We’ve seen EEIO data from EPA and CMU showing GHG impact of about 0.35 kgCO2e / USD. This is a spend-based methodology. When using OCLCA or AthenaIE we get around 0.85 kg/CO2e / USD for the same project. Any idea where this difference originates? I suspect lots of ESG reporting platforms for GHG Protocol Scope 3 utilize the EEIO factors - but no direct experience on that front. Thank you!
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Correct that most ESG platforms are using the spend-based EEIO numbers. In the GHG protocol, embodied carbon falls under scope III: capital assets. Two things potentially driving the difference come to mind -
The first potential driver of the observed difference is that EEIO factors include impacts that map most closely to A1-A3 (though not exactly overlapping), where One Click or Athena cover all life cycle phases.
The second potential driver behind the difference might be the level of specificity. The EEIO factors are a crude national average–like they stirred every relevant building and renovation in the country together into one big pot and then portioned it out a dollar at a time to assign impacts. Athena has a more refined set of assumptions based around a specific building in a specific place.
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Thank you Jack. I wonder does the WBLCA community have data normalizing GHG by project cost? This would provide a larger sample for testing the IO estimates. I can’t find research on this topic in the literature.
For some of our clients this is a considerable portion of reported impact. We would like to advise them if transition from spend-based to WBLCA methodology will be a GHG penalty. And help promote more accurate methodologies as best practices.
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Absolutely! We’ve had similar conversations where friends/clients expand their GHG Protocol reporting scope to include capital assets and are blown away by the impact. Harmonizing the methodologies to get wbLCA into scoped reporting seems complicated but, in my mind, very much worth it for the window it gives into what carbon reductions can look like.
In the peer-reviewed literature, hybrid EEIO/LCA approaches have been common for a while. Will be interesting to see how they come into practice in AEC.
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