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Global Warming Potential and Fossil-Energy Requirements of Biodiesel

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  2489 r 2010 American Chemical Society  pubs.acs.org/EF Energy Fuels  2010,  24,  2489  –  2499  :  DOI:10.1021/ef100051gPublished on Web 03/21/2010 Global Warming Potential and Fossil-Energy Requirements of BiodieselProduction Scenarios in South Africa A. L. Stephenson,* ,† H. von Blottnitz, ‡ A. C. Brent, § J. S. Dennis, † and S. A. Scott  ) † Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA,United Kingdom,  ‡ Department of Chemical Engineering, University of Cape Town, Rondebosch 7701, South Africa, § Centre for Renewable and Sustainable Energy Studies, School of Public Management and Planning, Stellenbosch University,Lynedoch, Stellenbosch 7603, South Africa, and   ) Department of Engineering, University of Cambridge, Trumpington Street,Cambridge CB2 1PZ, United KingdomReceived January 16, 2010. Revised Manuscript Received March 5, 2010 Life cycle assessment has been used to investigate the global warming potential (GWP) and fossil-energyrequirements of the production of biodiesel from canola (oilseed rape), soybean, and sunflower oils in SouthAfrica. The effect of scale and transportation of raw materials and products was investigated, as well as theeffect of ploughing grassland and using irrigation to grow oil crops. This research shows that the GWP andfossil-energyrequirementsofbiodieselproducedinSouthAfricavarywidely,dependinguponpredominantlythe crop yield, the requirement for irrigation, and the ploughing of uncultivated land. For the best casescenario, where no uncultivated land is newly ploughed and irrigation is not required, biodiesel has a GWP20 - 36%lowerthanthatofthefossildieselmixcurrentlyusedinSouthAfricaandafossil-energyrequirement50 - 62%lower.However,intheworst casescenario,whereoil-seedcropsaregrownonnewly cultivatedlandrequiring substantial irrigation, this paper concludes that biodiesel can have a GWP significantly higher thanSouth African fossil diesel. The scale of operation and transport distances involved are shown to have littleinfluence on the GWP and fossil-energy requirement of biodiesel produced in South Africa. 1. Introduction The global use of biofuels as an alternative to fossil-derivedtransport fuels is increasing. In 2003, the European Union(EU) releasedthe EU Biofuels Directive,whichset a target formember states to achieve a 5.75% market share of biofuels by2010, calculated on the basis of the energy content of all petrolanddieselusedfortransport. 1 In2009,thistargetwasrevisedinthe EU Renewables Directive, which calls upon each memberstatetoensure10%oftheenergyusedbyitstransportindustryis produced in a renewable manner by 2020. 2 The federalgovernmentoftheUnitedStateshasrecentlysetacommitmenttoincreasetheuseofbioenergy3-foldinthenext10years. 3 Thebiofuels industry is well-developed in some countries, such asGermany and Brazil; however, other countries are just em-barking on new biofuel strategies. For example, the BiofuelIndustrialStrategyoftheRepublicofSouthAfrica, 4 publishedin December 2007, aims at achieving a 2% penetration of biofuels in the national liquid fuel supply, calculated on thebasis of the total volume of all road transport fuels used peryear,by2012.Infact,aswellassupplyingfuelforusewithinthecountry, some companies in South Africa are planning toexport their fuels to Europe. 5 Accordingly, many new biofuelproduction facilities are being planned in South Africa, atdifferentscalesandusingavarietyoffeedstocks.Itisthereforetimely to study the sustainability of the different supply chainsthat could be used to produce biofuels in South Africa.Biodieselisgenerallyproducedbythetransesterificationofatriglyceride (vegetable oil) with an alcohol (methanol orethanol) in the presence of a base catalyst (usually sodiumhydroxide or potassium hydroxide) to produce the respectivefatty acid alkyl ester (biodiesel) and glycerol. 6 Transesterifica-tion involves three reversible reactions, whereby the triglycer-ideisconvertedsuccessivelytodiglyceride,monoglyceride,andglycerol,consuming1molofalcoholineachstepandliberating1 mol ofester.Theglycerol co-productcanberefinedandsoldto the pharmaceutical industry; however, this market is cur-rently saturated, and the refining process is complicated andenergy-intensive. In South Africa, there is significant researchinto alternative uses for glycerol, e.g., to produce biogas byanaerobicdigestion; 7 however,atpresent,itismostcommonlysold for use as a fuel in industrial furnaces. 