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omestic and industrial w a s te m a n a g e m e n t is
n o w a critical issue for A fric a n governments
because of high urban population growth.
In this context, a pilot waste processing operation to
r e c y c l e s o l i d s l a u g h t e r h o u s e b y - p r o d u c t s w a s
l a u n c h e d in 1 9 8 7 a t T h iè s b y the S e n e g a l e s e
S o c i é t é d ' e x p l o i t a t i o n d e s re s s o u rc e s a n i m a l e s
(SERAS) in colla bora tion with Agriforce, an economic
interest g r o u p a ffilia te d w ith the French C entre de
c o o p é r a t i o n i n t e r n a t io n a le en r e c h e rc h e a g r o n o
m i q u e p o u r le d é v e l o p p e m e n t ( C I R A D ) . T h e
Transpaille system is used to recycle these solid by
p ro d u c ts a n d b l o o d , thus p r o d u c i n g b i o g a s a n d
c o m p o s t . This c o m p o s t is b e i n g tested fo r b l o c k
p r o p a g a t i o n o f plants a n d the liq u id w a s te s a re
p u r ifie d b y a l a g o o n i n g t e c h n iq u e . An e c o n o m i c
assessm ent o f the Thiès o p e r a t i o n w i l l d e te r m in e
whether the project could be extended to the Dakar
slaughterhouse to reduce the pollution of Hann Bay.
Transpaille: energy
;
fertilization, cleansing
J.-L. FARINET
Agriforce, unité de recherche gestion de l'eau
Illustrated diagram of the Transpaille unit at Thiès BP 5 0 3 5 , 34 0 3 2 Montpellier cedex I , France
(all rights reserved for all countries). Tel. : (33| 6 7 61 7 4 2 4 Telex : 4 8 5 5 0 7 F Fax: (33) 6 7 61 71 6 0
T
he Transpaille procedure was designed by CIRAD and deve loped by Agriforce for organic waste recovery and processing using m e t h a n e f e r m e n t a t i o n ; gas and compost are produced.T h e s iz e o f t h e d i g e s t o r a n d peripheral e q u ip m e n t o f the system can be modified according to needs. T h e s e tu p at T h iè s c o n s is ts o f a 4 0 m 3 h o r i z o n t a l c y l i n d e r . T h e wastes are fed and the ferm entation effluents are discharged mechanical ly. The system is controlled through a hydraulic station, and the digestor is h e a te d b y m e a n s o f an i n t e r n a l circuit.
The n o m in a l c a p a c ity o f the Thiès slaughterhouse is 2 000 t per annum
o f c a rc a s s . T h is p r o d u c e s 4 8 0 t ( t o n n e s ) o f w a s t e w h i c h c a n be c o n v e rte d in to 55 t per a n n u m o f compost, and 35.5 m3 per day of biogas at an average processing temperature of 31 °C.
The bio gas is stored in tw o 30 m 3 PVC gas containers w h ic h fuel a b io gas 20 kVA, 3 000 rpm power gene rating unit. This unit provides power for the slaughtering line in the m o r ning and the refrigeration units in the afternoon. Moreover, the power unit is e q u ip p e d w it h a h eat r e c o v e r y system w h i c h makes it possible to m a in t a in the d ig es tor te m p e ra tu re a b o v e 3 0 ° C y e a r - r o u n d . T w o c oncrete c om post-ageing tanks are installed at one end o f the digestor cylinder.
Development
of Transpaille units
A Transpaille unit was installed at a slaughterhouse in N'Djamena (Chad) and became operational in |une 1994. This 20 m3 capacity unit produces hot water compost, which is sold to market gardeners.
The Transpaille anaerobic digestion technique is used to process slaughte rhouse wastes and was also developed for energy and compost production in rural African communities. In addition, a small-scale unit (3.5 m3) was desi gned to produce biogas for domestic use; this could provide a substitute for fuelwood in heavily deforested areas. Twelve of these small-scale units are currently being tested and showcased in three village in the Senegal River delta region.
In Mali, a 50 m3 capacity Transpaille unit is being built on an NGO experi mental farm. The biogas produced will provide energy to pump about 9 000 m3 of w ater w e e k ly to irrigate fru it orchards. The compost produced will be used to make a culture medium for plant nurseries.
M ore s p ecific a p p lic a tio n s of the technique are also being investigated. For instance, studies are under way in M exico on coffee pulp digestion in collaboration with a growers coope rative; in Brazil, a pilot research project should begin in 1995 to apply the technique for processing waste from a cassava industry.
