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Biomass as an Energy Source

Environmental Engineering · FE Reference Handbook section

Environmental Engineering
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10 exam-style examples
~45 min
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Handbook notes for this section

Definitions and conditions exactly as the handbook states them.

  • Some, but not all, possible combinations of inputs and processes:
  • CELLULOSIC PLANT MATERIAL GASEOUS
  • OILY PLANT MATERIAL FUEL
  • KEY: PHYSICAL PROCESSES CHEMICAL/THERMAL PROCESSES BIOCHEMICAL PROCESSES

Core formulas for this FE topic

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

This section is conceptual; there are no equations to memorise.

Worked exam-style examples

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

Example 1
Biomass as an Energy Source — solve for usable energy output — Biomass as an Energy Source

biomass as an energy source for a waste-to-energy power plant Given biomass mass processed (m) = 17,750 kg/day; higher heating value of biomass (HHV) = 10,180 kJ/kg; conversion efficiency (eta) = 0.5000, determine the usable energy output (E) in kJ/day.

Given

  • biomassmassprocessed(m)=17,750kg/daybiomass mass processed (m) = 17,750 kg/day
  • higherheatingvalueofbiomass(HHV)=10,180kJ/kghigher heating value of biomass (HHV) = 10,180 kJ/kg
  • conversionefficiency(eta)=0.5000conversion efficiency (eta) = 0.5000

Find

usable energy output (E), in kJ/day

Start with the thinking

  • The governing relation printed in this handbook section is Biomass as an Energy Source.
  • Everything except E is given, so isolate E 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.
  • Biomass as an energy source converts the chemical energy of organic feedstock into usable energy at a given conversion efficiency.
Biomass as an energy source conversion0255075100100Feedstock60Conversion45Energy Outputrelative energy

Figure 1 — schematic for Biomass as an Energy Source — solve for usable energy output — Biomass as an Energy Source

Step-by-step solution

  1. Step 1 — State the governing relation:

    E=m×HHV×ηE = m \times HHV \times \eta
  2. Step 2 — Rearrange symbolically for E:

    E=m HHV ηE = m\,HHV\,\eta
  3. Step 3 — List the givens: biomass mass processed (m) = 17,750 kg/day, higher heating value of biomass (HHV) = 10,180 kJ/kg, conversion efficiency (eta) = 0.5000.

  4. Step 4 — Substitute the given values:

    E=17750 10180 0.5000E = 17750\,10180\,0.5000
  5. Step 5 — Evaluate:

    E=90347500 kJ/dayE = 90347500\ \text{kJ/day}
  6. Step 6 — Check: returning E = 90,347,500 kJ/day to

    E=m×HHV×ηE = m \times HHV \times \eta

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

Answer:
E=90347500 kJ/dayE = 90347500\ \text{kJ/day}

Why the other options are there

  • 180,695,000 — kept a factor of two that cancels in the correct rearrangement.
  • 45,173,750 — dropped that same factor in the other direction.
  • 99,382,250 — rounded an intermediate value before the final step.

Reference: FE Handbook — Biomass as an Energy Source

Example 2
Biomass as an Energy Source — solve for biomass mass processed — Biomass as an Energy Source (2)

biomass as an energy source conversion efficiency calculation Given higher heating value of biomass (HHV) = 13,920 kJ/kg; conversion efficiency (eta) = 0.4700; usable energy output (E) = 529,056,000 kJ/day, determine the biomass mass processed (m) in kg/day.

Given

  • higherheatingvalueofbiomass(HHV)=13,920kJ/kghigher heating value of biomass (HHV) = 13,920 kJ/kg
  • conversionefficiency(eta)=0.4700conversion efficiency (eta) = 0.4700
  • usableenergyoutput(E)=529,056,000kJ/dayusable energy output (E) = 529,056,000 kJ/day

Find

biomass mass processed (m), in kg/day

Start with the thinking

  • The governing relation printed in this handbook section is Biomass as an Energy Source.
  • Everything except m is given, so isolate m 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.
  • Biomass as an energy source converts the chemical energy of organic feedstock into usable energy at a given conversion efficiency.
Biomass as an energy source conversion0255075100100Feedstock60Conversion45Energy Outputrelative energy

Figure 2 — schematic for Biomass as an Energy Source — solve for biomass mass processed — Biomass as an Energy Source (2)

Step-by-step solution

  1. Step 1 — State the governing relation:

    E=m×HHV×ηE = m \times HHV \times \eta
  2. Step 2 — Rearrange symbolically for m:

    m=EHHV ηm = \dfrac{E}{HHV\,\eta}
  3. Step 3 — List the givens: higher heating value of biomass (HHV) = 13,920 kJ/kg, conversion efficiency (eta) = 0.4700, usable energy output (E) = 529,056,000 kJ/day.