8 The four principal oils used by the biodiesel industry arecanola (rapeseed), sunflower, soybean, and palm oils, 6 whileattention is also currently turning to the use of the nonfoodfeedstock,  Jatropha curcas . 9 The warm, temperate climate in *To whom correspondence should be addressed: Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB21EW, U.K. Telephone: þ 44-(0)1223-748199.Fax: þ 44-(0)1223-336362.E-mail: als53@cam.ac.uk.(1) Directive 2003/30/EC of the European Parliament and of theCouncil.  Off. J. Eur. Union  2003 ,  123 , 42 - 46. (2) Directive 2009/28/EC of the European Parliament and of theCouncil.  Off. J. Eur. Union  2009 ,  140 , 16 - 62. (3) Demirbas, A.  Energy Convers. Manage.  2008 ,  49  (8), 2106  –  2116. (4) Department of Minerals and Energy. Biofuels Industrial Strategyof the Republic of South Africa. 2007 . (5) Phytoenergy. Environmental Impact Assessment and Environ-mental Management Plan for the Proposed Biodiesel Plant in EastLondon and Associated Activities. 2008 . (6) Mittelbach, M.; Remschmidt, C.  Biodiesel  ; The ComprehensiveHandbook , 1st ed.; Graz University: Graz, Austria, 2004; pp 6 - 9. (7) Verster, B. Private communication. University of Cape Town,South Africa, 2008 . (8) Murray, N. Private communication. Biodiesel Centre, Bellville,South Africa, 2008 . (9) Achten, W. M. J.; Verchot, L.; Franken, Y. J.; Mathijs, E.; Singh,V. P.; Aerts, R.; Muys, B.  Biomass Bioenergy  2008 ,  32 , 1063  –  1084.  2490 Energy Fuels  2010,  24,  2489  –  2499  :  DOI:10.1021/ef100051g  Stephenson et al. South Africa is suitable for growing canola, sunflower, andsoybean crops. Therefore, these crops are considered to bemostappropriatefeedstocksforbiodieselproductioninSouthAfrica 10 and are investigated in this study. Canola and sun-flower crops have the potential to produce more biodiesel perhectare than soybeans, owing to their higher content of oil;however, factors specific to the land and climate (e.g., avail-ability of water) determine the most appropriate feedstock tobe grown in a particular region. The Biofuel IndustrialStrategy aims at growing these crops on land classified asunder-used but with high potential; significant areas of theformer homeland regions of South Africa fall in this cate-gory. 4 (Anyofthe10regionsdesignatedbySouthAfricainthe1970s as semi-autonomous territorial states for the blackpopulation. The black homelands were dissolved and re-incorporated into South Africa as part of the 1994 transitionto democracy.) This area is predominantly grassland andwoody savannah, and it currently has three main uses:communal arable land, agricultural land, and arable stateland. 11,12 Communal arable land is mostly used for subsis-tencefarming,animalgrazing,andgrassland.Theagriculturalland has recently been acquired by new farmers under theLandReformprogram; 12 mostofthislandisleftuncultivatedand used for grazing. The arable state land has not yet beencultivated for agricultural use and is currently either used forgrazing or left for grass. 12 The Biofuel Industrial Strategy isunclear about what proportion of the land is already used asfarmland;however,itisevidentthatsignificantproportionsof grasslands and grazing lands will require cultivation to pro-videthelandrequiredtogrowtheoilseedcrops.Forexample,intheEasternCapeprovince,thereareplanstouse150000haof underdeveloped land to grow canola crops and 100000 hato grow soybean crops specifically for the production of biodiesel, as part of an integrated rural development pro-gram. 13 Over 95% of this land is currently uncultivated; 13 therefore, it is important to quantify the effect on the globalwarming potential (GWP) of the resulting biodiesel of con-verting this land to arable land for the cultivation of oil-seedcrops.This paper uses life cycle assessment (LCA) to investigatethe GWP and fossil-energy requirements of biodiesel produc-tion in South Africa, at each stage, from the production andsupply of the raw materials to the point of supply of the fuel,for the three oilseed crops. The effect of the scale of produc-tiononGWPandfossil-energyrequirementshasbeenstudied,aswellastheeffectofploughinggrasslandandusingirrigationtogrowoilcrops.TheuseofthebiodieselinbothSouthAfricaand the U.K. is considered. 