From 1988 to 1989, this p ro je c t in Senegal was jo in tly funded by:
- SERAS; - GIE Agriforce;
- the French Agence de l'environne ment et de la maîtrise de l'énergie (ADEME);
- the French ministère de l'environnement;
- the French ministère de
la coopération et du développement (Fonds d'a ide et de coopération).
M arketing com post as
seedling nursery blocks
J.-L. F A R IN E T
I
n 1 99 0, m a rk e t g a r d e n in g was c a r r ie d o u t on an e s t i m a t e d 19 0 0 0 hectares (ha) o f land in Senegal, m ainly in the Niayes zone. There w ill probably be further vege table crop extensions in the c om ing years because of recent crop diversi f ic a t io n a ro u n d the Senegal River and the planned Cayor Canal. Local markets w i l l n ot be able to absorb this increased vegetable production, w h i c h c o u ld be c le a re d on w o r ld markets.Senegalese m a rk e t g arde ne rs w i l l therefore first have to solve several specific problems:
- c o n t r o l l i n g soil f e r t i l i t y th ro u g h b a la n c e d inputs o f o rg a n ic m atter and mineral fertilizers;
- in tro d u c tio n o f high perform ance hybrid plant varieties;
- adapted techniques to make o p t i m um use o f the p o te n tia ls o f each plant variety.
It is always d iffic u lt to keep up che mical and biological fertility in c u lti vated soils, particularly in the tropics where organic matter mineralization is accelerated. O rganic soil a m e nd ments are thus required. In Senegal, m arket gardeners t r a d i t i o n a l l y use groundnut powder, fish waste, horse and d o n k e y m a n u r e , and p o u lt r y m anure w h ic h are high in nitrogen and phosphorus.
G rou nd nu t powder is an oil mill by p r o d u c t c o m p o s e d o f d e g r a d e d g roundnut shells and haulms mixed w ith sand. Compost obtained by pro
cessing slaughterhouse wastes is a n e w h ig h q u a li t y o rg a n ic m a n u re (T a b le 1), t h a t is c u r r e n t l y b e in g tested.
Slaughterhouse
compost
The Transpaille digestor installed at the Thiès slaughterhouse can process 4 8 0 t per a n n u m o f s o lid w astes, pro ducin g 13 000 kW h of electricity and 55 t of compost.
T h is c o m p o s t is a g o o d o r g a n i c manure, as shown by the results of tests c a r r ie d o u t at the C e n tre de d é v e l o p p e m e n t h o r t i c o l e de C a m b é rè n e (Senegal) w h i c h h ig h lighted its beneficial effects on soil fertility. However, the costs of produ cing this compost are higher (42 CFA f r a n c s / k g [ g r . w t . ] ) t h a n fo r o t h e r co n v e n tio n a l manures. In a dd itio n,
Melon plants in soil blocks after 1 6 days in the nursery. P hoto Y. H u rv o is
m a r k e t g a r d e n e r s p r e f e r to b u y g r o u n d n u t p o w d e r at 15 CFA francs/kg (gr.wt.). A market survey in the vegetable growing region revea
led that c o m p o s t from Thiès co u ld not be sold fo r higher than 30 CFA francs/kg (gr.wt.). In this price range, enhancement of raw compost is not co s t-e ffe c tiv e w it h the T ra n s p a ille system. It w il l thus be necessary to market this product in sectors where its q u a li t i e s are s u it a b le , such as n u rs e ry p la n t b lo c k p r o p a g a t io n ; enhancement and profits could then be discussed.
Table 1. Comparison of compost produced at the Thiès slaughterhouse with a French-type compost (an average of 43 unenriched organic manures; test n° 105 b, magazine 50 millions de consommateurs, 1979).
Type PH OM (%) N (%) P2O 5 (%) K2O (%) CaO (%) MgO (%) Thiès compost Average 7.7 52.1 2.0 2.4 0.9 3.5 0.7 French compost 5 to 8 30.0 1.6 1.5 1.4
;
0.4Elements compared: acidity (pH), levels (%) of organic matter (O M ), nitrogen (N), phosphorus (P2O5), potassium (K2O), calcium (CaO) and magnesium (MgO).
A new product
S o il b lo c k s a re w i d e l y used in European nurseries for propagating v e g e ta b le and f l o w e r p la nts . T his b lo c k p ro p a g a tio n t e c h n iq u e p r o vides protection for the germinating seed and then the seedling during the initial 4-week growth period. This is of a gron om ic interest since healthy and hardy plants can be p ro du ced w i t h a h ig h g r o w t h success a fte r transplanting. This means that mar ket gardeners can cut costs in their seed purchases, w it h a substantial labour reduction. The advantages of t h is t e c h n i q u e c o n s i d e r a b l y o u t w eig h the increased price incurred by the in d ire c t o rg an ic matter sup ple ment in the soil blocks (approxi mately 2 t o f dry matter/ha).
