ECO-EFFICIENT PROCESSING AND REFINING ROUTES FOR SECONDARY RAW MATERIALS FROM
SILICON INGOT AND WAFER MANUFACTURING
Ma in Bellmann*1, Be hane Da sene Dimd1, Anne-Ka in Søiland2, A ne Dahle3, C. Landaas4, Vic o ien
Iwaszko5, Rene Peche6, Wol am Pali zsch7, Philippe Lenain8, I a xe de Mea za9, Theodo a Ky a si10, Liu Huiping11,
Emanuele Milani12, Guy Chichignoud13, S e an Fische 14, Almu Schwenke15, Ei ik No dboe16, Ma co Pie e se17,
Roland Ri a18
1SINTEF, T ondheim No way, 2ReSiTec AS, K is iansand No way, 3No Sun, Oslo No way, 4No he n Silicon, Me åke
No way, 5ROSI Sola , Sain -Ma in-d’Hè es F ance, 6bi a Umwel ins i u GmbH, Augsbu g Ge many, 7LuxChem ech
GmbH, F eibe g Ge many, 8benkei, Lyon F ance, 9CIDETEC, San Sebas ian Spain, 10Uni e si y o Cyp us, Nicosia
Cyp us, 11GRÄNGES, Finspång Sweden, 12Ma elli Eu ope SPA, Vena ia Reala I aly, 13Ins i u Poly echnique De
G enobl, G enoble F ance, 14SGL Ca bon GmbH, Mei ingen Ge many, 15SGL Ba e y Solu ions, Mei ingen Ge many,
16Fi en No ge AS, Lillesand No way, 17Chemconse e, Bussum The Ne he lands, 18Commissa ia à l’éne gie a omique e
aux éne gies al e na i es, Le Bou ge -du-Lac F ance
ABSTRACT: In he ICARUS p ojec , 18 Eu opean pa ne s collabo a e o de elop and scale inno a i e echnologies
o eco e ing and e ining seconda y aw ma e ials om silicon pho o ol aic (PV) ingo and wa e manu ac u ing.
The p oduc ion o PV modules gene a es signi ican quan i ies o was e, pa icula ly silicon ke , g aphi e, and silica
esidues. ICARUS aims o ans o m hese was e s eams in o high- alue seconda y ma e ials sui able o ein eg a ion
in o he PV alue chain and o he indus ial applica ions. Fou indus ial pilo -scale p ocesses we e de eloped, a ge ing
he pu i ica ion and euse o hese ma e ials. Resul s om he pilo s demons a e bo h he echnical easibili y and
economic po en ial o subs i u ing hese eco e ed ma e ials o i gin and c i ical aw ma e ials. This wo k p o ides a
iable pa hway owa d a mo e esou ce-e icien and ci cula PV manu ac u ing indus y.
Keywo ds: Pho o ol aics, Silicon, Silicon Ke , Silica, Recycling, Ci cula i y
1 INTRODUCTION
Global deploymen o pho o ol aic (PV) echnology
con inues o accele a e, d i en by declining module cos s
and ne -ze o emission a ge s. Alongside his g ow h, he
silicon PV alue chain gene a es subs an ial p oduc ion
was es du ing ingo manu ac u ing and wa e ing. These
include silicon ke losses om wa e ing, as well as silica
and g aphi e componen s om c ys alliza ion u naces. A
signi ican p opo ion o hese was es is ei he disposed o
in land ills o di e ed in o low- alue applica ions. Such
p ac ices no only esul in he loss o po en ially aluable
ma e ials bu also con lic wi h sus ainabili y and ci cula
economy p inciples.