2. Materials and Methods 2.1. Definition of Scale.  The scale of production was definedin terms of the production capacities of typical processplants across the world. 14 “Large scale” was defined as a plantproducingmorethan100000tons/yearofbiodiesel;albeit,nosuchplantcurrentlyexistsinSouthAfrica.“Mediumscale”wasdefinedas a plant producing between 10000 and 100000 tons/year of biodiesel, with “small scale” production being between 1000 and10000tons/yearofbiodiesel.Finally,“microscale”productionwasdeemed to be a plant producing less than 1000 tons/year of biodiesel. Operating conditions for medium-, small-, and micro-scale plants in South Africa were obtained during site visits. 2.2. LCA.  A LCA was undertaken according to the Interna-tional Organization for Standardization (ISO) standards ISO14040:2006 15 and ISO 14044:2006 16 via the sequential stages of (i) goal and scope definition, (ii) inventory analysis, (iii) impactassessment, and (iv) interpretation and reporting, as describedbelow. The actual analysis was undertaken using the GaBi 4.3LCA software package. 17 2.2.1.GoalandScopeDefinition.  Inthispaper,twofunctionalunits(thebasisforcomparison)aredefined:(i)1tonofbiodieselthat has been delivered to a South African customer by road,blended with fossil-derived diesel to the desired fractionalvolume, and combusted in a typical, compact-sized car engineand (ii) 1 ton of biodiesel that has been delivered to the U.K. bysea,blended tothedesired fractionalvolumewith conventional,fossil-derived diesel, delivered to a filling station, and com-busted in a typical, compact-sized car engine. The results arebased on information gathered for the time period of 2006 - 2009. Process chains have then been used to summarizethe consequent main activities in the production of this func-tionalunit.TheseareshowninpanelsaandbofFigure1fortherespective sizes of plants and are discussed below. The “controlvolume” in thisstudy encompasses allof thestages directlyusedto produce biodiesel (i.e.,the foreground system, includingcropproduction,oilextraction,andesterification)andalsotheback-ground system, which provide the materials and energy used bythe foreground system. 2.2.2. Inventory Analysis.  Quantitative mass and energy bal-ances were performed over each control volume. Informationregarding the agriculture of canola crops was gathered from afarmintheWesternCapeprovinceofSouthAfrica.Sitevisitstoa South African fertilizer manufacturer and the ElsenburgAgricultural College, Stellenbosch (Western Cape province),werealsousedtoobtainnecessaryinformationontheagronomyofcanola,soybean,andsunflowerinSouthAfrica.Quantitativeinformation on both large- and small-scale oil extraction pro-cesses was required for the study. At the time of the datacollection, most of the biodiesel produced in South Africa usedwaste cooking oil as the feedstock. From discussions withbiodiesel producers, it was decided that solvent extractionmethods would most likely be used to provide the oil feedstockfor the medium-scale plants, while cold-pressing techniqueswould be used for small- and microscale generation. Operatinginformation from oil extraction facilities situated in SouthAfrica was not available for this study. However, informationfrom standard large-scale, solvent extraction and small-scale,cold-pressing facilities in the U.K. was available. 14 After theavailable extraction facilities in South Africa were investigated,it was decided that the processes would be similar to thoseemployed in the U.K.; therefore, this process information wasincorporated in the study. Process information from three,anonymous, biodiesel production plants operating at differentscales was considered. These were (i) plant A, which has thecapacity to produce ∼ 60000 tons of biodiesel per year, (ii) plantB, with a capacity of  ∼ 8000 tons of biodiesel per year, and (iii) (10) Nolte, M. Commercial biodiesel production in South Africa: Apreliminary economic feasibility study. Master’s Thesis, University of Stellenbosch, Stellenbosch, South Africa, 2007 . (11) Kingwill, R.; Sapsford, P.; Barnard, J.; Cartwright, A. LandIssues Scoping Study: Communal Land Tenure Areas: Key Issues.Department for International Development Southern Africa (DFID-SA). 