# Consider the following data for a domestic biogas plant: Number of cows = 5 Retention time = 20 days Temperature = 30°C Dry matter consumed = 2 kg/day

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Consider the following data for a domestic biogas plant:

Number of cows = 5

Retention time = 20 days

Temperature = 30°C

Dry matter consumed = 2 kg/day

Biogas yield = 0.24 m3/kg

Efficiency of burner = 60%

Methane proportion = 0.8

Heat of combustion of Methane = 28 MJ/m3

Density of dry material in fluid = 50 kg/m3

The power available from the digester will be nearly

1. 16.2 MJ/clay
2. 24.3 MJ/day
3. 32.3 MJ/day
4. 48.6 MJ/day

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Correct Answer - Option 3 : 32.3 MJ/day

Concept:

The power available from the digester = (Efficiency of burner × heat of combustion of Methane × Methane proportion × volume of biogas)

Volume of biogas = Biogas yield × Total mass of dry matter consumed

Calculation:

Total mass of dry matter consumed = Dry matter consumed × number of cows

= 2 × 5 = 10 kg/day

Volume of biogas = 0.24 × 10 = 2.4 m3/day

The power available from the digester = 0.6 × 28 × 0.8 × 2.4

= 32.256 MJ/day