Piki piki means motorbike in Kiswahili
This gadget was created to solve a real problem with biogas – getting the dung to the system quickly and efficiently. Motorbikes are the taxi’s of Africa so why not? Before I tell you about the above gadget I just want to remind you about the problems we have been having to solve to get the biogas to work at home.
Installing biogas at home has a real experience in afrigadget – we have figured out by trial and error how to get the gas under pressure –
At first we tried using water pressure, but when we stepped back and looked at it we realized that it really wasn’t simple or appropriate for bush applications ..
In fact, all we needed to do was to put pressure on the bags.
The pressure wasn’t enough to run the stove until we modified the stove jets by enlarging them slightly.
Next we had to figure out how to get the dung to my digester – you see I don’t own cows but my neighbors who live a few kilometers away do and are selling it at a very nice rate of Ksh 50 (70 US cents) for two large buckets . The owners are happy to see the dung as it accumulates in the nighttime stockades and attracts annoying flies that carry diseases if left on the land.
The problem I face is common to many folks around here, we rent houses but we don’t have livestock. But there are huge cattle farms around us. So Dominic came up with a solution that creates jobs and moves poop quickly and efficiently.
So we went to the local juakali welder on the roadside to create a dungmobile ..a trailer designed specially for cow dung!
We tested it with a human load to ensure it is balanced … each bucket weighs about 50 kg.
And the first delivery arrived without a problem! 🙂 Big Thanks to Dominic Wanjihia who seems to always have a simple solution to any problem.
I know you are wondering, if it’s that easy, then why doesn’t everyone use biogas?
Now that I’ve got biogas running my kitchen I wonder why so few people have done so in Kenya. There are countless articles, publications, websites and people who will tell you that biogas is the most economical and environmentally sustainable way to produce energy. In fact, the benefits of Biogas have been known for tens of years, and hundreds of systems have been built in Kenya. But it hasn’t really taken off – few of the installed systems are actually working and the uptake of biogas systems at a domestic level has been slower than slow – it’s virtually non-existent. A review of biogas in Kenya reports that technical breakdowns has discouraged uptake but the main limiting factor is cost.
Here’s a simple comparison of costs – from continuing using charcoal/fuelwood or Kerosene and LPG to using various biogas options.
|Options||Cost (US$ )||Time to install (days)||Labour||Maintenance||Durability|
|Fixed dome||1,500 – 2000||21||5 people||Low||Decades|
|Floating top||2,000 – 3,500||21||5 people||Low||Decades|
|Flexi bag envelope||400||1||1 person||Low||10 – 15 years|
|Fuelwood or LPG cylinders||200 (per year)||0||0||low||Decades|
For a simpleton like me these figures are immediately revealing – it takes 2 years to pay off a flexibag digester after which domestic fuel is free for at least the next 10 – 13 years. For the underground systems you have got to be hugely rich, or suffering from environmental guilt to make the decision to switch to biogas – from an economic perspective it will take 10 to 20 years to pay back. You could grow your own trees and make your own charcoal in that time frame….
Why is it so expensive for the constructed biogas systems? Because most of the biogas systems in use are constructed systems requiring engineering and masonry, they are very expensive, take weeks to install, require experts, and intensive follow up. If they go wrong it’s a major engineering task to fix it. This is why we are promoting the flexible bag option for domestic and small industry use.
Congratulations to Skylink Award winning Kenyan biogas innovators
We would ;like to congratulate Skylink Innovations who have just won a the Ashden 2010 Award for their biogas installations in Kenya.
I thought skylink was an airline… Biogas operated planes???
Their industrial scale system costs Ksh 1.6 million (US$ 19,753). Such installations may need to be financed by the Government institutions where they clearly make enormous economic and environmental sense for schools, prisons and other large institutions.