2003 . (12) Letete, T. Private communication. University of Cape Town,South Africa, 2008 . (13) Council for Scientific and Industrial Research (CSIR). InternalDiscussions and Documentation, Pretoria, South Africa, 2008 . (14) Stephenson,A.L.;Dennis,J.S.;Scott,S.A. ProcessSaf.Environ.Prot.  2008 ,  86 , 427  –  440. (15) International Organization for Standardization (ISO). ISO14040:2006. Environmental Management. Life Cycle Assessment. Prin-cipals and Framework. 2006 . (16) International Organization for Standardization (ISO). ISO14044:2006. Environmental Management. Life Cycle Assessment. Re-quirements and Guidelines. 2006 . (17) PE International. GaBi 4. Product Sustainability. Leinfelden-Echterdingen, Germany, 2008 .  2491 Energy Fuels  2010,  24,  2489  –  2499  :  DOI:10.1021/ef100051g  Stephenson et al. plant C, with a capacity of  ∼ 300 tons of biodiesel per year. Aninventory table was generated for each plant using the collatedinformation,showingtheresourceusageandalloftheemissionsassociated with the production of 1 ton of biodiesel. 2.2.3. Impact Assessment and Interpretation.  Using the LCAsoftware, it was possible to formulate the inventory table into asetofenvironmentalthemesbasedontheEDIP2003methodol-ogy 18 using estimates of how much each input and emissioncontributes to certain environmental impacts. The EDIP 2003methodology was chosen because it was the most up-to-datemethodology available for the study. Moreover, it was devel-oped in concert with the ISO standards ISO 14040:2006 15 andISO 14044:2006 16 and is considered to be one of the mostcomplete and consistent methodologies available. 19 This paperreports on the GWP category (in kg of CO 2  equiv) and fossil-energy requirement (in GJ). The LCA software included littledata that was specific to South Africa. To overcome thisproblem, major inputs were identified using sensitivity analysisand adapted to suit the South African context. Specifically, theenvironmental burden of electricity was calculated by assumingthe South African electricity mix to be 91% coal, 4% hydro-electricity, and 5% nuclear, 20 on an energy basis. Further, thediesel used for transporting the raw materials and products wasassumed to consist of 65 vol % refined crude oil and 35 vol %synthetic fuel, with 15 vol % being produced by Sasol’s coal toliquid(CtL)plantinSecundaand20vol%fromthegastoliquid(GtL) plant operated by PetroSA company in Mossel Bay. 21,22 2.3.ReferenceSystem. Itisimportanttousereferencesystemsfor any part of the process chain that would have an alternativeuse and a consequent different environmental burden if it werenot used in the process under assessment. In the production of biodiesel, a key issue is the alternative use of the land used togrowthecropsrequiredforbiodiesel;itisparticularlyimportanttoknowwhetherthelandwouldotherwisebeleftuncultivatedif it were not used to produce energy crops, because changinguncultivated land, such as grassland, to manage arable landgrowing annual crops results in the carbon content of the soildecaying at an exponential rate, toward a new, lower carboncontent, characterized by a time constant of around 10 - 20years, 23 and therefore releasing substantial quantities of carbonthatwerepreviouslystoredinthesoil.Asnotedabove,itislikelythat a significant proportion of the land required to grow the oilseed for biodiesel production will be grazing land or grassland,which will require new cultivation. In this work, both the best Figure 1.  Process chains for the production of biodiesel from the oil seeds, canola, soybean, and sunflower, in South Africa: (a) medium scaleand (b) small- and microscale. Sun = sunflower (a and b denote current and recommended agricultural practices, respectively). (18) Hauschild, M.; Potting, J. Spatial Differentiation in LifecycleImpact Assessment ; The EDIP 2003 Methodology. Guidelines fromthe Danish Environmental Protection Agency, Copenhagen, Denmark,2004 . (19) Bare, J. C.; Gloria, T. P.  