or not. gratis copy for bert bras water use vs consumption

ABSTRACTNumerous studies have pointed out the growing need toassess the availability of water sources in numerous regionsaround the world as future forecasts suggest that waterdemands will increase significantly while freshwaterresources are being depleted. In this paper, we highlight thedifference between water use versus consumption andanalyze the life-cycle water consumption of a car frommaterial extraction through production, use, and finaldisposition/end of life and determine a car's water footprintusing data from the EcoInvent database as well as datacollected from literature sources. Although water use istypically metered at the factory level, water consumption(i.e., water lost through evaporation and/or incorporation intoa material, part, and/or product) is much harder to quantify.As shown in this paper, the difference can be an order ofmagnitude or more. The use phase has significant impact onthe overall vehicle water consumption, followed by materialproduction, whereas end of life processing seems to berelatively insignificant. The assessment in this paperrepresents a life-cycle inventory assessment. The impact ofwater consumption varies by region and locality, and adifferentiation of impact would still be needed whether thewater consumption actually happens in water scarce regionsor not.

INTRODUCTIONMOTIVATIONWater is a prerequisite for life on earth. It is an essentialnatural resource for basic human needs such as food, drinkingwater and a healthy environment. Human beings areinextricably linked to freshwater for personal sustenance,basic hygiene, growing crops, producing energy,manufacturing goods or maintaining ecosystems. Given the

rise in population, and the increase in consumption of naturalresources, management of water resources has becomecritical [1]. The need for freshwater in some locations has ledto water allotments, shifts towards full-cost water pricing,more stringent water quality regulations, growing communityopposition, and increased public scrutiny over waterpractices.

Water consumption is a much different issue fromgreenhouse gas emissions because water has a local impactversus the global impact of greenhouse gas emissions. Inregions that have a surplus of water, variations in the level ofconsumption may have little noticeable impact. However, inwater scarce regions, the same consumption could putextreme strain on the available water resources.

For these reasons, we believe that assessments of water useand consumption must be developed to facilitate watermanagement and policy making. Ultimately, such analysescan serve as social change instruments - encouraging a water-oriented society that manages disputes and ensures thesharing of water by determining water use limits andequitable and efficient allocations [1].

WATER USE VS CONSUMPTIONIn this paper, we distinguish between water use and waterconsumption:

• Water consumption is defined as freshwater withdrawalswhich are evaporated or incorporated in products and waste.The water molecule is not available in liquid form for (re)useafter it is consumed, at least not immediately. The differencebetween the amount of liquid input water and liquid wastewater is the water consumption.

Quantifying the Life Cycle Water Consumption of aPassenger Vehicle

2012-01-0646Published

04/16/2012

Bert Bras, Francisco Tejada, Jeff Yen, John Zullo and Tina GuldbergGeorgia Institute of Technology

Copyright © 2012 SAE International

doi:10.4271/2012-01-0646

Gratis copy for Bert BrasCopyright 2012 SAE International

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http://dx.doi.org/10.4271/2012-01-0646

• Water Use is defined as all water that goes into a system.Most of this typically leaves the system as waste water.

This is an important distinction because, depending on howwater consumption is defined, it can alter the results of thewater footprint for a given life cycle significantly. Someauthors include water transferred into different watersheds, ordisposed into the sea after usage into the definition, e.g., [2],but we take a stricter definition due to our manufacturingprocess focus. In principle, any waste water from processoperations can be brought back to the same local with equalor better quality as the input water. Water that is included inthe product or evaporated during the process is completelylost, however.

FOCUS AND SCOPEGiven these distinct definitions, in this paper, we will assessthe amount of water consumed in a car's life-cycle, startingwith the production of materials used in a car. Althoughmany articles have been written about a vehicle's energyconsumption and greenhouse gas emissions, very few studieshave been made to assess the water consumption inproducing, operating and retiring a vehicle. With a growinginternational emphasis on water as a critical resource, a morein-depth understanding of the water footprint, or “splash” (aterm coined by Dave Berdish of the Ford Motor Company),of a typical automobile is needed. In this paper, we will focuson the water consumed by the processes of extracting andproducing the materials needed for a typical automobile. Acomparison will be made with data from domain specificliterature and data from the EcoInvent Life-Cycle Analysisdatabase (version 2.2). As will be shown, large discrepanciesexist which emphasize the need of further research.

