I have been using a template presented by the United Nations Department of Food and Agriculture as a general guide for the creation of the biogas system at the Energy Farm at UBC. This booklet suggested using rubber tire inner tubes as the gas capture system, a suggestion that I eventually chose against at the Energy Farm.

The U.N.’s suggestion is that tire inner tubes are simple to repair, easy to acquire, and can suitably store biogas for later use. While I find this idea appealing in situations of scarcity and as a means of reusing rubber that might be simply thrown out, I feel that taking a little more time to build a drum style gasholder is better overall choice for this biogas system.

The basic design of the dome style gasholder is as follows:

1.Invert a drum so that the holes on the lid face toward the ground

2.Remove or cut off the top of the drum

3.Insert a PVC pipe into one of the holes in the lid so that it stands vertically inside the inverted drum

4.Fill the main drum with water to about 3 inches below the top of the pipe and place another drum inside (inverted so that can collect the gas)

This “floating dome” style of gas collection captures a large amount of gas that is distributed using only one outlet. Moreover, all biogas digesters can have their gas routed to this single gas collecting dome. As the gas collects under the drum, the water acts as a seal so no gas escapes. Weight is put on the top of the second drum in order to determine the pressure of the system when connected to a stove or appliance. As the drum is pushed closer to the water more pressure is created and gas flows out through the PVC pipe toward the appliance.

I inverted a 50 gallon plastic drum, cut the top off, filled it up with water and placed a 20 gallon plastic garbage can to form the gasholder. I liked the fact that I could use plastic in this part of the system because it ensures the long life of the gasholder. While the inside of digesters Ludwig and David had to be painted with a protective paint, the plastic drums need less preparation and are guaranteed not to corrode from the gas.

Gasholder of Prototype Biogas System