This document provides training on techniques for composting biogas slurry and using the resulting compost and byproducts. It discusses how to produce quality compost from slurry through a two-stage process of separating the liquid and solid fractions and allowing the solid fraction to mature. The effects of slurry compost on soil properties and plant growth are described. Optimal agronomic use of fresh slurry, liquid fraction, and mature compost is covered, including application rates for various crops. Specific instructions are given for using these byproducts to create seedbeds and grow corn, potatoes, cabbage, and fruit trees.

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WORKSHOP OF TRAINING OF SNV BIOGAS
BENEFICIARIES, SUPERVISORSAND PARTNERS OF
DEVELOPMENT
TOPIC: TECHNIQUES OF COMPOSTING, HANDLING AND
VALORIZATION OF SLURRY
BAMENDA, from 12th to 14th September, 2011
Authors:
TEUPA LACHIO BERTIN
Agricultural engineer / Environmentalist
Tel : (237) 75 13 88 08
E-mail : teupalb@yahoo.fr
TIENTCHEU KAMENI Maurice
Coordinator of TERRE ET DEVELOPPEMENT
Tel : (237) 22 14 67 02/ 75 17 09 21
E-mail : terredeveloppement@yahoo.fr
ENGLISH VERSION

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SOMMAIRE
SOMMAIRE ........................................................................................................................................... 2
I-INTRODUCTION ................................................................................................................................ 3
MODULE I: TECHNIQUE OF PRODUCTION OF THE COMPOST ................................................. 4
I-1 Techniques of production of the compost starting from the slurry................................................ 4
I -1-1 What is slurry ?...................................................................................................................... 4
I-1-2 How to obtain a compost of good quality starting from the slurry?....................................... 4
I-2 Effects of a compost of slurry on the soil ...................................................................................... 5
MODULE II: OPTIMAL AGRONOMIC USE OF THE UNDER-PRODUCTS RESULTING FROM
THE COMPOSTING OF THE SLURRY............................................................................................... 7
II-1 The fresh slurry ............................................................................................................................ 7
II-2 Liquid fraction of the slurry ....................................................................................................... 8
II-3- The compost of slurry or mature compost .................................................................................. 9
II-4 Data sheet for the use of the compost of slurry, the fresh slurry, as well as liquid part on some
cultures .............................................................................................................................................. 10
III-4-1 Case of the creation of a seedbed....................................................................................... 10
III-4-2 Case of corn....................................................................................................................... 11
III-4-3 Case of irish potato ........................................................................................................... 11
III-4-4 case of cabbages................................................................................................................. 12
III-4-5 Maintenance of the fruit trees ............................................................................................ 13
BIBLIOGRAPHICAL IREFERENCES ............................................................................................... 14

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I-INTRODUCTION
Conscious of the effects on the socio economic level, medical and environmental inherent in
the use of wood like energy source for cooking in the households, the Cameroonian
government through the Ministry of Water and Energy Resources(MINEE) and in partnership
with international NGO SNV and Heifer international, aimed since 2010 to the promotion and
the development of domestic biogas, through the implementation of the program entitled
“National plan of development and promotion of the domestic biogas”, which started in April
2010. For this purpose, a certain number of organic digesters (model GGC 2047) were built
for some beneficiary households in five Regions of Cameroon (Extreme-north, North,
Adamaoua, West, the North West).
The majority of the households using the organic-digester to date are unaware of the value of
the slurry, bi product resulting from the degradation of the organic matter in an environment
without oxygen. Indeed, the slurry can be transformed into compost and constitute a source
of income for the households if it is marketed, or improve the productivity of the soil. It is
what justifies the implementation of the project entitled “Valorization of slurry as fertilizer for
increased agricultural production and/or for marketing” whose specific objectives are the
following:
 to make the households to understand the importance of the slurry as organic manure
for soil fertilisation;
 to train beneficiary households and the Supervisors and partners of development on
the process of composting, handling, production of the quality organic manure of and
its application in agricultural soils.
To achieve these objectives, the following mandate was entrusted to the consultant:
 to Develop training modules on the techniques of composting, the handling and the
production of organic manure;
 to train beneficiary households, the Supervisors and partners of development on the
techniques of composting, the handling of organic manure;

