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Biological Wastes 20 (1987)1209-215

A Note on Stimulation of Biogas Production from CattleDung by Addition of Charcoal

Sushil Kumar, M. C. Jain & P. K. ChhonkarDivision of Soil Scienceand Agricultural Chemistry,Indian AgriculturalResearchInstitute,New Delhi--110012, India

(Received 4 June 1986; accepted 27 August 1986)

A B S T R A C TV a r i o u s f o r m s o f c a r b o n w e r e s cr e e n e d f o r t h e ir a b i l i ty t o s t i m u l a t e b i o g a s

p r o d u c t i o n in b a t c h f e r m e n t e r s a n d t h e c o m m e r c i a l c h a rc o a l w h ic h w a s f o u n dto be mos t e f f i c ien t was t r i ed in a s emi -con t inuous anaerob ic d iges te r . Thea d d i t io n o f 5 % c o m m e r c i a l c h a r c o a l to c o w d u n g o n a d r y w e i g h t b a s isr e s u lt e d in a u g m e n t a t i o n o f g a s p r o d u c t io n b y 1 7 % a n d 3 4 "7 % in b a tc h a n ds e m i - c o n t i n u o u s f e r m e n t e r s , r e s p ec t iv e l y. A n a l y s i s o f t h e m i c r o b i a l p r o f il e o ft h e f e r m e n t e r s s h o w e d t h a t f e r m e n t e r s w i t h c h a rc o a l h a d a h i g h e r n u m b e r o fb o t h t o t a l a n a e r o b ic b a c t e r i a a n d c e l lu l o ly t ic s . T h e d e c o m p o s i t i o n o f V o l a t il eS o li d s i nc re a se d r o m 3 0 % t o 3 4 % a n d C O D r ed u ct io n f r o m 5 5 % t o 6 9 % o na d d i t i o n o f c h a r c o a l t o t h e s e m i - c o n t i n u o u s d i g e s te r . T h e V o l a t il e F a t t y A c i dconcen tra t ions were s imi lar and w i th in the accep tab le l imi t s . Loca l ly -p r o d u c e d w o o d c h a r c o a l w a s a s g o o d a s t h e c o m m e r c i a l c h a r c o a l i n b a t c hd iges t ions , bu t o ther fo rm s o f carbon were no t as e f fi c ien t .

INTRODUCTIONAnaerobic digestion of cellulosic waste materials for the production ofmethane is not only relatively slow but also can have poor process stability.The bacterial activity involved in the process is primarily associated withparticulate materials with much of it occurring on the surfaces of solidparticles (Hobson, 1973). Therefore, attempts have been made in the past tostimulate the microbial activity by incorporating solid, inert materials in

209Biological Wastes 0269-7483/87/$03.50 ElsevierApplied SciencePublishers Ltd, England,1987. Printed in Great Britain

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210 Sus h i l K um ar , M. C . J a i n, P . K . Chhonk aran aer ob ic d iges te rs (Barker , 1956). A ct iva te d carb on has a s t im ula to ry e ff ec to n a n a e r o b i c d i g e s t i o n (A d a m s , 1 9 7 6 ). A t t e m p t s w e r e t h e r e f o r e m a d e t oe n h a n c e b i o g a s p r o d u c t i o n b y a d d i n g c h a r c o a l i n v a r io u s f o r m s t o c a t tl ed u n g u s e d a s f e e d s t o c k s i n b a t c h a n d s e m i - c o n t i n u o u s d i g e s t e r s . D i g e s t e rp e r f o r m a n c e p a r a m e t e r s w e r e m o n i t o r e d .

