Technical potential for household biodigesters in Africa
Based on the FAOSTAT database, SNV Netherlands Development Organisation assessed the technical potential for household biodigesters by country in Africa. The findings indicate that the number of households qualifying for such digesters amounted to 32,9 million in 2018. This is an increase of not less than 78% compared to 2006. The rise is driven by the surge in the number of agricultural households with access to water and the strong growth of the dairy sector in Africa.
Although biogas can be generated by a score of organic material, cattle dung is arguably best suited as a substrate for small installations; the digestion process is robust and the material is abundantly available on many farmyards. For a biodigester to be attractive to a family, it should be able to provide at least 0.8 to 1 m3 biogas daily. To generate this amount of biogas, the household should have at least 20 to 30 kg of fresh dung available on a daily basis. Such amount of biogas would provide about 2 to 3 “stove hours”; sufficient to prepare at least one family meal. Theoretically, two mature cattle would be able to produce this amount of dung, however for large parts of Africa zero-grazing is not common, therefore most African households would rather need at least 3 or 4 night-stabled heads of cattle.
To enable both the installation’s micro-biological process as well as the hydraulic functioning, the feeding material, dung, has to be mixed with equal amounts of water4. This process water does not have to be of “drinking water” quality, but –in view of the significant amount needed on a daily basis, should be available in the vicinity5 of the installation.
Thus, the two main drivers for the technical potential for household biodigester are the number of cattle (partly) on-yard and the number of agricultural households having access to water.
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