Production
A set o f experiments was carried out to develop a high performance c o m post-based growth m edium (Fig. 1). The goal was to determ ine a means o f easily p ro du c in g soil blo cks that w o u l d s ta nd up to w a t e r i n g and a ll o w goo d seed g e r m in a tio n and seedling development. The resulting form ula is 75% com post/25% sand. Soil blo ck performance was enhan ced by th e a d d it io n o f a fu n g ic id e and w a t e r - r e t a i n i n g p r o d u c t. The technique involves moderately c o m pressing the soil mixture m anually or m ech an ica lly into small cubes. The size of these soil blocks varies accor ding to the plant species to be propa gated, e.g. 4 cm cubes for small-seed species (tom ato, cabbage, pepper) and 6-7 cm for large-seed species (melon, cucumber).
Marketing
It is essential to first d e te rm in e the features of the seedling nursery block market before d ev e lo p in g a m arke ting strategy. The potential customers are p rim a rily w e ll-e q u ip p e d market gardeners. Hybrid seeds are used for export crops and therefore the crop- p in g t e c h n i q u e s m u s t be f u l l y c o n tr o lle d . These soil b lo c k
custo-Figure 1. Schematic diag ra m of seedling nursery block production at the Thiès (Senegal) slaughterhouse.
mers require a to p q u a lity p ro d u c t and service, inv o lv in g plant protec tion, varietal purity, "field-side" d eli v e ry , and t e c h n i c a l s u p p o r t u n til crop harvest in some cases.
From a c o m p e titiv e v ie w p o in t , the o n ly other nursery vegetable plants c u r r e n t ly a v a ila b le in Senegal are g r o w n on im p o r t e d p e a t and th e p r ic e s are p r o h i b i t i v e ( 1 5 0 CFA francs/kg [gr.wt.]).
The p ro spe cts are th e r e f o r e q u ite p r o m is in g fo r th e d e v e lo p m e n t o f b lo ck propagated plants, but SERAS (whose p ro d u c tio n is n o w a n im a l- based) w i l l have to d iv e r s ify th e ir activities.
Selling price
In 1990, in the Thiès region, com pe t i t o r s w e r e s e l l i n g s e le c t e d ,
W a s t e p ro c e s s in g
non-hybrid varieties of "bare rooted" v e g e ta b le p la n ts at a b o u t 15 CFA francs/plant. The cost of pro ducin g a vegetable plant in a soil block, w ith field-side delivery, is estimated to be 12 CFA francs, at an average seed p ric e o f 3 CFA francs. The g ro w th m e d iu m p ric e increases c o n c o m i tantly w ith the seed price. The block p ro p a g a tio n te c h n iq u e is therefore e s s e n t i a l l y used to g r o w h ig h y i e l d i n g h y b r i d s . Su ch s e e d li n g n u r s e r y b lo c k s c a n be s o ld f o r 20 CFA francs/plant for a net profit of 8 CFA francs.
W h e n the T ranspaille system at the Thiès slaughterhouse is operated at nominal capacity, 1.5 m illio n plants per annum could be produced. They w o u ld be s upplied to customers in three 500 000 plant batches to allo w for compost ageing. Each transplan ted b atch c o u ld c o v e r a 1 2-25 ha surface area, depending on the plant species.
At the Thiès site, SERAS is currently p ro d u c in g rea dy-to -p la nt vegetable seedlings that are just being sold to sm allhold ers. H ow e v er, large-scale v e g e tab le p ro d u c e rs o ffe r a n o th e r more profitable market w h ic h should be exploited.
Tomato plants in soil blocks after 20 days in the nursery.
Photos Y. Hurvois
5-6 m illio n plants per annum could be produced by u tiliz in g the results of the Thiès slaughterhouse study at a larger capacity slaughterhouse such as that of Dakar. The increased pro duction could be sold to large priva te market gardeners.
