Compressing Bio-Gas into LPG Cylinders

Once the BioGas Digester bag full, the maximum Bag pressure should be approx. 1/3 of an Atmosphere!

The first option is to use the bio-gas straight from the digester bag, if the bio-gas is Not used, it should be automatically/slowly released into the Atmosphere by the system's pressure relief valve, that should be a standard inbuilt safety feature, or the Bag will eventually burst.

However, if you find you are not using the bio-gas as it is being generated, for a secure longer term supply of bio-gas, you would be better of compressing the biogas into LPG gas bottles!

As once the digester bladder is full, the gas would otherwise be wasted gas, due to the low pressure release valve automatically venting the bio-gas (Methane) into the atmosphere to stop the bladder/bag from being damaged.

Compressing your biogas enables you to better manage & secure your resource’s, and get you through times when you may not have enough organic matter to produce biogas.

The process of compressing biogas/methane is relatively simple and can be done by a handy person, all that is needed is an old Air compressor (or temporarily convert one), the only tools needed are a Shifting spanner, Thread tape.

Follow these simple steps to compress you BioGas;

1. On your air compressor remove both the inlet & exhaust (pressure) fittings from the Cylinder head.
2. Now fit a female or male hose barb depending on the fittings on the inlet side.
3. Then push the hose coming from the gas Scrubber, directly onto the brass hose barb.
4. The first fitting from the compressor should be a quick shut-off valve (to stop backwards pressure),
5. Then a T-junction is needed to fit a LPG Pressure gauge and a male LPG hose barb.
6. Now all you need is to fit a LPG hose, and the last fitting needed is a LPG Tank end fitting.
7. If you are using a Forklift tank you will need a Forklift end on the Filling hose.
8. Once all that is connected, simply open all valves, and then start the compressor.
9. Run the compressor for a short time, until the pressure gauge builds, then stop the compressor.
10. Close the Quick shut-off valve, that will leave the pressure in the line between the compressor & the LPG bottle.
11. Now Spray all joins with a mixture of water & dish washing detergent, if no bubbles appear, there are no leaks.
12. Now you are ready to safely start filling your gas bottles, watch as the bladder deflates as you fill your LPG tanks.
13. Stop the Compressor before the biogas bag totally deflated, as you don't want to draw liquid into the biogas line!

Now you will have compressed BioGas stored for use via a normal LPG tank, and as such you will only need to use a stand LPG BBQ regulator when de-cantering.