Dear Lea,
I just agree to the above mentioned good points and would like to add some other aspect: Who is profiting very direct?

I do not know about Rwanda much, but you already located in Kenya good technology and local experts who could deliver and support you during implementation, nearby in Zambia and Tanzania you will find good people too. Additional you might see
- Open Source manual of Christopher Kellner at: www.ted-biogas.org/assets/html_standalon...odigester_Lesoho.htm
- energypedia.info/wiki/Portal:Biogas

Aldo the technology and practical implementation issues are important, but not the most important issue in a project like this!

You may stress more on "Who will have the most profit out of this possible biogas system in order to keep it running/alive?"

copy of former contributions to the most important issue: "To run O&M without permanent external supports like external "capacity buildings" is to my understanding very important and to be very clear on profit and personal interests of people involved, not expecting people working just for the merits for free for the community or the local school. E.g. just maybe stating "Community should be involved in O&M process for sustainability" is not enough. Without going too much in very scientific research, organizational and HR details. In my educated guessing, it is very simple: If O&M staff is very direct connected/benefiting from the results of their daily work, you can skip many capacity building projects, quality control measurements, management information systems and scientific researches to keep decentralized or centralized systems running. In comparison, even with a good and permanent monthly salary you can neglect what ever wwtp and biogas system, in north or south does not matter. Good example from Indonesia: small entrepreneurial use of produced DEWATS-biogas by O&M staff to sale cooked noodles to passerby's."

I and others stressed on this important issue several times in the susana-forum, last example:
- forum.susana.org/forum/categories/10-by-...om-switzerland-#7060
- forum.susana.org/forum/categories/53-fae...al-sludge-management
and
- forum.susana.org/forum/categories/35-bio...-fall-into-disrepair

Let me suggest to you a combination of all the valid points made by Marijn, Chris, Julius and by my self:

Again I do not know the local condition, but still let me try. You may not catch all the fly's at once at all for the "only" benefit of that particular school via a biogas system to sanitize toilets, reducing firewood consumption to protect the forest and irrigate trees with effluent at once. A jack of all trades?

How about splitting tasks and benefits?

- School gets their own biogas plant, but running their kitchen on suggested fuel efficient cook stoves, e.g. wood-gasification using "agricultural waste products like maize cobs and so on" producing as by effect charcoal to improve soil condition (see black soil).
- Biogas plant is just sanitizing for the school their toilets and delivering effluent for irrigating to school trees as a service.
- Biogas plant and biogas stoves are "driven" (O&M) by a small group, who see them self as local small entrepreneurs, they "renting" for a small fee the school biogas plant. They are producing biogas via sanitizing (servicing the school) for their own benefit and based on own business ideas e.g. local food processing, cooking and so on. Through this approach they will be inventive and keep the system running and in my opinion even keep better running even during school breaks, as they will look for the right biomass's by them self and may starting business with cattle farmers too.
- This will reduce in the area general wood consumption, not alone for the school.

If not driven by local profit interests, a system like this will fall into disrepair very soon and people will turn on you to fix "YOUR" biogas plant. Be aware, if not fully in the hand of very direct beneficiaries, it will remain "YOUR" biogas plant!

Good Luck with your plans. Let us know how it goes on.

Detlef SCHWAGER

As mentioned, it has been discussed before. For example here:
forum.susana.org/forum/categories/35-bio...s-any-best-practices

While I personally think that a small scale bio-digester should be on pretty much every rural farm, my experience here in Uganda with systems in schools also led me become skeptical.

Adding to what has been mentioned already, there is usually a lack of dedicated technical staff at schools in East Africa and the teachers are not motivated (in general, but especially also) to do manual maintenance work. Thus even much simpler rain-water harvesting systems often fall into disrepair.

Besides that, as has been hinted at, as long as you can't abolish cooking with wood completely, the barrier to switching back to all wood/charcoal is very low and at the first sign of problems the bio-gas system will be abandoned.

I would rather recommend that you look into large fuel efficient cook stoves, e.g. so called rocket-stoves. Working on a similar method, wood-gasification units are also interesting as they allow to cook with agricultural waste products like maize cobs and so on; Ready to set up systems can be imported from China quite cheaply these days.