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 to follow-up the beneficiary households in the practical implementation of the training
by setting up demonstration plot.
MODULE I: TECHNIQUE OF PRODUCTION OF THE COMPOST
Aims :
 To make known to participants, the stages which lead to the production of a compost
of good quality starting from the slurry;
 To present to participants advantages which a compost obtained from slurry offers;
 To present to participants the beneficial effects of a compost of slurry of good quality
on the soild.
I-1 Techniques of production of the compost starting from the slurry
Composting is a mode of stabilization and processing of biodegradable organics waste, using
the natural process of decomposition of the organic matter, which can be held with the free of
air, or in a confined environment.
I -1-1 What is slurry ?
 It is an under product resulting from the digestion of the animal manure once one
introduces them into the bio-digester: This digestion takes place in the absence of
oxygen.
 The model of bio-digester used by the Cameroonian households make it possible to
ensure a digestion at a temperature ranging between 40-45°C. These temperatures
enable the destruction of germs responsible of diseases, and also the seeds of bad
grasses contained in the animal manure.
I-1-2 How to obtain a compost of good quality starting from the slurry?
The slurry which comes from the bio digester is an organic substrate, which still contained a
lot of water. It is thus difficult in this state to store this substrate, or to even market it.
Moreover, the solid phase of the slurry is considered as immature compost.

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Therefore, to produce a mature compost, the slurry should undergo the following stages:
Stage 1: Separation of the liquid fraction from the slurry
How?
 Introduce the fresh slurry into boxes of bamboo
Dimension of boxes of bamboo: 1m X 1m X 1m.
Do not tight bamboos between-them to allow a good ventilation. Moreover, the base of the
boxes of bamboo should not touch the soil, and must be at least to 30 cm above the top of the
soil.
 Put below the lower part of the boxes a container to collect the liquid which runs
 Store the liquid fraction collected in a hermetically closed container
Stage 2: Facilitate the maturation of the solid fraction
How?
 Leave the solid slurry in boxes during at least 2 weeks under the shelter of the sun and
the rain,
 Turn over every week. Then we obtain after at least two weeks, a mature compost easy
to store, and marketable.
I-2 Effects of a compost of slurry on the soil
The contribution of the compost in the soil permit:
to improve the adsorbing capacity of the soil : then the soil retains more nutritive
elements;
to preserve and improve the content of humus in the soil;
to stimulate the useful micro-organisms of the soil;

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to improve the water holding capacity of the soil; therefore, the soil retains from now
more water
to improve the structure of the soil; therefore, the soil resists from erosion better;
to improve the soil porosity; water infiltrates better in the ground;
to loosen the soil; the roots of the plants develop better
to bring fertilizing elements especially phosphorus , but also nitrogen and potassium;
to reduce infestation and the contamination of the soil by the germs of organisms
responsible for the diseases of plants, the seeds of bad grasses, heavy metals.

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MODULE II: OPTIMAL AGRONOMIC USE OF THE UNDER-PRODUCTS
RESULTING FROM THE COMPOSTING OF THE SLURRY
Objectives
 To improve knowledge of the participants on the agronomic values of the following
under-products: fresh slurry, liquid fraction of the slurry, the compost of the slurry;
 To render comprehensible to the participants the advantages and the disadvantages of
the use of under above-mentioned products;
 To present to the participants the techniques of optimal use of the compost of slurry,
the fresh slurry, the liquid fraction.
II-1 The fresh slurry
Agronomic values
The fresh slurry which comes out from the digester is a mixture of two fractions: the liquid
fraction very enriched in nitrogen, and potassium that can be directly used by plants; the solid
fraction rich in organic matter and assimilable phosphorus. Its fertilizing capacity is far higher
than the dried slurry.
In the North-West region, the households having tried out the fresh slurry noted the absence
of negative effects on culture after using it while sowing or transplantation. These households
rather noted an answer more favorable of the plant for the fresh slurry compared to the dry
slurry.
These considerations lead us to make the following recommendations for an optimal use
of the fresh slurry in agriculture:
 The Considerations to use in an optimal way the fresh slurry
 fresh slurry in an agricultural system of production which depends little on mineral
manure must be used in a preferential way because it offers the double advantage of
being at the same time a mineral manure and an organic soil conditioner
When to bring?