In gene al he li e a u e demons a es clea p og ess in
eco e ing high-pu i y p oduc s om silicon ke [1],
silica was e [2], and g aphi e [3]. Howe e , cu en
me hods gene ally yield seconda y ma e ials wi h limi ed
eco e y e iciency and insu icien quali y o high- alue
euse. In addi ion, signi ican ecycling echniques a e no
ye scalable o indus ial le el due o hei complexi y and
mul i-s age app oach. The ICARUS p ojec add esses his
challenge by de eloping and scaling indus ially ele an
ou es o he eco e y, e inemen , and ein eg a ion o
seconda y aw ma e ials om ingo and wa e
manu ac u ing.
The ICARUS p ojec is a collabo a i e e o be ween
18 EU (Eu opean Union) pa ne s. The wo k ocuses on
de eloping a ge ed echnological solu ions o e ine and
euse silicon ke , g aphi e, and silica was es om PV
manu ac u ing. Fou indus ial pilo echnologies ha e
been designed and es ed a pilo scale o assess imp o ed
ecycling p ocesses, wi h he po en ial o ou pe o m
exis ing me hods. The main goal is he p oduc ion o high-
pu i y, high- alue seconda y aw ma e ials, he eby
add essing he quali y limi a ions o en encoun e ed in
cu en ecycling app oaches. By 2027, he p ojec aims o
enable la ge-scale esou ce eco e y, wi h p ojec ed
capaci ies o 3.5 million ons o silicon ke , 700 housand
ons o silica, and 480 housand ons o g aphi e,
demons a ing bo h scalabili y and economic iabili y.
The wo k in ICARUS con ibu es di ec ly o sus ainabili y
and ci cula economy goals by ans o ming was e in o
eusable aw ma e ials, educing en i onmen al impac s,
and imp o ing he o e all e iciency o he silicon PV
alue chain.
2 METHODOLOGY
This sec ion p o ides a b ie o e iew o he ICARUS
p ojec and PV was e olume es ima es and
cha ac e iza ion. I also discusses he ou pilo -scale
ecycling echnologies de eloped o silicon ke ,
g aphi e, and silica.
2.1 O e iew o ICARUS
The ICARUS p ojec is o ganized in o six wo k
packages (WPs). WP1 add eses logis ics, ea men ,
quali y, quan i y, and sou cing o silicon PV p oduc ion
was e. WP2 de elops indus ial ou es o collec ing and
p e- ea ing silicon, silica, and g aphi e. WP3 ein oduces
hese was es in o silicon p oduc ion, while WP4 ocuses
on con olled condi ioning o pu i ied silicon. WP5
upg ades a lab-scale eac o o semi-indus ial scale o
con e ing silicon was e in o aluable ma e ials. Finally,
WP6 d i es ma ke up ake by demons a ing high-end
p o o ypes ha u ilize eco e ed silicon, silica, and
g aphi e.
2.2 Was e olume es ima es and cha ac e iza ion
PV ingo manu ac u ing gene a es signi ican was e.
To assess he po en ial o ecycling pa hways, i is
essen ial o es ima e was e olumes and cha ac e ize
ma e ials. Volume es ima es p o ide con ex o he scale
o he challenge, while cha ac e iza ion suppo s
e alua ion o echnical easibili y and p ocessing needs. In
his wo k, silicon ke was e was es ima ed using ac o s
such as annual PV ins alla ions, he a io o p oduc ion o
ins alla ions, c ys alline PV p oduc ion olumes, and he
cell- o-wa e a io. Es ima es o c ucible and po sc ap
was e assumed mul i-ba ch ingo pulling wi h M10 and
G12 wa e dimensions, while g aphi e was e was
es ima ed a 100 ons pe gigawa o PV capaci y, as
epo ed by [4].
The cha ac e iza ion o was e ma e ials and p oduced
silicon was ca ied ou using se e al analy ical echniques.
Induc i ely Coupled Plasma Mass Spec ome y (ICP-
MS) was applied o de ec me allic and non-me allic
impu i ies a ace le els, while LECO analysis was used
o quan i y ca bon and oxygen con en s. X- ay Di ac ion
(XRD) was employed o de e mine c ys allog aphic
s uc u e and phase composi ion, and Scanning Elec on
Mic oscopy (SEM) was used o examine su ace
mo phology. Toge he , hese echniques assess chemical
pu i y and mo phology, ensu ing ecycled ma e ials mee
quali y s anda ds o high-pe o mance applica ions.
