KIGALI, RWANDA—Field visits. If you want to do research in Africa on a shoestring (and I imagine other continents too) meet with the NGOs and companies of interest and arrange to go on one of their field trips. All organizations so far have been more than happy to take me along. It is a good deal for me and it is a good deal for them. For me, I get to have the undivided attention of knowledgeable people who would be hard pressed to spare 15 minutes to talk to me in their office. In the car, we get to talk for hours. For them, they are glad for the companionship. The field visit doesnt’t cost me anything and the people I travel with make for excellent tour guides. Even if you are not doing research, this is the way to get a local perspective while traveling on a shoe string. So my advice to you is come to Africa, find something interesting and start going on field visits with NGOs. In fact, living on a shoestring is the only way to get a local perspective. I have come to understand that if I had more money I would not be as good at my research.
I didn’t have much time in Rwanda but I wanted to see the famous biogas systems installed in the over capacity prisons of Rwanda. The prisons turned the problem of too much human waste into biogas for cooking. Foreigners need special permission to visit prisons in Rwanda which I did not have time to obtain so I went on a field visit with the Ministry of Infrastructure instead. MinInfra (Ministry of Infrastructure) is the implementing partner of the domestic biogas program in Rwanda. Claude of Mininfra was doing follow up for three anaerobic digesters of around 30 cubic meters recently built for schools. I tagged along.
There wasn’t much to see as everything but the digester covers are below ground, but the scenery was gorgeous.
The latrines are flushed with rainwater harvested from the roof. There is an auxiliary supply of water from the road in case rainwater is insufficient.
Like most toilets I have seen in Africa, these were squat toilets.
This is looking down through the toilet. A gutter passed under each of the squat toilets. Water was flushed down the gutter a couple of times a day to wash the feces into the digester. This was the first time I had seen such a set up. I am sure that it saves water. But the negative side effect is that the toilets don’t smell very good as there is feces sitting in the trough until it is flushed. Normally one of the benefits of a biogas toilet compared to a latrine is reduced odor, but here that benefit was not realized. Claude later said he would request that a vent pipe be installed to reduce odor.
Biogas production was only just beginning for these newly installed digesters. Bacteria populations in the digester take some time to form so methane production may not begin for a month after initial use. These stoves were originally heated with firewood but they had been retrofitted with huge biogas ranges manufactured in Kigali. We had some trouble lighting the stove though you can see a few blue flames. The carbon dioxide concentration may still be too high.
The place where part of the kitchen wall was broken gave a testimony to the smoke the cooks once endured. Soot from the wood fires now covered the walls, windows and ceilings.
On the way home we stopped by a domestic biogas plant of 6 cubic meters I believe. Mininfra, as a strategy to jump start anaerobic digester demand in Rwanda, awarded the most enterprising farmer in each of the 30 something districts a highly subsidized biogas plant and this was one of them. In Rwanda it is illegal to cut down trees without a special permit and even then you must plant trees in exchange. This means that people need to look for other sources of fuel, giving the biogas sector a big boost.
The biogas plants constructed under the domestic biogas program in Rwanda are the GCC style rather than the Modified Camartec used in Uganda. For a while, bricks were outlawed in Rwanda because brick making requires a lot of firewood. Thus, many biogas systems in Rwanda use rocks instead of bricks.
This farmer had a novel mixing mechanism. The inlet basin is filled with cow dung and water (in equal portions) and then the farmer can turn the crank to mix the slurry. The “feet” press the slurry against the sides of the basin to break up the clumps. I saw a man in Uganda mixing the cow dung elbow deep, which looked less fun. I am interested to see how this mixer works and if it wears down the concrete sides of the basin. And how to improve this mixer.
In the house, the biogas passes through a scrubber (top) and then through a gage. The only complaint of the farmer’s daughter was that the biogas smelled bad. This was because of hydrogen sulfide in the biogas. I know that scrubbers need to be aired out every once in a while to regenerate their capacity for absorbing hydrogren sulflide, so I wonder if the scrubber was simply saturated.
The stove itself was made in Kigali. I later visited the biogas stove salesman in Kigali who imports from Puxin Biogas in China. His stoves are much more expensive and I discovered that he spend three times more on shipping that on the stove itself. Crazy.