To validate our Exiobase implementation, we compared Earthster’s results against the EXIOBASE-ImpactWorld+ (IW+) benchmark. The EXIOBASE-ImpactWorld+ benchmark contains the official ImpactWorld+ characterization factors adjusted for EXIOBASE exchanges. The table below shows the relative difference between Earthster and EXIOBASE-ImpactWorld+.
Legend: Values represent the relative difference as a percentage (0% = identical results; 100% = maximum difference).
Indicator | Mean Difference (%) | Mode Difference (%) | Maximum Difference (%) |
Fossil and nuclear energy use | 90.0% | 92.2% | 100.0% |
Mineral resources use | 77.6% | 75.5% | 100.0% |
Photochemical ozone formation | 12.2% | 0.0% | 99.9% |
Marine eutrophication | 4.0% | 0.0% | 56.6% |
Freshwater acidification | 2.9% | 0.0% | 66.1% |
Terrestrial acidification | 2.2% | 1.4% | 48.6% |
Particulate matter formation | 0.4% | 0.1% | 26.2% |
Climate change (long/short term) | < 0.1% | 0.0% | 5.2% |
Freshwater eutrophication | 0.0% | 0.0% | 0.0% |
Land occupation (biodiversity) | 0.0% | 0.0% | 0.0% |
Human toxicity (non-cancer/cancer) | 0.0% | 0.0% | 0.0% |
Water scarcity | 0.0% | 0.0% | 0.0% |
Ionizing radiations | 0.0% | 0.0% | 0.0% |
Land transformation | 0.0% | 0.0% | 0.0% |
Ozone layer depletion | 0.0% | 0.0% | 0.0% |
Analysis of Divergences
While the majority of categories show a near-perfect match (less than 2% difference), there are specific areas where Earthster results intentionally differ from the benchmark.
Resource Scarcity (Fossil and Mineral)
The significant divergence in these categories is due to two primary factors:
Unused Extractions: The reference IW+ implementation maps "unused domestic extraction" flows as if they were useful resources. We have unmapped these to prevent the artificial inflation of resource scarcity.
Fossil Fuel Proxying: The reference implementation uses a mapping for generic fossil fuels with an energy value of 9.9 MJ/kg, which is on the lower range of energy content of fossil fuels. Our implementation utilizes a 32 MJ/kg proxy (anthracite coal), which serves as a more representative and conservative midpoint for global energy extraction.
Emissions and Acidification
For categories including Freshwater/Terrestrial Acidification, Marine Eutrophication, Particulate Matter, and Photochemical Ozone Formation, the differences are caused by a mapping error in the reference benchmark, whereas emissions of Phosphorus to soil are characterized as if they were emissions of Nitrous oxides to air.
Climate change
Climate change emissions are consistent with Earthster’s results, but in some datasets impacts may be up to 5% higher than Earthster’s. That’s because in the ImpactWorld+ Exiobase benchmarks CO released from Chemical wood pulp is treated as fossil emission rather than biogenic.