Compost
production cost
analysis
Profits derived through treatm ent of solid slaughterhouse wastes depend on the extent to w h ic h the produced c o m p o s t is refin ed . A t the o rg a n ic m anure stage, processing costs are estimated to be 1% o f the slaughte ring fee charged by SERAS. The p o l lu tio n p ro b le m can thus be solved quite cheaply at this recycling stage. SERAS could expect to generate pro fits by c re a tin g a se e d lin g nursery block sector. Processing costs for this
final stage in the profitable utilization o f c o m p o s t w o u l d c o r r e s p o n d to 2 0 .3 % o f the slaughtering fee. The slaughterhouse can also market the compost between these tw o stages as a bulk growth m edium for a profit of around 6% o f the slaughtering fee. V e ry lit t l e s p e c ia liz e d e q u ip m e n t o r s k ille d staff are re q u ire d at this intermediate stage.
The head o f the slaugterhouse can choose a compost p ro du c tion stage to m ee t his e c o n o m ic m eans and objectives. Regardless o f the choice, the slaughterhouse environm ent w ill be markedly improved by this means of p ollution and odour control.
W a s te p ro c e s s in g
Lagooning, a water
purification technique
for the tropics
J.-L. FARINET and Y. COPIN
A
lag o o n in g te c h n iq u e is used f o r w a t e r p u r i f i c a t i o n at a s l a u g h t e r h o u s e in T h iè s ( S e n e g a l). T h e u n i t m e e ts t w o objectives:- purification o f liq uid slaughterhou se wastes;
- testing the performances o f d if fe rent lagooning techniques in actual operational conditions.
The lagooning
principle
Lagooning reproduces the process by w h ic h water purifies itself b io log ica l ly, and accelerates and controls the p h e n o m e n o n . T h e p ro c e s s o fte n involves irrigating waste w ater and a llo w in g it to stand in a sedimenta tion basin. Organic matter is d ecom posed by bacteria, producin g water, c a rb o n d io x i d e and m in e ra l salts. These elements are then taken up by algae. The performance of this p ro cess is e n h an c ed at high te m p e ra tures, and it can be co m b in e d w ith th e T ra n s p a ille system in o rd e r to make optimal use o f the biomass that develops in the basin. The technique is used w i t h s u c c e s s in s o m e European slaughterhouses and, since it is o p tim a l at 25-35°C, co u ld cer ta in ly be adapted to operate under tropical African conditions. The pro cess is q u i t e r u s tic and t h e r e f o r e should be in line w ith the budgetary
constraints of slaughterhouse indus tries. Management and maintenance o f the equip ment and installations do not require skilled staff, the operating costs are lo w and, under anaerobic c o n d i t i o n s , t h e r e is no e n e r g y c o n s u m p t i o n . In c o n t r a s t , s o m e l a g o o n i n g t e c h n i q u e s r e q u i r e mechanical aeration.
S la u g h te r h o u s e s are o fte n set up a r o u n d u rb a n c e n tre s on e n o u g h land to a llo w construction of lagoon basins (i.e. lagoons).
Technical choices
There are several possible lagooning techniques for purification o f p o llu ted waters. Applications vary accor d in g to th e w a s te w a t e r ty p e and
lo a d , th e p h y s ic a l and e c o n o m ic e n v i r o n m e n t near the in s t a lla tio n and th e d eg re e o f w aste r e fin in g . L a g o o n in g can also be c o m b in e d w it h c o n v e n t io n a l in s t a lla tio n s in order to lim it land use and enhance microbial elim in atio n.
The Thiès lagooning
station
A t T h iè s , t h e b l o o d a n d r u m e n contents can be collected im m edia t e ly after a n im a ls are slaughtered. These wastes are then processed in a digestor by the Transpaille procedure to produce biogas and compost.
The liq uid effluents are derived from washing the slaughtering areas and f l o o r s , h id e p r o c e s s i n g , s e w a g e (toilets, showers) and rainwater.
The average waste w a te r o u tp u t is 10 m 3/d ay. C onsiderable variations were noted in the p ollution indicator results, e.g. suspended solids (SS), c h e m ic a l o x y g e n d e m a n d (C O D ) and a m m o n i a n it r o g e n ( N - N H 4), c o n c e r n i n g t h e s l a u g h t e r h o u s e effluents (Table 1 ).
Agriforce and the French Centre de r e c h e r c h e s de M è z e - H é r a u l t (CEREMHER) are c o ll a b o r a t i n g to d e v e lo p a lagooning system for the Thiès slaughterhouse. The e n v iro n mental conditio ns (especially clim a te), type of soil and performance spe cifications determined by SERAS and Agriforce were taken into considera t i o n in d e v e lo p i n g th e la g o o n in g t e c h n i q u e a n d d e c i d i n g on th e equipment design limitations. In this
Pistia stratiotes plants from the lagoon with
macrophytes.
