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Combustion

Environmental Engineering · FE Reference Handbook section

Environmental Engineering
12 formulas
10 exam-style examples
~60 min
All Environmental Engineering lectures

Handbook notes for this section

Definitions and conditions exactly as the handbook states them.

  • Combustible Substance Reaction Mols lb (kg)*
  • *Substitute the molecular weights in the reaction equation to secure lb (kg). The lb (kg) on each side of the equation must balance.

Core formulas for this FE topic

Definitions, applicability, units, assumptions and worked examples for each relation.

Worked exam-style examples

The four ways this section is written on the real exam — thoughts first, then equations, then substitution.

Example 1
Combustion — solve for higher heating value — Combustion

combustion of municipal solid waste in a waste-to-energy facility Given heat released (Q_fuel) = 326,400 kJ; mass of fuel burned (m_fuel) = 312.0 kg, determine the higher heating value (HHV) in kJ/kg.

Given

  • heatreleased(Qfuel)=326,400kJheat released (Q_fuel) = 326,400 kJ
  • massoffuelburned(mfuel)=312.0kgmass of fuel burned (m_fuel) = 312.0 kg

Find

higher heating value (HHV), in kJ/kg

Start with the thinking

  • The governing relation printed in this handbook section is Combustion.
  • Everything except HHV is given, so isolate HHV symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Combustion of solid waste or fuel releases heat quantified by the higher heating value per unit mass of fuel.

Step-by-step solution

  1. Step 1 — State the governing relation:

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}
  2. Step 2 — Rearrange symbolically for HHV:

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}
  3. Step 3 — List the givens: heat released (Q_fuel) = 326,400 kJ, mass of fuel burned (m_fuel) = 312.0 kg.

  4. Step 4 — Substitute the given values:

    HHV=326400312.0HHV = \dfrac{326400}{312.0}
  5. Step 5 — Evaluate:

    HHV=1046 kJ/kgHHV = 1046\ \text{kJ/kg}
  6. Step 6 — Check: returning HHV = 1,046 kJ/kg to

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}

    reproduces the given quantities, and both sides carry the same units.

Answer:
HHV=1046 kJ/kgHHV = 1046\ \text{kJ/kg}

Why the other options are there

  • 2,092 — kept a factor of two that cancels in the correct rearrangement.
  • 523.1 — dropped that same factor in the other direction.
  • 1,151 — rounded an intermediate value before the final step.

Reference: FE Handbook — Combustion

Example 2
Combustion — solve for heat released — Combustion (2)

combustion heating value calculation for a fuel sample Given mass of fuel burned (m_fuel) = 901.0 kg; higher heating value (HHV) = 37,990 kJ/kg, determine the heat released (Q_fuel) in kJ.

Given

  • massoffuelburned(mfuel)=901.0kgmass of fuel burned (m_fuel) = 901.0 kg
  • higherheatingvalue(HHV)=37,990kJ/kghigher heating value (HHV) = 37,990 kJ/kg

Find

heat released (Q_fuel), in kJ

Start with the thinking

  • The governing relation printed in this handbook section is Combustion.
  • Everything except Q_fuel is given, so isolate Q_fuel symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Combustion of solid waste or fuel releases heat quantified by the higher heating value per unit mass of fuel.

Step-by-step solution

  1. Step 1 — State the governing relation:

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}
  2. Step 2 — Rearrange symbolically for Q_fuel:

    Qfuel=HHV mfuelQ_{fuel} = HHV\,m_{fuel}
  3. Step 3 — List the givens: mass of fuel burned (m_fuel) = 901.0 kg, higher heating value (HHV) = 37,990 kJ/kg.

  4. Step 4 — Substitute the given values:

    Qfuel=37990 901.0Q_{fuel} = 37990\,901.0
  5. Step 5 — Evaluate:

    Qfuel=34228990 kJQ_{fuel} = 34228990\ \text{kJ}
  6. Step 6 — Check: returning Q_fuel = 34,228,990 kJ to

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}

    reproduces the given quantities, and both sides carry the same units.

