Embodied vs Operational LCA ghg emissions messaging..?

Is anyone out there actually seeing LCA’s show closer to a 50/50 split on embodied vs operational on high performance buildings that move towards electrification, renewable energy, and clean grids?

Because this seems to be the messaging Architecture 2030… :

or CLF’s graphic showing embodied being the heavy dominator, like this:

I post this because due to some amazing LCA and research work by @lkaufman and me (#humblebrag) - we have not seen high performance building profiles shift the total ghg emissions towards embodied.

We still very much see an operational dominating emissions profile on a number of low EUI buildings, EVEN ones that lean towards electrification, on-site renewable energy, and have future grid cleaning scenarios. Even with a concrete/steel structure, our last LCA was showing an 80/20 split towards operational on a grid that is cleaning now and supposed to be zero-carbon by 2050.

What is everyone else seeing?

-Scott

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Hi Scott,

It’s a good question, with regional answers based on the grid, the speed at which is gets renewable and what is considered in your embodied scope.

In our Path To Zero Carbon Series, we show a (mostly) Mass Timber building in a very clean electric grid with an overwhelming majority of emissions from embodied, admittedly a bit of a unicorn. It’s the third graphic down.

https://lmnarchitects.com/lmn-research/03-toward-zero-carbon-architecture

We looked at the 13 projects reported for the 2021 AIA 2030 reporting cycle, and here is the number of years before Annual Energy Use Carbon is greater than Embodied Carbon. This includes structure, envelope, most interiors, plus a simplistic +60MTCO2e/m2 for MEP.

Infinite, infinite, 41, 29, 23, 14, 13, 11, 7, 7, 7, 6, 3.

If we use the Cambium 2040 Blended data for energy use carbon decreasing over time, we get:

Infinite, 70, 48, 39, 32, 28, 27, 25, 24, 23, 15, 12, 4.

So with a 30-year timeframe and Cambium energy data, a 50/50 average is not that far off, though with significant deviation.

-Kjell

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Hi Kjell -

Appreciate the detailed response.

Granted our embodied carbon scope doesn’t cover all interiors and MEP, even if we bumped it by 25% (going from 4,000 metric tons CO2e to 5,000), it has a pretty small increase to the overall footprint, which is about 17,000 metric tons CO2e.

We are talking about 12,000 metric tons CO2e operating emissions on a 100,000 gsf higher educational building with a design EUI of 33 across 60 years on a grid that is putting a significant amount of renewables online in 2025 and shooting for zero-carbon by 2050.

Our major take away is: the grid isn’t cleaning fast enough to cut down operational emissions.

And my major take away from your ‘number of years before operational is greater than embodied’ above, is that if you cannot design to zet-zero energy on year 1, the operational is going to blow out the embodied within a short timeframe.

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One of the common assumptions among designers that I see while working on projects, even the high performance ones that are aiming for Arch 2030 targets, is that low EUI means low emissions. In the past, we didn’t often take the extra step to analyze the regional grid mix, so the actual emissions remained hidden. Traditional LEED (v4 and earlier) calculations reinforced this bias with energy savings measured in cost. So we’re making sure now to do the “extra” step to reveal the full picture. I’m sure this is common knowledge among the forum…just sharing here that a lot of designers stop at EUI. We need to go much further in our analysis as a rule to understand buildings’ impacts beyond the property line.

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One other important factor in this discussion is reference period. If you’re only looking at the first 5 years of a building’s operation, embodied emissions will dominate. The longer the reference period, the more we’ll see operational emissions dominate. This is obvious, of course, but I mention it to get at an important difference between the CLF and Architecture 2030 graphics in the first slide–the CLF describes a single building over a single reference period (probably 60 years?), but the Architecture 2030 graphic describes all building-related emissions between 2020-2050. This means that the longest reference period for a building captured in their analysis is 30 years (buildings built in 2020), but most will be much shorter (the reference period for a building built in 2049 is two years). This, I expect, explains some of why their result skew toward embodied emissions in a way we might not imagine at first glance.

