Ene gy Con e sion and Managemen 329 (2025) 119633
A ailable online 16 Feb ua y 2025
0196-8904/© 2025 Else ie L d. All igh s a e ese ed, including hose o ex and da a mining, AI aining, and simila echnologies.
Resea ch Pape
Recycling o plas ic- ich s eams om was e elec ical and elec onic
equipmen (WEEE) so ing plan s: An in-dep h s udy o py olysis po en ial
h ough p oduc cha ac e iza ion and li e cycle assessmen (LCA)
Bo ja B. Pe ez-Ma inez
a,*
, Alexande Lopez-U ionaba enechea
a
, Ad iana Se as-Malillos
a
,
Es he Acha
a
, Mi en Ma ínez-San os
a
, Blanca M. Caballe o
a
, Maide I u ondobei ia
b
,
Hugo A onso
b
a
Depa men o Chemical and En i onmen al Enginee ing, Bilbao School o Enginee ing, Uni e si y o he Basque Coun y (UPV/EHU), Plaza Ingenie o To es Que edo,
1, 48013 Bilbao, Spain
b
Depa men o G aphical Design and P ojec Enginee ing, Bilbao School o Enginee ing, Uni e si y o he Basque Coun y (UPV/EHU), Plaza Ingenie o To es Que edo,
1, 48013 Bilbao, Spain
ARTICLE INFO
Keywo ds:
WEEE
Py olysis
Plas ic was e
Seconda y aw ma e ials
Li e cycle assessmen
Py olysis oil
ABSTRACT
The mochemical ecycling is eme ging as a iable al e na i e o he ecycling o complex plas ic was e s eams,
such as hose o igina ed in was e elec ical and elec onic equipmen (WEEE) so ing acili ies. In his wo k, h ee
di e en WEEE plas ic- ich samples a e subjec ed o py olysis and he esul ing p oduc s a e ho oughly analyzed
o assess hei po en ial indus ial u iliza ion. The py olysis p ocesses a e conduc ed in a 3 L non-s i ed ank
eac o a a hea ing a e o 15 ◦C/min, eaching a inal empe a u e o 500 ◦C wi h a dwell ime o 30 min, using
1 L/min o N
2
as ca ie gas. The py olysis p oduc s a e cha ac e ized and e alua ed o hei po en ial appli-
ca ions, including pe ochemical eeds ock, e use de i ed uel (RDF), and solid adso ben . The esul s indica e
ha py olysis liquids can be used as RDF in cemen kilns, p o ided he halogen con en is below accep ance
limi s. The gases p oduced could be used as e ine y gases a e pollu an emo al. Addi ionally, he solid ac ion
cas s p omising esul s in p elimina y es s as a d ug adso ben in wa e , sugges ing a new and e y in e es ing
pa h o esea ch. Li e cycle assessmen (LCA) shows ha he py olysis o sample C, which has he wo s chemical
p ope ies, gi es he lowes en i onmen al impac , since he solid ac ion om his sample is he mos e ec i e
adso ben , achie ing almos 100 % emo al e iciency o he es ed d ugs. The indings sugges ha py olysis o
plas ic- ich s eams should no always be ocused on he oil p oduc ion, as i can yield o he aluable p oduc s.
1. In oduc ion
The amoun o elec ical and elec onic equipmen (EEE) placed on
he global ma ke is inc easing by almos 2.8 M pe yea [1]. The
consump ion o hese ma e ials is s ongly in luenced by he apid
de elopmen o some o he wo ld’s mos populous coun ies and he
esul ing inc ease in he g oss domes ic p oduc (GDP), bu also due o
he h ow-away philosophy su ounding hese p oduc s in he de eloped
coun ies [2]. Wi h an a e age li e ime o 4 o 10 yea s [3] and he
ela i ely low cos o some o he de ices, which makes hem easily
eplaceable, he amoun o was e om elec ical and elec onic equip-
men (WEEE) gene a ed ises o 62 M pe yea wo ldwide [1]. WEEE is
one o he mos complex was e s eams o manage and ecycle due o i s
ma e ial he e ogenei y and he p esence o haza dous subs ances. As a
consequence, in he Eu opean Union, i s collec ion, ea men and
ecycling is es ablished by a speci ic Di ec i e since 2012 (Di ec i e
2012/19/EU) [4]. Howe e , om he o al WEEE gene a ed in Eu ope in
he yea 2018, oughly he 50 % was collec ed o p ope ea men ,
losing he o he hal in o he was e lows as mixed esidual was e o
mixed me al sc ap [5]. This collec ion a e is s ill a away om he 85 %
ha he Eu opean Di ec i e es ablished o he yea 2019 [3].
The i s s ep o ecycle WEEE is he sepa a ion and so ing o i s
cons i u i e ma e ials h ough a mechanical ea men ha con ains
di e en s eps such as depollu ion, so ing, size educ ion, sepa a ion
and concen a ion in o use ul inal ac ions [6]. Haza dous subs ances
and componen s, o ins ance he e ige an s in “ empe a u e exchange
* Co esponding au ho .
E-mail add ess: [email p o ec ed] (B.B. Pe ez-Ma inez).
Con en s lis s a ailable a ScienceDi ec
Ene gy Con e sion and Managemen
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h ps://doi.o g/10.1016/j.enconman.2025.119633
Recei ed 2 Decembe 2024; Recei ed in e ised o m 4 Feb ua y 2025; Accep ed 9 Feb ua y 2025
Ene gy Con e sion and Managemen 329 (2025) 119633
2
equipmen ” o me cu y con aining ba e ies in “small equipmen ”, a e
sepa a ed be o ehand du ing depollu ion s ep o a oid he elease o
pollu an s o bo h he en i onmen and he subsequen so ing p ocess.
La ge me al and plas ic pa s, e.g. s eel, aluminum and plas ic cases, and
ames o he appliances, a e also eco e ed in his s ep. A e wa ds,
consecu i e size educ ion s eps a e ca ied ou o p og essi ely elease
he me allic ma e ials om he complex componen s o he appliances
and subsequen ly sepa a e hem by means o magne ic, eddy cu en and
induc ion sepa a o s. The p ocess a his poin is mainly ocused on
eco e ing s eel, aluminum and coppe ich ac ions, which make up
40 w % o WEEE [7]. A he same ime ha hese me als a e sepa a ed,
plas ics a e concen a ed, gene a ing plas ic- ich s eams ha also
con ain small pieces o me als ha a e no easy o sepa a e, such as hose
p esen in p in ed ci cui boa ds (PCB) and wi es, and o he unso ed
ma e ials such as ubbe s, glass o wood [8]. The main plas ics in hese
s eams a e: (1) S y ene-based plas ics, mainly ac yloni ile bu adiene
s y ene (ABS), bu adiene s y ene (SB), high impac polys y ene (HIPS)
o blends o ABS and polyca bona e (PC) om housings. (2) The mose
esins (mainly epoxy/phenolic esins) om elec onic boa ds. (3) O he
he moplas ics such as poly inyl chlo ide (PVC) om wi e jacke s,
polybu ylene e eph hala e (PBT) and polyp opylene (PP), among
o he s [9]. The he e ogenei y o hese s eams makes hem unsui able
o di ec mechanical ecycling and u he sepa a ion is also chal-
lenging due o he small pa icle size [10]. The e o e, hey a e usually
incine a ed o land illed.
Al e na i es o ecycling hese plas ic- ich complex s eams mus be
s udied ollowing a ci cula economy app oach, which is being p o-
mo ed by he Eu opean Union in he new Eu opean G een Deal s a egy,
in o de o eco e seconda y aw ma e ials ins ead o he cu en
disposal a land ill o ene gy eco e y ou es [11]. Howe e , he ecy-
cling o such a complica ed mix u e o ma e ials is a challenge in i sel .