Answer:
Qfuel=34228990 kJQ_{fuel} = 34228990\ \text{kJ}

Why the other options are there

  • 68,457,980 — kept a factor of two that cancels in the correct rearrangement.
  • 17,114,495 — dropped that same factor in the other direction.
  • 37,651,889 — rounded an intermediate value before the final step.

Reference: FE Handbook — Combustion

Example 3
Combustion — solve for mass of fuel burned — Combustion (3)

combustion energy release computed from fuel mass and heating value Given heat released (Q_fuel) = 1,994,400 kJ; higher heating value (HHV) = 25,450 kJ/kg, determine the mass of fuel burned (m_fuel) in kg.

Given

  • heatreleased(Qfuel)=1,994,400kJheat released (Q_fuel) = 1,994,400 kJ
  • higherheatingvalue(HHV)=25,450kJ/kghigher heating value (HHV) = 25,450 kJ/kg

Find

mass of fuel burned (m_fuel), in kg

Start with the thinking

  • The governing relation printed in this handbook section is Combustion.
  • Everything except m_fuel is given, so isolate m_fuel symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Combustion of solid waste or fuel releases heat quantified by the higher heating value per unit mass of fuel.

Step-by-step solution

  1. Step 1 — State the governing relation:

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}
  2. Step 2 — Rearrange symbolically for m_fuel:

    mfuel=QfuelHHVm_{fuel} = \dfrac{Q_{fuel}}{HHV}
  3. Step 3 — List the givens: heat released (Q_fuel) = 1,994,400 kJ, higher heating value (HHV) = 25,450 kJ/kg.

  4. Step 4 — Substitute the given values:

    mfuel=199440025450m_{fuel} = \dfrac{1994400}{25450}
  5. Step 5 — Evaluate:

    mfuel=78.3654 kgm_{fuel} = 78.3654\ \text{kg}
  6. Step 6 — Check: returning m_fuel = 78.3654 kg to

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}

    reproduces the given quantities, and both sides carry the same units.

Answer:
mfuel=78.3654 kgm_{fuel} = 78.3654\ \text{kg}

Why the other options are there

  • 156.7 — kept a factor of two that cancels in the correct rearrangement.
  • 39.1827 — dropped that same factor in the other direction.
  • 86.2020 — rounded an intermediate value before the final step.

Reference: FE Handbook — Combustion

Example 4
Combustion — solve for higher heating value (case 2) — Combustion (4)

combustion of municipal solid waste in a waste-to-energy facility Given heat released (Q_fuel) = 3,555,600 kJ; mass of fuel burned (m_fuel) = 646.0 kg, determine the higher heating value (HHV) in kJ/kg.

Given

  • heatreleased(Qfuel)=3,555,600kJheat released (Q_fuel) = 3,555,600 kJ
  • massoffuelburned(mfuel)=646.0kgmass of fuel burned (m_fuel) = 646.0 kg

Find

higher heating value (HHV), in kJ/kg

Start with the thinking

  • The governing relation printed in this handbook section is Combustion.
  • Everything except HHV is given, so isolate HHV symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Combustion of solid waste or fuel releases heat quantified by the higher heating value per unit mass of fuel.

Step-by-step solution

  1. Step 1 — State the governing relation:

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}
  2. Step 2 — Rearrange symbolically for HHV:

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}
  3. Step 3 — List the givens: heat released (Q_fuel) = 3,555,600 kJ, mass of fuel burned (m_fuel) = 646.0 kg.

  4. Step 4 — Substitute the given values:

    HHV=3555600646.0HHV = \dfrac{3555600}{646.0}
  5. Step 5 — Evaluate:

    HHV=5504 kJ/kgHHV = 5504\ \text{kJ/kg}
  6. Step 6 — Check: returning HHV = 5,504 kJ/kg to

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}

    reproduces the given quantities, and both sides carry the same units.