To begin the proper assessment of how much water isconsumed in the automotive life cycle, the goals and scopemust first be identified so that proper data is collected. Themodel will only include direct water consumptions ofproduction of materials, vehicle, fuels, etc. As such, weignore the water used in developing the infrastructure of thesupply chain network at this time, such as the waterconsumed in constructing the manufacturing facilities or thewater used for electricity or the indirect water consumptionresulting from transportation of the components. Once weconsider infrastructure development water consumption, wenot only must consider the water consumption for each set ofraw materials for construction but also the water consumed inthe intermediate processes; that said, such data isinconsistent. In defining this boundary, we also must considerthat the majority of the infrastructure for producing the rawmaterials or electricity could have existed for decades andwould not be dedicated solely for the production of rawmaterials for the automobile industry [1].

RELEVANT STUDIES ANDPUBLICATIONSWATER FOOTPRINT AND “SPLASH”OF PRODUCTSThe need for assessing and understanding the water useand/or consumption of products has risen in the past yearsdue to increased droughts and global warming. Analogous toecological footprints, the term “water footprinting” has beenused to define this process of assessing a product's waterimpact source [3]. According to [4], the water footprint of anindividual, community or business is defined as the totalvolume of freshwater that is used to produce the goods andservices consumed by the individual or community orproduced by the business.

Given that the set definition of a water footprint does notinclude a distinction between consumption versus use, weprefer to use “water splash”, a phrase coined by Dave Berdishof Ford Motor Company, to represent the water consumptionand/or use by products, process, and or services.

As in Life-Cycle Analysis studies, all processes within aproduction system that significantly contribute to the overallwater footprint need to be accounted for. If one traces theorigins of a particular product, one will see that supply chainsare never-ending and widely diverging because of the varietyof inputs used in each process step. Depending on thepurpose of a particular study, however, one can decide toinclude only the direct or indirect water use/consumption inthe analysis. By identifying which portions of the supplychain are the most water-intensive, whether that is rawmaterials or entire assemblies, a company is able tounderstand its indirect water consumption and to better assessthe business risk associated with using different suppliers inpotentially water-stressed areas or ecologically sensitiveregions [5].

Ultimately the water splash should be taken in context withother environmental and social impacts, as a waterassessment by itself does not provide all answers or solutions,but provides a better understanding of absolute volumetricneeds, the opportunity costs of the water used, and theimpacts to environments and people that could becomematerial risks. For companies, a water assessment begins totell an important story of dependence and risk, and can bringabout the type of changes necessary for delivery ofsustainable and equitable water management [6].

WATER STUDIES ON VEHICLESUPPLY CHAINBefore starting the life cycle water consumption analysis,literature reviews were completed to determine existing watermodels. Most reports were not concerned with the water



consumption, but chose to focus on either carbon dioxideemissions or energy use. The information available on waterconsumption or use for the automotive supply chain waslimited at best.

Very few articles provided a comprehensive discussion of thewater or materials consumed in the whole supply chain, butwould focus on specific case studies for different areas orgave overviews of total consumption. In some cases, the datafound did provide information on water use for differentmaterials as part of the supply chain, but did not offer anyfurther description on the scope of the footprint to determinethe actual water consumption [7, 8].

In [9], on the life cycle consumption of materials by vehicles,it was determined that the typical water consumption was90,100 liters for materials, and 242,000 liters per vehicle.However, no information was provided to indicate where andhow water was used or even if it took into account recyclingrates of water to determine the actual consumption rate. Nodescription of their water consumption definition was given[9].

A report by Volkswagen focused on the 10 year life-cycleinventory of four VW Golf A4 variants (ranging from800-1,181 kg curb weight) provides detailed assumptions andresults on water use and consumption [10]. The authors reportthat “water consumption of 95 m3 (95,000 liters) per car canbe broken down into that needed for electric powergeneration (46 m3), fuel production (23 m3), car washing (8m3), material production (10 m3) and other factors (9 m3)”[10]. The report also commented on a lack of referencesagainst which comparisons can be made. Specifically, theauthors wonder whether 8 m3 of water used during the 10-year use phase for car washing excessive or below average.They cite the water consumption with of an averagehousehold to be approximately 50 m3 per person per year.

AUTOMOBILE MATERIALCOMPOSITIONA representative model of material composition of a vehiclewas developed to start the water consumption accounting ofthe supply chain. In other words, the raw materials used tomanufacture a vehicle were identified. Given the importanceof having the correct material composition, multiple sourceswere compared which listed the information from variouslocations. The comparison of the data allowed for a betterunderstanding of the material composition (type and amount)in a typical vehicle.