  4. Step 4 — Substitute the given values:

    m=52905600013920 0.4700m = \dfrac{529056000}{13920\,0.4700}
  5. Step 5 — Evaluate:

    m=80866 kg/daym = 80866\ \text{kg/day}
  6. Step 6 — Check: returning m = 80,866 kg/day to

    E=m×HHV×ηE = m \times HHV \times \eta

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

Answer:
m=80866 kg/daym = 80866\ \text{kg/day}

Why the other options are there

  • 161,731 — kept a factor of two that cancels in the correct rearrangement.
  • 40,433 — dropped that same factor in the other direction.
  • 88,952 — rounded an intermediate value before the final step.

Reference: FE Handbook — Biomass as an Energy Source

Example 3
Biomass as an Energy Source — solve for conversion efficiency — Biomass as an Energy Source (3)

biomass as an energy source from agricultural waste feedstock Given biomass mass processed (m) = 14,860 kg/day; higher heating value of biomass (HHV) = 19,540 kJ/kg; usable energy output (E) = 778,023,000 kJ/day, determine the conversion efficiency (eta).

Given

  • biomassmassprocessed(m)=14,860kg/daybiomass mass processed (m) = 14,860 kg/day
  • higherheatingvalueofbiomass(HHV)=19,540kJ/kghigher heating value of biomass (HHV) = 19,540 kJ/kg
  • usableenergyoutput(E)=778,023,000kJ/dayusable energy output (E) = 778,023,000 kJ/day

Find

conversion efficiency (eta)

Start with the thinking

  • The governing relation printed in this handbook section is Biomass as an Energy Source.
  • Everything except eta is given, so isolate eta 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.
  • Biomass as an energy source converts the chemical energy of organic feedstock into usable energy at a given conversion efficiency.
Biomass as an energy source conversion0255075100100Feedstock60Conversion45Energy Outputrelative energy

Figure 3 — schematic for Biomass as an Energy Source — solve for conversion efficiency — Biomass as an Energy Source (3)

Step-by-step solution

  1. Step 1 — State the governing relation:

    E=m×HHV×ηE = m \times HHV \times \eta
  2. Step 2 — Rearrange symbolically for eta:

    η=Em HHV\eta = \dfrac{E}{m\,HHV}
  3. Step 3 — List the givens: biomass mass processed (m) = 14,860 kg/day, higher heating value of biomass (HHV) = 19,540 kJ/kg, usable energy output (E) = 778,023,000 kJ/day.

  4. Step 4 — Substitute the given values:

    η=77802300014860 19540\eta = \dfrac{778023000}{14860\,19540}
  5. Step 5 — Evaluate:

    η=2.6795\eta = 2.6795
  6. Step 6 — Check: returning eta = 2.6795 to

    E=m×HHV×ηE = m \times HHV \times \eta

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

Answer:
η=2.6795\eta = 2.6795

Why the other options are there

  • 5.3589 — kept a factor of two that cancels in the correct rearrangement.
  • 1.3397 — dropped that same factor in the other direction.
  • 2.9474 — rounded an intermediate value before the final step.

Reference: FE Handbook — Biomass as an Energy Source

Example 4
Biomass as an Energy Source — solve for usable energy output (case 2) — Biomass as an Energy Source (4)

biomass as an energy source for a waste-to-energy power plant Given biomass mass processed (m) = 90,200 kg/day; higher heating value of biomass (HHV) = 10,120 kJ/kg; conversion efficiency (eta) = 0.5400, determine the usable energy output (E) in kJ/day.