Answer:
HHV=5504 kJ/kgHHV = 5504\ \text{kJ/kg}

Why the other options are there

  • 11,008 — kept a factor of two that cancels in the correct rearrangement.
  • 2,752 — dropped that same factor in the other direction.
  • 6,054 — rounded an intermediate value before the final step.

Reference: FE Handbook — Combustion

Example 5
Combustion — solve for heat released (case 2) — Combustion (5)

combustion heating value calculation for a fuel sample Given mass of fuel burned (m_fuel) = 710.0 kg; higher heating value (HHV) = 28,590 kJ/kg, determine the heat released (Q_fuel) in kJ.

Given

  • massoffuelburned(mfuel)=710.0kgmass of fuel burned (m_fuel) = 710.0 kg
  • higherheatingvalue(HHV)=28,590kJ/kghigher heating value (HHV) = 28,590 kJ/kg

Find

heat released (Q_fuel), in kJ

Start with the thinking

  • The governing relation printed in this handbook section is Combustion.
  • Everything except Q_fuel is given, so isolate Q_fuel symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Combustion of solid waste or fuel releases heat quantified by the higher heating value per unit mass of fuel.

Step-by-step solution

  1. Step 1 — State the governing relation:

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}
  2. Step 2 — Rearrange symbolically for Q_fuel:

    Qfuel=HHV mfuelQ_{fuel} = HHV\,m_{fuel}
  3. Step 3 — List the givens: mass of fuel burned (m_fuel) = 710.0 kg, higher heating value (HHV) = 28,590 kJ/kg.

  4. Step 4 — Substitute the given values:

    Qfuel=28590 710.0Q_{fuel} = 28590\,710.0
  5. Step 5 — Evaluate:

    Qfuel=20298900 kJQ_{fuel} = 20298900\ \text{kJ}
  6. Step 6 — Check: returning Q_fuel = 20,298,900 kJ to

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}

    reproduces the given quantities, and both sides carry the same units.

Answer:
Qfuel=20298900 kJQ_{fuel} = 20298900\ \text{kJ}

Why the other options are there

  • 40,597,800 — kept a factor of two that cancels in the correct rearrangement.
  • 10,149,450 — dropped that same factor in the other direction.
  • 22,328,790 — rounded an intermediate value before the final step.

Reference: FE Handbook — Combustion

Example 6
Combustion — solve for mass of fuel burned (case 2) — Combustion (6)

combustion energy release computed from fuel mass and heating value Given heat released (Q_fuel) = 4,998,000 kJ; higher heating value (HHV) = 41,070 kJ/kg, determine the mass of fuel burned (m_fuel) in kg.

Given

  • heatreleased(Qfuel)=4,998,000kJheat released (Q_fuel) = 4,998,000 kJ
  • higherheatingvalue(HHV)=41,070kJ/kghigher heating value (HHV) = 41,070 kJ/kg

Find

mass of fuel burned (m_fuel), in kg

Start with the thinking

  • The governing relation printed in this handbook section is Combustion.
  • Everything except m_fuel is given, so isolate m_fuel symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Combustion of solid waste or fuel releases heat quantified by the higher heating value per unit mass of fuel.

Step-by-step solution

  1. Step 1 — State the governing relation:

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}
  2. Step 2 — Rearrange symbolically for m_fuel:

    mfuel=QfuelHHVm_{fuel} = \dfrac{Q_{fuel}}{HHV}
  3. Step 3 — List the givens: heat released (Q_fuel) = 4,998,000 kJ, higher heating value (HHV) = 41,070 kJ/kg.

  4. Step 4 — Substitute the given values:

    mfuel=499800041070m_{fuel} = \dfrac{4998000}{41070}
  5. Step 5 — Evaluate:

    mfuel=121.7 kgm_{fuel} = 121.7\ \text{kg}
  6. Step 6 — Check: returning m_fuel = 121.7 kg to

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}

    reproduces the given quantities, and both sides carry the same units.

Answer:
mfuel=121.7 kgm_{fuel} = 121.7\ \text{kg}

Why the other options are there

  • 243.4 — kept a factor of two that cancels in the correct rearrangement.
  • 60.8473 — dropped that same factor in the other direction.
  • 133.9 — rounded an intermediate value before the final step.

