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T eball eali za pe :
Ma ia Lluna Fo nells Ce nadas
Di igi pe :
Jaume Puigagu Juá ez
Diego Apon e He nández
G au en:
Enginye ia Ambien al
Ba celona, Feb ua y 2025
Depa amen d’Enginye ia Ci il i Ambien al (DECA)
Assessing he use o P-en iched s eel
slag as a sus ainable al e na i e o
con en ional e ilize s o c op
p oduc ion
TREBALL FINAL DE GRAU
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TABLE OF CONTENTS
ABSTRACT ............................................................................................................................... 5
RESUM ...................................................................................................................................... 6
RESUMEN ................................................................................................................................ 7
TABLES .................................................................................................................................... 8
FIGURES ................................................................................................................................... 9
ABBREVIATIONS ................................................................................................................. 10
1. In oduc ion ...................................................................................................................... 11
2. Objec i es ........................................................................................................................ 13
3. Li e a u e e iew and basic concep s ............................................................................... 14
3.1. Phospho us ............................................................................................................... 14
3.1.1. Phospho us cycle ............................................................................................. 14
3.1.2. Phospho us and plan me abolism ................................................................... 15
3.1.3. Sou ces and deple ion ...................................................................................... 16
3.1.4. Phospho us in an ag icul u al con ex .............................................................. 16
3.2. S eel slags................................................................................................................. 17
3.2.1. O igin and cha ac e is ics ................................................................................ 17
3.2.2. Slags as e ilize s ............................................................................................ 18
3.3. Mic obial ac i i y and egene a i e ag icul u e ....................................................... 19
3.4. Me als and hea y me als o in e es ......................................................................... 20
4. Ma e ials and me hodology.............................................................................................. 23
4.1. Expe imen al design................................................................................................. 23
4.1.1. Replicas and amendmen s ................................................................................ 23
4.1.2. Expe imen al se up and conside a ions ............................................................ 24
4.1.3. Ma e ials and p oceedings ............................................................................... 25
4.2. Va iables conside ed and moni o ed ........................................................................ 29
4.2.1. Plan heal h....................................................................................................... 29
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4.2.2. Soil heal h ........................................................................................................ 32
4.2.3. En i onmen al ac o s ...................................................................................... 35
5. Resul s .............................................................................................................................. 38
5.1. Plan heal h and g ow h ........................................................................................... 38
5.2. Soil heal h ................................................................................................................ 43
5.3. Slag’s me als a e: plan and leacha e. ..................................................................... 46
6. Conclusions ...................................................................................................................... 50
6.1. Limi a ions ............................................................................................................... 51
6.2. Fu u e lines o easea ch .......................................................................................... 51
7. Sus ainabili y analysis and e hical implica ions .............................................................. 53
7.1. De elopmen o he hesis ........................................................................................ 53
7.1.1. En i onmen al pe spec i e ............................................................................... 53
7.1.2. Economic pe spec i e ...................................................................................... 57
7.1.3. Social pe spec i e ............................................................................................ 59
7.2. Po en ial execu ion o he p ojec ............................................................................ 59
7.2.1. En i onmen al pe spec i e ............................................................................... 59
7.2.2. Economic pe spec i e ...................................................................................... 60
7.2.3. Social pe spec i e ............................................................................................ 60
7.3. Risks and limi a ions ................................................................................................ 61
7.4. E hical implica ions ................................................................................................. 62
7.5. Sus ainable De elopmen Goals .............................................................................. 62
REFERENCES ........................................................................................................................ 64
ACKNOWLEDGEMENTS ..................................................................................................... 70
ANNEX I ................................................................................................................................. 71
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ABSTRACT
Phospho us (P) is a c i ical mac onu ien essen ial o plan g ow h, oo de elopmen , and
ood p oduc ion. I plays a cen al ole in ene gy ans e , nucleic acid syn hesis, and memb ane
o ma ion, making i i al o global ood secu i y. As a ini e esou ce p ima ily ob ained om
sedimen a y ock mining, i s deple ion and en i onmen al impac ha e made cu en p ac ices
unsus ainable. The Eu opean Commission has classi ied P as a C i ical Raw Ma e ial
(Eu opean Commission, 2020), emphasizing he need o eco e y and ecycling.
This s udy e alua es he easibili y o phospho us-en iched s eel slags as a sus ainable
al e na i e o con en ional e ilize s h ough an 8-week con olled ag onomical expe imen
using basil plan s (Ocimum basilicum). Fi e condi ions we e es ed: a nega i e con ol (C-, no
e ilize ), a posi i e con ol (C+, s anda d e ilize ), and h ee ea men s wi h P-en iched slag
a a ying concen a ions (E, E10, and E20). Resul s showed ha slag amendmen s e ec i ely
p o ided bioa ailable phospho us. The E10 ea men , con aining 10 imes he phospho us
con en o C+, was he mos e ec i e in e ms o biomass p oduc ion. En i onmen al analysis
con i med minimal me al leaching, wi hin in e na ional sa e y h esholds. This esea ch
highligh s he po en ial o s eel slags o egene a i e ag icul u e, suppo ing phospho us
ecycling and sus ainable nu ien managemen . Fu he s udies a e ecommended o op imize
slag applica ion me hods and assess long- e m soil impac s.
Key wo ds: Phospho us, S eel Slags, Sus ainable Ag icul u e, Regene a i e Ag icul u e,
Nu ien Recycling, Mic obial Ac i i y, Bioa ailable Phospho us, Ci cula Economy,
En i onmen al Sa e y
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RESUM
El òs o (P) és un mac onu ien c í ic essencial pe al c eixemen de les plan es, el
desen olupamen de les a els i la p oducció d'alimen s. Juga un pape cen al en la
ans e ència d'ene gia, la sín esi d'àcids nucleics i la o mació de memb anes, e que el
con e eix en i al pe a la segu e a alimen à ia mundial. Com a ecu s ini ob ingu
p incipalmen a a és de la mine ia de oques sedimen à ies, el seu esgo amen i impac e
ambien al han e insos enibles les p àc iques ac uals. La Comissió Eu opea ha classi ica el P
com a Ma è ia P ime a C í ica (Eu opean Commission, 2020), des acan la necessi a de
ecupe a i ecicla aques elemen .
Aques es udi a alua la iabili a de les escò ies d'ace en iquides amb òs o com a al e na i a
sos enible als e ili zan s con encionals mi jançan un expe imen con ola de 8 se manes amb
plan es d’al àb ega (Ocimum basilicum). Es an p o a cinc condicions: un con ol nega iu (C-
, sense e ili zan ), un con ol posi iu (C+, e ili zan es ànda d) i es ac amen s amb escò ies
en iquides amb òs o a di e en s concen acions (E, E10 i E20). Els esul a s an demos a
que els ac amen s amb escò ies p opo ciona en òs o biodisponible. El ac amen E10, que
con enia 10 egades el con ingu de òs o de C+, a se el més e ec iu. L’anàlisi ambien al a
con i ma una lixi iació mínima de me alls, dins dels llinda s in e nacionals de segu e a .
Aques a in es igació des aca el po encial de les escò ies d’ace pe a una ag icul u a
egene a i a, donan supo al ecicla ge de òs o i a una ges ió sos enible dels nu ien s. Es
ecomanen es udis addicionals pe op imi za els mè odes d’aplicació de les escò ies i a alua
els impac es a lla g e mini sob e la salu del sòl.
Pa aules clau: Fòs o , Escò ies d’Ace , Escò ies Neg es, Ag icul u a Sos enible, Ag icul u a
Regene a i a, Recicla ge de Nu ien s, Ac i i a Mic obiana, Fòs o Biodisponible, Economia
Ci cula , Segu e a Ambien al
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RESUMEN
El ós o o (P) es un mac onu ien e c í ico esencial pa a el c ecimien o de las plan as, el
desa ollo de las aíces y la p oducción de alimen os. Desempeña un papel cen al en la
ans e encia de ene gía, la sín esis de ácidos nucleicos y la o mación de memb anas, lo que
lo hace i al pa a la segu idad alimen a ia global. Como ecu so ini o ob enido p incipalmen e
a a és de la mine ía de ocas sedimen a ias, su ago amien o y su impac o ambien al han uel o
insos enibles las p ác icas ac uales. La Comisión Eu opea ha clasi icado el P como Ma e ia
P ima C í ica (Eu opean Commission, 2020), des acando la necesidad de su ecupe ación y
eciclaje.
Es e es udio e alúa la iabilidad de las esco ias de ace o en iquecidas con ós o o como una
al e na i a sos enible a los e ilizan es con encionales median e un expe imen o con olado
de 8 semanas con plan as de albahaca (Ocimum basilicum). Se p oba on cinco condiciones: un
con ol nega i o (C-, sin e ilizan e), un con ol posi i o (C+, e ilizan e es ánda ) y es
a amien os con esco ias en iquecidas con ós o o en di e en es concen aciones (E, E10 y
E20). Los esul ados demos a on que los a amien os con esco ias p opo ciona on ós o o
biodisponible, mejo ando la biomasa ege al, el desa ollo de las aíces y la ac i idad
mic obiana. El a amien o E10, que con enía 10 eces el con enido de ós o o de C+, ue el
más e ec i o. El análisis ambien al con i mó una lixi iación mínima de me ales, den o de los
lími es in e nacionales de segu idad. Es a in es igación des aca el po encial de las esco ias de
ace o pa a una ag icul u a egene a i a, apoyando el eciclaje de ós o o y una ges ión
sos enible de nu ien es. Se ecomiendan es udios adicionales pa a op imiza los mé odos de
aplicación de las esco ias y e alua los impac os a la go plazo sob e la salud del suelo.
