NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Technoeconomic comparison of biofuels: 

ethanol, methanol, and gasoline from 

gasification of woody residues

American Chemical 

Society – National 

Meeting

Joan Tarud

Steven Phillips

August 31, 2011

NREL/PR-5100-52636
 NATIONAL RENEWABLE ENERGY LABORATORY

Acknowledgements

U.S. Department of Energy

National Renewable Energy 

Laboratory

Co-Author: Steven Phillips

Internal Assistance Provided By:

– Rich Bain

– Abhijit Dutta

– Andy Aden

– Mary Biddy

– Sara Havig

 Thank you:

2
 NATIONAL RENEWABLE ENERGY LABORATORY

Presentation Overview

• Brief discussion on the three fuels evaluated

• Discussion of equivalent feedstock and front end processes

• For each fuel, discussion of back end processes

• Process comparisons of:

Efficiencies 

Yields

Water usage

• Economic assumptions and results

• Conclusions

3
 NATIONAL RENEWABLE ENERGY LABORATORY

Methanol, Ethanol, and Gasoline

0

20000

40000

60000

80000

100000

120000

140000

Methanol Ethanol Gasoline

Methanol BTUs per Gallon

• Intermediate to other fuels and 

chemicals

Ethanol

• Well into American market 

with 10%-15% ethanol in 

much of the U.S. gasoline

Gasoline

• Today’s primary fuel in the 

U.S. for lightweight vehicles

4

65,000

85,000

120,000
 NATIONAL RENEWABLE ENERGY LABORATORY

Equivalent Front End Processes

Multi-Stage Syngas Compression

Gasification

Tar 

Reforming Scrubbing

Begin with equivalent:

• Feedstock cost of $61.57 per dry U.S. ton ($67.87 per dry metric tonne) 

 (includes capital and operating costs, and dry matter losses

 associated with feed delivery, drying, and handling)

• Plant size of 2,205 dry U.S. tons per day (2,000 dry metric tonnes

 per day) of woody residues 

* Feedstock cost is based on the 2011 Multi-Year Program Plan from the U.S. Department of Energy

5
 NATIONAL RENEWABLE ENERGY LABORATORY

Gasifier

Steam Air

Flue Gas Combustor

Gasification

Low-Pressure, 

Indirectly-Heated, 

Circulating, Fluidized 

Bed Gasifier

Dry 

Wood 

Chips

Synthesis Gas 

and Char

Char

Synthesis Gas

Temperature: 1,600°F (871°C)

Pressure: 20 psi (1.4 bar)

Syngas

Composition

Mole Percent (wet)

H2 (Hydrogen) 13.9

CO2 (Carbon

Dioxide)

7.1

CO (Carbon 

Monoxide)

23.7

H20 (Water) 43.6

CH4 (Methane) 8.6

C2H2 (Acetylene) 0.2

C2H4 (Ethylene) 2.4

C2H6 (Ethane) 0.1

C6H6 (Benzene) 0.07

C10H8 (Tar -

Naphthalene)

0.1

NH3 (Ammonia) 0.2

H2S (Hydrogen 

Sulfide)

0.04

H2:CO molar ratio 0.59

Gasifier Efficiency 72.8% HHV

72.4% LHV

6
 NATIONAL RENEWABLE ENERGY LABORATORY

Tar 

Reforming

Scrubbing

Syngas Cleanup

Tar Reformer: 

• Fluidized bed reactor 

• Containing a nickel catalyst 

• The hydrocarbons are converted to CO 

and H2

Scrubbing:

• Venturi scrubber with a quench 

chamber

• Removes particulates, residual 

ammonia, and residual tars

• Prior to entering the quench, the 

syngas is cooled through heat 

exchange with the steam system from 

1,600°F (871°C) to 140°F (60°C) 

Compound

2012 Targets for Tar and 

Methane Conversion 

Reforming

Methane (CH4) 80%

Ethane (C2H6) 99%

Ethylene (C2H4) 90%

Tars (C10+) 99.9%

Benzene (C6H6) 99%

Ammonia (NH3)a 90%

7
 NATIONAL RENEWABLE ENERGY LABORATORY 8

Ethanol – Back End Processes

Syngas at 

3,000 psia

(207 bar)

Mixed Alcohol 

Synthesis

Alcohol 

Separation

Ethanol

Methanol

Higher 

Alcohols

Mixed Alcohol Synthesis 

• Within the reactor, this mix contacts a metal-sulfide catalyst (Dow’s potassiumpromoted cobalt molybdenum sulfide catalyst)

