Biogas use in Reconstruction
Practical Action
Haulage: for sustainability reasons and to limit costs the push is to combine the system with
manually operated emptying technologies (Boot N., 2006). These technologies are also more
feasible in urban settings where access is an issue for vacuum pumps. When using these
technologies it is not the distance from the latrine to the disposal point that is the defining factor
but the time it takes.
Disposal: is essentially about the placement of the digester which is governed by three main
factors:
Space and land tenure; for example in slum areas space is sparse and they live on land
they do not own so improving sanitation facilities is not high on their priority list
Not in my back yard (NIMBY); people do not want waste dumped where they live however
this is a very context specific area
Use of the gas; whether it be a communal facility or private household
Treatment: there are essentially two main issues regarding treatment. The first is problems
surrounding pressure of the gas. One solution would be to ensure that the digester is correctly
maintained. Another physical solution, highlighted by Kossmann et al. (1999), is the use of a
separate gas holder. Floating drum digesters allow the user to alter the pressure of the gas by
applying weight and pushing the moving “drum” down.
Research has highlighted maintenance issues surrounding these digesters and that fixed dome
digesters provide better results. Therefore a possible solution is to take the benefits from both
technologies and use them to their full advantage by using the fixed dome design for the batched
digester setup while connecting a floating drum design in series to act as storage, so when/if the
user does experience pressure complications they can apply an amount of weight to the top of the
drum and increase the pressure.
Figure 6: Possible digester setup to deal with pressure issues - Source: Practical Action
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