Normally cow dung is measured in kg and biogas in m3. 1 kg of cow dung along with an equal quantity of water (1:1) under anaerobic conditions. can vary depending on several factors such as the composition of the feedstock, the temperature of the digester, and the efficiency of the biogas system. Some digesters can yield 20 m3 of biogas per tone of waste while others can yield as much as 800 m3 per tone.

e.g.,

One tone of TS can produce 200 ccm of biogas, so 1 kg of TS will produce 0.2 m3 of Biogas.

One Kg of dung contains about 20% TS.

Now, 1 kg of dung which contains 20% TS will produce, 0.2*0.2 = o.04 m3 of biogas.

1 kg dung will produce 0.04 m3 of biogas.

Hence, 1/0.04 = 25 kgs is required to produce 1 m3 of Biogas.

Density = mass/ volume.

density of biogas is 1.15 kg/m3

mass ( required here is 1 kg )

volume required to make 1 kg biogas = mass ( 1 kg )/ density (1.15 kg/m3) = 0.86 m3.

therefore to produce 1 kg of biogas we need 0.86*25 = 21.7 approx 22 kgs of dung.

Please note the above calculation has been conducted without the addition of water. Generally a 1:1 ratio of feedstock is to water is taken. This will alter the calculations significantly.

Similarly, biogas yield can be calculated on Volatile solid (VS) content, which is a percentage of TS content. Another way is to base your calculations on the Chemical oxygen demand ( COD ) of the substrate. Though COD methods are generally employed for waste water treatment.

Dear John Joe Padua ,

The scientifically correct way to calculate the biomethane CH4 (typically 60% - 80% of dry biogas) production from a broad range of solid organic waste and wastewaters incl. manure is based on volatile solids (VS) or on chemical oxygen demand (COD). The biomethane CH4 production is 0.497 Nm³ CH4 / kg VS removed or 0.350 Nm³ CH4 / kg COD removed. This method is proven in our full scale AD+™ plants worldwide since 1980 which convert up to 99% COD.

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