Preventing brominated flame retardants from occurring in recycled expanded polystyrene: comparing Norwegian visual sorting with advanced screening methods
Heidi Knutsen
a,*, Hans Peter H. Arp
a,baNorwegianGeotechnicalInstitute(NGI),P.O.Box3930UllevålStadion,N-0806,Oslo,Norway
bNorwegianUniversityofScienceandTechnology(NTNU),DepartmentofChemistry,NO-7491,Trondheim,Norway
ABSTRACT
Thereisinternationalinteresttoincreaserecyclingratesofexpandedpolystyrenefoam(EPS).Extensiveuseof brominatedflameretardants(BFRs),however,presentsahindertothis.Ifuncontrolled,hazardousBFRscould persistinrecycledEPSleadingtonewexposureroutes,includinginmaterialssuchasEPSpackagingwherenoflame retardantsarerequired.ThisstudylookedatEPSfoamcollectedfromNorwegianMunicipalWasteSortingFacilities, visuallysortedas"whiteEPSfoam",mostlyderivedfrompackaging.BrominewasanalysedbyX-rayfluorescence (XRF), and selected BFRs including hexabromocyclododecane (HBCDD) were analysed by targeted gas chromatography-massspectrometryanalysis.ResultswerecomparedwithEUandUNEPlowpersistentorganic pollutantconcentrationlimits(LPCLs).Oneoutof120samplescontainedHBCDDoverestablishedLPCLs,likely attributabletomissortedinsulationEPS.Further,nofalsenegativesoccurred,asallsamplesinwhichtargetBFRs werequantifiedhadXRF-detectablebromine.VisualsortingofwhiteEPSpackagingfoam,withtheuseofXRFin uncertaincaseshasthepotentialofminimizinghazardousBFRsinrecycledEPS.Thecontextofnationalsorting infrastructureandcomplianceshouldbeacentralfeatureoffuturestudiesinvestigatinghowBFRsorother hazardoussubstancesentertheglobalcirculareconomy.
ARTICLE INFO Keywords:
Recycling EPS
Unintentionalcontaminants Sorting
BFR
1. Introduction
Expandedpolystyrene(EPS)foam,havingaglobalproductionof10 million metric tons in 2018 (Garside, 2019), is widely used in the construction and packaging sectors (Abdallah et al., 2018). As a packagingmaterial,EPSfoamislightweight,rigidandabletowithstand heavyloadsrelativetoitsmaterialcomposition(2%polystyrene,98%
air)(Samperetal.,2010).Fromacirculareconomyperspective,EPSfoam representsanimportantwastestreamforwastereduction,reuse,redesign andrecycling(Korhonenetal.,2018;Kraletal.,2013).Moreefficient recyclingstrategiescouldalsohelpreduceexposureofhazardousEPS litter(Turner,2020).RecyclingofEPSistechnicallypossible,asmethods areinplacetoconvertEPStoitsmonomerstyrene(Stenmarcketal., 2017).
ManyEPSproductscontainhazardousbrominatedflameretardants (BFRs)likehexabromocyclododecane(HBCDD)(Turner,2020).Dueto itspersistence,toxicityandecotoxicity,HBCDDwasin2008listedonthe EuropeUnion(EU)'sREACH(Registration,Evaluation,Authorisationand RestrictionofChemicals(EC1907/2006)CandidateListofsubstancesof very highconcern(SVHC)asa persistent,bioaccumulative andtoxic
(PBT)substance(Article57d),andin2013itwasaddedtotheStockholm ConventiononPOPs(UN,2013).Further,theEUandUnitedNations Environment Programme (UNEP) have introduced a low persistent organicpollutant(POP)concentrationlimit(LPCL)of0.1%byweight(or 1000mg/kg)forrecyclingofcertainbrominatedcompounds,including HBCDD,aswellasalimitof0.01%(100mg/kg)asanunintentional contaminant,includingrecycledmaterials,abovewhichproductsarenot permittedfor sale(EU,2016). EPScan alsocontain other BFRslike tetrabromobisphenol A (TBBPA), as well as the POP substance decabromodiphenylether(BDE-209)(Ranietal.,2014).AnewerBFR additive thatis currently more commonin EPS is PolyFR (CAS No.