M E T H O D ST h e b a t c h an d sem i - co n t i n u o u s d i g e s t e r s w e r e m a i n t a i n ed a t 3 5 ___ I C .P o w e r e d c h a r c o a l ( D a r c o G 6 0 ) o r o t h e r c a r b o n s w e r e m i x e d w i th f r es hd u n g b y w e i g h t o n a d r y w e i g h t b a s i s a t d i f f e r en t l ev e l s ( s ee T ab l e s ) an dm a d e i n t o a p a s te b y a d d i n g a n i n o c u l u m o f 1 0 0 m l o f d i ge s te d c o w d u n go b t a i n e d f r o m a G o b a r G a s P l a n t , t h e n d i l u t e d w i t h w a t e r t o m a k e u p5 1 it re s o f s lu r r y c o n t a i n i n g 8 % T o t a l S o l i d s. T h i s w a s f e r m e n t e dan ae r o b i ca l l y i n 6 . 5 - 1 i t r e c ap ac i t y g l a s s b o t t l e s a s d e sc r i b ed ea r l i e r( K u m a r & B i sw a s , 1 9 8 2 ) . S i m u l t a n e o u s l y , t h e s a m e a m o u n t o f s lu r ry ,p r e p a r e d a s a b o v e w i t h D a r c o G 6 0 c h a r c o a l , w a s p l a c e d i n a s e m i -c o n t i n u o u s d i g e s t e r ( 6 . 5 l i t r e s ) d e s i g n e d i n o u r l a b o r a t o r y ( J a i n &K u m ar , 1 9 8 6 ) . I n i ti a l ly , th e d i g e s t e r s w e r e l o ad ed w i t h 5 l it re s o f s l u r r yw i t h 8 % T o t a l S o lid s . S u b s e q u e n t l y , 1 2 5 m l o f s l u r ry w i t h o r w i t h o u tc h a r c o a l w a s i n t r o d u c e d i n t o t h e f e r m e n t e r s e v e r y d a y s o a s to g i v e a 4 0 - d a yr e t e n t i o n t i m e . C o w d u n g a l o n e s e r v e d a s c o n t r o l i n b o t h s y s t e m s .

T h e g a s w a s c o l le c t e d o v e r s a l in e w a t e r i n g r a d u a t e d j a r s a n d i ts v o l u m em e a s u r e d d a i l y . G a s s a m p l e s w e r e a n a l y s e d e v e r y 1 0 d a y s u s i n g a g a sc h r o m a t o g r a p h w i t h a t h e r m a l c o n d u c t i v i ty d e te c t or . A l iq u o t s o f fr e sh a n dd i g es t ed s l u r r y s am p l e s w e r e an a l y se d a t 1 0 - d ay i n t e r v a l s o v e r a p e r i o d o f 4 0d a y s f o r T o t a l S o l id s , V o l a t il e S o li ds , C h e m i c a l O x y g e n D e m a n d , p H a n dv o l a ti le a ci d s b y s t a n d a r d m e t h o d s ( A P H A 1 97 5). T o t a l a n a e r o b i c b a c t e r i aw e r e e n u m e r a t e d b y t h e m e t h o d o f M a k i ( 19 54 ) a n d c e l lu l o s e h y d r o l y s i n gb a c t e r i a b y t h e m e t h o d o f M a h & S u s m a n ( 19 67 ). A ll a n al y s e s w e r e c a r r ie do u t i n d u p l i c a t e a n d t h e v a l u e s r e p o r t e d a r e t h e m e a n v a l u e s .

R E S U L T S A N D D I S C U S S I O NBatch fermentat ion

P e r i o d ic a n d t o ta l y i e ld s o f b i o g as o b t a i n e d f ro m c o w d u n g a l o n e a n d t r e a te dw i t h d if fe r e n t c o n c e n t r a t i o n s o f D a r c o G 6 0 c h a r c o a l a r e s h o w n i n T a b l e s 1a n d 2 . T h e s e b a t c h f e r m e n t a t i o n s s h o w e d a 1 7 % i n c re a s e i n g a s p r o d u c t i o ni n th e t r e a t m e n t r e c e iv i n g 5 % p o w d e r e d c h a rc o a l, b u t m o r e t h a n 5 % d i d n o t

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Digestion with charcoal 211

T A B L E 1Per i od ic a nd To t a l Y i e l ds o f B i ogas (l itr es pe r k i l og ram dry w e i gh t o f cow dung) O b t a i nedf rom C ow D ung and i ts A dmi x t u res w i th D arco G 60 C harco a l a t D i ff er en t C oncen t r a t i onsin Batch Diges ters

