Poop piki piki for my biogas system

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.

Skylink recieve the Ashden Award from Sir Richard Attenborough

I thought skylink was an airline… Biogas operated planes???

Human waste digester under construction in Meru Prison

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.

Solving the flexible biogas digester problems

You’d think that given the amount of cow dung available around rural Africa that biogas would be a big hit right? Well, its actually relatively unknown. The main reason is materials, coast and complicated technology. People in these areas use charcoal or wood for their domestic cooking needs – its not only dirty hard work to collect firewood, but it’s unhealthy and damages the environment. But, it’s free …

We believe that  biogas from cow dung holds huge promise for rural and urban areas as a cheap source of energy that can be turned into domestic use or even business anywhere in rural Kenya….eg. pasturizing milk, making yoghurt, running fridges, generators, hammer mills for grinding corn, cooking, baking, heating water, running machines… and reducing your carbon footprint.

I have recently become the latest guinea pig for Dominic Wanjihias experiments … and it has been quite a learning experience

Problem No. 1.The system needs to be cheap and mobile for communities who don’t own land or who move regularly (pastoralists)

Simply Logic flexi -bag for biogas - small, cheap and made of parts you can find in any hardware
Biogas system on a motorbike in Kenya
You may need a Dominic to help set it up
It can be dirty work - but don't let that discourage you...

After only 2 weeks it will have ballooned like this

After only 2 weeks the bag will have inflated with methane - beautiful biogas
Great party trick: The biogas will burn and amaze

Problem No. 2. The pressure is not enough to light a stove. Nothing ever works as you initially planned that’s why having a fundi like Dominic around to modify, adapt and rethink as you go along helps so much.

To create pressure Dominic got two tanks, and did some juakali pipe connections. One tank was placed above the other. The lower tank was filled with water. Long pipes and short pipes were put through the lids and specially made holes in the tanks …  It’s all about applying simple physics really…

You need a few tools - all available at tusky's or Nakumatt

Then using a pump ..(we’ll be using a modified bicycle pump next time) he was able to move the gas from the flexi bag to the lower tank and displace water to the upper tank. This water creates enough back pressure to get the stove to light.. that’s the theory … here is what happened.

A curious boda boda rider (motorbike taxi) called Victor volunteered to help… Rhoda watched in awe

Victor pumped... others set up the stove

“Houston we have a problem” …Ok, accidents are bound to happen…pressure pushed the pipe off  and Victor got soaked..just water though. The top tank fills with water as you pump biogas into the bottom tank, and the water drains back to the bottom tank as the gas is used

Course all this hard work was not for nothing – we had to make a cup of tea –

It took 15 minutes for the water to boil!

Yes we are very very proud that the system worked so Cheers! a well deserved cup of tea.

We estimate that it took about 1/4 to 1/2 of the gas in one blue tank to boil the kettle – that’s about 1/8th of a cubic meter – and the entire flexi bag contains about 5 cubic meters… which means we have about 10 hours of gas use…..and the stuff is being produced all the time (we had quite some wastage as we fooled around to get the system to work)

Well it all seemed to be going just fine when …pssssssttttt

Houston, we have another problem...we sprung a leak!

Nothing serious but we were losing a bit of gas through one of the lids (holes had been drilled through the  lids to insert pipes) …we  need to fix that before we build up any pressure in that tank.

If you are interested in biogas let us know! Leave a comment.

Recycling – tyres, motorbike wheels and water pumps

What do you get if you cross tractor tyres, motorbike wheels and a water pump? Well, in Africa you could get anything! Here’s an odd combination of things related to water – recycled tractor tyres cut to make water troughs

This contribution is thanks to Bankelele (the very cool Kenyan blogger) who responded to a recent post on tractor tyres with the comment “I found a similar one last week and e-mailed it to hash, but perhaps the pics should be added to this post as its the same use of tractor tyre for livestock water”. He spotted it in Feb 2010 during funeral at a homestead in kapsowar, Kenya (note to Banks – Thanks for this, and next time send me low res pics dude!)

water pump engine used for a grinder
well it works doesn't it?

Here’s another water related gadget – a water pump turned into a grinder – and why not? This was spotted and photographed in Gikomba in Nairobi Kenya by Dominic Wanjihia.

wheel barrow

A modified wheel barrow that makes so much more sense – motorbike tyres and check out the puncture proofing on the wheel below

Puncture proof!

This was spotted on the Limuru  road works near Nairobi Kenya. Have you seen anything interesting that you’d like to contribute to Afrigadget? Don’t be shy! Send it to us – we’d love to get contributions from across the continent.

Fuel saving Sufuria

Here’s another interesting idea from Dominic Wanjihia (see links to his other gadgets below) – the fuel efficient Sufuria. A sufuria is the aluminium pan that is used by virtually everyone in Kenya to make tea, ugali and for cooking vegetables. Like all pots that we use, energy is wasted around the sides of the pot. In Africa this is expensive as fuel be it gas, kerosene or charcoal  is expensive. sufuria 1

This is what it looks like when assembled

Sufuria Kenya afrigadget
Sufuria Kenya afrigadget

This is what it is comprised of – two sufurias to make one efficient one. Basically a hole is cut out of the bigger sufuria – and the piece cut out becomes the lid so nothing is wasted. To wash the sufuria you just dismantle the pieces by just slipping it out. The heat that otherwise escapes around the edge of the pan, is trapped between the cooking pot and  it’s sleeve.

