Building consensus on a generic water scarcity indicator for LCA-based water footprint: preliminary results from WULCA

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1 Building consensus on a generic water scarcity indicator for LCA-based water footprint: preliminary results from WULCA Anne-Marie Boulay 1,*, Jane Bare 2, Lorenzo Benini 3, Markus Berger 4, Inga Klemmayer 5, Michael Lathuilliere 6, Philippe Loubet 7, Alessandro Manzardo 8, Manuele Margni 1, Montserrat Núñez 7, Bradley Ridoutt 9, Sebastien Worbe 10, Stephan Pfister 11 1 CIRAIG, Ecole Polytechnique of Montreal, Canada 2 US EPA, Office of Research and Development, National Risk Management Research Laboratory, Cincinnati, OH 3 European Commission, Joint Research Center Sustainability Assessment Unit, Ispra (VA), Italy 4 Technische Universität Berlin, Chair of Sustainable Engineering 5 Hamburg University of Technology, Institute for Water Resources and Water Supply, Germany 6 Institute for Resources, Environment and Sustainability, University of British Columbia, Vancouver, Canada 7 Irstea, UMR ITAP, Montpellier, France 8 CESQA, University of Padua, Department of Industrial Engineering, Italy 9 Commonwealth Scientific and Industrial Research Organisation (CSIRO), Sustainable Agriculture National Research Flagship, Private Bag 10, Clayton South, Victoria 3169, Australia 10 Veolia Environment Research & Innovation, France 11 ETH Zurich, Institute of Environmental Engineering Corresponding author. anne-marie.boulay@polymtl.ca ABSTRACT Consuming water can affect human health (e.g. by reducing availability of irrigation water and hence food availability), ecosystems (by decreasing water availability for terrestrial/aquatic species) and future generations (by depleting non-renewable resources). However, no standard method exists to quantify the stress on water without favoring any of these areas of protection. Stress/scarcity indexes have focused on an anthropocentric perspective, and a few on an ecocentric perspective. We explore the possibility of developing an indicator considering the water resource as a whole and propose a method which is not centered on an area of protection but rather assesses the extent to which all water demand and availability differ within a watershed (i.e. hydrocentric). This concept can eventually serve as a single metric to assess potential impacts from water use and be used consistently in the application of the upcoming ISO standard and for ecolabelling of food and energy products. Keywords: water use impact assessment, Water Footprint, environmental impacts, water stress, water scarcity 1. Introduction Life Cycle Assessment (LCA) has served as a decision-making tool to help reduce environmental impacts for several decades. Recently, the methodology was used to assess water-specific impacts and group them in a new water footprint concept, currently being framed in an upcoming ISO standard (ISO/FDIS 14046, 2014). While this document provides principles, requirements and guidelines, no specific characterization method is recommended even though several have emerged in the last five years to assess impacts from water use (Kounina et al. 2013). The need for a consensus-based method is clear and particularly relevant for food production systems where product-level environmental labels and declarations are already emerging. In 2013, the UNEP-SETAC Life Cycle Initiative recognized the need for a consensual method following the many existing water use impact assessment methods described by Kounina et al. (2013), and solicited the Water Use in LCA Working Group (WULCA), fostering method development and applications since 2007, to undertake this task. By bringing together method developers and experts from the fields of LCA, hydrology, ecology, etc., WULCA will propose by the end of 2015, consensus-based indicators to assess impacts from water use, which can be used to comply with the requirements of the ISO document. This paper presents the water footprint concept as defined in the upcoming ISO standard, and WULCA s progress towards a consensus-based method. As agriculture accounts for over 70% of water withdrawal and its water consumption is estimated to increase by a 20% by 2050 (WWAP, 2014), combined with the fact that agri-food global businesses are expanding and hence putting new stress on local aquifers (WBCSD, 2012), the food sector is benefitting most from such methodological developments. 142