Period Cow dung Cow dung + Cow dung + Cow dung +(days) alone 5% charcoal 10~% charcoal 15% charcoal

1-7 44-10 64 .54 71 .82 68.888-1 4 46.20 59-08 65.52 63.2815-21 45.08 53-06 52.08 50.54

22 -28 32.62 25.48 22.68 19.6029 -35 18.90 17.92 12.60 17.5036 -40 6.58 7.00 5.88 8.68T ot al 193.48 227.08 230.58 228.48

c h a n g e g a s p r o d u c t i o n . H o w e v e r , i n t r ia l s in w h i c h a g r a n u l a r f o r m o f D a r c oG 6 0 c h a r c o a l w a s u s e d t h e r e w a s n o s i g n i f i c an t i n c re a s e i n th e g a s p r o d u c e d .W i t h 1 % t o 5 % p o w d e r e d D a r c o G 6 0 c h a r c o a l t h e i n c r e a s e i n t h e g a sp r o d u c t i o n w a s i n p r o p o r t i o n t o th e c h a r c o a l c o n c e n t r a t i o n ( T a b l e 2). N os i g n if i c a n t c h a n g e i n t h e r a t e o f g a s p r o d u c t i o n d u r i n g t h e f i rs t w e e k o fd i g e s t i o n w a s o b s e r v e d i n i t i a l ly b u t t h e e f f ic i e n cy o f t h e d i g e s t e r w a si m p r o v e d s u b s e q u e n t ly . T h e c u m u l a t i v e g a s y i e ld s o v e r th e t h i r d w e e k o fd i g e s t i o n a m o u n t e d t o 8 5 % o f t h e t o t a l g a s y ie ld s , a n d t h e g a s c o m p o s i t i o nw a s 6 2 % m e t h a n e a n d 3 7 % c a r b o n d i o x id e . O t h e r e x p e r i m e n t s w e re

T A B L E 2Per iodic and To ta l Yie lds of Biogas ( li tres pe r k i logram d ry weight of cow dung) Obta in edf rom C ow D ung and i t s Mi x t u r e w i t h D arco G 60 C harcoa l i n B a t ch D i ges t e r s

Period Cow dung Cow dung Cow dung Cow dung Cow dung Cow dung(days) control + 1% + 2% + 3% + 4% +5%charcoal charcoal charcoal charcoal charcoal

1-7 70 71 71 82 85 958-14 64 65 70 69 69 6815-21 34 37 35 40 43 4222-28 16 15 15 15 21 1629-35 13 13 12 12 11 1236-40 9 7 9 7 4 8

206 208 212 225 233 241Per cent increaseov er co ntro l - - 0 '97 2-9 9-2 13"0 17"0

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212 Sushil Kumar, M. C. Jain, P. K. ChhonkarTABLE 3Periodic and Total Yields of Biogas (litres per kilogram dry weight) from Cow Dung Treated

with Different Forms of Carbon (5% w/w) in Batch DigestersPeriod Cow dung Cow dun g Cow dung Cow du ng Cow dung Cow dung(days) + + + + + alone

wood graphite petroleum c ar bo n activated (control)charcoal coke black charcoal

1-7 49.70 43.15 41'35 37-70 22.25 42"108-14 39'95 42.75 40'35 39-95 23.46 35"3015-21 22.90 21'25 23.80 23'95 43'89 17"7522-28 18'95 12-25 11'35 14.45 37-20 17"5029-35 14-70 11-95 11-80 11'50 14"15 14-6036-42 13.10 11.00 10"35 10.30 13.95 9"9043-49 10-80 10"60 9-35 9'55 12'85 9-1550-56 10"60 10.10 9"20 8-35 10'25 9"15Total 180.70 163'05 157.55 155"75 178.00 155.45

