Question Bank • QB_FP_017 NAT • 2 Marks

Section 3: Farm Power

Sources of Power

Subtopic: Sources of power on the farm – human, animal, mechanical, electrical, wind, solar and biomass

Question Statement:

A dairy farm housing 30 mature cows produces $10\text{ kg}$ of collectible fresh wet dung per cow per day. The specific biogas yield of the fresh dung is $0.036\text{ m}^3/\text{kg}$. If the produced biogas has a lower heating value of $20\text{ MJ/m}^3$, the total daily thermal energy potential available from the biogas in $\text{MJ}$ is ________ (answer in integer).

Answer Key:

216

Step-by-Step Solution & Explanation

1. Total fresh dung collected per day: $\text{Dung} = 30 \text{ cows} \times 10\text{ kg/cow/day} = 300\text{ kg/day}$ 2. Daily biogas production: $V_{\text{gas}} = 300\text{ kg/day} \times 0.036\text{ m}^3/\text{kg} = 10.8\text{ m}^3/\text{day}$ 3. Daily thermal energy yield: $E = 10.8\text{ m}^3/\text{day} \times 20\text{ MJ/m}^3 = 216\text{ MJ/day}$
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