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close this bookBetter Farming Series 32. Biogas 2: Building a Better Biogas Unit (FAO Better Farming series, 1986, 47 p.)
View the document(introduction...)
View the documentPreface
View the documentIntroduction
Open this folder and view contentsHow to build a better small biogas unit
Open this folder and view contentsPutting in the waste
View the documentTime
Open this folder and view contentsTemperature
View the documentScum
View the documentWhen the gas is made
View the documentTaking care of your biogas unit
View the documentMaking more biogas
Open this folder and view contentsWhat more can you do?

When the gas is made

114. Do not burn the first gas that is made in your biogas unit. It may have air in it and could explode.

115. A few days after the inner tube has begun to swell with gas, open the valve and let out all of the gas that has been collected.

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

117. After the valve is open you will have to force the gas out of the inner tube or tubes.

118. You can force gas out of a tube by rolling it as you were told to do in Item 63 in this booklet, or by putting a weight on it such as pieces of wood or stones.

119. The drawings on the next page show you how to force air out of a biogas unit with one or more inner tubes.

120. When all of the gas is out, close the valve and your biogas unit will begin to collect gas again.

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


Collect gas

122. Now you can attach the gas line to the top of the valve. However, do not open the valve until the inner tube is half full. Later, you can help to push the gas out of the inner tube by putting a few stones or bricks on it.


Attach the gas line

123. Items 108 to 114 in Booklet No. 31 tell you how to use biogas for cooking and how to clean the burner.

124. After all the gas has been made, take the unit apart and empty out the fertilizer. Items 115 to 118 in Booklet No. 31 tell you how to use the fertilizer.

125. However, be sure to keep about 4 litres of the fertilizer to be used as a starter for next time.


Keep fertilizer as a starter

126. Clean the unit carefully and check for leaks.


Check for leaks

127. 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 oil drum with waste

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