Photo Y. H urvois.
project, several requirements have to be met: low investment, lo w energy c o n s u m p t i o n , and p r o d u c t i o n o f plant m aterial fro m the lagoons to compensate for variations in the raw m a te r ia l s u p p ly f o r th e d ig e s t o r . Figure 1 shows a schematic diagram o f the p ro c e d u r e , w h i c h in c lu d e s p re tre a tm e n t, a d e c a n te r/d ig e s te r and th ree lagoons (L-i, L2 and L3). The features of the lagooning station and retentio n tim es in each e q u ip ment unit are given in Table 2.
The different units
P r e t r e a t m e n t r e t a i n s th e gro ss solids and floating matter. A degrea sing/screening tank, divided into four
compartm ents separated by screens and metal plates, has been added to the existin g cesspool. Pretreatment reduces the SS and C O D levels by 30%.
The d e c a n te r/ d ig e s te r is a s im p le c y l i n d r i c a l ta n k d iv i d e d in t o t w o compartments that operate in parallel. D u e to its sm all d ia m e te r, a t h i c k crusty layer is formed on the surface w h ic h reduces odours. This primary a na erob ic process can be upset by marked o utput variations, but works w ell w ith heavy loads. This step fur ther reduces the C O D by 6 0 % and the SS by 80%.
The secondary waste water treatment takes place in three different lagoon
Table 1. Elimination of pollution loads in waste waters from the Thiès slaughterhouse (February 1990). Pollution indicators (mg/l) Slaughterhouse outlet Lagoon outlet Elimination (%) SS 6 000 350 94 Soluble COD 2 900 250 91 n-n h4 300 5 98
SS : suspended solids; C O D : chemical oxygen demand; N -N H4: ammonia nitrogen
Practical
adaptations
The Thiès lagooning station is the first water purification installation designed for a slaughterhouse in western Africa. It is based on European slaughterhouse waste water processing techniques, w h ic h were adapted to fit A frica n conditions. Indeed, simple solutions were found for some technical pro blems caused by seasonal changes and load variations, etc.
A macrophyte-based aeration system enables the development of aerobic bacteria w h ic h help to decompose solids in waste overload situations, and during the cool rainy seasons when there is little sunlight. A biogas genera tor can be used as a power supply for this low-power aerator, thus reducing energy costs.
M ud b u ild u p aro und the roots of macrophytes {Pistia stratiotes) near the lagoon outlets can kill these plants. The problem can be solved by concentra ting the macrophyte crop in these parts of the lagoon to keep the biomass at the peak growth phase.
Effluent D e g re a s in g /s c re e n in g tank Pretreatm ent
D e c a n te r/d ig e s te r
Figure 1. Schematic diagram of the waste water processing system at the Thiès slaughterhouse.
basins: a natural lagoon w ith m ic ro phytes and tw o subsequent lagoons w ith macrophytes. Effluents from the decanter/digester flo w by gravitation into the first lagoon (L-|). During the natural lagooning stage, microphytes (micro-algae) d e v e lo p by a s s im ila t i n g th e p o l l u t i n g e le m e n ts . T h is leads to a drop in pollution to levels that are acceptable for m acrophyte g r o w t h , i.e. N - N H 4 is re d u c e d by more than 60%. The lagooning stage w ith macrophytes involves one main lagoon (L2) and a secondary lagoon (L3) in series. They are covered with
Pistia s tra tio te s (w a te r le ttu c e ), a
c o m m o n r a p id ly and easily g ro w n plant species in Senegal, w h ic h has the effect of concentrating the water pollution. These plants are then c o l lected and used in th e T ra n s p a ille sy s te m to p r o d u c e e n e r g y and co m p ost. The c o m p o s t is e n ric h e d w ith minerals (particularly nitrogen) extracted from the waste waters.
Table 2. Features of the lagooning station and retention times.
Pretreatment Decanter Lj Lagoon L2 Lagoon L3 Lagoon
tank digester Volume (m3) 5.5 4.0 225 79 37 Depth (m) - 2 1.2 0.5 0.5 Surface area (m2) - 2 0 250 168 84 Retention 2.2 h 4 d 22 d 1 0 -1 2 d 8-1 Od times (h or d)
Maintenance
The lagoons are maintained by a quarter time employee. There are regular duties to be done. On a daily basis, this worker removes all floating matter from the pre processing tank, removes any accumu lated grease from the Lj lagoon, collects four-six wheelbarrows of water lettuce from the L2 and L3 lagoons and takes them to the Transpaille digestor. On a weekly basis, the pretreatment tank is cleaned and the crust is scraped off the top of the digester.