Palab as cla e: Fós o o, Esco ias de Ace o, Esco ias Neg as, Ag icul u a Sos enible,
Ag icul u a Regene a i a, Reciclaje de Nu ien es, Ac i idad Mic obiana, Fós o o
Biodisponible, Economía Ci cula , Segu idad Ambien al
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TABLES
Table 1. Mos common chemical composi ions o EAF slag in Spain. Sou ce: Ska e al., 2017
.................................................................................................................................................. 18
Table 2. Collec ion o uppe limi s o ecommended in akes o he selec ed lis o me als o
wa e and ood consump ion. Sou ce: Eu opean Commission, 2023; Ins i u e o Medicine, US,
1997-2011, WHO, 2022. Excep o : ....................................................................................... 21
Table 3. Composi ion o he soil in he di e en amended soils. ........................................... 24
Table 4. Ini ial nu ien and physical p ope ies o he pea -moss. .......................................... 26
Table 5. Me al in s eel slag’s leacha e compa ed o Spanish limi s se by he Dec e o 32/2009,
de 24 de eb e o ....................................................................................................................... 27
Table 6. Chemical composi ion o he adap ed Hoagland solu ion. ........................................ 28
Table 7. Wa e ing amoun s du ing he i s 3 weeks. .............................................................. 35
Table 8. A e age chlo ophyll eadings h oughou he du a ion o he expe imen pe
expe imen al condi ion and s anda d de ia ion. ...................................................................... 39
Table 9. Plan heigh a e age ini ial and inal eadings and hei s anda d de ia ion pe
en i onmen al condi ion .......................................................................................................... 41
Table 10. Final nu ien con en and physical condi ions o he soil pe each expe imen al
condi ion. ................................................................................................................................. 44
Table 11. Leacha e esul s in compa ison wi h d inking wa e guidelines (sou ce in Table 2 o
his p esen documen ) and slag’s leacha e analysis. The esul s o he ab wa e used o
wa e ing and he Hoagland solu ion p o ide a concep ual ze o o he esul s. In bold he
maximum alues. Highligh ed in ligh ed he alues ha su pass he e e ence alues......... 47
Table 12. Me al concen a ion wi hin plan issue compa ed o maximum and e e ence in akes
o he s udied me als (Sou ce in able 2). In bold he maximum alues. Highligh ed in ligh
ed he alues ha su pass he e e ence alues. ...................................................................... 48
Table 13. To al me al amoun pe a e age plan o each o he expe imen al condi ions. In bold
he maximum alues. ............................................................................................................... 49
Table 14. Ca bon oo p in calcula ion including he in en o y, he alue, he emission ac o
used and i s sou ces and he o al alues. ................................................................................. 55
Table 15. Cos pe indi idual i em o he p ojec . To al cos calcula ion. ............................... 58
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FIGURES
Figu e 1. Expe imen se up. .................................................................................................... 25
Figu e 2. Plan iew o a g oup o po s, showing he soil mix u e used. .................................. 26
Figu e 3. Pic u e o he slags used as amendmen s. ................................................................. 28
Figu e 4. Pic u es du ing he inal ha es . .............................................................................. 29
Figu e 5. Chlo ophyll me e SPAD plus Konika Minol a. ...................................................... 30
Figu e 6. Abso bance peaks o chlo ophyll. Sou ce: Spad-plus manual ................................. 30
Figu e 7. Co ela ion be ween SPAD alue and ni ogen concen a ion o basil plan s. Fon :
(Ruiz-Espinoza e al., 2010) ..................................................................................................... 31
Figu e 8. Se up o he analysis o mic obial ac i i y using he ATP ex ac ion me hod. ...... 33
Figu e 9. Rhizon sample s o po e wa e ex ac ion a ached o a lue sy inge. .................... 34
Figu e 10.LED ligh s used. ...................................................................................................... 36
Figu e 11. Ligh in ensi y dis ibu ion [Klux]. Each cell o he igu e ep esen s a po posi ion
wi hin he expe imen al se -up. ................................................................................................ 37
Figu e 12. Dis ibu ions used h oughou he expe imen . The colou e e s o he expe imen al
condi ion: blue (C-), pink (C+), g een (Esc), o ange (Esc 10) and yellow (Esc20). The numbe s
e e o he speci ic eplica wi hin he expe imen al condi ion (1-4). ...................................... 37
Figu e 13. Chlo ophyll eadings pe en i onmen al condi ion h ough ime. ......................... 39
Figu e 14. Plan heigh a e age eadings pe en i onmen al condi ion in ime. ..................... 40
Figu e 15. Final plan weigh (abo e and below g ound) a e age and s anda d de ia ion and
mois u e a e age con en pe expe imen al condi ion. ............................................................ 42
Figu e 16. Bellow g ound ( oo s) inal weigh (a e age and s anda d de ia ion) and leng h
(a e age) pe expe imen al condi ion ...................................................................................... 42
Figu e 17. Mic obial ac i i y a e age in ime pe expe imen al condi ion. ............................. 43
Figu e 18. Mic obial ac i i y ini ial and inal alues (a e age and s anda d de ia ion) pe
expe imen al condi ion............................................................................................................. 44
Figu e 19. Nu ien con en (Ca, C and N) in pe cen age o d y weigh and pH o he inal soil
pe expe imen al condi ion ...................................................................................................... 45
Figu e 20. pH a e age o leacha e samples in ime pe expe imen al condi ion ..................... 46
Figu e 21. Pic u es o he plan s be o e he ha es 06/06/2024.............................................. 71
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g a i opic de elopmen , and dense and longe oo hai s (Poi ie e al., 2022). Addi ionally,
plan s ha e e ol ed sophis ica ed mechanisms o sense and espond o a ia ions in Pi
a ailabili y (Khan e al., 2023).
3.1.3. Sou ces and deple ion
App oxima ely 90% o mined P is used in e ilize p oduc ion o sus ain c op yields (Poi ie
e al., 2022). The e a e wo ypes o P mining: su ace mining (up o 100m below g ound) and
unde g ound mining (>100m). Su ace mining can a ec a wide a ea han unde g ound
leading o e osion o soils. Du ing he ex ac ion p ocess wa e usage a ec s he hyd ology o
he a ea. Following ex ac ion, he p oduc unde goes he p ocess o bene icia ion, whe e
unnecessa y mine als a e emo ed gene a ing a wide ange o po en ially ha m ul byp oduc s.
Discha ges om he indus y o wa e bodies and he soil include acid mine d ainage, oxic
me als and adioac i e elemen s (Pb, Cd, Hg, C , As, U, Th and Ra). These all esul in
signi ican e ec s on ecosys em and human heal h. Dus , luo ide and adon gas emissions
gene a e ai quali y p oblems as well. (Re a e al., 2018)
Comme cially ex ac ed P p ima ily comes om sedimen a y deposi s o apa i e o med in
ma ine en i onmen s o e geological ime. By 2022, he la ges ese es a e concen a ed in
Mo occo (including Wes e n Saha a) and China, which oge he hold app oxima ely 70% o
he wo ld’s P- ich deposi s (Poi ie e al., 2022). This geog aphic concen a ion c ea es
ulne abili ies in he ood sys em, as access o e ilize s is hea ily dependen on geopoli ical
s abili y. Fo example, Mo occo’s con ol o Wes e n Saha a’s phospha e esou ces has spa ked
in e na ional legal and e hical conce ns, wi h claims ha he ex ac ion and ade o phospha es
om he egion iola e in e na ional law. China has imposed high expo a i s o p io i ize
domes ic supply, u he emphasizing he poli ical sensi i i y o P dis ibu ion (Co dell e al.,
2009).
Recen ly, a massi e P deposi o 70 billion ons was disco e ed in No way, po en ially
ex ending he global P supply by 50 yea s a cu en usage a es (Redacció 324, 2023).
Howe e , while his disco e y delays he p edic ed deple ion o P ese es, issues such as
une en global dis ibu ion, pollu ion om excessi e P use, he impac o mining and he non-
enewable na u e o phospha e ock pe sis . These challenges unde sco e he impo ance o
sus ainable P managemen wi hin he amewo k o a ci cula economy.
3.1.4. Phospho us in an ag icul u al con ex
P is o en he limi ing nu ien in e es ial p ima y p oduc ion, playing a c ucial ole in c op
yields and ag icul u al sus ainabili y. C op a ailable P la gely depends on abio ic wea he ing
and bio ic p ocesses, such as oo exuda ions, mic obial ac i i y, pH, i on and aluminium
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con en (Robe s & Johns on, 2015). This a iabili y a ec s he e iciency o e ilize s: due o
immobiliza ion, only 10-20% o applied P is used by plan s he ollowing yea a e applica ion
(Ha a e al., 2010).
The soil su e s P loss h ough c op emo al and abio ic and bio ic wea he ing. His o ically,
na u al p ocesses ha e occasionally p o ided su icien P inpu s o o se losses in a ailable P.
These na u al p ocesses include annual sedimen a ion om looding o olcanic ash ich
wa e s. T adi ional ag icul u e commonly used biological phospha e sou ces such as animal
aeces, c op and o ganic was e o c ushed bones o keep P le els along wi h e osion con ol.
This o ganic P ans o med o Pi h ough mic obial ac i i y in he soil which was boos ed by
biological e iliza ion. By he 19 h and ea ly 20 h cen u ies, phospho us sho ages became a
ecognized limi a ion o ag icul u al p oduc i i y in pa s o Eu ope, he Ame icas, Aus alia,
and Sou he n A ica. This ecogni ion d o e he adop ion o addi ional P sou ces, including
guano and ock phospha es ( ossil phospho i es). (Reijnde s, 2014).
Cu en ly, as seen p e iously, ock phospha es domina e global phospho us supply. The
sus ained use o syn he ic e ilize s and ossil phospho i es, being a d i ing agen o mid-19 h
cen u y “G een e olu ion”, has played a c i ical ole in suppo ing mode n ag icul u al
p oduc i i y and mee ing global ood demands being and will con inue o do so (Ashley e al.,
2011).
Acknowledging he challenges posed by phospho us (P) as a ini e esou ce, including conce ns
o e deple ion and pollu ion, signi ican esea ch e o s o e he pas 30 yea s ha e ocused
on de eloping ecycling and eco e y echniques, pa icula ly in he was ewa e ea men
indus y. These ad ancemen s include me hods such as calcium phospha e p ecipi a ion (Deng
& Dha , 2023), he use o laye ed double hyd oxides coupled wi h biocha (Keyikoglu e al.,
2022), and Fe-based ma e ials (Zhu e al., 2024). Despi e hese de elopmen s, u he esea ch
is equi ed o ad ance low- ech solu ions, such as cons uc ed we lands and il e sys ems, o
make phospho us eco e y mo e accessible and sus ainable (Bi d & D izo, 2009).
3.2. S eel slags
This sec ion explo es he o igin, cha ac e is ics, and po en ial applica ions o s eel slags, wi h
a ocus on hei use as ag icul u al amendmen s. I begins wi h an o e iew o he ypes o
slags p oduced in s eel manu ac u ing and hei composi ion, ollowed by a de ailed discussion
on hei ole as e ilize s. Special a en ion is gi en o hei nu ien p o ile, en i onmen al
impac , and hei po en ial o p omo ing sus ainable ag icul u al p ac ices.