Given

  • biomassmassprocessed(m)=90,200kg/daybiomass mass processed (m) = 90,200 kg/day
  • higherheatingvalueofbiomass(HHV)=10,120kJ/kghigher heating value of biomass (HHV) = 10,120 kJ/kg
  • conversionefficiency(eta)=0.5400conversion efficiency (eta) = 0.5400

Find

usable energy output (E), in kJ/day

Start with the thinking

  • The governing relation printed in this handbook section is Biomass as an Energy Source.
  • Everything except E is given, so isolate E 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.
  • Biomass as an energy source converts the chemical energy of organic feedstock into usable energy at a given conversion efficiency.
Biomass as an energy source conversion0255075100100Feedstock60Conversion45Energy Outputrelative energy

Figure 4 — schematic for Biomass as an Energy Source — solve for usable energy output (case 2) — Biomass as an Energy Source (4)

Step-by-step solution

  1. Step 1 — State the governing relation:

    E=m×HHV×ηE = m \times HHV \times \eta
  2. Step 2 — Rearrange symbolically for E:

    E=m HHV ηE = m\,HHV\,\eta
  3. Step 3 — List the givens: biomass mass processed (m) = 90,200 kg/day, higher heating value of biomass (HHV) = 10,120 kJ/kg, conversion efficiency (eta) = 0.5400.

  4. Step 4 — Substitute the given values:

    E=90200 10120 0.5400E = 90200\,10120\,0.5400
  5. Step 5 — Evaluate:

    E=492924960 kJ/dayE = 492924960\ \text{kJ/day}
  6. Step 6 — Check: returning E = 492,924,960 kJ/day to

    E=m×HHV×ηE = m \times HHV \times \eta

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

Answer:
E=492924960 kJ/dayE = 492924960\ \text{kJ/day}

Why the other options are there

  • 985,849,920 — kept a factor of two that cancels in the correct rearrangement.
  • 246,462,480 — dropped that same factor in the other direction.
  • 542,217,456 — rounded an intermediate value before the final step.

Reference: FE Handbook — Biomass as an Energy Source

Example 5
Biomass as an Energy Source — solve for biomass mass processed (case 2) — Biomass as an Energy Source (5)

biomass as an energy source conversion efficiency calculation Given higher heating value of biomass (HHV) = 10,990 kJ/kg; conversion efficiency (eta) = 0.2600; usable energy output (E) = 160,678,000 kJ/day, determine the biomass mass processed (m) in kg/day.

Given

  • higherheatingvalueofbiomass(HHV)=10,990kJ/kghigher heating value of biomass (HHV) = 10,990 kJ/kg
  • conversionefficiency(eta)=0.2600conversion efficiency (eta) = 0.2600
  • usableenergyoutput(E)=160,678,000kJ/dayusable energy output (E) = 160,678,000 kJ/day

Find

biomass mass processed (m), in kg/day

Start with the thinking

  • The governing relation printed in this handbook section is Biomass as an Energy Source.
  • Everything except m is given, so isolate m 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.
  • Biomass as an energy source converts the chemical energy of organic feedstock into usable energy at a given conversion efficiency.
Biomass as an energy source conversion0255075100100Feedstock60Conversion45Energy Outputrelative energy

Figure 5 — schematic for Biomass as an Energy Source — solve for biomass mass processed (case 2) — Biomass as an Energy Source (5)

Step-by-step solution

  1. Step 1 — State the governing relation:

    E=m×HHV×ηE = m \times HHV \times \eta
  2. Step 2 — Rearrange symbolically for m:

    m=EHHV ηm = \dfrac{E}{HHV\,\eta}
  3. Step 3 — List the givens: higher heating value of biomass (HHV) = 10,990 kJ/kg, conversion efficiency (eta) = 0.2600, usable energy output (E) = 160,678,000 kJ/day.

  4. Step 4 — Substitute the given values:

    m=16067800010990 0.2600m = \dfrac{160678000}{10990\,0.2600}
  5. Step 5 — Evaluate:

    m=56232 kg/daym = 56232\ \text{kg/day}
  6. Step 6 — Check: returning m = 56,232 kg/day to

    E=m×HHV×ηE = m \times HHV \times \eta

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

Answer:
m=56232 kg/daym = 56232\ \text{kg/day}

Why the other options are there

  • 112,464 — kept a factor of two that cancels in the correct rearrangement.
  • 28,116 — dropped that same factor in the other direction.
  • 61,855 — rounded an intermediate value before the final step.