The main waste water in flo w canal is cleaned monthly.
The lagoons have to be cleaned every 5 years and the sediments are then loaded into the Transpaille digestor.
There is a hydraulic system of locks to adjust (in parallel or series) waste water levels in the lagoons from full to empty. Experiments and cleaning c a n th u s be c a r r i e d o u t w i t h o u t having to shut d ow n the entire ope ration.
Economic aspects
The design of a lagooning station w ill depend on the site. Investment costs v a r y , and s o il p r e m e a b i l i t y is an im p o r ta n t d e te rm in in g fa c to r. The costs incurred at the Thiès installa tion (8.1 m illio n CFA francs) cannot be sim p ly extrapolated and applied to othe r slaughterhouses since it is only a small-scale experimental unit.
The constant effluent load variations at th e sm all T hiè s s la u g h te rh o u s e c o u l d be t h e w e a k p o i n t o f t h is small-scale lagooning system.
An installation b uilt to handle m axi m um loads could, however, require c o n s i d e r a b l e e x tra e x p e n d it u r e s . An alternative w o u ld be to divert part o f th e e f f lu e n t s d u r in g h ig h - l o a d periods to an agricultural/water p uri fication plot.
Annual depreciation charges for the l a g o o n i n g u n i t is 4 0 0 0 0 0 C F A francs, over a term o f 3 years for the stock, 10 years fo r th e e q u ip m e n t
and 25 years fo r c i v il e n g in e e rin g costs fo r all construction and deve lopment work.
Total lagooning expenses can be up to 550 000 CFA francs per annum , i n c l u d i n g 150 0 0 0 CFA francs fo r o p e ra tio n s and m a in te n a n c e . The water purification cost has been esti mated at 735 CFA francs/t o f carcass, or 2.4% of the slaughter fee charged b y SERAS f o r an a v e ra g e o v e r a l l sla u g h te r rate o f 750 t per a n n u m of carcass.
Efficiency, prospects
The overall cleansing objectives can be met w ith this lagooning technique since the p ollution indicator c oncen trations are reduced by at least 90% over 1.5 months. The w ater is p u ri fied enough to be used for the first hide washing, but it cannot be used to wash d ow n the animal carcasses. This represents a substantial savings for the slaughterhouse since w ater costs are high in Senegal. Full water recycling w ill require further studies and e x p e n s iv e a d d it io n a l in s t a lla tions.
Moreover, the results w ith the lagoo ning system at Thiès showed a mar ked 50-60% decrease in the effluent load potential. This means a p o llu tio n re d u c tio n o f m o re th a n 9 5 % , w h ic h is taken into consideration in pollution tax calculations.
A g r o n o m ic s tu die s c o u ld n o w be conducted on the cleansing capacities
of cultivated soils, and it w o u ld also be interesting to assess water utiliza tion in dry zones. The results o f the experiments carried out at Thiès w ill be very useful for d ev e lo pin g other processing units. However, if a new c o n c e p t is d e v e lo p e d w h i c h is as e c olog ic al, sim ple and inexpensive as lagooning, it should be kept in mind that different specific conditions are fo u n d at each slau gh te rh ou s e and t h e y s h o u ld be f u l l y a n a ly s e d to obtain the best performance.
References
Proceedings of the workshop "Valorisation a g ro é n e rg é tiq u e des déchets d 'a b a t t o ir en z o n e t r o p i c a l e " , N o v e m b e r 1 9 9 1 , T hiès, Senegal. CIE Agriforce, SERAS, AFME, French ministère de la coopération et du développement, 118 pp.
FAR IN ET J.-L., H U R V O IS Y., 1 9 9 1 . Valorisation et épuration des déchets d'abat t o ir au Sénégal. F ina l r e p o r t 1 9 8 9 - 1 9 9 1 . CIRAD, Montpellier, France, 90 pp.
FARINET J.-L., HURVOIS Y., FOREST F., 1991. Waste management and processing for energy, organic fertilizer and pollution control in a tropical slaughterhouse. In 7lh European Conference "Biomass for energy, industry and e n v iro n m e n t", Athens, Greece, 22-26 A p ril 1991. CIRAD-CA, Montpellier, France.
FARINET J.-L., FOREST F„ HURVOIS Y., 1991. Etude de la c o m m e rc ia lis a tio n d 'u n c o m p o s t de déchets d 'a b a tto ir au Sénégal. Final report, French ministère de la recherche et de la technolo gie , Agriforce, M ontpellier, France, 27 pp. + 4 annexes.
