mini biogas

8/12/2019 Mini Biogas

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Mini Bio-gas plant using food waste, decomposableorganic material and kitchen wasteI have been searching for some method of using the food waste, decomposable organic material andkitchen waste efficiently, and came across information on producing bio-gas from organic waste.

The bio-gas produced from food waste, decomposable organic material and kitchen waste, consisting of

methane and a little amount of carbon di oxide is an alternative fuel for cooking gas (L!". #lso, thewaste materials can be disposed off efficiently without any odor or flies and the digested slurry from the bio-gas unit can be used as an organic manure in the garden.

$omponents of the %io-gas lant

The ma&or components of the bio-gas plant are a digester tank, an inlet for feeding the kitchen waste, gasholder tank, an outlet for the digested slurry and the gas delivery system for taking out and utili'ing theproduced gas.

This pro&ect is also useful for students to have a hands-on learning experience in constructing a ini %io-!as lant, using locally available material.

aterial )e*uired+

. mpty $ can /0 ltrs capacity+ 1o. (to be used as 2igester Tank"3. mpty $ can 40 ltrs capacity+ no. (to be used as !as 5older Tank" (ake sure the smaller can fitsinside larger one and moves freely"6. 74 mm dia pvc pipe+ about 40 cm long (to be used for feeding waste material"4. 63 mm dia pvc pipe+ about /0 cm long (fixed inside gas holder tank as a guide pipe"/. 3/ mm dia pvc pipe+ about 8/ cm long (fixed inside the digester tank as a guide pipe"7. 63 mm dia pvc pipe+ about 3/ cm long (fixed on digester tank to act as outlet for digested slurry"8. -seal or any water-proof adeshive9. !as outlet system+ lease see :tep 4 below for re*uired materials and construction

Tools re*uired

2o not re*uire many tools here. # hack saw blade for cutting the cans ; pipes and a sharp knife for cuttingholes on the cans are all the tools we need.

#dditional accessories

# single burner bio-gas stove or a%unsen %urner used in school laboratories


2/17

%ought this /0 ltrs capacity$ can, which will act asthe digester unit andremoved the top portion ofthe can, by cutting it with ahack saw blade+

Step 2:

The smaller white can, whichwill act as the gas holder fitsinside the red one. 5ere,again removed the top of thewhite can, also with the helpof a hack saw blade

Step 3:


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74 mm, 63 mm and 3/ mm dia $ pipes which will be used for feeding the kitchen waste, guide pipe forthe gas holder and guide pipe fixed with the digestion chamber respectively. # small piece of 63 mm diapipe will be used as outlet for the slurry+

Step 4:


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. items re*uired for the gas delivery system+ got these items from a hardware store

. %all valve + one no ( to ad&ust the gas flow"3.


5/17

5ere I have marked the cuts to be made in the bottom of the gas collection tank. The smaller hole on the leftfor gas delivery system, center hole for fixing the 63 mm guide pipe and 74 mm hole for fixing the wastefeeding pipe on the right side. ade these holes with the help of a sharp knife and hack saw blade.

The next image is Inside of the gas holder showing the 63 mm guide pipe (center" and the 74 mm feedingpipe fixed with -seal

Step :


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Top view of the gas holder showing the feeding pipe, central guide pipe and the gas delivery system+ I haveclosed the feeding pipe withe an old lid (red one". This will facilitate opening the feed pipe only during

feeding the system.

Step !:


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Digestion tank fitted with the central guide pipe and the outlet pipe for the slurry:

Step ":


8/17

$ompleted unit. I have removed the gas pipe, so that the &oints will get cured without any stress+

>ait for a day or two before feeding the system, allowing all &oints to get cured and become leak-proof.

Initially, cow-dung mixed with water will be fed in to the system, which will start the gas formation process.:ubse*uently, food waste, decomposable organic material and kitchen waste will be diluted with water andused to feed the system. The gas holder will rise along the guide pipes based on the amount of gasproduced. >e can add some weight on top of the gas holder to increase the gas pressure. >hen we feedthe system, the excess digested slurry will fall out through the outlet pipe, which can be collected, dilutedand used as organic manure.

Initial production of gas will consist of oxygen, methane, carbon di oxide and some other gases and will notburn. These gases can be released to the atmosphere by opening the ball valve at least three ? four times.

:ubse*uent gas will consist of about 80 to 90 percent methane and the rest carbon di oxide, which can beused in a single bio-gas burning stove or a %unsen burner.

Total cost of this proto-type system is about one thousand Indian )upees (about 30 dollars"

This is a basic prototype of a %io-gas system using the food waste, decomposable organic material andkitchen waste to produce gas. #n one thousand litre capacity 2igestion tank will be sufficient for a smallhousehold for daily cooking purpose. The bigger commercial models provide a water seal between thedigestion tank and gas holder tank.

@ou can get further information on kitchen waste based mini %io-gas plant at the following links+


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http+??e-biogas.blogspot.in?

http+??www.samuchit.com?index.phpAoptionBcomCcontent;viewBarticle;idB9;ItemidB0

Step #:
http://www.samuchit.com/index.php?option=com_content&view=article&id=8&Itemid=10http://www.samuchit.com/index.php?option=com_content&view=article&id=8&Itemid=10


10/17

$harged the digester tank with cow dung diluted with water. laced the gas holder tank and left it for twothree days. The cow dung slurry started the process of gas forming.

!as formation started and the gas holder tank gets lifted up. I have placed two bricks on top of the gasholder to get more gas pressure.

Step $%:

1ote for students who are doing this as their :chool ro&ect+

. Take guidance from your teacher while using the gas in a stove or %unsen burner.

3. $ollect surplus food and wastage during lunch, dilute and feed the system.

6. Druit peels, extracted tea powder, waste milk and milk products can also be used for feeding the system.

4. 2E 1ET F: eggshells, Enion peels or left-over bones in this system as they will affect the efficient

functioning of the system

/. lant some seedling

7. while feeding, collect the slurry from the outlet, feed the seedlings and watch them grow


11/17

Dirstly, when you add the diluted cow dung ? food waste ? kitchen waste through the inlet pipe, the digested slurrywhich is lighter than the fresh one, will automatically fall out through the outlet pipe. The slurry level inside thedigester will not go beyond the level outlet pipe.

:econdly, the gas will not leak through the guide pipe as the 63 mm dia pipe opening will be always inside theslurry.

Thirdly, mix e*ual amounts of cow dung and water for initial feeding the system. @ou can add as much as the tank

can hold.

Lastly, properly digested slurry will not have any foul smell. If it smells means there is no anaerobic digestion andyou need to empty the system and restart with fresh cow dung slurry

actually it is not necessary to hold up the inner PVC can as the waste feeding system pipe extentsalmost to the bottom of the digester. opening the waste feeding pipe will not allow any gas toescape as the gas holder is immersed in the slurry.

In the bigger systems of about 1000 kg and above capacity a water seal is provided between theslurry and the gas holder which will prevent any gas escape through the outer gap betweendigester and gas holder

Logic is not a common trait in the farmers over here, they would rather &ust dump raw slurry onto the fields ratherthan spend the money to build a digester that could heat their homes for free and help save the environment.There has been about 0,000 gallons of slurry dumped in the field beside my house this week, the smell isatrocious and made me sick on Tuesday, the smell is so bad that you cant open the windows or hang clothes outto dry until it rains hard enough to wash the slurry in.

>hen i researched the bio gas idea a few years ago i found a good idea for a storage system that used 3 waterfilled barrels, one acts as a gas store and the other acts as a water reservoir for the water displaced by the gas asit gathers, the idea is so that you have a constant gas pressure to the burner and no risk of getting flash back tothe digester. #s the gas is burned of the water returns to storage tank from the reservoir and keeps the pressureconstant.

!here are some land fill sites here that are extracting bio gas but the are large scale operations.

In southern Ireland there has been a program to encourage farmers to install methane digesters onfarms there was allot of opposition to the idea due to the e"uipment needed was expensive and

farmed don#t like spending money the problem seems to be that in winter months the process usesalmost all the gas produced to keep the system warm enough to produce gas.

I would like to see more farmers use digested as the digested slurry does not stink the place up

when sprayed on the fields. in the end it all comes down to expense and farmers will not buildmethane digesters until it becomes law most of the farmers here don#t reali$e the potential energy

that they are %ust throwing away most actually pay farm contractors to spread their collected slurryonto the fields.

&o you burn the gas straight off the collector or have you it piped into a storage tank

The bio-gas plant in :ecunderabad cantonment may be a bigger one and I think they may be utili'ing the entireorganic waste from the cantonment. They might have also made some modifications or attachments which willenable the gas to burn in normal L! stove. If you have taken any photographs of the plant please post them herefor reference.

The performance reduction in #)TI or any other bio-gas plant is due to our mistake only. >e normally think that byfeeding more waste material, we may get more gas, but feeding more than the capacity of the digester will makethe slurry acidic and slowly its performance will go down. :ame will happen by feeding onion peels, egg shells andbones in a smaller bio-gas plant as these materials will take very long to get digested.


12/17

)egarding your doubts

. The bio-gas plant I have shown is a prototype with only a /0 kilogram digester tank. >e can feed about 3/0 to600 grams of waste material. which will produce about 00 grams of usable methane gas. ractically, it is verydifficult to use this plant for our day to day chores.

3. The blockers are over-feeding and under-feeding.

6. There is no such thing as initial difficulty. @ou have to start the digestion process with cow dung slurry and sayafter about three to four days, you can start adding kitchen waste. @ou need to release atleast three - four timesthe initial gas produced into atmosphere as this contains more impurities and won


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4" slurry outlet pipe/" gas outlet pipe

Step $: &hose the correct container


14/17

ake holes in the tank for Inlet and outlet. Dor this I took a old iron rod and heated it to make holes.$#FTIE1+ rod is really very hot.

Step 3: 'i( the inlet and outlet pipes


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Step 4: Making the )as holder *ank


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I took a paint bucket of 30 lts for making a gas holder tank. this tank holds the gas produced. The tank isoverturned and fixed with a valve used for plumbing purposes.

Step 5: *ime to mi( the cow dung +


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mix the cow dung in proportion of /0?/0. add /0G water and make a fine slurry. 1ow put the slurry in thedigester tank.

Step : lmost finished+

ut the gas holder tank overturned in the digester tank after adding the slurry . )%)+ open the valvewhile putting the gas holder tank. the mini plant takes 0-/ days for the first time to get output. Dor the firsttime, the gas in the tank wont burn as it contains $arbon 2ioxide gas, if fortunately it burns then good or waitfor the second time. @ou can detect how much gas is there in this system, the gas holder tank will rises upas the gas is produced.

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