6. Anaerobic Digestion

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<p>c</p> <p>ZURICH UNIVERSITY OF APPLIED SCIENCES</p> <p>RESEARCH ON ANAEROBIC DIGESTION OF ORGANIC SOLID WASTE AT HOUSEHOLD LEVEL IN DAR ES SALAAM, TANZANIA</p> <p>Bachelor Thesis</p> <p>by Lohri Christian Riuji Bachelor of Science 2005 Institute of Natural Resource Sciences 23.01.2009</p> <p>Supervisors Switzerland Prof. Dr. Urs Baier, Zurich University of Applied Sciences, ZHAW Yvonne Vgeli, Swiss Federal Institute of Aquatic Science and Technology, Eawag Department of Water and Sanitation in Developing Countries, Sandec Supervisors Tanzania Prof. Dr. Gabriel R. Kassenga, ARDHI University, Dar es Salaam Dr. Shaaban M. Mgana, ARDHI University, Dar es Salaam</p> <p>ImpressumKeywords Anaerobic digestion, ARTI Compact biogas system, biogas, solid waste management, organic solid waste, resource recovery, renewable energy, developing countries, Tanzania Suggestion for citation Lohri, C. (2009): Research on anaerobic digestion of organic solid waste at household level in Dar es Sala am, Tanzani a; Bachelor Thesis at ZHAW (Zurich University of Applied Sciences) in collaboration with EAWAG (Swiss Federal Institute of Aquatic Science and Technology) Address Christian Lohri, Stadelstrasse 23, 6048 Horw, Switzerland, E-mail: riu.lohri@gmail.com</p> <p>AbstractR a p i d u r b a n i s a t i o n a n d p o p u l a t i o n g r o wt h h a v e m a g n i f i e d t h e n e c e s s i t y f o r a d e q u a t e s o l i d wa s t e m a n a g e m e n t t h r o u g h o u t t h e wo r l d . I n o r d e r t o m i n i m i s e t h e r i s k t o t h e e n v i r o n m e n t and human health, economically feasible solutions are sought for the treatment of solid wa s t e , p a r t i c u l a r l y i n u r b a n a r e a s o f l o w- a n d m i d d l e - i n c o m e c o u n t r i e s . T h i s p a p e r e v a l u a t e s t h e s u i t a b i l i t y o f t h e A R T I C o m p a c t b i o g a s s ys t e m ( C B S ) a s a d e c e n t r a l i s e d l o w- t e c h t r e a t m e n t o p t i o n f o r t h e o r g a n i c f r a c t i o n o f h o u s e h o l d wa s t e i n D a r e s S a l a a m ( D S M ) , T a n z a n i a . A l i t e r a t u r e r e v i e w a b o u t s o l i d wa s t e a n d e n e r g y m a n a g e m e n t i n D S M wa s f o l l o we d b y t h e i n s t a l l a t i o n a n d m o n i t o r i n g o f a r e s e a r c h C B S wi t h t h e a i m o f o b t a i n i n g p r e c i s e d a t a c o n c e r n i n g t h e p e r f o r m a n c e o f t h e d i g e s t e r a s we l l a s q u a n t i t y a n d quality of the biogas and effluent. The unstirred floating-dome digester (capacity 850l, pH: 6 . 5 , T e m p . : 3 0 C ) wa s f e d wi t h t wo s u b s t r a t e s : F o o d wa s t e ( F W : 2 4 % T S , 9 1 % V S ) a n d m a r k e t wa s t e ( M W : 1 0 % T S , 8 8 % V S ) . T h e d a i l y l o a d o f 2 k g wa s t e ( d i l u t e d wi t h 1 8 l o f wa t e r ) wa s b a s e d o n l i t e r a r y f i n d i n g s a n d r e p r e s e n t s a r e a l i s t i c f i g u r e o f g e n e r a t e d wa s t e q u a n t i t y p e r T a n z a n i a n h o u s e h o l d o f 5 m e m b e r s . T h e r e d u c t i o n o f wa s t e v o l u m e ( F W : T S reduction by 84.9%, MW: TS reduction by 72.8%) and organic load (FW: VS reduction by 92.2% and COD reduction by 83.1%; MW: VS reduction by 85.3% and COD reduction by 8 4 . 2 % ) we r e s u b s t a n t i a l a n d i l l u s t r a t e t h e e f f e c t i v e n e s s o f t h e d i g e s t e r . T h r o u g h t h e a n a e r o b i c p r o c e s s , t h e a m m o n i a c o n c e n t r a t i o n ( N H 4 - N ) wa s r a i s e d b y 1 3 4 . 5 % t o 7 4 . 1 m g / l ( F W ) a n d 2 0 6 . 5 % t o 2 7 . 