1195978-93-8),whichisacopolymerof polystyreneandbrominated polybutadiene.PolyFRisnotcurrentlyconsideredahazardoussubstance (Kochetal.,2019).
WiththeincreasedmotivationtorecycleEPS,thereisaconcernthat phased-outorrestrictedBFRsmaypersistinrecycledproducts,including thosetheywerenotintendedfor,likeEPSpackagingfoam.Packaging foamhasbeenfoundinsomecountriestocontainhighlevelsofHBCDD (Abdallah et al.,2018; Rani etal., 2014),potentially attributableto recycling practices. The presence of BFRs in recycled EPS materials
* Correspondingauthor.
E-mailaddress:[email protected](H.Knutsen).
http://doi.org/10.1016/j.hazl.2021.100016
Received21December2020;Receivedinrevisedform4February2021;Accepted5February2021 Availableonline10February2021
2666-9110/©2021TheAuthor(s).PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).
ContentslistsavailableatScienceDirect
Journal of Hazardous Materials Letters
j o urn a lh ome pa ge : w ww . e l se v i e r . com / l oca t e / ha z l
introducesnewexposureroutestohumans,suchasbydermalcontactto theEPSandproductspackedwithin(Abdallahetal.,2018),inadditionto environmentallitter(Turner,2020).
InNorway,approximately70000tonsEPSisimportedorproduced yearly,ofwhichabout50%isusedasfishboxes,whilemostoftherestis usedinthebuildingandconstructionindustryasisolationorfoundations.
Smalleramountsareusedastransportprotectionforelectronicproducts andfurniture(AvfallNorge,2020).ThecollectionofEPSfromfishboxes andotherpackagingin2019was5353tons(GPN,2020).
The EPS foam waste from municipal households in Norway is dominatedbywhitepackaging.Fordisposalofthiswaste,Norwegian citizensareinstructedtoplacesmallpiecesofEPSwasteintotheirnormal householdwaste(typicallyincineratedforenergy)(Arpetal.,2017), while largerpieces shouldbe deliveredtoamunicipalwastesorting facility(MWSF).TheseMWSFshaveadesignatedcontainerforwhiteEPS, andthesecontainersgiveinstructionstodisposecolouredEPSforeither incinerationor,inthecaseofEPSinsulationplates,ashazardouswaste (duetotheirlikelihoodofhavingBFRs).
Inthis studythepresence ofBFRs wasinvestigatedin whiteEPS collectedfromNorwegianMWSFs.Thepurposewastoseewhatlevelof chemical analysisis neededtoprevent HBCDDandotherBFRs from enteringapotentialrecyclingstreamforpackagingEPSabovetheLPCLs of0.01%and0.1%.Thepossibleoptionsinthisrespectwas1)noanalysis, onlyvisualsorting;2)simplebrominescreening(e.g.withportableX-ray fluorescence,XRF);3)advancedbrominescreening(e.g.XRFofdissolved EPS,followingSchlummeretal.(2015));and4)targetedBFRsubstance specificanalysis(e.g.gaschromatography-massspectrometry,GC-MS).
2. Materialandmethods
2.1. SamplingandMunicipalWasteSortingFacilities
EPSsamples(n=120)werecollectedbetweenFebruaryandMarch 2019atfourMWSFsfromdiverselocationsinNorway.Siteinformationis provided in Table 1. Arandomised, representative collection of EPS packagingfrom designatedsortingcontainers wascollected,andthe sampleswereplacedintransparentLDPEbags,transportedtoNGIand keptsealedatroomtemperatureuntilanalysis.
EPSsamplingwasdonetoreflectthevisualdiversityofsamplesinthe container,basedonshapes(e.g.fishboxes,packaging,irregular,plates), colour(shadesofwhite/miscolouration)anddegreeofweathering(see below). The diversity of packaging is considered to reflect recently disposedwaste,basedoncommunicationwiththeMWSFstaff,asthe containersaregenerallyfilledonthescaleofdaystoweeksdependingon thelocation.
2.2. Chemicals
Pureanalyticalgradeacetone(VWR,Darmstadt,Germany)andtechnical gradebromine (certifiedreferencematerial Br-,100030
m
g/l,Spectrapure StandardsAS(Oslo,Norway))wasusedtomakefourcalibrationstandardswithbromineconcentrationsrangingfrom0to1000mg/kg(0,10,100and 1000).
