Existing methods for applying the planetary boundary concept in life cycle assessment are not sufficiently spatially and temporally resolved. Here, we develop a new method for freshwater use based... Show moreExisting methods for applying the planetary boundary concept in life cycle assessment are not sufficiently spatially and temporally resolved. Here, we develop a new method for freshwater use based on the safe operating space (SOS) at watershed-level. The SOS is based on the concept of environmental flow requirements, which is the share of mean monthly flow that should be reserved to achieve or maintain "fair conditions" of aquatic ecosystems. The method is composed of two steps. First, water consumption is multiplied by a characterization factor, which converts it to an environmental impact, expressed as an area-equivalent of a watershed's mean monthly flow. Second, the environmental impact is compared to an assigned share of SOS to determine if the activity causing it can be considered environmentally sustainable, with respect to a chosen principle for sharing the SOS.The method is demonstrated for a case study on water consumed for irrigation in open-field tomato production in 27 watersheds, spanning 10 countries and 5 continents, based on data for 316 farms in the year 2014. Water consumption was modelled from crop characteristics, climatic data and the assumed type of irrigation system. Two principles, "status quo" and "gross value added", were illustratively applied for the assignment of SOS to 1 tonne of tomatoes.The characterization factors developed span two orders of magnitude from 10th to 90th percentile, which shows the relevance of a spatially and temporally explicit assessment. In the case study, the characterization factors largely determine the high variability in the resulting environmental impacts between watersheds, which ranged from 400 m(2) to 50,000 m(2) per tonne of tomatoes. The analysis would suggest that the freshwater use by current tomato farming is environmentally sustainable in all months in a maximum of 2 of the 27 watersheds with respect to the two principles applied for sharing the SOS.The method can be used as a basis to identify potential "planetary boundary hotspots" in the life cycle of products and to inform appropriate interventions. Two key challenges are the lack of appropriate spatial and temporal data in current life cycle inventories and the choice of sharing principle for assigning the SOS. Show less
Ecosystem quality is an important area of protection in life cycle impact assessment (LCIA). Chemical pollution has adverse impacts on ecosystems at the global scale. To improve methods for... Show moreEcosystem quality is an important area of protection in life cycle impact assessment (LCIA). Chemical pollution has adverse impacts on ecosystems at the global scale. To improve methods for assessing ecosystem impacts, the Life Cycle Initiative hosted at the United Nations Environment Programme established a task force to evaluate the state-of-the-science in modelling chemical exposure of organisms and resulting ecotoxicological effects for use in LCIA. Outcome of the task force work will be global guidance and harmonization by recommending changes to the existing practice in exposure and effect modelling in ecotoxicity characterization. These changes reflect the current science and ensure stability of recommended practice. Recommendations must work within the needs of LCIA in terms of (a) operating on information from any inventory reporting chemical emissions with limited spatiotemporal information, (b) applying best estimates rather than conservative assumptions to ensure unbiased comparison with results for other impact categories, and (c) yielding results that are additive across substances and life cycle stages and allow a quantitative expression of damage to the exposed ecosystem. Here, we report the current framework as well as discuss research questions identified in a roadmap. Primary research questions relate to the approach for ecotoxicological effect assessment, the need to clarify the method's scope and interpretation of its results, the need to consider additional environmental compartments and impact pathways, and the relevance of effect metrics other than the currently applied geometric mean of toxicity effect data across species. Because they often dominate ecotoxicity results in LCIA, metals pose a specific focus, which includes consideration of their possible essentiality and changes in environmental bioavailability. We conclude with a summary of key questions along with preliminary recommendations to address them as well as open questions that require additional research efforts. This article is protected by copyright. All rights reserved. Show less