9 m g / l ( M W ) , wh i c h e n h a n c e s t h e u s e f u l n e s s o f t h e e f f l u e n t a s a n o r g a n i c f e r t i l i z e r . O n a v e r a g e , t h e a n a e r o b i c d i g e s t i o n o f f o o d wa s t e r e s u l t e d i n 6 4 0 l ( 5 7 4 N l ) b i o g a s p e r k g V S wi t h m e t h a n e c o n t e n t o f 5 6 . 8 % . 7 0 0 l ( 6 2 8 N l ) b i o g a s p e r k g V S wi t h 6 6 . 4 % C H 4 we r e p r o d u c e d f r o m m a r k e t wa s t e ( h yd r a u l i c r e t e n t i o n t i m e f o r b o t h f e e d s t o c k s : 4 2 . 5 d a y s ) . K i t c h e n wa s t e i n D S M c o n s i s t s o f a n e q u a l m i x o f t h e s e t wo s u b s t r a t e s a n d wa s f o u n d o u t t o p r o d u c e a p p r o x i m a t e l y 2 0 0 l o f b i o g a s wh i c h i s s u f f i c i e n t f o r 4 5 m i n o f cooking on a gas stove (equivalent to 1/3 of the daily cooking time per average househ o l d ) . A f a m i l y wi t h 5 m e m b e r s c a n h e n c e s a v e 2 8 k g o f c h a r c o a l p e r m o n t h s ( 2 3 0 0 0 T Z S ) wh i c h d e f i n e s t h e a m o r t i s a t i o n p e r i o d o f a C B S ( p r i c e 8 5 0 0 0 0 T Z S ) a s 3 y e a r s . An inspection tour to the 12 installed CBS at household level in DSM revealed that only 4 s ys t e m s we r e i n o p e r a t i o n . A l t h o u g h t h e c o n s e q u e n t i a l e f f o r t s b y A R T I - T Z r e s u l t e d i n a n i n c r e a s e t o 1 0 C B S b e i n g i n o p e r a t i o n 5 we e k s l a t e r , t h e s e f i n d i n g s u n d e r l i n e t h e i m p o r t a n c e o f a n a d e q u a t e f o l l o w- u p s t r a t e g y t o g u a r a n t e e a h i g h p e r c e n t a g e o f we l l m a i n t a i n e d ARTI Compact biogas systems. The final evaluation regarding the suitability of the CBS (technical, economical, environm e n t a l , s o c i o - c u l t u r a l a n d p o l i t i c a l , a s we l l a s s a f e t y a s p e c t s ) wa s a s s e s s e d a s g o o d . H o we v e r , a s t h e h i g h i n v e s t m e n t c o s t p r e s e n t s t h e h i g h e s t b a r r i e r f o r wi d e d i s s e m i n a t i o n of the ARTI technology in Tanzania, economical adjustments should be taken into consideration. This study includes various recommendations regarding technical adaptations, o p e r a t i o n a l e n h a n c e m e n t s , r e b a t e s ys t e m a n d a f t e r - s a l e s s e r v i c e s .</p> <p>ZusammenfassungA n h a l t e n d e V e r s t d t e r u n g u n d s t a r k e s B e v l k e r u n g s wa c h s t u m v e r s t r k e n we l t we i t d i e D r i n g l i c h k e i t f r e i n e a n g e m e s s e n e A b f a l l wi r t s c h a f t ( S o l i d W a s t e M a n a g e m e n t ) . U m d i e R i s i k e n f r U m we l t u n d G e s u n d h e i t z u m i n i m i e r e n , we r d e n s p e z i e l l f r u r b a n e Z e n t r e n i n E n t wi c k l u n g s l n d e r n z u n e h m e n d a l t e r n a t i v e L s u n g e n z u r s i n n v o l l e n A b f a l l b e h a n d l u n g gesucht. D i e v o r l i e g e n d e A r b e i t b e u r t e i l t d i e E i g n u n g d e s A R T I C o m p a c t B i o g a s S ys t e m s a l s d e z e n t r a l e l o w- t e c h M g l i c h k e i t , d e n o r g a n i s c h e n A n t e i l v o n H a u s h a l t s a b f l l e n i n D a r e s S a l a a m (DSM), Tansania zu behandeln. Einer Literaturstudie ber Energieverbrauch und Abfallwi r t s c h a f t i n D S M f o l g t e I n s t a l l a t i o n , B e t r i e b u n d b e r wa c h u n g e i n e r A R T I F o r s c h u n g s a n l a g e . Z i e l d a b e i wa r , p r z i s e D a t e n z u r E f f i z i e n z d e r A n l a g e z u g e n e r i e r e n , A u s s a g e n z u r Menge und Zusammensetzung des produzierten Biogases zu ermglichen und die Qualitt des Effluents zu bestimmen. Der ungerhrte, floating-dome Fermenter (Kapazitt 850l, pH: 6 . 