All the forms of carbon used were powdered.a Of local production.c o n d u c t e d t o s ee i f h i g h e r e f fi ci en c ie s o f g a s p r o d u c t i o n w e r e a c h i e v e d b yu s i n g o t h e r e as il y a v a il a b le f o r m s o f c a r b o n . A m o n g t h es e , p o w d e r e d w o o dc h a r c o al s h o w e d t h e m a x i m u m i n c re as e o f 1 6 % i n b io g a s p r o d u c t i o n(Table 3) .Semi-cont inuous fermentat ionS i nc e th e m a j o r i t y o f b i o g a s p l a n t s r u n o n s e m i - c o n t i n u o u s fe e d in g th e s es t u d i e s w e r e e x t e n d e d t o a s e m i - c o n t i n u o u s s y s t e m u s i n g a l a b o r a t o r yh o r i z o n t a l d i g e s t e r d e s c r i b e d e l se w h e r e (J a in & K u m a r , 1 98 6). T h e r e s u l t s( T a b l e 4 ) s h o w e d t h a t t h e b i o g a s y i e l d s f r o m c o w d u n g m i x e d w i t hD a r c o G 6 0 c h a r c o a l w e r e h i g h e r t h a n f r o m c o w d u n g a lo n e . T h e a v e r a g eg a s y i el d w a s 0 .2 m 3 p e r k i l o g r a m d r y w e i g h t f e d p e r d a y f r o m c o w d u n ga l o n e a n d 0 "27 m 3 p e r k i l o g r a m d r y w e i g h t f ed p e r d a y i n c o w d u n g a m e n d e dw i t h c h a r c o a l ( 3 4- 7% h i g h e r f r o m c o w d u n g m i x e d w i t h ch a r co a l) . A f t e r 4 0d a y s, w h e n n o c h a r c o a l w a s a d d e d t o t h e s e m i - c o n t i n u o u s fe r m e n t a t i o n , t h eg a s p r o d u c t i o n r e m a i n e d t h e s a m e .

T h e i n c re a se i n ga s p r o d u c t i o n c a u s e d b y t h e a d d i t i o n o f c h a r c o a l m a y b ea t t r i b u t e d t o e n h a n c e d m i c r o b i a l a c t i v i t y i n t h e d i g e s t e r c o n t r i b u t e d b yg r o w t h o f b a c t e r i a o n t h e s u r f a c e o f th e c a r b o n p a r t ic l e s ( A d a m s , 1 9 76 ). T h i sis c o r r o b o r a t e d b y t h e r e su l ts o f st u d i e s o n m i c r o b i a l p r o f il e s o f t h e d i g e s t er s( T a bl e 5 ) w h i c h s h o w e d t h a t t h e s l u rr y a m e n d e d w i t h c h a r c o a l h a d h i g h e rm i c r o b ia l n u m b e r s t h a n t h e u n a m e n d e d s lu rr y.

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Digestion with charcoal 213T A B L E 4

Average Daily Yields of Biogas Obtained from Cow Dung Alone and Cow Dung T r e a t e dwith Darco G 60 Charcoal (5% w/w) in a Semi-continuous System

Period (days) Gas production per d ay(li tres pe r kilogram dry weight o f cow dung fe d pe r day)Cow dung alone Cow dung amended with charcoal

1-5 32-0 36"86-10 42"4 72"011-15 134-4 180-816-20 220"0 262-421-25 243"2 358"426-30 198"4 284-031-35 203"2 292-036-40 a 215"2 272.841-45 207"2 263.246-50 212"8 269'651-55 202"4 276.056-60 197.6 273'6

a No charcoal was added after 40 days.The mean va lues o f some d iges t ion character i s t i cs dur ing f ermentat ion

a re gi v e n in T a b le 6 . T h e d e c o m p o s i t i o n o f V o l a t il e S o l i ds w a s 3 0 % a n d3 4 % a n d C O D r e du c ti o n w a s 5 5 % a n d 6 9 % i n t he c o w d u n g an d c o w d u n gmixed wi th charcoa l , respect ive ly . These va lues are in accordance wi th theg a s p r o d u c ti o n . T h e p H o f t h e a m e n d e d d i g e st i o n w a s s l ig h tl y h ig h e r th a nt h a t o f t h e c o w d u n g a l on e . V o l a t i le F a t t y A c i d c o n c e n t r a t i o n s w e r e w i t h i nthe acceptable l imits .

