A farmer with 6000 pigs plan to use biogas generated from the pig manure to prod
ID: 219168 • Letter: A
Question
A farmer with 6000 pigs plan to use biogas generated from the pig manure to produce heat for the farm house. Assume fattening pig (-60 kg) produce manure contains 0.3 kg matter per day, the density of dry matter in the fluid (as wet manure) is -50 kg/m3. The retention time of the operation is 20 days and a burner efficiency is 0.6, biogas yield per unit day mass of whole input is 0.24 mP/kg, the heat of combustion per unit volume biogas is 20 MJ/m3, please calculate the biogas production m3/day, and the thermal energy provided by the burner MJ/day or kW. (please note that some conditions are not needed) dryExplanation / Answer
Ans. Total dry matter yield in 20 days =
No. of pigs x Dry matter yield per pig per day x No. of days
= 6000 pigs x (0.3 kg pig-1 day-1) x 20 days
= 1800 kg
#I. Biogas production in 20 days = Total dry mass x Biogas yield
= 1800 kg x (0.24 m3 kg-1)
= 432 m3
Now,
Biogas production per day = Biogas production in 20 days / 20 days
= 432 m3 / 20 days
= 21.6 m3/ day
#II. Total energy released per day upon combustion =
Biogas production per day x Enthalpy of combustion
= (21.6 m3 / day) x (20 MJ / m3)
= 432 MJ/ day
# Thermal energy provided by burner = Total energy released x Burner efficiency
= (432 MJ/ day) x 0.6
= 259.2 MJ / day ; [1 day = 86400 sec]
= 259.2 x 103 kJ / 86400 sec
= 0.003 kJ/ s ; [1 kJ/s = 1 kW]
= 0.003 kW
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