A study on the life cycle analysis of passenger cars by(Spielmann and Althaus 2007) provided the average weightof passenger vehicles sold in Switzerland. The paperinvestigated the environmental burdens of car infrastructure

by expenditures for fuels and operating materials consumedin the manufacturing, maintenance and disposal of the vehiclein Switzerland, but includes material compositions for a carin 2004 by percentage [11]. However, the paper onlyprovided a basis percentage of expected materials withoutgiving more detailed descriptions of what specific materialscomprised these specific percentages [11]. In [12],information is given for the typical weight composition of aNew Ford Galaxy 2.0 I DW10 cDPF Trend edition. Like thepaper on Swiss passenger vehicles [11], the vehiclecomposition in [12] did not provide more detaileddescriptions on specific compositions for values that couldencompass a vast range of materials either.

Comprehensive data for average size automobiles in theUnited States was found in [13]. We use their data in ourassessment because it better presents the typical weight for aUS vehicle and reports the individual material composition[13]. The information on individual metals and plasticsprovided a more detailed basis with which to construct amore accurate and encompassing water footprint assessmentof the supply chain [13]. The U.S. Geological Survey foundthat the typical weight of a US vehicle was 1470 kg in theyear 2004, and made of 131 kg aluminum 975 kg iron [14].Both values match those of the selected study [13].

A summary of the data found in the publicly availableliterature on average automobile material compositions isgiven in Table 1. As can be seen in Table 1, the values for theU.S. vehicles from [13] are consistent and in the samemagnitude as the values of for both the Swiss passengervehicles [11]. Obviously, depending on which vehicle ischosen, the water footprint and supply chain will differ.

WATER CONSUMPTION IN THEPRODUCTION AND PROCESSING OFMATERIALSLITERATURE DATAThe next step was to identify water consumption in liters perkilogram of material. This information includes both thewater consumption in liter/kg of raw materials and the waterconsumption in liter/kg to processes the material. Thepercentage of weight as part of the entire vehicle can also beused to determine the percentage of water consumption fordifferent materials as part of entire water consumption.Ultimately, by examining how much is consumed in themaking of the materials, the final water cost of making avehicle can be determined.

An effort was made to ensure that the data was from sourcesthat were either tied to industry, published in an academicjournal, or from a government agency. The data, collected forwater consumption for steel and aluminum were gathered



from the U.S. Department of energy [15, 16]. Although thesevalues can vary depending on interpretation, and evendepending on which processes are assumed in the analysis,the values selected were from more common processes. Thevalues for some of the other materials, like copper, zinc,magnesium and glass were obtained from sources like theU.S. Department of the Interior or from published work in theInternational Journal of Life Cycle Analysis [17,18,19,20].The data obtained for plastics and rubber were obtained fromeither publicly available data provided directly bymanufacturers or from professional associations [21, 22].

In addition, an effort was made to ensure that the definitionand scope mentioned in the work was consistent with thewater consumption described earlier. Finding such sourcesproved challenging because many of the sources did notprovide a definition for water consumption nor described thespecific processes that led to the given value. We observedthat the terms water use and water consumption are oftenused as synonyms, making the determination of true waterconsumption according to our definition very difficult attimes.

A summary of the data found for the water consumed inmaterials production and processing is given in Table 2. Thenon-ferrous/other metals category listed in Table 2 wasassumed to be primarily magnesium. As can be seen in Table2, steel has a relatively low consumption of water comparedto aluminum. As will be later shown, these two materialshave the largest impact on the overall water consumption forthe materials in a vehicle.

Despite efforts to ensure the use of quality data, uncertaintiesand limitations of data are inevitable and thus restrict aspecific interpretation of results. However, comparisons ofwater consumption of the materials, general trends in thewater consumption, and differences between data from

EcoInvent and from other sources provide a directional trendand areas of concern of water consumption in the supplychain.

Table 2. Summary of Water Consumption for SelectedMaterials and Processing

ECOINVENT AND LITERATURE DATACOMPARISONThe EcoInvent V2.2 LCA database was also used to create analternative model to use as a comparison. Although the dataobtained from the reports in the data base did not containdescriptions of how the water was being used, or how muchwater was consumed, it provided a comparison of the existingtrends [7, 8].

Water data found in EcoInvent for the various materials canbe found in Table 2. For completeness, Table 3 also lists therecord number showing where the data was stored in theEcoInvent database (V2.2). The database includes variouswater inputs, specifically,

• Water, cooling, unspecified natural origin

• Water, lake

Table 1. Materials Composition [11, 13].



• Water, river

• Water, salt, ocean

• Water, salt, sole

• Water, turbine use, unspecified natural origin

• Water, unspecified natural origin

• Water, well, in ground.

The database does not contain any water output or wastewater data. Clearly, the EcoInvent data represents water userather than consumption. Although no detailed explanationcould be found regarding the origins of the “turbine water”listed, it was assumed that this water used in hydropowerproduction of electricity for the materials. In order to remainconsistent, water used for turbines was therefore not includedin the following analyses using EcoInvent data. The values intable 3 refer to extraction of materials and processing of thoseinto semi-finished products. The definition of semi-finishedproduct is not clearly defined, however.

