the effects requires some sort of normalization and weighting factor, and there are different groups out there that have attempted this. These factors vary depending on the source, but the CLF LCA practice guide (https://carbonleadershipforum.org/lca-practice-guide/) has a few that the CLF has confidence in on page 28 of the guide. Our personal feeling is that mass timber offers a better solution than concrete and steel at this point, but we’re keeping an eye on these other effects and using this as a guide to push our material procurement and to promote better product development. -Justin Schwartzhoff, LMN Architects From: Jeremy Shiman

Hi all, We've seen these differences in our practice as well. How we choose to interpret this type of result is to say - great, we've lowered GWP...now are there swaps we can make that are GWP neutral that allow us to reduce our impacts in these other categories?  For example, galvanization tends to increase your EUP - are there places that you are using galv that don't actually need it?  Our general feeling is that, yes, climate change is the most pressing issue, and therefore the first determining factor...but that it can't be the only one, or we will make some unfortunate substitutions. While we also (like Justin!) are pushing for timber as a replacement for concrete and steel wherever we can, we are also trying to identify other material categories BEYOND structure that are major contributors to eutrophication and acidification - such as roofing products, flooring, and insulation - in order to identify ways to offset the increase we see in those categories when we have a preference for engineered timber.  -Efrie Escott, KieranTimberlake

Jeremy -  Chiming in to say "me three". I recently drafted a memo to GBCI about this issue (that Justin co-signed), and am attaching it here. Highlights:

• The structure of the LEED impact reduction credit may disincentivize teams from using mass timber as a substitute for non-wood products such as concrete and steel due to observed relative increases in non-GWP impacts in timber buildings (when using Tally to document and compare impacts)
• Non-GWP impacts' increases are tied to the amount of wood in the design.
• Although adhesives in a laminated timber product like CLT likely contribute to increases in non-GWP impacts, their contribution does not 'make or break' the overall outcome - all impact categories except GWP increase even when adhesive-less wood substitutes concrete/steel

My hypothesis on why this is happening is that wood products interact with global nitrogen and phosphorous cycles during the product stage - in short, unlike most other building materials, wood literally grows in soil and water. So when you even have a little bit of this unique material in your design, you see huge swings in non-carbon-related impacts. But that's just a hunch. I'll build on Efrie here - maybe one way to restructure the LEED credit is to say "demonstrate a reduction in GWP first, and then other categories optionally". Will keep you updated on GBCI's response -

Bio based building products really should be certified from environmental positive regenerative farms.  Otherwise, the release of nitrogen, the fertilizer and phosphorus run off to create hypoxia, etc., need to be weighed against carbon benefits for holistic environmental impacts. Same for many other systems, e.g. ground source heat pumps, the holistic LCA environmental impact can be more or less than air sourced heat pumps, pending on different elements, including the life cycle (usually ground source heat pumps loops are longer than air source heat pumps), the carbon benefits also need to be weighed against holistic environmental impacts.   See selected studies further below: We likely need holistic impacts, EPD and beyond, to understand whether we have acupuncture, or, simply needles that hurt, when erects anthropogenic order into the terrestrial environment. https://www.sciencedirect.com/science/article/abs/pii/S0960148122002233 https://rshare.library.ryerson.ca/articles/thesis/Comparative_life_cycle_assessment_ground_source_heat_pump_system_versus_gas_furnace_and_air_conditioner_system/14665932

We also have a project that is using CLT and we found a similar issue with the Eutrophication while doing our WBLCA. We haven't submitted for the LEED credit yet, and am glad to see this thread.  Alex and Justin, thank you for submitting the memo to GBCI, I would love to know what they conclude. 

New here (hi everyone!) and really appreciate this discussion. Even as someone whose work mostly revolves around climate change, I share the feeling that a focus on carbon shouldn't blinker us to the range of other impacts. Echoing others here, I think LCA provides a unique opportunity to look across life cycle environmental impacts.  When we consider comparing between impact categories to privilege one over another, TRACI guidelines enumerate that "since each impact category has different units it is not appropriate to simply look at the values of each impact category and determine from this point which impact category is of most concern." There's also a warning against these weightings written into ISO 14040: "there is no scientific basis for reducing LCA results to a single overall score or number, since weighting requires value choices." I don't mean to trot out the guidelines to defer to their authority, but to illustrate an important point they're making--focusing on GWP is, in part, a value judgement. As someone whose work is almost entirely focused on climate change, I see wbLCA as an important chance to take a wider view: the climate crisis is also a biodiversity crisis, the upstream/downstream human health impacts are often also environmental justice issues, and the fragile ecosystems where material extraction happens are often in the global south.  Current LEED language asks that a project targets reductions in multiple indicators, one of which must be GWP. Given the urgency of climate change and the need to avoid trade-offs, this seems reasonable to me. One issue here is that communication around the significance of indicators other than GWP is lacking. Their names don't roll off the tongue, the units are wonky, and they're not as much in the public consciousness.  Regarding the specific issue around timber, I wonder if it's worth taking up with industry groups, Woodworks or similar. Seems like a great opportunity for a wood product manufacturer with regenerative practices to distinguish themselves with a product-specific EPD!   

Hi all, We have also been having this problem when comparing a concrete/steel baseline to a CLT and glulam structure. The guidance we got from LEED is that it is ok to have a hybrid baseline so we have been running our baseline model with some CLT in it which helps balance out the extreme increases in the other environmental impacts. However, I’m not in favor of manipulating the baseline building to be in our favor as a final solution, but it also feels like we are being questionably penalized for end-of-life scenarios of other environmental impacts that seem very difficult to accurately predict and quantify. I’m looking forward to the conversations happening with GBCI to try and figure out the best solution! One of the things I have found in our research with a recent project is that most of the increased environmental impacts for eutrophication and acidification come from the end-of-life stage. In our LCA study, we used Tally and studied the cradle to grave impact of the structure only. The building life is set to 60 years. The project SF is 34,438. We compared a concrete/steel baseline structure to our design which is primarily CLT and Glulam and these are the results we got organized by life cycle stage (I also attached an excel sheet):   EUTROPHICATION (kgNeq) comparing baseline to timber design [A1-A3] Product – 20% increase [A4] Transportation – 990% Increase  [B2-B5] Maintenance and Replacement – 55% Decrease [C2-C4] End of Life – 5,420% Increase [D] Module D – 76% Increase Full Life Cycle – 439% Increase   ACIDIFICATION (kgSO2eq) comparing baseline to timber design [A1-A3] Product – 2% decrease [A4] Transportation – 990% Increase  [B2-B5] Maintenance and Replacement – 69% Decrease [C2-C4] End of Life – 1,031% Increase [D] Module D – 66% Increase Full Life Cycle – 77% Increase   As you can see, there is a glaring increase at the end-of-life stage for both impacts, as well as some in the transportation stage. My inclination is that the increased impact in these other environmental impact categories is due to the assumptions made in Tally about wood going into the landfill – “65.5% of wood is sent to landfill, 17.5% to incineration, and 17.5% to recovery.” Has anyone found research on end-of-life scenarios that might help inform why there are such negative environmental impacts at this stage and what we can do to mitigate them? Or if this is only a concern because of the assumptions made by Tally and it wouldn’t be that bad if the wood was re-used or processed differently? We are still looking into what might be the cause of increased end-of-life impacts. Also, Is anyone seeing a large increase in other environmental impacts at the product stage or through EPDS, or is it when looking at the full life cycle impact? Best, 

Hi all - Reviving this conversation as it is relevant to the LCA outcomes for several of our current Mass Wood projects. @Alex Ianchenko, how was your memo to GBCI received?