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Details of the Flexi bag biogas system

I’ve been inundated with requests for more information about the biogas system after my good friend Jagi told all his friends and they told theirs so on … I love social networking but in this case it’s socialnetWORKING.

I got a comment from Stephen Kamau who says

“EYE WITTNESS-This system really works.I bought the system through M-pesa after visiting a home in Transmara where i found Dominic stiring cow shit, and when he explained how it works,i decided to purchase. I installed it myself with my wife giving hand when i needed help and, after three weeks there was more gas than what our kitchen requires.
Thank you for the easiest technology.”

And here’s his proud construction

This blog is for all those people who want a share of Stephens joy.

Everyone who has seen my biogas system above, has asked how to get one. Loads of people want to buy one for their mother back in the village. Yes you can have one!

If you’d like to order it, simply call Dominic 0722 700 530 to place your order  or email him Dominic Wanjihia dwanjihia@yahoo.com.  The costs  vary but range from Ksh 45,000 to 55,000.  Specifics can all be found here on the Simply Logic official website  http://www.biogas.co.ke/

Start with basics. What is biogas?

Biogas is the gas produced by the biological breakdown of organic matter through fermentation. The gas is made up of methane (CH4) and carbon dioxide (CO2). Methane is highly combustible with oxygen when in contact with air. This occurs in anaerobic conditions which is in the absence of oxygen.

Biogas can be produced from a variety of materials such as manure, sewage, garden and kitchen wastes, and yes, your own dung.

Methane biogas burns hotter than butane with a beautiful blue hue – it helps to have someone beautiful to cook for you too (no that’s not me).

Thus, biogas is a low-cost fuel which can be used for any heating purpose, such as cooking and boiling water.

Justification for biogas use in Kenya

Everyone knows that Kenyas forests are disappearing because of charcoal and even though it’s leading to climate change, water shortages and power cuts, yet everyone still uses charcoal!

Some scary facts

  1. It is estimated that wood makes up 95% of domestic energy use in Kenya.
  2. The per capita use of wood is 1 ton per year! Crikey there are more than 40 million of us now!What about next year and the next and on and on….
  3. Natural replacement rates of wood fuel are estimated to be less than 60% – ie wood supplies are disappearing by 40 % each year in Kenya.
  4. Given the above, there will be no (affordable) charcoal in the near future. We need alternative affordable energy.

Most Kenyans have no alternative fuel source to wood fuel. 75% of the population, lives in rural areas with no access to, or money to afford liquid gas or Kerosene. But the good news is that nearly everyone has a cow – or access to one.

Actually biogas can be produced from any biological waste so rural farmers and pastoral communities can produce more than enough energy though biogas if they just had digesters… that’s where we come in

The miracle of Biogas

Before you get too excited let me remind you that biogas is not a new concept. Ancient Persians observed that rotting vegetables produce flammable gas and in 1859 Indians built the first sewage plant in Bombay. Biogas has been used in China for 2,000–3,000 years. It’s just that we in Kenya are ridiculously slow in adopting appropriate and obvious technology.

Two types of biogas digesters have been previously promoted in Kenya. The floating dome type from India and fixed dome types from China. Both are used widely in their home countries but haven’t done all that well here.

Studies have been done to find out why Kenyans don’t take to biogas and have come up with several reasons –

  1. Fixed dome and floating top systems are very expensive to install with costs ranging from Kes 150,000 and upwards for domestic systems. Ie. it’s just too expensive.
  2. They require technical expertise in construction which requires masonry stones and cement. It can take several days or weeks to construct. This adds to the cost and sheer scaryness of it.
  3. Metal parts of the dome are prone to rusting requiring regular repair or replacement
  4. Since it’s a construction, the user must own the land due to the construction requirements
  5. Parts are bulky requiring expensive truck transportation – we all know what a rip off it is to hire a pick up or lorry
  6. Some of the parts are imported and are not locally produced or widely available

Enter the (Dominic) FLEXIGAB biogas digester

Dominic Wanjihia has been scratching his head about the energy problems in rural parts of Kenya. Just think about it, if you are reading this blog you probably have an obvious source of energy, electricity.