2 1.1. LCA and water footprinting In contrast with an LCA, an LCA-based water footprint is the fraction of LCIA results which are related to water resource. These LCIA results include impacts associated with water use, and the subsequent effect on water availability for humans and ecosystems, as well as direct impacts on the water resource and its users from relevant emissions to air, soil and water (see Fig.1). These latter impacts are quantified using traditional LCA impact categories (e.g. freshwater eutrophication, freshwater acidification, human toxicity and eco-toxicity). A water footprint may be presented as the result of a stand-alone assessment or as a sub-set of results of a larger environmental assessment, such as an LCA. As per the ISO standard, a qualifier is used when a water footprint study is limited to certain aspects only. A water scarcity footprint and a water availability footprint assess impacts associated with water use only, whereas a water footprint (no qualifier ) assesses all relevant impacts related to water, hence including relevant emissions that occur without any water use and yet still impact water (e.g. SO x emissions to air causing freshwater acidification). In the recent years, businesses have started to include scarcity indicators (sometimes also called stress indicators) to assess potential impacts of water use. In the context of the standard, this is the equivalent of a water scarcity footprint, or a water availability footprint (if the change in water availability caused by water degradation is also included). However, at this point no consensus-based approach exists for doing so and results are not always comparable when different scarcity/stress indicators are used for characterization. Figure 1: Representation of a water footprint with respects to LCA impact categories (figure from Impact World + (Bulle et al. 2014)) Scarcity From the ISO definition, scarcity is the extent to which demand for water compares to the replenishment of water in an area, such as a drainage basin (ISO ). Up until now, water scarcity indexes have been built to reflect the problem as one for either humans or ecosystems. Most indexes (Pfister et al. 2009; Boulay et al. 2011; Frischknecht et al. 2009; Gassert et al. 2013) considered only human water use divided by water availability (see Eq.1). A few others (Smakhtin et al. 2004; Hoekstra et al. 2012) have considered that water scarcity should exclude water requirement for ecosystems to be maintained in fair condition, resulting in an index that shows whether the human water use impairs ecosystems (>1) or not (<1) (see Eq.2). Hence, none of these indicators represents a neutral assessment of the relationship between all water demand and availability. 143

3 The main gap is that no indicator exists where demand for water in an area is compared with availability in such a way that modeling choices and interpretation of the physical meaning are explicit and transparent. human water use Scarcity Anthropocentric = Fn ( ) Eq. 1 water availability human water use Scarcity Ecocentric = Fn ( ) Eq. 2 water availability ecosystem water requirement 1.3. Consensus-based indicator project from WULCA WULCA commenced a new two-year activity in January 2014 aiming at developing consensus-based indicator(s) for water use impact assessment. The first steps defined a framework (based on previous WULCA deliverable (Bayart et al. 2010; Kounina et al. 2013)) and led to the identification of the three sets of indicators on which to focus (see Fig.2): 1) The impact pathway leading to damages on human health is already modeled by different methods and ready for harmonization (Boulay et al. 2014). Hence it was included in the work and a consensus-based methodology defining this impact pathway is under development. 2) The ecosystem impact pathway includes several methodologies with possible complementary assessments (Kounina et al. 2013). A subgroup was formed to harmonize the different impact pathways in this category, by defining a consistent framework and possibly identify a midpoint indicator early in the impact pathway. 3) Answering the demand from industry for a generic (not human- or ecosystem-oriented) and recommended stress/scarcity indicator, a specific sub-group focused its efforts on the development of such a metric. It was set out as an indicator independent of other impact pathways and not leading directly to any endpoint damages. Further harmonization with the conventional midpoint-endpoint framework may come later as the indicators further develop. This paper is presented by the sub-working group focusing on this last stress-based midpoint indicator and presents results of the findings to date. The impact pathways leading to impacts on resources or compensation processes were considered not sufficiently mature to be included in this consensus building phase. Figure 2. Chosen impact pathways for WULCA s consensus building work. 144

4 2. Methods In order to provide a scarcity indicator which represents a generic assessment of the demand and availability of water in a region, we define scarcity following ISO/FDIS definition, as shown in Eq.3, where the total water demand includes all users, human and non-human, and water availability includes the available renewable resource. This indicator is therefore not anthropocentric or ecocentric, but simply based on the water resource, i.e. hydrocentric. Scarcity hydrocentric = Fn ( Total water demand ) Renewable water availability Eq.3 To illustrate the difference in scarcity definitions, we compare the three approaches using eq. 1-3 without a scaling function (just the ratios) in a simple preliminary assessment. Not all necessary high quality data was available at this early stage of the project and proxy data was used to illustrate the concepts. Human water consumption (HWC) from WaterGap (Alcamo et al. 2003) was used to represent water demand from humans. Environmental water requirements (EWR) assessment from Smakthin et al. (2004) were used to represent ecosystem water demand. These values represent the portion of the available flow required to maintain ecosystems in a fair condition, defined by the authors as moderate or considerable modification from the natural state where the sensitive biota is reduced in numbers and extent. This state represents a modeling choice which should be agreed on and assessed with corresponding data. This data is regionalized and readily available for the entire globe, and was used as a first assessment to illustrate the concepts; it does not yet include terrestrial ecosystems water requirements and may not represent the best data available. Water availability (WA) data from WaterGap (Alcamo et al. 2003) was used for this first assessment. 3. Results Figures 3, 4, and 5 illustrate the different scarcity ratios: anthropocentric, ecocentric and hydrocentric, respectively. They are calculated using the ratios presented in Eq. 1, 2 and 3 respectively. The difference between anthropocentric and ecocentric scarcity is negligible for most of the world, with few watersheds showing visibly higher scarcity in the ecocentric case (hardly visible on a black and white scale). This makes sense, since the scarcity level is increased by environmental flow requirements but the pattern is not changed. Not surprisingly, results on Fig.5 show higher scarcity in most regions of the world for the hydrocentric indicator since this includes ecosystem water demand within the numerator of the equation and therefore also regions with no human water consumption show some scarcity. Figure 6 shows the difference in results between the anthropocentric indicator and hydrocentric indicator. At a minimum, scarcity increases in comparison to the anthropocentric approach between around the world. Most of North and South America, Europe and Central Asia increases between , and some watersheds in the USA and Eastern Europe increase by up to This difference represents exactly the EWR percent of available water assessed by Smakhtin et al. (2004), which varies from 0-47%. By integrating ecosystem s water requirement, this approach therefore gets rid of the artifact that water scarcity in desert areas is 0 if no human is using water, as discussed in Berger et al (2014). Figure 7 shows the difference in results between the hydrocentric approach and the ecocentric indicator. In this case, some highly scarce regions show a higher indicator with the ecocentric indicator than with the hydrocentric approach, but these regions are still consistently at the top of the scarcity scale. As a mathematical demonstration, if one hypothetical region shows a water availability of 100 m 3, with 90% of this amount being consumed by humans (90 m 3 ), yet having a EWR value of 40% (40 m 3 ), the ecocentric indicator would result in 90/(100-40) = 1.5, indicating that the water use is tapping into the ecosystem s requirements. A hydrocentric approach results in ( )/100 = 1.3, indicating the shared pressure on both human and ecosystem needs for water. 145

