“Topics in Bioenergy, Bioprocessing, and

Biofuels” PSE 490/CFR 523

Spring 2008

Agenda

Bioenergy Rice Krispies Treats Biomass chemistry

Your co-instructor: Renata Bura

B.Sc.,1997, Ryerson University, Toronto, Canada, Chemistry

M.A.Sc., 2000, University of Toronto, Chemical Engineering and Applied Science and Environmental Engineering

Ph.D., 2004, University of British Columbia, Vancouver, Canada, Forestry

Post Doc., 2006, UBC, Vancouver, Canada

2006, joined UW-Assistant Professor in Natural Products Chemistry

Biofuels and biochemicals

BiomassBiofuels

Biochemicals

Biological

Thermochemical

What is Bioconversion?

General: a process which uses biological agents (microorganisms or protein) to transform a feedstock into desirable products.

Bioethanol A chemical/biochemical process by which

lignocellulosic materials are converted to ethanol and other co-products.

Why Bioconversion?

Energy» An alternative source of energy for the

transportation sector produced locally Air pollution

» Reduction in greenhouse gas emissions Waste elimination

» Elimination of problems with field burning/incineration, stockpiling, etc.

Socio/economical benefits» Creation of new jobs, rural development

Fundamentals of wood chemistry

Cellulose Hemicellulose Lignin

Bioethanol from sugar cane

Energy balance History Problems Production

Bioethanol from corn

Corn to ethanol» Energy balance» Problems» Production

– Dry milling– Wet milling

Bioethanol from lignocellulosic biomass

Feedstock diversity» Pretreatment » Hydrolysis» Fermentation

Biodiesel

Why biodiesel? How to make it?

» Possible sources Biodiesel and cars

How is Biomass like a Kellogs™ Rice Krispies Treat?

Your warped instructor needed some sort of an analogy to assist people in understanding biomass.

This is it.

Image borrowed from Kellogs™ web site for academic purposes

Rice Krispies Alone

At my home, a box of Rice Krispies consists of 2 things: Rice Krispies and Rice Krispies dust.

You can pour this mixture into a bowl but you cannot stand it up or make a bar.

Image borrowed from Kellogs™ web site for academic purposes

Formation of the Bar

You also need something to preserve the bars….A variety of preservatives can be used.

In order to make a solid bar, you need something to glue together the Rice Krispies and the Rice Krispies dust.

Marshmallow cooked over an open flame works great.

Rice Krispies Treats

Ingredient Amount Wood Equivalent

Big Rice Krispies 1 3/4 cups Cellulose

Rice Krispies Dust 1 cup Hemicelluloses

Marshmallow 1 1/8 cup Lignin

Butter 3 tablespoons Lignin

Preservatives ~ 1-5 tablespoons Extractives

The butter and the marshmallows are heated together forming a sticky glue type material.This is applied to the Rice Krispies and dust forming a bar which is solid when cooled.

What is Cellulose?

Cellulose is a large molecule made from glucose molecules (dextrose) strung together like beads on a string.

The glucose molecules are known as monomers and the cellulose chain is known as a polymer. » 1 glucose molecule= monomer » 2 linked glucose molecules= dimer» 3 linked glucose molecules= trimer» lots of linked glucose molecules = polymer

What is Cellulose?

Cellulose is straight chain polymer. In bead terms, imagine a very very long straight string of beads with 2 ends and no branching points.

In wood, cellulose chains contain typically 10,000 glucose molecules…quite a long sting of beads.

Source: World Book Encycopedia

Cellulose Very long straight chain polymer of glucose (a sugar): approximately 10,000 in a row in

wood. Cotton is nearly pure cellulose.» Think about a very long string of beads with each bead being a glucose molecule.

Cellulose molecules link up in bundles and bundles of bundles and bundles of bundles of bundles to make fibers.

Uncolored polymer.

O

O O

O

O

O

O

O

CH2OH

OHHO

OHHO

CH2OHOH

CH2OH

HO

OH

CH2OH

HO

O

Cellulose

Cellobiose Unit

What are Hemicelluloses?

Hemicelluloses are also sugar polymers but different from cellulose because they are:» Made up glucose and other sugars.» Contain some molecules other than sugars.» Branched little polymers

– Much smaller than cellulose as they are made up of between 50-300 sugars (Rice Krispies Dust)

There are lots of varieties of hemicelluloses.

Hemicelluloses

Branched little uncolored sugar polymers (~ 50 to 300 sugar units)» Composition varies between wood species.