All you need is one energy source to provide you with all the conveniences  you need – fridge, stove, hot water, lights. Without electricity your life would be severely compromised – no way to cool and store food, no way to work at night, watch TV, listen to radio, have a hot shower … and most of all, no way to work! But that’s how many Kenyans live. No wonder we are losing so much  productivity.

After seeing piles of dung wasting away at Maasai Manyatta’s, and the owners lamenting the flies, Dominic wondered why they weren’t making and using biogas – afterall, the women spend hours fetching firewood. The simple reason – they didn’t know anything about it.

Building a fixed dome by a manyatta didnt’ seem all that acceptable or convenient, especially if the family moved, and getting materials into remote areas was another challenge.  Then there’s the cost – the underground dome systems cost too many cattle. So started the flow of ideas – the Maasai needed something transportable, cheap and easy to operate,

That’s the true story of how the Flexibag biogas digester was born.

Dominic scratched his head some more, toured the juakali sector for materials, parts, ideas, pipes, and started sewing things together… testing what works and what doesn’t. We did a lot of research on the internet – bags have been used before but they failed due to light weight materials used. After many experiments and failures we now have something that works incredibly well.

The system Dom finally settled on is so simple it made him laugh. It comprises a heavy duty rubber bag as the digester. It sits mostly above ground and uses PVC pipes for inputs and outputs. Plastic gas pipes tap the gas from the digester and transfer it to the point of use. If the volume of gas is low the pressure can be increased by simply adding pressure to the biogas bag by placing 4 – 6 jerrycans full of sand on top (nothing with sharp edges should be used).

Some simple facts about WHY YOU SHOULD GET ONE OF THESE.

  1. It is cheap – Ksh 28,000 (USD 400) Ksh 45,000 (sorry folks I’ve had to update this today for the new and much improved digesters (March 2nd 2011) – check Simply Logic Website for all updates on costings) for the bag and pipes making it affordable for domestic and small businesses (appliances are a separate cost).
  2. Cooking appliances can run directly from the biogas after a slight modification.
  3. It is made from locally available and affordable materials. Ie there is no need for imported parts
  4. Durable – the envelope is made of a very strong rubberized textile which is tear resistant materials. To protected from sunlight with a layer of grass, and from livestock by surrounding with a small fence
  5. It is light weight and easily portable – this system can be quickly transported into rural areas weighing 10 kg and packs small enough to be carried on a bicycle or motorbike.
  6. If you decide to move it, it is easily transferrable. There is no masonry construction involved in setting up this system so the bag can be emptied, rolled up and moved to a new location.
  7. Installation is quick  – the only requirement is to level a patch of ground. the time taken to install build the system is only a few minutes for roll out the envelope and connect pipes.
  8. In the event of rips, tears (vandalism) or broken pipes, repair of the system is easy, quick and cheap (no digging and masonry works)
  9. Biogas production is rapid – being above ground promotes rapid gas production attributed to the high temperatures achievable by direct sun exposure

Let me explain how it works. You add fresh cow dung that has been mashed with water til it’s smooth like porridge into the poop pipe in the foreground. Once in the bag it begins to ferment and move slowly across the digester till it’s “exhausted”. Gas that is formed presses down on the poop and pushes the exhausted  stuff out of the orange pipe in the background. If the gas pressure rises because you aren’t using enough gas, it will simply push more poop out the other end. No, it can’t explode and shower you with wet dung.

We found that two big buckets of dung were enough to keep a household of 3 plus 4 dogs going continuously.

The pipe in the middle is the gas pipe – simply connect that to your gas stove* Note that this sytem will not work on those fancy Hotpoint cooker jobbies, we’re talking about 1 or 2 ring Mekko  type stoves which are specially adapted for biogas which does not come under as much pressure as methane in a tank. Once modified the stove cannot be restored to a methane stove. We have also made special burners for ovens – special is an overstatement, they are so simple you will cry.