2.3 Pilo echnologies
The ou indus ial pilo echnologies which a e he
co e o he ICARUS p ojec a e:
• Pilo A: Collec s and p ocesses silicon ke cake,
g aphi e, and silica was e acco ding o de ined
s anda ds, deli e ing he ma e ial ei he o end-
use g oups o inal applica ions o o o he
pilo s o u he e ining.
• Pilo B: Aims o p oduce silicon wi h highe
quali y and a a lowe cos han con en ional
me allu gical silicon p ocesses. This pilo uses
seconda y ma e ials such as g aphi e, silica, and
silicon ke in a pilo -scale subme ged a c
u nace (SAF).
• Pilo C: Scales up he annual con olled
condi ioning o silicon, based on ma e ial
ecei ed om Pilo A o a capaci y o 500 ons
pe yea , aiming o imp o e he quali y o
g anula silicon o PV applica ions.
• Pilo D: Will scale up a small-scale eac o o a
semi-indus ial le el, a ge ing a capaci y o 50–
70 ons pe yea . The p ocess is based on he
eac ion o ee silicon in he ke wi h a sodium
hyd oxide solu ion unde con olled empe a u e
and p essu e condi ions, p oducing hyd ogen,
sodium silica es, and eac ion hea .
3 RESULT AND DISCUSSION
This sec ion epo s he key indings om was e
olume es ima es and ma e ial cha ac e iza ion, along
wi h esul s om he ou pilo p ojec s, wi h emphasis on
Pilo B.
3.1 Was e olume es ima es and cha ac e iza ion esul
The es ima ion o silicon ke was e accoun s o
losses om wa e ing as well as c opping, squa ing,
cham e ing, and g inding ope a ions. Figu e 1 shows he
es ima ed global cumula i e ke gene a ion om 2018 o
2027, indica ing ha annual olumes could each abou
700 kMT by 2027. Simila ly, Figu e 2 p esen s p ojec ed
cumula i e silica and g aphi e was es om 2023 o 2027.
O e all, hese es ima es highligh he subs an ial olumes
o was e gene a ed in ingo and wa e manu ac u ing.
Al hough ypically ea ed as was e, hese ma e ials
ep esen a aluable oppo uni y o ecycling and
ein eg a ion in o he PV alue chain and o he
applica ions.
Figu e 1: Cummula i e silicon ke was e in kMT.
Figu e 2: Cummula i e silica and g aphi e was e in on.
Impu i y analysis o silicon ke samples om
di e en sou ces was conduc ed using ICP-MS. The
esul s show ha he main dopan impu i ies a e bo on,
gallium, and phospho us, wi h concen a ions a ying
ac oss samples. The main me allic impu i ies include
aluminum, calcium, i on, and nickel. LECO analysis
indica ed ca bon concen a ions o 1–2 w .% and oxygen
con en o 4–5 w .% in mos samples. SEM and XRD
analyses e ealed i egula mo phologies, wi h he ke
consis ing mainly o c ys alline silicon and an amo phous
phase.
LECO analysis o i e g aphi e powde samples
e ealed signi ican ly highe ash con en compa ed o a
i gin e e ence sample. ICP-MS analysis o he ash
iden i ied silicon, cobal , and calcium as he main
impu i ies. XRD esul s showed he p esence o g aphi e
2H, SiC, and c ys alline SiO2 phases, while SEM e ealed
mul iple phases wi h dis inc mo phologies ac oss
di e en egions o he samples. Simila cha ac e iza ion
was ca ied ou on silica was e samples, which we e ound
o consis mainly o amo phous silica and c ys alline
c is obali e, wi h calcium iden i ied as he p ima y
impu i y.
