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DOI: 10.5281/zenodo.17285090
O iginal A icle
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ANAEROBIC EXPERIMENTATION TO DETERMINE KEY PARAMETERS FOR
OPTIMAL PERFORMANCE OF A PILOT SCALE BIO-DIGESTER FOR
EMULATING LANDFILL CONDITIONS AND GAS RECOVERY
*Ene iok O. Usungu ua
1
, Akanimo U. Usungu ua
2
, Why e A. Akpan
3
, Aniekan E. Ikpe
4
and Uchechi E.
I oekwe
5
1, 3
Depa men o Mechanical Enginee ing, Fede al Uni e si y o Technology,
Iko Abasi, Nige ia
2
Depa men o Elec ical/Elec onic Enginee ing, Fede al Uni e si y o Technology,
Iko Abasi, Nige ia
4
Depa men o Mechanical Enginee ing, Akwa Ibom S a e Poly echnic, Iko Osu ua,
Iko Ekpene, Nige ia
5
Depa men o Mechanical and Ae ospace Enginee ing, Uni e si y o Uyo, Nige ia
*Co esponding au ho : ene iokusungu [email protected]; eneusungu ua@ u ia.edu.ng
ARTICLE
INFO
ABSTRACT
Pape ID: IJASTR-
68D31DC8D57A8
Recei ed: 2025-09-05
Published: 2025-10-05
DOI:
h ps://dx.doi.o g
/10.5281/zenodo.17
285090
Page No: 257-272
The inc easing popula ion and economic ac i i ies in Nige ia ha e encou aged high
gene a ion o was es as well as high ene gy c isis, esul ing in he con inued use o
ossil uels and inc emen in g eenhouse gases. The e o e, he necessi y o ackle
hese se backs ia biomass land ill biogas p oduc ion, a enewable ene gy sys em
om was es canno be o e emphasized. This s udy examined he op imal anae obic
diges ion p ocesses o a pilo -scale bio-diges e s o emula ing land ill condi ions.
O ganic eeds ock om a ie y o ood was e, cow dung and dis illed wa e we e
collec ed om ca e e ias, es au an s, ho els, and households in Iko Abasi me opolis
and ca le ange in Uyo, Sou h Sou h Nige ia. Seg ega ion, cha ac e iza ion,
homogeniza ion, pa ame ic es s, moni o ing and ex ac ion we e ca ied ou . These
samples we e diges ed using a bio-diges e wi h pa ame ic es ing equipmen .
Di e en masses o eeds ock anging om 10 – 25 kg wi h wo mix a ios o 1:1 and
2:1 each we e employed. F om he esul s, he hyd aulic e en ion ime (HRT)
showed linea i y wi h app oxima ely 0.73 days pe kg, a pH o 6.9 – 7.1 (p e-
diges ion), 6.7 – 6.8 (pos -diges ion) and mesophilic empe a u e o 22–33°C.
Feeds ock o 1:1 a io had gas yield o 12 ml pe kg whe eas 1:2 a io had 11.4 ml
pe kg. Sys em p essu e was espec i ely 0.16 Pa pe day, 0.053 Pa pe kg eeds ock
and 0.174 Pa pe day, oughly 0.058 Pa pe kg eeds ock. I can be concluded ha a
posi i e co ela ion exis s be ween eeds ock mass and biogas yield wi h 1:1 a io
ha ing a consis en ad an age o 21-27% gas yield o e he 2:1 a io. The pilo -scale
expe imen s also b idged he gap be ween labo a o y-scale esea ch and ull-scale
land ill applica ions, educing g eenhouse gas emissions and ha nessing enewable
ene gy.
Keywo ds: Was es, Ene gy c ises, Biomass, Land ill, Feeds ock, Pilo -scale
In e na ional Jou nal o Ad anced Scien i ic and Technical
Resea ch
A ailable online on
h p://www. spublica ion.com/ijs /index.h ml
ISSN 2249-9954
Ci e This Pape : Ene iok O. Usungu ua, Akanimo U. Usungu ua, Why e A.
