4.4.1 Potential Biogas Generation, Utilisation and treatment

This chapter aims to determine the quantity of biogas that can be produced in the given situation, demonstrate how the biogas can be utilised, and offer an example of necessary treatment.

Potential Biogas Generation

To begin with, it is important to determine the potential amount of biogas that can be produced. This can be achieved by referring to the provided table containing all the necessary information.

It is important to note that the design parameters outlined in this training material are solely meant to serve as an illustration for training purposes. Applying these parameters to actual application systems without adequate verification is not recommended.

ParameterValueUnitHow data was obtained
Number of people600Users/dayGiven
Inflow quantity
per person
6.2L/user/dayWater usage survey: 5L/cap/day for cleansing and flushing.

Estimated excreta generation rate 1.2L/cap/day
(Urine 0.9L/cap/day, Faeces: 0.3L/cap/day)
TS13,000mg/LCharacterisation study
VS9,200mg/LCharacterisation study
Specific biogas
0.23m3/kgVSCharacterisation study (BMP test)
Required Assumptions for the Case Study

First, we must determine the amount of organic material supplied into the digester daily, and to do so, we need to calculate the total inflow per day, measured in cubic meters.


IN TOTAL Total inflow per daym³/day
PNumber of people users/day
INPInflow quantity per person m³/day

Further, we need to understand how much organic materials measured as volatile solids (VS) will be added for conversion into biogas.


OLROrganic loading ratekgVS/day
IN TOTAL Total inflow per daym³/day
QVSQuantity of VSmg/L

Finally, we can determine the anticipated amount of biogas. Based on the BMP test, the specific biogas production rate is 0.23 m3/kgVS.


QGASBiogas production ratem³/day
OLROrganic loading ratekgVS/day
BMPBiogas potential m³/kgVS

Potential Biogas Utilization

The survey results indicated that the absence of proper lighting contributed to the perception that the restroom was not secure. The data is presented in the following graph.

Survey Results – Case Study

Based on the observation, it was decided to use the biogas as a lighting source for 8 hours at night.

ParameterValueUnitHow data was obtained
Biogas consumption100L/hManufacturer
Operation of biogas lamp8h 
Required Assumptions for the Case Study

First, we need to calculate how many lamps can be operated with the expected biogas production rate of 7.87m3/day and the biogas consumption of 100L/h/Lamp for 8 hours of light at night.

The biogas production rate is sufficient to supply fuel for nine biogas lamps. The decision was made to allocate two lamps for each female restroom block and one lamp for each male restroom block.


As discussed in the basics of anaerobic digestion, biogas consists of more than just methane or carbon dioxide. It also contains water and hydrogen sulphide, which need to be eliminated. The following table presents the H2S concentration and the biogas lamp tolerance.

Hydrogen Sulphide

Desulphurisation Unit

The following table presents the possible H2S concentration in biogas produced from excreta and the biogas lamp tolerance.

ParameterValueUnitHow data was obtained
H2S tolerance of
a biogas lamp
H2S Concentration4000ppmMeasured from similar
biogas plants in the area
Assumptions for Case Study

The level of H2S in the biogas measures 4000 ppm, which is higher than the acceptable limit. To tackle this issue, a desulphurisation unit must be installed before the biogas lamps. The manufacturer has shared details about the desulphurisation unit, as summarised in the table below.

ParameterValueUnitHow data was obtained
H2S removal efficiency99%Manufacturer
Flow rate<10m3/dManufacturer
Total treatment capacity400m3Manufacturer
Assumptions for Case Study

To proceed, we need to verify the intended concentration of H2S once the desulphurisation process is complete and determine the number of units required to reach the permissible H2S levels.


COUTConcentration OUTPUTppm
CINConcentration INPUTppm
ERRemoval Efficiency%

Based on the result, the concentration level after the desulphurisation unit – at 40 ppm – falls below the acceptable threshold. As a result, a single unit should suffice.

Additionally, we must confirm whether the flow rate of the desulphurisation unit aligns with the anticipated biogas flow rate.

The anticipated biogas production rate of 7.8m3/d falls below the specified maximum flow rate of 10m3/d for the desulphurisation unit, making it compatible.

For planning, we also need to know how frequently the filter needs to be exchanged, which is defined by the total treatment capacity.

To determine how often to change the filter media, divide the treatment capacity by the biogas production rate.

In our situation, replacing the filter media after 51 days is suggested.

Desulphur Unit Technology Providers