Thermochemical Biofuels:

Challenges and Opportunities June 14, 2012

Brent Shanks

Steffenson Professor Chemical & Biological Engineering Department

2

• Petroleum at $90/bbl – Gasoline, wholesale & untaxed ~$2.70/gal – Diesel, wholesale & untaxed ~$3.00/gal – Grain Ethanol, corn at $3 & $6.50/bu $2.40 & $3.80/gge

Some Context

Biofuels Digest, May 11, 2012

3

• Requires consistent capital cost and evaluation bases

• Comparative economics, not business-case economics

• Considered commercial or “near-commercial” technology where possible

• Material and energy balances by Aspen Plus, generally

• Location U.S. Gulf Coast, 2011 $

• Biomass at $5.4/GJ (limit 1 million t/yr/plant)

• Coal at $2/GJ

• Estimates for Nth of a kind plants (N = 5-7)

• Stand-alone plant: Feedstock in; Finished fuels out

• Comparisons are based on best available data; design basis and data are often not very complete

* Jim Katzer (ExxonMobil retired, Iowa State University)

Technology Comparison*

Liquid Transportation Fuels from Coal and Biomass: Technological Status, Costs, and Environmental Impacts, NRC, 2009.

4

Material: Grain (corn) Corn Stover Wood (poplar)

Starch, wt % 72.0 n/m n/m

Cellulose, wt % 2.4 36 40

Hemicellulose, wt % 5.5 26 22

Lignin, wt % 0.2 19 24

Ash, wt % 1.4 12 0.6

Bio-Conversion:

Typical Yields: gge/dry tonne 72 48 50

Thermal-Conversion:

Gasification Yield, gge/dry tonne - 67 72

Pyrolysis Yield, gge/dry tonne - 55 60

Feedstock Cost, $/dry tonne: 255 95 80

Feedstock Cost Component:

Bioconversion, $/gge 3.50* $2.00 $1.60

Gasification, $/gge - $1.40 $1.10

Fast Pyrolysis, $/gge - $1.75 $1.30

Red numbers are first-cut indicator of feedstock cost contribution to product cost

* For Corn at $6.50/bu, DDGS netback reduces this to ~$2.60/gge

Biomass Properties & Fuel Cost Component

FB Gasifier

& Cyclone

Chopping &

Lock hopper

oxygen

biomassTar

Cracking

steam

CO2

Gasification

& Quench

Grinding &

Slurry Prep

oxygen

water

coal

Syngas

Scrubber

Acid Gas

Removal

F-T

Refining

F-T

Synthesis

CO2

FlashRefrigeration

Plant

slag

Flash

methanol

CO2

syngas

Water Gas

Shift

Reg

en

era

tor

H2S + CO2

To Claus/SCOT

HC

Re

co

ve

ry

Recycle

Compr.

finished gasoline &

diesel blendstocks

unconverted syngas+ C1 - C4 FT gases

raw FT

product

Refinery H2 Prod

syncrudelight ends

purge gas Power

Island

net export

electricity

gas

coolingexpander

ATRoxygen steam

dry ash

gas

cooling

Filter

flue gas

• Coal: all components are commercially robust

• Biomass gasification is “essentially commercial”

• Options: Methanol synthesis followed by MTG to produce mainly gasoline, DME

Primarily Finished

Gasoline & Diesel

Some Net

Electricity

Thermochemical: Gasification

Liquid Transportation Fuels from Coal and Biomass: Technological Status, Costs, and Environmental Impacts, NRC, 2009.

6

Thermochemical: Gasification Feedstock Mode Fuel Price, $/gge

– Coal (CTL) Vent CO2 1.75

– Coal CCS 1.90

– Coal/Biomass (40%) (CBTL) Vent CO2 2.75

– Coal/Biomass (40%) CCS 3.00

– Biomass (BTL) vent CO2 3.60

– Biomass CCS 3.85

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

Fu

el C

om

pon

ent

Cost

, $/g

ge

Co-produce Recovery

CO2 Disposal

O & M

Coal Feed

Biomass Feed

Capital Recovery

Fuel Component Cost

Liquid Transportation Fuels from Coal and Biomass: Technological Status, Costs, and Environmental Impacts, NRC, 2009.

7

Biomass Gasification Challenges

• Ash management

• “Tars” conversion

• Scalability

• Reactor technology

– CompactGTL, Syntroleum

– Velocys (25 bpd, May, 2012)

Biomass Fast Pyrolysis*

*Bridgwater et al. in Progress in Thermochemical Biomass Conversion, Bridgwater, ed. (2001) 977.