In his sense, he mochemical ecycling is an al e na i e o o e come he
p oblem o he e ogenei y and incompa ibili y o plas ics in mechanical
ecycling. The mochemical p ocesses, such as gasi ica ion and py olysis,
ha e p o en hei e iciency in he ea men o complex plas ics
s eams, being capable o gene a ing a a ie y o aluable p oduc s. Due
o he in insic na u e o he gasi ica ion p ocess, i ocuses on he p o-
duc ion o aluable gases, mainly syngas (H
2
+CO), o he syn hesis o
chemicals. This p ocess has al eady p o en i s e iciency con e ing
was e plas ic in o gaseous s eams in which syngas (up o 50 ol%)
[12,13] o hyd ogen (up o 67 ol%) [14] we e he majo compounds.
Py olysis, on he o he hand, is a mo e lexible he mochemical ea -
men echnique, able o p oduce a wide ange o p oduc s wi h many
applica ions, no mally di ided in o 3 phases (solid, liquid and gas),
whose quan i y and quali y can be modi ied by adjus ing he ope a ing
condi ions. Fo ins ance, when conside ing py olysis o packaging
plas ic was e, he p ocess is no mally o ien ed owa ds he p oduc ion o
py olysis oils, he liquid ac ion, which ha e demons a ed g ea po-
en ial o use in oil e ining and pe ochemical indus y [15].
Con e sely, when conside ing he py olysis o polyme s wi h a mo e
complex s uc u e, e.g. he mose ing esins, gas p oduc ion is he
p e e ed op ion o e he p oduc ion o liquid hyd oca bons due o he
high complexi y o he la e [16]. In his espec , ecen in es iga ions
ca ied ou by he au ho s o his wo k on he decomposi ion o epoxy
and polyes e ma ixes o composi e ma e ials exhibi he possibili y o
achie ing gaseous s eams ich in syngas (o e 50 ol%) by py olysis
[17,18].
In he case o plas ic- ich s eams gene a ed in WEEE so ing plan s,
he py olysis p ocess usually ocuses on he py olysis oils. Howe e ,
hei indus ial u iliza ion is comple ely condi ioned by he pollu an s
hey may con ain, mainly halogens om PVC and plas ics con aining
b omina ed lame- e a dan s (BFR), and hea y me als. The concen a-
ion o bo h halogens and hea y me als is no mally limi ed and unde
su eillance in indus ial p ocesses due o he se e e consequences hey
can gene a e o p ocessing, he en i onmen and human heal h [19].
Howe e , his kind o in o ma ion is no no mally epo ed in li e a u e,
gene a ing he w ong belie ha py olysis oils om WEEE plas ic- ich
s eams could be di ec ly used in indus y. The e o e, i is necessa y o
conduc an exhaus i e and igo ous s udy on he possible con amina ion
o py olysis oils om WEEE plas ic- ich s eams and he in luence his
may ha e on hei po en ial applica ions.
The objec i e o his wo k is o s udy he py olysis o h ee di e en
plas ic- ich s eams ejec ed a di e en sepa a ion s eps o a WEEE
so ing plan . The samples will be deeply analyzed and subjec ed o
py olysis. Then, he p oduc s will be ho oughly cha ac e ized and hei
easibili y as al e na i e eeds ock o p oduc o he indus y will be
es ablished. A las , he en i onmen al pe o mance o he py olysis o
he h ee samples will be compa ed by means o li e cycle assessmen
(LCA) me hodology, based on he p e iously iden i ied applica ions o
each py olysis p oduc . This assessmen will help o es ima e which is
he ejec ed s eam wi h he bes possibili ies o be ea ed by py olysis
among hese gene a ed in common WEEE so ing plan s. The en i e
wo k as a whole ep esen s a signi ican no el y in he ield, since i
epo s he na u e o di e en plas ic- ich s eams gene a ed in WEEE
so ing plan s and he possibili ies ha hese s eams ha e o be alo-
ized h ough py olysis. The compa ison o he chemical p ope ies o
he p oduc s wi h he limi alues used in he indus y is e y igo ous,
esul ing in a ealis ic LCA analysis and a us wo hy snapsho o he
eal possibili ies o hese py olysis p oduc s.
2. Ma e ials and me hods
2.1. P epa a ion o WEEE samples
Th ee plas ic- ich samples (A, B, and C) om di e en p ocess lo-
ca ions o a WEEE so ing, sepa a ion and classi ica ion plan we e used
o he expe imen s. The appea ance o he samples can be seen in Fig. 1.
The o iginal A and B samples p esen ed mo e han 93 w % o pa icles
bigge han 10 mm. On he con a y, mo e han hal o sample C was
composed o pa icles smalle han 1 mm in diame e , since i came om
a milling s age downs eam o he poin whe e s eams A and B we e
gene a ed. The samples we e le o d y unde a mosphe ic condi ions
un il he equilib ium mois u e was eached. Subsequen ly, a qua e ing
p ocess was applied o ge ep esen a i e smalle samples o 100 g o
bo h ma e ial composi ion measu emen and py olysis es s. The o ig-
inal samples, excep o sample C, we e u he milled below 2 mm o
cha ac e iza ion analyses. These analyses included p oxima e analysis,
ul ima e analysis (C, H, N, S, O, Cl, B and me als), highe and lowe
hea ing alue (HHV and LHV) and he mog a ime ic analysis (TGA).
2.2. Py olysis expe imen s
Py olysis expe imen s we e ca ied ou in he labo a o y scale plan
shown in Fig. 2. I comp ises, as main elemen s: an uns i ed 3.0 L
s ainless s eel ank eac o ope a ing in semi-ba ch egime a a mo-
sphe ic p essu e; a wa e -cooled condensa ion sys em o gas–liquid
sepa a ion and liquid collec ion; an ac i a ed ca bon column o he
emo al o pollu an s and condensable compounds s ill p esen in he
gaseous s eam; and a 25 L Tedla plas ic bag o he collec ion o gases
o analysis.
Py olysis expe imen s we e designed in o de o maximize oil p o-
duc ion. When liquids a e he a ge , i is usual o wo k a he lowes
empe a u e a which comple e deg ada ion o he plas ic esidue is
gua an eed. I ha is no he case, lowe empe a u es (e.g. 400 ◦C) will
p oduce less liquid due o lack o decomposi ion [20] and highe em-
pe a u es (e.g. 600 ◦C) will s a o enhance c acking eac ions o p o-
duce gas o he de imen o he liquid ac ion [21]. As a as he o he
ope a ing pa ame e s a e conce ned, al hough hey may be mo e
dependen on he plan and eac o design, i can be said ha liquid
p oduc ion is a o ed by high hea ing a es and sho esidence imes in
he eac o . These a e, a leas , he conclusions d awn by he au ho s
a e se e al yea s o expe ience wo king wi h complex plas ic was e
B.B. Pe ez-Ma inez e al.
Ene gy Con e sion and Managemen 329 (2025) 119633
3
[21–25]. Consequen ly, he ope a ing condi ions o he py olysis es s
pe o med in his wo k we e 100 g o sample, 15 ◦C/min hea ing a e,
500 ◦C inal empe a u e, 30 min e en ion ime. A pu e ni ogen low o
1.0 L/min is in oduced om he bo om o he eac o and passes
h ough a pie ced dis ibu ion pla e be o e con ac ing he sample and
he es o he eac o in i s way o he ou le , lushing he apo s
gene a ed du ing he p ocess. The empe a u e is con olled by a he -
mocouple placed in he cen e o he eac o , close o he sample. Py-
olysis liquid and solid yields we e calcula ed by he weigh di e ence in
he pipelines, condense s and eac o be o e and a e he py olysis, and
we e exp essed as w .%. The gas yield was calcula ed by di e ence o
100.
2.3. Analy ical echniques
2.3.1. Was e samples cha ac e iza ion
The de e mina ion o he composi ion o he was e samples was
made as ollows. A ep esen a i e sample o 100 g was sepa a ed om
he es ollowing he coning and qua e ing me hod. Then, each piece o
hese 100 g was aken by hand and he na u e o he ma e ial was
de e mined based on he au ho ’s expe ience. In case o doub (mainly
wi h some plas ics), he piece (only ha piece) was in oduced in a
KUSTA 4004 M mul iplexed NIR spec ome e o de e mine i s na u e.