5 Scarcity Anthropocentric Figure 3. Anthropocentric scarcity assessment showing the ratio of consumed water by humans to available water (HWC/WA). Scarcity Ecocentric Figure 4. Ecocentric scarcity assessment showing the ratio of consumed water by humans to available water, to which water for ecosystem has been subtracted (HWC/(WA-EWR)). Scarcity Hydrocentric Figure 5. Hydrocentric scarcity assessment based on the ratio of all water demand to all water available, showing the pressure on the water resource ((HWC+EWR)/WA). 146

6 Difference Hydrocentric - anthropocentric Figure 6. Difference (decimal percentage) between the hydrocentric approach as shown in Fig.5 and the anthropocentric scarcity shown in Fig.3. Difference Hydrocentric - ecocentric Figure 7. Difference (decimal percentage) between the hydrocentric approach as shown in Fig.5 and the ecocentric scarcity shown in Fig Discussion Results presented in this paper show intermediate work as the working group progresses towards a consensual indicator. At this point, we have identified that scarcity indicators used until now have been focused mainly on potential impacts on humans, and some towards ecosystems, but none reflected simply the pressure on the resource coming from the demand of all local water users in comparison with the availability. At this point, potential impacts on ecosystems from water use have only been accounted for at the endpoint level (e.g. Pfister et al. 2009, Hanafiah et al. 2011). A combination of human and ecosystem impacts based on endpoint methods and subsequent weighting of these indicators have been suggested by Ridoutt and Pfister (2013). However, such aggregated endpoint-based CF integrate a weighting scheme, which is only allowed by ISO as an additional and subsequent step following impact characterization, after first obtaining separated impact category indicator results. This ensures that value choices are transparently provided and eventually can be adapted to the values of the decision maker. While such weighted methods are still being investigated (Ridoutt and Pfister, 2014), the objective of the approach presented in this paper is rather to provide a generic indicator representing potential problems associated with water use in relation with the local scarcity, without focusing on one area of protection. Findings of this paper indicate that an indicator that assesses scarcity following the ISO definition and considering all water demand can provide an alternative perspective and better reflect the potential consequences of using water in different areas around the world. Hydrocentric scarcity values are higher than anthropocentric scarcity values and generally higher than ecocentric scarcity values (except in highly (eco)scarce regions), and hence may allow the quantification of potential problems in such regions that have been excluded so far on the scarcity level. 147