2.3. Samplepreparation
Priortoanalysis,allsampleswereweighedandphotographed.Colour, degradation/weatheringdegree(0=notdegraded;1=somedegrada- tion; 3=massive degradation, Fig.1) and,if possible,source, label, productionyearandcountryoforiginwasnoted.
2.4. XRFanalysisfordetectionofbromineinfoamsamples
AllEPSfoams(n=120)werecutintoapproximately1010x10cm piecesandanalysedforbrominecontentusingamounted,hand-heldXRF (X-rayfluorescencespectroscopy)apparatus(ThermoScientificNiton XL3t).EachsolidfoamsamplewasscannedwithXRFatthreelocations (60sec.perscan)ontheexteriorandalsoonthefreshlycutinterior.
2.5. GC-MSanalysis
Samples with detectable (n = 16) and a random selection of undetectable(n=20)brominelevels(basedonXRFanalysis)weresent totheaccreditedlaboratoryEurofinsEnvironmentTestingASforanalysis ofBFRs(HBCDD,Penta-BDE(commercialmixture),Octa-BDE(commer- cialmixture),Deca-BDE(BDE-209)andTBBPA;LOQ=10mg/kg),to verify whether bromine could be an indicator of the presence of prioritizedBFRs.Inbrief,the sampleswereextractedwith dichloro- methanewithaninternalstandardmixinanultrasonicbath.Theextracts werefurtheranalysedwithGC-MS(Agilent,column:15mDB-5(J&W), 0.25mmi.d.,0.1
m
mfilm)usingheliumascarriergaswithatemperature programmablecoldinjectionsystem(temperatureprogram:70C,2min.upto345Cfinaltemperature).
2.6. XRFanalysisfordetectionofbromineinacetoneextracts
Schlummeretal.(2015)publishedascreeningmethodforrapidfield identification of HBCDDcontaining EPS (and extruded polystyrene, XPS),andfurtherdifferentiationfromPolyFRcontainingEPS.Thetest principleisbasedonPolyFRnotbeingextractableinacetonewhereas HBCDD is, along with other acetone-soluble BFRs. XRF analysis of acetoneextractswasperformedforaselectionofsamples withhigh levelsofbromineinthesolidphase(n=3),basedonXRFanalysisof EPSsamples(section2.4)andsampleswithmeasurableHBCDDlevels (basedonGC-MSanalysis,n=1).FollowingSchlummeretal.(2015), 2gEPSfoamwasputina500mlglassbeakerand5gacetonewas addedandtheglassbeakerwasmanuallyswirleduntilcompletevisual dissolution.After5min,thesupernatantofabout3gofclearacetone extractwastransferredwithaglasspipetteintopolyethylenesample cuvettes, coveredwith mylarfilm, andplacedinthe XRFstandfor analysis.EachacetonesamplewasscannedwithXRFatthreelocations (60sec.perscan).
Table1
MunicipalWasteSortingFacilities(MWSF)sampledanddetailsfromtheexpandedpolystyrenefoam(EPS)samplingcampaign
MWSF Numberofsamples
(n)andsampleIDs
Location EPSwastecharacteristics EPSwasteamounts
Mile n=20
M-1toM-20
Drammenmunicipality.Centrally locatedintheeasternandmost populatedpartofNorway
MostlywhiteEPSpackagingfrom households(detachedhouses)
250-300kgisusuallyreceivedper month(3000-3600kgperyear)
Lyngås n=20
L-1toL-20
8000kgwhiteEPSwasreceivedin 2018
Haraldrud n=40
H-1toH-40
Oslocity.Norway'scapitaland mostpopulouscity.Locatedinthe easternpartofNorway
MostlywhiteEPSpackagingfrom households(apartmentbuildings)
Notprovided
FinnmarkRessurs n=40 F-1toF-40
Hammerfestmunicipality.Locat- edinthenorthern-andeastern- mostcountyinNorway.