10.  The envelope digester will produce and hold up to 5 cubic meters of gas which is adequate for one family cooking needs for 2 days.  As long as dung is added daily the gas production can be maintained.

11.  The capacity of the system is easily expanded – to increase gas capacity (eg for several houses, a village or school), simply add more flexi bags beside the initial one and connect with pipes.

12.  The exhausted dung is emitted by the system automatically and has no bad odour (dung will need to remain in the bag for up to 3 months to be fully digested). It is channeled directly to the farm or vegetable patch where it can be used immediately (no further composting required).

13.  This system can be adapted to include human wastes as well as kitchen wastes.

14.  The cost of Flexibag system will be offset within 2 years afterwhich the cost of gas is free.

I did a simple calculation and worked it out

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

I bet you want to ask, but does the system REALLY work?

Yes it does. I’ve installed one at home and my gas cylinder is now idle. So many people want to know more about thow it works, and especially how to get one. Well, hopefully it’s all in this blog post

Your mother needs one of these

If you would like to see a demonstration, or order one of these, simply call Dominic 0722 730500 to place your order  or email him Dominic Wanjihia dwanjihia@yahoo.com

July 27, 2010 Posted by | biogas | , , , , , , , , , , | 8 Comments

Biogas analysis in my kitchen

I know I’m onto a great thing by running my stoves on biogas, it’s cheap, easy and good for the environment.

Here are some facts about biogas from cow dung:

Cow dung gas is 55-65% methane, 30-35% carbon dioxide, with some hydrogen, nitrogen and other traces.

One cow produces approximately 36 – 68 kg of dung per day!

About one cubic meter of biogas can be generated from 16 kg of cow manure at around 28°C. This is enough gas to cook for a few hours.

One cow produces approximately 32 kg of dung per day – enough to feed a biogas system for an entire family!

We put two massive buckets of dung into our digester and have produced about 4 cubic meters of gas over a period of 3 days. Why is it acting so slow?

There are two things I need to do to improve my biogas system.

1. Find out what inputs are optimal for biogas production – does kitchen waste help?

2. Find out whether temperature or acidity is affecting the production of methane.

I set out to ask if my biogas is really operating at optimal temperatures, and how much methane is actually in the biogas?

My condom experiment yielded gas only from the mashed beans and dung so I tested that to find out if it was producing methane and not some other noxious gas .

After scouring Nairobi’s school lab suppliers I got a thermometer (-10 deg – + 60 deg Centigrade) for a whopping 750/- (almost 10$), a measuring cylinder for Ksh 250/- or 4$ (made in China – Pyrex one was 10 x the price!). I also bought some litmus ph paper (which cost me Ksh1,150 for  a reel (US 20$). I also bought a 50 ml syringe at the school shop for a whopping Ksh 150/- (2) I feel so cheated).

I’m so annoyed because you can use red cabbages to test acidity for free! (if you have red cabbages)

Determination of methane concentration

I found a website (but can’t remember where ) that provided a protocol for testing the concentration of biogas (methane) produced. Sodium hydroxide (caustic soda) reacts with carbon dioxide to produce carbonates.

So simple…

1. Dissolve some caustic soda crystals in 100ml water (watch out the stuff burns – add caustic soda grains to water not the other way round and don’t make it too concentrated – it really burns (experience)

2. Fill syringe with water then squirt most out to remove all gas

3. Put syringe end into the jet of biogas and draw in about 10 – 20 cc gas. Record the amount of gas.

4. Place into the caustic soda solution and draw up another 20 cc. Shake but keep the end of the syringe in the caustic soda solution. Or use a gloved finger to seal the end. Caustic soda burns like a bitch.

5. Now calculate the volume of the gas remaining. The NaOH absorbs all the carbon dioxide so you are left with only methane (in theory).

For our biogas we had 26/30 cc of gas was methane = that is a concentration of 86.7% methane. Not bad eh?

I then took the beans/dung condom, broke it under water, trapped the gas and repeated the experiment. 14/16 cc remained – that’s 87.5% methane. No real difference.