Acid Gas Removal

• Utilizes a physical solvent, dimethyl ethers of polyethylene glycol (DEPG) to 

remove nearly all of the H2S and a portion of the CO2 

Alcohol Separation

• Molecular sieve removes water

• Two-step distillation for recovery of ethanol and higher alcohol products

Acid Gas 

Removal
 NATIONAL RENEWABLE ENERGY LABORATORY

Gasoline

Gasoline 

Separation

Methanol-to-Gasoline Methanol Synthesis

& Degassing 

Acid Gas 

Removal

Low 

Temperature 

Shift

Syngas at 

745 psia

(51.4 bar)

9

Methanol and Gasoline Back End Processes
 NATIONAL RENEWABLE ENERGY LABORATORY

Acid Gas 

Removal

Low 

Temperature 

Shift

Syngas at 

745 psia

(51.4 bar)

Low Temperature Shift

H2:CO ratio of 2.1 (mole basis) 

A stoichiometric number of 1.75

Acid Gas Removal

Combined AGR and LOCAT systems 

remove the sulfur and CO2 to:

• 2.2 mol% CO2

• 0.06 ppm H2S

10

Low Temperature Shift & Acid Gas Removal
 NATIONAL RENEWABLE ENERGY LABORATORY

• Fixed bed reactor 

containing a copper/zinc 

oxide/alumina catalyst

• Assumed conversion to 

99% methanol 

• After 87 wt% of unconverted 

syngas is recycled to 

methanol synthesis reactor 

inlet

• Operating conditions

• Temperature: 500°F (260°C)

• Pressure: 735 psi (50.7 bar)

Methanol Synthesis

Cleaned 

Syngas

Temperature, °F (°C): 500 (260)

Pressure, psi (bar): 733 (50.5)

Methanol

Synthesis

Reactor Methanol Degassing 

and Dehydration

Columns

Heat Exchange

& Separation

Methanol 

+ Gases

90 (32)

569 (39.2)

Unconverted/Recycled Syngas split 15/85

between AGR and Synthesis Reactor

Dissolved 

Gases

Methanol 

+ Gases

98 (37)

250 (17.2)

To AGR

11
 NATIONAL RENEWABLE ENERGY LABORATORY

Methanol-to-Gasoline Conversion

Air

Methanol

Crude 

Gasoline Vent 

Gas

Inlet Temp: 625°F (329°C)

Exit Temp: 750°F (399°C)

Pressure: 200 psi (13.8 bar)

Fluidized Bed Reactor

12
 NATIONAL RENEWABLE ENERGY LABORATORY

Gasoline from MTG

Temperature oC (oF)

 Reactor Inlet 330 (625)

 Reactor Outlet 400 (752)

Pressure bar(psia)

 Reactor Inlet 14.5 (210)

 Reactor Outlet 12.8 (185)

Yield, wt%

 Hydrocarbons 44

 Water 56

 Total 100

Gasoline Breakdown

 Paraffins 58%

 Olefins 20%

 Aromatics 22%

Crude Hydrocarbon 

Product, wt%

 Light gas 2

 Propane 5

 Propylene 1

 Isobutane 7

 n-Butane 5

 Butenes 1

 C5+ Gasoline 79

 Durene <1

 Total 100

Finished Fuel 

Products, wt% 

 Gasoline 82

 LPG 10

 Fuel Gas 8

 Total 100

13
 NATIONAL RENEWABLE ENERGY LABORATORY

Gasoline Compositions

Crude 

Gasoline

Product

Gasoline

Gasoline

Composition

(Mole 

Percent)

Butanes 3.3

Pentane 22.0

Pentene 3.2

Hexane 18.4

Hexene 2.7

Heptane 6.8

Heptene 4.6

Octane 2.0

Octene 5.0

Nonane 1.8

Nonene 1.8

Benzene 2.6

Toluene 2.3

Xylene 8.8

1,2,4 

Trimethylbenzene

8.7

1,2,4 ,5 

Tetramethylbenzene

0.6

Gasoline

Composition

(Mole 

Percent)

Butanes 16.2

Pentane 15.4

Pentene 2.3

Hexane 12.9

Hexene 1.9

Heptane 4.8

Heptene 3.2

Octane 1.4

Octene 3.6

Nonane 1.2

Nonene 1.3

Benzene 1.8

Toluene 1.6

Xylene 6.2

1,2,4 

Trimethylbenzene

6.0

1,2,4 ,5 

Tetramethylbenzene

0.4

14
 NATIONAL RENEWABLE ENERGY LABORATORY

Process Comparisons

15

Fuel

(Co-Product)

Methanol Ethanol

(Mixed 

Alcohols)

Gasoline

(LPG)

Yield

(gallons/dry U.S. ton feedstock)

