Which one of the following energy sources has the lowest energy content per…
2023
Which one of the following energy sources has the lowest energy content per unit mass?
Answer: B. Biomass — CONCEPTSpecific energy is the useful heat released per unit mass of a fuel, usually compared on the same lower-heating-value basis. A larger value means that…
- A.
Coal
- B.
Biomass
- C.
Hydrogen
- D.
Natural Gas
Show answer & explanation
Correct answer: B
CONCEPT
Specific energy is the useful heat released per unit mass of a fuel, usually compared on the same lower-heating-value basis. A larger value means that one kilogram of the fuel can release more energy. Fuel composition and moisture affect the measured value.
APPLICATION
Using standard approximate heating values for the offered fuels:
Energy source | Typical energy content (MJ/kg) | Value-local explanation |
|---|---|---|
Coal | about 20–30 | Carbon-rich solid fuel; the exact value varies with coal rank. |
Biomass | about 15–20 | Oxygen in the organic material and retained moisture reduce usable heat per kilogram. |
Hydrogen | about 120 | Its combustion releases very high energy relative to its mass. |
Natural gas | about 45–55 | Methane-rich gas has a higher mass-based heating value than solid carbonaceous fuels. |
CROSS-CHECK
The ordering on this common reference basis is biomass < coal < natural gas < hydrogen. This independently confirms biomass as the least energy-dense option by mass; exact values vary with grade and moisture, but the standard comparison retains this ordering.
RESULT
The smallest representative range in this comparison is the biomass range, so biomass has the lowest energy content per unit mass among the offered sources.