Maximising bio-oil yield om indus ial dai y sludge: a pa adigm on py olysis
empe a u e and hea ing a e in he con ex o he EU FLEXBY p ojec
L. Taboada-Ruiz, E. Ciu cina, R. Pa do, J. Holgado, P. Ál a ez Rod íguez, M. Díaz-Somoano, B. Ruiz
Ca bon Science and Technology Ins i u e (INCAR), CSIC. C/ F ancisco Pin ado Fe 26, 33011, O iedo, Spain.
Keywo ds: Dai y was e alo iza ion, Con en ional py olysis, Hea y bio-oil, T anspo sec o
P esen ing au ho email: l. abo[email p o ec ed]s
In oduc ion
The dai y indus y p oduces signi ican quan i ies o sludge, which is cha ac e ised by i s high o ganic con en . I
hese by-p oduc s a e no eco e ed, hey a e classi ied as was es and he e o e ha e o be managed as such, which
en ails a numbe o en i onmen al and economic disad an ages. The physical and chemical cha ac e is ics o
biological sludge gene a ed in was ewa e ea men p ocesses depend on he ype o was ewa e ea ed and he
ea men p ocesses employed.
As he wo ld inc easingly ansi ions away om ossil uels, ecycling di e en indus ial esidues in o
bio uels is eme ging as an en i onmen ally and economically sus ainable s a egy. Py olysis, de ined as he p ocess
o he mal decomposi ion o a subs ance in he absence o oxygen, has been ex ensi ely s udied o he pu pose o
con e ing esidue in o bio uels, wi h con en ional py olysis being he mos widely used me hod. Se e al
expe imen al a iables, such as py olysis empe a u e o hea ing a e, play a c ucial ole in de e mining he yield
and quali y o he inal bio uel p oduc s (Kau e al. 2015). Lowe empe a u es end o a o he p oduc ion o
biocha , while highe empe a u es enhance he yield o liquid bio-oil and gas (Vilas-Boas e al. 2021). Slow
py olysis is he mos e ec i e echnology o high-yield biocha p oduc ion, while as py olysis p o ides highe
bio-oil yields, and in e media e py olysis p oduces a balanced dis ibu ion o biocha , bio-oil and gas (S. Sa a ian,
2023). The con e sion o dai y sludge in o bio uels h ough py olysis p ocesses o e s a comp ehensi e alue
p oposi ion o he managemen o such was e, while educing dependence on ossil uels and p omo ing
sus ainable ene gy p ac ices.
The aim o his s udy is o assess he easibili y o using sludge om he dai y indus y o p oduce bio uels
o bioma e ials h ough con en ional py olysis p ocesses, whe e empe a u e and hea ing a e will be he main
pa ame e s o s udy.
Me hodology
The esidue is a biological sludge o a dai y indus y loca ed in he no h o Spain. The company, wi h a
175-yea his o y, specialises in he p oduc ion and ma ke ing o dai y p oduc s. Gi en he indus ial na u e o he
was e, he sludge sample was me iculously collec ed, d ied and p epa ed o a pa icle size ha was sui able o
cha ac e isa ion and py olysis (≤1 mm).
The dai y sludge sample was cha ac e ised o de e mine i s physico-chemical p ope ies and sui abili y
o use in py olysis p ocesses. This was done by s udying i s p oxima e and ul ima e analyses, as well as o he
ele an analyses. The mog a ime ic analysis showed he e olu ion o he sludge esidue wi h empe a u e.
The con en ional py olysis was ca ied ou using a cylind ical, elec ic, ho izon al o en o o iginal design.
The sample (7-8g) was pu in o he o en a oom empe a u e. Ni ogen gas was lowed a 100 ml/min o c ea e an
ine a mosphe e inside he eac o . The u nace was hea ed a di e en speeds (25°C/min o 5°C/min), eaching
di e en py olysis empe a u es be ween 450 and 750°C and he sample was held a he inal empe a u e o one
hou . A e py olysis, bio-cha , bio-oil and gas ac ions we e s udied.
