Quantifying uncertainties in absolute environmental sustainability assessment: A general framework applied to French electricity production

Assessing the environmental performance of products and systems from an absolute perspective, in relation to the Earth's carrying capacities, is highly uncertain. This is mainly due to value-based choices that must be made to downscale carrying capacities to the assessed activity, often making assessment results highly dependent on one's interpretation of distributive justice. We present a framework for evaluating uncertainties in the downscaling of carrying capacities in absolute environmental sustainability assessment (AESA) of products and systems. The framework considers 19 possible approaches to share carrying capacities, grounded in four theories of distributive justice (like egalitarianism and utilitarianism) and seven enacting metrics, such as final consumption expenditure or prior emissions. Application to French power using the PB-LCIA impact assessment method showed that impact scores were statistically significantly higher than the downscaled carrying capacity (i.e., frequency of no-transgression ≤0.95) in seven out of ten planetary boundaries. For example, the median biosphere integrity impact score with a 90 % uncertainty interval was 0.0081 (0.0047–0.012) % of biodiversity intactness index (BII) loss, as opposed to the median downscaled planetary boundary equal to 0.0032 (0.00032–0.017) % BII loss, corresponding to a frequency of no-transgression equal to 0.21. This highlights the need to consider uncertainty in AESA of products and systems for more robust quantification of their performance, and setting better-grounded reduction targets.