Cover Image
close this bookBetter Farming Series 31. Biogas: What it is; How it is Made; How to Use it (FAO Better Farming Series, 1984)
View the document(introduction...)
View the documentPreface
Open this folder and view contentsIntroduction
Open this folder and view contentsHow to build a small biogas unit
Open this folder and view contentsWaste materials
View the documentTime
View the documentCold weather protection
View the documentStirring the waste mixture
View the documentWhen the gas is made
View the documentUsing your biogas
View the documentUsing the fertilizer
View the documentTaking care of your biogas unit
View the documentMaking more biogas

When the gas is made

98. Do not burn the first gas that is made. It may have air in it and could explode.

99. A few days after the small drum has begun to rise, open the valve or clamp or untie the gas line and let out all of the gas that has been collected.


open the valve

100. While you are letting the gas out, be very careful not to have fire near the biogas unit.

101. To let the gas out, push the small drum back down into the waste mixture in the large drum. This will force all gas and air out of your biogas unit. Then, close the valve or clamp or tie the gas line and your biogas unit will begin to collect gas again.


Push the small drum down

102. If you have done this carefully, the next gas that is made will have no air in it and it will be safe to burn. You can burn all the biogas that is made after this. Do not open the unit again until all the gas has been made.

103. After all the gas has been made, take the unit apart and empty out the fertilizer. Keep about 4 litres of the fertilizer to be used as a starter for the next time.


Take the unit apart


Keep fertilizer for starter

104. Clean the unit and check for leaks.


Clean and check for leaks

105. Now fill the unit with new waste material and add the starter. Close the unit tightly and it will begin to make gas again.


Fill with new waste material

106. Remember, every time you start again, do not burn the first gas that is made.