Once all he pieces we e iden i ied, hey we e sepa a ed in o amilies
and weigh ed. The he mog a ime ic p o iles o he plas ic- ich sam-
ples we e ob ained on a Me le -Toledo TGA/SDTA851 he mobalance
by means o dynamic analysis om 30 o 900 ◦C unde a hea ing a e o
10 ◦C/min in a 50 mL/min ni ogen a mosphe e. P oxima e analysis was
pe o med on a LECO TGA-701 he mobalance ollowing he EN-ISO
21660–3:2021 s anda d o mois u e, he EN-ISO 22167:2022 s an-
da d o ola ile ma e and he EN-ISO 21656:2021 o ash de e mi-
na ion. The highe hea ing alue (HHV) de e mina ion was conduc ed in
a LECO AC-500 au oma ic calo ime e ollowing he EN-ISO
21645:2022 s anda d. Then, lowe hea ing alue (LHV) was calcula ed
based on he HHV and he hyd ogen con en . Fo he de e mina ion o
ca bon, hyd ogen, ni ogen, and sul u con en a LECO T uSpec CHNS
au oma ic analyze was used acco ding o he s eps dic a ed by he EN-
ISO 21663:2021 s anda d, while oxygen was analyzed in a Eu o ec o
Eu o EA elemen al analyze . The chlo ine and b omine con en s we e
quan i ied ollowing he UNE-EN 15408:2011 s anda d, which consis s
in he combus ion o he sample in an au oma ic calo ime e , he same
one used o he HHV de e mina ion. The p oduced gaseous halides
we e adso bed in a basic solu ion o hei la e analysis by ion ch o-
ma og aphy (Dionex ICS 3000). The con en o me als was de e mined
ia XRF analysis on an ED-XRF Rigaku NEX QC +Quan EZ Analyze by
means o s anda d-less semi-quan i a i e Fundamen al Pa ame e s (FP)
Fig. 1. Appea ance o he as ecei ed WEEE samples.
Fig. 2. Schema ic ep esen a ion o he labo a o y scale py olysis plan .
B.B. Pe ez-Ma inez e al.
Ene gy Con e sion and Managemen 329 (2025) 119633
4
me hod.
2.3.2. Oils cha ac e iza ion
The elemen al composi ion and HHV o he py olysis liquids we e
de e mined using he same echniques and p ocedu es as hose
explained o aw samples. The main componen s in he oils we e
measu ed by gas ch oma og aphy (GC) AGILENT 6890 using a J&W DB-
FFAP capilla y column (60 m ×0.320 mm ×0.25 µm), coupled o a mass
spec oscopy de ec o (MS) AGILENT 5973, employing a ch oma o-
g aphic me hod de eloped by he au ho s and epo ed and discussed in
a p e ious wo k. To his ega d, i mus be aken in o accoun ha
GC–MS echnique is able o “see” only he 90 w % app oxima ely o he
o al oil when analyzing his kind o py olysis oils [26]. Besides, he
esul s in his a icle a e gi en in peak a ea pe cen age, i.e., wi hou
calib a ion. The e o e, hey canno di ec ly ex apola e in o w .% e-
sul s, because his can lead o e o s in he ange 50–200 % o he
subs ances ypically ound in hese oils [26]. A las , hose chemicals
p esen ing a spec a quali y ma ch wi h NIST08 spec a lib a y lowe
han 85 we e classi ied as “no iden i ied”. The oils de i ed om sample
A we e u he analyzed o de e mine he p esence o hea y me als (Ni,
Pb, Cd, C , As, Cu, Co, Tl, Sb, Sn, Hg, Mn, Zn) and he con en o poly-
chlo ina ed biphenyls (PCBs 18, 20, 28, 31, 44, 52, 101, 105, 118, 138,
149, 153, 170, 180, 194, 209). Acid diges ion ollowed by induc i ely
coupled plasma a omic emission spec oscopy (ICP-AES) was used o
me als de e mina ion. PCBs we e de e mined by GC–MS, acco ding o a
me hod based on he EN 12766 s anda d.
2.3.3. Gases cha ac e iza ion
The composi ion o he gases was measu ed by an Agilen 7890 se ies
gas ch oma og aph (GC), coupled wi h a he mal conduc i i y de ec o
(TCD) and a lame ioniza ion de ec o (FID). Column se up was
composed o a i s column, Agilen HP-Plo Q (30 m x 320 µm x 20 µm),
o he sepa a ion o he main hyd oca bons and a second column,
Agilen HP-PLOT Molesie e (30 m x 530 µm x 25 µm), place in se ies o
he sepa a ion o he pe manen gases; he low be ween he columns
was con olled by an elec onic al e. The quan i a i e cha ac e iza ion
o he gases was pe o med by calib a ing he main compounds usually
ound in his ype o gaseous s eam using a s anda d gas mix u e. The
composi ion o he s anda d was: CO
2
15 ol%, H
2
S 5 ol%, H
2
20 ol%,
CO 20 ol%, CH
4
20 ol%, C
2
H
4
5 ol%, C
2
H
6
5 ol%, C
3
H
6
5 ol%, C
3
H
8
3 ol%, 1-Bu ene 1 ol%, and 1-Pen ene 1 ol%. Bo h HHV and LHV o
he p oduced gases we e heo e ically calcula ed based on he com-
bus ion en halpy o each compound [27], by a ibu ing o each com-
pound pe cen age i s own HHV o LHV.
2.3.4. Solids cha ac e iza ion and adso p ion es s
Ul ima e and p oxima e analysis o py olysis solids we e de e mined
by he same means as he ones explained in sec ion 2.3.1. o he o iginal
was e samples. The measu emen o su ace a ea and po e olume was
ca ied ou by adso p ion iso he ms o CO
2
a 0 ◦C in a Mic o ac
BESORP-max II BEL, which is he s anda d p ocedu e o he measu e-
men o coal and coal like su aces when small and na ow mic opo es o
ul amic opo es a e expec ed [28]. Fo he adso p ion es s, six ypes o
penicillin d ugs (β-lac am an ibio ics) we e selec ed as main ep esen-
a i es o he mos common d ugs ound in was ewa e . Thei
desc ip ion and he gi en codi ica ion a e shown in Table 1.
S ock solu ions o he six penicillin ypes (AMOX, AMPI, CARB,
CLOX, PEN-G and PEN-V) we e dilu ed wi h high-pe o mance liquid
ch oma og aphy (HPLC) g ade wa e (Scha lau, Spain) and mixed in a
single solu ion con aining 1200 µg/mL o each pha maceu ical com-
pound. The adso p ion expe imen s we e ca ied ou in iplica e and in
ba ch mode in 50 mL polyp opylene Falcon ubes, con aining 0.5 g o
py olysis solid and 10 mL o he abo emen ioned penicillin solu ion.
This high adso ben loading was selec ed unde he assump ion ha he
solids maybe we e no good adso ben s. All Falcon ubes we e co e ed
wi h aluminum oil o a oid pho odeg ada ion. Then, all samples we e
s i ed a 150 pm on an o bi al shake unde ambien labo a o y con-
di ions (~20 ◦C) du ing 1 h. The con ol sample was also spiked wi h he
an ibio ic solu ion, bu wi hou adding any py olysis solid. This con ol
was included o in es iga e he na u al deg ada ion and possible
con amina ion o an ibio ics. A e he expe imen s, he collec ed sam-
ples we e il e ed (wi h 0.22 µm polyp opylene il e s) and analyzed by
HPLC-MS/MS ch oma og aph (Agilen 1290 In ini y II) coupled o a
iple quad upole mass de ec o (Agilen Technologies 6430 T iple
Quad). The an ibio ics emo al e iciency was calcula ed using Eq. (1),
whe e C
0
and C
a e he concen a ions o an ibio ics (µg/mL) in he
con ol sample and in each sample a he end o he expe imen ,
espec i ely.