Reference: FE Handbook — Biomass as an Energy Source

Example 6
Biomass as an Energy Source — solve for conversion efficiency (case 2) — Biomass as an Energy Source (6)

biomass as an energy source from agricultural waste feedstock Given biomass mass processed (m) = 75,350 kg/day; higher heating value of biomass (HHV) = 10,380 kJ/kg; usable energy output (E) = 927,281,000 kJ/day, determine the conversion efficiency (eta).

Given

  • biomassmassprocessed(m)=75,350kg/daybiomass mass processed (m) = 75,350 kg/day
  • higherheatingvalueofbiomass(HHV)=10,380kJ/kghigher heating value of biomass (HHV) = 10,380 kJ/kg
  • usableenergyoutput(E)=927,281,000kJ/dayusable energy output (E) = 927,281,000 kJ/day

Find

conversion efficiency (eta)

Start with the thinking

  • The governing relation printed in this handbook section is Biomass as an Energy Source.
  • Everything except eta is given, so isolate eta 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.
  • Biomass as an energy source converts the chemical energy of organic feedstock into usable energy at a given conversion efficiency.
Biomass as an energy source conversion0255075100100Feedstock60Conversion45Energy Outputrelative energy

Figure 6 — schematic for Biomass as an Energy Source — solve for conversion efficiency (case 2) — Biomass as an Energy Source (6)

Step-by-step solution

  1. Step 1 — State the governing relation:

    E=m×HHV×ηE = m \times HHV \times \eta
  2. Step 2 — Rearrange symbolically for eta:

    η=Em HHV\eta = \dfrac{E}{m\,HHV}
  3. Step 3 — List the givens: biomass mass processed (m) = 75,350 kg/day, higher heating value of biomass (HHV) = 10,380 kJ/kg, usable energy output (E) = 927,281,000 kJ/day.

  4. Step 4 — Substitute the given values:

    η=92728100075350 10380\eta = \dfrac{927281000}{75350\,10380}
  5. Step 5 — Evaluate:

    η=1.1856\eta = 1.1856
  6. Step 6 — Check: returning eta = 1.1856 to

    E=m×HHV×ηE = m \times HHV \times \eta

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

Answer:
η=1.1856\eta = 1.1856

Why the other options are there

  • 2.3712 — kept a factor of two that cancels in the correct rearrangement.
  • 0.5928 — dropped that same factor in the other direction.
  • 1.3041 — rounded an intermediate value before the final step.

Reference: FE Handbook — Biomass as an Energy Source

Example 7
Biomass as an Energy Source — solve for usable energy output (case 3) — Biomass as an Energy Source (7)

biomass as an energy source for a waste-to-energy power plant Given biomass mass processed (m) = 90,310 kg/day; higher heating value of biomass (HHV) = 12,590 kJ/kg; conversion efficiency (eta) = 0.4300, determine the usable energy output (E) in kJ/day.

Given

  • biomassmassprocessed(m)=90,310kg/daybiomass mass processed (m) = 90,310 kg/day
  • higherheatingvalueofbiomass(HHV)=12,590kJ/kghigher heating value of biomass (HHV) = 12,590 kJ/kg
  • conversionefficiency(eta)=0.4300conversion efficiency (eta) = 0.4300

Find

usable energy output (E), in kJ/day

Start with the thinking

  • The governing relation printed in this handbook section is Biomass as an Energy Source.
  • Everything except E is given, so isolate E 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.
  • Biomass as an energy source converts the chemical energy of organic feedstock into usable energy at a given conversion efficiency.
Biomass as an energy source conversion0255075100100Feedstock60Conversion45Energy Outputrelative energy

Figure 7 — schematic for Biomass as an Energy Source — solve for usable energy output (case 3) — Biomass as an Energy Source (7)

Step-by-step solution

  1. Step 1 — State the governing relation:

    E=m×HHV×ηE = m \times HHV \times \eta
  2. Step 2 — Rearrange symbolically for E:

    E=m HHV ηE = m\,HHV\,\eta
  3. Step 3 — List the givens: biomass mass processed (m) = 90,310 kg/day, higher heating value of biomass (HHV) = 12,590 kJ/kg, conversion efficiency (eta) = 0.4300.