Table 3. EcoInvent V2.2 Water Data for SelectedMaterials

By comparing the information from EcoInvent in Table 3with the literature data in Table 2, a significant difference innumbers can be seen (see Table 4). This large difference,ranging from one to two orders of magnitude, has to domainly with the fact that the data from EcoInvent onlycontains water inputs and no output data. The water data fromEcoInvent reflects water use and as can be seen in Table 4,the differences are significant. The water values in Table 3and 4 are much higher than those reported by others whohave made detailed process studies which include recyclingof water and have more clear definitions on waterconsumption.

Table 4. Comparison of Water Data from EcoInvent andLiterature Sources

Thus, the data from the EcoInvent LCA database onlycaptures water use and does not distinguish between waterthat goes to the sewer system (and can thus be reused) versuswater that is truly lost (consumed) due to evaporation orencapsulation in a material. The water data from theEcoInvent LCA database should therefore not be used for awater consumption assessment, as it will result in a wrongassessment as will be shown in the next section where weapply this data to producing the raw materials for anautomobile.

AUTOMOBILE MATERIAL WATERCONSUMPTIONWATER CONSUMPTION BASED ONLITERATURE DATAAn effort was made to ensure that the information foundincluded recycling of water in all processes and explicitlyexplained what was meant by water consumption and toensure that this water consumption definition was consistentwith that set out in the scope. However, is inevitable thatsome discrepancies in the data could exist. More importantly,the analysis shows a trend in water consumption and explainsin detailed where most of the water is used, specifically inrecovery and processing of the metals, as these tend to be thegreater consumers of water in the supply chain. These valuescan vary depending on the vehicle, model, and even formanufacturing centers depending on individual processes andtechnologies being implemented.

Using the values from literature sources listed in Table 2, anassessment of the water consumption for material productionwas constructed. By using the typical car material



composition in combination with the water consumption forsemi-finished products of the materials composition, wedetermined that the production of one vehicle consumes5,570 liters of water. Most of the water consumption (over75%) in a vehicle occurs in producing steel, aluminum, andrubber (see Table 4 and Figure 1). Although aluminum issecond in terms of material mass in a typical U.S. vehicle, itswater consumption as part of the supply chain is nearly ashigh as that of steel. This water consumption can be reducedby using more recycled aluminum.

Figure 1. Water Consumption Percentages usingLiterature Data

WATER CONSUMPTION/USE BASEDON ECOINVENT DATAA comparison was made with water data for materials foundin the EcoInvent LCA database. The data found only showedthe amount of water that went into a system, without takinginto account recycling rates or reuses of water or breaking

down any steps. EcoInvent reports often mentioned the factthat recycled water was not accounted for in the inventory.Although no definition or actual explanation could be foundregarding water use or water definition in the EcoInventreports, it is clear that the data only reflects water use and notconsumption.

The assessment using the water data from the EcoInventdatabase can be found in Table 5. The results from theEcoInvent database are significantly higher than the literaturesources used for determining true water consumption.

Table 5. Water Use for Vehicle Material Productionbased on EcoInvent Data

Although the amounts differ, compiling the data from theEcoInvent database in a pie chart as shown in Figure 2

Table 4. Water Consumption for Vehicle Material Production



indicates a similar trend between water use and consumption.For instance, the water use is still highest for steel, as a resultof it comprising the largest mass of a vehicle. Aluminum isstill second but glass moves up to third in water consumption.Nevertheless, the amount of water used using data fromtheEcoInvent data base is 30 times higher than that calculatedusing literature based water consumption data. Thisdiscrepancy comes from the fact that the LCA databasesaccount for water use and not water consumption. Waterconsumption due to evaporative losses is typically a fractionof water use.

Figure 2. Water Use Percentages using EcoInvent Data

The differences in the water data for EcoInvent and literaturesources are provided in Table 6. The EcoInvent data basevalues are much higher (30 times) and reflect only waterinputs. Recycling of water can greatly reduce the waterconsumption. The water data from the EcoInvent LCAdatabase should therefore not be used for a waterconsumption assessment, as it will result in wrongconclusions.

Table 6. Water Data Comparison for MaterialProduction for One Average US Vehicle

WATER CONSUMPTION OFMATERIALS PRODUCTION INCOMPARISON TO OTHER LIFECYCLE STAGESA comparison of water consumption in other phases of thevehicle life-cycle process is also made to identify whichphase (production and assembly, use, end-of-life recycling,parts production) has the greatest consumption.

