Biomass Basics:Renewable Energy and Chemicals

Dennis J. MillerDepartment of Chemical Engineering and Materials

ScienceMichigan State University

East Lansing, Michigan 48824(517) 353-3928

millerd@egr.msu.edu

Benefits of the Chemical IndustryTell Our Students About It!!

The Emerging Paradigm: Sustainability and Green Chemistry

"Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.”

The Brundtland Commission Report, The United Nations, 1987.

• Environmentally Sustainable

• Economically Sustainable

• Socially Sustainable

Petroleum

www.bp.com

Distribution of proven (oil) reserves

1984,1994, 2004

Oil reserves-to-production (R/P) ratios

Oil consumption by region

Major oil trade movements

Energy Consumption Concepts(A great web site: www.bp.com)

• Material and Energy Balances– How much fossil energy in MJ (oil, coal, gas)

does the world use annually?– How much oil does the U.S. use annually?

(A: about 1.5 cubic miles)– How many watts per person does that equate

to in the U.S.?

Biorenewable Fuels and Chemicals

Corn: The Near-term Biofuels Feedstock

2005 Statistics• Production: 11.8 billion Bushels• Acres planted: 80.9 million acres• Average yield: 160 bushels/acre

(vs. 137 bu/a in 2000!)

The corn plant 3.8 tons corn stover / acre (lignocellulosic)• 3.8 tons corn grain / acre

Societal/Global perspective questions: How much of our fuel needs can corn provide?What are the costs associated with using corn for fuel?How does politics enter into corn ethanol?

Corn to ethanol energetics

C6H12O6 = 2 C2H5OH + 2 CO2

glucose ethanol carbon dioxide 1.0 kg 0.51 kg 0.49 kg 17 MJ 15.8 MJ 0 MJ

Theoretical yield 2.7 gal/bu EtOH yield (grain only): 450 gal/acreEtOH yield w/ 50% stover: 670 gal/acre

• Ethanol energy content 80,000 Btu/gal• Gasoline energy content 130,000 Btu/gal

Ethanol fuel supply

• U.S. gasoline consumption (2006): 150 billion gal

• U.S. fuel ethanol consumption (2006): 6 billion gal – 4% of total gasoline demand – Blended 10% with gasoline (40% of U.S. gasoline contains ethanol)– 14 million of 80 million acres of corn harvested

Ethanol energy exercises

• How much corn would be required to provide E10 for the entire U.S.?A: About ~5 billion bushels (40% of 2006 U.S. crop)

• What land mass would be required to replace all U.S. gasoline with ethanol?A: 200 billion gal EtOH equates to 75 billion bushels corn / yr or300+ million acres (22% of U.S. landmass)!

Cellulosic Biomass – long-term renewable biofuel feedstock

Composition (wt%) Wood SwitchgrassCellulose 55 55Hemicellulose 20 30Lignin 25 15

Yield (ton/acre) 3 - 8 3 - 10Ethanol yield (gal/ton) 90 - 100 90 - 100

Challenges – Switchgrass is low-density compared to corn, more costly to

collect and transport.– Cellulose difficult to hydrolyze (structural polymer); starch is

amorphous and easy to hydrolyze.– Can burn lignin to provide energy for plant operation

Senior Design Problem: Bioenergy plantation design

• Fundamental concept: there exists an optimum biorefinery capacity (M) for biofuel production. (Tradeoff between capital cost (~M0.6) and cost of transporting biomass (~M1.5)).

• Process energy provided by lignin combustion• Can choose parameters arbitrarily or use

standard values (NREL website). • Possibilities for open-ended design, multiple

smaller “feeder” process units in remote locations.

Biomass Plantation Economics (NREL)

Biodiesel from plant oils

R''

O

OO

O

R

O

R'

O R

O

O

acid methyl ester(biodiesel)

OH

methanol

+

Plant oil(triglyceride)

OH

HO

OH

glycerol

3 + 3OH- or H+

• Plant oils include soy, rapeseed, canola, etc.. • Waste cooking oils are minor potential source, are inexpensive, but contain water and free fatty acids that must be cleaned up.•Other sources include algae, sewage, etc.. • Reversible reaction system •Typical methanol:oil feed ratio of 6:1 gives two product phases, >98% methyl ester yield

Current biodiesel production(Batch production, labor and energy intensive)

Plant oil (100 kg) (30 gal)

Methanol (22 kg)(6:1 ratio)

NaOCH3 (0.5 kg)

60oC, 2 hr

purification

Glycerol+

NaOCH3

Biodiesel Product(100 kg)(30 gal)

Neutralizepurify Glycerol

byproduct(10.4 kg)

(0.7 lb/gallon)

Biodiesel in the classroomMaterial and energy balances:

a) Calculate stoichiometric reaction masses, byproduct glycerine yieldsb) Calculate biodiesel energy density relative to diesel fuelc) Optimizing energy yields from land - Which fuel type gives higher energy yield per acre, biodiesel or ethanol? Canola: 1000 kg/acre*0.44 kg oil/kg canola*39 mJ/kg = 17160 MJ/acreEthanol: 160 bu/acre*2.7 gal/bu*3 kg/bu*27 MJ/kg = 35000 MJ/acre

Reaction engineering:Make biodiesel as classroom demo (cooking oil + methanol + sodium hydroxide/methoxide)Good example of homogeneous catalysis (can see color change upon addition of sodium hydroxide in methanol)