Remo ale iciency(%) = C0−C
C0
(1)
2.4. Li e cycle assessmen (LCA)
The LCA me hodology was ca ied ou ollowing he ISO 14040
s anda ds. The main goal o he LCA was o assess he en i onmen al
impac s o he py olysis p ocess applied o each o he plas ic- ich WEEE
samples. The unc ional uni (FU) selec ed o he analysis, 1 o WEEE
plas ics, was se based on he amoun o di e en WEEE plas ic ac ions
ha a con en ional sized WEEE ea men plan would p oduce pe
hou . The in en o y o he LCA is shown in Table 2, which includes he
inpu s and ou pu s o he py olysis p ocess in each case. Excep o he
ea ed sample, he ma e ial and ene gy inpu s in he h ee cases we e
he same, as he e was no a ia ion in he py olysis p ocess i sel . These
we e: (1) ni ogen used as ine and ca ie gas, (2) ene gy necessa y o
hea an indus ial py olysis eac o using na u al gas as uel, (3) ac i-
a ed ca bon used o gas cleaning and (4) wa e used o cooling he
condense s. The quan i ies employed o he LCA analysis we e di ec ly
measu ed om he labo a o y expe imen s. The ni ogen inpu was
conside ed liquid ni ogen o a oid he ze o impac ha he so wa e
a ibu es o he low “ni ogen gas”. The selec ion o he ou pu lows
will be explained in “Resul s and discussion” sec ion, since i was done
aking in o accoun he chemical p ope ies o he p oduc s.
En i onmen al impac s we e calcula ed by using OpenLCA so wa e
coupled wi h he Ecoin en 3.9 da abase. The ReCiPe 2016 Midpoin
(H) me hod was used o ca ego ize he esul s in o eigh een en i on-
men al impac indica o s [29]. The wide ange o en i onmen al im-
pac s calcula ed wi h he selec ed me hod enables a deepe insigh o he
p ocess analysis and makes easie he compa ison wi h esul s om
o he esea ch wo ks a ailable in he li e a u e.
3. Resul s and discussion
3.1. Cha ac e iza ion o he o iginal was e samples
The ma e ial composi ion o he was e samples is p esen ed in
Table 3. Samples A and B showed a p edominan s y enic na u e (PS,
HIPS and ABS), along wi h a high con en o polyole ins (PP and PE) and
o he he moplas ics. This is well in acco dance wi h he composi ions
epo ed in o he s udies de eloped wi h simila was e s eams, whe e
s y enic plas ics we e p esen in he g ea es pe cen age and polyole ins
Table 1
Desc ip ion o he six di e en penicillin d ugs used in he adso p ion es s.
Penicillin ype Codi ica ion Pu i y (%) O igin
Amoxicillin AMOX 99 Sigma-Ald ich
Ampicillin AMPI 95 Sigma-Ald ich
Ca benicillin CARB 99 Sigma-Ald ich
Cloxacillin CLOX 99 Sigma-Ald ich
Penicillin G PEN-G 99 USP
Penicillin V PEN-V 89.9 USP
B.B. Pe ez-Ma inez e al.
Ene gy Con e sion and Managemen 329 (2025) 119633
5
we e also ound in signi ican quan i ies [30,31]. The composi ion o C
sample, on he con a y, p esen ed a la ge amoun o ines, which did
no allow a comple e de e mina ion o i s composi ion. In any case, he
ma e ials ha could be iden i ied in C sample showed a much smalle
amoun o s y enic plas ics, polyole ins and o he he moplas ics, being
PVC he mos abundan ma e ial. As i can be seen, he e a e clea di -
e ences in composi ion (and also pa icle size) among he plas ic ich
ac ions ha a e gene a ed in a WEEE ea men plan . This is an issue
ha mus be highligh ed and aken in o conside a ion when i comes o
p ojec a py olysis plan o ea “WEEE plas ics” wi hou u he spec-
i ica ion. I is common o hink ha hose WEEE plas ics will ha e a
composi ion simila o ha o sample A because his is he ypical
composi ion epo ed in li e a u e. Howe e , his could lead o unde-
si able su p ises in he exploi a ion pe iod o he plan .
Table 4 shows he ul ima e analysis, he p oxima e analysis and he
HHV o he h ee was e samples. The esul s o he ul ima e analysis
we e qui e simila o A and B samples, being bo h ich in ca bon. The
main di e ence be ween hem was he chlo ine con en , which was
highe in sample B due o he highe quan i y o PVC p esen in his
Table 2
In en o y used o pe o m he LCA.
Sample Inpu /
ou pu
Flow Amoun Uni A oided
was e
P o ide
A I WEEE plas ics-A 1
ni ogen, liquid 0.75 ma ke o ni ogen, liquid | ni ogen, liquid | Cu o , U −RER
ene gy, indus ial le el
na u al gas
1965 MJ na u al gas, bu ned in gas u bine | na u al gas, bu ned in gas u bine | Cu o , U
ac i a ed ca bon,
g anula
0.2 ac i a ed ca bon p oduc ion, g anula om ha d coal | ac i a ed ca bon, g anula |
Cu o , U −RoW
ap wa e 20 ap wa e p oduc ion, con en ional ea men | ap wa e | Cu o , U −RoW
O biogas 92 m
3
TRUE anae obic diges ion o manu e | biogas | Cu o , U −RoW
haza dous was e, o
incine a ion
0.209 ea men o haza dous was e, haza dous was e incine a ion, wi h ene gy eco e y |
haza dous was e, o incine a ion | Cu o , U −RoW
was e mine al oil 0.686 clinke p oduc ion | was e mine al oil | Cu o , U −Eu ope wi hou Swi ze land
B I WEEE plas ics-B 1
ni ogen, liquid 0.75 ma ke o ni ogen, liquid | ni ogen, liquid | Cu o , U −RER
ene gy, indus ial le el
na u al gas
1965 MJ na u al gas, bu ned in gas u bine | na u al gas, bu ned in gas u bine | Cu o , U
ac i a ed ca bon,
g anula
0.2 ac i a ed ca bon p oduc ion, g anula om ha d coal | ac i a ed ca bon, g anula |
Cu o , U −RoW
ap wa e 20 ap wa e p oduc ion, con en ional ea men | ap wa e | Cu o , U −RoW
O e ine y gas 0.131 TRUE e ine y gas p oduc ion, pe oleum e ine y ope a ion | e ine y gas | Cu o , U −RoW
haza dous was e, o
incine a ion
0,27 ea men o haza dous was e, haza dous was e incine a ion, wi h ene gy eco e y |
haza dous was e, o incine a ion | Cu o , U −RoW
was e mine al oil 0.599 ea men o was e mine al oil, haza dous was e incine a ion, wi h ene gy eco e y |
was e mine al oil | Cu o , U −RoW
C I WEEE plas ics-C 1
ni ogen, liquid 0.75 ma ke o ni ogen, liquid | ni ogen, liquid | Cu o , U −RER
ene gy, indus ial le el
na u al gas
1965 MJ na u al gas, bu ned in gas u bine | na u al gas, bu ned in gas u bine | Cu o , U
ac i a ed ca bon,
g anula
0.2 ac i a ed ca bon p oduc ion, g anula om ha d coal | ac i a ed ca bon, g anula |
Cu o , U −RoW
ap wa e 20 ap wa e p oduc ion, con en ional ea men | ap wa e | Cu o , U −RoW
O ac i a ed silica 0,525 TRUE ac i a ed silica p oduc ion | ac i a ed silica | Cu o , U −GLO
was e mine al oil 0.36 ea men o was e mine al oil, haza dous was e incine a ion, wi h ene gy eco e y |
was e mine al oil | Cu o , U −RoW
e ine y gas 0.115 TRUE e ine y gas p oduc ion, pe oleum e ine y ope a ion | e ine y gas | Cu o , U −RoW
Table 3
Ma e ial composi ion o he was e samples (w .%, n =1).