3.2.1. O igin and cha ac e is ics
The e a e commonly h ee slag ypes depending on i s o igins: blas u nace (BF) s eel slag,
i on mel e (IM) slag and he elec ic a c u nace (EAF) s eel slag. (Bi d & D izo, 2009). O
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he h ee, EAF a e mo e e icien in ene gy use when p oducing s eel. Fo his expe imen , EAF
s eel slags we e chosen since i is he mos p e alen s eelmaking p ocess in Spain (70% o all
s eel is p oduced in EAFs) (Ska e al., 2017).
Elec ic a c u nace s eel slags, known in Ca alan as Escò ies Neg es, o igina e om he s eel
p oduc ion p ocess in elec ic a c u naces. The p ima y aw ma e ial used o s eelmaking in
EAFs is s eel sc ap. Du ing he mel ing s age, impu i ies such as manganese and silicon a e
emo ed, esul ing in slags ha accumula e hese impu i ies. Find he slag’s common chemical
composi ion in able 1. (Esco ias Neg as | CEDEX, n.d.).
Table 1. Mos common chemical composi ions o EAF slag in Spain. Sou ce: Ska e al., 2017
This esidue is in cons an abundan supply: in 2017, a o al o 13704000 o o dina y s eel was
p oduced in Spain, which gene a ed 1781560 o slags (110-150kg o slag/ o s eel) (Esco ias
Neg as | CEDEX, n.d.).
They a e commonly e alo ized wi hin he ci il cons uc ion sec o , used as agg ega es in
conc e e o oad cons uc ion. The e alo iza ion o hese slags is a p ocess o e seen by
Di ec i e 2008/98/CE o he Eu opea Pa liamen on esidues ansposed in Spain h ough Ley
22/2011 on esidues and con amina ed soils. Bo h ulings inco po a e he equisi es ha ce ain
ypes o esidues need o mee o ge ou o he esidue s age MITECO, 2023). In 2018, in Spain
only 4% o hese slags ended up in land ills (MITECO, 2023).
3.2.2. Slags as e ilize s
Slags ha e demons a ed signi ican po en ial as soil amendmen s and e ilize s (Das e al.,
2019). Thei cha ac e is ics no only educe he leacha e po en ial o hea y me als and mi iga e
g eenhouse gas (GHG) emissions bu also due o hei composi ion, see able 1, hey p o ide
essen ial nu ien s ha enhance plan de elopmen and mic obial ac i i y (Das e al., 2019;
O’Conno e al., 2021). The alkaline na u e o slags, de i ed om hei calcium and magnesium
oxide con en , inc eases soil pH by eleasing hyd oxide ions (OH⁻) du ing dissolu ion,
e ec i ely mi iga ing soil acidi ica ion. (Das e al., 2019).
These bene i s a e likely due o shi s in mic obial me abolism and modi ica ions in mic obial
habi a s (Das e al., 2019). Al hough no immedia e di ec h ea s o human heal h om slag
applica ion ha e been iden i ied, po en ial isks such as hea y me al con amina ion, leacha e
con amina ion, and bioaccumula ion o hea y me als in plan s emain c i ical conside a ions.
(O’Conno e al., 2021)
Coun ies such as Japan, Ko ea, and China ha e ex ensi ely used s eel-making and blas
u nace slags as aw ma e ials o e ilize s. These e ilize s a e ca ego ized in o slag silica e
19
e ilize s, lime e ilize s, slag phospha e e ilize s, and i on-based e ilize s (Das e al.,
2019). In Eu ope, app oxima ely 2.7% o slags a e cu en ly u ilized as e ilize s. (O’Conno
e al., 2021)
Slags ha e he capaci y o emo e P om aqueous solu ions h ough adso p ion. Thei
e iciency in P emo al depends on he slag’s pa icle size, ini ial P con en and a io o slag
mass o aqueous solu ion olume (Vu e al., 2021). This cha ac e is ic has esul ed in s eel slag
il e echnology eme ging as an e ec i e and low-cos phospho us-adso bing agen . I is
p omising in educing P concen a ions om municipal, domes ic, and ag icul u al was ewa e
(Bi d & D izo, 2009). 1998 he i s ag icul u al ial was conduc ed using BF slags amongs
o he P emo al ma e ials and concluded ha slags showed g ea po en ial as e ilize s.
Following up, in 2009 ano he ag icul u al assay was conduc ed by Bi d & D izo in Vancou e .
They ob ained p omising esul s using P-en iched EAF slags as e ilize s compa ed o s anda d
chemical e ilize s. They u ilized na u ally en iched slags, whe e dai y a m was ewa e was
used o phospha e he slags ins ead o elying on chemical phospho us sou ces. This esul ed
in a mo e ealis ic app oach o P a ailabili y wi hin he slags accoun ing o possible bio ilm
and in e ac ions ha may occu . While his assay p o ided e idence suppo ing he a ailabili y
o phospho us adso bed in slags, a mo e comp ehensi e app oach ha inco po a es soil and
plan quali y indica o s is needed o ad ance owa ds i s scaling up in a con ex o egene a i e
ag icul u e.
3.3. Mic obial ac i i y and egene a i e ag icul u e
Mic obial ac i i y in soil encompasses he di e se a ay o biochemical p ocesses acili a ed
by soil mic oo ganisms (Collins English Dic iona y). These p ocesses a e d i en by bac e ia,
ungi, ac inomyce es, p o ozoa, and o he mic oo ganisms ha in e ac o decompose o ganic
ma e and ecycle essen ial nu ien s o plan g ow h. They pa icipa e in nu ien ixa ion and
solubiliza ion, assis in s ess managemen , p oduce phy oho mones, and posi i ely in luence
plan phenology and c op yield. Addi ionally, soil mic oo ganisms a e ins umen al in o ming
soil agg ega es, which imp o e soil s uc u e, s abili y, wa e e en ion, and ai ci cula ion.
Fu he mo e, mic oo ganisms acili a e eco- iendly ag icul u al p ac ices such as
bio emedia ion and he biocon ol o phy opa hogens. The di e si y o mic oo ganisms is
undamen al o main aining soil heal h and quali y, as di e en g oups o mic oo ganisms
con ibu e o i al soil p ocesses (Nazi e al., 2024). Fac o s such as soil acidi y and nu ien
le els signi ican ly in luence he di e si y and ac i i y o hese mic oo ganisms. (Nada ajah &
Abdul Rahman, 2023; P asha & Shah, 2016)
As a esul , soil mic oo ganisms ha e been widely accep ed as bioindica o s o soil heal h and
ac i i y, p o iding a angible measu e o he soil’s biological i ali y and ecological s a us. This
20
app oach is aken pa icula ly by egene a i e ag icul u e. Which is widely ecognized as a
collec ion o na u e- iendly a ming p ac ices designed o e i alize soil heal h. These
p ac ices include no- ill a ming, co e c opping, c op o a ion, ag o o es y, and he use o
o ganic, home- o a m-based inpu s.
Chemical e ilize s and pes icides a e o en conside ed essen ial o indus ial ag icul u e and
global ood secu i y. Howe e , hey a e associa ed wi h signi ican en i onmen al and heal h
impac s, pa icula ly hei ole in he eu ophica ion o wa e bodies. Acco ding o he Uni ed
Na ions En i onmen al P o ec ion, app oxima ely 30–40% o lakes and ese oi s wo ldwide
a e a ec ed by eu ophica ion o a ying deg ees. This p ocess es ic s he use o wa e o
ishe ies, ec ea ion, indus y, and d inking due o he excessi e g ow h o undesi able algae
and aqua ic weeds, as well as oxygen deple ion caused by hei decomposi ion. Pe iodic su ace
blooms o cyanobac e ia in d inking wa e supplies pose se ious heal h isks (M. N. Khan &
Mohammad, 2014). Addi ionally, chemical inpu s h ough e ililze al e he mic obial
p ope ies o soil, o en educing mic obial di e si y and ac i i y. These challenges highligh
he u gen need o ansi ion owa d sus ainable ag icul u al p ac ices ha p io i ize soil heal h
and enhance mic obial i ali y (P asha & Shah, 2016).
3.4. Me als and hea y me als o in e es
This sec ion p o ides an o e iew o he key me als and hea y me als ele an o his s udy,
ocusing on hei ole in ag icul u al sys ems, po en ial isks, and h esholds o en i onmen al
and human heal h. I discusses essen ial mic onu ien s alongside po en ially ha m ul elemen s.
Addi ionally, he egula o y limi s o hese me als in soil and wa e a e examined o
con ex ualize hei p esence in he slag amendmen s and hei implica ions o sus ainabili y
and sa e y.
The lis o me als e e ed o in his epo a e decided based on he c i e ium s ablished by
Di ec i e 2003/33/EC on limi concen a ions o leacha e on ine ma e ials. These me als a e:
Zinc (Zn), Ba ium (Ba), Nickel (Ni), Selenium (Se), Coppe (Cu), Molybdenum (Mo), A senic
(As), Vanadium (V), Ch omium (C ), Cadmium (Cd), Me cu y (Hg) and Lead (Pb). This lis
includes he me als limi ed in he Real Dec e o 1051/2022, 2022 o Spain ega ding he
maximum con en o me als ha can be used in ag a ian soil. This con i ms he ele ance o
his lis wi hin he scope o he s udy.
The lis includes essen ial mic onu ien s (Zn, Cu, Mo, Ni) and po en ially ha m ul me als (Cd,
Pb, As, Hg and C ). Mic onu ien s a e essen ial elemen s ha main ain plan s’ o e all heal h
by being ins umen al in hei g ow h, de elopmen , and ep oduc ion. They a e equi ed in
minimal quan i ies. Thei le els need o be moni o ed o ensu e hey a e wi hin a ole able and
bene icial ange. (Ahmed e al., 2024)
21
The con amina ion o ag icul u al soils by hea y me als is a majo d i e o soil deg ada ion
(Vácha, 2021). When hea y me als accumula e o oxic le els, hese non-biodeg adable
elemen s ad e sely impac c op heal h and p oduc i i y. They can dis up he no mal s uc u e
and unc ion o cellula componen s in plan s, in e e ing wi h me abolic and de elopmen al
p ocesses essen ial o g ow h and p oduc i i y (Rashid e al., 2023). They also ha e a
signi ican e ec on human heal h. Hea y me als ha e he abili y o cause memb ane and DNA
damage, impai ing p o ein p oduc ion and al e ing hei unc ions including enzyma ic ac i i y.
