PROCEEDINGS OF THE II INTERNATIONAL SYMPOSIUM ON ANAEROBIC DIGESTION OF SOLID
WASTE. BARCELONA. JUNIO 1999. PAG. 192-195.
CODIGESTION OF PIG SLURRY AND ORGANIC
WASTES FROM FOOD INDUSTRY
Elena Campos, Jo di Pala si and Xa ie Flo a s
Depa men o En i onmen and Soil Science, Uni e si y o Lleida. Ro i a Rou e, 177.
25198 Lleida, Spain.
ABSTRACT
Anae obic diges ion o pig slu y can be a good op ion o ge a highe alue o hese was es. Al hough
he mophilic anae obic diges ion is mo e e icien han mesophilic anae obic diges ion, i p esen s some
limi a ions, like less s abili y and an inc eased e ec o some inhibi o s. The main inhibi o o pig slu ies is
ee ammonia. In o de o imp o e he me hane p oduc ion, some mix u es o slu y and o ganic was es om
ood indus y we e es ed, like was es om ui and oli e oil e ine y indus ies (pea was e and oil
bleaching ea h). A ba ch expe imen was ca ied ou , in o de o de e mine he maximum po en ial o
me hane p oduc ion and biodeg adabili y o hese was es. The expe imen was de eloped in mesophilic and
he mophilic anges (35º and 55º). The mesophilic esul s we e be e han he he mophilic ones, showing a
la ge inhibi ion by ammonia in he he mophilic ange. In bo h empe a u e anges, he me hane p oduc ion
was imp o ed by addi ion o a co-subs a e. The highe me hane p oduc ion was ob ained om he
codiges ion o slu y and oil bleaching ea h (95% and 5% espec i ely). The me hane yield was 344 mL
CH4/g VSini ial, which is 2.4 imes he me hane yield o slu y (144.0 mL CH4/g VSini ial).
KEYWORDS:
Anae obic diges ion; codiges ion; ammonia inhibi ion; o ganic indus ial was es; pig slu y; empe a u e.
INTRODUCTION
In Ca alonia he e a e mo e han i e million pigs, p oducing mo e han 30.000 m3/day o was es. The
anae obic diges ion can be a good op ion o ge a highe alue o hese was es. The mophilic anae obic
diges ion has some heo e ical ad an ages o e mesophilic, like a be e sani a ion o e luen s, as e p ocess
a es and bigge me hane yield. Howe e , he slu y p esen s a e y high concen a ion o ammonia, which
has been desc ibed as a e y impo an inhibi o o anae obic p ocess. F ee ammonia is he ac i e
componen causing ammonia inhibi ion (Angelidaki e al., 1993), and i s concen a ion depends on he o al
ammonia, pH and empe a u e. The inhibi o y concen a ion depends on he mic o-o ganisms adap a ion
phenomena (Van Velsen e al., 1979; Kos e , 1986; Hansen e al., 1998). So, a wide a ie y o inhibi o y
alues a e ound in he li e a u e, i.e. 80 mg N-NH3/L (Kos e , 1986), 700 mg N-NH3/L (Angelidaki e al.,
1993) o 1100 mg N-NH3/L (Hansen e al.1998).