Polyole ins S y enic plas ics PVC PVC +me al O he he moplas ics Rubbe s Foams PCB
A 13.2 45.0 1.7 2.0 23.2 1.6 0.1 2.7
B 13.4 43.6 11.8 1.0 24.8 3.8 0.1 0.0
C 7.2 7.0 16.5 0.8 15.7 5.4 0.1 3.9
Tex ile Pape / Ca dboa d Magne ic me als Non-magne ic me als Pe ous Mul ima e ial Fines
(Ø <1 mm)
O he s
A 0.3 0.1 0.0 3.2 0.1 1.5 2.5 2.9
B 0.0 0.2 0.0 0.3 0.0 0.4 0.0 0.5
C 0.0 0.3 0.0 0.6 0.3 1.0 36.0 5.2
Table 4
Ul ima e and p oxima e analysis o samples and high hea ing alue (HHV).
Elemen al o ganic analysis (w .%, as ecei ed basis, mean alue ± STD, n ¼3)
C H N O S Cl B
(ppm)
O he s
1
A 65.4
±2.4
6.8
±0.3
1.9
±0.2
8.1 ±
2.6
0.2
±0.1
0.8
±0.1
369 ±
37
4.9
B 63.3
±2.8
7.5
±0.3
2.6
±0.4
4.8 ±
1.4
0.1
±0.1
3.2
±0.3
592 ±
59
4.9
C 43.4
±3.2
6.2
±0.4
1.4
±0.2
16.0
±2.1
0.4
±0.1
2.6
±0.3
211 ±
36
−-
P oxima e analysis (w .%, as ecei ed basis, mean alue ± STD, n ¼3) and HHV
(MJ/kg, as ecei ed basis, mean alue ± STD, n ¼3)
Mois u e Vola ile Ma e Ash Fixed Ca bon
1
HHV (MJ/kg)
A 0.4 ±0.1 83.3 ±1.5 11.9 ±1.4 4.5 ±0.4 30.2 ±0.3
B 0.9 ±0.1 79.8 ±0.5 13.5 ±0.5 5.9 ±0.3 29.1 ±0.6
C 0.8 ±0.1 53.0 ±5.4 40.8 ±5.7 5.4 ±0.4 15.0 ±1.0
1
by di e ence.
B.B. Pe ez-Ma inez e al.
Ene gy Con e sion and Managemen 329 (2025) 119633
6
sample. When compa ed o simila was e s eams s udied in o he
wo ks, he majo elemen s (C, H and N) p esen in bo h A and B samples
we e wi hin he epo ed anges, while hei oxygen concen a ion ell in
in e media e alues [32,33]. C sample showed a e y di e en na u e,
p esen ing lowe ca bon con en and a e y high quan i y o oxygen.
This elemen al composi ion is simila o ha o p in ed ci cui boa ds
(PCB), whe e oxygen become mo e p esen due o he o mula ion o
hei cons i u i e esins, hus lowe ing he ca bon plus hyd ogen con-
cen a ion [34,35]. The e o e, i could be hough ha PCB concen a-
ion in his C sample was g ea e han ha obse ed in he composi ional
analysis. In his sense, PCB could be hidden in he “ ines” ac ion due o
hei b i leness, which make hem mo e p one o yield small pa icles
when a c ushing o educing s ep is applied.
Wi h espec o he pollu an s ound in he h ee samples (S, Cl and
B ), chlo ine o bo h B and C samples appea ed in a g ea e concen-
a ion, while i s concen a ion in sample A was below hose alues. This
is in acco dance wi h he PVC con en o sample A, which was signi i-
can ly lowe han in samples B and C. Howe e , he highes chlo ine
con en was epo ed o sample B, while he highes PVC con en was
ound in sample C. This could be explained by he ac ha he chlo ine
con en o PVC plas ics can be e y di e en depending on he speci ic
o mula ion o he PVC in ques ion, since he p opo ion o addi i es in
some comme cial PVCs has been epo ed o be as high as 80 w % [36].
Thus, i is possible ha i sample C came om he sinking ac ion o a
loa -sink p ocess in he WEEE so ing plan , he PVC i con ained would
ha e a lowe chlo ine con en , as i is known ha he highe he amoun
o addi i es, he lowe he lo a ion o PVC [37]. B omine, on he o he
hand, appea ed in concen a ions wo o de s o magni ude lowe han
he alues desc ibed in o he wo ks [9,32]. The eason o inding hese
small quan i ies o b omine in he samples is ha he egula ion on
pe sis en o ganic pollu an s (POP) implies ha plas ics wi h a o al
b omine concen a ion highe han 2 w % mus be sepa a ed in WEEE
so ing plan s and sen o elimina ion, because some b omina ed lame
e a dan s (BFR) a e classi ied as POP and he 2 w % o o al b omine
s a is ically ensu es ha he concen a ion o hese egula ed BFR will be
below he h eshold concen a ion [38]. Consequen ly, he plas ic- ich
s eams gene a ed a e his sepa a ion s ep ha e low b omine con-
en s, al hough i s p esence can s ill be a ibu ed o plas ics wi h BFR in
low concen a ions. Finally, sul u in he samples appea ed a low
alues, cas ing a sligh ly g ea e concen a ion ha he ones ound in
o he epo ed wo ks dealing wi h WEEE s eams, and maybe ela ed o
some polyme iza ion ini ia o s such as sodium pe sulpha e [32,33].
The p oxima e analysis and HHV a e also shown in Table 4, whe e a
high o ganic ma e con en ( ola iles + ixed ca bon) is epo ed o
samples A and B, abo e 85 w % in bo h cases. These samples also
showed e y low mois u e con en (bellow 1 w %) and he ypical ash
con en alues o plas ic- ich ejec s o WEEE so ing plan s, a ound he
10 w % [32,39]. This is in ag eemen wi h he ma e ial composi ion,
whe e a main polyme ic na u e was obse ed o bo h samples. The high
con en o ola ile ma e made hese samples especially in e es ing o
he p oduc ion o py olysis oils and gases. C sample, o he wise, con-
ained a signi ican quan i y o ash (40.8 w %), p obably ela ed o such
a high con en o ines, which caused he ola ile ma e con en o
dec ease conside ably. A and B samples showed accep able HHV ha
would a p io i allow hem o be used di ec ly as uels, wi h alues close
o hose o bi uminous coals [40]. This was no he case o sample C,
whose HHV was highly condi ioned by i s con en o ash and oxygen,
and consequen ly p o iding a HHV ha was hal ha o he o he wo
samples.
Table 5 shows he con en o me als o he h ee samples. In gene al
e ms, i can be no ed ha he me al con en o sample C was highe han
ha o samples A and B. This esul is in di ec ag eemen wi h i s highe
ash con en and indi ec ly wi h he la ge amoun o ines in his sample,
which a i s sigh appea ed o be me allic powde . Howe e , i is
impo an o emembe ha his analysis was semi-quan i a i e, based
on undamen al pa ame e s and wi hou he use o s anda ds, so he
alues in he able do no ha e he accu acy o a quan i a i e analysis.
The me als ound in he highes p opo ion in all samples we e
aluminum, silicon, coppe , calcium and i anium. The i s h ee a e
majo me als in he composi ion o EEE, so i is logical o some ex en
ha hey we e de ec ed mixed wi h he plas ic ma e ials o hese de-
ices. Calcium and i anium, on he o he hand, a e pa o addi i es ha
a e widely used in plas ic o mula ions, such as calcium ca bona e,
calcium sul a e and i anium dioxide, and can be p esen in concen a-
ions close o 50 % o he o al weigh o he plas ic [41]. I is wo h
men ioning ha he amoun o calcium p esen in sample C, signi ican ly
highe han ha o sample B, could co obo a e he hypo hesis ha he
PVC p esen in sample C was much mo e addi i a ed han ha o sample
B, since calcium is a e y common elemen among PVC addi i es [42].