– 5 carbon sugars: xylose, arabinose.– 6 carbon sugars: mannose, galactose, glucose.– Uronic Acids: galacturonic acid, glucuronic acid.– Acetyl and methoxyl groups (acetic acid &

methanol). Major hemicelluloses:

» Xylans - big in hardwoods» Glucomannans: big in softwoods

Minor hemicelluloses: pectins, others.

Xylan Structure

4--D-Xly-14--D-Xly-14--D-Xly-14--D-Xly4--D-Xly

4-O-Me--D-Glc

-L-Araf

O O

O

O

O

O

OH

OHHO

HO

HO OH

OO

O

HO OH

O

O

CO2HH3CO

OHHOH2C

O

O

OH

Glucomannan Structure

4--D-Glc-14--D-Man-14--D-Man-14--D-Man-1

2,3

Acetyl

6

-D-Gal1

There are different structured glucomannans in hardwoods and softwoods (and within softwoods)

Glucomannans are mostly straight chained polymers with a slight amount of branching. The higher the branching, the higher the water solubility.

What is Lignin?

Lignin is a polymer like cellulose and hemicelluloses but is made with phenolic compounds (aromatic rings) instead of sugars.

Lignins are large 3 dimensional polymers that form the glue that holds the cellulose and hemicelluloses together.

Lignin has been described as 3 dimensional chicken wire.

Picture taken from Katy’s chicken page.

Lignin

Phenolic polymer - the glue that holds the fibers together.

Lignin is a very complex polymer which is connected through a variety of different types of linkages.

Colored material.CH2 O

OH

OCH3

COHH

HC

CH2OH

OH CH2OHC

O

H3CO

C O

CH

CH

H

CH

CHOH2

HO

H

CH

OCH3

OH

C

OH2C

CHO

O

C

CH2OHH3C

O

O

COH

O CH

H3C

CH2OH

H

HCOH

1

2

3

4

5

6

7

H

HC CH

O

O CH

CH2O

C

OCH3

O

CHO

H2C

H3C

8

OHC CH CH2OH

CH2OH

O

O

C

OH

H3C9

10

O

HC CH

COHH2

CH2O

CH

O

OH

H3C

11

H3C

12

HO

CH2OHH3C

13

O

C

O

CH

O CH

O

H3C

H

CH3

CH

OH

O

CH

H3C

CH

H2COH

15

16

Carbohydrate

CH2OH

OH

OCH3

HC 14

H2COH

HC

CHO

17

HOCHO

O

C O CH2

H3C18

HCHO

O

H

H3C

19

O

CH

OCH

O

CH

O

COHH2

OH

OCH3

COHHCOHH2

20

H

CH

H2COH

OCH3

O

HC O

C

OCH3

CH

CH

CHO

22

21

O

H2COHCH2

CH2

H

C O

C

OCH3

24

25

26CH

28

27

O

CH2OH

H

CH3

CH

O

O

H2COH

H

H2COH

H3C

H3C

H2COH

O

CH

CH

OHC

O

O

O

H

23

COH

OCH3

What are Extractives?

In the Rice Krispies model, extractives compounds were represented by preservatives added to the treats. This is a very good representation of the role of a good portion of the extractives in trees.

The term extractives refers to a large variety of different chemicals produced by the tree for a variety of reasons (protection, food storage, formation of membranes, color, etc.).

Examples: what sticks to your hand when you pick up your Christmas tree, what comes out of your tea bag with hot water.

Extractives

The term extractives refers to a group of unique chemical compounds which can be removed from plant materials through extraction with various solvents.

Typically these chemicals constitute only a small portion of the tree (<5%).» In some tropical species this can be as high as

25%. Extractives are produced by plants for a variety of uses.

» The most common use by plants is protection. Extractives can cause serious problems for processing. Pitch is a term which is often used when describing some

groups of extractives. Extractives are responsible for the characteristic color and

odor of wood.

Putting it All Together

Putting all of the components together and you get biomass. The cellulose and the hemicelluloses held together with lignin.

Taking the lignin away through chemical processes (pulping and bleaching) leaves these fibers of cellulose and hemicelluloses.

Picture from Focus Forest Products Web Site

What is the Chemical Makeup of Wood?

0

10

20

30

40

50

60

%

Douglas Fir Redwood Yellow Pine Balsam Fir

Cellulose*Hemicellulose*Lignin*Extractives

* Data for Cellulose, Hemicellulose & Lignin on extractive free wood basis