Introduction to Water Assessment in GaBi Software

Transcription

1 Introduction to Water Assessment in GaBi Software Version 1.0 November 2012

2 Authors Dr. Annette Koehler Daniel Thylmann PE INTERNATIONAL AG Hauptstraße Leinfelden Echterdingen Germany Phone Fax Internet info@pe-international.com

3 Content List of Contents 1 Introduction Terminology Water assessment in GaBi Software Quantities of water use, degradative water use and freshwater consumption Water use Degradative use Consumptive use of freshwater (freshwater consumption) Assessment of environmental impacts water footprinting Literature List of Figures Figure 3-1: Water input flows in GaBi Software... 4 Figure 3-2: Water output flows in GaBi Software... 5 Figure 4-1: Fresh water use in GaBi Software... 6 Figure 4-2: Blue water use in GaBi Software... 7 Figure 4-3: Degradative water outputs in GaBi Software... 7 Figure 4-4: Freshwater consumption in GaBi Software... 9 Figure 4-5: Blue water consumption in GaBi Software

4 Introduction 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. The 2012 GaBi 6 upgrade 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

5 Terminology 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 plants (Note: Only water from irrigation is considered in the assessment of agricultural processes. Consumption of rain water is neglected.), 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 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 CD). 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 alteration in quality Freshwater consumption = freshwater lost to the watershed (water vapor to air 1, evapotranspiration, water incorporated into products, water release to sea) Freshwater inputs degradative freshwater outputs (outputs to freshwater and soil environment) = Freshwater consumption 1 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

6 Water assessment in GaBi Software 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. 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 4

7 Water assessment in GaBi Software The water output flows are depicted in Figure 3-2: Figure 3-2: Water output flows in GaBi Software 5

8 Quantities of water use, degradative water use and freshwater consumption 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. 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: Figure 4-1: Fresh water use in GaBi Software 6

9 Quantities of water use, degradative water use and freshwater consumption 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 and the quality has been altered. Water emissions to freshwater are assumed to remain in the same watershed, so this is the degradative use category (see Figure 4-3). degradative water outputs Figure 4-3: Degradative water outputs in GaBi Software 7

10 Quantities of water use, degradative water use and freshwater consumption 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. 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 PE INTERNATIONAL 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: 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 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. 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

11 Quantities of water use, degradative water use and freshwater consumption The corresponding GaBi quantities are defined as follows in Figure 4-4: Figure 4-4: Freshwater consumption in GaBi Software Figure 4-5: Blue water consumption in GaBi Software 9

12 Assessment of environmental impacts water footprinting 5 Assessment of environmental impacts water footprinting The water footprint of a product system is a set of different calculations (see ISO draft) 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 PE INTERNATIONAL for further information on how further evaluations, including impact assessment of your GaBi water inventories, can be performed. 10

13 Literature 6 Literature BAYART ET AL BERGER, FINKBEINER 2010 ISO (CD) 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 WA- TER USE IN LIFE CYCLE ASSESSMENT?. SUSTAINABILITY 2 (4), ISO/CD LIFE CYCLE ASSESSMENT -- WATER FOOTPRINT -- REQUIREMENTS AND GUIDE- LINES. INTERNATIONAL ORGANIZATION FOR STANDARDIZATION. KOEHLER, A. (2008): WATER USE IN LCA: MANAGING THE PLANET S FRESHWATER RE- SOURCES. 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 BIOEN- ERGY. 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) 11