Reference: FE Handbook — Combustion

Example 7
Combustion — solve for higher heating value (case 3) — Combustion (7)

combustion of municipal solid waste in a waste-to-energy facility Given heat released (Q_fuel) = 3,857,700 kJ; mass of fuel burned (m_fuel) = 500.0 kg, determine the higher heating value (HHV) in kJ/kg.

Given

  • heatreleased(Qfuel)=3,857,700kJheat released (Q_fuel) = 3,857,700 kJ
  • massoffuelburned(mfuel)=500.0kgmass of fuel burned (m_fuel) = 500.0 kg

Find

higher heating value (HHV), in kJ/kg

Start with the thinking

  • The governing relation printed in this handbook section is Combustion.
  • Everything except HHV is given, so isolate HHV symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Combustion of solid waste or fuel releases heat quantified by the higher heating value per unit mass of fuel.

Step-by-step solution

  1. Step 1 — State the governing relation:

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}
  2. Step 2 — Rearrange symbolically for HHV:

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}
  3. Step 3 — List the givens: heat released (Q_fuel) = 3,857,700 kJ, mass of fuel burned (m_fuel) = 500.0 kg.

  4. Step 4 — Substitute the given values:

    HHV=3857700500.0HHV = \dfrac{3857700}{500.0}
  5. Step 5 — Evaluate:

    HHV=7715 kJ/kgHHV = 7715\ \text{kJ/kg}
  6. Step 6 — Check: returning HHV = 7,715 kJ/kg to

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}

    reproduces the given quantities, and both sides carry the same units.

Answer:
HHV=7715 kJ/kgHHV = 7715\ \text{kJ/kg}

Why the other options are there

  • 15,431 — kept a factor of two that cancels in the correct rearrangement.
  • 3,858 — dropped that same factor in the other direction.
  • 8,487 — rounded an intermediate value before the final step.

Reference: FE Handbook — Combustion

Example 8
Combustion — solve for heat released (case 3) — Combustion (8)

combustion heating value calculation for a fuel sample Given mass of fuel burned (m_fuel) = 527.0 kg; higher heating value (HHV) = 44,840 kJ/kg, determine the heat released (Q_fuel) in kJ.

Given

  • massoffuelburned(mfuel)=527.0kgmass of fuel burned (m_fuel) = 527.0 kg
  • higherheatingvalue(HHV)=44,840kJ/kghigher heating value (HHV) = 44,840 kJ/kg

Find

heat released (Q_fuel), in kJ

Start with the thinking

  • The governing relation printed in this handbook section is Combustion.
  • Everything except Q_fuel is given, so isolate Q_fuel symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Combustion of solid waste or fuel releases heat quantified by the higher heating value per unit mass of fuel.

Step-by-step solution

  1. Step 1 — State the governing relation:

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}
  2. Step 2 — Rearrange symbolically for Q_fuel:

    Qfuel=HHV mfuelQ_{fuel} = HHV\,m_{fuel}
  3. Step 3 — List the givens: mass of fuel burned (m_fuel) = 527.0 kg, higher heating value (HHV) = 44,840 kJ/kg.

  4. Step 4 — Substitute the given values:

    Qfuel=44840 527.0Q_{fuel} = 44840\,527.0
  5. Step 5 — Evaluate:

    Qfuel=23630680 kJQ_{fuel} = 23630680\ \text{kJ}
  6. Step 6 — Check: returning Q_fuel = 23,630,680 kJ to

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}

    reproduces the given quantities, and both sides carry the same units.

Answer:
Qfuel=23630680 kJQ_{fuel} = 23630680\ \text{kJ}

Why the other options are there

  • 47,261,360 — kept a factor of two that cancels in the correct rearrangement.
  • 11,815,340 — dropped that same factor in the other direction.
  • 25,993,748 — rounded an intermediate value before the final step.