Though it’s not in production, Dominic is using this sufuria at home and swears that it saves at least 50-75% energy on a kerosene stove (his estimate is based on how long it’ takes to boil water).

So if you put a fuel efficient sufuria on a Kinyanjui fuel efficient stove I wonder how much energy saving you could achieve?

Dominic Wanjihia has been previously on Afrigadget showcasing his flat parabolic mirror, container garden, wearable Solar Panel vest, Food dryer, and camel milk cooler.

Evapocooler invention for cooling camels milk in Somalia

Or How to get your camel milk to market in 40 degree C climate.

My brother Dominic Wanjihia invented this gadget which he calls Fine Lined Evaporative Cooler, for rural application in Somalia – the cooling of camels milk for transportation . He was working on a project for VETAID, Somali Pastoral Dairy Development Program – SPDDP,in Burao, Somalia June 2008. All this content belongs to Dominic who has allowed me to post it here- please seek his permission to use this content elsewhere dwanjihia@yahoo.com

Cool-box design Fine Lined Evaporative cooler
Cool-box design Fine Lined Evaporative cooler

Evaporative cooling technology

The evaporative cooling concept has been used for centuries in countless applications. Cooling occurs when a fluid changes state from liquid to vapor. Put simply, evaporation. In order to evaporate, the liquid requires energy or heat. It acquires this heat energy from its immediate surrounding. As the surrounding gives up this heat, it lowers in temperature or cools.

The rate at which evaporation occurs depends largely on two main factors, the amount of heat available and the humidity in the air.

The cooler must also be shaded from direct sunlight otherwise the surfaces absorb UV heat and warms up, becoming ineffective as a cooler.

In short

Evaporative cooling devices work most efficiently in windy, dry and shaded conditions

Charcoal cooler

Everyone knows how to make charcoal fridges. After carrying out extensive tests on evaporative coolers in hot arid Burao, Somaliland, with day temperatures as high as 36OC in the shade, the charcoal would absorb ambient heat from the air and as opposed to cooling, would warm up the interior compartment.

Imagine wearing a wet thick winter jacket under the palms at a breezy beach. The jacket acts as a wetsuit and will insulate your body preventing heat from escaping.

Fine lined cooler

However, imagine wearing a wet skintight t-shirt in similar conditions. The water evaporates quite rapidly and cools your body.

I applied this concept to the cooler prototype pictured and achieved startling results. The cooler would drop as low as 15.5OC at night when temperatures averaged 25OC and maintain under 17OC during the day at average temps of + 32OC.



An elevated metal box is lined interior and exterior with a fabric. In this case I used locally available corrugated galvanized iron sheets for the container and sisal sacking fabric for lining. The upper ends of the fabric overhang in a water trough that rings the top of the cooler. Capillary action causes the water to slowly trickle over the inner and outer surfaces. A small vent keeps the interior air circulating and wind guides or tunnels direct air flow over the exterior surfaces. A low speed small solar powered fan can be incorporated in areas where there is not a constant breeze.

How it works

The circulating air in the interior causes evaporation on the wet surfaces. The necessary energy is acquired from the contents hence cooling them and is transfers to the iron sides.

Wind guides or tunnels direct an airflow over the external sides. The evaporation that occurs acquires energy from the sides causing further cooling of the interior.

Convection current system to increase water bath cooling
Convection current system to increase water bath cooling

Construction design

Cool-box with water-bath interior for rapid milk cooling application– Collection Point Cooler

Walk-in cold-room for vegetable storage

Vehicle mounted for long distance transporters

Features (Comparison to conventional charcoal coolers)

Very simple construction

Corrugated galvanized iron or GI sheets increase the surface area

Wind tunnels guide air flow efficiently over evaporation surfaces

Air flow coolers at tunnel entrances

Being galvanized, the sheets are long lasting

GI sheets are affordable and available in most rural areas

Secondhand sacking fabric is available in virtually every vegetable market

The simple capillary action dripping system replaces more complicated dripping apparatus

Convection current system to increase water-bath cooling efficiency

Cool box design with waterbath for rapid drop in temperature of milk
Cool box design with waterbath for rapid drop in temperature of milk
The design simplified
The design simplified

In hot arid regions, cooling the warm ambient air before it reaches the wet evaporation surfaces increase efficiency. Note. Setup for airflow from either direction

level coolers – achieved low’s of 16OC at ambient temp of 30OC +
level coolers – achieved low’s of 16OC at ambient temp of 30OC +
Rapid Temperature Drop Test 4 lts boiling water in aluminum milk churn placed in water-bath at 16OC
Rapid Temperature Drop Test 4 lts boiling water in aluminum milk churn placed in water-bath at 16OC

For further information and other rural development concepts and innovative designs, Dom can be reached on

mobile tel +254 722 700 530 dwanjihia@yahoo.com