Proposal for a new normalization reference in LCA based on “safe operating space”: presentation of framework and global factors at midpoint level

Planetary boundaries have been suggested for a range of environmental impacts,such as climate change, eutrophying nutrients and land use. The boundaries demarcate the safe operating space of humanity: Staying within the space ensures environmental sustainability, while exceeding it risks pushing ecosystems into alternative regimes, leading to adverse effects for humanity. Planetary boundaries can be applied as policy targets. To promote a societal development in the direction of these targets, an indicator system is needed that measures the fraction of the safe operating space that a given activity occupies. We propose that such an indicator system can be applied in life cycle assessment (LCA) by integrating planetary boundaries via the normalization step. We present the framework of integration, a literature review of quantified boundaries and resulting normatively consistent global average normalization factors in units compatible with characterized results at midpoint level in LCA. Our suggested framework allows expressing normalized results in units of “sustainable person years”. Normalization factors are derived by dividing the safe operating space by the global population. The proposed normalization factors were compared with existing normalization factors that are based on global impacts currently taking place. The impact categories climate change, land use and terrestrial acidification were found to have their safe operating space exceeded on average globally, while the opposite was true for the remaining six categories assessed. Additional research is needed with respect to spatial differentiation since the derived global normalization factors have reduced environmental relevance for impact categories operating at the regional or local scale. Nevertheless the developed normalization factors represent an important first step in enabling LCA to help guiding society in the direction of staying within the safe operating space.