How to operate a small scale biogas digester system

Biodigester operates like a stomach. Everything goes in will have to go out after fermentation. The amount that goes in is about the same with the one you draw out. It has to be systematic and consistent to ensure the digestion system works properly all the time. According to a simple formula I posted previously in this group, for this 160 liter digester, the size of feeding is about 160/50 or to make it simple 150/50 equals to 3 liter. So for 160 liter system, it is advisable to feed 3 liter at a time. To follow a rule of thumb or common practice in feeding you have to apply 1:1 ratio. Best is to mix 1.5 kg of organic waste to 1.5 liter of water or total up to 3 liter there you have 3 liter feed in 1:1 ratio. Next step is taking out 3 liter of existing slurry out as an excretion from the system and add 3 liter of liquid waste into the system as its fresh feed. To ease the process its best if you prepare a 3 liter bucket to be used for the purpose so that you wont just simply do things without knowing the exact volume and jeopardize the stabiliy and equilibrium of the process in years to come.


Design your own small scale biogas digester system at home



 

Large Scale Underground Biogas Digester System Lay out



 

Design and construction of mini biogas digester for family use

The biogas digester is composed of a green house made with hollow sunlight sheet and metal supporting frame, a membrane digester with a gas storage bag combined in one, a stainless steel sink, a stainless steel outlet, a biogas filter and a biogas booster pump:

1. Biogas production of 2m3/day is good enough for a family

2. It is a DIY kit small scale biogas system for convenient transport and easy assembly.

3. It is surface mounted, there is no need for digging or heavy construction.

4. It can be assembled within 2 hours by anyone with manual and video guidance.

5. Treated organic waste locally, use biogas for cooking, electricity or feed garden with nutritious liquid fertilizer.

6. Used for family, farm, restaurant, hotel, resort to treat organic waste, such as food waste, sewage sludge, animal waste.

7. Light weight and easy to install, packed in carton box.

8. Life span more than 10 years - made of stainless steel frame

9. Raw material of green house and PVC biogas storage bag

10. Specification 156*120*195cm

11. Methane Content 65% which is excellent for cooking
 
 
Construction video:
 
 
 
 More info:

DIY kit assemble mini biogas digester for family use


Calculation of feeding ratio for 1000 liter biogas digester

To my understanding 1000 liter/40 = 25 liter. So it is advisable to feed 25 liter of food waste mixed with water. It means, your food waste is already included in that 25 liter. I have read from this elsewhere, the maximum ratio of food waste to water you can apply is 1:1 (though to me its too much for the microbes to handle). Roughly the maximum weight of food waste you can put is 12.5 kg in which you add another half of water to add up to 25 liter as total mixed. However its up to you what level of total solids you want to practice by reducing the food waste within that 25 liter. The more effluent you take out from the digester, the more bacteria you will discard and that may affect whole digestion process and becoming slower in producing gas.

Construction of 45 liter biogas biodigester for beginner

To construct a simple biogas digester in the photo above is easy. The materials you need are readily available at any hardware store near your residential area.

Basically the system consist of:

1. Inoculum
2. Biogas biodigester
3. Biogas storage
4. Connection between biodigester and its biogas storage

Inoculum
Inoculum is a starter for the anerobic fermentation process to begin. It consist of consortium of microbes to help in digesting suitable raw material and able to turn them into biogas and effluent that is more environment friendly within a short period of time compared to conventional aerobic composting.

Biodigester

What is a biodigester? The function is to contain the fermentation process of food waste occurred in an aerobic condition without any oxygen.

Biogas storage
Used tyre tube to contain and store biogas produced from the fermentation.

Connector
A silicon clear host to connect gas produced from biodigester to the storage bag.

Other accessories and materials needed
PVC pipe, silicon gel, plastic and metal valve, etc.

Want to construct your own low cost biogas biodigester ? CLICK HERE!

Inoculum preparation for biogas generation

The most cheapest and easiest way to produce an inoculum is using digestate from working biogas digester. They are consist of active culture with stable activity because consist of varieties of microbes working together or consortium.

Next source is by taking a scoop of slurry or sediment from anaerobic pond. These are also active microbes we can used directly to produce biogas.

If you happen to live nearby cattle farm, dung is another source of microbes that can produce biogas.But to start with cow dung we need to mix it with water and ferment until it mature in which produces biogas.

Do not mistaken biogas with carbon dioxide. Biogas is flammable while CO2 is not.

So to produce biogas you can start with things that already around you.


Want to construct your own biogas biodigester? Click here!