Biogas Technology in Tanzania
Overview
History
The history of biogas dissemination in Tanzania dates back to 1975 when the Small Industries Development Organisation built 120 floating-drum plants up to 1984. In the Arusha region the Arusha Appropriate Technology Project constructed traditional Chinese fixed-dome plants and "floating-seven-drum digesters", their own development consisting of a gas holder made of 7 oil drums connected together. The objective of this project was to build biogas plants at the lowest investment costs possible. In 1982 the newly founded parastatal Organisation Centre for Agricultural Mechanization and Rural Technology (CAMARTEC) continued the dissemination of this technology in the Arusha area. About one year later Technical Cooperation between Tanzania and Federal Republic of Germany led to the introduction of the Biogas Extension Service (BES). CAMARTEC and the Deutsche Gesellschaft für Technische Zusammenarbeit (GIZ) were in charge of implementing this project and the latter seconded an interdisciplinary team (social scientist, mechanical engineer and agriculturist) to Tanzania. Only a few of the more than 100 biogas plants built were still in operation at this time.
In the initial years the BES disseminated biogas plants mainly in the so-called "Coffee and Banana Belt", the region around Arusha where particularly positive conditions promised a high dissemination density for biogas plants:
- a fertile region with high productivity and a dense population (192 inhabitants/km2 cf. national average of 25/km2)
- smallholding structure, farm households own an average of 1.5 acres of land
- extensive animal husbandry for dairy production
- relatively well-off farmers as widespread additional income from other jobs
Standardisation
Concentration on a project area which could be easily observed with good conditions led relatively early in project history to standardisation not only of the plant design, of administrative procedures, of guarantees (2 years) but also of user advice which in view of the high dissemination density could be carried out village for village. In 1984/85 household plants were offered with a digester volume of 8, 12 and 16 m3, in 1990 the programme comprised standardised plants of sizes with 12, 16, 30 and 50 m3 for households and institutions as well as a toilet biogas plant for an institution.
Technical Development
A variety of technical development work was necessary to guarantee long-term performance of the plant. The fixed-dome plant initially disseminated by the BES proved to be non-reliable in practice. After 3 years of operation cracks allowing gas to leak out appeared on many plants with a digester volume of over 8 m3. The cause of this was seen to be in that the dome construction was not statically determined and cracking from the digester region up to the gas storage area could not be prevented. The solution to this problem was a pre-determined breaking point, the so-called "weak ring". Later a reinforcing ring, the "strong ring" made of concrete was added over this. This guaranteed that the gas storage area remained free of cracks. Another technical innovation which proved to be beneficial was the use of an additive in the cement for the gas-proof plaster. In the meantime the experience gained by CAMARTEC has been used successfully in many biogas dissemination programmes.
During cooperation work with a Kenyan organisation gas burners were developed which were reliable, easy to service and which corresponded to the cooking habits of the region. Supply problems and inferior performance of imported gas lamps led to an own model being developed and to the modification of petroleum pressure lamps for operation by gas. A kit developed for this purpose was exported to other GTZ projects. In other projects only the idea was taken up and this led to more simple solutions, e.g. in Java. The use of biogas for large-scale consumers necessitated the development and distribution of a gas cooker for institutions which only works with primary air and thus burns stably.
The development work towards sustainable reliability and user friendliness resulted in extensive integration of biogas plants into the work routines of farmers. As a "biogas unit", a system of coordinated components was developed to include not only the plant but also integration into the farm system. This included livestock housing with a concrete floor and direct connection of the urine channel to the digester, slurry tank, distribution channels for the slurry or a slurry cart, advice on the utilisation of slurry, gas pipeline systems, burners and lamps. Women were specifically instructed during initial years in Tanzania but this process suffered when the GTZ social studies expert left the project.
By 1990 around 200 "biogas units" had been constructed directly by the BES or on its authority by trained craftsmen. In 1992 there were 600 biogas plants in the whole of Tanzania.
Special Energy Programme
Dissemination strategy and project structures underwent decisive changes mainly around 1990. These were chiefly a result of financial and personnel withdrawal of the GTZ from the BES and the subsequent extensive transfer of the project to the counterpart organisation. In the course of this transfer phase from 1990 to 1992 and with a further extension from 1992 to 1994, the project receives financial support within the scope of the Special Energy Programme (SEP) which apart from the biogas component also includes fuelwood-saving stoves. Personnel involvement of the GTZ is reduced to one person for both components and the main task of this person is to see that the locally provided funds of the BES are used for the purpose intended and the SEP funds are applied to overriding measures which the customer cannot finance (e.g. training).
Financing
Orders which cannot be covered by the standardised range of plants and services and which necessitate additional research and development work have to be financed completely by the customer. This increased orientation towards privatisation of the BES has sent the costs for a Biogas Unit from around TSh 300,000 in 1989 to TSh 400,000 to 7000,000 according to the region. Despite this, the number of units constructed until 1992 has increased to about 400.
Further Dissemination Programmes
Apart from the CAMARTEC dissemination programme there are two other relatively extensive dissemination programmes: one is being carried out by the church organisation (ELCT) in Arusha and one by the Ministry of Water, Energy and Minerals in Dar es Salaam. On all sides there is sporadic cooperation in the field of training and upgrading with the animal husbandry department of the Ministry of Agriculture in Arusha and the Ministry of Water, Energy and Minerals in Dar es Salaam which primarily supports the dissemination of biogas technology in the region of Dar es Salaam. It ensures training for private craftsmen, builds demonstration plants and is in charge of monitoring and evaluation.
There has been no cooperation with the active church organisation ELCT which has been active in dissemination since 1988. The reason may be the almost contrary dissemination concept of the ELCT in comparison to the BES. In ten decentral church centres there are contacts trained in biogas technology who coordinate advice, training of biogas craftsmen and construction etc. The target group is made up of farmers with at least two head of cattle. Chinese fixed-dome plants with conical fundaments are disseminated. The farmers receive 50% of the investment costs as a credit on conditions depending on their socio-economic situation. To keep the investment costs low the farmer families are included in the construction of plants. The costs for a 12 m3 plant, for example, amount to an average of TSh 100,000. Biogas accessories (lamps, stoves) are imported from India and China and are around half the price of those from CAMARTEC. CAMARTEC's commercially oriented, strictly standardised dissemination programme is considered by ELCT as not adapted to Tanzanian conditions as it only serves the rich farmers.
Further Information
References