Chemical Building Blocks from Biomass

Carbon number Biomass Blocks Petroleum Blocks

C1 methanol, CO methane

C2 acetic acid, ethanol ethylene

C3 lactic acid, acetone, propylene propionic acid, glycerol

C4 succinic acid, n-butanol isobutylene

3-hydroxybutyrate butadiene

C5 xylose, glutamic acid

3-hydroxyvalerate

C6 glucose, lysine benzene

C7, C8 toluene

xylene

Chemicals from CarbohydratesChemicals from Carbohydrates

CORNSTARCH

CELLULOSEIndustrial starches,cellulose derivatives

GLUCOSE

Fermentation Chemical conversion

Organic acids Ethanol Others Gluconic acid SorbitolPolymers

H2O2

Lactic acidSuccinic acidCitric acidAcetic acidPropionic acidItaconic acidLysineD,L-MethionineOther amino acidsAromatics

1,3-propanediol2,3-butanediolABE

Starch copolymersXanthan gumAlginatesHydroxyalkanoate

PG, EGGlycerolSorbitanAscorbic acid

Syrups, sweeteners

BIOMASS(CORN, WOOD..)

Lactic AcidLactic Acid

Fermentation: C6H12O6 2 C3H6O3

(glucose) (lactic acid)

- Yields exceed 0.95 lb/lb glucose - Product concentrations > 90 g/L - Production rates > 3 g / L· hr - Ca(OH)2 to neutralize, acidulation w/ H2SO4 (CaSO4 waste) Production cost: < $0.25 / lb

Production capacity: 350 MM lb/yr (Cargill)100 MM lb/yr (all others)

CH CO

OH

OH

CH3

Equilibrium Lactate Ester ReactionsL1

L2

L3

L4

L4E

L1EL2E

L3E

W

W

W

W

W

W

W

Et

Et

EtEt

Et

Et

Et

Et

Et

L1

L1

L1

OH

O

O

OH

O

OH

O

O

OC2H5

O

L2

L2E

Nominal lactic acid concentration (wt%)

L1 L2 L3 L4

20 20 - - -

50 42 8 - -

88 58 22 6 2

Equilibrium oligomer distribution

- Lactic acid oligomerization reactions characterized by Ke = 0.23

Lactate esters via reactive distillation

Lactic Acid + Ethanol = Ethyl lactate + Water

Lactic Acid

Ethanol

Water

Ethyl Lactate

Ethanol + Water

Ethyl Lactate (+ oligomers)

Wt %

EtOH 82.93EtLA 0.13Water 16.94

Stream 3Flow 65.98 kmol/hr

Wt %

LA 0.00 EtOH 0.30EtLA 72.64Water 0.13 L2ES 19.44 L3ES 6.11L2 Acid 0.66 L3Acid 0.63

Stream 4Flow 9.90 kmol/hr

Wt %

EtOH 100.0

Feed Stream 2Flow 54.0 kmol/hr 85C 1.16 atm

Wt %

LA 58.0Water 14.0L2 Acid 22.0L3 Acid 8.0

Feed Stream 1Flow 21.87 kmol/hr 25C

10

30

35

Reactive distillation for lactate ester production

7FEED (88% LA feed)

LA : 9.519 kmol/hrL2 Acid : 2.005 kmol/hrL3 Acid : 0.505 kmol/hrWater : 9.847 kmol/hrEtOH : 54.000 kmol/hr

# Stages 35Reflux ratio 0.1

Lactic acid conversion (%) >99

Chemicals from Renewables

• Material balances/reaction engineering: Determine theoretical yields - renewables generally undergo weight loss in conversion, whereas petroleum generally undergoes weight gain in conversion.

• Separations: schemes for purifying low volatility organic/renewable products (evaporation, reactive distillation, chromatography, other novel separations)

• Thermodynamics: Many biobased reactions are reversible, involve nonideal solutions, physical properties estimation required

Summary

• Renewable fuels and chemicals can be incorporated across the core ChE curriculum– Energy and mass balance calculations – Thermodynamics: physical properties, phase

equilibria, reaction equilibria– Reaction engineering: kinetics, reactor design,

catalysis– Separations: design separations schemes for non-

volatile, thermally fragile compounds– Process design: core chemical engineering principles

and unit operations are key to designing biorefineries

GREEN CHEMISTRY DEFINITION

Green Chemistry is the utilisation of a set of principles that reduces or eliminates the use or generation of hazardous substances in the design, manufacture and application of chemical products *.

GREEN CHEMISTRY IS ABOUT (12 principles)• Waste Minimisation at Source• Use of Catalysts in place of Reagents• Using Non-Toxic Reagents• Use of Renewable Resources• Improved Atom Efficiency

• Use of Solvent Free or Recyclable Environmentally Benign Solvent systems

Traditional Synthesis of Ibuprofen

(CH3CO)2O

AlCl3

O

I¯Bu

ClCH2CO2C 2H5

NaOC2H5

O CHCO2C2H5

I¯Bu

H+

H20

CHO

I¯Bu

H2NOH

I¯Bu

C N

CH NOH

I¯Bu

CO2H

Ibuprofen

(BASF and Celanese Corporation)

60% Waste

Green Chemistry Alternative Synthesis of Ibuprofen PGCC Winner 1997

(CH3CO)2O

HF catalyst

H2

CO, PdCO2H

O

OH

Ibuprofen

(BASF and Celanese Corporation)

1% Waste

+ CH3COOH

Green chemistry in the curriculum

• Material and Energy Balances– Define and implement atom economy and waste

generation into stoichiometry problems– Yield calculations for multiple step syntheses

• Reaction Engineering and Design courses– Carry out reactor design for green process and

compare with traditional process• Resource: ACS Green Chemistry Institute