The AGAMA BiogasPro is a simple tank that relies entirely on nature for its operation. Nature provides bacteria that will breakdown organic materials into gas. The owners and operators of the AGAMA BiogasPro are required to feed it, water it and let it build a biomass inside the tank that will work consistently. The biomass needs time to breakdown the organic material, which means that it should remain in the tank long enough for all the bacteria process the matter. The biomass is fairly strong, but it will die if it is poisoned, not fed, not watered or drowned. Each of these four actions may show up in different symptoms.

There are 2 inputs and 2 outputs that can be checked –

Inputs -water and waste going into the digester

Outputs – gas from the top of the digester – this should contain at least 55% methane to burn

Water overflow from the expansion chamber and digester – this contains some nutrients and can be tested for pH, temperature and solid content

Solid feed – preferably wet solids – kitchen waste, sewerage and fresh animal manure

Too much solid feed – gas is produced, but the liquid overflow contains some solids

Too little solid feed – less gas is produced, as the bacteria do not have enough to eat

The solid feed cannot biodegrade – no gas  – the solids fill up the tank, effectively making the tank smaller. This  lowers the time solids spend in contact with the bacteria that produce gas

The solid feed biodegrades slowly – less gas is produced


Water feed:

Too much water fed into the digester –the bacteria has too little time to break down the solids and the biomass can be overflowed from the digester – this leads to less gas to eventually no gas

Too little water fed into the digester –a  scum layer can form on top of liquid that prevents gas being collected in the digester. The gas that is produced is wasted by bubbling out of the expansion chamber

Biomass : this is started when the digester is installed and fed cow manure–it develops and grows over time as it gets used to its feed patterns – how much it is fed, what it can break down, and the temperature it operates in during the different seasons of the year

The biomass is not fed enough – less gas is produced and some bacteria die off

The biomass is fed too much – some of the solids flow through the digester without being broken down

The biomass poisoned – no burnable gas. The remaining bacteria may still produce gases, but not the burnable methane. This must be repaired quickly to save the biomass and continue gas production

The biomass is too cold – the chemical breakdown is slowed down and less methane is produced

Liquid content in digester

Acidic – no gas – smelly

Alkaline – no gas – smelly

Cold – less gas

Hot – high gas production


Trouble shooting

Fault Possible causes Control measures  



1.       Structural tank defects causing water or gas leaks



The tank was purchased with a defect.

The tank was damaged during installation

Ensure appropriate sign-off of the tank delivery.

Ensure certified installation

Replace or repair the tank.

Undertake certified defect repairs

2.       No digestate overflowing from the BiogasPro


Debris in the inlet or inspection risers ( eg plastic bag)

Debris blocking the outlet (eg plastic bag)

Leak in the structure

Blockage from overloading

Not enough water going into the system causing solidification within the tank

Correct operations and maintenance – regular checks for inorganic material

Correct operations and maintenance –

Review loading rates on product datasheet


Remove inorganic material


Ensure that the design volumes are entering the digester

Add water to within design volumes

3.       Effluent backing up sewer pipes or overflowing out of the inlet riser Inroganic debris in inlet chute riser or excessive solid volumes in inlet riser

Solid or inorganic debris blocking riser

Correct operations and maintenance- regular checks for inorganic material

Review loading rates on product datasheet

Remove debris and ensure correct volumes are entering system
4.       Leak in the gas line Incorrect installation

Damaged or broken pipes through vegetation growth into the joints

Perished or corroded components

Ensure that the line is installed to specifications, not close to vegetation growth and with no possibility of trapping condensation water. Ensure that components are operated  and maintained correctly, and weathered components replaced. Contact specialist
5.       Blockage in the gas line Water trapped in pipe. This is usually evidenced by variable flame at the burner

Effluent backing up pipe

Ensure that the gas line is not bent causing a “U”water trap in the line, ensure that the water traps are checked and emptied regularly Contact specialist
6.       Blockage or leak in the sewer line


Incorrect installation

Damaged or broken pipes

Incompatible material lodged in the line


Ensure that scum or protein froth build up has not entered the pipe at the gas outlet Contact plumber

Regular inspections to replace damaged, broken or perished components

7.       Reduction in burning time Review loading rates on product datasheet

Buildup of inorganic material in the tank ( sand, grit etc) causing the capacity to reduce

Ensure only correct amount and type of raw material enters the digester at different times of the year

Replace or repair components


8.       General malfunctioning of the burner Burner parts dirty or corroded ( food often falls into gas outlets, jets get blocked with carbon)

Using an incorrect appliance

Clean ( wire brush) appliance regularly

Use only a purpose built biogas appliance

Clean appliance carefully and gently

Replace appliance if necessary

9.       Irregular flame Incorrect gas/air mixture

Combustibility of gas insufficient

Ensure correct control of the air/gas mixture on the appliance.

Do a pH test to ensure an optimal environment for methane producing bacteria (pH = 6 – 8) exists within the digester

Ensure correct environment for methane producing bacteria
10.   Flame far above the burner Pressure too high

Deposition of carbon on the nozzle

Air/gas ratio incorrect at appliance

Adjust gas valve

Clean nozzle

Adjust air/gas ratio on the burner

11.   Flickering flame Water in the pipe Check the gas pipeline/water trap for trapped water if one exists Ensure that there is no water in the gas line and that the water is removed from the water trap.
12.   No gas pressure at the appliance ( but pressure in the reactor)


Stop valve closed

Leak or blockage in the gas pipeline between the BiogasPro and the burner

Open stop valve

Check for gas leaks or blockages throughout the gas line on leaking joints/couplers or on broken pipes or perished flexi hoses. Caused by sand or tree roots obstructing pipes, or water in the pipe (check for sufficient downhill gradient or the water trap)

Confirm all required valves are open and repair/replace components if necessary
13.   Poisoning of the digester bacteria by toxic substance Toxic substances ( such as acid cleaner) enr=tring the system through sewer or grey water pipes or through contaminated feedstocks Erect appropriate signage to prevent toxic substances entering the system. Use only biodegradable detergents or pesticides

Check for diseased livestock

Stop toxic substances entering the system, introduce fresh uncontaminated feedstock. If bilogy is completely dead, the system should be pumped out and re-commissioned
14.   Foul odour or change of colour of digestate Incorrect pH – risen above 8 or below 6. The biological activity within the system is out of balance Ensure that only prescribed types and volumes of feedstock are used.

Do pH tests monthly and check for contamination by toxic substances

If the pH is below 6, add new and fresh feedstock. If problem persists, contact a specialist
15.   Not enough gas Too little loading

Incorrect feedstock

Lack of liquids impeding hydraulic flow

Too much liquids diluting the mixture

Gas leaking from tank or pipes

Scum build-up in the reactor ( gas cannot penetrate scum layer and reach the gas storage area)


Increase loading to designed input

Change feedstock to designed feedstock

Increase liquid input

Ensure that liquid is not leaking out of the structure

Decrease liquid input

16.   Scum formation within the tank Incorrect raw material feedstock being used. Scum can form within the reactor, restricting or stopping the gas from bubbling up into the gas riser. Instead the gas will bubble out of the inspection riser Ensure that only prescribed (wet, fresh and non-fibrous) raw material feedstock is used. Contact a specialist to break up and remove scum.

Remove gas cap and perform maintenance