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 It could be used as well as a basic manure and a cover manure; therefore, it could be
spread on the soil at the time of sowing or transplantation (basic manure), or in the
course of culture (manure of cover).
 Its hiding on the soil could be immediately followed by the sowing or planting,
without a depressive effect on the plant being observed.
How to bring?
 To optimize the use by the plant of mineral nitrogen brought by the fresh slurry, it is
necessary to hide it in the soil, and to avoid spreading on the soil surface ;
 As previously, the hour of hiding of the fresh slurry in the soil will influence the
optimal use of the plant of nitrogen mineral brought. Thus, we recommend to hide this
substrate in the ground very early in the morning, or late in the evening, by avoiding
sunny times;
 Depth of hiding: 10-15 cm. Indeed, it is the layer of the ground richest in micro-
organisms and the best ventilated one, which will have to support the good
mineralization of the organic matter.
Where to bring the fresh slurry?
 Their strong water content limits their storage, their transport and marketing. They
will thus be used in a preferential way in the pieces located near the household.
Which quantity is necessary to use? : see table 1
II-2 Liquid fraction of the slurry
This fraction contains more nitrogen than the compost or the fresh slurry .
When to bring?
The liquid fraction of the slurry is regarded as nitrogenized manure, and for this raison, it
must be brought. after sowing and during the phase of growth of the seedlings (approximately
2 or 4 weeks after lifting);
How?

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 Make a line approximately at 10 cm from the line of sowing. This line must be 3 to 5
cm deep;
 incorporate the liquid fraction of the slurry in the line then cover with ground;
 One can also bring it while making a round around the seedling, then incorporate
liquid manure in the round and recover with ground.
 Favorable moment of spreading
The liquid fraction of the slurry is a primarily nitrogenized manure. To optimize the use by
the plant of assimilable nitrogen that it contains, it will be necessary to avoid incorporating it
in the soil during the sunny period of the day.
Thus we recommend to incorporate this manure either early in r the morning, or late in the
evening.
 Indicative amount of contribution on some cultures: see technical requirements
below(data sheets)
insert a draw
II-3- The compost of slurry or mature compost
General considerations: this substrate has a fertilizing capacity lower than the fresh slurry.
We recommend that its use must be associated with mineral manure or the liquid fraction of
the slurry. This will permit to have an answer of the plant comparable with the enrichment of
the soil with fresh slurry.
 Quantity and period of contribution
The compost must be hidden in the ground at the time of sowing or transplantation. The table
below gives indications on the amounts of application for some cultures
Tableau 1: Proportion of the mature compost advised for some cultures
Culture Plant density
(plants/ha)
proportion of the
compost usable
proportion of the
compost
usable/ha
Number of
bags of 50 kg

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1 Corn 50 000 0,4-1,2kg/plant 20 – 60 t 400-1200
2 Yams 10 000 1,3kg/hole 13 t 260
3 Irish
Potatoes
50 000 0,25 - 1 kg/plant 20 -50 t 400-1000
4 Palm tree 146 2,5-3kg/plant 365 kg -438 kg 8-9
5 Banana
plantain
1111 2-3kg/hole
6 Tomatos 22 000 1kg/plant 22 t 440
7 nursery - 3kg/m2
8 Fruit trees variable 2,5-3kg/plant
Source: PRSSE (Programme de Réforme du Sous-Secteur Engrais)
How to bring?
See data sheets below
II-4 Data sheet for the use of the compost of slurry, the fresh slurry, as well as liquid
part on some cultures
III-4-1 Case of the creation of a seedbed
 Arrange boards of sowing with a dimension of 5 m length, 1 m width. Thus, it gives a
surface of 5m2.
 Bring the compost to the boards of sowing to the amount of 3 kg of compost/ m2.
Thus for 5 m2 it will be necessary to bring 15 kg of compost.
 Sightly incorporate (on approximately 5.-10 cm) the compost in each board of sowing
using a small rake.
 Using a stick, to draw parallel lines with a depth of approximately and separate each
other of 20 cm. and 1 cm depth .
 Spread in these lines a nématicide-insecticide, like MOCAP 10G or the COUNTER
10 G at a rate of ½ spoon of coffee per line