Following up on Kjell’s point about “significant deviation,” here’s a graphic I prepared for a recent webinar about exactly this. Note that the embodied carbon estimates here includes replacements, another twist in the effect of reference period on the operational/embodied split. Still, very wide deviation by geography. These models were built in EPIC, using the Cambium mid-case data over a thirty year reference period, and conservative assumptions for embodied carbon (~960 kgCO2e/sf).

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Hi Jack - In our specific case, looking at the first 10 years, it was still a 60/40 split towards operational.

Dirty grid is dirty, even with a low EUI building.

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Scott,

Are you looking at static emission numbers comparing embodied vs operational emissions? If so, this isn’t taking into account the time value of those emissions. When comparing embodied and operational emissions - or really, any emissions over a time scale - looking at ton-years may be a more relevant metric for the atmospheric impact of those emissions across your timeframe. For example, 1000 kg CO2e emitted from A1-A5 activities persists in the atmosphere (mostly, with some decay, depending on the chemical), continuing to act as greenhouse gasses throughout the 10 year window. Ignoring decay and simplifying for the sake of example, at the end of that ten year period, the embodied emissions will equal 10 ton-years. I expect this may change the math in your analysis.

I’m not a dynamic LCA expert by any means, so if someone out there wants to push back or clarify this, please jump in. My understanding is that when emissions are released and how long they act as greenhouse gasses in the atmosphere is critically important for emissions accounting over time, and this is of particular importance when valuing the reduction potential of carbon storing materials and comparing embodied and operational emissions that occur over time.

Cheers,
Jacob

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The time value is a useful point here. I had a post recently on carbon storage of wood products and was trying to get at the same concept. There’s very minimal benefit to carbon storing materials if you can’t account for the time value of carbon/ delayed emissions. This isn’t captured in LCA so needs to be conveyed in a qualitative manner.

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I agree, Lauren. How is delay a benefit?

If we are serious about carbon reduction (and it appears much of the world is getting there), then I can only imagine that the end of life for wood is not going to be decay. We definitely need to have figured this out 60-100 years from now. Are there other ways of talking about or quantifying the benefits of delay?

Also agree with Lara – we need to use carbon emissions + energy instead of just energy when we reduce our footprint from operational energy use. We are starting to use NREL Cambium.

Jacob, my understanding is that if you look long term, when you emit carbon doesn’t matter much in most cases (please respond if you think otherwise). CO2 will last centuries, CH4 will be mostly depleted in 20, but the warming and other effects from both will last longer. If you have a deadline, like “stay under 1.5 by 2050” then you can use ton-years. The problem is that we really have a budget for the total tons of CO2e, not a timeframe. Or rather the timeframes for global CO2e emissions are generated by paths that meet the global carbon budget, not the other way around. Staying under 1.5 determines a total budget, and the budget determines the timeframe. The global carbon budget for 1.5 appears to be around 340-400 GT CO2e and we are emitting around 60 GigaTons of CO2e/year.

To bring this back to the question at the top of this email, delay is only a benefit under a few conditions as I see it:

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I don’t want to minimize the important of upfront/embodied carbon, because we are all here on this forum discussing it for a reason. But this discussion (and my recent LCAs) really reinforce to me how critical it is to get our energy sources under control, especially if we are approaching this from a total CO2e budget perspective…

And if on-site renewable isn’t an option for a project, then we are left to the mercy of the grid… which is unfortunately outside of our control.

Cue the hopelessness feeling.

Just to throw one more concept into the mix for this great holistic discussion - the embodied carbon of our renewables is not zero, and in fact is sometimes not showing as paying for itself (carbon wise) in a low energy house for a long long time (See Bronwyn Barry’s presentation on the PH Ribbon from the recent NA Passive House Network Conference).