Resul s
The sludge was e has a high ca bon con en o 44.2%. P oxima e analysis showed a mode a e ash con en
(22.6%) in he esidue, which will a ou he p oduc ion o biocha in he py olysis p ocess wi h a composi ion
sui able o al e na i e applica ions ( e ilize s, ac i a ed ca bon p ecu so s). P oxima e analysis also indica ed a
ema kably high ola ile ma e con en (79.8%), which will a o a conside able yield o he liquid and gaseous
ac ions. The chlo ine con en is signi ican ly low (0.052%), indica ing ha he biomass is sui able o i s
applica ion in py olysis, as he isk o co osion du ing he he mal p ocess o he subs ance is minimised. The ash
usibili y analysis p o ides key indings: he ini ial de o ma ion empe a u e is 1336 °C, indica ing ha he ashes
do no de o m un il e y high empe a u es a e eached.
The yield o he solid, liquid and gas
ac ions is con ingen on he expe imen al
condi ions o he py olysis p ocess (i.e.
empe a u e and hea ing a e). Py olysis p ocesses
ha e been ca ied ou a a hea ing a e o 25 °C/min
and a di e en empe a u es (450, 500, 600 and
750) o e i y ha , a low empe a u es, he
majo i y ac ion o bio-oils is ob ained. The bio-
cha , bio-oil and gas yields as a unc ion o
empe a u e can be seen in Fig. 1. Once he op imal
empe a u e o he expe imen had been
es ablished, u he es s we e conduc ed in which
he hea ing a e was modi ied. The esul s indica e
ha , a 500°C, a highe hea ing a e (25°C/min)
a o s a highe yield o he bio-oil ac ion, Fig. 2.
Conclusions
Ul ima e and p oxima e analysis indica es ha
dai y sludge possesses good p ope ies o use in py olysis
p ocesses o p oduce bio uels o bioma e ials. The
Eu opean Flexby P ojec has been concei ed wi h he
objec i e o de eloping hea y bio uels o he anspo
sec o . As pa o he p ojec , he sludge om he dai y
indus y was subjec ed o con en ional py olysis a di e en
expe imen al a iables in o de o op imise he bio-oil yield.
Th ough he s a egic a ia ion o he con en ional
py olysis p ocess pa ame e s ( empe a u e and hea ing
a e), i was de e mined ha low empe a u es (450 and 500
°C) and a mode a e hea ing a e (25 °C/min) yield op imal
bio-oil ac ions, wi h up o 54% yield. These es s ha e
con i med ha he biosludge has he ideal cha ac e is ics o
be ans o med in o a high alue-added p oduc in he
con ex o he ci cula bio-economy.
Acknowledgemen s
The wo k desc ibed in his publica ion was subsidised by Ho izon Eu ope (HORIZON) amewo k
h ough he G an Ag eemen Numbe 101144144. Addi ionally, he au ho s hank o Man eque ías A ias, dai y
indus y, o p o iding he biomass sludge used in his wo k.
Re e encias:
(1) Kau , R.; Ge a, P.; Jha, M. K. S udy on E ec s o Di e en Ope a ing Pa ame e s on he Py olysis o
Biomass: A Re iew. J. Bio uels Bioene gy 2015, 1 (2), 135. h ps://doi.o g/10.5958/2454-
8618.2015.00015.2.
(2) Vilas-Boas, A. C. M.; Ta elho, L. A. C.; Kamali, M.; Hauschild, T.; Pio, D. T.; Jahanian a d, D.; Gomes, A.
P. D.; Ma os, M. A. A. Biocha om Slow Py olysis o Biological Sludge om Was ewa e T ea men :
Cha ac e is ics and E ec as Soil Amendmen . Bio uels Biop od. Bio e ining 2021, 15 (4), 1054–1072.
h ps://doi.o g/10.1002/bbb.2220.
(3) Sa a ian, S. Pe o mance Analysis o Sus ainable Technologies o Biocha P oduc ion: A Comp ehensi e
Re iew. Ene gy Rep. 2023, 9, 4574–4593. h ps://doi.o g/10.1016/j.egy .2023.03.111.
Funded by he Eu opean Union. Views and opinions exp essed a e howe e hose o he
au ho (s) only and do no necessa ily e lec hose o he Eu opean Union o CINEA.
Nei he he Eu opean Union no he g an ing au ho i y can be held esponsible o hem.
Fig. 1. Py olysis ac ion yield. E ec o he empe a u e.
Fig. 2. Py olysis ac ion yield. E ec o he
hea ing a e a 500°C.