5 , T e m p : 3 0 C ) wu r d e m i t z we i S u b s t r a t e n g e f t t e r t : S p e i s e - A b f l l e ( S A : 2 4 % T R , 9 1 % oTR) und Markt-Abflle (MA: 10% TR, 88% oTR). Die tglich zugefhrte Abfallmenge von 2kg (verdnnt mit ca.18l Wasser) reprsentiert eine realistische Abfallmenge pro 5k p f i g e n H a u s h a l t . D i e R e d u k t i o n d e s A b f a l l v o l u m e n s wa r b e t r c h t l i c h ( S A : T R - A b n a h m e um 84.9%, MA: TR-Abnahme um 72.8%), ebenso verdeutlicht die Reduktion des organischen Anteils (SA: oTR-Abnahme um 92.2%, CSB-Abnahme um 83.1%; MA: oTR-Abnahme um 85.3%, CSB-Abnahme um 84.2%) die Wirksamkeit der Anlage. Aufgrund der anaeroben Vergrung stieg die Ammoniumkonzentration (NH4-N) um 134.5% auf 74.1mg/l (SA), resp. u m 2 0 6 . 5 % a u f 2 7 . 9 % ( M A ) , wa s e i n e v e r b e s s e r t e D n g e q u a l i t t a u f g r u n d r a s c h v e r f g b a rer Pflanzennhrstoffe darstellt. Durchschnittlich resultierte aus der Vergrung der SpeiseAbflle 640l (574Nl) Biogas/kg oTR, bei einem Methangehalt von 56.8%. Die Vergrung der Markt-Abflle ergab eine Menge von 700l (628Nl) Biogas/kg oTR mit einem CH4-Anteil von 6 6 . 4 % . D i e A u f e n t h a l t s z e i t b e t r u g b e i b e i d e n S u b s t r a t e n 4 2 . 5 T a g e . E i n g l e i c h we r t i g e s G e m i s c h d i e s e r z we i S u b s t r a t e e r g a b e i n e u n g e f h r e G a s p r o d u k t i o n v o n 2 0 0 l i n D S M , wa s e i n e r K o c h d a u e r v o n 4 5 m i n a u f e i n e m G a s h e r d e n t s p r i c h t . D i e s wi e d e r u m e n t s p r i c h t 1 / 3 der durchschnittlichen Kochzeit eines tansanischen Haushalts pro Tag. Eine 5-kpfige Fam i l i e k a n n d a h e r 2 8 k g H o l z k o h l e p r o M o n a t e i n s p a r e n ( 2 3 ' 0 0 0 T Z S ) , wa s e i n e A m o r t i s a t i onszeit der ARTI-Anlage (850'000 TZS = ca.550 ) von 3 Jahren ergibt. Die Besichtigung von 12 installierten ARTI-Haushaltsanlagen in DSM deckte gravierende U n t e r h a l t s m n g e l a u f : N u r 4 d e r A n l a g e n wa r e n i n B e t r i e b . D i e n a c h f o l g e n d e n A n s t r e n g u n gen von ARTI-TZ verfehlten die angestrebte Wirkung nicht: 5 Wochen spter stieg der Anteil der funktionierenden Anlagen auf 10. Trotzdem verdeutlichen diese Resultate, dass eine angemessene Nachverkaufsuntersttzung unbedingt erforderlich ist. Die Schlussbeurteilung der ARTI-CBS Eignung beinhaltet technische, konomische, kolog i s c h e , s o z i o k u l t u r e l l e u n d p o l i t i s c h e K r i t e r i e n s o wi e S i c h e r h e i t s a s p e k t e u n d e r g a b e i n positives Resultat. Nichtsdestotrotz sollten konomische Anpassungen ins Auge gefasst we r d e n , d a d i e h o h e n I n v e s t i t i o n s k o s t e n d a s H a u p t h i n d e r n i s f r e i n e we i t e V e r b r e i t u n g d e r Technologie darstellen. Die Arbeit listet abschliessend Empfehlungen auf bezglich techn i s c h e n A n p a s s u n g e n , U n t e r h a l t s b e t r i e b , R a b a t t s ys t e m u n d K u n d e n d i e n s t .</p> <p>Table of ContentsAbstract ........................................................................................................... 1 Zusammenfassung............................................................................................. 1 Abbreviations ................................................................................................... 1 1 1.1 1.2 1.3 2 2.1 Introduction .............................................................................................. 1 General Background .................................................................................... 1 Objectives .................................................................................................. 