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NB: one can also disinfect the ground by bringing ebullient water, at a proportion of
10l/m2. That must be done before tracing the lines
 Sow the seeds on the treated lines, then to cover the board of sowing with the straw
or the sheets of raffia
 Remove the sheets of raffia when lifting begin and arrange a shelter
 Treat the seedlings with the suitable pesticides
Duration in seedbed: Variable according to the seedlings (3-4 weeks)
Insert a Draw
III-4-2 Case of corn
 Plow the ground (20-30 cm of depth), by taking the care to split up the lumps of earth;
 Spread on the plowed ground the compost at the following proportion: 20 t/ha-
60t/ha, i. e. 2-6 kg of compost/m2
 Incorporate the compost in the ground, on approximately 10.-15 cm of depth
 Then sow the seeds
III-4-3 Case of irish potato
 Plow the ground and to make balks of 50-60 cm width, 20-25 cm height. The balks
are separated each other from 60-80 cm
 Open the medium of each balk on a 15 cm depth
 Bring the compost in the open line in the middle of each balk, and cover it slightly
with ground.
 Lay out then the tubers of potato every 25-40 cm in the open line of
 The first sarclo-ridging takes place between 30-40 days after sowing. Then bring a
manure of cover, in particular the urea, with the amount of 1 limps of tomato for 20
seedlings. The urea is brought around each seedling.
NB: In the place of urea, one will be able to also use the liquid fraction of the slurry
resulting from a bio-digester as presented to section III-2;
INDICATIVE AMOUNT: 1 limps of sardine (or 02 limp of tomato) of liquid fraction of
slurry/Plant.
However, research should lean to confirm this optimal amount.

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Insert a draw
III-4-4 case of cabbages
 Plow the ground around 30 cm depth
 Bring 4 kg of compost/ m2, then hide it on 10-15 cm depth
 Materialize the lines of planting : spacing between lines: 75 cm; spacing between
seedlings on the line: 40 cm
 Plant the cabbage seedlings
 3 to 4 weeks after planting, bring urea to the amount of 1 limps of sardine for 7
seedlings.
NB: In the place of urea, one will be able to also use the liquid fraction of the slurry
resulting from a bio-digester as presented to section III-2;
INDICATIVE PROPORTION: 3, 5 limps of sardines of the liquid fraction of slurry per
seedling.
However, research should lean to confirm this optimal amount
In the case of sowing on seed hole:
 Open the seed holes, and bring in these seed holes approximately 0,5kg of compost ,
then mix with soil
 Plant the cabbage seedlings in the seed holes having received the compost and cover
with the ground.
 3 to 4 weeks after planting, bring urea to the amount of 1 limps of sardine for 7
seedlings.
NB: In the place of urea, one will be able to also use the liquid fraction of the slurry
resulting from a bio-digester as presented to section III-2;
INDICATIVE PROPORTION: 3, 5 limps of sardines of the liquid fraction of slurry per
seedling.
Insert a draw

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III-4-5 Maintenance of the fruit trees
Each year, on the surface covered with the sheets of the fruit trees, distribute a layer from
approximately 1 cm thickness of compost, with the amount of 2,5 - 3 kg /plant
Insert a draw

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BIBLIOGRAPHICAL IREFERENCES
CEFREPADE
Composting of waste in the developing countries: methods of installation and follow-up of
perennial decentralized installations, October 2008 –
ICRAF
Good practices of culture in forest seedbed: Practical Directives for the Community seedbeds.
Technical handbook N° 2,2006 –
Maider ETCHART
Management and valorization of the slurry of collective methanisation in the basin of the
Arterris co-operative, September 2009 –
PRSSE
Data sheet on the fertilization of the potato (Solanum tuberosum L.) in Cameroun
PRSSE
Data sheet on composting in country medium
SOLAGRO
The agronomic quality of the digestats: synthesis, December 2004