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The beautiful blue flame - BIOGAS!


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Hi all

Thought it is about time that I contribute something to this forum. I wanted to start earlier to show how the project progressed, but I was too worried that it might not work...!

It all started after visiting a youngster close to us in the former Transkei - in the corner of his kitchen was a two-plastic-drum-model biogas digester! With about 2L of cattle manure slurry he was cooking his daily meal on a little gas hob. It was an incredible eye opener for me! The concept was just too simple not to try it at home.

We have been living off-grid on solar since being back on the farm for about 4 years now. It has been great, but the one area of improvement is that i still need to buy LPG for cooking and heating. It is not a huge bill, but on the heating front I would love to do much more to heat up the old farmhouse during wintertime. We have also renovated another 8 cottages/living unit which we rent out as I have shown. All operate off-grid but cook with gas mainly. Generally, as you all know, solar is not good at anything to do with heating and this is where gas generally comes into its own.

Attached photos are of Moeghesi's inhouse digester - pipe off the top, straight to hob - and it works! He also had concrete built one outside - but this was not operational due to a crack/gas leak.

 

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Note the blocks on top - that is the pressure regulation system!

Needless to say - the chap inspired me and off i went to University of Google for a good few months (ask my wife... i was gone-gone). Anyone who has looked at the subject will soon see there are various kinds of anaerobic (without oxygen) digester types each with it's own positives and negatives. Cost was the main concern for me even though I realised I need to get to quite a sizable setup to even think about additional heating as well as supplying cooking gas also to the other cottages. I have long thought of starting up a 'hobby dairy' or some intensive livestock feeding setup and when i then made the link to have biogas from the waste it was another reason to go through the effort as there will be a beautiful synergy.

Without going through all the detail, the biogas model I decided to go with is basically the horizontal operation 'plug-flow' model using a type of 'biobag' as the actual digester. In most instances this is the cheapest way to go bigger with the main downside being insulation in winter. For this reason I put the whole system sub-grade and am busy insulation the roof structure. Even from Moeghesi I learn that wintertime is not great for producing biogas in our region.... The microbes do not like temperatures colder than 10C and also do not like fluctuating day and night temps. Insulation, as well as some winter solar/gas heating, i do realise will be key to adequate winter gas production.

My choice of site was simple - a sloped area, below some old diary infrastructure, which is also quite close to the house/point/s of use. 'Stable' waste will be drained straight into the digesters pre-mixing and mixing tank. On the third photo the in and outlet tanks are being casted.

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On 1/20/2017 at 7:58 PM, DeepBass9 said:

Something you may want to consider, although its a bit late now as you have submerged your digester, but I keep tilapia in a poly tunnel over winter, and the temperature doesn,t go below 22 degrees. Maybe you could adapt that to keep your microbes bubbling.

Wow.. That's interesting. Well, the top half/more than half of the inlet hole is open and as far as i understand one needs to especially warm up the new slurry coming in... so perhaps one can put a tank 'in' this tank above the slurry that is on the way in...

OK, now i read your reply properly... you mean the poly tunnel keep it warm.. Yes, i was thinking about that initially, but i heard to many stories of rats and stuff eventually getting to the bladder en there goes the gas..

 

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Hi plaasjaap, very interesting. I was involved for some time in PFS study of commercial size biogas plant. It did not come off eventually as we could not find sufficient feed material within reasonable distance.

One question, I don't see any flash back arrestor on the system (the one with the blue drums). That's probably not a great idea.

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Ok ,now it is allowing me to add photos again...

So after 'ditch' was finally ready we installed the bag. The next important step was to 'prime' this monster and it took about 10 000L of manure slurry that I carted from a nearby dairyfarm. I don't have a decent slurry pump yet and i realised that the stuff i was sucking is too thin. I then got hold of a tractor trailer load of wasted sorghum silage - we mixed this in with the thin stuff. This stuff just reeked of "potential' energy...!

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By now i had finally connected my first section of gas piping - I used old rigid 32mm water piping. One needs to avoid low points and design the running of your pipes to firstly drain out any moisture - water vapour is always part of the gas coming out and this condensates in the pipe and will eventually block the flow of gas at the lowest points.

Within about three days there was action, a very fat white worm was starting to bloat!

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I had learnt that the first couple of 'bloats' will not be very rich in methane and be mostly CO2, but i still tried to light it at the end every now and again... After day 7 I was getting a wee bit worried that I had build a huge CO2 emitting rumen... I mixed it again (pump the thinnest stuff from the bottom outlet tank back to the inlet tank). The next evening i could hardly believe it when i saw the first signs of a magical blue flame...

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On 1/20/2017 at 8:54 PM, cvzyl said:

Hi plaasjaap, very interesting. I was involved for some time in PFS study of commercial size biogas plant. It did not come off eventually as we could not find sufficient feed material within reasonable distance.