Akpan, Aniekan E. Ikpe and Uchechi E. I oekwe (2025). "ANAEROBIC
EXPERIMENTATION TO DETERMINE KEY PARAMETERS FOR
OPTIMAL PERFORMANCE OF A PILOT SCALE BIO-DIGESTER FOR
EMULATING LANDFILL CONDITIONS AND GAS RECOVERY".
INTERNATIONAL JOURNAL OF ADVANCED SCIENTIFIC AND
TECHNICAL RESEARCH (IJASTR), ol. 15, no. 5, 2025, pp. 257-272. DOI:
h ps://dx.doi.o g/10.5281/zenodo.17285090
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DOI: 10.5281/zenodo.17285090
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258
1. In oduc ion
Anae obic diges ion is a complex biological p ocess ha has gained signi ican a en ion in
ecen yea s due o i s po en ial o sus ainable was e managemen and enewable ene gy
p oduc ion. This p ocess, which occu s in he absence o oxygen, in ol es he b eakdown o
o ganic ma e by mic oo ganisms, esul ing in he p oduc ion o biogas, p ima ily composed
o me hane (CH
4
) and ca bon dioxide (CO
2
) (Bewani e al., 2025; Ikpe e al., 2025). In he
con ex o land ill managemen and gas eco e y, achie ing op imal anae obic diges ion
p ocesses a e c ucial o de eloping e icien and en i onmen ally iendly was e ea men
solu ions. The inc easing global conce n o e g eenhouse gas emissions, coupled wi h he
g owing need o al e na i e ene gy sou ces, has led o a enewed in e es in ha nessing he
po en ial o land ill gas (LFG) as a aluable esou ce. Land ills, which a e essen ially la ge-
scale anae obic sys ems, p oduce signi ican amoun s o CH
4
ha can be cap u ed and u ilized
as a enewable ene gy sou ce (Ebunilo e al, 2018; Ikpe e al., 2020). Howe e , he complex
and he e ogeneous na u e o land ills p esen s challenges in op imizing gas p oduc ion and
eco e y. To add ess he challenges associa ed wi h anae obic diges ion p ocesses in land ill
en i onmen s, esea che s in his ield ha e u ned o pilo -scale bio-diges e s. These
expe imen al se ups allow o con olled s udies o key pa ame e s ha in luence he
pe o mance o anae obic diges ion sys ems, p o iding adequa e knowledge ha can be applied
o ull-scale land ill ope a ions (E onmosele e al., 2020; Ho chani & Koubaa, 2025). The use
o pilo -scale bio-diges e s o emula ing land ill condi ions o e s se e al ad an ages. Fi s ly,
i allows o he manipula ion and moni o ing o a ious ope a ional pa ame e s in a con olled
en i onmen , which is no easible in ac ual land ills. Secondly, i p o ides a cos -e ec i e
means o es ing di e en was e composi ions, en i onmen al condi ions, and ea men
s a egies wi hou he isks associa ed wi h ull-scale implemen a ion. Las ly, pilo -scale
expe imen s can gene a e da a ha b idges he gap be ween labo a o y-scale s udies and eal-
wo ld applica ions, enhancing he eliabili y and scalabili y o esea ch indings (Ikpe e al.,
2024; El-Sheikh e al., 2025). Key pa ame e s ha in luence he pe o mance o anae obic
diges ion sys ems in land ill-like condi ions include subs a e composi ion and cha ac e is ics,
pH and alkalini y, empe a u e, mois u e con en , o ganic loading a e, hyd aulic e en ion ime
(HRT), nu ien balance, p esence o inhibi o y subs ances and mic obial communi y s uc u e
and dynamics (Gabanki e al., 2025; G iggs e al., 2025; G obelak e al., 2025). Unde s anding
he in e play be ween hese pa ame e s is c ucial o op imizing biogas p oduc ion and eco e y
in land ill en i onmen s. Fo ins ance, he composi ion o he was e subs a e can signi ican ly
a ec he a e and ex en o anae obic deg ada ion, as well as he quali y o he p oduced biogas