PARTS PRODUCTIONThe making of most standard automobile parts typicallyinvolve a number of similar processes that are adjusted foreach case to yield different products. For metal components,encompassing anywhere from 70 %-85 % of a vehicle byweight, the parts production process can have manyindividual processes for which water can be used andconsumed [13]. However, they can be summarized into majorsets encompassing most of the intermediate categories asshown in Figure 3. The percentages of material flows for thevarious manufacturing stages shown in Figure 3 were basedon a report from Argonne National Laboratory [24]. For someof the metal components, more than one major process willbe applied in the manufacturing of the final product. Forinstance, an aluminum part may be cast, and then machined,so water consumption for both processes must be included inthe analysis.

Similarly to the metal components, the major componentsencompassing the rest of the vehicle, consisting mainly ofplastic, rubber, and glass components, can be categorized intoconsisting of other major manufacturing processes as shownin Figure 4. Unlike metals, the nonmetal parts typically donot have a major secondary process during manufacturing soone manufacturing process can be assigned to a percentage ofthe material for each category.

A summary of the water consumption in the production ofparts is shown in Tables 7 and 8. The amount of material foreach process was found using the material composition of anaverage US vehicle from Table 1 with the processcompositions from Figures 3 and 4. Water consumption datawas gathered from a variety of sources for metal parts[25,26,27,28,29,30,31,32,33,34] and non-metal parts [19, 35,36]. Most sources provide flow rate information and notwater consumption per se. However, 3% to 5% evaporationand loss rates are typical and have been used to determine theconsumption rates when direct information was not available.



The total water consumption for the primary processes is 847liters and the water consumption for the secondary processesis 47 liters for a total water consumption of 894 liters for theparts production for an average US vehicle. The casting ofmetal components has the highest water consumption values.This is because of the higher temperatures required fortreating of the materials, requiring more water for cooling.The machining of steel components consumed the most waterfor the secondary processing of metals. Relative to the waterconsumption in metals, the effect of plastics and rubber isminimal. This is because of the lower temperatures requiredfor treating of the materials, requiring less water for cooling,and of the relatively less energy intensive manufacturingprocesses involved.

A water use assessment was also completed using data fromEcoInvent. The results are given in Table 9. The data formachining, the secondary process, for all of the differentmaterials was not included primarily because the data waspresented in terms of kilogram of material removed (which isunknown). Furthermore, the secondary operations require farless water than the primary processes.

A comparison of water consumption and use results presentedin Tables 7 and 9, respectively, indicates again a factor 30difference between Ecoinvent data and literature data (35,000liters versus 894 liters).

Figure 3. Manufacturing Processes for Metal Parts [24]

Figure 4. Manufacturing Processes for Non-Metal Parts [24]



Table 7. Water Consumption for Primary Processes inParts Production for Average US Vehicle

Table 8. Water Consumption for Secondary Processes inParts Production for Average US Vehicle

Table 9. Water Use for Primary Processes in PartsProduction for Average US Vehicle using EcoInvent

Data

PRODUCTION AND ASSEMBLYIn order to put material production numbers in context, weassessed how much water is used in vehicle production andassembly by OEMs. Water data given in sustainability reportsfrom selected automakers was compiled and summarized inTable 10. In case water use or consumption per vehicle wasnot directly reported by the OEMs, the use/consumption pervehicle was calculated by combining vehicle production datawas combined with water data from the reports.

Examinations of the reports showed that the reporting ofwater data by car makers is inconsistent and do not followstandard definitions. Specifically, the words “consumption”and “use” seem to be used interchangeably. For example, theBMW group (BMW, Mini, Rolls-Royce) reports water“consumption” of 2.31 m3/vehicle produced, see page 87[37].



This includes the process water input for the production aswell as the general water consumption like for sanitationfacilities. In the same report, the BMW group also reportsgroup wide a total water input of 3,418,816 m3 and totalwaste water output of 2,427,754 m3, see page 86 [37]. Thiswould mean a water loss (consumption) of 991,062 m3. Witha reported vehicle production of 1,481,253 units (andignoring the production of 112,271 motorcycles) this resultsin a water consumption (per definition used in this paper) of0.67 m3/vehicle. Most likely the “consumption” of 2.31 m3/vehicle reported by BMW is actually water use. We suspectthat such issues are the results of linguistic translations fromGerman to English because use and consumption are oftenused as synonyms in dictionaries and thesauri. This wouldalso explain the high water consumption of Daimler, whichreports consumptions of 6.0 m3 per car produced and 18.1 m3

per truck produced [38].