J. Clean Prod.  2008 ,  16 , 1021  –  1035. (20) Winkler, H. Energy Policies for Sustainable Development inSouth Africa. Options for the Future. Energy Research Centre, Uni-versity of Cape Town, Cape Town, South Africa, 2006 . (21) Fitton, J. Private communication. Sasol, Johannesburg, SouthAfrica, 2008 . (22) SouthAfricanPetroleumIndustryAssociation(SAPIA).AnnualReport. 2006 . (23) Thomson, A.; Mobbs, D. Land Use Change and Soil Carbon inthe U.K.: Current and Future Modeling Approaches. Centre for Ecol-ogy and Hydrology. Natural Environment Research Council. Cost 639/v Workshop, Copenhagen, Denmark, 2008 .  2492 Energy Fuels  2010,  24,  2489  –  2499  :  DOI:10.1021/ef100051g  Stephenson et al. and worst case scenarios have been investigated. The best casescenario corresponds to using idle arable land, which is alreadycultivated, therefore using it to grow energy crops would notreleaseanysignificantcarbonemissionsfromthesoil.Theworstcasescenariowouldmeanthelandrequiredfortheenergycropswould come from ploughing uncultivated grassland.The Intergovernmental Panel on Climate Change (IPCC)Guidelines for National Greenhouse Gas Inventories wereused 24 to determine the quantities of carbon dioxide emittedfrom soils because of the conversion uncultivated grassland inthe homeland regions to arable land growing annual crops.Despitetheexponentialreleaseofcarbon,inthisstudy,thetotalemission was split evenly over 20 years, as recommended by theIPCCfortheconversionofuncultivatedlandtoarableland, 24 todetermine anaverageenvironmental performanceof thebiofuelover the time frame. When converting from grassland with lightto highly weathered soils, typical of soils in the homelands, 25 tolong-term cultivated land, in a warm, dry, and temperateclimate,atotalCO 2 emissionof18tonsofCO 2 /hawasassumed,corresponding to 0.9 tons of CO 2  ha - 1 year - 1 over 20 years. 24 There is, however, much uncertainty associated with the valuesused because the carbon emissions are highly dependent uponthe type of soil; therefore, further research is required for thecarbon dioxide emissions from ploughing the specific land to becultivated for energy crops. 2.4. Allocation Methods.  The production of biodiesel gener-ates the co-products seed meal and glycerol; one purpose of allocation is to determine, rationally, how a particular environ-mental burden, e.g., GWP, should be shared among the biodie-sel and co-products. A preferred method of allocation is directsubstitution. 26 However, to use direct substitution, the productbeing replaced must already be satisfied by other processes.Thus, this approach cannot be taken when the product beingreplaced is always regarded as a co-product, byproduct, orwaste. If direct substitution cannot be used, simpler allocationmethodscanbeapplied,includingallocationbyeconomicvalue,calorific value,ormass.Inthesecases,itispreferable toallocateburdens on the basis of economic value because economicrelationships reflect socioeconomic demands. 27 The allocationprocedures adopted in this study are described below.In South Africa, seed meal is generally used as an animal feed.Animalfeedisusuallyproducedasaco-productofotherprocesses,making allocation by substitution difficult. Therefore, the alloca-tion of environmental burdens for the meal was calculated usingquoted market prices, as shown in the following equation:allocation  ¼  A γ A γ þ B ε ð 1 Þ Here, A isthemarketpriceofmealwhenusedforanimalfeed, B is the market price of seed oil,  γ  is the proportion of the seed bymass converted to mass of meal, and  ε  is the proportion of theseed by mass converted to mass of oil. At present, significantquantities of animal feed are imported by South Africa; how-ever, in the future, the animal feed market may become floodedas increasing quantities of seed meal are produced as a bypro-duct of biodiesel production. In this case, the meal may beexported, or alternative uses, such as its combustion for energygeneration, may be investigated.It has been assumed that glycerol is used as a fuel in indus-trial furnaces. Allocation by substitution has been employed,assuming the thermal energy produced displaced the energyproduced from combusting heavy fuel oil.As well as allocating the environmental burden betweenbiodiesel and its co-products, the burden associated with theusage of land must also be allocated to the different agriculturalproducts produced on the land, as crops are rotated each year.For example, in the Eastern Cape, canola can be grown on thesame land every 4 years while being rotated with other, non-biodiesel crops. 