I on, also a majo me al in he composi ion o EEE, was p esen in lowe
concen a ions, co esponding o aces ha can s ill be ound mixed
along he disca ded s eams despi e ha ing an e ec i e sepa a ion s ep
in WEEE so ing plan s. O he me als ypical o plas ics addi i es such as
phospho us, an imony, ba ium, lead o zinc we e also ound, ha ing
hei o igin in he composi ion o lame- e a dan s, he mal s abilize s,
pigmen s o lub ican s [43]. Finally, i is wo h no ing he low con-
cen a ion o me cu y and he absence o cadmium in he samples, as a
consequence o he p og essi e p ohibi ion o he use o hese wo
subs ances in household applica ions.
The he mal decomposi ion pa e n o he h ee samples, shown in
Fig. 3, e eals wo main deg ada ion phases. The i s one occu s be-
ween 250 ◦C and 350 ◦C, while he second spans om 350 ◦C o 510 ◦C.
The ma e ials commonly p esen in polyme ic was e s eams ha can
unde go decomposi ion s eps a ound 250 ◦C a e wood, polyu e hane
(PU) and PVC. In he case o wood, his is a ibu ed o he decompo-
si ion o hemicellulose [44]; in he case o PVC, acco ding o he li e -
a u e, i co esponds mainly o he elease o chlo ine, de i ed om he
clea age o C-Cl bonds [45,46]; a las , PU i sel decomposes a em-
pe a u es a ound 300 ◦C [47]. Addi ionally, some lame e a dan s
usually ound in polyca bona es (PC) such as ammonium polyphospha e
can also he mally decompose a 300 ◦C [48]. In he case in ques ion, in
iew o he composi ion o he samples in Table 3, i could be said ha
he main con ibu o o he i s majo he mal decomposi ion phe-
nomenon is PVC. Howe e , sample C showed a highe decomposi ion
peak han sample B, when he la e con ained mo e chlo ine acco ding
o Table 4. The eason may be ha sample C con ained mo e addi i a ed
Table 5
XRF analysis o samples (ppm, as ecei ed basis, mean alue ±STD, n =3).
Elemen Sample
A B C
Al 7050 ±3521 6950 ±2369 15200 ±1374
Si 8250 ±2645 6700 ±801 52800 ±9354
P 1780 ±47 767 ±201 n.d.
1
K 344 ±0 n.d.
1
1720 ±482
Ca 6770 ±1398 7740 ±1601 25000 ±1739
Ti 3000 ±388 4140 ±281 3170 ±1646
C 124 ±113 19 ±8 106 ±68
Mn 18 ±2 22 ±2 135 ±22
Fe 666 ±23 781 ±33 2090 ±535
Co 80 ±58 n.d.
1
10 ±5
Ni 15 ±13 24 ±0 n.d.
1
Cu 3460 ±527 2090 ±894 5900 ±361
Zn 329 ±57 275 ±38 1040 ±55
S 56 ±24 39 ±5 495 ±205
Z 6 ±2 6 ±2 151 ±53
Cd n.d.
1
n.d.
1
n.d.
1
Sn 141 ±53 87 ±25 137 ±18
Sb 1210 ±49 1650 ±251 920 ±258
Ba 463 ±136 320 ±75 3840 ±474
Hg 2 ±1 2 ±1 7 ±1
Pb 130 ±4 420 ±126 1260 ±199
To al me al concen a ion ≈34000 ≈32000 ≈114000
1
No de ec ed.
B.B. Pe ez-Ma inez e al.
Ene gy Con e sion and Managemen 329 (2025) 119633
7
PC han sample B wi hin he ‘o he he moplas ics’ o i could e en
con ain PU and/o wood wi hin he ‘o he s’, he pe cen age o which is
highe han ha o sample B. Ano he explana ion could be he lack o
ep esen a i eness o he samples used o he analysis. This is a e y
ypical p oblem when wo king wi h such he e ogeneous g anula was e,
due o i s undamen al a iabili y ha is enhanced in he de e mina ion
o pa ame e s ha a e no p esen in all he pa icles ha o m he was e,
as is he case o halogens in WEEE plas ics. This issue has been add essed
by he au ho s in a ecen ly published wo k [49].
The second deg ada ion s ep co esponds o he elease o hyd o-
ca bons p oduced by he c acking o plas ics ia he b eakdown o C–C
and C–H bonds, a phenomenon widely epo ed in he he mal deg a-
da ion s udies conce ning plas ic- ich was e s eams [50]. O he less
ele an decomposi ion phenomena can be obse ed in he ange o
650–850 ◦C, which could be ela ed o he decomposi ion o ca bona es
and sul a es in he samples [51]. In any case, i can be seen in he igu e
ha 500 ◦C is a empe a u e high enough o achie e he quan i a i e
decomposi ion o he ola ile ma e in he h ee samples.
3.2. Py olysis yields
The yields ob ained in he py olysis o samples A, B and C a e p e-
sen ed in Table 6. The da a o he py olysis yields include he mean
alue o a leas wo equi alen expe imen s ha did no di e mo e
han 3 poin s in w .% om one o ano he . In he case o he solid
ac ion, he me allic pa s clea ly isible o he naked eye we e sepa-
a ed om he ca bonaceous solid in samples A and B in o de o analyze
he cha wi hou in e e ence om hese me allic pa s, which cons i-
u ed he 26.6 and 10.8 w % o he solid ac ion o A and B espec i ely.
This was no possible wi h sample C, due o i s small pa icle size.
Table 6 shows ha he liquid p oduc was he main ac ion o samples A
and B, anging a ound 70 w % and 60 w %, espec i ely. The ollowing
p oduc by weigh was he solid ac ion, being g ea e o B sample, due
o i s highe ash and ixed ca bon con en s. In any case, as i can also be
seen in Table 6, he yields ob ained wi h hese samples a e compa able
o hose ob ained in di e en wo ks ca ied ou wi h simila was e
s eams and ope a ing pa ame e s, whe e he p oduc gene a ed o a
la ge ex en was he liquid (60–70 w %), ollowed by he solid ac ion
(20–30 w %) and inally gases (10–15 w %). C sample, howe e , was
once again condi ioned by he g ea p esence o me als and o he ino -
ganic compounds in i s composi ion, p oducing a solid ac ion as i s
main p oduc . Liquids we e he second mos abundan p oduc ob ained
by his sample C, yielding 36 w %, a alue signi ican ly low compa ed o
he o he wo samples and he esul s om li e a u e, which a p io i
disca ded his sample as aw ma e ial o he gene a ion o oils.
3.3. Liquid ac ion cha ac e iza ion
The composi ion o he py olysis oils, de e mined as pe cen age o
GC–MS peak a ea, can be obse ed in Table 7. As i can be seen, he
composi ion o he liquids changed signi ican ly om samples A and B o
sample C, as did he py olysis yields and he cha ac e iza ion o he
samples hemsel es. The i s wo samples p esen ed wha can be
conside ed a ypical composi ion o a py olysis liquid coming om a
s y enic- ich plas ic s eam, wi h a g ea p esence o mono-a oma ic
hyd oca bons (MAH) such as s y ene, e hylbenzene and oluene,
oge he wi h a non-negligible concen a ion o phenol and i s de-
i a i es, ela ed o he p esence o oxygen in he samples. Such oil
Fig. 3. The mog a ime ic beha iou o samples A, B and C by means o dynamic analysis.
Table 6
Py olysis yields o he h ee samples: a compa ison wi h li e a u e.
Own wo k Li e a u e
A B C [9] [52] [53]
Was e Rejec ed WEEE
ac ion
Rejec ed
WEEE
ac ion
Plas ic om
sc ap
compu e s
Small
WEEE
Reac o Ba ch Semi-ba ch Ba ch Semi-
ba ch
Ope a ion
empe a u e
(◦C)
500 500 500 400
Solid yield (w .
%)
20.9 27.0 52.5 32.0 18.3 18.0
Liquid yield
(w .%)
68.6 59.9 36.0 61.0 63.9 74.0
Gas yield
(w .%)
10.5 13.1 11.5 7.0 17.8 8.0
B.B. Pe ez-Ma inez e al.