T A B L E 5Influence of Charcoal Addition of Total Anaerobic Bacteria and Cellulose HydrolysingBacteria ( x 104) in Semi-continuous Digester

Time o fsampling(days)

Anaerobic bacteria Cellulose hydrolysing bacteriaControl W ith Control W ithwithout charcoal without charcoal

charcoal charcoal10 117 151 27"5 35-520 106 132 32-0 52"030 147 160 40"0 76-040 176 197 55"5 56"0

T o t a l 546 640 155.0 219.5

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214 Sushil Kumar, M. C. Jain, P. K. ChhonkarT A B L E 6Process Parameters During Fermentation of Cow Dung Alone (A) and Cow Dung Treatedwith Charcoal (B) in the Semi-continuous Digester

D a ys % V S V F A C O D p Hdegradation (rag litre - 1) (mg litre- t)A B A B A B A B

0 -- -- 26 73 88 500 92 000 6"7 6-810 9'9 11-6 53 79 69 000 70 500 6"8 7"020 20'1 22"6 890 1 019 43 200 36000 7"4 7'130 24"7 27"2 572 660 41 600 32 800 7"6 7"840 30-1 34"3 730 571 39 600 28 600 7-4 7'6

The addition of powdered charcoal to an anaerobic digester is mostbeneficial in removing the slowly biodegradable organic materials. Thereadily biodegradable compounds are not adsorbed on activated charcoal(Hutto n, 1978). The higher pr oduc tion of biogas on addit ion of 5 % charcoalto cow d ung suggests a useful method for increasing the efficiency ofanaerobic digesters.

A C K N O W L E D G E M E N TThe authors are grateful to Dr N. N. Goswami, formerly Head of theDivision o f Soil Science and Agricul tural C hemistr y, for his keen interest inthe work and en coura gement and guidance. Than ks are also due to Shri V.Verma and Shri F. D. Ross for help in the laboratory work.

R EF ER ENC ESAdams, A. D. (1976). Powdered activated carbon improves anaerobic digestion.W a t e r S e w . W o r k s , July, 62-3.American Public Health Association (1975). S t a n d a r d m e t h o d s f o r t he e x a m i n a t i o no f w a t e r a n d w a s t e w a t e r (14th edn).Barker, H. A. (1956). B a c t e r i a l f e r m e n t a t i o n s , John Wiley & Sons, New York.Hobson, P. N. (1973). Microbiology of anaerobic treatment processes. P r o c e e d i n g so f F u n d a m e n t a l M i c r o b i o l o g ic a l A s p e c t s o f W a s t e T r e a t m e n t S y m p o s i u m ,

375-6.Hutton, D. G. (1978). Combined powdered activated carbon-biological treatment.In: C a r b o n a d s o r p t i o n h a n d b o o k (Cheremisinoff, Paul N. & Ellerbuch, Fred(Eds)), Ann Arbor Science Publishers Inc., Michigan 389-447.

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Digestion with charcoal 215Ja in , M . C. & K um ar, Sushi l (1986). Sem i-cont inuo us labo ra to ry d iges te r forbiogas studies, Research and Indus t ry , 31(3), 203-5.Ku m ar , Sushi l & Biswas, T. D . (1982). Biogas prod uc t io n f rom di f fe rent anim alexcreta . Indian J. agric. Sci . , 52(8), 513-20.M ah , R . A . & Susman , C . (1967) . M ic rob io logy o f anae rob ic s ludge fe rmen ta t i on .I. E n u m e r a t i o n o f t h e n o n - m e t h a n o g e n i c an a e r o b i c b a c te r ia , Appl . Micro-biology, 16, 358.M aki , L. R. (1954) . Ex per im ents in the m icrobio logy o f ce l lu lose deco m pos i t ion inmunic ipa l sewage , Anton ie van Leeuwenhoek , 20, 185.