MostlyEPSfishboxesandwhite EPSpackagingfromindustryand households
12106kgfishboxesperyear, and1600kgwhiteEPSpackaging
2.7. Qualitycontrolandqualityassurance
Thesolidfoamsampleswerescannedattheexposedsurfaceaswellas ontheinner,slicedpart,toverifyifbrominewasevenlydistributedinthe EPS(threescanspersurface).
Quantificationofbromineinthesolidfoamsamples(LOQof8mg bromine/kg) was carried out using the internal calibration of the instrument using three polyvinylchloride (PVC) standards (Thermo Scientific,Norway)withbrominelevelsof0,499and1099mg/kg.The curvewashighlylinear(r2=0.9996,Fig.S1).
Bromine levels in acetone extracts were calculated from the calibrationcurveobtainedfromthecalibrationstandardsof0,10,100 and1000mg/kg(Section2.2.).Thecurvewashighlylinear(r2=0.9999, Fig.S2).Thelimitofquantification(LOQ,calculatedaslowestcalibration standard)was10mg/kg.
DuringtheXRFmeasurements,asystemcheckwascarriedoutatthe startandendofeachday'smeasurementandatintervalsofeveryhour.
TheaccreditedlaboratoryEurofinsEnvironmentTestingASensured GC-MSquantificationoverspecificmasses(m/z)wereperformedagainst externalstandardcalibrationandcorrectedusingPCB209asaninternal standard,withanestimatedrelativeexpandedmeasurementuncertainty of14%.
3. Resultsanddiscussion 3.1. BrominelevelsinsolidEPSfoam
BrominewasdetectedbyXRFanalysisin16outof120EPSsamples (13%,Table2),rangingfrom9.4to4453mg/kg(meanSD:1500 1900;median:120,n=16).Sixofthesehadbrominelevels>1000mg/
kg(range:3413-4454).Theremainingsamplescontainingbromine(n= 10)rangedfrom8.1to660mg/kg(mean:120190;median:40).The differencebetweenthetwogroupswassignificant(p=0.00014,n= 120). There was no significant difference between bromine levels measuredontheexposedsurfacevs.theinterior(p=0.96;TableS2), which indicate that bromine was evenly distributedthroughout the samples.Therewerenosignificantdifferenceinbrominecontentbetween samples of different weathering degree (p = 0.50-0.99, n = 120).
However,mostsamplesdidnotshowanysignsofweathering(TableS1), asmostoftheEPSpackagingconsistedofwastedirectlyfromhouseholds.
ThehighestbrominecontentwasmeasuredinsampleM-13(4500 mg/kg),which looked like aninsulation plate,though wascoloured white,unlikemostsuchplatesinNorway(oftenblue).EPSinsulation materialsoftencontainBFRs(Harradetal.,2019;Sharkeyetal.,2018).
RelativelyhighbrominelevelswerealsofoundinsampleH-25(3500mg/
Fig.1.Exampleofdegradation/weatheringdegrees.
Table2
Concentrations(mg/kgdryweight)ofbrominatedflameretardantsHBCDDandTBBPAmeasuredwithGC-MS,aswellasbrominemeasuredwithXRFinEPS-samples fromMile(M),Lyngås(L),Haraldrud(H)andFinnmark(F).Penta-,octaanddeca-BDEswerenotquantifiableoverthemethodsLOQ(10mg/kg).LOQforHBCDDand TBBPA(GC-MS):10mg/kg.LOQforbromineinsolidEPSsamples(XRF)8mg/kg;LOQforbromineinacetoneextracts(XRF):10mg/kg.Onlysampleswithmeasurable bromineand/orBFRlevelsareshowninthetable().
Sample-ID HBCDD(GC-MS) TBBPA(GC-MS) Estimatedbrominecontent
basedontargetGC-MSa
Bromine(XRF)b AcetoneExtractable bromine(XRF)c
M-5 <LOQ <LOQ - 12 -
M-13 8900 <LOQ 6650 4500 700
L-2 <LOQ <LOQ - 9.4 -
L-7 <LOQ <LOQ - 640 -
H-4 <LOQ 14 8.2 3600 710
H-7 <LOQ <LOQ - 120 -
H-12 <LOQ <LOQ - 120 -
H-17 <LOQ <LOQ - 25 -
H-20 <LOQ <LOQ - 19 -
H-25 <LOQ <LOQ - 3600 -
H-35 <LOQ <LOQ - 86 -
H-36 <LOQ <LOQ - 4200 <LOQ
F-11 <LOQ <LOQ - 32 -
F-15 <LOQ <LOQ - 16 -
F-16 <LOQ 280 160 3500 -
F-38 <LOQ 200 120 3500 540
aBasedonmeasuredHBCDDorTBBPAconcentrationsmultipliedbypercentmassbromineof0.747and0.588respectively,forconversiontoequivalentbromine concentration(estimate).