Discrepancies were also found in Toyota's reports. For 2009and 2010, Toyota lists water “consumption” of 4.4 m3 and3.7 m3 per vehicle produced in its assembly plants,respectively [39]. It seems likely that Toyota's data alsorepresents water used rather than consumed (and thusevaporated). Discrepancies also exists for Toyota betweendata reported in[39] and [40] for the year 2009, namely 4.4m3/vehicle versus 3.6 m3/vehicle, respectively.

For the US automakers, Ford reports a water use of 4,800liters per vehicle [41]. General Motors did not report waterconsumption per vehicle for their operations. Chryslerreported total water withdrawal of 10,684,609 m3 and totalwater discharge of 7,057,625 m3. With production data of1,571,662 vehicles this results in a water use of 6.80 m3/vehicle and water consumption of 2.31 m3/vehicle.

Table 10. Water Use/Consumption for Vehicle Assemblyand Production for Selected OEMs

*Values directly reported by manufacturer

Clearly, the reporting of water data by car makers isinconsistent and these numbers do not include partsproduction done by suppliers, but merely the in-house

operations. Nevertheless, by comparing the data in Tables 6and 10, the impact of vehicle production operations is lessthan material production with respect to water consumption.

USE PHASETo better understand how the water consumption of materialsproduction is part of the entire vehicle life cycle, acomparison was made with the water consumption in thevehicle's use stage. Some studies have been performedquantifying the water consumption in the production oftraditional petroleum fuels. An overview is presented herein.

The first major life cycle water assessment for petroleum-based fuels was conducted as part of the comprehensiveenergy-water outlook as described in [47], where Gleickassessed water demands for the extraction and refiningprocesses for crude oil and petroleum. Water consumptionwas calculated for onshore exploration and primaryextraction, as well as for secondary and tertiary methodsincluding enhanced oil recovery (EOR) technologies, as wellas for petroleum refining. While water consumption data forpetroleum extraction and refinement in [47] illustrate thewidely varying water requirements for producing gasolineand diesel, there is no information regarding the distributionof these technologies in fuel production pathways in theUnited States.

A more recent study [48] provides a more detailedbreakdown of available fuel extraction technologies based onthe process water flows from which a weighted average ofprimary and additional oil extraction water consumptioncould be determined (and by extension a comprehensiverange of total water consumption for gasoline production)[48]. It outlines the technology shares in onshore and offshorecrude oil extraction in key production regions in the UnitedStates. The authors considered three major petroleum-producing regions in the United States that contribute to 90percent of domestic crude oil production and 81 percent of oilrefining. The authors also considered foreign oil productionby examining water consumption trends in Saudi Arabian oilproduction, as that region has a lack of surface water and lowrecharging aquifer rates [48]. Much of the water used in theoil production process in Saudi Arabia is treated frombrackish or seawater resources and the authors stress thatwater consumption values are based on individual wells andprojects instead of a national distribution. Similarly, theauthors considered petroleum recovered from Canadian oilsands, which accounts for 39 percent of total petroleumproduction in Canada, from where bitumen is either extractedfrom surface mining or in situ extraction methods and isprocessed into synthetic crude oil; as with EOR technologiesfor conventional crude extraction, the authors assessed waterdemands based on a national technology distribution for oilsands production. Water consumption for oil sands crudeproduction was leveraged from Gleick's study (which



includes a brief assessment of oil sands crude production) andlater assessments for surface mining and in situ oil sandsextraction. In addition to specifying the distribution ofprimary and secondary oil recovery technologies in theseregions, the researchers also examine the amount of producedwater stemming from water stored in extracted crude oil thatneeds to be removed from the extracted fuel; some of theproduced water is reintroduced to the well via water floodingand injection in secondary recovery methods.

These water consumption values are summarized below inFigure 5, where a direct comparison shows that waterconsumption varies significantly based on regional conditionsfor conventional crude extraction, while water consumptionin Saudi Arabian and Canadian oil sands production areslightly lower overall.

Figure 5. Water Consumption for Petroleum Productionand Refining for U.S., Canadian, and Saudi Production

(Adapted from [48]).

In this paper, we assume it takes 3.8 liters of waterconsumption to produce one liter of gasoline. Assumingtypical fuel efficiency of 11.7 km/liters of gasoline equal tothe current Corporate Average Fuel Economy standard (=27.5mpg), we can calculate the vehicle's use phase waterconsumption. Driving 100,000 mile (160,000 km) wouldconsume 13,675 liters of gasoline and thus 51,965 liters ofwater. This is 10 times the amount of water consumed inmaterial production or OEM vehicle assembly operations.

Comparing the use phase to material production, using thepreceding fuel data, it would take 17,443 km in the use phaseof a vehicle to equal the 5,570 liter of water consumption inthe production and processing of raw materials for a car.Based on this preliminary data, it would seem that the use ofa car is a more a water intensive process than the productionof a car, similarly to energy consumption and greenhouse gasemissions.