  4. Step 4 — Substitute the given values:

    E=90310 12590 0.4300E = 90310\,12590\,0.4300
  5. Step 5 — Evaluate:

    E=488911247 kJ/dayE = 488911247\ \text{kJ/day}
  6. Step 6 — Check: returning E = 488,911,247 kJ/day to

    E=m×HHV×ηE = m \times HHV \times \eta

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

Answer:
E=488911247 kJ/dayE = 488911247\ \text{kJ/day}

Why the other options are there

  • 977,822,494 — kept a factor of two that cancels in the correct rearrangement.
  • 244,455,624 — dropped that same factor in the other direction.
  • 537,802,372 — rounded an intermediate value before the final step.

Reference: FE Handbook — Biomass as an Energy Source

Example 8
Biomass as an Energy Source — solve for biomass mass processed (case 3) — Biomass as an Energy Source (8)

biomass as an energy source conversion efficiency calculation Given higher heating value of biomass (HHV) = 12,460 kJ/kg; conversion efficiency (eta) = 0.3300; usable energy output (E) = 768,394,000 kJ/day, determine the biomass mass processed (m) in kg/day.

Given

  • higherheatingvalueofbiomass(HHV)=12,460kJ/kghigher heating value of biomass (HHV) = 12,460 kJ/kg
  • conversionefficiency(eta)=0.3300conversion efficiency (eta) = 0.3300
  • usableenergyoutput(E)=768,394,000kJ/dayusable energy output (E) = 768,394,000 kJ/day

Find

biomass mass processed (m), in kg/day

Start with the thinking

  • The governing relation printed in this handbook section is Biomass as an Energy Source.
  • Everything except m is given, so isolate m 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.
  • Biomass as an energy source converts the chemical energy of organic feedstock into usable energy at a given conversion efficiency.
Biomass as an energy source conversion0255075100100Feedstock60Conversion45Energy Outputrelative energy

Figure 8 — schematic for Biomass as an Energy Source — solve for biomass mass processed (case 3) — Biomass as an Energy Source (8)

Step-by-step solution

  1. Step 1 — State the governing relation:

    E=m×HHV×ηE = m \times HHV \times \eta
  2. Step 2 — Rearrange symbolically for m:

    m=EHHV ηm = \dfrac{E}{HHV\,\eta}
  3. Step 3 — List the givens: higher heating value of biomass (HHV) = 12,460 kJ/kg, conversion efficiency (eta) = 0.3300, usable energy output (E) = 768,394,000 kJ/day.

  4. Step 4 — Substitute the given values:

    m=76839400012460 0.3300m = \dfrac{768394000}{12460\,0.3300}
  5. Step 5 — Evaluate:

    m=186875 kg/daym = 186875\ \text{kg/day}
  6. Step 6 — Check: returning m = 186,875 kg/day to

    E=m×HHV×ηE = m \times HHV \times \eta

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

Answer:
m=186875 kg/daym = 186875\ \text{kg/day}

Why the other options are there

  • 373,751 — kept a factor of two that cancels in the correct rearrangement.
  • 93,438 — dropped that same factor in the other direction.
  • 205,563 — rounded an intermediate value before the final step.

Reference: FE Handbook — Biomass as an Energy Source

Example 9
Biomass as an Energy Source — solve for conversion efficiency (case 3) — Biomass as an Energy Source (9)

biomass as an energy source from agricultural waste feedstock Given biomass mass processed (m) = 22,820 kg/day; higher heating value of biomass (HHV) = 11,500 kJ/kg; usable energy output (E) = 236,882,000 kJ/day, determine the conversion efficiency (eta).