Thei e ec s can include, amongs o he s, he impai men o kidney unc ion, in e ili y,
dis u bance o de elopmen , inc ease he isk o ca dio ascula disease.(Wi kowska e al.,
2021)
Table 2. Collec ion o uppe limi s o ecommended in akes o he selec ed lis o me als o wa e and ood
consump ion. Sou ce: Eu opean Commission, 2023; Ins i u e o Medicine, US, 1997-2011, WHO, 2022. Excep
o :
*Fo Ba, he alue shown is he no obse ed ad e se e ec le el (NOAEL), es ablished a 0.21 mg/kg body weigh
o an a e age bodyweigh o 70kg. Sou ce: (Choudhu y & Ca y, 2001).
** This alue was no ound on he WHO limi s, i was ound a (EPA, 2000)
Me al
Maximum le els in
ood
[mg/kg we weigh ]
(Eu opean Commission,
2023)
Die a y Re e ence
In akes pe day
[mg/day]
(Ins i u e o Medicine,
US, 1997-2011)
Tole able Uppe
In ake
[mg/day]
(Ins i u e o Medicine,
US, 1997-2011)
WHO d inking wa e
guidelines [mg/L]
(WHO, 2022)
Zn
-
8 o women / 11
o men
40
No heal h guideline,
>4mg/L esul in
as ingen as e
Ba
-
1.4 *
-
1.3
Ni
-
1
0.07
Se
-
0.055
0.4
0.04
Cu
-
0.9
10
2
Mo
-
0.045
2
0.07
As
Ranges om 0.1 o
0.3 o ce eal based
p oduc s
-
-
0.01
V
-
-
1.8
0.23* *
C
-
0.025 o women/
0.035 o men
-
0.05
Cd
0.2 o esh he bs
-
3
Hg
No in o ma ion on
ege ables. Ranges
om 0.1-1 on
sea ood.
-
-
0.006
Pb
0.3 o lea y b assica
-
-
0.01
22
The oxici y o c ops is in luenced by se e al ac o s, including c op ype, g ow h condi ions,
de elopmen al s age, and he speci ic oxic p ope ies o he me als in ol ed. Addi ionally, he
physical and chemical p ope ies o he soil, he bioa ailabili y o he me al ions in he soil
solu ion, and hizosphe e chemis y play c i ical oles in de e mining he ex en o hei impac .
(Rashid e al., 2023)
In e na ional o ganiza ions like he Wo ld Heal h O ganiza ion o he Eu opean Commission
se h esholds and limi s on ega ds o human and en i onmen al heal h on hese elemen s. In
able 2, we collec ed he limi s/ ecommended in akes o he elemen s moni o ed in his s udy
ha applied o d inking wa e and ood consump ion. These limi s will be used as e e ence
alues in his s udy o assess and p ope ly unde s and he dange associa ed wi h slags and hei
po en ial leacha es.
Add essing and moni o ing hea y me al con amina ion is he e o e essen ial o main aining
soil heal h, suppo ing sus ainable ag icul u al p ac ices, and p o ec ing en i onmen al and
human heal h.
23
4. Ma e ials and me hodology
4.1. Expe imen al design
To e alua e he po en ial o phospho us (P)-en iched s eel slags as e ilize s, an 8-week
expe imen was conduc ed using 20 basil plan s (Ocimum basilicum). The expe imen spanned
a o al o 57 days (8.14 weeks), which, based on p e ious ag icul u al s udies in ol ing basil,
is conside ed su icien o assess he impac o ea men s on plan de elopmen and g ow h
(Ál a ez-González e al., 2022; Bi d & D izo, 2009). This ime ame allowed o he
obse a ion o key g ow h s ages and p o ided eliable da a on he e ec s o phospho us-
en iched slag amendmen s.
Fi e expe imen al condi ion g oups we e es ablished, as ollows:
1. Nega i e con ol [C-/1]: Basil g ow h e alua ion unde nu ien -de icien soil
condi ions. Wa e ed wi h ab wa e .
2. Posi i e con ol [C+/2]: Basil g ow h e alua ion unde he applica ion o a s anda d
Hoagland liquid solu ion.
3. Amended condi ion 1 [E/3]: Amendmen wi h P-en iched slag equi alen o he amoun
o P dosed ia he Hoagland solu ion.
4. Amended condi ion 2 [E10/4]: Amendmen wi h P-en iched slag equi alen o 10 imes
he amoun o P in he Hoagland solu ion.
5. Amended condi ion 3 [E20/3]: Amendmen wi h P-en iched slag equi alen o 20 imes
he amoun o P in he Hoagland solu ion.
The posi i e and nega i e con ol g oups we e necessa y o main ain a e e ence poin
h oughou he expe imen . The amended g oups a di e en concen a ions o slags we e
s udied o see he po en ial bene i s o dange s o slags a di e en concen a ions and assess
he bioa ailabili y o adso bed P a di e en concen a ions.
Each condi ion consis ed o ou eplica es a anged in a andom dis ibu ion. The expe imen al
layou was o a ed e e y 2.5 weeks o minimize posi ional bias. Du ing he expe imen , soil
mic obial ac i i y, plan heigh , and chlo ophyll con en o lea es we e moni o ed. A he end
o he expe imen , abo e-g ound and below-g ound biomass we e measu ed. Biweekly wa e
po e wa e samples we e collec ed o assess po en ial me al leaching.
4.1.1. Replicas and amendmen s
The amoun o slag was de e mined based on he phospho us demand o basil plan s. Following
he ecommenda ions o Ál a ez (2022), he basil plan weekly P p o ided was o 3.09mg. This
esul ed in a o al o 24.78 mg by he end o he expe imen (8 weeks). Fo C+ g oup, P was
24
weekly p o ided by he Hoagland solu ion. Fo he slag-amended condi ions, he o al P added
a he s a was adjus ed as ollows:
• E: Equi alen o he P dosed weekly by he Hoagland solu ion.
• E10: Equi alen o 10 imes he weekly P dose.
• E20: Equi alen o 20 imes he weekly P dose.
Using a known concen a ion o 1.09 mgP/g slag and he o al P demand o 24.78 mg, he
equi ed amoun o slag was calcula ed and ounded o he nea es mul iple o i e o accoun
o he limi a ions o p ecision balances a his weigh ange. The olumes o he soil mix u e
we e adjus ed o ensu e consis en po olumes o app oxima ely 0.9 L. See Table 3 o he
composi ion o each expe imen al condi ion.
Table 3. Composi ion o he soil in he di e en amended soils.
Expe imen al
Condi ion
Subs a e (Pea moss + Pe li e)
[g]
Slag
[g]
Slag % o o al weigh
C-
350
0
0%
C+
350
0
0%
E
350
25
6.67%
E10
310
250
44.64%
E20
260
500
65.79%
4.1.2. Expe imen al se up and conside a ions
The expe imen al se up consis ed o i e ows o ou po s, each 1 L in olume, placed unde
ou ans e sal 250V LED ligh s a 55 cm om he g ound, see Figu e 1. One seedling was
plan ed in each indi idual po . Each po had a Rhizon sample inse ed o po e wa e
ex ac ion. The a angemen was o a ed wice du ing he expe imen o ensu e uni o m ligh
exposu e. In o de o ge a homogeneous mois u e and equal olume o soil in o he di e en
expe imen al condi ions, he soil and slags we e p e iously sa u a ed in wa e .
25
Figu e 1. Expe imen se up.
4.1.3. Ma e ials and p oceedings
4.1.3.1. Basil
Culina y he b O. Basilicum is commonly e e ed o as swee basil o basil. I is na i e o Asia
and A ica, bu is cul i a ed wo ldwide. Basil is conside ed low main enance g owing well
indoo s and ou doo s unde sunny and mois condi ions (Li & Chang, 2016).
The basil plan s used in he expe imen we e as seedlings, in he same s age o de elopmen .
Th ee s emmed plan s we e chosen o ensu e maximum homogenei y.
4.1.3.2. Soil
The subs a e used was a 1:1 mix u e o pea moss and pe li e, selec ed o i s nu ien -poo
cha ac e is ics o isola e nu ien in ake om e ilize s and slags. An ini ial analysis o he pea
moss con i med i s low nu ien a ailabili y, see able 4.
Pea moss is an o ganic ma e ial o med om pa ially decomposed sphagnum moss and o he
ege a ion in wa e logged, anae obic (low oxygen) condi ions o e housands o yea s. I is
p ima ily ha es ed om pea bogs in egions such as Canada, No he n Eu ope, and Russia.
I s unique p ope ies make i a widely used subs a e in ho icul u e and ag icul u al
expe imen s.
One o he de ining ea u es o pea moss is i s wa e e en ion capaci y, as i can hold up o 20
imes i s weigh in wa e . I has a signi ican ly low pH, anging 3-4. This p ope y ensu es a
32
The samples we e sen d y a he analysing acili y Eu o ins, Lleida. To ob ain enough biomass,
all he abo e and below biomass o he plan s wi hin he same expe imen al condi ions we e
joined oge he .
4.2.2. Soil heal h
Soil is cons i u ed by solid, liquid and gaseous phases. Wa e and ai quali y a e de e mined by
hei deg ee o pollu ion and he esul ing impac on heal h and ecosys ems (Bünemann e al.,
2018). Howe e , soil quali y is de ined much mo e b oadly as “ he capaci y o soil o unc ion
as a i al li ing sys em, wi hin ecosys em and land-use bounda ies, o sus ain plan and animal
p oduc i i y, main ain o enhance wa e and ai quali y, and p omo e plan and animal heal h”
(Do an & Zeiss, 2000). As such, h ee a iables ha e been s udied in his expe imen o gi e a
wholis ic app oach o assessing soil quali y: a bio ic indica o (mic obial ac i i y), he quali y
o i s liquid phase (assessing po e wa e me al con en ) and he e olu ion o he nu ien
composi ion and physical p ope ies o he soil.