(Ikpe e al., 2019; Kabeyi e al., 2025; Kamboj e al., 2025). Simila ly, main aining app op ia e
pH le els and empe a u e anges is essen ial o suppo ing he g ow h and ac i i y o di e se
mic obial communi ies esponsible o he di e en s ages o anae obic diges ion (Kim e al.,
2025; Makondo e al., 2025). Fu he mo e, he mois u e con en o he was e mass plays a
c i ical ole in acili a ing he anspo o nu ien s and mic oo ganisms, as well as he emo al
o inhibi o y subs ances. Op imizing he o ganic loading a e and hyd aulic e en ion ime can
help maximize biogas p oduc ion while p e en ing sys em o e load and ins abili y (La inwo
In e na ional Jou nal o Ad anced Scien i ic and Technical Resea ch ISSN 2249-9954
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DOI: 10.5281/zenodo.17285090
O iginal A icle
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259
e al., 2015, Pe e a e al., 2025). In ecen yea s, ad ances in molecula biology echniques ha e
enabled esea che s o gain deepe insigh s in o he complex mic obial ecology o anae obic
diges ion sys ems. De e mining he s uc u e and dynamics o mic obial communi ies in hese
en i onmen s is c ucial o de eloping s a egies o enhance biogas p oduc ion and p ocess
s abili y (Wang e al., 2019; Kasina h e al., 2021; Angelidaki e al., 2023). This s udy se s he
s age o an in-dep h explo a ion o anae obic expe imen a ion using pilo -scale bio-diges e s
o de e mine key pa ame e s o op imal pe o mance in emula ing land ill condi ions and gas
eco e y, h ough p ac ical in es iga ion o hese pa ame e s and hei in e ac ions. F om he
indings ob ained, esea che s can de elop mo e e icien and sus ainable s a egies o land ill
managemen and biogas u iliza ion, con ibu ing o he b oade goals o was e educ ion,
enewable ene gy p oduc ion, and en i onmen al p o ec ion.
2. Ma e ials and Me hods
2.1. Ma e ials
The a ious ma e ials used in he cou se o he expe imen al p ocedu e in his s udy a e s a ed
as ollows:
a. Samples: O ganic eeds ocks such as ood was e, wa e lea , Cow dung and dis illed
wa e . Va ie y o ood was e we e used du ing he expe imen . These included he
ollowing: Soya beans, Rice, Cocoyam, Cooked Plan ain, Semo i a, Cooked Banana
and Fu u. Samples o Cow dung co-diges ed du ing he expe imen al p ocess o his
s udy was collec ed om a Ca le ange in Uyo, Akwa Ibom S a e. The ood was es
we e sou ced om di e en Ca e e ias, Res au an s, Ho els, households in Iko Abasi
me opolis and i s en i ons.
b. Appa a us: A pH me e , s ainless bowel, ubbe hose, gas cylinde , ball al es,
p essu e gauge, he mome e , weighing scale and 100 li e s Bio-diges e designed wi h
mild s eel
2.2. Me hods
Figu e 1 shows he expe imen al se up o anae obic diges ion o op imize a pilo -scale bio-
diges e emula ing land ill condi ions o gas eco e y ea u es including a Bio-diges e as he
cen al uni whe e o ganic eeds ock unde goes anae obic decomposi ion. A Tempe a u e
Gauge and P essu e Gauge moni o in e nal condi ions o ensu e op imal mic obial ac i i y and
gas p oduc ion. The Inle Val e allows eeds ock in oduc ion, while a Gas Hose connec ed o
a Fil e ex ac s biogas, emo ing impu i ies. A Hand Comp esso wi h a C ank aids in mixing
o p essu e egula ion, and a Gas Cylinde s o es he collec ed biogas. This se up suppo s key
pa ame e es ing (e.g., empe a u e, p essu e, e en ion ime) o enhance gas yield and emula e
land ill p ocesses. A pH me e was used o measu ing he pH o eeds ock be o e, du ing and
a e diges ion o o ganic eeds ock.
