|Better Farming Series 32. Biogas 2: Building a Better Biogas Unit (FAO Better Farming series, 1986, 47 p.)|
|How to build a better small biogas unit|
52. As you have been told this unit has an inner tube which holds the gas.
53. If you can get a large truck or tractor inner tube, you will need only one.
54. You can also use tubes from automobiles. However, these are smaller so you will need two or even three.
55. Try to get a large tube because it is easier to attach one large tube than two or three small ones.
56. First check each tube that you are going to use for leaks. Each tube must be airtight. To check a tube for leaks fill it with air.
Fill tube with water
57. Then put the tube in water. You can put it in a pond or in a quiet stream.
58. Turn the tube slowly under the water. Look for air bubbles. If you see any bubbles, mark each place on the tube.
Look for air bubbles
59. Let the tube dry. When it is completely dry, repair all of the leaks.
Repair all leaks
60. Fill the tube with air and put it in the water again to make sure that you have repaired all of the leaks well.
Check again for leaks
61. If there are still leaks, start all over again. It is very important to seal all leaks carefully.
62. When all the leaks are sealed let all of the air out. To do this, unscrew the cap of the air inlet and remove the valve.
Let the air out
63. Roll the tube very tightly. If you have a smooth, round pole, you can roll the tube around this.
64. When the tube is tightly rolled and there is no air in it, screw the cap on the air inlet. This is to keep more air from getting inside.
Screw the cap on the air inlet
When you screw the cap on the air inlet, do not put the valve back, and keep the inner tube rolled up until you attach the short gas line (see Item 70 in this booklet).
65. Now you are ready to attach the gas holder.