The data from EcoInvent for material production, whichequates to 169,211 liters of water use for material production,

would result in 505,853 km of driving to equate the waterconsumption in the production and processing of rawmaterials in the supply chain. Clearly, using different waterdata-sets and assumptions with respect to water use versuswater consumption can lead to completely differentconclusions with respect to the relative impact of differentlife-cycle stages.

In this context, Volkswagen states that by far the largestproportion of water consumption is accounted for byprocesses in the upstream material supply chain based ontheir Life-Cycle Assessment studies [42]. This statementseems correct if based on EcoInvent data, but incorrect if oneuses direct water consumption data only. For comparison, wehave provided the EcoInvent life-cycle inventory data for 1kg unleaded petrol and diesel at a regional storage in Europein Table 11 which would imply a use of 857 and 690 liters ofwater per kilogram of gasoline and diesel, respectively. Usinga gasoline density of 0.77 kg/liter, this would imply a wateruse of 13,675 × 857 × 0.77 = 8,950,288 liters over the usephase of a gasoline powered car.

If we take out the turbine use water, we arrive at about 14 and13 liters per kilogram gasoline and diesel, which seems morerealistic, but still 2 to 4 times higher than from [48].

Table 11. Water Consumption/Use for 1 kg Gasoline(Petrol) and Diesel Production per EcoInvent

END OF LIFE RECYCLINGAn assessment of the amount of water consumed at the end oflife for a mid-sized gasoline powered US vehicle was alsoperformed. Published documents were used to developdiagrams of how the car material flows at the end of life for avehicle. Various papers contained valuable information onthe typical processes and some of the values for materialflows [10, 13, 49,50,51,52], but typically did not contain dateon water use. Companies involved in the design andmanufacturing of recycling equipment like shredders and sinkfloat separators, provided most of the water intake, and water



consumption values for the different machines and processes[53,54,55,56,57]. Although much of the required informationis provided publicly through the specifications for theirequipment, individual engineers confirmed the water valuesfor the different processes and assumptions.

According to our analysis based on shredder machinery andother industry data, 259 liters of water is consumed for thedismantling, shredding, and processing of a US vehicle at theend of life. Even though the processing of the plastics canrequire significant amounts of water, with the use of wastewater treatment technology, much of it can be recycled andreused.

End of life data found in the EcoInvent V2.2 databaseindicates 3,039 liters of water for end of life vehicle recyclingand disposal. The EcoInvent supporting information did notprovide any background information regarding whatassumptions or definitions were given for the water numbers.The description merely said that the values representedinformation for the bulk materials and explained that therecould have been uncertainty in methodology. There is also nodescription of what happens to that water after it goes into thesystem. Using publicly available machinery information, itwas found that the water use would be 4,346 liters, most ofwhich is part of the shredding residue separation process,which is in the same scope as that of the EcoInvent database.The biggest discrepancies between the EcoInvent data andpublicly available information were found in the water intaketo the shredding operation. The EcoInvent database had 1,781liters for water intake, while machinery data suggested avalue of 23 liters.

WATER CONSUMPTION SUMMARYIn Table 12, the overall water consumption of a vehicle isgiven using Ecoinvent as well as literature data discussed inthis paper. No definitive total has been given, but someconclusions can be made. As can be seen, in both cases, theend of life processing is rather insignificant to the other lifecycle phases. The use phase dominates the assessment usingthe literature data. It also dominates the EcoInvent basedassessment if the full water use including turbine water isincluded, but the use phase becomes less important than thematerial production phase if this turbine water is excluded.This clearly indicates that significant uncertainty andambiguity exists in the LCA databases and literatureregarding water use and consumption data.

Table 12. Water Consumption/Use for an Average USVehicle Life Cycle

SUMMARY AND CONCLUSIONSThis paper focused on an assessment of the amount of waterconsumed in the production, use and recycling for a mid-sized gasoline powered US vehicle. Although water use istypically metered at the factory level, water consumption(i.e., water lost through evaporation and/or incorporation intoa material, part, and/or product) is much harder to quantifyand requires data on water discharge in addition to waterinput. As was shown, the difference can be an order ofmagnitude or more.

According to our analysis, 5,570 liters of water is consumedfor the extracting and processing of materials to produce atypical US vehicle. The 5,570 liters is less than theapproximately 10,000 liters reported in [10] for the smallerGolf vehicles' material production, but is directionally in thesame order of magnitude. In comparison, water consumed forfuel production is almost 10 times more, namely, 52,000liters for 160,000 km with a corporate average fuel economyof 11.7 km/liter gasoline. Water consumption in partsproduction was significantly less at 894 liters per vehicle withcasting being the primary consumer of water. Vehiclerecycling is relatively insignificant at 259 liters/vehicle. Theassembly and production operations seem to be moresignificant than parts production, but the data reported byOEMs is very inconsistent and lack proper definition of useversus consumption.