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DOI: 10.5281/zenodo.17285090
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Figu e 1: Expe imen al se up o anae obic diges ion
The expe imen al p ocedu e is illus a ed in Figu e 2. The low cha ou lines he expe imen al
p ocess o anae obic diges ion o op imize a pilo -scale bio-diges e emula ing land ill
condi ions o gas eco e y. I begins wi h he Collec ion o Feeds ock, ollowed by
Seg ega ion o Feeds ock o sepa a e componen s, and Cha ac e iza ion o O ganic Feeds ock
o assess p ope ies. Nex , P elimina y Tes ing (pH, Mix Ra io, e c.) de e mines ini ial
condi ions, leading o Homogeniza ion/Mixing o O ganic Feeds ock o uni o mi y. Fu he
Mixing, Pou ing in o Bio-diges e s, and P ope Sealing p epa es he se up, while Obse ing
Ini ial Bio-Diges e Tempe a u e and P essu e moni o s ea ly condi ions. Concu en ly,
Moni o ing P ocess Condi ion o Biogas Yield acks pe o mance, and Obse a ion and
Ex ac ion o Biogas concludes wi h gas collec ion. This sys ema ic app oach iden i ies key
pa ame e s like pH, mix a io, and e en ion ime o op imal bio-diges e e iciency.
Figu e 2:
Flow cha showing expe imen al p ocedu es o anae obic diges ion
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DOI: 10.5281/zenodo.17285090
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3. Resul s and Discussions
In his s udy, he esul s ob ained om he anae obic expe imen a ion o de e mine key
pa ame e s o op imal pe o mance o a pilo scale bio-diges e o emula ing land ill
condi ions and gas eco e y a e p esen ed in Table 1-4.
Table 1: Biogas yield om 25 kg o o ganic was e
Mix Ra io 1:1
Mix Ra io 2:1
HRT Biogas
Yield
(ml
)
P essu e
(Pa)
pH
be o e
Diges ion
Biogas
Yield
(ml)
P essu e
(Pa)
pH a e
Diges ion
Tempe a u e
(
o
C)
14
10
0.2
7.1
30
0.4
6.7
22
15
20
0.3
25
0.36
23
16
25
0.34
25
0.35
24
17
30
0.4
2
5
0.45
29
18
30
0.4
23
0.32
29
19
30
0.4
20
0.3
29
20
40
0.5
20
0.3
32
21
45
0.55
3
5
0.34
33
22
35
0.46
30
0.4
32
23
30
0.39
25
0.35
31
24
30
0.4
25
0.35
31
25
25
0.34
20
0.3
24
26
25
0.35
20
0.3
24
27
15
0.24
20
0.3
22
28
15
0.24
15
0.25
22
29
10
0.2
15
0.25
22
30
10
0.2
10
0.2
22
To al
425
5.91
383
5.52
Table 2: Biogas yield om 20 kg o o ganic was e
Mix Ra io 1:1
Mix Ra io 2:1
HRT Biogas
Yield
(ml)
P essu e
(Pa)
pH be o e
Diges ion
Biogas
Yield
(ml)
P essu e
(Pa)
pH a e
Diges ion
Tempe a u e
(
o
C)
14
10
0.2
7.0
10
0.2
6.7
22
15
20
0.3
14
0.24
23
16
30
0.4
20
0.3
29
17
40
0.5
30
0.4
32
18
35
0.45
34
0.45
31
19
35
0.45
33
0.42
31
20
33
0.42
32
0.43
31
21
31
0.41
25
0.34
31
22
30
0.4
25
0.34
30
23
26
0.36
23
0.33
26
24
20
0.3
18
0.29
23
25
19
0.28
15
0.25
22
26
15
0.25
14
0.24
22
27
10
0.2
10
0.2
22
To al
354
4.82
303
4.43
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Table 3: Biogas yield om 15 kg o o ganic was e
Mix Ra io 1:1
Mix Ra io 2:1
HRT
(Days)
Biogas
Yield
(ml)
P essu e
(Pa)
pH be o e
Diges ion
Biogas
Yield
(ml)
P essu e
(Pa)
pH a e
Diges ion
Tempe a u e
(
o
C)
14
10
0.2
6.9
10
0.2
6.8
22
15
26
0.36
20
0.3
25
16
30
0.4
24
0.35
29
17
40
0.49
30
0.4
32
18
37
0.46
30
0.4
31
19
35
0.45
25
0.34
30
20
29
0.4
23
0.33
28
21
24
0.35