Biochar

O

O

.c

c.

c.

.c

c.

Cellulose

H2, CO, CH4, CO2

Gas

O

O

OH

OH

OH

O

O

OH

OH

OH

O

OH

O

OHO

OH

O

OH

O

O

O

O

Bio-oil

O

OH

OH

O

HOCH2

O

HO

HO

O

CH2OH

O

OH

OH

O

HOCH2

O

HO

HO

O

CH2OH

O

OH

OH

O

HOCH2

O

OH

OH

O

HOCH2

O

HO

HO

O

CH2OH

O

HO

HO

O

CH2OH

O

OH

OH

O

HOCH2

O

OH

OH

O

HOCH2

O

HO

HO

O

CH2OH

O

HO

HO

O

CH2OH

H2O

Corn stover Bio-oil

Biochar Gas

+ + ~500°C

(~22 GJ m-3) (~1.5 GJ m-3) (~21 MJ kg-1) (~6 MJ kg-1)

Fast Pyrolysis

Composition: Fast Pyrolysis Bio-Oil*

Wt%

Water 20-30

Lignin fragments: insoluble pyrolytic lignin 15-30

Aldehydes: formaldehyde, acetaldehyde, hydroxyacetaldehyde, glyoxal 10-20

Carboxylic acids: formic, acetic, propionic, butyric, pentanoic, hexanoic 10-15

Carbohydrates: cellobiosan, levoglucosan, oligosaccharides 5-10

Phenols: phenol, cresol, guaiacols, syringols 2-5

Furfurals 1-4

Alcohols: methanol, ethanol 2-5

Ketones: acetol (1-hydroxy-2-propanone), cyclopentanone 1-5

*Bridgwater et al.; in Progress in Thermochemical Biomass Conversion, Bridgwater, ed. (2001) 977.

Pyrolysis Severity

Primary Processes Secondary Processes Tertiary Processes

Vapor

Phase

Liquid

Phase

Solid

Phase

Low P

High

P

Low P

High

P

Biomass Charcoal Coke Soot

Primary

Liquids

Primary

Vapors

Light HCs,

Aromatics,

& Oxygenates

Condensed Oils

(phenols, aromatics)

CO, H2,

CO2, H2O

PNA’s, CO,

H2, CO2,

H2O, CH4

Olefins, Aromatics

CO, H2, CO2, H2O

CO, CO2,

H2O

Thermal Conversion Reactions

12

• Fast pyrolysis

– Dynamotive, ENSYN

– Avello

• Catalytic pyrolysis

– KIOR

– Anellotech

• Hydropyrolysis

– GTI

Thermochemical: Pyrolysis

ENSYN, 40 tonne/day

KIOR, 50 ton/day

13

Bio-Oil Upgrading Approach

Water

Wash

Bio-Oil Recovery as

Stage Fractions Biomass

Prep/Pretreatment

Selective thermal

depolymerization

(500º C)

Particulate

Removal

Heavy Ends:

Lignin oligomers

and anhydrosugars

Phenolics and Furans

Light Ends:

Aqueous phase of low MW

carbohydrate-derived

compounds

Anhydro-sugars

Lignin

oligomers

Catalytic

deoxygenation

(200-250º C)

Steam

reforming

(200-250º C)

Ring opening/

deoxygenation

(300-350º C)

Hydrogen

Hydrocarbons

Biomass

Hydrocarbons

Bioasphalt

Lignin-derived

chemicals

14

Schematic of Pyrolyzer–GC/MS System

He

Capillary Separation Column

Gas Chromatograph

Mass Spectrometer

(MS)

Feedstock Pyrolyzer

~ 500 μg

500oC

Cellulose Pyrolysis Products

Anhydro sugars Furans/Pyrans Low mol.