W a s t e p ro c e s s in g
Abstract... Resumen... Résumé
J.-L. FARINET - Transpaille: energy, fertilisation, cleansing.
Designed by CIRAD (Centre de coopération internationale en recherche a g r o n o m iq u e p o u r le - d é v e lo p p e m e n t ) an d developed by Agriforce, the Transpaille procedure is used for the rec o v e ry an d processing of o rg a n ic w astes using methane fermentation; gas and compost are produced. The system was installed at the slaughterhouse in Thiès, Senegal, in 1 9 8 8 - 1 9 8 9 . It consists of a 4 0 cubic m eter horizontal cylinder. The slaughterhouse produces 4 8 0 metric tonnes of waste per ye ar which can be converted into 55 tonnes of compost per year and 3 5 .5 cubic metres of biogas per day ot a process temperature of 31 °C.
Key words: energy, organic waste, recycling, Senegal.
J.-L. FARINET-Transpaille : energia, fertilización, descontaminación.
El procedimiento Transpaille, puesto a punto por el GIRAD (C e ntro de cooperación in te rn a c io n a l en investigación agronómica para el desarrollo) y desarrollado por Agriforce, recupera y trata los residuos orgánicos por fermentación m e t á n ic a , p r o d u c ie n d o gas y a b o n o c o m p u e s to s . El dispositivo, que se instaló en el matadero de Thiès, Senegal, en 1 9 8 8 -1 9 8 9 , incluye una cuba cilindrica horizontal de 4 0 m etros cúbicos. El m a ta d ero produce 4 8 0 toneladas de residuos al año, que pueden transformarse en 5 5 toneladas de abono compuesto al año y 3 5 ,5 metros cúbicos de biogas al dia para una temperatura de 31 °C.
Palabras clave : en erg ía , residuos orgánicos, reciclaje, Senegal.
J.-L. FARINET — Transpaille : énergie, fertilisation, dépollution.
M is au p o in t p a r le C IRAD ( C e n t r e de c o o p é r a t io n i n t e r n a t i o n a le en r e c h e rc h e a g r o n o m i q u e p o u r le dé ve lo pp em e nt) et développé par Agriforce, le procédé Transpaille récupère et traite les déchets organiques par fe r m e n ta tio n m é th o n iq u e en pro du is an t du g a z et du compost. Le dispositif a été mis en place à l'abattoir de Thiès au S é n é g a l, en 1 9 8 8 - 1 9 8 9 . Il c o m p r e n d u n e cu ve cylin driqu e h o rizo n ta le de 4 0 m ètres cubes. L 'a b a tto ir produit 4 8 0 tonnes de déchets par an, ce qui peut être transformé en 55 tonnes de compost et 3 5 ,5 mètres cubes de biogaz pour une température de 31 °C.
Mots-clés : énergie, déchet organique, recyclage, Sénégal.
J .-L . FARINET - M arketing compost as seedling nursery blocks.
The Transpaille ferm e ntor, installed at the Thiès slaughte rhouse, Senegal, can process 4 8 0 tonnes of solid wastes per year to produce 55 tonnes of compost. As an organic manure compost, it has competition from the price of traditional ferti lizers. Consideration is being given to the possibility of produ cing seedlings in nursery beds, as this could be a profitable m arket sector. The beds contain a mixture of 75 % compost to 25 % sand, plus a w ater-retaining product and a fungicide. Growing seedlings in nursery beds is an increasingly wides pread practice in m a rk e t gardening, due to its agronomic advantages, and there are plans for marketing the technique in major agricultural areas. Regardless of the degree of valo rization of the compost, pollution is eliminated at the Thiès slaughterhouse. In the case of seedlings sold in nursery beds, profits will be made, although this type of utilization means that SERAS will have to diversify its operations.
Key words: compost, plants, nursery beds, m a rk e t garden crops, environment, pollution, Senegal.
J.-L. FARINET - Comercialización de abono compuesto en forma de semilliones en terrones. El fe rm e n ta d o r Transpaille, instalado en el m a ta d e ro de Thiès, en Senegal, puede tratar 4 8 0 toneladas anuales de residuos sólidos para producir 5 5 toneladas de abono com- pusto. Como abono orgánico, el abono compuesto sufre la competencia de los fertilizantes tradicionales debido al pre cio. Se proyecta la fabricación de terrones para semillones, pues se ha revelado una actividad rentable. Los terrones están constituidos por uno mezcla del 75 % de abono com puesto y del 25% de arena, a la que se agrega un producto de reten ción de ag u a y un fu n g icid a . El t r a n s p la n te de semilliones en terrones se utiliza cada vez más en los cultivos hortenses debido a sus ventajas agronómicas, por lo que la comercialización está prevista en los grandes perímetros agrí colas. Cualquiera que sea el grado de valorización del abono compuesto, la contaminación es eliminada en el matadero de Thiès. En caso de venderse semilliones en terrones, se reali zará un beneficio, pero este tipo de valorización supone sin embargo la diversificación de las actividades de la SERAS. Palabras clave : abono compuesto, semilliones en terrones, labores de huerta, matadero, medio ambiente, contam ina ción, Senegal.