Ene gy Con e sion and Managemen 329 (2025) 119633
8
composi ions ha e al eady been epo ed by s udies ea ing simila
was e s eams unde he mal py olysis condi ions, whe e BTEX and
s y ene we e he p edominan compounds p esen [54–56]. I is no e-
wo hy he low concen a ion o poly-a oma ic hyd oca bons (PAH)
ound in hese wo oil samples. Finally, he p esence o benzenebu a-
neni ile was p obably de i ed om he ni ile g oups p esen in plas ics
such as ABS [57].
The esul s shown in Table 7 e ealed ha he highe concen a ion
o oxygen in sample C was ans e ed o he liquid ac ion du ing he
p ocess in he o m o oxygena ed o ganic compounds, such as phenols,
cap olac am, wa e and o he s. As s a ed be o e, he o igin o he highe
oxygen concen a ion could be a ibu ed o a g ea e complexi y o he
polyme s comp ising sample C, as he ones p esen in he esins o PCB.
This is in line wi h he composi ion o he liquid ac ion de i ed om
PCB py olysis obse ed in he li e a u e, whe e he main compounds
de ec ed happened o be phenolic and alkyl-phenolic compounds
[34,58]. The oxygen concen a ion also a ec ed he HHV o sample C
de i ed oils, which, in compa ison o samples A and B, is mo e han 10
MJ/kg lowe , as i can be seen in Table 7.
The composi ion o he liquids condi ioned he elemen al analysis
shown in Table 8. As he liquids de i ed om samples A and B we e
mos ly composed o hyd oca bons, hey showed a ca bon plus hyd ogen
con en nea 85 w %. These esul s a e expec ed when p ocessing his
ype o s eams unde he mal py olysis condi ions, since WEEE plas ics,
in gene al, end o deg ade in o oils composed mainly o ca bon and
hyd ogen, in weigh pe cen ages abo e 85 % [54]. Howe e , only a
31.8 w % o ca bon con en was ound in he sample C de i ed liquids
and he o al pe cen age o quan i ied elemen s was 64.2 w %, a a he
low alue. When calcula ing he elemen al balance o he p ocess, an
unde quan i ica ion o oxygen was de ec ed in he p oduc s o sample
C, so i is mos likely ha he oxygen analysis o hese liquids did no gi e
co ec esul s. The eason could be ha his oil was an o ganic liquid
sample wi h a high wa e con en , which gene a ed wa e –oil in e ace
zones in he o m o small d ople s ha may ha e condi ioned he ox-
ygen analysis, gi ing smalle alues han eal ones. The p esence o
phospho ous in hese liquids, no de e mined in his wo k, and pa o
some lame e a dan s, could also ha e in luenced his unbalanced
esul .
The pollu an s p esen in he o iginal samples we e ans e ed o he
gene a ed liquid ac ions, as can be seen in Table 8, and had a clea
impac wo sening he quali y o he oils de i ed om he h ee samples.
The oil om sample A had almos no sul u and a educed concen a ion
o halogens compa ed o he o iginal sample. The oil om sample B,
al hough main aining low sul u le els, con ained signi ican ly highe
quan i ies o halogens, which was a di ec consequence o he g ea e
concen a ion o hese in he o iginal sample. Finally, he oil om
sample C p esen ed a e y high le el o con amina ion, wi h alues o 1
w % o sul u , 10 w % o chlo ine and 2 w % o b omine, p obably
enhanced by he low liquid yield. I mus be men ioned ha he halogens
con en and hea ing alues epo ed in Table 8 o sample C a e based on
a single measu emen due o he di icul y o his sample o be com-
bus ed in he calo ime e .
3.4. Solid ac ion cha ac e iza ion and adso p ion es s
The solid ac ions ob ained in he py olysis o samples A, B and C, as
can be seen in Table 9, we e mainly composed o ash (52.1, 44.5 and
77.3 w %, espec i ely), whils ixed ca bon esul ed o be he second
mos abundan componen in hei he mog a ime ic analysis. These
esul s co ela e well wi h he ash con en epo ed by he p oxima e
analysis pe o med on he o iginal samples and we e o be expec ed. The
eason is ha he ino ganic con en o he ini ial samples is no mally
concen a ed in he py olysis solid, which is also composed o a ca bo-
naceous p oduc commonly e e ed o as cha , di ec ly de i ed om he
ca boniza ion o some plas ics and o he ma e ials such as wood o
pape ha could be p esen in he p ocessed samples. P e ious s udies
wo king wi h simila WEEE s eams also epo ed esul s whe e hal o
he py olysis solid was composed o ash, while he ola ile ma e and
he ixed ca bon con en cas ed alues close o 15 and 30 w % espec-
i ely [25,59]. As a as he ul ima e analysis is conce ned, he main
elemen de ec ed in all he h ee samples was ca bon, coming di ec ly
om he ixed ca bon p esen in he solid ac ion, as can be seen by
compa ing bo h he p oxima e and elemen al analyses. Sample C,
signi ican ly condi ioned by i s high ash con en , e ealed a lowe ca -
bon concen a ion. The second mos abundan elemen in all h ee
samples was oxygen, which seems o be e enly dis ibu ed among he
h ee py olysis ac ion. Smalle amoun s o hyd ogen, ni ogen and
pollu an s such as sul u , chlo ine and b omine we e also de ec ed in a
simila end epo ed by he au ho s when wo king on he py olysis o
Table 7
Liquids composi ion by GC–MS analysis (a ea %) and HHV (ni: no iden i ied).
Chemical amilies and subs ances / samples A B C
Hyd oca bons
Ole ins
1-Hexene 0.1 0.3 2.0
Monocyclic a oma ic hyd oca bons
Toluene 7.8 8.7 4.3
p-Xylene 2.1 2.6 0.0
E hylbenzene 8.6 10.3 0.0
P opylbenzene 0.7 1.5 0.0
S y ene 42.4 36.1 10.6
α
-Me hyls y ene 4.3 3.1 0.0
Polycyclic a oma ic hyd oca bons
1,3-Diphenylp opane 3.3 3.7 7.9
Non-hyd oca bons
Phenol 11.0 10.6 18.6
Alkylphenol 6.9 8.4 15.8
Benzenebu aneni ile 3.3 5.1 7.9
Cap olac am 0.0 1.7 7.6
Wa e 1.1 1.6 14.6
n.i. 8.0 6.4 10.5
HHV (MJ/kg) 36.2 32.7 20.9
Table 8
O ganic elemen al cha ac e iza ion (w .% ±STD, as gene a ed basis, n =3),
HHV and LHV (MJ/kg ±STD, as gene a ed basis, n =3) o py olysis oils.
C H N O S Cl B HHV LHV
A 80.0
±2.6
7.8
±
0.2
2.0
±
0.1
4.2
±
0.5
0.1
±
0.0
0.5
±
0.2
0.1
±
0.0
36.2
±0.5
34.7
±0.5
B 78.0
±2.8
8.5
±
0.2
2.5
±
0.3
4.2
±
0.2
0.1
±
0.0
2.8
±
1.8
0.3
±
0.1
32.7
±0.6
31.2
±0.6
C 31.8
±2.5
8.5
±
0.2
2.5
±
0.2
8.3
±
0.7
1.0
±
0.5
9.9 2.2 20.9 19.4
Table 9
Py olysis solids cha ac e iza ion.
Elemen al analysis (w .% ± STD, as gene a ed basis, n ¼3)
C H N O S Cl B
A 36.8 ±
2.4
1.5 ±
0.1
1.4 ±
0.2
6.1 ±
0.5
0.1 ±
0.1
1.1 ±
0.3
0.4 ±
0.1
B 36.1 ±
3.4
1.7 ±
0.1
1.2 ±
0.2
11.3 ±
1.7
0.1 ±
0.0
3.6 ±
0.2
0.6 ±
0.1
C 13.6 ±
1.8
0.6 ±
0.1
0.5 ±
0.1
11.8 ±
0.0
0.2 ±
0.0
0.9 ±
0.3
0.1 ±
0.0
P oxima e analysis (w .% ± STD; as gene a ed basis, n ¼3), and HHV (MJ/kg ±
STD, as gene a ed basis, n ¼3)
Mois u e Vola ile Ma e Ash Fixed Ca bon HHV
A 3.3 ±0.0 9.5 ±0.3 52.1 ±0.8 35.1 ±0.5 14.3 ±0.5
B 2.9 ±0.0 10.6 ±0.3 44.5 ±0.2 41.9 ±0.3 13.2 ±0.1
C 1.4 ±0.1 8.3 ±0.2 77.3 ±1.2 13.0 ±1.0 5.0 ±0.5
B.B. Pe ez-Ma inez e al.