By codiges ion o di e en ypes o was es, such as manu e, household solid was e and o ganic indus ial
was e, a highe gas yield can be ob ained om biogas eac o s. Indus ial was es a e mo e easily deg adable
and ha e a highe gas po en ial han manu e, a ying om 30 o 500 m3/ on (Ah ing e al., 1992; Angelidaki
e al., 1997). Slu y can be an excellen basic subs a e o he codiges ion, because i has a high wa e
con en s, a high bu e ing capaci y and a wide a ie y o needed nu ien s o anae obic bac e ia. (Angelidaki
e al., 1997). P e ious expe ience o codiges ion o slu y and sewage sludge, wi h sa is ac o y esul s, has
been epo ed (Flo a s e al., 1999). Codiges ion o manu e and oil bleaching ea h (OBE) has p o ided e y
good esul s in Denma k (Ah ing e al., 1992), due o he high lipids con en o his kind o was es, ha
p o ides a high po en ial o biogas p oduc ion (Ah ing e al., 1992). Howe e , an excess o lipids can cause
inhibi ion (Hanaki e al., 1981; Ah ing e al.,1992). O he in e es ing indus ial was es a e hose p oduced in
ui juice ac o ies. The main p oblem associa ed wi h diges ion o ligno-cellulosic was es is he
main enance o s able pH, which is associa ed wi h i s poo bu e ing capaci y and ola ile a y acids
accumula ion. Combina ion wi h ano he was e wi h high bu e ing capaci y can be a good way o diges i
(Banks e al., 1998). Bo h ypes o was es (OBE and pea was e) a e p oduced in la ge quan i y in he a ea o
Lleida (Ca alonia, Spain), and he objec i e o he p esen wo k is o analyse he pe o mance o i s
codiges ion wi h pig slu y, using ba ch diges ion es s.
MATERIAL AND METHODS
The ba ch eac o s we e 120 mL glass ials, illed wi h 50 g. o sample and 5 g. o inoculum, ini ially
bubbled wi h N2/CO2 gas mix u e o ai displacemen , igh ly closed wi h ubbe aps, placed in incuba o s
held a 35ºC (mesophilic es ) and 55ºC ( he mophilic es ), and ollowed o 75 days. Fi e epe i ions we e
in ol ed o e e y ea men and e e y empe a u e. Duncan’s mul iple s a is ical es was applied o gas
p oduc ion compa ison among ea men s and empe a u es. The inoculum p oceeded om an anae obic
diges e ea ing pig slu y since 1983, in he mesophilic ange. The pig slu y used came om a a ening
pig a m nea Lleida. The pea was e came om a ui juice ac o y, close o Lleida. The OBE was e came
om an oli e oil bleaching and il e ing ac o y. The expe imen al design consis ed o ele en ea men s and
a blank un, pe o med a 35ºC and 55ºC empe a u es. Table 1 shows p opo ions used o each co-subs a e
and subs a e composi ion o each ea men .
TABLE 1. SUBSTRATE COMPOSITION FOR EACH TREATMENT
T ea
men
Slu y
%
Pea
Was e
%
OBE
%
Wa e
%
TS
(1)
VS
(1)
COD
(2)
TKN
(3)
NH4
+
(3)
pH To al
Alk
(4)
VFA
Alk
(5)
Alk.
Ra e
T1 100 - - 0 7.92 5.87 82.50 5.06 3.43 8.06 10.55 3.66 0.29
T2 95 - - 5 7.52 5.58 78.37 4.82 3.28 7.96 10.05 3.30 0.27
T3 87.5 - - 12.5 6.93 5.14 72.18 4.44 2.97 8.03 8.98 3.09 0.29
T4 80 - - 20 6.33 4.69 66.00 4.05 2.70 7.95 8.20 2.88 0.29
T5 95 5 - - 9.29 7.29 102.4 4.91 3.21 7.55 9.75 3.66 0.31
T6 87.5 12.5 - - 11.35 9.45 132.3 4.98 3.01 7.25 8.73 3.54 0.34
T7 80 20 - - 13.41 11.63 162.1 4.66 2.71 6.88 7.58 3.39 0.37
T8 - 20 - 80 7.08 6.98 96.14 0.89 0.08 3.45 0.00 0.00 -
T9 95 - 5 - 12.40 7.54 136.9 4.76 3.20 7.69 9.50 3.75 0.33
T10 87.5 - 12.5 - 19.13 10.09 218.5 4.48 3.04 7.33 8.10 3.66 0.38
T11 - - 12.5 87.5 12.2 4.94 58.54 0.38 0.04 6.93 0.95 0.90 0.79
(1)To al and ola ile solids a e exp essed as % (w/w); (2) Chemical Oxygen Demand in g O2/Kg; (3) To al
Kjeldahl Ni ogen and o al ammonia a e exp essed as g N/Kg; (4) To al alkalini y is exp essed as g
CaCO3/L; (5) Vola ile a y acids alkalini y is exp essed as g AcH/L.
