Introduction to Water Assessment in GaBi

Transcription

1 Introduction to Water Assessment in GaBi Version 1.2 unchanged for 2016 Edition

2 Contents Contents Introduction Terminology Water assessment in GaBi Software Quantities of water use, degradative water use and fresh-water consumption Water use Degradative use Consumptive use of freshwater (freshwater consumption) 7 5 Assessment of environmental impacts water footprinting References Authors Dr. Annette Koehler Daniel Thylmann annette.koehler@thinkstep.com daniel.thylmann@thinkstep.com 1

3 1 Introduction Freshwater scarcity is recognized as one of the most pressing environmental issues today and in the future. There is increasing interest in using the GaBi software to assess water use from an LCA perspective. With the yearly upgrades, GaBi Software always contains complete and consistent water inventory data. Since 2012 (GaBi 6 upgrade) GaBi provides additional quantities to allow for easy assessment of water data that are the fundamentals for water footprint calculations. It is therefore important to have a correct understanding of the terminology for the GaBi quantities applied. This document provides an introduction to the latest GaBi water assessment terminology and details on how water use and water consumption can be assessed using GaBi Software. 2 Terminology Water use: Water use is understood as an umbrella term for all types of anthropogenic water uses. On an inventory level, water use equals the measured water input into a product system or process. In most cases water use is determined by total water withdrawal (water abstraction). Consumptive and degradative use: Freshwater use is generally differentiated into consumptive water use (= water consumption) and degradative water use, the latter denoting water pollution: Freshwater consumption (consumptive freshwater use) describes all freshwater losses on a watershed level which are caused by evaporation, evapotranspiration from plants1, freshwater integration into products, and release of freshwater into sea (e.g. from wastewater treatment plants located on the coast line). Therefore, freshwater consumption is defined in a hydrological context and should not be interpreted from an economic perspective, so it does not equal the total water use (total water withdrawal), but rather the associated losses during water use. Note 1 Note: Typically, only water from irrigation is considered in the assessment of agricultural processes and the consumption of rain water is neglected. The rationale behind this approach is the assumption that there is no environmental impact of green water (i.e. rain water) consumption. Such an effect would only exist if crop cultivation results in alterations in water evapotranspiration, runoff and infiltration compared to natural vegetation. Additionally it remains arguable whether or not such changes (if they occur) should be covered by assessment of land use changes rather than in water inventories. However, rain water use is sometimes assessed in different methodological approaches or can be used for specific analyses. The GaBi software allows assessment of both water use including rain water ( Total fresh water use, total freshwater consumption ) and without rainwater ( Blue water use and blue water consumption ), see Chapter 4. 2

4 that only the consumptive use of freshwater, not sea water, is relevant from an impact assessment perspective because freshwater is a limited natural resource. Degradative water use, in contrast, denotes the use of water with associated quality alterations and describes the pollution of water (e.g. if tap water is transformed to wastewater during use). These alterations in quality are not considered to be water consumption. Note that the watershed level is regarded as the appropriate geographical resolution to define freshwater consumption (hydrological perspective). If groundwater is withdrawn for drinking water supply and the treated wastewater is released back to a surface water body (river or lake), then this is not considered freshwater consumption if the release takes place within the same watershed; it is degradative water use. The difference between freshwater use and freshwater consumption is highly crucial to correctly quantify freshwater consumption, in order to interpret the meaning of the resulting values and for calculating water footprints (see ISO 14046). Summary: Freshwater Use = consumptive use + degradative use of freshwater = water input of freshwater or total freshwater withdrawal on inventory level Degradative use of freshwater = freshwater released back to watershed, with possible alteration in quality Freshwater consumption = freshwater lost to the watershed (water vapor to air2, evapotranspiration, water incorporated into products, water release to sea) Freshwater inputs degradative freshwater outputs (outputs to freshwater and soil environment) = Freshwater consumption 3 Water assessment in GaBi Software All water flows necessary for calculating water use and freshwater consumption can be found in the GaBi balance view. 2 Note that evaporated water is denoted water vapor (elementary flow) in the GaBi inventory system while steam is considered a technical flow (as product output from e.g. steam generation, i.e. valuable substance). 3