4.2.2.1. Mic obial ac i i y
E e y wo weeks, mic obial ac i i y was assessed using an ATP (adenosine iphospha e)
hyd olysis es . A small soil sample, app oxima ely 0.25 g, was collec ed om he su ace o a
dep h o a ound 3 cm and wi hin a adius o 3 cm om he plan s em. The ATP me hod is a
well-es ablished echnique o quan i ying mic obial ac i i y in soil. ATP, he uni e sal ene gy
molecule p esen in all li ing cells, se es as an indica o o mic obial me abolic ac i i y. The
analysis u ilized a bioluminescence assay in which ATP, ex ac ed using speci ic chemical
eagen s, eac s wi h he enzyme luci e ase o p oduce ligh . The in ensi y o he emi ed ligh
is di ec ly p opo ional o he ATP concen a ion, p o iding a p ecise measu emen o
mic obial ac i i y in he soil samples.
In he p esen expe imen , he LuminUl a ATP es ing ki , see igu e 8, was used. I p o ided
he ollowing p o ocol o he analysis o solid samples:
1. Sampling and ex ac ion o ATP:
• Take 0.25 g o subs a e and place in a ube con aining Ul aLyse ATP ex ac ing
eagen .
• Shake igo ously du ing 5 minu es.
• A e shaking, ex ac 1 mL o he solu ion and ans e o a dilu ion ube.
2. ATP measu emen :
• Place 100 µL o he dilu ed solu ion in a specialized essel.
• Add 100 µL o Luminase o e eal he p esence o ATP.
• S a he me e and wai o he ATP eading.
33
The blank is made wi h a eagen - ee solu ion o se e as a esul con ol which is exp essed
in RLU (Rela i e Ligh Uni s). The calcula ion o ATP de e mina ion, p o ided by he
manu ac u e , is as ollows:
𝐴TP(pgATP
g sample)=RLUsample − Backg oundRLU
RLU Luminase ·50000 (pgATP)
mass o sample (g)
Figu e 8. Se up o he analysis o mic obial ac i i y using he ATP ex ac ion me hod.
4.2.2.2. Po e wa e analysis
To ex ac po e wa e om he po s o leacha e analysis, Rhizon sample s we e used. These
ins umen s, p o ided by Rhizosphe e, a e designed o ex ac po e wa e while il e ing i ,
making i sui able o hea y me al es ing. The model used was he MOM sample , which
ea u es a 5 cm memb ane wi h a po e size o 0.15 mic ome e s o il a ion and a o al leng h
o 12 cm. The sample s we e ully inse ed in o he po s o hei o al leng h. Sampling was
pe o med ou imes du ing he expe imen , beginning wo weeks in and subsequen ly e e y
wo weeks.
Fo sample collec ion, 10 ml Lue lock sy inges we e a ached o he Rhizon sample s, and
nega i e p essu e was applied by pulling he sy inge plunge and locking i in place using a
pipe e ip. This se up, see Figu e 9, allowed he po e wa e o be ex ac ed o e nigh . Once
collec ed, he leacha e om all plan s wi hin he same g oup was pooled o ensu e su icien
sample olume o analysis. The samples we e hen sen o he Depa men o Ma e ials Science
and Enginee ing a UPC, whe e hey we e acidi ied and s o ed unde e ige a ion un il hey
34
we e sen o Technologic and Scien i ic Cen es a Uni e si a de Ba celona (CCi UB) o he
me al es ing.
Figu e 9. Rhizon sample s o po e wa e ex ac ion a ached o a lue sy inge.
The objec i e o his was o p ope ly assess whe he he slags we e leaching and in which
concen a ion. Along wi h he me al analysis on he plan ’s biomass, his es allowed us o ge
a comp ehensi e pic u e o how he slags we e a ec ing he en i onmen . Again, he me al lis
included he ollowing: Zn, Ba, Ni, Se, Cu, Mo, As, V, C , Cd, Hg, Pb. Fu he mo e, pH and
conduc i i y we e also es ed. These esul s compa ed o he ini ial leaching analysis o he
slags gi e us in o ma ion on he impac o such slags in ag icul u al condi ions.
4.2.2.3. Soil composi ion and p ope ies
Ini ial and inal soil composi ion analyses we e conduc ed o cha ac e ize he g owing
condi ions o he expe imen ocusing on nu ien a ailabili y. The pa ame e s s udied we e:
humidi y, pH, conduc i i y, Phospho us concen a ion, Po assium, Calcium, Magnesium,
elemen al Ni ogen and elemen al Ca bon. Gi en he alkaline na u e o slags and hei po en ial
leacha e, he moni o ing o pH and elec ic conduc i i y was deemed impo an .
The ini ial es ing was made solely on he pea moss o assess he nu ien con en . The esul s
poin ed o a nu ien -poo soil. This aligned wi h ou objec i es since we needed he e ilize
and he slags o be he sole sou ce o nu ien s.
Fo he inal soil composi ion analysis, he mix u e o pea moss and pe li e was sen o es ing
(a Eu o ins, Lleida) a e unde going a sie ing p ocess in which all slag con en was emo ed.
Since his inal analysis also included he pea moss, he esul s a e no comple ely compa able
wi h he ini ial es ing bu i does allow o a compa ison wi hin expe imen al condi ions.
35
4.2.3. En i onmen al ac o s
4.2.3.1. Soil mois u e
Mois u e is ce ainly a c i ical ac o o plan g ow h. In gene al, a mois u e con en in be ween
20% and 40% is conside ed ideal o mic obial ac i i y and nu ien cycling, as hese condi ions
allow e icien decomposi ion o o ganic ma e by mic obes and inc eased a ailabili y o
nu ien s o plan s (Che linka, 2024).
In his expe imen , a soil mois u e le el o 26% was in ended o be main ained o c ea e a s able
en i onmen conduci e o heal hy plan de elopmen and mic obial p ocesses. This mois u e
con en ep esen s 80% o he ield capaci y o he soil s udied, which was es ablished a 0.325
m3 wa e /m3. Co ec ions had o be made h oughough he expe imen o keep such mois u e
and was no always achie ed in a cons an manne .
Field capaci y e e s o he maximum wa e e en ion capaci y o a subs a e. I ep esen s he
uppe limi o soil mois u e o op imal plan g ow h, p o iding su icien wa e while ensu ing
adequa e ai space o oo espi a ion and mic obial ac i i y. A his s age, soil po es a e illed
o capaci y wi hou being sa u a ed: la ge po es emp y by g a i y, while smalle po es e ain
wa e by capilla y ac ion. This balance enables plan s o ex ac wa e easily, minimizing he
isk o wa e logging ha can ha m oo s and soil mic oo ganisms (ScienceDi ec Topics
O e iew o Field Capaci y, n.d.; Zo a elli e al., 2010). This capaci y a ies acco ding o soil
ex u e and s uc u e. As an example, sandy soils ha e a lowe ield capaci y (0.15 m3 wa e /m3
soil) due o hei la ge po es, which d ain quickly, whe eas clay soils (0.45 m3 wa e /m3 soil),
wi h hei smalle po es, e ain wa e longe .
Plan s we e wa e ed in a ci cula mo ion, o dis ibu e he wa e e enly. This was done biweekly
wi hou excep ion. In o de o keep a a he equalized wa e supply, ini ially all wa e ing was
homogeneous, see Table 7. This ini ial cons an wa e ing was main ained du ing he i s 3
weeks (6 wa e ings) o allow o equal condi ions amongs all expe imen al condi ions.
Table 7. Wa e ing amoun s du ing he i s 3 weeks.
C-
C+
E
E10
E20
Wa e
50 mL
/
/
/
/
P-less Hoagland
/
/
50 mL
50 mL
50 mL
Hoagland
/
50 mL
/
/
/
36
As he expe imen mo ed o wa d, mo e de eloped plan s equi ed mo e wa e han he less
de eloped ones. We conside ed his a disad an age ha was limi ing g ow h. The e o e, we
added an addi ional wa e supply in p opo ion o he soil’s mois u e. This soil mois u e con en
was moni o ed a he ime o wa e ing using mois u e p obes. The mois u e gene a ed by he
addi ion o he 50 mL o e ilize was de e mined. This p opo ion o mL added o he inc ease
o mois u e le els was measu ed and calib a ed h oughou he expe imen . This a io will be
e e ed o as mL:mois u e. Fo all wa e ings, all po s excep hose in he C- g oup, ecei ed
50 mL o e ilize plus an addi ional wa e supply. In o de o calcula e in a easonable manne
his addi ional wa e supply, he mois u e o each po was measu ed. Then, using he
mL:mois u e a io he amoun o ex a wa e o be added was measu ed:
(Wd – W ) · mL:mois u e= Addi ional wa e
Wd e e s o he desi ed mois u e con en , 26%
W e e s o he mois u e measu ed a he ime o wa e ing
mL:mois u e e e s o he a io ound be ween mL o wa e added and mois u e inc ease
4.2.3.2. Ligh exposu e
The ial was conduc ed unde a i icial ligh ing wi h a ligh :da k cycle o 16h:8h. This
p opo ion is mos ep esen a i e o la e sp ing o ea ly summe in Ba celona hough i sligh ly
exagge a es na u al summe dayligh hou s o p omo e plan g ow h in con olled expe imen al
se ings. 250 V LED ligh s we e used o p o ide con olled and consis en ligh exposu e and
o hei ene gy e iciency and du abili y, see Figu e 10.
Ligh exposu e plays a c i ical ole in plan g ow h and de elopmen , se ing as he p ima y
ene gy sou ce o pho osyn hesis. Pho osyn he ically Ac i e Radia ion (PAR), he ange o
ligh wa eleng hs be ween 400–700 nm, is i al o his p ocess as i d i es he con e sion o
ligh ene gy in o chemical ene gy. (Lee e al., 2023)
Figu e 10.LED ligh s used.
Ligh in ensi y was measu ed using a pho on me e . Ini ial measu emen s e ealed
he e ogenei y in ligh dis ibu ion, wi h plan s a he cen e o he se up ecei ing highe ligh
37
in ensi ies compa ed o hose a he edges, see igu e 11. To add ess his, a o a ion schedule
was implemen ed o compensa e o une en ligh exposu e. Plan s we e ea anged
app oxima ely e e y 2.5 weeks, ensu ing ha each plan expe ienced bo h high and low ligh
condi ions o e he cou se o he expe imen . The o a ion s a egy in ol ed a andomized
ini ial dis ibu ion ollowed by sys ema ic eassignmen s o balance ligh exposu e ac oss all
ea men s.