130 84

(10)

61

(9)

Production

(million gallons annually)

100 65

(8)

47

(7)

Energy Production

(MMBtu/dry U.S. ton feedstock)

8.4 7.1 7.3

Efficiencies HHV

 LHV

48.9 46.5 48.1

45.8 44.9 48.0

Total Water Usage 

(gallons water/gallon fuel)

 Process Water Usage

 

 Utility Water Usage

1.8 2.6 3.4

1.0 1.2 2.2

0.8 1.4 1.2
 NATIONAL RENEWABLE ENERGY LABORATORY

Economic Assumptions

• Nth plant 

• Equipment was sized and priced based on mass and energy 

data from Aspen Plus simulation

• Discounted cash flow rate of return completed

• Reference year of $2007 U.S.

• 30 year plant life

• 10% internal rate of return

• 40% equity of total plant investment 

• 8% loan rate on remaining 60% debt

• Co-products:

• LPG from Gasoline Process – $1.35/gallon ($0.36/liter) 

co-product credit

• Higher Alcohols from Ethanol Process – $2.11/gallon ($0.56/liter) 

co-product credit

16
 NATIONAL RENEWABLE ENERGY LABORATORY

Methanol Ethanol Gasoline

Total Capital Investment ($MM) 259 516 334

Capital Investment per Annual Gallon 

Gasoline Equivalent

4.7 12.1 7.1

PGP or Minimum Product Selling Price

($/MMBtu, HHV basis) 

($/gallon) 

18.42 24.10 22.66

1.20 2.05 2.72

Economic Results & Comparison

17
 NATIONAL RENEWABLE ENERGY LABORATORY

Summary

18

Methanol Ethanol Gasoline

Energy Content (Btu/gallon) 65,000 85,000 120,000

Efficiencies HHV

 LHV

48.9 46.5 48.1

45.8 44.9 48.0

Yield

(gallons/dry U.S. ton feedstock)

130 84

(10)

61

(9)

Production

(million gallons annually)

100 65

(8)

47

(7)

Total Capital Investment (MM$) 259 516 334

Plant Gate Price ($/MMBtu)

18.42 24.10 22.66

• The energy basis PGPs are within the uncertainties inherent in technoeconomic

 analysis and thus should be considered as the same

• Specific advantages of gasoline fungibility, partnered with comparable process

 efficiencies and economics, warrant further research 
 NATIONAL RENEWABLE ENERGY LABORATORY

Supplemental Information

19
 NATIONAL RENEWABLE ENERGY LABORATORY

Methanol Ethanol Gasoline

Gasification $43,254,246 $43,250,000 $45,620,595

Syngas Cleanup and 

Compression $54,524,041 $136,060,000 $62,628,422

Alcohol Synthesis 

Reaction $7,320,586 $41,420,000 $10,289,705

Alcohol Separation $10,474,820 $20,310,000 $8,695,084

MTG Process $24,802,792

Steam System & Power 

Generation $23,469,623 $46,110,000 $29,562,825

Cooling Water & Other 

Utilities $9,770,000 $9,620,000 $9,980,000

Total Installed 

Equipment Cost (TIC) $148,813,413 $296,780,000 $191,579,578

Total Capital Investment 

(TCI) 259,380,000 516,390,000 333,680,000

20

Capital Costs by Plant Section
 NATIONAL RENEWABLE ENERGY LABORATORY

Tar Reformer Conversions – 2012 Targets

Compound

2012 Targets for Tar and Methane 

Conversion Reforming

Methane (CH4) 80%

Ethane (C2H6) 99%

Ethylene (C2H4) 90%

Tars (C10+) 99.9%

Benzene (C6H6) 99%

Ammonia (NH3)a 90%

21
 NATIONAL RENEWABLE ENERGY LABORATORY

Acid Gas Removal Design Parameters

Acid Gas Removal Parameter Value

Amine used Monoethanolamine (MEA)

Amine concentration 35 wt%

Amine circ. rate 2,261.5 gpm (8,559.8 L/min)

Amine temp. @ absorber 110°F (43.3°C)

Absorber pressure 735 psia (50 atm)

Stripper condenser temperature 212°F (100°C)

Stripper reboiler temperature 230°F (110°C)

Stripper pressure 65 psia (4.4 atm)

Stripper reboiler duty 162 MMBtu/h (171 GJ/h)

Stripper condenser duty 108 MMBtu/h (114 GJ/h)

Amine cooler duty 54.3 MMBtu/h (57.3 GJ/h)

Heat duty per pound CO2 removed 2,650 Btu/lb (6.19 MJ/kg)

CO2 removed 61,170 lb/h (27,746 kg/h)