wt. species

Fo

rmic

aci

d

Gly

cola

ldeh

yd

e

Ace

tol

Fu

rfu

ral

Hyd

rox

ym

eth

ylf

urf

ura

l

Lev

og

luco

san

5-m

eth

yl

furf

ura

l

3-f

ura

n m

eth

ano

l 2

-fu

ran

met

han

ol

5-m

eth

yl

furf

ura

l

Ace

tic

acid

Lev

og

luco

san

-fu

ran

ose

An

hyd

rox

ylo

pyra

no

se

2-h

yd

rox

y-3

-met

hyl

cycl

op

ente

n-2

-on

e

Lev

og

luco

seno

ne

1,4

;3,6

-dia

nhyd

ro-g

luco

pyra

nose

Patwardhan, P.; et al. J. Anal. Appl. Pyrolysis 2009, 86, 323

16

Effect of Chain Length

Glucose Cellobiose Maltohexaose Cellulose

LMW 57.42 42.16 41.01 21.42

Furans 19.08 17.44 13.85 5.63

Anhydrosugars 13.65 30.69 40.33 67.59

Levoglucosan 7.01 24.36 33.11 58.78

All numbers are wt%

LMW – Low molecular weight compounds

Patwardhan, P.; et al. J. Anal. Appl. Pyrolysis 2009, 86, 323

17

Cellulose

Depolymerized

fragment

Intermediate

Another

depolymerized

fragment

Levoglucosan

Ponder et. al., J Anal. Appl.Pyrolysis,, 1991

Fragment resulting from the

Glycosidic cleavage of dextran

Proposed Mechanism

Detailed mechanism

Department of Chemical and Biological Engineering

Quantum Chemistry Investigations

Levoglucosan

kmid-chain scission

kring closure

kend-chain scission

Ponder et al., J. Anal. Appl. Pyrolysis 1992, 22, 217-229.

O

OH

OHO

OH

O O

OH

OH

OH+

O-

O

OHOOH

OH

O

OHOH

O

OH

O

CH+

OHOH

O

OH

OH O

OH

OH

O

O

CH+OH

OHO

OHMayes and Broadbelt, submitted

Initiation

Depropagation

18

0

50

100

150

200

Gas ImplicitTHF

ImplicitWater

ΔH

in

kc

al/m

ol

at

77

3K

RadicalIonicConcerted

Concerted Mechanism ΔG in kcal/mol

773K, Implicit THF

53.2

-34.8

0.0

‡

+

Detailed mechanism

Department of Chemical and Biological Engineering

Quantum Chemistry Investigations Results

Mayes and Broadbelt, “Unraveling the Reactions that Unravel Cellulose,” submitted. 19

Reaction pathways included in cellulose fast pyrolysis

Detailed mechanism Pyrolysis mechanism

O

OH

OHOHOH

OH

CH

CH

CH

CH

CH

CH2 OH

O

OH

OH

OH

OH

CH O

CH

CH OH

CH2

OH

OH

CH2

OH

CH O

O

OH

OHOH

O

O H

C

C

C

H

H O H

H

O

C

C

H

H H

O C

C

C

H

H O H

H

O

C

C

H

H

O

OH O

O

OH

OHOH

OH

OH

OH OH

OHOH

OH

O

OH

OH

O

O

OHOH

OH

O

OHOH

OH

O

OHOH

OH

CH2

OH

CH O

OH

C

C

C

C

C

CH2OH

O

H

H OH

H

O H

H

OH

C

C

C

C

C

CH2OH

O

H

H

H

O H

CHOO

CH OH

CH OH

CH OH

CH OH

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Char, CO2, CO, H2O

O

OH

OOHOH

OH

O

OH

OHOHO

OH

O

OHOH

O

OH

O

OH

OOHO

OH

O

OHOOH

OH

O

OHOH

O

OH

O

OHOH

O

O

OHO

OHOOH

OH

OO

OHOH

O

O

OHOH

OH

O

OO

OHOH

O

O

OH

OHOHOH

OH

OHO

OHOOH

OH

O

OHOH

OH

O

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Glucose

Department of Chemical and Biological Engineering

Levoglucosan is formed by

concerted, glycosidic bond

cleavage reactions

in the mid and end of

cellulose chains

All other low molecular

weight products are formed

from glucose through various

reactions like dehydration,

ring opening, ring flipping,

retro aldol, retro Diels-Alder

and Grob fragmentation

20

Experimental data corresponds to Patwardhan et al., Biores. Technol. 2010, 101, 4646-4655

0

10

20

30

40

50

60

550 oC500

oC450

oC400

oC

Mass

yie

ld,

wt.

-%

350 oC

0

2

4

6

8

10

12

14

16

550 oC500

oC450

oC400

oC 350

oC

0.0

0.5

1.0

1.5

2.0

2.5

3.0

550 oC500

oC450

oC400

oC 350

oC

Levoglucosan 5-HMF 2-Furfural Formic acid

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

Expt.

Model

550 oC500

oC450

oC400

oC 350

oC

Effect of temperature on cellulose fast pyrolysis products

Model Predictions Model Predictions

Department of Chemical and Biological Engineering

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

0

20

40

60

80

100

Cellulose

Weig

ht

loss

/M

ass

yie

ld,

wt.

