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EMBODIED CARBON INTENSITY DIAGRAMS

ECID: COMPARISON OF LCA TOOLS

There are many differences between the LCA tools used to generate the ECIDs.  This section is focused on the aspects of the tools that were deemed most relevant to have affected the differences in results. 

The LCAs were originally performed with the versions of the LCA tools current as of late 2022. In the course of reviewing the results for the commentary, we updated some of the results using later versions of the tools. 

X = Automatically Included

See Reference below for each numbered note

Reference
 1) The Athena data used for these analyses are from multiple versions of Athena.
2) For B1-B7, some of these tools have the option to include inputs for these impacts, but were not utilized for these analyses.
3) Most material data does not include waste processing, but “avoided burden” methodology data for metals includes waste processing effects, though it is not reported separately in Module C3.
4) For A5 (installation energy and water consumption), tallyLCA asks the user to input these values manually.  One Click LCA automatically includes material wastage impacts and allows the user to input construction site operations manually when utilizing the Life Cycle Carbon tool. Construction site operations are often excluded in practice.
5) The One Click LCA analysis used the One Click Life Cycle Carbon Tool.
6) For C1 (deconstruction & demolition), One Click LCA allows the user to choose pre-set demolition scenarios based on square footage when utilizing the Life Cycle Carbon Tool.

Life Cycle Stages A1-A3

Athena IE

Athena databases are typically built from the ground up using actual mill or engineered process models. (7) There are regionalized assumptions for certain Canadian and US cities.

tallyLCA

tallyLCA

Relies on the 2017 GaBi background Life Cycle Inventory (LCI) database from Sphera (formerly Thinkstep). It contains mostly industry average data with some manufacturer specific EPDs that have been analyzed by Thinkstep. Database contains North American average values and has no regionalization, though transportation distances can be customized (different default values are assumed for each material).

One Click LCA

One Click LCA

Has the largest global LCI database consisting of mostly publicly available manufacturer-specific and industry average EPDs with EPDs using both GaBi and Ecoinvent as their background LCI data. One Click LCA also generates its own generic data for a wide range of construction processes using Ecoinvent as the upstream LCI database. It makes regionalized assumptions for Canadian provinces and US states.

Reference

7) Athena Sustainable Materials Institute. (2019, May). User Manual and Transparency Document, Impact Estimator for Buildings v.5.

Life Cycle Stage A4

Athena IE

Athena IE

Transportation distances and modes reflect regional averages and are not editable in the database.

tallyLCA

tallyLCA

Transportation distances and modes are auto-generated by the software and they are editable by the user. 

One Click LCA

One Click LCA

Transportation distances and modes are auto-generated by the software and they are editable by the user. 

Life Cycle Stage A5

Waste

Waste

  • Athena IE
    • Material waste factors are included in the overall material quantities, so not reported under A5. 
  • tallyLCA
    • Material waste factors are not included by default and must be added manually by the user.
  • One Click LCA
    • One Click LCA automatically includes the impacts of material waste based on unique waste percentages assumed for each type of material and the designated end-of-life scenario. Waste default values are set based on typical wastages, and they vary based on construction process, building and design. Waste factors may be modified manually by the user

Construction Impacts

Construction Impacts

  • Athena IE
    • Athena accounts for energy consumption and emissions associated with on-site construction activities. For some materials, construction impacts are estimated using the energy required to lift materials into place.
  • tallyLCA
    • Construction site emissions may be included if manually inputted by the user.
  • One Click LCA
    • Construction site emissions may be included if manually inputted by the user.

Life Cycle Stage B

Note

The use stage was excluded from our analyses due to the assumption that the structural system will not require significant maintenance, repair, replacement or refurbishment during the building’s useful life.

Life Cycle Stage C

Wood Product

Wood Product Summary
Tool Incinerated Recycled Landfilled – decomposed Landfilled – stored permanently Source
Athena IE 10% 10% 18.4% 61.6%

Woodworks Article

(2023 version)

(8)
tallyLCA 22% 14.5% 31.75% 31.75% Woodworks Article
One Click LCA (9)

100%

(default)

 0% Woodworks Article

Steel (W shapes) Product

Steel (W shapes) Product Summary
Tool Recycled Landfilled Source
Athena IE Not Available Not Available
tallyLCA 98% 2% (10)
One Click LCA9

100%

(default)

Steel Decking Product

Steel Decking Product Summary
Tool Recycled Landfilled Source
Athena IE Not Available Not Available
tallyLCA 98% 2% (11)
One Click LCA (12)

100%

(default)

Reinforcing Steel Product

Reinforcing Steel (rebar) Product Summary
Tool Recycled Landfilled Source
Athena IE Not Available Not Available
tallyLCA 70% 30% (11)
One Click LCA (12)

100%

(default)

Concrete Product

Concrete Product Summary
Tool Recycled Landfilled Source
Athena IE Not Available Not Available
tallyLCA 55% 45% (11)
One Click LCA (12)

100%

(default)

 

Reference

8) In December 2023 Athena released a new version of Impact Estimator that changed the biogenic accounting. The information provided in this table is based on the previous version of the software that was used for this ECIDs study and is no longer publicly available. The Woodworks link provided here applies to the new version of Impact Estimator. The figures provided in the table are based on an earlier version of the Woodworks overview.