One question, I don't see any flash back arrestor on the system (the one with the blue drums). That's probably not a great idea.

Thanks - yes nothing on that system. it is worth noting that in the original biogas 'bible' (A Chinese Biogas Manual) not a single mention is made of any such thing safety feature or need therefore. And this is after thousands of small scale digesters of various kinds have been operating for decades across the Chinese countryside. Maybe they didn't know of such a measure that can be taken, but I am quite sure if it was a big risk and many explosions happened due to flash backs, it would at least have been mentioned. Anyhow, it is a simple thing to put in yes.

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Since then it has been fun trying to convert every single gas appliance that i can put my hand on to see if it can work on biogas. The Alva space heater took a lot of tweaking but it works (so far only on one panel or so), but even the safety cutoff/thermocouple still operates. What one really needs is a huge variety of different sized jets to swop out - it seems to be a very sensitive matter - just too much or just too little and it won't burn or would only burn sort-of. My wife's Smeg (!) has also been stripped and reassembled and it is now a multi-fuel machine... The oven i couldn't get converted and allowed wifey to keep that on LPG as my (unmentioned...) forecast would be that, even if i got it to work on biogas, it won't be as predictable as LPG heat and there goes those nice nice Red Velvet cakes as well as keeping her on board regarding this exciting new energy source...

Below are the two types of gas (es? - one gas many gasses/gees/gases...;-) burning side-by-side. LPG now suddenly looks green compared to the bluer colour of the biogas. Admittedly, the biogas is lower in 'oempf' so the same size flame is less heat and takes a little longer to get something to the boil. The key is just to get more gas to flow whilst still getting the air mixture right.

And all this time, which we are not cooking or I am not testing the gas it is bubbling out of my over-pressure container... Over time one will probably get a very good idea of how much it is really producing, but a couple of nights ago I left the valve open outside. By the morning it was still blowing out, even though the pressure had dropped from about 20mBar to 5. After plugging it in the burner it still boiled the kettle in no time and that is the cup of coffee you can see above... I haven't yet installed a pressure system (tyres on the bag...) as it is operating at max all the rest of the time. 

Next items to convert are gas geysers (at least Dewhot have indicated they have successfully done this and can supply me with the jets) and then... the generator. The latter probably won't happen too soon.

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4 minutes ago, Energy said:

WOWOW. When you coming down to Paarl?

We have 500 Goats and Many Cows. Would love to do something like this.

All though goat poops not the best?

Jay 

HI Jay

I am in WC in two weeks time... Always keen to help others out. It is really do-able, more so than I ever thought...

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8 hours ago, Energy said:

WOWOW. When you coming down to Paarl?

We have 500 Goats and Many Cows. Would love to do something like this.

All though goat poops not the best?

Jay 

It does work though, I have used that. I think it may be easier to get into a slurry as it is already pellletised.

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13 hours ago, DeepBass9 said:

Awesome!

What was the cost of the system? The major cost apart from the earthworks must have been the bag?

Well... this is the beauty of it (so far...) - I had the bag made and it cost me about 1/5  of the commercial offering of a real 'biobag' or much smaller (1/3) 'jojo' tank type readymade models! That was when i decided it is worth trying it out...

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A dairy farm in our area went big on bio-gas and save plenty. Have a look at http://www.farmersweekly.co.za/agri-technology/farming-for-tomorrow/affordable-sa-bio-digester-powers-local-dairy-farm/

Also if one wants to spend the money and have an easy to install solution try http://www.biogaspro.com/. Perhaps the farmers and others could convert internal combustion engines driving generators and run them on bio-gas. That is what the Basson brothers did resulting in massive savings. I have found home built Indonesian installation videos on Youtube. That is a poor country (almost like South Africa nowadays) so I guess they look for saving money saving methods wherever they can.

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As far as I know, for diesel engines it is as easy as feeding the biogas into the air intake when the engine is running, and then the engine governer regulates the engine speed. You need a bit of diesel still to keep the engine firing though. I presume for petrol you can just pipe the biogas into the engine through the intake and the spark should detonate it. You would have to fiddle with the air/gas mixture though, and I'm not sure how the petrol engine governor will deal with that. . 

I was planning to try something like that with my Lister generator, but haven't got round to it as yet.

 

Those biogaspro solutions look really easy!

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Well... this is the beauty of it (so far...) - I had the bag made and it cost me about 1/5  of the commercial offering of a real 'biobag' or much smaller (1/3) 'jojo' tank type readymade models! That was when i decided it is worth trying it out...


Quick question, what do you do to remove the sulphur from the biogas?

Sent from my SM-N910F using Tapatalk

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