Figu e 11. Ligh in ensi y dis ibu ion [Klux]. Each cell o he igu e ep esen s a po posi ion wi hin he
expe imen al se -up.
Th ee di e en ligh dis ibu ion pa e ns we e adop ed du ing he expe imen o add ess he
obse ed he e ogenei y (see Figu e 12). This app oach was c i ical o minimize a iabili y in
ligh exposu e, which could in luence pho osyn he ic e iciency and, consequen ly, plan
g ow h. Addi ionally, da a collec ed using he pho on me e allowed o p ecise moni o ing and
alida ion o he adjus men s made.
While i was no easible o achie e comple ely uni o m ligh exposu e, he compensa o y
o a ions ensu ed ha ligh a ailabili y was no a con ounding a iable in he compa a i e
analysis o ea men s. Fu u e i e a ions o his expe imen could explo e u he e inemen s
in ligh se up, such as he use o di used ligh ing sys ems o supplemen a y side ligh ing, o
educe ligh in ensi y dispa i ies.
Figu e 12. Dis ibu ions used h oughou he expe imen . The colou e e s o he expe imen al condi ion: blue
(C-), pink (C+), g een (Esc), o ange (Esc 10) and yellow (Esc20). The numbe s e e o he speci ic eplica
wi hin he expe imen al condi ion (1-4).
38
5. Resul s
To assess he impac o he ea men s on basil c ops compa ed o he con ols, his sec ion
p o ides an in-dep h discussion o he moni o ed a iables h oughou he expe imen . The
analysis is di ided in o h ee ca ego ies: plan heal h and g ow h, soil heal h, and me al
pollu ion in he plan s and leacha e. Fo p ac icali y, he e m "posi i e condi ions" will e e
o C+, E, E10, and E20. Annex I p o ides images o he inal s a e o he basil plan s o suppo
he indings.
5.1. Plan heal h and g ow h
Chlo ophyll
The da a ep esen ed in igu e 13 ep esen s he a e age chlo ophyll con en o he di e en
expe imen al condi ions (C-, C+, E, E10, E20). The uni s used a e SPAD me e eadings, which
would equi e calib a ion o quan i y o al chlo ophyll. Howe e , o he pu poses o his
expe imen , ela i e compa isons a e su icien . As a gene al end, all posi i e condi ions had
a chlo ophyll peak ea ly in he expe imen (week 2 and 3) and all excep condi ion E inished
he expe imen in a nega i e end. Since all expe imen al condi ions lowe ed a a ound week
7 and 8 a na u al decline was expec ed.
Condi ion C- seems o ha e a a he cons an declining end while also showing he lowes
chlo ophyll con en . This esul is consis en wi h i s expe imen al condi ion, in nu ien
de icien plan s chlo ophyll con en is nega i ely a ec ed. The posi i e con ol, C+, peaked a
week 3 and showed a cons an beha iou un il he lowe ing pe iod.
All h ee amended condi ions – E, E10 and E20- peaked a week 2. E hen s abilized o he
du a ion o he expe imen . E10 and E20 luc ua ed signi ican ly. This beha iou could be
cohe en wi h di e en P- eleasing a es o he slags. Since each plan had di e en wa e ing
amoun s in p opo ion o i s de elopmen his could ha e esul ed in di e en geochemical
condi ions in he soil which could p oduce une en elease o P. I is impo an o no e ha C+
ecei ed a weekly phospho us con ibu ion, whe eas E, E10, and E20 had hei en i e
phospho us con en applied o he soil a he s a . This di e ence may explain he consis en
pe o mance obse ed in C+.
A weeks 6 and 7, be o e and he ini ial s ages o lowe ing, he e was no signi ican di e ence
amongs posi i e condi ions: E20 showed he highes esul s while E showed he lowes . The
inal measu emen showed signi ican di e ences amongs posi i e condi ions: E showed he
highes chlo ophyll con en and E10 he lowes . This could be a consequence o di e en
lowe ing a es o di e en g owing a es ha would ha e esul ed in as e nu ien deple ion.
39
Figu e 13. Chlo ophyll eadings pe en i onmen al condi ion h ough ime.
When ac o ing in a iabili y, see able 8, we see ha he nega i e con ol, C-, shows he lowes
a iabili y h ough ime. Condi ion E is he amended condi ion wi h he lowes a iabili y while
he posi i e con ol, C+, shows he highes . All posi i e condi ions ha e a simila a e age
chlo ophyll con en , e lec ing o e all equal heal h.
Table 8. A e age chlo ophyll eadings h oughou he du a ion o he expe imen pe expe imen al condi ion
and s anda d de ia ion.
A e age
chlo ophyll
con en
S anda d
De ia ion
C-
29.1
2.81
C+
37.3
4.50
E
36.13
3.01
E10
35.05
4.34
E20
36.58
4.24
20
25
30
35
40
45
SPAD eading ( ela i e o chlo ophyll con en )
C- C+ E E10 E20
Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Week 7 Week 8
40
Plan heigh
To u he in es iga e plan de elopmen , g ow h was moni o ed o e ime, see Figu e 14. As
p e iously explained heigh is no a p ope assessmen o a plan ’s g ow h i lacks dimensions,
so his in o ma ion will be used o assess g ow h a es and will be co ec ed wi h in o ma ion
on inal biomass.
As expec ed, C- exhibi ed he leas g ow h, consis en wi h i s nu ien -de icien condi ion. All
posi i e condi ions showed signi ican g ow h s a ing om week 2. E10 began o ou pe o m
he o he g oups by week 3 and main ained i s lead h ough he du a ion o he expe imen . The
amended condi ion E, which con ained he same amoun o phospho us as C+, and E20
demons a ed simila g ow h a es o C+.
Figu e 14. Plan heigh a e age eadings pe en i onmen al condi ion in ime.
Table 9 shows he a e age ini ial and inal plan leng h alues pe expe imen al condi ion and
he s anda d de ia ion. Fo he posi i e con ol, C+, he s anda d de ia ion is 9.12cm, 17.05%
o he inal leng h alue. The e o e, his de ia ion is conside ed signi ican and challenges he
compa abili y o he esul s. This sugges s ha , unde con ol condi ions, indi idual plan s
exhibi ed di e en g ow h a es, possibly due o inhe en gene ic di e ences o mic o-
en i onmen al a ia ions wi hin he expe imen al se up.
Expe imen al condi ion E10 was no only e ec i e, as seen p e iously, bu also a ou ed a
a he uni o m plan g ow h. The o he amended g oups, E and E20, showed e en mo e
uni o mi y. Lowe a iabili y sugges s ha hese condi ions p o ided a mo e s able and
consis en en i onmen .
0
10
20
30
40
50
60
70
Heigh [cm]
C- C+ E E10 E20
Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Week 7 Week 8
41
Table 9. Plan heigh a e age ini ial and inal eadings and hei s anda d de ia ion pe en i onmen al condi ion
Ini ial leng h (cm)
Final leng h (cm)
AVG
SD
AVG
SD
C-
2.68
0.30
9.45
4.19
C+
2.35
0.24
53.50
9.12
E
2.70
0.10
47.75
2.36
E10
2.80
0.26
58.88
3.33
E20
2.40
0.15
56.75
2.63
Abo e and below g ound biomass
Complemen ing wi h in o ma ion wi h he inal biomass is c ucial as heigh is an insu icien
indica o o a plan ’s igou . See igu e 15 o he a e age and s anda d de ia ion o he inal
abo e g ound esh weigh o each expe imen al condi ion and i s mois u e con en .
Consis en wi h i s heigh , C- exhibi ed he lowes biomass, e lec ing i s nu ien -de icien
condi ion. E10 main ained i s supe io pe o mance, p oducing 7.66% mo e biomass han he
unne up, C+. Howe e , E displayed p opo ionally less biomass ela i e o i s heigh ,
highligh ing he impo ance o measu ing biomass o gain a mo e comp ehensi e
unde s anding o plan de elopmen . E’s pe o mance indica es ha , al hough he phospho us
p o ided by he slag suppo ed plan g ow h, i was signi ican ly less e ec i e han he s anda d
e ilize alone.
Amongs he posi i e condi ions, E10 ollowed by E20 demons a ed he highes uni o mi y
among indi idual plan s, while E exhibi ed he lowes . In e es ingly, C+ showed g ea e
consis ency in biomass compa ed o i s a iabili y in heigh .
Mois u e con en emained consis en ac oss all posi i e condi ions, a e aging app oxima ely
85%.
48
Following up wi h he plan ’s me al con en . The analysis ga e he esul s in mg o me al pe
kg o d y weigh , o easily compa e wi h he Eu opean Union’s maximum me al con en in ood
and knowing ha all expe imen al g oups showed a a he cons an mois u e con en , hese
esul s we e con e ed o mg o me al pe kg o we weigh . In Table 12 highligh ed in ligh
ed a e he alues ha su pass he e e ence alues; howe e , his ma king is in lamma o y
because he s ablished se ing size o basil plan s is a a ound 5 lea es o 2.5 g ams/day, a
om 1kg. Taking his in o accoun , all he esul s a e wi hin accep able alues o daily in ake
and a om he maximum ole able amoun .
Table 12. Me al concen a ion wi hin plan issue compa ed o maximum and e e ence in akes o he s udied
me als (Sou ce in able 2). In bold he maximum alues. Highligh ed in ligh ed he alues ha su pass he
e e ence alues.
Su p isingly, he mos amoun o maximum alues we e ound in C- plan s. The me al alues
a e exp essed in e ms o concen a ion. C- plan s we e he ones wi h he leas amoun o mass,
he e o e he ini ial alues o essen ial nu ien s ha e no dilu ed in o a la ge biomass as may
ha e happened wi h he o he g oups. Table 13 shows he o al amoun o each me al pe g oup.
This has been achie ed by mul iplying he concen a ion by he a e age biomass o he
expe imen al condi ion. This able e eals ha indeed he o al amoun s o each elemen a e
much g ea e in he posi i e condi ions compa ed o he nega i e con ol.
49
The concen a ion o Zn ollows a dec easing end when compa ed o he amoun o slags
amended. Heal hie plan s a e associa ed wi h g ea e concen a ion o Zn, de iciency could
ela e o damage o oo s o poo i iga ion p ac ices, nei he o which ha e been obse ed in
he p esen expe imen . Fu he es ing would be necessa y o de e mine he eason o his. Ni
and Pb a e p esen in all condi ions, highly concen a ed in C-. This indica es ha hey we e
p obably p esen in he soil used. Slag induced me als - Ba, Mo and V - a e in highe
concen a ions in E20, as expec ed. Dis ega ding C- concen a ions, hese me als showed
p opo ionali y wi h he amoun o slag.
