IMPACT World+ 2.1

New indicators:

• Plastic physical effect on biota
  This new indicator measures the effect of plastic resins emitted in the water environments (both freshwater and marine) on biota, in PDF.m2.yr. It also comes with a midpoint indicator in CTUe. This indicator is the result of the work of the MariLCA working group [https://marilca.org/characterization-factors/]
• Fisheries impact
  This new indicator measures the impact on biodiversity of fisheries activities. It is only assessed at the ecosystem quality damage level (in PDF.m2.yr). This is based on the work of Stanford-Clark et al. [https://doi.org/10.3390/su16093870]
• Marine & terrestrial ecotoxicity
  In the v2.1 we decided to finally integrate these two ecotoxicity indicators, at the damage level only. These are based on an old version of Usetox (v2.02). As the v3 of Usetox is on the verge of being released, all ecotoxicity and toxicity categories will be updated in the next version of IW+.
• Photochemical ozone formation
  For this impact category, IW+ adopts what the ReCiPe methodology recommends. In their 2016 update [https://doi.org/10.1007/s11367-016-1246-y], ReCiPe renamed the indicator "Photochemical oxidant formation" to "Photochemical ozone formation". In addition, they calculated the impact of this category on ecosystem quality. There are thus two corresponding impact categories at damage level: "Photochemical ozone formation, human health" and "Photochemical ozone formation, ecosystem quality"

Updated indicators:

• All climate change indicators
  IMPACT World+ v2.1 proposes the carbon neutrality approach (i.e., CO2-bio = 0) as well as the -1/+1 approach (CO2-bio uptake = -1 / CO2-bio release = +1). However, the latter is only available in the expert and midpoint versions. In the footprint version, the carbon neutrality assumption is still being used.
  Furthermore, we added CFs for temporary storage of biogenic carbon that can be used (e.g., Correction for delayed emissions, carbon dioxide, biogenic).
• Climate change, human health
  In the v2.0.1, we updated the GWP100 and GTP100 indicators following the recommendations of the AR6 from the IPCC2021. Now in the v2.1, we are also updating our damage indicators for climate change to follow the AR6 recommendations. Notably, the cumulative AGTP500 used in the derivation of these CFs was recalculated with updated equations (which we obtained thanks to Yue He and Thomas Gasser from the International Institute for Applied Systems Analysis - IIASA). In addition, the effect factors were also updated. Previously it was based on data from the World Health Organization from 2003, it is now based on the WHO 2014 report as well as the work of L. Rupcic (https://backend.orbit.dtu.dk/ws/portalfiles/portal/329521472/PhD_Thesis_Lea_Rupcic.pdf).
• Climate change, ecosystem quality
  Similarly to the human health indicator the cumulative AGTP500 were recalculated. However, the effect factor was not updated yet for this impact category.
• Particulate matter formation
  Those CFs were updated to the latest model from Fantke, et al. This is composed of a series of articles on updates to fate and effect factors [https://doi.org/10.1021/acs.est.9b01800 / https://doi.org/10.1021/acs.est.7b02589
  This model now provides regionalized characterization factors per town of more than 100,000 inhabitants. The CFs at the town-level are available in the source file, but in the dev file and in the different software versions, we only provide national/regional (e.g., RER) as well as global values, aggregated from the town-level factors.
• Water availability, human health
  Those CFs were updated to the latest model of L. Debarre (2024). This model includes a harmonization of methodology between the domestic and agriculture water use, updates the exposition factors using the latest Gross National Income data and updates the EF. Overall, the values of the characterization factors of this category have dramatically decreased, by a minimum of 65%.
• Water availability, terrestrial ecosystems
  While the original value of the characterization was not updated (e.g., 0.21 PDF.m2.yr in Netherlands), the regionalization was updated based on an estimation of depths of groundwater, based on Jasechko (2021) [https://doi.org/10.1126/science.abc2755].
• Water scarcity
  Those CFs were updated to the latest update of the AWARE model Seitfudem (2024).
• Fossil and nuclear energy use
  The HHV values were updated to match the updated HHVs in ecoinvent.
• Ozone layer depletion
  Those CFs were adapted to match the latest data from the World Meteorological Organization (2022) [https://ozone.unep.org/sites/default/files/2023-02/Scientific-Assessment-of-Ozone-Depletion-2022.pdf]. In addition, the time horizon has now been extended to the infinite instead of limiting it to 500 years.

Methodology

For more detail on the methodology behind each impact category, refer to Github: https://github.com/CIRAIG/IWP_Reborn/tree/master/Methodology

Corrections

In this section we only provide information on the major corrections that were made. For a full report of all the changes please refer to https://github.com/CIRAIG/IWP_Reborn/tree/master/Report_changes

• There are challenges associated with using IMPACT World+ files across databases or software for which they were not specifically designed. For instance, this is why we now provide files adapted to particular ecoinvent versions in brightway2. Similarly, both SimaPro and openLCA periodically update the names of their elementary flows. When an impact assessment method has previously been imported into one of these tools, an embedded procedure in their update processes is supposed to adjust the characterization factor names in line with the new flow names, ensuring compatibility with the updated list. However, we lack detailed knowledge of this procedure, meaning we cannot guarantee that the updated versions of IW+ in these tools would align with our specific modeling choices. Likewise, the IW+ versions we provide for a given release of SimaPro or openLCA might be incompatible with previous or subsequent versions due to discrepancies in flow names and characterization factors. Consequently, users of these software should verify which flows are characterized and make adjustments if necessary.
• Harmonization of regionalized flows
  Regionalized impact model do not operate at the same geographical granularity. In the previous version, some flows were characterized in one impact category but not in the other. For instance, the flow "Water, lake, US-TRE" was characterized for the "water scarcity" indicator but not for "Water availability, human health". All regionalized flows are now characterized for all the impact categories they affect. This is also true for the newest regionalized impact category (Particulate matter formation) where SO2 for example is regionalized at a much more granular level than in the freshwater acidification impact category.
• Fossil and nuclear energy use
  For the SimaPro version of the v2.0.1, some flows that only exist in SimaPro were not characterized, such as "Oil, crude, 43.4 MJ per kg". Now they are properly characterized using the energy content value specified in the name. Results obtained with SimaPro will thus differ from results obtained with brightway2 and openLCA, since the latter do not use such flows and only use flow such as "Oil, crude".
• Thermally polluted water
  In the v2.0.1, the flows "Water, turbine use, unspecified natural origin" were not linked to the correct proxy, which meant they did not impact the Thermally polluted water category, which underestimated the impact of this category.
• The problem of "Nitrogen"
  "Nitrogen" can mean two different things. It can literally mean the "N" element, but it can also mean the "N2" molecule. The issue is that it is not clear in the LCI databases, which meaning does "Nitrogen" have. Previously, our understanding was that "Nitrogen" meant "N" but since then, ecoinvent notably, added formulas to the elementary flows they provide and associated the formula "N2" to their "Nitrogen" flows, indicating that they understand it as "N2" and not "N". Furthermore, in SimaPro and openLCA, the associated CAS number is generally "7727-37-9" which again corresponds to "N2". Thus, we now consider that “Nitrogen” represents dinitrogen, and thus does not impact the "Marine eutrophication" impact category anymore. We also corrected a previous mistake: N2O is not characterized anymore for this impact category.

IMPACT World+ 2.0.1

• Create of the footprint version of IW+
• Update to IPCC2021 AR6 for midpoint categories
• Creation of an unspecified land type CF for land use categories

IMPACT World+ 2.0

v2.0

Small readme update.