Analy ical p ocedu es. Gas analysis (N2, CH4, CO2) we e ca ied ou by gas ch oma og aphy using a
The moques 8000 ch oma og aph wi h a TCD and a packed s eel column Po apak N. To al and ola ile
solids, COD, pH, alkalini y and Kjeldahl and ammonia ni ogen we e de e mined acco ding o S anda d
Me hods (APHA, 1995). F ee ammonia concen a ion was calcula ed om he equilib ium ela ionship.
RESULTS AND DISCUSSION
Accumula ed me hane p oduc ion and yields ob ained a 75 days ba ch es a e p esen ed in Table 2, wi h he
esul s o he Duncan es .
Resul s in mesophilic expe imen . Non s a is ically signi ican di e ences we e ob ained among he di e en
slu y dilu ions es ed ( ea men s T1-T4), showing non-inhibi ion e ec by ammonia o his empe a u e.
Al hough he high o al ammonia concen a ion (2.7-3.4 g N-NH4/L), he ee ammonia concen a ion
p esen s a low alue a he beginning o he diges ion. The e ec o slu y/pea mix u e was no signi ican
o me hane ( ea men s T5-T8). Fo T7 ea men (20% o pea was e), he p ocess ailed, p obably due o a
less bu e ing capaci y and a highe ib e con en s. Diges ion o pea was e (T8) couldn’ de elop due o a
low pH and bu e ing capaci y. Codiges ion o slu y and OBE ( ea men s T9-T10) showed a e y good
beha iou a 35ºC, p esen ing a s a is ically signi ican highe me hane p oduc ion han hose ob ained o
he o he ea men s. The T10 p ocess showed a lag phase, p obably due o a sligh inhibi ion by long chain
a y acids. The lipid con en s in his mix u e was 35.7 g/L, highe han alues epo ed by o he au ho s
(Ah ing e al., 1992; Hanaki e al., 1981).
TABLE 2. METHANE PRODUCTION AND YIELD BY TREATMENT AND TEMPERATURE,
AT 75 DAYS BATCH TEST
Me hane P oduc ion
(mL CH4)
Me hane Yield
(mL CH4/gSVini)
Me hane Yield
(mL CH4/gSVini)
55ºC 35ºC 55ºC 35ºC Di e ences due
o empe a u e
T1 192.6 de 439.8 c 63.1 c 144.0 b 80.9*
T2 199.1 de 425.1 c 70.0 cd 144.0 b 74.0*
T3 246.2 e 365.8 c 90.8 de 134.8 b 44.0*
T4 293.4 367.3 c 114.6 143.6 b 29.0*
T5 419.1 g 534.0 c 110.7 e 141.0 b 30.3*
T6 518.0 h 828.4 d 107.4 e 171.6 b 64.2*
T7 535.3 h 188.4 b 88.1 de 31.0 a -57.1*
T8 0.0 a 0.0 a 0.0 a 0.0 a -
T9 6.8 ab 1289.0 1.8 a 343.9 d 342.1*
T10 136.5 cd 1050.1 e 26.9 b 206.6 c 179.7*
T11 77.3 bc 9.8 a 29.7 b 3.8 a -
Duncan’s mul iple es wi h a 95% con idence le el: Di e en le e means
signi ican di e ences among he means, by columns ( o each empe a u e);
(*) means signi ican di e ences be ween empe a u es o each ea men .
