Better Farming Series 32. Biogas 2: Building a Better Biogas Unit (FAO Better Farming Series, 1986): Scum

Better Farming Series 32. Biogas 2: Building a Better Biogas Unit (FAO Better Farming Series, 1986)

		(introduction...)
		Preface
		Introduction
		How to build a better small biogas unit
		Putting in the waste
		Time
		Temperature
		Scum
		When the gas is made
		Taking care of your biogas unit
		Making more biogas
		What more can you do?

Scum

110. Sometimes a hard layer of scum may form on top of the waste mixture in your biogas unit. If this happens, less gas will be made and gas will not collect in the inner tube.

Hard layer of scrum

111. If the waste is well mixed before it is put into unit, there will be less chance for scum to form and your biogas unit will make gas well.

112. Scum is more likely to form if you use plant materials than if you use only animal waste.

113. To keep scum from forming, shake your biogas unit from time to time. The drawing below shows you how.

Shake the oil drum