Reference: FE Handbook — Combustion

Example 9
Combustion — solve for mass of fuel burned (case 3) — Combustion (9)

combustion energy release computed from fuel mass and heating value Given heat released (Q_fuel) = 567,200 kJ; higher heating value (HHV) = 10,220 kJ/kg, determine the mass of fuel burned (m_fuel) in kg.

Given

  • heatreleased(Qfuel)=567,200kJheat released (Q_fuel) = 567,200 kJ
  • higherheatingvalue(HHV)=10,220kJ/kghigher heating value (HHV) = 10,220 kJ/kg

Find

mass of fuel burned (m_fuel), in kg

Start with the thinking

  • The governing relation printed in this handbook section is Combustion.
  • Everything except m_fuel is given, so isolate m_fuel symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Combustion of solid waste or fuel releases heat quantified by the higher heating value per unit mass of fuel.

Step-by-step solution

  1. Step 1 — State the governing relation:

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}
  2. Step 2 — Rearrange symbolically for m_fuel:

    mfuel=QfuelHHVm_{fuel} = \dfrac{Q_{fuel}}{HHV}
  3. Step 3 — List the givens: heat released (Q_fuel) = 567,200 kJ, higher heating value (HHV) = 10,220 kJ/kg.

  4. Step 4 — Substitute the given values:

    mfuel=56720010220m_{fuel} = \dfrac{567200}{10220}
  5. Step 5 — Evaluate:

    mfuel=55.4990 kgm_{fuel} = 55.4990\ \text{kg}
  6. Step 6 — Check: returning m_fuel = 55.4990 kg to

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}

    reproduces the given quantities, and both sides carry the same units.

Answer:
mfuel=55.4990 kgm_{fuel} = 55.4990\ \text{kg}

Why the other options are there

  • 111.0 — kept a factor of two that cancels in the correct rearrangement.
  • 27.7495 — dropped that same factor in the other direction.
  • 61.0489 — rounded an intermediate value before the final step.

Reference: FE Handbook — Combustion

Example 10
Combustion — solve for higher heating value (case 4) — Combustion (10)

combustion of municipal solid waste in a waste-to-energy facility Given heat released (Q_fuel) = 2,621,300 kJ; mass of fuel burned (m_fuel) = 971.0 kg, determine the higher heating value (HHV) in kJ/kg.

Given

  • heatreleased(Qfuel)=2,621,300kJheat released (Q_fuel) = 2,621,300 kJ
  • massoffuelburned(mfuel)=971.0kgmass of fuel burned (m_fuel) = 971.0 kg

Find

higher heating value (HHV), in kJ/kg

Start with the thinking

  • The governing relation printed in this handbook section is Combustion.
  • Everything except HHV is given, so isolate HHV symbolically first — never rearrange after the numbers are in.
  • Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
  • Combustion of solid waste or fuel releases heat quantified by the higher heating value per unit mass of fuel.

Step-by-step solution

  1. Step 1 — State the governing relation:

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}
  2. Step 2 — Rearrange symbolically for HHV:

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}
  3. Step 3 — List the givens: heat released (Q_fuel) = 2,621,300 kJ, mass of fuel burned (m_fuel) = 971.0 kg.

  4. Step 4 — Substitute the given values:

    HHV=2621300971.0HHV = \dfrac{2621300}{971.0}
  5. Step 5 — Evaluate:

    HHV=2700 kJ/kgHHV = 2700\ \text{kJ/kg}
  6. Step 6 — Check: returning HHV = 2,700 kJ/kg to

    HHV=QfuelmfuelHHV = \dfrac{Q_{fuel}}{m_{fuel}}

    reproduces the given quantities, and both sides carry the same units.

Answer:
HHV=2700 kJ/kgHHV = 2700\ \text{kJ/kg}

Why the other options are there

  • 5,399 — kept a factor of two that cancels in the correct rearrangement.
  • 1,350 — dropped that same factor in the other direction.
  • 2,970 — rounded an intermediate value before the final step.

Reference: FE Handbook — Combustion

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