Resul s in he mophilic expe imen . Fo slu y dilu ion ea men s, he highes me hane p oduc ion was
ob ained in he T4 ea men (20% o wa e ). In hese expe imen s, me hane yield and ini ial ee ammonia
concen a ion a e e y well co ela ed, as can be shown in Figu e 1, indica ing a signi ican inhibi o y
ammonia e ec . Fo slu y/pea mix u es, he highes yield alue was 110.7 mL CH4/g VS o T5 ea men ,
which is smalle han T4 ea men , bu no s a is ically di e en . Taking in o accoun ha he T5 ea men
has highe ini ial ammonia concen a ion han he T4, i can be said ha he main e ec o pea was e is he
addi ion o o ganic ma e . Co-diges ion o slu y and OBE p esen ed low gas p oduc ion, indica ing
inhibi ion by ammonia and LCFA.
All ea men s p esen signi ican di e ences, a 95% con idence le els, be ween mesophilic and
he mophilic anges. Inhibi ion by ee ammonia concen a ion a he mophilic ange, inc easing o 1000 mg
N-NH3/L du ing he expe imen , could be he main e ec . Taking in o accoun some p e ious good
expe iences wi h highe le els o ammonia con en s (Hansen e al., 1998), he impo ance o he adap a ion
o biomass used as inoculum mus be ema ked.
Figu e 2. Co ela ion be ween me hane yield and ee ammonia concen a ion, a 55ºC
CONCLUSIONS
Codiges ion o slu y wi h o he subs a es could be a e y good op ion o inc ease he me hane p oduc ion.
Codiges ion wi h OBE showed a e y good beha iou a mesophilic ange, wi h a me hane yield 2.4 imes
bigge han o slu y diges ion. The main e ec o pea was e addi ion was inc ease o o ganic ma e . In
gene al he mesophilic ange showed a be e beha iou han he he mophilic one, showing a clea
inhibi ion by ee ammonia. The p e ious adap a ion o inoculum is basic o p ocess pe o mance.
ACKNOWLEDGMENTS
This esea ch has been suppo ed by he Lleida Council (Pae ia), and by a g an om CIRIT (Gene ali a o
Ca alunya).
REFERENCES
Ah ing, B., Angelidaki, I., Johansen, K.(1992).Anae obic ea men o manu e oge he wi h indus ial
was e. Wa . Sci. Tech. 25 (7), 311-318
Ame ican Public Heal h Associa ion (1995). S anda d Me hods o he Examina ion o Wa e and
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Angelidaki, I., Ah ing, B. (1993). The mophilic anae obic diges ion o li es ock was e: he e ec o
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Banks, C.J., Humph eys, P.N.(1998). The Anae obic T ea men o a Ligno-cellulosic subs a e o e ing li le
na u al pH bu e ing capaci y. Wa . Sci. Tech. 38 (4-5), 29-35.
Flo a s, X., Bonma í, A., Campos, E., An únez, M. (1999). Ensayos en discon inuo de codiges ión anae obia
e mo ílica de pu ines de ce do y lodos esiduales. E ec o del amonio. In . Tecn., 10 (1) 79-85.
Hanaki, K., Ma suo, T., Nagase, M. (1981). Mechanism o Inhibi ion Caused by Long-Chain Fa y Acids in
Anae obic Diges ion P ocess. Bio ech. Bioengin., 23, 1591-1610.
Hansen, K., Angelidaki, I., Ah ing, B.(1998). Anae obic diges ion o swine manu e: Inhibi ion by ammonia.
Wa e Resea ch, 32 (1), 5-12.
Kos e , I.W. (1986). Cha ac e is ics o he pH-in luenced adap a ion o me hanogenic sludge o ammonium
oxici y. J- Chem. Tech. Bio ech 36, 445-455.
Van Velsen (1979). Adap a ion o Me hanogenic sludge o high ammonia-ni ogen concen a ions. Wa e
Resea ch, 13, 995-999
CH4/VSi = -0.0636*[N-NH3] + 72.962
R2 = 0.7777
CH4/VSi = -0.2889*[N-NH3] + 341.56
R2 = 0.8573
0
20
40
60
80
100
120
140
700 750 800 850 900 950 1000
N-NH3 (mg N/L)
mL CH4/g VSi
Day 15
Day 75