Using biogas technology to solve the disposal issues surrounding latrine waste
Practical Action
maintain, by weight, a Carbon/Nitrogen (C/N) ratio between 20-30:1. The C/N ratio can be
manipulated by combining materials low in carbon with those that are high in nitrogen, and
vice versa (The United Nations, 1979). “If the C/N ratio is very high the biogas production will
be low; if the C/N ratio is very low, the pH value will increase, and will have a toxic effect on
bacteria” (Mang & Li, 2009).
Social and cultural issues
The first area of concern regarding social and cultural issues is tackling problems regarding
the community’s willingness to use the technology. There are three main areas that must be
dealt with to ensure a successful implementation.
First the implementer must keep the public well informed. It is “extremely difficult to achieve
change in excreta disposal practices as they are part of the basic behavioural pattern of a
community and are not readily modified” (Faechem & Cairncross, 1978). Chaggu et al (2002)
identify in Dar-es-Salaam that there is a lack of understanding why the disposal system has to
be changed because of the “lack of perceived benefits” (IRCWD, 1982) biogas technology
has. The low education level results in “inadequate financial resources” (Chaggu et al, 2002)
so the priority is not a good excreta disposal when there is competition for financial resources.
This poor education level leads a low level of involvement (Strauss et al 2002) and without
involvement, construction and maintenance skills cannot be passed on.
This lack of knowledge can lead to an unwillingness to use the by-products, (Strauss &
Montangero, 2002) the second area of concern. When assessing the willingness to use the
residual as a soil conditioner the critical factor is land to use the conditioner on. If people do
not have gardens or areas to use compost, like in urban areas, then they are not going to want
it. One solution suggested is for farmers and other industries that have use for soil conditioner
to collect the treated sludge. This will be dependent on a number of factors including
sufficient access for the farmer’s haulage vehicle to collect the soil conditioner, the collection
being more beneficial for the farmers (i.e. quicker and cheaper) than collecting from their
normal supplier and also the dependability of the agreement. Gas should be more acceptable
than the residual because of the lack of direct contact with consumables that soil conditioner
has. However the reasons why people do not like the use of digestion by-products cannot
always be attributed to a straight forward misunderstanding. Often these decisions are difficult
to understand.
The final concern when dealing with willingness to use the technology is religious issues over
human excreta. Night soil workers carry a stigma, Eales (2005) explains that in Kibera
residents see the job as illegal and it is therefore “legitimate to assault those who haul
stinking buckets and drums through narrow alleys”. This leads to emptying taking place at
night because there is less chance they will be robbed or beaten. The idea is to make the
process as less obtrusive as possible, which implementing manually operated systems will do.
This will limit the disruption to the customer and therefore their opinion of emptying will
improve. Regarding cultural taboos research could only come back to the use of education
programmes put in place to help people understand the benefits of the practice, but once
again this factor is very context specific.
Another area of concern is the effect of increasing the emptying frequency. There are two ways
the user can be affected, the increase in frequency of payments and, the inconvenience to the
occupant. The inconvenience to the user can be limited through improved emptying practices
as outlined throughout this brief. Regarding the former point, currently, the occupant will
relate the pit being full to emptying time. The challenge the implementer faces is to remove
that link and in its place put in an ideology that instead of waiting for the pit to fill, have it
emptied on a more regular basis so the user has more control over payments. The burden
households face when saving up for one large payment is often too much and can often leave
them in financial disarray. A smaller more frequent payment will be easier to manage removing
the cash flow risk large payments carry. It is important that these smaller more frequent
payments do not leave users worse off financially. If you can incentivise the setup by
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