b XRFanalysisonsolidEPSfoam;cXRFanalysisofacetoneextractablebromine.
kg),whichwasawhiteEPSsamplewithblackdots.Theblackdotsare likely due to manufacturing impurities of black EPS in white EPS (according to a personal communication with the Norwegian EPS producers society, EPS-foreningen). However, black dots do not necessarilyimplybromine,assampleM-7hadasimilarfrequency of black dots, but with no measurable bromine with the applied XRF method.HighbrominelevelswerealsofoundinwhiteEPSsamplesH-36 andH-4(4000and3600mg/kg,respectively),aswellasF-16andF38 (3500mg/kg),whichwerenotvisuallydistinguishablefromtheothers.
3.2. ComparisonofXRFandBFRanalysis
TheBFRanalysisbyGC-MSofthe16sampleswithbrominedetected byXRF and20diverse, representativesamples wherebrominecontent was<LOQarepresentedinTable2andTableS3.Innoneofthesamples wherebrominewas<LOQwasaBFRquantified(TableS3),meaningthere were no“falsenegatives”usingXRF.HBCDDwas detected above LOQinonly oneofthe16samples,andTBBPAaboveLOQinthreeofthe16samples.For thesefour samples, theGC-MS derivedbrominecontent wascalculatedbased onthisdata(Table2).Ingeneral,XRFgaveahigherbrominecontentthan whatwascalculatedbasedontargetedGC-MSresults,andsomeofthis discrepancymaybeduetoadditionalbrominatedcompoundsbeingpresent.
Inthisstudy,therewereeightsamplescontainingbrominebutnoneofthe targetPOP-BFRs;however,theselikelycontainotherflameretardantsnot measuredbytheGC-MSanalysisinthisstudy,includingPolyFRaswellas
"emergingBFRs"(Nyholmetal.,2013;Ranietal.,2014),possiblyalsoasa cocktailofnon-targetBFRsfromPS/EPSrecycling.
ThesamplewithHBCDDdetectedwasthesuspectedwhiteinsulation- plateM-13,withconcentrationsabovetheLPCLlimitforhazardouswaste (8900 mg HBCD/kg, Table 2). Harrad et al. (2019) presented that insulationplatesinparticulararedominatedbyHBCDD,andthathand- heldXRFdatagenerallycorrelatewellwithHBCDDforinsulationplates aswellasotherconstructionanddemolitionwaste.Thisalsohighlights theimportanceofseparatingsuchEPSwaste(i.e.insulationplates)from packagingwaste,forrecycling.ThethreesampleswithTBBPAwereH-4, F-16 andF-38. Allof these were whiteEPS samplesthat resembled packagingmaterialandcouldnotbevisuallydistinguishedfromother samples.
AsshowninTable2andFig.2,acetone-extractablebrominewas measuredovertheLOQ(10mg/kg)inthreeofthefoursamples,with
levelsrangingfrom540to710mg/kg.Theacetoneextractablebromine wasconsistentlylessthanthetotalbromine,indicatingtheextractionwas notquantitative.ForthesamplewithlargeamountsofHBCDD,M-13, only15%ofthebrominewastransferredtotheacetonefraction.Forthe three other EPS samples with high bromine content, bromine was transferredintotheacetonefractionoftwoofthesamples(H-4andF-38), butnotH-36(Fig.2).Thislattercasemaybeduetotheuseofbrominated polymersorotherproductsthatarenotacetoneextractable,forexample PolyFR (Schlummer et al., 2015). The former two cases are partly explainedbytracelevelsofTBBPAfromtheGC-MS,butnotquantitatively (Fig.2).Thisimpliesthepresenceofoneorseveralacetone-solubleBFRs thatwerenotanalysedforbyGC-MS,potentiallyTBBPAderivativeslike TBBPA-DPBE(Khaledetal.,2018),otherBFRs(Zhengetal.,2019),or possiblybreakdownproductsofPolyFR(Kochetal.,2016;Kochetal., 2019)andotherBFRs.