22
 NATIONAL RENEWABLE ENERGY LABORATORY

Gasoline Comparison

23

55.0 58.6 52.2

10.0

20.3

11.2

10.0

0.0

6.6

25.0 24.2

28.6

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Conventional Gasoline Aspen Model Gasoline M-Gasoline

Paraffins Olefins Cycloparaffins Aromatics
 NATIONAL RENEWABLE ENERGY LABORATORY

C5+ Breakdown for MTG Gasoline

24

Weight %

 PENTANE 14.6

 PENTENE 2.1

 HEXANE 14.6

 HEXENE 2.1

 HEPTANE 6.2

 HEPTENE 4.2

 OCTANE 2.1

 OCTENE 5.2

 NONANE 2.1

 NONENE 2.1

 BENZENE 1.8

 TOLUENE 1.9

 XYLENE 8.6

 124TMB 9.5

 1245TMB 0.7

 ETHBENZ 0.8

 Total 78.5
 NATIONAL RENEWABLE ENERGY LABORATORY

MTG Reaction Conversions (in series)

1 2 METHANOL --> DME + H2O 1.00 13 3 DME --> HEXENE + 3 H2O 0.03

2 9 DME --> 2 124TMB + 9 H2O + 6 H2 0.10 14 2 DME --> BUTENE + 2 H2O 0.02

3 7 DME --> 2 TOLUENE + 7 H2O + 6 H2 0.02 15 DME --> C2H4 + H2O 0.01

4 4 DME --> ETHBENZ + 4 H2O + 3 H2 0.01 16 4 DME + H2 --> OCTANE + 4 H2O 0.04

5 4 DME --> XYLENE + 4 H2O + 3 H2 0.10 17 3 DME + H2 --> HEXANE + 3 H2O 0.26

6 5 DME --> 1245TMB + 5 H2O + 3 H2 0.01 18 2 DME + H2 --> N-C4H10 + 2 H2O 0.30

7 3 DME --> C6H6 + 3 H2O + 3 H2 0.03 19 DME + H2 --> C2H6 + H2O 0.02

8 9 DME --> 2 NONENE + 9 H2O 0.03 20 DME + 2 H2 --> 2 CH4 + H2O 0.03

9 7 DME --> 2 HEPTENE + 7 H2O 0.06 21 7 DME + 2 H2 --> 2 HEPTANE + 7 H2O 0.22

10 5 DME --> 2 PENTENE + 5 H2O 0.03 22 9 DME + 2 H2 --> 2 NONANE + 9 H2O 0.10

11 4 DME --> OCTENE + 4 H2O 0.08 23 5 DME + 2 H2 --> 2 PENTANE + 5 H2O 0.74

12 3 DME --> 2 C3H6 + 3 H2O 0.02 24 3 DME + 2 H2 --> 2 C3H8 + 3 H2O 1.00

25
 NATIONAL RENEWABLE ENERGY LABORATORY 26

Process Comparisons (SI Units)

Fuel

(Co-Product)

Methanol Ethanol

(Mixed 

Alcohols)

Gasoline

(LPG)

Yield

(liters/dry metric tonne feedstock)

542 351

(42)

255

(38)

Production

(million liters annually)

379 246

(30)

178

(26)

Energy Production

(GJ/dry metric tonne feedstock)

9.8 8.3 8.5

Efficiencies HHV

 LHV

48.9 46.5 48.1

45.8 44.9 48.0

Total Water Usage 

(liters water/liter fuel)

 Process Water Usage

 

 Utility Water Usage

1.8 2.6 3.4

1.0 1.2 2.2

0.8 1.4 1.2
 NATIONAL RENEWABLE ENERGY LABORATORY 27

Economic Results & Comparison (SI Units)

Methanol Ethanol Gasoline

Total Capital Investment ($MM) 259 516 334

Capital Investment per Annual Liter 

Gasoline Equivalent

1.2 3.2 1.9

PGP or Minimum Product Selling Price

($/GJ, HHV basis) 

($/liter) 

17.45 22.84 21.48

0.32 0.54 0.72
 NATIONAL RENEWABLE ENERGY LABORATORY 28

Summary (SI Units)

Methanol Ethanol Gasoline

Energy Content (kJ/liter) 18,000 24,000 33,000

Efficiencies HHV

 LHV

48.9 46.5 48.1

45.8 44.9 48.0

Yield

(liters/dry tonne feedstock)

542 351

(42)

255

(38)

Production

(million liters annually)

379 246

(30)

178

(26)

Total Capital Investment (MM$) 259 516 334

Plant Gate Price ($/GJ)

17.45 22.84 21.48