Methane Digester Experiments

Experiment by Tony T (from WoodGas)

A small methane digester that we ran off of chicken manure. It was a very small digester built out of a one gallon pickle jar (glass). As a storage device I used a 12 inch bicycle inner tube.

The fist couple of days the digester is getting rid of the air in the digester and producing CO2, alot of it. After about 3 days CO2 production stops as the bacteria deplete the oxygen and die. After a lull of a couple of days the anaerobic bacteria kick in and start producing methane. I have allowed the system to fill my storage device with CO2 and then I empty it every day (and squeeze out every bit of CO2 by rolling the tube up). By the time it produces methane there is only a very tiny bit of CO2 left in the tube. As I burned the gas for the first few days the fuel quality starts to come up as the rest of the CO2 is "flushed" out of the system with the gas.

This little inner tube would hold enough gas to run my 8hp lawn tractor for about 7 minutes at full throttle. I would hold the tube and squeeze it with my hand to keep the pressure up.

I know that during WWII they would use gas bags and apply a weight to it to keep the pressure up so I assume we can do this with other gases. The only reason I see for compressing the gas is to put more in less space and get longer run times which is more practical than a gas bag/inner tube. If you need a quick easy way to store gas the bag/inner tube would work (IMHO).