20
0.3
25
22
14
0.24
14
0.24
23
23
10
0.2
10
0.18
22
To al
255
3.45
204
3.04
Table 4: Biogas yield om 10 kg o o ganic was e
Mix Ra io 1:1
Mix Ra io 2:1
HRT
(Days)
Biogas
Yield
(ml)
P essu e
(Pa)
pH be o e
Diges ion
Biogas
Yield
(ml)
P essu e
(Pa)
pH a e
Diges ion
Tempe a u e
(
o
C)
13
12
0.22
7.0
10
0.2
6.7
22
14
23
0.33
18
0.28
24
15
27
0.38
24
0.35
26
16
30
0.4
25
0.36
31
17
28
0.38
20
0.3
27
18
19
0.30
10
0.2
23
19
12
0.21
8
0.18
22
Sum
151
2.22
115
1.87
Figu e 3 is a ho izon al ba cha illus a ing he ela ionship be ween di e en weigh s o
o ganic eeds ock (10 kg, 15 kg, 20 kg, and 25 kg) and hei co esponding hyd aulic e en ion
imes (HRT) in days (19 days, 23 days, 27 days, and 30 days) wi hin he con ex o an anae obic
expe imen a ion se up. The in o ma ion on he cha was ob ained om Tables 1-4, which we e
measu ed om he expe imen al se up. This se up was designed o de e mine key pa ame e s
o op imal pe o mance in a pilo -scale bio-diges e ha emula es land ill condi ions, wi h a
ocus on biogas (p ima ily me hane) eco e y. The y-axis labels he eeds ock weigh s in
ascending o de om bo om o op (10 kg a he bo om, 25 kg a he op), while he x-axis
ep esen s HRT in days, anging om 0 o 30 in inc emen s o 5. Each ba , illed in blue,
ex ends igh wa d o indica e he HRT alue o ha speci ic eeds ock weigh , showing a clea
end o inc easing HRT as eeds ock mass inc eases. Key obse a ions om he cha in Figu e
3 a e highligh ed as ollows:
i.
10 kg eeds ock: The ba ex ends o app oxima ely 19 days, indica ing he sho es
HRT among he es ed masses.
ii.
15 kg eeds ock: The ba eaches abou 23 days, showing a mode a e inc ease.
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iii.
20 kg eeds ock: The ba goes o oughly 27 days, u he ex ending he e en ion
pe iod.
i .
25 kg eeds ock: The ba hi s a ound 30 days, he longes HRT in he da ase .
a. Rela ionship be ween Feeds ock Mass and HRT
The ela ionship depic ed is posi i e and nea ly linea : as he mass o o ganic eeds ock
inc eases, he HRT also inc eases. This implies ha highe eeds ock loads equi e longe
e en ion imes o achie e op imal diges ion and gas eco e y in he bio-diges e sys em
emula ing land ill condi ions. To quan i y his:
i.
The inc emen in eeds ock mass is consis en a 5 kg in e als ( om 10 o 15 kg, 15 o
20 kg, and 20 o 25 kg).
ii.
Co esponding HRT inc eases a e 4 days (19 o 23), 4 days (23 o 27), and 3 days (27
o 30), a e aging abou 3.67 days pe 5 kg inc ease (o oughly 0.73 days pe kg).
iii.
O e all, om 10 kg o 25 kg (a 15 kg inc ease), HRT ises by 11 days ( om 19 o 30),
yielding a slope o app oxima ely 0.73 days pe kg i assuming a linea i .
b. In eg a ion o P o ided Pa ame e s (pH and Tempe a u e)
The expe imen 's condi ions o 6.9-7.1 pH be o e diges ion, d opping o 6.7-6.8 a e , and a
empe a u e ange o 22-33°C p o ide c i ical con ex o in e p e ing his ela ionship, as hey
in luence mic obial ac i i y and diges ion kine ics.
pH Conside a ions
i.
P e-diges ion pH (6.9-7.1) is nea neu al, ideal o in oducing eeds ock wi hou
immedia e shocking he mic obial communi y. This ange suppo s ini ial hyd olysis by
acid- o ming bac e ia.
ii.