Compa ing wi h he po e wa e esul s we ind some di e ences. Se, As and C we e no p esen
in he po ’s leacha e bu we e ound in plan s om all g oups. Se is no essen ial o plan
g ow h bu can be bene icial, howe e , As and C a e pollu an s and should no ha e been
p esen wi hin he plan . The slag’s leacha e could ha e a small con ibu ion o hei p esence
wi h a 0.01ppm concen a ion o As and 0.03ppm o C . Thei p esence is wi hin heal h limi s
bu hei o igin is unknown and suspec ed o be om he own seedling o he soil.
This e idence indica es ha , al hough he me als leached om he slags emain wi hin
accep able limi s, hey a e s ill abso bed by he plan s. The p esence o me als which we e
di ec ly a ibu ed o he slag amendmen s, unde sco es he need o ca e ul moni o ing and
managemen in u u e applica ions. While he concen a ions obse ed in his s udy comply
wi h sa e y s anda ds, he cumula i e e ec s o long- e m slag use and he po en ial o me al
accumula ion in soil and c ops mus be ca e ully e alua ed.
Table 13. To al me al amoun pe a e age plan o each o he expe imen al condi ions. In bold he maximum
alues.
Elemen
C- [μg]
C+ [μg]
E [μg]
E10 [μg]
E20 [μg]
Zn
300.42
1247.89
1040.17
1099.24
661.99
Ba
12.97
65.83
63.59
233.85
272.39
Ni
1.05
5.74
4.25
7.91
7.14
Se
0.60
4.62
2.56
5.54
5.19
Cu
11.76
38.96
20.39
38.51
37.32
Mo
1.17
7.92
7.17
14.23
15.58
As
0.36
0.66
2.05
2.37
2.60
V
0.70
3.50
3.18
13.92
17.39
C
0.85
7.00
5.33
8.46
6.81
Cd
0.32
0.73
0.72
0.71
0.45
Pb
0.70
5.15
2.66
5.85
4.93
50
6. Conclusions
The indings o his s udy con i m ha en iched slags can se e as sus ainable, cos -e ec i e,
and egene a i e e ilize s by p o iding bioa ailable phospho us. Among he expe imen al
condi ions, E10 consis en ly ou pe o med he o he g oups ac oss nea ly all moni o ed
a iables, including plan heigh , abo e- and below-g ound biomass, oo leng h, and
mic obial ac i i y, while main aining high uni o mi y among indi idual plan s. The C+
g oup gene ally exceeded he pe o mance o he E g oup, indica ing ha no all phospho us
adso bed by he slag becomes bioa ailable. E10, which con ained en imes he phospho us
p o ided o C+, showed sligh ly be e esul s han C+, indica ing ha sligh ly mo e han
10% o he phospho us adso bed by he slags became bioa ailable.
The esul s on mic obial ac i i y indica e ha slags ha e no nega i e impac on i s
de elopmen , demons a ing hei compa ibili y wi h soil ecosys ems. Al hough he high
a iabili y in he esul s limi s he abili y o make p ecise compa isons be ween condi ions,
E10 exhibi ed he mos a o able esul s wi h 26.52% mo e ac i i y han C+. These indings
highligh he ecological compa ibili y o phospho us-en iched slags as a po en ial soil
amendmen , as hey suppo mic obial heal h while p o iding bioa ailable nu ien s.
The moni o ing o me al leaching om he slags has conclusi ely demons a ed hei sa e y
o bo h human and ecosys em heal h. The slag’s leacha e did con ibu e o he p esence o
ce ain me als, especially Ba, Mo and V which we e also abso bed by he plan s. Howe e ,
he concen a ions o hese me als wi hin he plan s and in he soil’s po e wa e we e
consis en ly well below in e na ional e e ence and sa e y h esholds, unde sco ing hei
en i onmen al compa ibili y. These indings p o ide s ong e idence ha phospho us-
en iched slags can be sa ely u ilized as a soil amendmen in ag icul u al p ac ices. Howe e ,
he cumula i e e ec s o long- e m slag use and he po en ial o me al accumula ion in soil
and c ops mus be ca e ully e alua ed.
These indings ha e posi i e social, economic, and en i onmen al impac wi hin he
ag icul u al sec o , hese ideas a e u he de eloped in he addi ional chap e 7.
Sus ainabili y analysis and e hical implica ions. Low-cos il e ing echnologies such as
we lands coupled wi h he P- emo ing quali ies o slags could be used in ag icul u al was e
wa e ea men . This a o dable echnology could b ing empowe men o u al a eas which
would p oduce e ec i e e ilize while keeping nu ien pollu ion con olled and closing he
P cycle locally.
51
6.1. Limi a ions
Du ing he expe imen and he subsequen analysis, se e al limi a ions we e iden i ied,
which p o ide oppo uni ies o e inemen in u u e esea ch. This sec ion highligh s hese
challenges and p oposes ecommenda ions o u he in es iga ion.
One key limi a ion was he wa e ing me hod used in he expe imen . The app oach did no
accoun o a ying wa e consump ion a es among plan s. Mo e de eloped plan s
consumed wa e mo e quickly han less de eloped ones, leading o g ea e a iabili y in soil
mois u e con en . This inconsis ency a ose because all expe imen al condi ions ollowed he
same wa e ing schedule. While his may ha e in luenced g ow h a es, he esul s show ha
he E10 g oup es ablished i s lead by week h ee and main ained i h oughou he
expe imen . The e o e, he e was p obably no impac on he esul s. Howe e , implemen ing
a mo e au oma ed wa e ing sys em, capable o main aining consis en soil mois u e le els,
would ensu e uni o m condi ions o all plan s and yield mo e accu a e esul s.
Budge a y cons ain s also es ic ed he scope o me al es ing. Al hough p omising esul s
we e ob ained, expanding he analysis o include a b oade ange o me als would o e a
mo e comp ehensi e unde s anding o he en i onmen al and ag onomic impac .
Speci ically, u u e esea ch could examine he ollowing elemen s:
• I on: A c ucial mic onu ien o plan s ha signi ican ly in luences mic obial
ac i i y.
• Manganese: P esen in slags, i could posi i ely a ec enzyma ic unc ions i
abso bed by plan s.
• Magnesium and Calcium: Typically ound in slags, hese elemen s imp o e soil
s uc u e and e ili y.
Addi ionally, a mo e de ailed ini ial assessmen o he plan ’s nu ien con en as seedlings
could help cla i y he concen a ion o me als a ea ly de elopmen al s ages. Simila ly, while
he ini ial soil analysis ocused on pea moss o unde s and he nu ien con ex , including an
analysis o he comple e soil-pe li e mix u e would ha e acili a ed a mo e accu a e
compa ison wi h he expe imen al esul s.
6.2. Fu u e lines o esea ch
In ligh o he esul s and he iden i ied limi a ions, u u e i e a ions o his s udy a e
ecommended wi h changing pa ame e s ha could enable mo e p ecise measu emen s and
be e insigh s in o he e iciency and impac o using s eel slags as e ilize s. The ollowing
a eas o in e es ha e been conside ed:
52
• Compa ison o slag ypes: in es iga ing he p ope ies o di e en slag ypes, such
as blas u nace (BF) and induc ion mel ing (IM) slags, could e eal a ia ions in
hei e ec i eness as e ilize s.
• Use o slags om ac ual il e s: acco ding o D izo & Bi d’s assay in 2009, P-
il e ing we lands o en esul in slags being co e ed wi h bio ilms, solids, and
o he deposi s, which may al e hei pe o mance. The p esen s udy simpli ied
he p ocess by using chemically cha ged slags, bu u u e expe imen s should
compa e hese o slags used in eal-wo ld il e s o be e unde s and how hese
condi ions a ec phospho us bioa ailabili y.
• Moni o ing de elopmen s ages: building on he wo k o D izo and Bi d (2009),
u u e esea ch could examine plan de elopmen ac oss di e en g ow h s ages.
Thei indings sugges ed ha EAF s eel slags pe o m be e in he long e m,
equi ing ex ended pe iods o elease phospho us e ec i ely. While his s udy
obse ed consis en pe o mance h oughou he expe imen , u he compa isons
ac oss a ying ha es imes could cla i y hese disc epancies.
• E ec o slag g anulome y: he pa icle size o slags a ec s hei phospho us-
adso bing p ope ies and may in luence phospho us bioa ailabili y. Tes ing slags
wi h a ying pa icle sizes, including c ushed slags, could iden i y he mos
e icien g anulome y o use as e ilize s.
Pu suing he p oposed esea ch di ec ions will p o ide a deepe unde s anding o he
po en ial o s eel slags as sus ainable e ilize s and op imise hei e iciency.
53
7. Sus ainabili y analysis and e hical implica ions
In his sec ion he en i onmen al, economic and social implica ions o he de elopmen
o he hesis as well as i s applica ion will be explo ed, including a e iew on po en ial
isks and he iden i ica ion o he p ojec ’s limi a ions. Unde s anding he in e ac ions and
he cha ac e is ics o he h ee pilla s o sus ainabili y is c ucial in he de elopmen o
new echnologies and se ices.
This analysis is di ided in h ee subsec ions o clea e assessmen : he de elopmen o
he hesis, he po en ial applica ion o he slags and a sec ion dedica ed o he isks and
limi s o his analysis. A sec ion on e hical implica ions and he alignmen wi h he
Sus ainable De elopmen Goals is also p o ided.
7.1. De elopmen o he hesis
7.1.1. En i onmen al pe spec i e
The ul ima e goal o his expe imen lies wi hin ci cula i y: ecycling slag ma e ials as
e ilize s o shu down he phospho us cycle. Howe e , ma e ials, anspo and esou ces
we e needed o pe o m he expe imen and hose ha e ce ain impac in e ms o
emissions. The main p eoccupa ion e ol ing a ound he expe imen was he p esence o
hea y me als, which ha e been ho oughly moni o ed. No dange ous leaching has been
ound a he expe imen ’s condi ions.