7 However, the main challenges lie in the proper attribution of ecosystem water needs compared to human water consumption and the data availability to develop a global indicator of reasonable quality for robust assessments. In this paper, human water consumption was used, along environmental water requirements for ecosystems based on fair conditions, which is not based on the same reference and hence still introduces some bias. Results would likely differ and scarcity values increase if the same perspective on demand is taken. However, this was performed as a preliminary assessment with readily available data, and defining and assessing the water demand from humans and ecosystems with the same underlying basis (e.g. actual water demand, ideal/pristine water demand, etc.) is necessary to reduce bias and remain transparent. Best available data should be used to represent the water demand both from a human and an ecosystem perspective, including aquatic and terrestrial ecosystems, with special attention to wetlands (Verones, Pfister, et al. 2013; Verones, Saner, et al. 2013). Different definitions and sources of data exist to quantify water availability, whether current or pristine for example, and this aspect should be investigated and the most relevant source for this indicator chosen. Also, while this work has shown only blue water-related data, interactions with green water and the change in blue water associated with land use change should be investigated. Coherence among the sources of data, the geographic and temporal resolution, and close analysis to prevent double counting are important aspects that should be analyzed. 5. Conclusion This work provided an overview of the relationship between LCA, water scarcity, water availability and water footprinting, in light of the upcoming ISO standard It quantifies the characterization factors for different interpretations of the scarcity concept and applied directly the ISO definition to provide a first glance at a generic hydrocentric indicator of water scarcity quantifying the pressure on the water resource in a region by relating the water demand and availability. Results show higher scarcity in comparison with the currently used anthropocentric methods as it encompasses a larger problematic. The WULCA working group is further developing this indicator through ongoing investigating of data sources, hypothesis, data resolutions and choices associated with this novel approach. 6. Acknowledgements The authors acknowledge the financial support of WULCA s sponsors: Cascades, Cotton Incorporated, Danone, ExxonMobil, GDF SUEZ, Hydro-Québec, Unilever and Veolia. 7. References Alcamo, J. et al., Development and testing of the WaterGAP 2 global model of water use and availability. Hydrological Sciences Journal, 48(3), pp Bayart, J.-B. et al., Framework for assessment of off-stream freshwater use within LCA. International Journal of Life Cycle Assessment, 15(5), p.439. Berger, M. et al., Water Accounting and Vulnerability Evaluation (WAVE): Considering Atmospheric Evaporation Recycling and the Risk of Freshwater Depletion in Water Footprinting. Environmental science & technology, 48(8), pp Available at: Boulay, A.-M. et al., Regional Characterization of Freshwater Use in LCA: Modeling Direct Impacts on Human Health. Environmental Science & Technology, 45(20), pp Available at: Boulay, A.-M. et al., Analysis of water use impact assessment methods (part A): evaluation of modeling choices based on a quantitative comparison of scarcity and human health indicators. International Journal of Life Cycle Assessment, DOI /s Bulle, C. et al., Impact World +. Frischknecht, R., Steiner, R. & Jungbluth, N., The Ecological Scarcity Method - Eco-Factors 2006: A method for impact assessment in LCA U.-W. N. 0906, ed. Gassert, F. et al., AQUEDUCT Global Maps 2. 0, Washington, D.C. 148

8 Hoekstra, A. Y., Mekonnen, M. M., Chapagain, A. K., Mathews, R. E., & Richter, B. D. (2012). Global Monthly Water Scarcity : Blue Water Footprints versus Blue Water Availability. PLoS ONE, 7(2). doi: /journal.pone ISO 14046, Water footprint Principles, requirements and guidelines, Kounina, A. et al., Review of methods addressing freshwater use in life cycle inventory and impact assessment. The International Journal of Life Cycle Assessment, 18, pp Available at: Pfister, S., Koehler, A. & Hellweg, S., Assessing the environmental impacts of freshwater consumption in LCA. Environmental Science & Technology, 43(11), pp Available at: Ridoutt, B.G. & Pfister, S., A new water footprint calculation method integrating consumptive and degradative water use into a single stand-alone weighted indicator. International Journal of Life Cycle Assessment, 18, pp Smakhtin, V., Iwra, M. & Water, I., A Pilot Global Assessment of Environmental Water Requirements and Scarcity., 29(3), pp Verones, F., Saner, D., et al., Effects of Consumptive Water Use on Biodiversity in Wetlands of International Importance. Environ. Sci. Technol., 47, pp Verones, F., Pfister, S. & Hellweg, S., Quantifying Area Changes of Internationally Important Wetlands Due to Water Consumption in LCA. Environ. Sci. Technol., 47, pp WBCSD (World Business Council for Sustainable Development) (2009). Water for Business Initiatives guiding sustainable water management in the private sector. Visited online 23/04/2014 WWAP (United Nations World Water Assessment Programme), The United Nations World Water Development Report 2014: Water and Energy. Paris, UNESCO. 149

9 This paper is from: Proceedings of the 9th International Conference on Life Cycle Assessment in the Agri-Food Sector 8-10 October San Francisco Rita Schenck and Douglas Huizenga, Editors American Center for Life Cycle Assessment

10 The full proceedings document can be found here: It should be cited as: Schenck, R., Huizenga, D. (Eds.), Proceedings of the 9th International Conference on Life Cycle Assessment in the Agri-Food Sector (LCA Food 2014), 8-10 October 2014, San Francisco, USA. ACLCA, Vashon, WA, USA. Questions and comments can be addressed to: ISBN: