Vertical Biogas DIgester Design

 Source: Joel Canaria

 Observe a typical design of a digester.

Inlet - feeding occurs here having the largest diameter among all.

Gas outlet - biogas produced from the process goes out thru here connected to external storage.

Overflow - where slurry displaced by a new feeding goes out thru here.

Stirrer - to make sure agitation takes place. Optional for some practitioner.

Drain - to let the accumulated sediment to flow out thru to be discarded after operating for sometime. 


















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Horizontal Biogas Digester Design

I would like you to check out this design from a friend, more details please check under the QR code. Usually the blue tank converted as biodigester in a vertical form. This is quite different which someone could try on horizontically.

Source: Jørgen Rasmussen (A Clean New World)


 
Or for more explanation please refer to below video:


Floating drum system for biogas storage

 The system consist of two components:

1. The floating drum that has inlet and outlet for biogas. Inlet will let the biogas into the drum to be stored. Outlet is to let the biogas out when it is needed so should there be valve installed to control the process.


2. The base drum that contained water act as a platform for upper drum to float when there is gas produced. A steel guide installed to make sure the floating drum won't fall to the side.



So both drums are of different volume

a. floating drum is 160 liter

b. base drum is 200 liter

source: Biogas DIY FB Group

Biogas digestate as fertilizer

 

No mistake in deciding to pursue biogas generation. Food waste could be managed well environmentally friendly way. Also the byproducts could also useful for agriculture. After digestion the solid waste leftover could be turned into powder after drying and grinding. Inside its already contained beneficial microbes such able to fixing nitrogen in soil. Or its properties could be enhanced more via biotechnology application towards enrichment and value adding of the existing waste material.
 
Your effort will be worth it.
 
But be careful to call your digestate as a biofertilizer make sure it contains beneficial microorganisms (eg. Nitrogen fixing and/or phosphate solubilizing and/or potassium solubilizing, etc) to enhance the properties of the soil where you applied the digestate so that your plant grow better compared to untreated soil. Another thing, biofertilizer should contain enough no. of beneficial microorganism compared to background microflora or otherwise won't show the expected effect if suppressed by other dominant or large no. of other microbes inside the digestate.
 
fresh digestate
 
 
digestate in powder form after drying and grinding
 

 two useful microbes from digestate
 
 

Filtering biogas with water to reduce its carbon dioxide content

 Filtering biogas with water may fulfill two needs:

  1. Biogas mostly consist of CH4 (methane) and CO2 (carbon dioxide). So, filtering with water could lower the percentage of CO2 in your biogas so that it has more CH4 with higher calorific value and shorter time for cooking. Higher CO2 percentage mean you may have much volume of biogas but with little percentage of CH4 end up with longer cooking time. Only CH4 is flammable and not CO2.
  2. Lower CO2 content in your kitchen when cooking inside own house mean healthier environment.


Leak test for biogas digester

Actually leak test should be done before actual run or after you finished fabricating the digester.

Or if you want to perform in the middle of process by putting soap water at joins to see whether are there bubbles formed.


If you cannot do those above just simply paste adhesive like silicon etc or similar adhesive onto all joints to make sure no leaks.