3.3. ComparisonwithLiterature
ThereweretwootherknownstudiesthatlookedatBFRcontentin EPSpackagingwaste,astudyfromtheUKandIreland(Abdallahetal., 2018)andaSouthKoreanstudy (Ranietal.,2014).IntheUK and Irelandstudy,27outof29EPSpackagingsamples,mostlyforfoodand electronicappliances, hadHBCDD levels abovea detectionlimit of
>0.0007mg/kg,withameanvalueandrangeof2025mg/kgand
0.16-91mg/kg,respectively.Thiscanbeconsideredlowcomparedto the100mg/kgLPCL.Thesamestudymeasuredsubstantiallyhigher concentrations of HBCDD inEPS packaging for lab equipment and constructionmaterials(mean:5261573mg/kg,range:0.036-5897 mg/kg,n=14),whichcrossedtheLPCLlimitinsomecases(Abdallah etal.,2018).IntheSouthKoreanstudy,twoEPSpackagingsamples wereanalysed;aniceboxforfoodpackagingandelectronicappliance packagingmaterial.ThesehadHBCDDlevelsof960and0.65mg/kg, respectively(Ranietal.,2014).Comparedtothisstudy'srelativelyhigh LOQofHBCDDof10mg/kg,therewere15outof29packagingsamples thatexceededthisintheUKandIrelandstudy,andoneoutoftwointhe SouthKoreanstudy.Bycomparison,onlyoneoutof120(or0.8%)had detectableHBCDDlevelsinthisstudy–thesuspectedinsulationplate.
Thiscouldindicatethatthe"whiteEPS"inNorwegiansortingfacilities maycontainmorevirginmaterial,orrecycledvirginmaterialwithless flameretardants.
Fig.2.BrominecontentinsamplesM-13,H-14,H-36andF-38(basedonbrominecontentmeasuredbyXRFinEPSfoamsamplesandEPSfoamextracts,andestimated brominelevelsbasedonmeasuredBFRcontent(GC-MSanalysis)).
4. RecyclingpotentialforNorwegian,whiteEPSpackagingwaste
Based on theXRFresults of thesolidEPS samples in thisstudy (n = 120), themedianconcentrationofbrominewas4mg/kg,whenhalfoftheLOQof 8mg/kgwasusedinthecalculationswhentheconcentrationswere<LOQ.
Thus,asaconservativeestimate,consideringthatin2019,5353tonsEPS wastepackagingwascollectedforrecyclinginNorway(seeabove),the amountofbrominebeingsentintorecyclingwouldbe21kgperyear,or 0.0004%theweightofrecycledEPS.Theseresultswouldfavourrecycling ofsortedwhiteEPSinNorway,asthisiswellbelowtheLPCLvalueforBFRs of0.1%(1000mg/kg)forrecyclingand0.01%(100mg/kg)abovewhich productsarenotpermittedforsale.Onlyonesampleoutof120hadHBCDD abovetheLPCLs,likelyduetoamissortedinsulationplatesample.There werethreesampleshavingTBBPA,withonlytwoexceeding0.01%,and nonehadmeasurablelevelsofPBDE.
Inthisstudyweaskedthequestionwhichlevelofoptionswouldbe neededtobebelowtheLPCL,withtheoptionsbeing1)noanalysis,only visual sorting;2)simpleXRFscreening; 3)advanced screeningusing acetonedissolvessubsamples;and4)targetedBFRsubstancespecific analysis.
ItappearsevidentthatinNorwaythecurrentvisualsortingsystem used,topreventcolouredEPS,insulationEPSorsmallEPSpieces,toenter thewhiteEPSpackagingwastestreamforrecycling,appearsaneffective strategy. This study did not include packaging peanuts, EPS from laboratorywareorEPSfromconstructionanddemolition(exceptforone wronglysortedinsulationplate),butbasedonresultsfrome.g.Abdallah etal.(2018),Drageetal.(2018)andHarradetal.(2019),werecommend thatthesebenotincludedforrecycling,unlessarecyclingtechniqueis usedthatremoveshazardoussubstancessuchasBFRs.Further,wedo recommend thatwhiteEPSthatresemble insulationplatesshould be measuredwithXRFatsortingfacilitiesindubiouscases,orsimplynot allowedtoberecycled.