Ene gy Con e sion and Managemen 329 (2025) 119633
9
phones ecycling ejec ed s eams [25]. As a as he HHV is conce ned,
i was closely ela ed o he ash con en o he py olysis solids, so ha he
highe he ash con en , he lowe he HHV o he solids. In his sense, he
py olysis solids o samples A and B p esen ed HHV alues sligh ly lowe
han hose ound o biomass uels [60,61], while he solid o sample C
could no be used compe i i ely as a uel.
The su ace a ea o he solid ac ions was measu ed as a i s s ep o
de e mine hei po en ial applica ion as adso ben s o chemicals in
wa e ; he esul s a e p esen ed in Fig. 4. Again, ino ganic ma e ials
(mainly me als) ha we e o su icien pa icle size o be de ec ed by he
naked eye we e emo ed by hand o he possible ex en be o e he
su ace a ea de e mina ion. The speci ic su ace a eas o he solids
de i ed om A, B and C samples we e 133.4, 89.1 and 36.7 m
2
/g
espec i ely, o which abou 92 % was mic opo ous a ea, as shown in
Fig. 4. These alues a e simila o he ones ound in he li e a u e o he
ac i a ed py olysis cha s de i ed om he py olysis o plas ics [62,63].
The adso p ion e iciency o he py olysis solids o an ibio ics in
wa e was measu ed as es ablished in sec ion 2.3.4., and he esul s a e
p esen ed in Table 10. In his case, he py olysis solid de i ed om
sample C was he one ha cas ed he bes esul s, being capable o
adso bing nea 100 % o he d ugs p esen in he wa e o each an i-
bio ic amily es ed. The esul s we e also in e es ing when i comes o
he adso p ion e iciency o sample B de i ed solid, wi h a emo al e -
iciency be ween 64 % and 81 % depending on he an ibio ic amily
es ed. The py olysis solid om sample A, on he o he hand, did no
pe o m well in he es , achie ing poo emo al e iciencies ha could
no each 50 % e iciency in any case.
The well-pe o ming esul s o he py olysis solid o sample C a e, a
a glance, qui e su p ising. On he one hand, his py olysis solid had he
smalles su ace a ea (36.7 m
2
/g) and, no mally, be e adso p ion e -
iciencies a e expec ed o g ea e su ace a eas. This could be explained
by he ac ha he adso p ion capaci y does no only depend on he
su ace a ea, since o he ac o s such as elec os a ic o ces, po e size,
hyd ogen bonds, hyd ophobic e ec s o chemiso p ion mus be also
aken in o accoun [64,65]. On he o he hand, his solid p oduc was
e y a om wha is conside ed an ac i a ed ca bon ( ypical indus ial
adso ben ), mainly because o i s high ash con en , which was 77.3 w %
e sus 8–10 w % o comme cial ac i a ed ca bons, e.g., Fil aso b. In
ac , he na u e o he py olysis solids om he h ee samples was p e-
dominan ly ino ganic, wi h some ca bonaceous con en . The e o e, he
high adso p ion e iciency o he py olysis solid o sample C should
pe haps y o be explained by i s me al oxide con en . Se e al wo ks can
be ound in he li e a u e conce ning he success ul adso p ion o an i-
bio ics in aqueous phase using adso ben s based on silica, alumina, i on,
calcium oxides and mix u es o hem [66–69]. When ca ying ou he
mass balance o he me als quan i ied in he o iginal sample C
(conside ing ha hey quan i a i ely emain in he solid ac ion in he
o m o oxides), i can be p o ed ha he py olysis solid o his sample is
composed o app oxima ely 20 w % silica, 7 w % calcium oxide and 5 w
% alumina, be ween o he ac i e me al oxides. The p esence o hese
oxides could explain he good adso p ion pe o mance o he py olysis
solids. In ac , i s ca bon con en (13.6 w %) could e en enhance he
adso p ion capaci y o his ma e ial, since ca bon–me al oxide com-
posi e adso ben s ha e been epo ed in li e a u e as e y e icien in he
an ibio ics adso p ion [70–72]. In summa y, i seems like his py olysis
solid could ac as a kind o mul i unc ional composi e adso ben ma e-
ial, especially e icien o an ibio ics emo al in wa e . This disco e y
will be s udied and analyzed mo e deeply by he au ho s in he nea
u u e. One o he issues ha need deepe in es iga ion is he possible
c oss con amina ion o he liquid phase wi h me als deso bed om he
py olysis solids. Lixi ia ion expe imen s ca ied ou by he au ho s
showed ha his phenomenon is possible, since concen a ions o Ni
(≤218 µg/L), Pb (≤470 µ g/L), Cu (≤201 µg/L) and C (≤7 µg/L) we e
measu ed in he elua e. Howe e , his issue mus be s udied in he same
condi ions as hose o he adso p ion expe imen s.
3.5. Gas ac ion cha ac e iza ion
Table 11 shows he composi ion o he gas ac ion de i ed om he
py olysis o he h ee samples, as well as i s HHV and LHV. The
composi ion o he gases is gi en in ni ogen, oxygen, wa e and pol-
lu an s ee basis. Conce ning pollu an s, hese gases we e cleaned by
ac i a ed ca bon adso p ion in he py olysis p ocess i sel , as desc ibed
in sec ion 2.2. Howe e , i is likely ha he cleaned gases s ill con ained
halides and maybe o he pollu an s no de ec ed by he GC-TCD/FID
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
A B C
Po e olume (cm3/g)
Su ace a ea (m2/g)
Su ace a ea
Mic opo e
su ace a ea
To al olume
in po es
Fig. 4. Solid ac ion su ace cha ac e iza ion.
Table 10
An ibio ic emo al e iciency in wa e o py olysis solids p oduced om samples
A, B and C (% ±STD, n =3).
A B C
PEN-G 17 ±10 64 ±31 98 ±2
PEN-V 28 ±14 73 ±28 99 ±1
AMOX 26 ±8 64 ±32 99 ±1
AMP 34 ±11 68 ±30 99 ±1
CARB 10 ±9 65 ±33 99 ±1
CLOX 48 ±24 81 ±23 100 ±0
Table 11
Py olysis gas composi ion and hea ing alues.
Gases composi ion
Compound A B C
ol.% w .% ol.% w .% ol.% w .%
CO
2
28.8 43.1 10.0 18.8 7.1 14.5
H
2
13.6 0.9 22.3 1.9 27.3 2.6
CO 15.7 15.0 7.7 9.2 11.6 15.1
C
2
H
4
5.2 4.9 10.1 12.1 7.6 9.9
C
2
H
6
6.7 6.9 12.0 15.4 8.3 11.6
CH
4
17.0 9.3 24.7 16.9 25.4 18.9
C
3
H
6
9.1 13.6 8.1 15.2 6.1 12.3
C
3
H
8
2.3 3.3 2.6 4.6 3.1 6.1
C4 1.5 3.0 2.4 5.7 3.1 8.1
C5 0.0 0.0 0.1 0.2 0.3 0.9
Gases hea ing alue
A B C
MJ/kg MJ/Nm
3
MJ/kg MJ/Nm
3
MJ/kg MJ/Nm
3
HHV 23.7 27.3 39.5 36.4 39.9 33.8
LHV 22.0 25.4 36.5 33.7 36.8 31.2
B.B. Pe ez-Ma inez e al.
