Introducing carrying capacity-based normalisation in LCA: framework and development of references at midpoint level

Abstract

Purpose There is currently a weak or no link between the indicator scores quantified in life cycle assessment (LCA) and the carrying capacity of the affected ecosystems. Such a link must be established if LCA is to support assessments of environmental sustainability and it may be done by developing carrying capacity-based normalisation references. The purpose of this article is to present a framework for normalisation against carrying capacity-based references and to develop average normalisation references (NR) for Europe and the world for all those midpoint impact categories commonly included in LCA that link to the natural environment area of protection. Methods Carrying capacity was in this context defined as the maximum sustained environmental intervention a natural system can withstand without experiencing negative changes in structure or functioning that are difficult or impossible to revert. A literature review was carried out to identify scientifically sound thresholds for each impact category. Carrying capacities were then calculated from these thresholds and expressed in metrics identical to midpoint indicators giving priority to those recommended by ILCD. NR was expressed as the carrying capacity of a reference region divided by its population and thus describes the annual personal share of the carrying capacity. Results and discussionThe developed references can be applied to indicator results obtained using commonly applied characterisation models in LCIA. The European NR are generally lower than the global NR, mainly due to a relatively high population density in Europe. The NR were compared to conventional normalisation references (NR′) which represent the aggregated interventions for Europe or the world in a recent reference year. For both scales, the aggregated intervention for climate change, photochemical ozone formation and soil quality were found to exceed carrying capacities several times. Conclusions The developed carrying capacity-based normalisation references offer relevant supplementary reference information to the currently applied references based on society's background interventions by supporting an evaluation of the environmental sustainability of product systems on an absolute scale. Recommendations Challenges remain with respect to spatial variations to increase the relevance of the normalisation references for impact categories that function at the local or regional scale. The sensitivity of NR to different choices, e.g. threshold value, should be quantified with the aim of understanding and managing uncertainties of NR. For complete coverage of the midpoint impact categories, normalisation references based on sustainability preconditions should be developed for those categories that link to the areas of protection human health and natural resources.

Interpretation of comparative LCAs: external normalization and a method of mutual differences

“…How can we obtain unbiased results?^Previous studies have arbitrarily attempted to scale down normalized data Bpeaksâ s in White and Carty (2010), but such repair efforts lack a fundamental basis. Alternatively, the use of planetary boundaries or carrying capacity based normalization references has been proposed as a way to provide a better measure of absolute impacts Bjørn and Hauschild 2015;Fang et al 2015). This can function as some sort of Bthreshold^that rejects alternatives exceeding such planetary boundaries following a strong sustainability approach (Janeiro and Patel 2015).…”

Normalisation and weighting in life cycle assessment: quo vadis?

“…As part of external normalisation, a recent method based on the definition of carrying capacities has emerged (Bjørn and Hauschild, 2015). The method is based on an alleged more ecologically oriented stance, giving priority to natural boundaries rather than to current levels of e.g.…”

“…It thus accounts for the environmental flows from all up-and downstream processes needed to support the consumption activities of that region/country over the reference duration, including those that occur outside its physical or geographical boundaries as a consequence of the activities taking place within that region or nation. (Breedveld et al, 1999;Dahlbo et al, 2013;Laurent and Hauschild, 2015) CarryingCharacterized indicator results are divided by the normalisation references representing (Bjørn and Hauschild, 2015) Pizzol, M, A Laurent, S Sala, F Verones, the carrying capacity of the reference system (e.g. world) for each impact category * Alternatives are defined as any compared system (whether they relate to different scenarios of a same product system or to different product systems).…”

Local versus Global Environmental Performance of Dairying and Their Link to Economic Performance: A Case Study of Swiss Mountain Farms

“…As identified by Sala et al [61], further research and development of the methods in the LCA field are needed in order for the indicators to better reflect the carrying capacity and planetary boundaries. First LCA-based approaches that integrate carrying capacities into environmental performance indicators and enable analyses to move from relative to absolute environmental sustainability were recently developed (e.g., [62][63][64]). Also, Repar et al [7] developed conceptual considerations on how to integrate carrying capacities into the indicators of the local and global environmental performance they proposed.…”