Using water data found in the EcoInvent V2.2 database wecalculated that 169,212 liters of water are used in theproduction of materials to produce one car. The comparisonshowed that the water numbers in the database weresignificantly (30 times) higher than those found ingovernment documents, in published papers, and in publiclyavailable company information. This can be explained by thefact that the EcoInvent water numbers only reflect waterinput data and do not include discharge or recycling rates. Asstated in the paper, the EcoInvent water data is even higher ifthe turbine use water category was also included in ourassessment. We did not include this category because it isalmost certainly related to indirect electricity production.

Similarly, water for parts production processes usingEcoInvent data was also significantly higher (35,000 liters)



than the water consumption calculated using literature data(894 liters). Whereas the use phase dominated the life cyclein the water consumption assessment per literature data, theassessment using EcoInvent water data for gasolineproduction (and excluding turbine use water) resulted in alower water amount than used for material productions. Thiswould indicate that material production is more importantthan the use phase. Given the ambiguity of the data inEcoInvent, we would question such a conclusion.

Overall, end of life recycling has a relatively low overallimpact, ranging from 259 liter of water consumption (as perliterature data) to 3,039 liters (as per EcoInvent data).

Despite the variability and uncertainties still observed as partof this assessment, directional trends and areas of concern ofthe water consumption in a vehicle life cycle can beobserved, however. As it was shown, in material production,most of the water was consumed in the production of steel,aluminum and rubber.

It is clear that further research is needed before any robustconclusions on life cycle water consumption can be drawn.The data uncertainty is still very significant and definitions/system boundaries of the different literature sources are notfully consistent.

Most of the data presented in the paper illustrates the use ofthe best available technology by U.S. standards. Most of theinformation found was based on the U.S. industry which mustmeet certain EPA environmental regulations so the use ofwastewater recycling seemed a common trend. This trendmay not exist in other localities such as low cost countries,however, where many automotive suppliers reside. This maymean that the actual water “splash” from materials productionmay be higher than stated in this paper.

Going beyond a water inventory (in terms of consumptionand/or use) for various vehicle types and models, the nextstep is to assess the actual impact. The impact of waterconsumption varies by region and locality, and adifferentiation would be needed whether the waterconsumption actually happens in water scare regions or not.In addition, the quality of water (input and output) isimportant: obviously the consumption of drinkable water inwater scarce regions is much more important than theconsumption of non-drinkable water. It remains to be seenwhether a life cycle approach - adding up generic figuresalong the life cycle - will be the right approach.

For all these reasons, care and caution should be taken whenusing pure total figures of water consumption or water use.

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CONTACT INFORMATIONProfessor Bert BrasGeorge W. Woodruff School of Mechanical EngineeringGeorgia Institute of TechnologyAtlanta, GA 30332-0405

ACKNOWLEDGMENTSThe material presented in this manuscript is based onresearch done within the Sustainable Design andManufacturing Program of the Manufacturing ResearchCenter at the Georgia Institute of Technology incollaboration. The authors would like to thank all those whohave contributed their invaluable input and support, includingbut not limited to David Berdish, Tim Wallington, SherryMueller and Wulf-Peter Schmidt from the Ford MotorCompany.

The Engineering Meetings Board has approved this paper for publication. It hassuccessfully completed SAE's peer review process under the supervision of the sessionorganizer. This process requires a minimum of three (3) reviews by industry experts.

All rights reserved. No part of this publication may be reproduced, stored in aretrieval system, or transmitted, in any form or by any means, electronic, mechanical,photocopying, recording, or otherwise, without the prior written permission of SAE.

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Positions and opinions advanced in this paper are those of the author(s) and notnecessarily those of SAE. The author is solely responsible for the content of the paper.

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http://awcservice.com/shredder_technology_htm.htm

http://awcservice.com/shredder_technology_htm.htm

http://www.metso.com/recycling/mm_recy.nsf/WebWID/WTB-070201-2256F-F0B34?OpenDocument&mid=925DAA637E899E1CC22575AE004F0D1F




http://www.cwc.org/hdpe/hdpe_bp.htm

http://www.cwc.org/hdpe/hdpe_bp.htm

http://www.navarini.com/wanne_e.htm

http://www.navarini.com/wanne_e.htm

http://www.prsi.com/index.cfm?event=ViewPage&contentPieceId=4325

http://www.prsi.com/index.cfm?event=ViewPage&contentPieceId=4325

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