-%

Pyrolysis time, s

Levoglucosan

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

0

1

2

3

4

5

6

7

MW 102

Char

GlycolaldehydeHCOOH

H2O

CO2

2-Furfural

5-HMF

Mass

yie

ld,

wt.

-%

Pyrolysis time, s

Glucose

OH

OH OH

Time evolution of products of cellulose fast pyrolysis

T = 500 oC

P = 1 atm

Mn = 135,554 g/mol

PDI = 2.25

21

22

0

1

2

3

4

0 0.1 0.2 0.3 0.4

Wt

%

mmol of salt/g of cellulose

Acetol

0

10

20

0 0.1 0.2 0.3 0.4

Wt

%

mmol of salt/g of cellulose

Formic acid

0

20

40

60

0 0.1 0.2 0.3 0.4

wt

%

mmol of salt/g of cellulose

Levoglucosan

NaCl KCl

MgCl2 CaCl2

0

1

2

3

4

5

0 0.1 0.2 0.3 0.4

Wt

%

mmol of salt/g of cellulose

Furfural

Patwardhan, P.; et al. Bioresource Technol. 2010, 101, 4646

Alkali/Alkaline Earth Effects

23

0

200

400

600

800

1000

1200

1400

1600

1800

0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350 0.400 0.450

mo

l o

f g

luc

ose

/mo

l o

f m

eta

l io

n

mmol of salt/g of cellulose

NaCl

Ca(OH)2

KCl

“Turnover” Number

Effect of Alkali/Alkaline Earth

Patwardhan, P.; et al. Bioresource Technol. 2010, 101, 4646

24

Proposed Mechanism

Ca2+

Ca2+

25

Lignin Pyrolysis

Ace

tic

acid

Low mol. wt. compounds Phenolic compounds

Patwardhan, P.; et al. submitted 2011

26

Micropyrolysis of Lignin

Phen

ol M

ethox

y p

hen

ol

Eth

yl

phen

ol

Hydro

xy s

tyre

ne

Conif

eryl

alco

hol

Sin

apyl

alco

hol

GC-MS Analysis of Vapors from

Micropyrolysis of Lignin

GC-MS Analysis of Condensed Products from

Micropyrolysis of Lignin

Monomers

Oligomers

Patwardhan, P.; et al. submitted 2011

27

Lignin Monomers

coumaryl

alcohol

coniferyl

alcohol

sinapyl

alcohol

28

0

5

10

15

20

25

30

35

0 500 1000 1500 2000 2500

Are

a %

Mol. Wt. (Da)

CCS Mix

GPC of Lignin Monomers

0

5

10

15

20

25

30

35

0 500 1000 1500 2000 2500

Are

a %

Mol. Wt. (Da)

CCS Mix

CCS Mix Py

0

5

10

15

20

25

30

35

0 500 1000 1500 2000 2500

Are

a %

Mol. Wt. (Da)

CCS Mix

CCS Mix Py

CCSA Mix Py

Patwardhan, P.; et al. ChemSusChem 2012

29

“Passivating” Alkali in Biomass

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

20.00

Light Oxygenates Anhydrosugars Furans Phenols

wt%

of bio

mass (

wet

basis

)

Comparison of Different Switchgrass Pretreatments

Switchgrass Control

Acetic Acid

Formic Acid

Nitric Acid

Hydrochloric Acid

Phosphoric Acid

Sulfuric Acid

Kuzhiyil et al. (2012) submitted

30

Increases:

Nutrient Availability

Microbial Activity

Soil Organic Matter

Water Retention & Quality

Crop Yields

Decreases:

Fertilizer Needs

Greenhouse Gas Emissions

Nutrient Leaching

Soil Bulk Density

Terra Preta Oxisol

Biochar Application

31

Carbon Residence Time

100 m

Moderate Temperature High Temperature

Biochar “Average” Structure

Brewer, et al. Environ. Prog. Sustainable Energy 2009, 28, 386-396.

33

• Gasification

issue of scale

• Pyrolysis

issue of product quality

Key Challenges

34

Acknowledgements • Robert Brown

• Jim Katzer

• Pushkaraj Patwardhan

• Klaus Schmidt-Rohr

• Catherine Brewer

• Linda Broadbelt

– Vinu Ravikrishnan

– Heather Mayes

• ConocoPhillips

• U.S. Department of Energy

National Advanced Biofuels Consortium