Dear Lea,

I do not have hands-on experience with biogas, but, from what I understand, Marijn's comments are on-target.

If you want to generate enough biogas for cooking, you could aument the amount of biomass going in, for example by building Urine-diverting Dry Toilets (UDDTs) in the surrounding community, or maybe there is abundant local animal dung or agricultural waste that could be added. This would also help to overcome the problem of school vacations.

Otherwise, I suggest that it would be more practical, economical and reliable to build UDDTs at the school, as we are discussing with respect to a school in the Congo:

forum.susana.org/forum/categories/27-tra...ashing-stations#6988

Even if the biogas project goes forward, I highly suggest you also build waterless urinals that feed fruit trees directly via perforated hoses buried 10 cm under the ground, without anyone having to handle or smell it. As I understand it, urine does not contribute significantly to biogas production (correct me, anyone, if I am wrong). It is also the most abundant type of excrement at a school, so keeping lots of the urine out increases the detention time of the feces in the digestor. In addition, these fruits would be an important, nutritious addition to the children's diet (that does not requiere cooking).

I did a rough calculation, based on recommended doses of chemical fertilizers, that one adult's urine might best go to 10 mango trees, given proper dilution, etc. By dispersing the urine immediately in the soil, the soil microbes that receive and transform it become well populated and this is more in line with the daily needs of the trees (as opposed to the occasional spreading of chemicals, with the risk of overdose).

I also highly recommend having an an active tree nursery at the school, where decomposed fecal solids and diluted urine can feed the young trees for reforestion, with minimal health risk for the children who would optimally participate in this.

In terms of cooking, I suggest there is great potential for solar ovens in most of Africa and other sunny places in the Tropics.

Best wishes,
Chris Canaday

Dear Lea,

If you search around the forum some more you will find that we have had a number of discussions on biogas, especially for school toilets, in the past.

Myself, even though I am a biogas promoter, could probably be placed in the category of people who are a bit skeptical about this approach; the following are my main concerns:

1.) Biogas from toilet waste only, is unlikely to create sufficient cooking gas for the school to fully replace using firewood. Because in many projects the beneficiaries will expect that they can cook all their food on biogas once the system is installed, this is bound to lead to disappointments. So please get some realistic projections of how much gas can be produced and how much cooking can be done with this gas. And make sure everyone understands the limitations of the system.

2.) Unless very long hydraulic retention times are ensured (100 days+) I don't think the slurry is safe to use as a fertilizer and should be dealt with in some other way. Please think that one through carefully.

3.) There is one more big risk, during long school breaks the system is not fed and thus the biogas creating process may die off. If this happens, it will be difficult to get it started again.

Please take up these issues with your supplier, and do contact us here if you are not satisfied with the answers for a second opinion.

Kind regards

Marijn Zandee

Dear all,
I have currently incorporated a NGO in Germany called `Protect nature`. For my first project I would like to set up a biogas plant combined with about 10 toilets at a rural school in the North of Rwanda. As you can see below I am interested in systems developed by Biogas International, Kenya. Since a lot of people use fire wood for cooking etc. the last forests are fragemted and threatened. My aim is to deliver `clean` energy and protect the forest at once. Preferably I would also integrate a water bar.Does anyone has experience with those systems? I am looking forward to any response.

Kind regards, Lea

`Biogas International has developed the world’s first portable biogas system that uses human excrement as input matter. The BioSanGas is an effective waste disposal and sanitation system. The process of anaerobic respiration has a sanitizing effect on the input matter. The output slurry is sterilized and can be applied to plants directly as fertilizer or sanitarily disposed of.

The BioSanGas system is completely “hands off”. The digester is directly connected to the toilet so that human waste is directed into it once flushing is done. The digester is made of high grade plastic material that can sustain the pressure exerted by the biogas produced. At the output end, a closed container may be used for storage before the output slurry is used as fertilizer or disposed of in another way.`
(www.biogas.co.ke/index.php/using-joomla/...7-demo/78-biosan-gas)

Attached you can find more details.