Fo he pu pose o his analysis, and gi en he ac ha he expe imen is pa o a la ge
p ojec , bounda ies need o be se . The scope o his analysis s a s wi h he slags (no i s
p oduc ion p ocess), and ends wi h he disman ling o he po expe imen . Fu he mo e,
he analysis ex e nalized a ou side acili ies had an impac beyond ou capabili ies. Mos
o he ma e ial used was al eady in possession o he esea ch g oup o he lab, including
po s, mois u e me e s and LED. In ac , educing he amoun o new ma e ial was always
a p io i y while se ing up he expe imen . Ene gy consump ion was minimized using
LED ligh s, which a e ene gy e icien . Wa e ing was kep o he necessa y amoun o
a oid pe cola ion. He e is a lis o po en ial ca ego ies o impac :
• Resou ces:
o Wa e :
▪ Fo i iga ion: 31.06 L
▪ To clean lab equipmen . We do no ha e he means o es ima e his
alue since his was no moni o ed h oughou he expe imen .
54
o Ene gy:
▪ Ligh ing: LED ligh ing du ing 16 hou s a day o 57 days, esul ing
in a o al o 912 hou s o ligh om he 4 led ans e sal ligh s.
LED consump ion can ange om 10 o 50Wh/hou . To be in he
conse a i e side we will measu e an impac o 50Wh/hou ligh ,
gi ing a o al o 182.4 kWh
• T anspo a ion:
o Slag p oduc ion plan o expe imen al si e (UPC Campus No d): 46 km
o Rhizon sample s we e sen om he Ne he lands. The e was a mis ake
while o de ing so i was e u ned and sen again using exp ess sending.
1500km pe way. 4500km in o al.
o Leacha e samples we e sen o es ing o he Uni e si y o Ba celona
(Cci UB), which is less han 1km om UPC Campus No d. The e o e, we
will neglec his impac .
o Soil and plan analysis we e sen o Eu o ins, Lleida o es ing. 262 km.
o S a anspo o he expe imen al si e (San Cuga o UPC Campus No d
by ain). 13km each way o abou 4 mon hs. An app oxima ed 3224km
in o al.
o The basil seedlings we e picked up a Jo di Plan e s Scp a Viladecans,
Ba celona. 62km.
• Ma e ial:
o The ATP de ec ion ki equi ed he use o single use plas ics. A ough
es ima e o a o al o 800g o single use plas ics we e used.
o The usage o a lap op o he du a ion o he expe imen and he gene a ing
o documen s (4 mon hs o usage).
The p e ious in o ma ion is summa ized in able 14. Using emission ac o s ex ac ed
om a ious sou ces speci ied in he able, a ough es ima e o he o al ca bon oo p in
o he p ojec was gene a ed.
55
Table 14. Ca bon oo p in calcula ion including he in en o y, he alue, he emission ac o used and i s
sou ces and he o al alues.
In en o y Elemen
Co esponding
Value
Emission Fac o
(kg CO2e/uni )
To al
Emissions (kg
CO2e)
Sou ce
Wa e o i iga ion
31.06 L
0.000344
0.01068464
Li ecycle analysis (LCA)
s udies o wa e sys ems
(e.g., IWA)
Ligh ing (LED, 4
ligh s, 912 hou s)
182.4 kWh
0.233
42.4992
Spain lec ici y
g idemission da a (Global
Ca bon A las, REE)
T anspo : Slag
p oduc ion plan o
expe imen al si e
46 km
0.12
5.52
IPCC guidelines o diesel
ehicle emissions
T anspo : Rhizon
sample s
4500 km
0.12
540
IPCC guidelines o eigh
ucks (a e age emission
ac o )
T anspo : S a
commu ing (FGC)
3224 km
0.03
96.72
FGC Ba celona emission
da a (o icial epo s)
T anspo : Soil and
plan analysis (Lleida
o si e, 132 km)
262 km
0.12
31.44
IPCC guidelines o diesel
ehicle emissions
T anspo : Basil plan
pick up a Viladecans
62 km
0.12
7.44
IPCC guidelines o diesel
ehicle emissions
Single-use plas ics
om he ATP ki
800 g
6
4.8
LCA s udies o plas ics
(EPA, Plas ics Eu ope)
Lap op usage
960 hou s
0.05
48
A e age lap op ene gy
consump ion da a (IEA,
LCA s udies)
TOTAL
776.43KgCO2e
56
The esul ing o al impac calcula ed is 776.43 KG o equi alen CO2 o he de elopmen
o his expe imen . Fo e e ence, he a e age Eu opean pe son gene a es 7.25 equi alen
CO2 pe yea (JRC). F om looking a he able, we deduce ha he weak spo o he p ojec
in e ms o sus ainabili y was anspo a ion. Bu aside om he hizon, which we simply
could no ind om local supplie s, he e was an e o o use local es ing acili ies o
educe he en i onmen al and economic cos o he whole p ojec .
These a e he supplie s ha mainly pa icipa ed in he expe imen :
• Celsa o p oduce he slags. On hei websi e (h ps://www.celsag oup.com/) hey
ha e a sec ion on hei en i onmen al commi men , claiming hey a e he leading
s eel company in Eu ope in e ms o ci cula p oduc ion and low emissions. They
ecycle e ous sc aps and u n hem in o s eel. They ha e he goal o become Ne
posi i e in 2050.
• AdecGlobal o he slag’s e alo iza ion. They specialize in e alo izing
cons uc ion esidues in o p oduc s. They a e commi ed o sus ainable
cons uc ion, deca boniza ion and p omo ing a ci cula economy. They comply
wi h he egula ions om he Agència de Residus de Ca alunya. (Find mo e
in o ma ion a : h ps://adecglobal.com/)
• Rhizosphe e Resea ch P oduc s o he Rhizon sample s. No in o ma ion was
ound on he websi e (h ps://www. hizosphe e.com/). Howe e , a e con ac ing
hem, hey assu ed ha al hough hey a e a small company and do no ha e he
means o ex ensi e documen a ion, all Rhizon sample s a e p oduced in-house,
hey minimise was e and p io i ize e-use (e.g. packaging ma e ial) whe e e
possible. They p oduce wi hin Eu ope, he e o e hey comply wi h Eu opean
egula ions.
• LuminUl a o he ATP ki s. On hei websi e hey ha e a sec ion on
en i onmen al compliance (h ps://www.luminul a.com/expo -en i onmen al-
compliance/) whe e hey acknowledge he obliga ion o minimizing he
en i onmen al impac o hei p oduc s. They acili a e he disposal o hei
p oduc s and use en i onmen ally iendly ma e ials.
• Jo di Plan e s Scp o he basil seedlings. No in o ma ion ega ding he
en i onmen al commi men o his endo could be ound.
In summa y, al hough no speci ic en i onmen al epo s could be ound, all he
expe imen ’s supplie s show a commi men owa ds sus ainabili y. In he case o he
slags’ o igins, sus ainabili y and ci cula i y a e he backbone o bo h in ol ed companies.
57
7.1.2. Economic pe spec i e
This expe imen u ned ou o be mo e cos ly han expec ed due o he ex e naliza ion o
samples. Th oughou he p ojec he e was an emphasis on eusing and limi ing he
pu chase o new ma e ial. The human cos was minimal since he p incipal au ho and
execu o o his expe imen was no emune a ed.
The same app oach will be made o he p e ious sec ion. We gene a ed he ollowing lis
o app oxima ed po en ial cos s o he mos ele an i ems.
• Re sou ces:
o Wa e :
▪ Fo i iga ion: 31.06 L. Negligible cos s.
▪ To clean lab equipmen . We do no ha e he means o es ima e his
alue since his was no moni o ed h oughou he expe imen .
o Ene gy:
▪ Ligh ing: 182.4 kWh.
• T anspo :
o By ca (a cu en gasoline a e o 1.4 EUR/L a a 6.5 L consumed pe
100km):
▪ Slag p oduc ion plan o expe imen al si e (UPC Campus No d):
46 km by ca . 4.18 EUR.
▪ The basil seedlings we e picked up a Jo di Plan e s Scp a
Viladecans, Ba celona. 62km in o al. 6.64 EUR.
o Soil and plan analysis we e sen o Eu o ins, Lleida o es ing. 262 km
by anspo a ion se ice. Fee o ap ox 30 EUR.
o Leacha e samples we e sen o he Uni e si y o Ba celona (Cci UB) o
es ing which is less han 1km om UPC Campus No d, we will hen
neglec his impac .
o Rhizon sample s. 4500 km by anspo a ion se ice. Billed 68.35 EUR.
o S a anspo o he expe imen al si e (San Cuga o UPC Campus no d
by ain). 53 EUR co esponding o he ee o 1.33 T-Jo e ca ds.
• Ma e ial:
o Slags: we e p o ided o ee.
o Lab equipmen ( eac i es and ma e ial): his cos was minimal since he
Hoagland solu ion used up e y low concen a ions o i s componen s.
o Rhizon sample s. 150 EUR.
o ATP ki . Fo he amoun used up a ough es ima e o 700 EUR.
64
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ACKNOWLEDGEMENTS
I would like o exp ess my hea el g a i ude o my u o s, Jaume Puigagu and Diego
Apon es, o always inding solu ions o e e y p oblem and o e ing explana ions o e en
he mos unexpec ed esul s. To Rosa Manyosa, my dea es colleague, o he pa ience,
eliabili y, unwa e ing suppo , and all he co ee b eaks ha kep me going h oughou
he expe imen —and so much mo e. To Ma a Fe nández-Ga ell o he kindness,
expe ise, and aluable guidance, and o Emma Goué ec, who accompanied and
suppo ed me h ough he inal s ages o he expe imen . I am also deeply g a e ul o he
en i e GEMMA eam o hei in aluable ad ice, willingness o help, and genuine
cu iosi y.
I ex end my deepes hanks o my pa en s and Nona, who d o e me o he lab when my
leg was b oken and p o ided boundless suppo h oughou his jou ney. Specially my
mom who ead his hesis mo e imes han I did.
Thank you Gu u, my bes iend h ough hick and hin, o making going o uni wo h i
e e y day, o singlehandedly managing Ramoona’s while I was w i ing his hesis, o
endless laugh e , and o e en mo e endless d eams.
Finally, I wan o hank he basil plan s o hei excellen beha io and o p o iding us
wi h such sa is ying esul s.
71
ANNEX I
Figu e 21. Pic u es o he plan s be o e he ha es 06/06/2024.
72
