Feasibility Study for a National Domestic Biogas Programme in - SNV

Feasibility Study for a National Domestic Biogas Programme Burkina Faso
be composed of several digesters connected with one gas holder, which
again increases cost and labour.
While it is recognized, that batch-fed digesters are the simplest biogas
generators, it is not advisable that especially in schools students had to
operate the batch wise filling and emptying as punishment, as it has been
practised in most educational institutions.
3. Utilization of local materials. Use of easily available local materials should
be emphasized in the construction of a biogas plant. This is an important
consideration, particularly in the context of Burkina Faso where transportation
infrastructure has not been developed adequately. Due to the subsidy policy
this obstacle to a dissemination strategy has never been considered. Today
‘real locally’ available building materials are mainly red soil, sand, natural
stones, cement and cement bricks, PVC- and galvanized piping, offered by
commercial hardware services in any commune all over the country. Metal
workshops are still centred around the main market places and in urbanized
areas.
4. Durability. Construction of a biogas plant requires a certain degree of
specialized skills, which may not be easily available, and supervision during
construction to guarantee water and gas tightness. A plant of short life could
also be cost effective but such a plant may not be reconstructed once its
useful life ends. Especially in situations where people are yet to be motivated
for the adoption of this technology and the necessary skills and materials are
not readily available, it is recommended to construct plants that are more
durable although this may require a higher initial supervision labour and
capital investment.
5. Suitable for the type of input material. The design should be compatible
with the type of input material that will be used. Fresh manure, fibre-free
vegetable pulp, sewage can be put into a continuously charged biogas
digester. However, in the 70 th and 80 th zero- or semi-zero-grazing practices
have yet been not common and organic waste, sanitation and sewage has
not been considered in any national biogas strategy. Therefore only plant
(waste) material such as sorghum or millet straw, maize straw or similar
agricultural plant wastes mixed together with dried manure have been
promoted. This material led to the point that the batch feeding design or
discontinuous system was standardized instead of a design for continuous or
semi-continuous feeding.
6. Frequency of using input and output material. Selection of a particular
design and size of its various components also depend on how frequently the
user can feed the system and utilize the gas and the slurry. As R+D project,
the standardized batch dry fermentation design filling and emptying frequency
was even successfully adapted to irrigation systems to drive motor pumps
with biogas. 92
92
Lidon, B. and Sola, G., APPLICATION DU BIOGAZ A LA PETITE IRRIGATION, CIEH,
January 1982
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