5 The water input flows can be found under Resources Material resources Renewable resources Water (see also Figure 3-1). Figure 3-1: Water input flows in GaBi Software The water output flows are depicted in Figure 3-2: Figure 3-2: Water output flows in GaBi Software Note that for the output flows, the first term in brackets refers to the receiving water body, and the second term to the water type released from the technosphere. E.g., river water from 4

6 technosphere, cooling water refers to cooling water that is released into a river after use. With the 2014 update a set of new flows was introduced: lake water from technosphere, rain water, river water from technosphere, rain water, and sea water from technosphere, rain water. These flows can be used to account for collected rainwater that is released back into the environment (after use and/or treatment if applicable) in order to set up closed water balances. Please also note that only flows that are used in the respective data set/ LCA model will appear in your balance view, i.e. not all listed flows will be visible in all datasets. 4 Quantities of water use, degradative water use and freshwater consumption With the 2012 update, the GaBi software contains quantities for water use and water consumption, as defined and described below. 4.1 Water use The water input flows in GaBi refer to total water use. In order to quantify total freshwater use, all freshwater input flows are summed up. As stated above, rain water is important for a complete inventory and thus part of the total water use and total freshwater use. However, for impact assessments, in general only blue water (surface and groundwater) is considered, excluding rain water (see above footnote 1). Normally, the focus lies in freshwater use and consumption. Sea water is also excluded in this aggregation. Thus, the flow based equations are: Total freshwater use = total freshwater withdrawal/abstraction = water (river water) + water (lake water) + water (ground water) + water (rain water) + water (fossil groundwater) Blue water use = Water (ground water) + Water (lake water) + Water (river water) + Water (fossil ground water) Accordingly the provided GaBi quantities are defined as in Figure 4-1 and Figure 4-2: 5

7 Figure 4-1: Fresh water use in GaBi Software Figure 4-2: Blue water use in GaBi Software 4.2 Degradative use Degradative water output: As mentioned above, degradative use takes place when the water used remains in the same watershed (potentially with altered quality). Water emissions to freshwater are assumed to remain in the same watershed, so this is the degradative use category (see Figure 4-3). 6

8 degradative water outputs Figure 4-3: Degradative water outputs in GaBi Software The water flows that leave waste water treatment plants (river water from technosphere, waste water) can be found among the outputs. River water from technosphere, turbined refers to water use in hydroenergy generation. Corresponding flows lake water from technosphere exist. Please note that river/lake/sea water in the output refers to the destination of the water released, not to the source (see above). Degradative use (water pollution, release of contaminants or heat into water bodies) describes changes in quality which are covered by specific impact categories of LCA (e.g. eutrophication, acidification, ecotoxicity, assessment of thermal emissions). Methods to assess effects of reduced water availability due to deterioration in water quality are still in development and in their very infancy. Please contact thinkstep in case further information is needed. 4.3 Consumptive use of freshwater (freshwater consumption) As mentioned above, freshwater that leaves the watershed is considered consumed. This is the fraction that is most interesting as this water is lost to the ecosystem and for downstream users. Total freshwater consumption is defined as: 7

9 Total freshwater consumption = total freshwater use (water input) total freshwater release from technosphere (water outputs) = water vapor (including water evaporated from input products and including evapotranspiration of rain water from plants) + water incorporated in product outputs + water (freshwater, incl. rainwater released to sea,) Please note that in general only blue water (surface and ground water) is considered. Therefore, rain water is typically excluded from freshwater consumption and the focus is only on blue water consumption (see above, footnote 1). In detail, the flow based calculation is: Blue water consumption = Water (ground water) + Water (lake water) + Water (river water) Water (river water from technosphere, cooling water) Water (river water from technosphere, turbined) Water (river water from technosphere, waste water) Water (lake water from technosphere, cooling water) Water (lake water from technosphere, turbined) Water (lake water from technosphere, waste water) 8

10 The corresponding GaBi quantities are defined as follows in Figure 4-4: Figure 4-4: Total freshwater consumption in GaBi Software 9

