Fuels and Energy Content — Comparing Calorific Value by Fuel Type In practical thermal engineering, is the mass-based calorific value (MJ/kg) of typical liquid fuels (e.g., petrol/gasoline, diesel, kerosene) generally higher than that of common solid fuels (e.g., coal grades, wood, biomass)? Choose the most appropriate response.

Introduction:
The calorific value of a fuel is the heat released by complete combustion of a unit mass (or volume). Comparing typical liquid and solid fuels helps in selecting fuel for boilers, engines, furnaces, and process heaters. The question probes basic fuel science: do common liquid fuels usually exhibit higher calorific value per kilogram than widely used solid fuels?

Given Data / Assumptions:

• Representative liquid fuels: petrol/gasoline, diesel, kerosene, furnace oil.
• Representative solid fuels: air-dried wood, lignite/sub-bituminous coal, bituminous coal, coke, agricultural residues.
• Comparison on a mass basis (MJ/kg), neglecting minor variability due to additives and moisture beyond typical handling conditions.

Concept / Approach:
Calorific value depends on elemental composition, especially carbon and hydrogen content, and on moisture/ash fractions. Liquids refined from petroleum tend to have high hydrogen-to-carbon ratios and low ash, which raise the higher heating value (HHV) per kilogram. Many solid fuels (wood, low-grade coal, biomass) carry higher inherent moisture and ash, lowering effective MJ/kg.

Step-by-Step Solution:
Typical HHV ranges: gasoline ≈ 44–46 MJ/kg; diesel ≈ 44–46 MJ/kg; kerosene ≈ 43–46 MJ/kg.Typical solids: wood (air-dried) ≈ 15–18 MJ/kg; lignite ≈ 10–20 MJ/kg; sub-bituminous/bituminous coal ≈ 20–32 MJ/kg; metallurgical coke ≈ 28–31 MJ/kg.Observation: For the mainstream solid fuels used widely, the MJ/kg is commonly lower than for petroleum liquids. Hence the general statement that liquid fuels have higher calorific value than solid fuels is correct in most practical contexts.

Verification / Alternative check:
Fuel specification sheets and handbooks show petroleum liquids with low ash/moisture and high hydrogen content, which elevate HHV. Even when some high-grade coals approach 32 MJ/kg, they still seldom exceed typical petroleum liquids on a mass basis.

Why Other Options Are Wrong:
Choosing “No” would contradict the majority of field data for commonly used fuels. While niche solids (e.g., certain synthetic char) can be energy-dense, the general engineering rule remains that liquids are higher on a mass basis.

Common Pitfalls:
Mixing mass-based MJ/kg with volume-based MJ/L (where densities differ); ignoring moisture corrections for biomass; assuming all coals have identical quality.

Final Answer:
Yes