9) For One Click LCA, the Expert-level license allows the user to adjust the end-of-life scenario from a list of preset options. The information represented in the tables above are the default end-of-life scenarios.

10) University of Oregon Department of Architecture & Environment, Clackamas County Courthouse Life Cycle Assessment of Architectural Concept Designs, August 2020.

11) University of Oregon Department of Architecture & Environment, Clackamas County Courthouse Life Cycle Assessment of Architectural Concept Designs, August 2020.

12) For One Click LCA, the Expert-level license allows the user to adjust the end-of-life scenario from a list of preset options. The information represented in the tables above are the default end-of-life scenarios.

Module D

The three tools vary widely in their approach to Module D.

Athena IE

Athena IE

    • Wood
      • Athena IE reports biogenic carbon in Module D.  See Biogenic Carbon section for details.
    • Steel
      • The end-of-life calculations for steel products follow the World Steel Association “avoided burden” methodology. If the assumed recycling rate is higher than the recycled content in the form of scrap used in the product, a “credit” (negative GWP value) is given in Module D. If the recycling rate is less than the assumed recycled content, a “burden” (positive GWP value) is added in Module D. Thus Modules A-D results can show higher embodied carbon impacts than Modules A-C results.
    • Concrete
      • No Module D impacts for concrete.

tallyLCA

tallyLCA

  • Wood products have negative GWP in Module D unless Biogenic Carbon is accounted for, in which case they have positive values in Module D (overall A-D impacts are still negative). The uptick in Module D is due to biogenic carbon leaving the system due to recycling, energy recovery, decomposition, etc. When biogenic carbon, typically stored in wood or other organic materials, is released during decomposition or combustion, it contributes to the overall carbon emissions in this phase.If the materials are incinerated or biodegraded (instead of being sequestered in a landfill, for example), they release stored carbon back into the atmosphere, increasing emissions in the A-D phase.
  • Steel products, with the exception of rebar, have negative Module D GWP values (credit).
  • Concrete has small positive GWP values in Module D (burden).

One Click LCA

One Click LCA

    • Module D impacts are dependent on the end-of-life scenario chosen. 
    • For the default end-of-life scenarios, steel and wood yield net-negative Module D impacts (credits) while concrete yields net-positive Module D impacts (burden).

Biogenic Carbon (13)

Athena IE

Athena IE (before v. 5.5)

    • By default, Athena Impact Estimator considers biogenic carbon but does not report the individual biogenic carbon flows that occur in each life cycle stage. Instead, Athena IE reports the amount of permanently stored biogenic carbon (i.e., carbon that is permanently stored in the landfill at the end of life) in Module D. 
    • If a user runs only Modules A-C, excluding the impacts of Module D that are outside the system boundary, biogenic carbon is excluded from the reported global warming potential (GWP). However, if a user runs Modules A-D, including biogenic carbon, the results include Module D impacts of other building materials besides wood. In order to capture only the biogenic carbon impacts of the wood products without the Module D impacts of other materials, the user should run Modules A-C for all building materials and then run Modules A-D for the wood products only. The impacts reported in Module D for the wood products can then be added to the A-C analysis for all materials to obtain a GWP value that includes biogenic carbon effects. (Version 5.5 of Athena Impact Estimator, released in December 2023, resolved this issue by reporting biogenic carbon in the appropriate life cycle stage instead of as a lump sum in Module D.

tallyLCA

tallyLCA

    • Biogenic carbon enters the system in A1 and some biogenic carbon leaves the system in A3.
    • tallyLCA reports only the emissions associated with landfill and incineration in Module C1-C4. Biogenic carbon that leaves the product system due to recycling is reported in Module D. Module D also includes other benefits and impacts such as energy recovery and use of that energy to offset energy from the grid (based on US national average electricity grid carbon intensity), not shown. It is difficult to disaggregate this data to determine only the portion of biogenic carbon that leaves the system through recycling to be passed on to the next system.
    • When biogenic carbon is excluded in tallyLCA, no credit is given in Module A1 for the biogenic carbon stored in the log when it enters the system. Similarly, when wood products leave the system or are incinerated, biogenic carbon emissions are not reported; however, biogenic methane emissions from landfill decomposition are still reported. Likewise, because biogenic carbon flows are not reported, there is no permanent biogenic carbon storage when the user chooses to exclude biogenic carbon.

One Click LCA

One Click LCA (14)

    • One Click LCA calculates the amount of biogenic carbon stored in the wood products but does not report biogenic carbon flows over the full life cycle, nor does it include biogenic carbon in the overall GWP. Biogenic carbon enters the system in A1 and some biogenic carbon leaves the system in A3. In Module C3, the default assumption is that 100% of biogenic carbon within the system is emitted. In other words, One Click LCA does not include any permanent biogenic carbon storage, regardless of whether the default or a custom end-of-life scenario is used. Because One Click LCA does not include biogenic carbon in the reported GWP, biogenic carbon flows (-1 in/+1 out) are not reported within each module. Rather, the amount of biogenic carbon stored in the wood products is reported separately in Modules A1-A3 and is assumed to be stored for the life of the building.
Reference

13) WoodWorks. (2024, January). Biogenic Carbon Accounting in WBLCA Tools.

14) One Click LCA. (2024, August). Biogenic Carbon.

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