3.2 Resul s om he pilo s
The ICARUS p ojec aims o ans o m silicon ke ,
g aphi e, and silica was e in o high- alue seconda y aw
ma e ials by de eloping and scaling ou pilo
echnologies o e icien ecycling. This sec ion p esen s
hei esul s, wi h a mo e ocus on Pilo B, chosen as he
mos ep esen a i e o he o e all p ocessing chain, while
summa izing key ou comes om he o he pilo s.
Pilo A: Indus ial-scale p ocessing ou es o silicon
ke was e ha e been es ablished a Technology Readiness
Le el (TRL) 7. A con inuous d ying sys em has been
success ully commissioned as an al e na i e o he exis ing
ba ch d ying p ocess o silicon ke il e cake. This
sys em achie es mois u e le els o less han 1 w %.
Addi ionally, an indus ial-scale pos ea men p ocess
has been de eloped o ma e ial in ended o use in o
li hium-ion ba e ies and he moelec ic modules. A
p e ea men p ocess has also been implemen ed o
signi ican ly educe con aminan s such as aluminum,
nickel, and i on. Fo he silica was e, a p ocessing ou e
has been de eloped and a pilo line es ablished, a ge ing
aw ma e ial speci ica ion sui able o p oduc ion o high
pu i y silicon ca bide.
Pilo B: This pilo aimed o ein oduce silicon ke ,
g aphi e, and silica was e in o he silicon alue chain
h ough ca bo he mic educ ion. Two expe imen al
campaigns we e ca ied ou in a pilo -scale SAF. The
p ocess began wi h he collec ion and p e ea men o aw
ma e ials, ollowed by agglome a ion in o sel - educing
b ique es. Th ee ypes o b ique es we e made, Type A
(pu e qua z and ca bon black wi h binde and wa e ),
Type B (po sc ap, ca bon black, binde , and wa e ), and
Type C (silicon ke wi h binde and wa e ). These
b ique es we e hen subjec ed o pilo -scale ca bo he mic
educ ion in he SAF o p oduce silicon, which was
subsequen ly analyzed o de e mine i s pu i y. The wo
expe imen al campaigns which we e un o e a pe iod o
h ee days and h ee nigh s consis ed o wo expe imen s,
o aling ou expe imen s. These a e:
• EXP 1: Type A b ique es and qua z lumps as
cha ge.
• EXP 2: Type A b ique es, qua z lumps, and po
sc ap lumps as cha ge.
• EXP 3: Type B b ique es and po sc ap lumps
as cha ge.
• EXP 4: Type B and Type C b ique es and po
sc ap lumps as cha ge.
Ac oss wo SAF campaigns, a o al o 92 kg o silicon
was p oduced h ough wel e apping ope a ions. In he
i s campaign (EXP 1 and EXP 2), 60 kg o silicon was
ob ained, while he second campaign (EXP 3 and EXP 4)
yielded 32 kg. ICP-MS analysis o six samples om each
ap (Tables I) con i med ha he p oduced silicon me
me allu gical-g ade pu i y equi emen s [5], wi h he
second campaign achie ing sligh ly highe pu i y han he
i s .
Table I: Pu i y o he apped silicon measu ed by ICP-MS.
Pu i y (%)
Sample
Campaign 1
Campaign 2
1
97.87
98.43
2
98.27
98.16
3
98.47
98.01
4
98.39
98.47
5
98.34
98.78
6
98.79
98.05
De ailed ICP-MS analysis o Campaign 1 samples
showed phospho us as he dominan dopan , sligh ly abo e
me allu gical-g ade h esholds, while bo on and gallium
emained wi hin limi s. Aluminum exceeded he h eshold
in ea ly appings bu s abilized la e , i on was accep able
in hal o he appings, and i anium consis en ly exceeded
limi s; o he me als we e wi hin ange, con i ming o e all
sui abili y o me allu gical-g ade silicon. In Campaign 2,
phospho us and bo on le els dec eased, gallium inc eased,
and aluminum and i on we e well con olled, hough
calcium, i anium, ch omium, and nickel exceeded
h esholds. Despi e hese a ia ions, i can be concluded
ha he p oduced silicon in his campaign me
me allu gical-g ade s anda ds, an encou aging esul gi en
ha 70% o he eeds ock came om ecycled po sc ap
and ke .