2 Methodologies ............................................................................................ 2 Background Information ............................................................................. 3 Tanzania .................................................................................................... 3 2.1.1 2.1.2 2.1.3 2.1.4 2.1.5 2.1.6 2.1.7 2.1.8 2.2 General facts and figures ................................................................... 3 Dar es Salaam .................................................................................. 3 Solid waste management in Dar es Salaam ............................................ 4 Energy management........................................................................... 7 Deforestation and Health .................................................................... 8 Fertilizer demand .............................................................................. 9 History of domestic biogas dissemination in Tanzania ............................. 9 Policy and plans in regard to biogas................................................... 10</p> <p>Anaerobic Digestion .................................................................................. 11 2.2.1 2.2.2 2.2.3 2.2.4 Biological process ........................................................................... 11 Substrates/Feedstock ....................................................................... 12 Biogas ........................................................................................... 13 Effluent .......................................................................................... 15</p> <p>2.3</p> <p>ARTI Compact Biogas System ..................................................................... 16 2.3.1 2.3.2 2.3.3 ARTI-TZ ......................................................................................... 16 Design and Technology of ARTI Compact Biogas System ....................... 16 Dissemination and costs ................................................................... 17</p> <p>3 3.1</p> <p>Materials and Methods ............................................................................. 19 Research-plant at ARDHI University ............................................................. 19 3.1.1 3.1.2 3.1.3 3.1.4 3.1.5 3.1.6 Installation ..................................................................................... 19 Feedstock and feeding plan .............................................................. 20 Monitoring of digester activity ........................................................... 24 Gas measurements .......................................................................... 24 Effluent .......................................................................................... 26 Calculations ................................................................................... 27</p> <p>3.2</p> <p>Inspection of ARTI plants in DSM ................................................................ 30 3.2.1 3.2.2 Analysed parameters........................................................................ 30 Interviews ...................................................................................... 30</p> <p>4 4.1</p> <p>Results ................................................................................................... 31 Research-plant at ARDHI University ............................................................. 31 4.1.1 4.1.2 4.1.3 4.1.4 4.1.5 4.1.6 4.1.7 Influence of enhanced feeding procedure on process stability ................ 31 Stratification inside digester in terms of TS, VS and COD ..................... 33 Intense monitoring of VFA, alkalinity and A/TIC ...................</p>

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