I see a lot of scary language out there from proponents of the status quo who say we need to mine too much new material for our renewables. I think its less than they say, but we desperately need to keep all of our currently available precious metals out of the landfill and ramp up recycling programs of all electronics etc…

Cue the fire in the belly feeling! :wink:

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Agree, Sara. There is embodied carbon in electricity-generating infrastructure whether we build it as part of a project or not.

This is the best study of the embodied energy of electricity-generating infrastructure I’ve found, showing that renewables have a smaller percentage of their energy that is outside the typical boundary set for carbon emissions.

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I only skimmed this thread after the first post, but if I’m following correctly, then I can add some further input:
We regularly see full LCAs, where the grid decarbonisation is considered in line with the conservative version of the latest UK Future Energy Scenario decarbonisation pathway; and the conclusion is consistently showing embodied as significantly larger than operational impact over a 60 year reference study.
My experience may be biased though, as we’re doing studies on buildings with ambitious EUI targets, driven by planning requirements and sustainability accreditation (e.g. NABERS).

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Hi Mike -

Thanks for your input.

Here are 2 plots from our study:
-The top being the final design that was an adaptive reuse, reusing much of the existing structure, but still providing additional concrete/steel, and enclosure improvements
-The bottom being a hypothetical new build, that demo’d the existing, and rebuilt everything from scratch
-Zero Carbon Grid by 2050 (with incremental reductions in-between now and then, but starting at 1300 lbCO2e/MWh)
-33 EUI (kbtu/sqft/yr)

Again - my takeaway is even with a grid that is decarbonizing, a (mostly) electrified building on a dirty grid will emit A LOT of ghg emissions up until the zero-carbon point, enough to tip the scale. Too much has been emitted by the time the grid reaches zero-carbon.

So I think we’re commonly seeing ambitions for much more efficient operational performance than yours (33kBTU/sqft/year = ~100kWh/m2/year; we’re talking 55kWh/m2/year, looking at the base build)

And our grid is currently less than half that carbon intensity, if we’re to believe UK grid data; 1300lbCO2e/MWh = ~590gCO2e/kWh, whereas UK grid carbon intensity in the next few days is averaging 230gCO2e/kWh See live tracker: Carbon Intensity

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Hi Mike -

Agreed that your EUI is more ambitious, but your grid is even more ambitious. Welcome to the Midwest, United States, where operational ghg emissions dominates your buildings wbLCA.

Updated takeaway: context matters.

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Haha, “context matters”, definitely!

I wouldn’t say the grid is ambitious though – it is indeed lower than what you’re dealing with :slight_smile: But same point persists: We are seeing embodied becoming more important – dominant even in some cases – and that’s because of a milder climate/lower EUI, and much lower grid carbon intensity.

Best of luck :slight_smile:

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Sounds like a good study, it’s important to give our clients the best available, regionally relevant info on carbon emissions. And 33 is a good EUI as well, much better than many buildings, so energy-related carbon emissions may be underreported in many cases compared to your study. As a reference for everyone else, the US average GHG is in the 800s, well below the 1300 lbCO2e/MWh dirty grid in the study. https://www.epa.gov/egrid/power-profiler#/ You can find your region easily in the link.

As another reference, the US electricity grid has decreased carbon intensity by more than 35% since the peak around 15 years ago.

https://www.c2es.org/content/u-s-emissions/#:~:text=U.S.%20net%20emissions%20declined%2013,a%20leveling%20of%20electricity%20demand.

We need urgent action on all strategies, embodied and operational. For energy, we need ‘efficient electrification’ that includes heat pumps (2x-3x more efficient than electric resistance or gas, sometimes up to 6x) to reduce carbon emissions from electricity.

-Kjell

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Agreed, Kjell. Nice summary!

The man-contributed CO2 in the atmosphere may be about one part in ten thousand of the atmosphere. This is supposed to be increasing the heat in the atmosphere by capturing solar energy re-emitted by the earth, that is not already being captured by the other CO2 present in the atmosphere, and then transferring that heat to the other 9,999 particles that surround each of these particles of CO2, while heating them by a significant amount.

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