J.-L. FARINET - La commercialisation du compost sous forme de plants en mottes.
Le ferm e nteu r Transpaille installé à l'abattoir de Thiès est géré par la société d'exploitation des ressources animales au S é n é g a l (S E R A S ). Il p e u t t r a i t e r a n n u e l le m e n t 4 8 0 tonnes de déchets solides pour produire 55 tonnes de compost. Comme a m en d em e n t organique, le compost est concurrencé par le prix des engrais organiques traditionnels. Lo fabrication de plants en mottes est envisagée et se révèle être une filière rentable. Les mottes sont constituées d'un mélange de 75 % de compost et de 25 % de sable auquel on ajoute un produit de rétention d'eau et un fongicide. Le repi quage des plants en mottes est de plus en plus utilisé en cul tures maraîchères du fait des avantages agronomiques et la commercialisation est envisagée dans les grands périmètres agricoles. Quel que soit le degré de valorisation du compost, la pollution est éliminée à l'abattoir de Thiès. Dans le cas de la vente de plants en mottes, un bénéfice sera réalisé. Ce type de valorisation suppose néanmoins une diversification des activités de la SERAS.
Mots-clés : compost, plant en motte, maraîchage, abattoir, environnement, pollution, Sénégal.
J.-L. FARINET, Y. COPIN - Lagooning, a water purification technique for the tropics.
Lagooning is used for the first tim e os a w ater purification technique at a slaughterhouse in western Africa. This tech nique reproduces the process by which w ater purifies itself biologically, and accelerates and controls the phenomenon. The procedure includes pretreatm ent, a decanter/digester and three lagoons. The organic matter is degraded by bacte ria, producing water, carbon dioxide and mineral elements, which are then assimilated by micro-algae and macrophytes (Pistia stratiotes). The tropical climate is suitable for this processing m e th o d , w hich is o p tim u m at te m p e r a tu r e s between 2 5 °C and 35 °C.
K ey w o rd s : e n v i r o n m e n t , p o llu t io n , p u r ific a t io n , slaughterhouse, lagooning, Senegal.
J. L. FARINET, Y. COPIN - La depuración en laguna, una técnica para purificar las aguas en medio tropi cal.
La depuración en laguna es utilizada por la primera vez para un matadero en Africa occidental. Esta técnica reproduce el fenómeno de autodepuración de las aguas por via biológica, acelerándolos y controlándolos. El principio incluye, en serie, un pretratamiento, un decantador/digestor y tres lagunas. La materia orgánica es degradada por los bacterias, que produ cen agua, gas carbónico y elementos minerales. Estos últimos son asimilados por las microalgas y los macrofitos ( Pistia stratiotes). El clim a tro p ic al es f a v o r a b le a este m odo de t r a t a m i e n t o , el cual es ó p t im o en t e m p e r a t u r a s comprendidas entre 25 °C y 3 5 °C.
P a la b ra s c la v e : m e d io a m b i e n t e , c o n t a m in a c ió n , depuración, matadero, depuración en laguna, Senegal.
J.-L. FARINET, Y. COPIN - Le lagunage, une technique d'épuration des eaux en milieu tropical.
Le lagunage est pour la première fois utilisé pour l'épuration des déchets d'un abattoir en Afrique occidentale. Cette tech nique reproduit les phénomènes d'auto-épuration des eaux par voie biologique en les accélérant et en les maîtrisant. Le principe comprend en série : un prétraitem ent, un décan- te u r/d ig e s te u r et trois lagunes. La m atière organique est dégradée par les bactéries, ce qui produit de l'eau, du gaz carbonique et des éléments m inéraux. Ceux-ci sont ensuite assimilés par les microalgues et les macrophytes ( Pistia stra tiotes). Le climat tropical est favorable à ce mode de traite ment, qui est optimal pour les températures comprises entre 2 5 °C et 3 5 °C.
Mots-clés : en vironnem ent, pollution, épuration, abattoir, lagunage, Sénégal.