11 Figure 4-5: Blue water consumption in GaBi Software 5 Assessment of environmental impacts water footprinting The water footprint of a product system is a set of different calculations (see ISO 14046) and should be used as an umbrella term rather than to communicate a single number. Only results on the level of environmental impact (e.g. after consideration of regional water availability) should be labeled as a water footprint. The simple aggregation of water on an inventory level represents water accounting and should be expressed as such and not as a water footprint. Please contact thinkstep for further information on how further evaluations, including impact assessment of your GaBi water inventories, can be performed. ISO 14046:2014 specifies principles, requirements and guidelines related to water footprint assessment of products, processes and organizations based on life cycle assessment (LCA). ISO 14046:2014 provides principles, requirements and guidelines for conducting and reporting a water footprint assessment as a stand-alone assessment, or as part of a more comprehensive environmental assessment. Only air and soil emissions that impact water quality are included in the assessment, and not all air and soil emissions are included. The result of a water footprint assessment is a single value or a profile of impact indicator results. Whereas reporting is within 10

12 the scope of ISO 14046:2014, communication of water footprint results, for example in the form of labels or declarations, is outside the scope of ISO 14046:2014 [ISO 14026:2014]. The most demanding aspect of the new standard is the need to limit the aggregation of information on the life cycle impact assessment part of the modelling. This means that principally any LCI value of any water related intervention of any step in the life cycle must be reported separately in the inventory phase. Even if several thousand processes are involved it is theoretically not allowed to aggregate on LCI level. Aggregation is only allowed in the subsequent step in the impact assessment. A sister standard Environmental management Water Footprint Examples is still in work and practical guidance how to apply this standard on process chains of several thousand processes still missing. However, the GaBi database enables the user to fully comply with the new standard in the foreground system. Any related and necessary water flow is defined in the GaBi database and may be used in the own foreground system of the user and in the specific data collection process of each individual user. Concerning background data and data on pre-calculated systems (of several thousand unit processes) in GaBi as well as data of other re-published third party or industry data sources (like certain association data, certain company data) within the GaBi databases may show different water results than (theoretically) calculated on basis of the new ISO standard. Depending of the specific case of water quality and location of use the difference might be more or less relevant. Due to the relative premature nature of the water footprint results, we recommend to carefully interpret water footprint results. In case of any significant difference between existing water footprint results and newly ISO calculated results we recommend scenarios and the sensitivity analysis. Concerning our own background data and the data provided by industry and associations we will stepwise update the information towards full ISO conformity, considering relevancy and feasibility of the update. 11

13 6 References BAYART ET AL BERGER, FINKBEINER 2010 ISO KOEHLER 2008 PFISTER ET AL PFISTER, HELLWEG 2009 RIDOUTT, PFISTER 2010 RIDOUTT, PFISTER 2012 BAYART, J.; BULLE, C.; DESCHÊNES, L.; MARGNI, M; PFISTER, S.; VINCE, F.; KOEHLER, A. (2010): A FRAMEWORK FOR ASSESSING OFF-STREAM FRESHWATER USE IN LCA. INT J LIFE CYCLE ASSESS 17(3), PP BERGER, M.; FINKBEINER, M. (2010): WATER FOOTPRINTING: HOW TO ADDRESS WATER USE IN LIFE CYCLE ASSESSMENT?. SUSTAINABILITY 2 (4), ISO/CD LIFE CYCLE ASSESSMENT -- WATER FOOTPRINT -- REQUIREMENTS AND GUIDELINES. INTERNATIONAL ORGANIZATION FOR STANDARDIZATION. KOEHLER, A. (2008): WATER USE IN LCA: MANAGING THE PLANET S FRESHWATER RESOURCES. INT J LIFE CYCLE ASSESS 13 (6), PP PFISTER, S.; KOEHLER, A.; HELLWEG, S. (2009): ASSESSING THE ENVIRONMENTAL IMPACT OF FRESHWATER CONSUMPTION IN LCA. ENVIRON SCI TECHNOL 43(11), PFISTER, S.; HELLWEG, S. (2009): THE WATER SHOESIZE VS. FOOTPRINT OF BIOENERGY. PNAS 106(35), E93-E94 RIDOUTT, B.; PFISTER, S. (2010): A REVISED APPROACH TO WATER FOOTPRINTING TO MAKE TRANSPARENT THE IMPACTS OF CONSUMPTION AND PRODUCTION ON GLOBAL FRESHWATER SCARCITY. GLOBAL ENVIRONMENTAL CHANGE 20 (2010), RIDOUTT, B.; PFISTER, S. (2012): 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, ONLINE FIRST (2012) 12