For small scale house hold units, we need solutions that will compete against the cost of installing LPG or using charcoal, firewood or kerosene stoves. When we talked to local Maasai near Nairobi they found the flexi bag systems appealing because they could be purchased with the sale of just 2 or 3 cows, can be rolled up and moved when they migrate, and it saves the women the work of searching for firewood, it’s hygenic because water can be heated for bathing children, while it also removes dangerous piles of rotting cow dung near the homesteads which are breeding sites for biting and disease carrying flies which affect livestock and people.
32 thoughts on “Poop piki piki for my biogas system”
nice work! For a moment there I was *concerned* when I read that you tested the trailed with human load.. read like human waste!
This is excellent, I like the way you keep things relatively simple. My landlord is building a biogas digester from old metal containers, he likes working with metal. I’ll be interested to see it being tested but I’d say it will be tested in its final resting place, rather than here, where it’s being constructed. I’ll try and get a few photos but it’s just a collection of containers right now. All the best. S
I’m reposting, thanks so much for sharing!
This is a great system. And i like all those handy pictures. But what i am searching is a stepp by stepp guide to actually build one.
Would you like to post one or maybe a link?
Thanks for you lovely Blog
I should have added that i was talking abut the biogas System. Not the trailer 🙂
A step by step description of a similar system made from cheap polyethylene tubular film can be found at
It is not durable as the bag system above but if you protect it from UV rays from the sun it will bear up for about 2 to 4 years. Then only the foil has to be replaced all other components will be still useable.
I’m curious about something – how do you add the new dung to the bag without letting out all the gas? Is it in a separate container?
Hi Mart, there’s not much to show as it is so simple, check out my previous post https://www.afrigadget.com/2010/06/09/solving-the-flexible-biogas-digester-problems/ .
Hi Rosa, good question. Check out hte pictures on this blog https://www.afrigadget.com/2010/06/09/solving-the-flexible-biogas-digester-problems/ and you will see that the gas cannot escape as the dung is holding it back – the inlet pipe enters at the bottom of the digester. Hope that makes sense.
Congratulations for your common sense approach & practical innovation.
Energy Independence require us to seek nature based sustainable solutions.
I would suggest installing a plastic pipe loop at the bottom of the digester bag and circulating hot water through it to increase biological activity. A small solar water heater could keep the digester warm and produce more bio gas. Try it.
Practical and simple just the way it should be
Do not forget to add your organic food waste ( mashed and slurry form only- no bones) to the Poop- it will produce more bio gas. Add at different times to not overload the digester.
When you draw the digested solids out, add some chopped up yard waste and bury in a trench to make compost. If worms are available it can accelerate the vermi-compost process.
thanks Ram really appreciate your ideas. Paula
Great Paula, Still hoping to come and see how it really works!
Are you near the Rudolf School? You can encourage them to invest in Biogas, they have lots of animal waste in the school.
I think this is an awesome way of helping yourself, while also helping the environment.
I apologize if you have already covered this or I missed it, but what type of supply do you need in order to produce enough biogas for you/family? That is to say, is it something you can only do if you have a herd of animals or can it also be done on a smaller level?
Is there any way we in the more developed world could fund the construction of biogas digesters through micro-loans perhaps?
This project is a great example of self reliance and how one family can show us what ” Be the Change” means. Hope it starts a grass root movement that can replace the need for fire wood in poor communities. We know the adverse impact of deforestation on climate which causes flooding, and loss of good top soil.
There is no shortage of food waste, agricultural and animal waste in villages. With support from UN, the Local lending institutions should offer 60 month- low interest loans to help people build such systems and be able to live with nature. It is time we stop destroying nature and live with it smartly and help our environment.
Are the Leaders in poor country ready to lead?
Good luck to all who follow this example.
Great article. I dont know how we have lived without this LPG costs more than this. I have to try this out!!!!!!!!!!!!!
This is great. but why don’t you use human excrement too? There are countless examples of biogas being created from human source, eg half of Rwanda’s prisons use it (they also won an Ashden award). It’s a brilliant way to turn waste into resource. You’d need the cow dung for volume.
rose (author of The Big Necessity: The Unmentionable World of Human Waste and Why it Matters)