Given

  • biomassmassprocessed(m)=22,820kg/daybiomass mass processed (m) = 22,820 kg/day
  • higherheatingvalueofbiomass(HHV)=11,500kJ/kghigher heating value of biomass (HHV) = 11,500 kJ/kg
  • usableenergyoutput(E)=236,882,000kJ/dayusable energy output (E) = 236,882,000 kJ/day

Find

conversion efficiency (eta)

Start with the thinking

  • The governing relation printed in this handbook section is Biomass as an Energy Source.
  • Everything except eta is given, so isolate eta 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.
  • Biomass as an energy source converts the chemical energy of organic feedstock into usable energy at a given conversion efficiency.
Biomass as an energy source conversion0255075100100Feedstock60Conversion45Energy Outputrelative energy

Figure 9 — schematic for Biomass as an Energy Source — solve for conversion efficiency (case 3) — Biomass as an Energy Source (9)

Step-by-step solution

  1. Step 1 — State the governing relation:

    E=m×HHV×ηE = m \times HHV \times \eta
  2. Step 2 — Rearrange symbolically for eta:

    η=Em HHV\eta = \dfrac{E}{m\,HHV}
  3. Step 3 — List the givens: biomass mass processed (m) = 22,820 kg/day, higher heating value of biomass (HHV) = 11,500 kJ/kg, usable energy output (E) = 236,882,000 kJ/day.

  4. Step 4 — Substitute the given values:

    η=23688200022820 11500\eta = \dfrac{236882000}{22820\,11500}
  5. Step 5 — Evaluate:

    η=0.9026\eta = 0.9026
  6. Step 6 — Check: returning eta = 0.9026 to

    E=m×HHV×ηE = m \times HHV \times \eta

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

Answer:
η=0.9026\eta = 0.9026

Why the other options are there

  • 1.8053 — kept a factor of two that cancels in the correct rearrangement.
  • 0.4513 — dropped that same factor in the other direction.
  • 0.9929 — rounded an intermediate value before the final step.

Reference: FE Handbook — Biomass as an Energy Source

Example 10
Biomass as an Energy Source — solve for usable energy output (case 4) — Biomass as an Energy Source (10)

biomass as an energy source for a waste-to-energy power plant Given biomass mass processed (m) = 3,000 kg/day; higher heating value of biomass (HHV) = 15,810 kJ/kg; conversion efficiency (eta) = 0.2500, determine the usable energy output (E) in kJ/day.

Given

  • biomassmassprocessed(m)=3,000kg/daybiomass mass processed (m) = 3,000 kg/day
  • higherheatingvalueofbiomass(HHV)=15,810kJ/kghigher heating value of biomass (HHV) = 15,810 kJ/kg
  • conversionefficiency(eta)=0.2500conversion efficiency (eta) = 0.2500

Find

usable energy output (E), in kJ/day

Start with the thinking

  • The governing relation printed in this handbook section is Biomass as an Energy Source.
  • Everything except E is given, so isolate E 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.
  • Biomass as an energy source converts the chemical energy of organic feedstock into usable energy at a given conversion efficiency.
Biomass as an energy source conversion0255075100100Feedstock60Conversion45Energy Outputrelative energy

Figure 10 — schematic for Biomass as an Energy Source — solve for usable energy output (case 4) — Biomass as an Energy Source (10)

Step-by-step solution

  1. Step 1 — State the governing relation:

    E=m×HHV×ηE = m \times HHV \times \eta
  2. Step 2 — Rearrange symbolically for E:

    E=m HHV ηE = m\,HHV\,\eta
  3. Step 3 — List the givens: biomass mass processed (m) = 3,000 kg/day, higher heating value of biomass (HHV) = 15,810 kJ/kg, conversion efficiency (eta) = 0.2500.

  4. Step 4 — Substitute the given values:

    E=3000 15810 0.2500E = 3000\,15810\,0.2500
  5. Step 5 — Evaluate:

    E=11857500 kJ/dayE = 11857500\ \text{kJ/day}
  6. Step 6 — Check: returning E = 11,857,500 kJ/day to

    E=m×HHV×ηE = m \times HHV \times \eta

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

Answer:
E=11857500 kJ/dayE = 11857500\ \text{kJ/day}

Why the other options are there

  • 23,715,000 — kept a factor of two that cancels in the correct rearrangement.
  • 5,928,750 — dropped that same factor in the other direction.
  • 13,043,250 — rounded an intermediate value before the final step.

Reference: FE Handbook — Biomass as an Energy Source

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