Pos -diges ion pH (6.7-6.8) shows a sligh dec ease, which is ypical in anae obic sys ems
due o VFA p oduc ion du ing acidogenesis. Howe e , i emains wi hin he op imal ange
o me hanogens (gene ally 6.5-7.5), indica ing good bu e ing capaci y (possibly om
inhe en eeds ock alkalini y o amendmen s no speci ied). I HRT we e oo sho o
highe masses, VFAs could accumula e excessi ely, d opping pH below 6.5 and causing
"sou " diges e ailu e (inhibi ed me hane p oduc ion). The inc easing HRT wi h mass
likely p e en s his by allowing mo e ime o VFA consump ion, main aining pH s abili y
and enabling consis en gas eco e y ac oss all loads.
iii.
In land ill-emula ing bio-diges e s, s able pH is c ucial o simula ing long- e m was e
s abiliza ion, whe e uncon olled acidi ica ion can educe gas yields by 20-50% in poo ly
managed sys ems.
Tempe a u e Conside a ions
i.
The 22–33°C ange alls wi hin he mesophilic egime ( ypically 20-40°C), whe e
mesophilic bac e ia h i e a mode a e a es wi hou he ene gy inpu s needed o
he mophilic sys ems (50-60°C). This is ene gy-e icien o pilo -scale se ups emula ing
ambien land ill empe a u es, which o en a y seasonally bu a e age a ound 25-35°C
due o exo he mic decomposi ion.
ii.
A lowe empe a u es (e.g., 22°C), eac ion a es slow, necessi a ing longe HRT o
achie e simila deg ada ion le els-aligning wi h he cha 's end o ex ended e en ion o
highe masses. Con e sely, a he uppe end (33°C), kine ics accele a e, bu highe loads
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s ill equi e mo e ime o handle inc eased subs a e olume wi hou o e whelming he
sys em.
iii.
Tempe a u e luc ua ions wi hin his ange could sligh ly a ec he exac HRT needed; o
ins ance, coole condi ions migh ampli y he need o longe e en ion o compensa e o
educed mic obial ac i i y. O e all, his mesophilic se up p omo es s able, cos -e ec i e
ope a ion o gas eco e y, wi h HRT adjus men s ensu ing op imal pe o mance despi e
a ying eeds ock masses.
c. Implica ions o Op imal Bio-Diges e Pe o mance
De e mining key pa ame e s o a pilo -scale bio-diges e emula ing land ill condi ions, he
cha in Figu e 3 highligh s HRT as a scalable pa ame e ied o eeds ock mass. Fo op imal
gas eco e y:
i.
Lowe masses (e.g., 10 kg) allow sho e HRT (19 days), sui able o low-load scena ios
wi h as e u no e and po en ially highe daily gas ou pu pe uni mass.
ii.
Highe masses (e.g., 25 kg) demand longe HRT (30 days) o a oid o e load, ensu ing
comple e diges ion and maximizing cumula i e biogas yield ( ypically 0.2-0.6 m³/kg
ola ile solids in mesophilic sys ems).
iii.
This ela ionship indica es he ade-o in bio-diges e design: sho e HRT imp o es
h oughpu bu isks ins abili y a high loads, while longe HRT enhances eliabili y and
gas quali y (highe me hane con en ) bu educes capaci y.
i .
Conside ing he pH s abili y and mesophilic empe a u es, he sys em appea s well-
op imized, wi h no signs o inhibi ion. Fo eal-wo ld land ill emula ion, hese indings
could in o m scaling: e.g., HRT should be adjus ed p opo ionally o was e inpu o
sus ain 50-70% me hane in eco e ed gas, educing g eenhouse emissions compa ed o
uncon olled land ills.