Pilo C: A combined sys em o powde eeding,
mel ing, solidi ica ion, and g anula ion has been
de eloped and commissioned. The powde eeding uni
has a capaci y o 500 ons pe yea , while he mel ing and
g anula ion uni s handle 50 ons pe yea . The p ocess
success ully demons a ed he p oduc ion o ecycled
silicon a a low a e o 1 kg/h, achie ing 4N pu i y.
Pilo D: A chemical con e sion p ocess o silicon
was e has been scaled up o 87 ons pe yea , p oducing
wa e glass and g een hyd ogen o di e se ma ke
applica ions. End-o -li e PV panels and semiconduc o
indus y esidues we e also shown o be aluable
al e na i e sou ces o ma e ial eco e y.
4 CONCLUSIONS
This s udy h ough he ICARUS p ojec highligh s he
subs an ial olumes o silicon ke , silica, and g aphi e
was e gene a ed du ing ingo and wa e manu ac u ing and
demons a es hei huge po en ial as aluable seconda y
aw ma e ials. De ailed cha ac e iza ion o hese was es
con i med he sui abili y o hese was es as subs i u es o
i gin ma e ials, while he success ul implemen a ion o
ou pilo echnologies wi hin he ICARUS p ojec
alida ed he echnical easibili y o hei eco e y and
euse. Toge he , hese esul s p o ide a s ong ounda ion
o in eg a ing ecycling in o he PV alue chain,
ad ancing bo h sus ainabili y and ci cula economy
objec i es in he PV indus y.
5 ACKNOWLEDGEMENT
This wo k is pa o ICARUS p ojec unded by
Ho izon 2020 esea ch and inno a ion p og amme unde
g an ag eemen No 958365.
6 REFERENCES
[1] Li, J., Lin, Y., Wang, F., Shi, J., Sun, J., Ban, B., Liu,
G. and Chen, J., 2021. P og ess in eco e y and ecycling
o ke loss silicon was e in pho o ol aic indus y.
Sepa a ion and Pu i ica ion Technology, 254, p.117581.
h ps://doi.o g/10.1016/j.seppu .2020.117581.
[2] Yang, S., Han, S., Chen, J., Wei, K. and Ma, W., 2024.
A sus ainable mine al p ocess o silicon and qua z
eco e y om qua z c ucible was e ash ia elec ical
sepa a ion. Mine als Enginee ing, 216, p.108887.
h ps://doi.o g/10.1016/j.mineng.2024.108887.
[3] Zhang, Y., Z. Chen, K. Xie, X. Chen, Y. Hu, and W.
Ma. Pu i ica ion o Was e G aphi e om C ucibles Used
in Pho o ol aic C ys alliza ion by an Alkali-Acid
Me hod. Me als 2023, 13, 1180. 2023.
h ps://doi.o g/10.3390/me 13071180.
[4] B ailo sky, P., Baumann, K., Held, M., B iem, A.K.,
Wambach, K., Ge ais, E., He ceg, S., Me oy, B., Nold,
S. and Ren sch, J., 2023. Insigh s in o ci cula ma e ial and
was e lows om c-Si PV indus y. EPJ Pho o ol aics, 14,
p.5. h ps://doi.o g/10.1051/epjp /2022029.
[5] Me allu gical-G ade Silicon (MGS) - WikiChip.
h ps://en.wikichip.o g/wiki/me allu gical-
g ade_silicon#google_ igne e.