Out door temperature

The bacteria responsible for creating methane don’t like low temperatures. They operate optimally at 20 degrees and higher to 40 degrees. Lower than 10 degrees C and will virtually stop functioning.

Well, its’ the cold season here in Nairobi and our bag is above ground so it’s taking on the air temperature, especially at night.  I took 4 temperatures including waking up at at 3 am and 5 am to measure  the temperature – that’s dedicated!

10 am – 20.5

4 pm – 25

3 am – 15

5 am – 11.5

The generally low temperatures and daily range of 10 degrees centigrade may be pissing our bacteria off…but its the daily fluctuations that are the real problem. The bacteria’s really don’t like temperature shifts of more than 1 degree – no wonder the biogas production has slowed down.

Now I have to find a way of raising the temperature of the biogas plant and keeping it stable. My sister suggested I cover it with hay and sprinkle with water and effective microorganisms so that they start composting and producing heat…another stinky thought to consider. Or, I could simply dig a hole and partially bury the thing……

The problem of acidity

According to people who know, methane producing bacteria prefer neutral or slightly alkaline conditions. Like us humans, they don’t tolerate acidity! To find out hat’s happening to the acidity in the biogas digester I used the super expensive Ph paper that I bought in Nairobi at a swindlers shop on Kijabe Street (if you want home lab supplies don’t go to lab supplies, go to Kijabe street there are tons of stores but avoid the industrial suppliers and head to the school suppliers near Longonot Place – they have very cheap Chinese alternatives).

Well the tests came out in favour of methanogenic bacteria – the contents of the digester are living at a healthy pH of 9 which is rather alkaline.

Or maybe I just need more dung …

To find out more about my biogas installation check out my latest condom experiment on substrates with and the super cheap and very effective flexibag system designed by Dominic Wanjihia – and the motorbike trailer he designed to get dung to my house

July 9, 2010 Posted by | biogas, Kenya | , , , , , | 6 Comments

Biogas bursting with Energy

We’ve been away for a few days and received this email

Subject “Full of goodness, Bursting with energy”

Content – of the email was simply this photo

bursting biogas.jpg

You cant imagine my pride… my cow dung has done that! Wow!

I hope you’ll agree that’s pretty serious expansion if you compare photos of the system just a few days ago. And if it’s your first time to participate in my biogas experiment, then you must check out my condom experiment here.

Well, we finally made fire!biogas fire.jpg

Check it out! I’m so happy 🙂

We all knew it would work – so why were we so impressed when it actually did?

burning.jpg

There’s something quite delicious about making this thing work – but truth be told, while it was fun flaring the gas around and enjoying the warm blue flame, we have come across a snag. The pressure in the bag is insufficient to run my kitchen stove.

So now we have another plan, it involves two bright blue tanks, more pipes, wrenches, glue and a hose… and some rather ingenious ideas of creating pressure using water… watch this space.

Please note that This is a home experiment to create biogas for our home consumption – we (Paula, Peter and Dominic) would love to hear your comments, get your involvement and hear your ideas.

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June 8, 2010 Posted by | carbon emissions, carbon footprint, Climate change, Conservation, green house gases, Kenya | , , , , , | 4 Comments

Flexi-bag Biogas digester is full – Anafura kama mandazi!

Hi folks, it’s only been a week and my biogas digester looks – well positively like a mandazi (a donut like delicious breakfast bread – it’s 6 am and I’m hungry!).

I’m so chuffed with my biogas. Check it out

After 1 week it's looking dangerous - just hoping it wont explode while I'm away

Here it is on day 1.

We are on our way to northern Kenya and had to leave on Tuesday for the 2 day drive – before I left I went to check on my experiment which had gone disgusting, so I chucked it out.  Long story short – cow dung produces the most biogas, kitchen waste simply got fungus and consumed all the gas and sucked the condom into the cup – wondering what the hell I’m on about? Check out the experiment here.

June 2, 2010 Posted by | biogas | , , , , | 2 Comments