Figu e 3: Rela ionship be ween masses o o ganic eeds ock and co esponding HRT in days
Figu e 4 g aphically illus a es a ho izon al g ouped ba cha depic ing he cumula i e biogas
yield (in ml) o wo di e en mix a ios o wa e o o ganic eeds ock, 2:1 (o ange ba s) and
0 5 10 15 20 25 30
25 Kg o eeds ock
20 Kg o eeds ock
15 Kg o eeds ock
10 Kg o eeds ock
HRT (Days)
Weigh o Feeds ock
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1:1 (blue ba s) ac oss a ying eeds ock masses (10 kg, 15 kg, 20 kg, and 25 kg). This da a
appea s o s em om he same anae obic expe imen a ion con ex as p e iously discussed,
aimed a op imizing pa ame e s o a pilo -scale bio-diges e ha emula es land ill condi ions
o enhanced gas eco e y. The y-axis ca ego izes he eeds ock masses in ascending o de
om bo om o op (10 kg a he bo om, 25 kg a he op), while he x-axis measu es cumula i e
biogas yield om 0 o 450 ml in inc emen s o 50 ml. Fo each eeds ock mass, wo ba s a e
p esen ed side-by-side: o ange o he 2:1 mix a io (mo e dilu ed, highe wa e con en ) and
blue o he 1:1 mix a io (less dilu ed, highe subs a e concen a ion). These esul s indica e
consis en pa e ns: highe eeds ock masses p oduce g ea e absolu e biogas yields o bo h
a ios, and he 1:1 a io ou pe o ms he 2:1 a io ac oss all masses. The ba s a e uni o mly
s yled, emphasizing di ec compa isons wi hin and ac oss ca ego ies.
a. Rela ionship be ween Mix Ra ios, Feeds ock Mass, and Cumula i e Biogas Yield
Figu e 4 illus a es wo p ima y ela ionships: (1) a posi i e co ela ion be ween eeds ock mass
and biogas yield o each mix a io, and (2) a consis en ad an age o he 1:1 wa e - o- eeds ock
a io o e he 2:1 a io in e ms o yield, wi h he gap widening sligh ly a highe masses. These
ends a e analysed in his s udy, wi h espec o he con ex o anae obic diges ion p inciples,
whe e biogas (p ima ily me hane and ca bon dioxide) is p oduced h ough mic obial
b eakdown o o ganic ma e in oxygen- ee condi ions.
b. E ec o Feeds ock Mass on Biogas Yield
In Figu e 4, as eeds ock mass inc eases om 10 kg o 25 kg, cumula i e biogas yield ises
p opo ionally o bo h mix a ios. This is expec ed, as g ea e o ganic mass p o ides mo e
subs a e ( ola ile solids) o mic obial deg ada ion, leading o highe gas p oduc ion. The
ela ionship appea s nea ly linea :
i. Fo he 2:1 a io: Yield inc eases by 40 ml (10 o 15 kg), 60 ml (15 o 20 kg), and 70
ml (20 o 25 kg), a e aging 57 ml pe 5 kg inc emen (o 11.4 ml pe kg).
ii. Fo he 1:1 a io: Yield inc eases by 40 ml (10 o 15 kg), 60 ml (15 o 20 kg), and 80
ml (20 o 25 kg), a e aging 60 ml pe 5 kg inc emen (o 12 ml pe kg).
iii. O e all slope: F om 10 kg o 25 kg (15 kg inc ease), yields ise by 170 ml o 2:1 (110
o 280 ml) and 180 ml o 1:1 (140 o 320 ml), yielding app oxima e linea i s o Yield
(2:1) 40 + 11.3 × mass (kg) and Yield (1:1) 70 + 12 × mass (kg). The sligh accele a ion
a highe masses (la ge inc emen s) may indica e economies o scale, whe e la ge
loads enhance mic obial syne gies o hea e en ion in he diges e , boos ing e iciency.
c. Implica ions o Bio-Diges e Pe o mance
In a pilo -scale sys em emula ing land ill condi ions (slow, laye ed decomposi ion), highe
masses mimic dense was e accumula ion, po en ially inc easing gas eco e y po en ial.
Howe e , wi hou co esponding adjus men s (e.g., o hyd aulic e en ion ime, as no ed in
p io analysis: 19 days o 10 kg, up o 30 days o 25 kg), o e load could occu . The inc easing
yields sugges he expe imen main ained s abili y, allowing ull subs a e u iliza ion. Absolu e
yields a e modes (e.g., 11-13 ml/kg o 1:1), ypical o lab/pilo scales wi h o ganic was e
unde mesophilic condi ions, bu scalable o land ill scena ios whe e yields can each 100-200
ml/kg ola ile solids o e longe pe iods (Ikpe e al., 2023).
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