IntegrationofEPSsortingwithXRFdoeshavesomepotentialtosort outmoreambiguousEPSsamplesorcomplexEPSwastestreams;which wouldbedesirabletoincreaserecyclingrates.Inthisandasimilarstudy byHarradetal.(2019),nofalsenegativeswereaccounted(brominenot found,buthazardousBFRsidentified).Also,Sharkeyetal.(2018)found thatXRFanalysisofEPSprovedreliableasa"pass/fail"screeningtoolfor LPCL compliance.Acting onpseudo-false positives(i.e.sampleswith measurable bromine, but no BFRs based on targeted analyses) by removingthemfromtherecyclingloopwouldonlycauseasmallportion of EPS to not be recycled, which would also be favourable from a precautionarypointofview.Therefore,XRFwouldbearecommended investmentforotherEPSstreamsthanpackagingwaste,particularlyfor thesortingoflargepiecesthatcouldcontainBFRs,inordertoincrease EPSrecyclingtargetswhileavoidingBFRcontamination.Itwouldalsobe recommendedinregionswherepackagingEPSisalreadyimpactedby unintendedBFRcontaminationthroughrecycling.
Theuseofadvancedbrominescreeningviaacetonedissolutionand targetedchemicalanalysisislikelynotpossibletobemadeatthelevelof individualEPSpiecesatMWSFsinacost-effectiveway.However,such techniquescouldplayanimportantroleforcharacterizingproduced, recycledEPS,along-sidetargetBFRandnon-targetanalysis.Analysisof acetone-solubleandnon-acetonesolubleBFRscouldhelptomonitorin whatformbromineisappearinginrecycledEPS.
5. Internationalrelevance
DataonEPSsortingpracticesinothercountriesisveryhardtocome by.Thus,infuturestudiesonEPSrecycling,orotherplasticrecycling, thecontextofsortinginfrastructureandcomplianceshouldbeacentral featurewheninvestigating howBFRsor otherhazardoussubstances enter the circular economy. An important way forward is that construction EPS shouldbe kept separated from packaging EPS for recycling, forseparationof BFRandnon-BFRwaste.However, more
investigationsareneededinothercountriestoensurethatBFRsfrom e.g.constructionEPS,donotenterthepackagingEPSwastestream.The Korean (Rani et al.,2014), UK andIreland (Abdallahet al., 2018) studies report higher concentrations of BFRs in packaging than observedhere,whichcouldhavebeenduetomixedsortingintothe recyclingstream.Basedonthesediscrepancies,theresultsinthisstudy forNorwaymaynotbeapplicabletoEPSsortingandrecyclingschemes inother countries.XRF screening ofvisually sorted EPS packaging wasteinothercountrieswouldbethemostrapidwaytocomparewith theNorwegiansituation.
Onaninternationallevel,andparticularlyinEurope,EPSrecyclingis increasing, as emphasised by a voluntary pledge submitted by the association"EuropeanManufacturersofEPS"(EUMEPS)onbehalfofits memberstoincreasetheirrecyclingtargetsby2025(EUMEPS,2018).
Thisisapositivetrend;howeveraspartofthispledge,itshouldbeensured thataslittleBFRsendupinrecycledEPSproductsaspossible.
DeclarationofCompetingInterest
Theauthorsdeclarethattheyhavenoknowncompetingfinancial interestsorpersonalrelationshipsthatcouldhaveappearedtoinfluence theworkreportedinthispaper.
Acknowledgementandfundingsources
Thisworkwasco-fundedbyNORSIRKandtheResearchCouncilof Norwaythroughinternalfunding(GBV)andtheprojectSLUDGEFFECT (302371/E10).
AppendixA.Supplementarydata
Supplementarymaterialrelatedtothisarticlecanbefound,inthe onlineversion,atdoi:https://doi.org/10.1016/j.hazl.2021.100016.
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