13 In this study, if a burden was due to a non-annual treatment of or an emission from the land, the totalburden was split equally among the crops grown on the landduring that time period. For example,  ∼ 4 tons of limestone isapplied to South African arable soils approximately every 5years, 28 releasing CO 2  when it neutralizes acidic soils. The totalburden from the addition of the 4 tons of limestone was dividedby 5 and allocated to each annual crop.As already mentioned, the impact of the conversion of grass-land to cultivated land is investigated in this paper. Because theenergy crops require rotation with non-energy crops, additionalland as well that used to grow the energy crops may requirecultivation to provide adequate areas of arable land for therotationofthecrops.TheGWPburdencausedbyploughingtheland allocatedto the biodiesel wascalculated from the landareathat the biodiesel crop occupies; the burden caused by anyadditionallandrequiringploughingbecauseofthecroprotationrequirement was allocated to the non-energy crops. 2.5. Indirect Land-Use Change.  Indirect greenhouse gas emis-sions can also be attributed to biofuels if the production of conventional agricultural commodities is displaced by the culti-vation of bioenergy crops. The reduction in the production of the agricultural commodities must be met by increased produc-tionelsewhereorbytheuseofalternativeproducts;accordingly,this may lead to the change of land-use elsewhere, which mayhave a considerable environmental burden associated with it(e.g., deforestation). For example, if grazing land in SouthAfrica were converted to arable land to grow bioenergy crops,land elsewhere may be required for grazing, causing a change inland use. In a LCA, it is difficult to quantitatively account forsuch situations; therefore, indirect gashouse emissions were notincluded in this study. 2.6. Nitrous Oxide  ( N 2 O )  from Soils.  Nitrogenous fertilizerscontribute to the GWP of biodiesel because (i) their productionis energy-intensive, (ii) their production releases significantquantitiesofnitrousoxide,and(iii)aproportionofthenitrogenadded to agricultural soils, in the form of fertilizer, is convertedto N 2 O, a potent greenhouse gas, and released to the atmo-sphere. 29 There is considerable uncertainty associated with thevaluesusedfortheemissionsofN 2 Ofromsoilsusedforgrowingoil crops. 30 These emissions vary widely and depend upon anumber of factors, such as soil type, climate, tillage, fertilizerrates, and crop type. It was decided to use the 2006 IPCCGuidelines for National Greenhouse Gas Inventories to deter-mine nitrous oxide emissions, 31 which consider direct nitrousoxide production from increased nitrification and denitrifica-tion rates in soils, as well as indirect production from nitrateleachingandrunoff,andthevolatilizationofNasNH 3 andNO x followed by their accumulation in soils, lakes, and other waters.The 2006 IPCC Guidelines suggest a value of the conversionfactor ( C  F ) of 1.1 wt % of synthetic nitrogen inputs to N 2 O - N (24) Intergovernmental Panel on Climate Change (IPCC). Agricul-ture, Forestry and Other Land Use. IPCC Guidelines for NationalGreenhouse Gas Inventories. 2006 ; Vol.  4 . (25) Nagle,G.  Development andUnderdevelopment: Focuson Geogra- phy ; Nelson Thornes: Cheltenham, U.K., 1999. (26) Department for Environment, Food and Rural Affairs(DEFRA). Evaluation of the comparative energy, global warming andsocio-economiccostsandbenefitsofbiodiesel.Report20/1.London,U.K., 2003 . (27) Clift, R.  Inst. Chem. Eng. Environ. Prot. Bull.  1998 ,  53 , 9  –  13. (28) Murray, N. Private communication. Biodiesel Centre, Bellville,South Africa, 2007 . (29) Crutzen, P. J.; Mosier, A. R.; Smith, K. A.; Winiwarter, W. Atmos. Chem. Phys. Discuss.  2007 ,  7  , 11191  –  11205. (30) Mortimer, N. D.; Elsayed, M. A. North East Biofuel SupplyChain Carbon Intensity Assessment. North Energy Associates Ltd.,Stocksfield, U.K., 2006 . (31) IntergovernmentalPanelonClimateChange(IPCC).N 2 OEmis-sions from Managed Soils, and CO 2  Emissions from Lime and UreaApplication, IPCC Guidelines for National Greenhouse Gas Inven-tories. 2006 ; Vol.  4 .
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