Continuous Production of Polylactic Acid Utilizing

Dextrose from Corn

Elizabeth BolLandon Carlberg

Senja LopacDavid Roland

May 7, 2004

Overview

Scope Market Analysis Basic Chemistry Key Design Assumptions Process Specifications Key Design Decisions Safety and Environmental Concerns Economic Evaluation Recommendations

Breakdown of Waste

Paper36%

Yard Trimmings

12%Food Scraps

11%

Plastics11%

Metals8%

Rubber, Leather, and

Textiles7%

Glass6%

Wood6%

Other3%

Products Time to biodegrade

Cotton rags 1 to 5 months

Polylactic acid, composted 45 to 60 days

Paper 2 to 5 months

Orange peels 6 months

Cigarette butts 1 to 12 years

Plastic coated paper milk cartons

5 years

Plastic bags 10 to 20 years

Leather shoes 25 to 40 years

Nylon fabric 30 to 40 years

Tin cans 50 to 100 years

Aluminum cans 80 to 100 years

Plastic 6-pack holder rings 450 years

Glass bottles 1 million years

Plastic bottles Forever

Scope

Plant built in Midwest Two key assumptions

Built next to corn milling facility Dextrose production can be

increased with increased demand of PLA

Total capacity of 500 million pounds per year Cargill and Dow Chemical co-

venture resulted in a 300 million pound polymer plant, with second plant in planning

Properties of Polylactic Acid

Insoluble in water, moisture and grease resistant Biodegradable and compostable Clarity and glossiness similar to its other plastic

competitors Requires 20 to 50% less fossil fuels to produce

than regular plastics Comparable physical properties to polyethylene

terephthalate (PET)

Uses

Single-use items such as plates, utensils, cups, and film wrap

Plastic bottling and fast-food companies Paper coatings Clothing fibers Compost bags Biomedical field

Current Market

Plastics 2000: 150 million tons 2010: Expected to reach 258 million tons

Biodegradable Plastics 1997: 20 million pounds 2004: Expected to capture 20% of the market for

plastics (approximately 50 million tons) Current selling price of PLA: $1.50/lb Current selling price of PET: $0.60/lb

Chemistry of Fermentation Step

26126 OHC

•Bacteria breaks down one molecule of dextrose to form two molecules of lactic acid

Chemistry of Lactide Formation Step

2

•Two molecules of lactic acid combine to form one molecule of lactide

Chemistry of Polymerization Step

•The lactide polymerizes through ring opening polymerization to a molecular weight of approximately

30,000

Block Flow Diagram

Key Design Assumptions

Industrial scale equipment behaves similarly to laboratory testing equipment

Equipment from differing experiments is compatible

Fermentation Step

Polymerization Step

Key Design Decisions - Fermentation

Two-stage membrane cell recycle bioreactor with ammonia resistant strain of Lactobacillus rhamnosus High productivity More feasible for scale-up

Electrokinetic bioreactor Relieves product inhibition Alleviates need for additional pH control chemical

Key Design Decisions - Neutralization

Calcium carbonate/Sodium hydroxide Ammonia

Easy to recycleNo salt formationDoes not damage cells

ElectrodialysisDoes not introduce additional chemical for

separation

Key Design Decisions – Polymerization Catalyst

Tin OctanoateCatalyst used by Cargill DowLess expensiveHarmful to humans and the environment

Zinc β diiminate complex catalystGives 94% conversion in 30 minutes Immobilized in a packed bed

Safety

Flammables, corrosives, and explosion hazardsCareful chemical storage placementsStrict personal protective equipment policies

Implementation of process control Execution of extensive safety procedures

Environmental Concerns

Produces n-butanol waste stream which needs to be treatedFurther research is necessary

All process solvents and catalysts require secondary containment and careful monitoring

Key Economic Assumptions

Interest Rate, 12% Working capital is 15% of fixed capital Addition to existing corn milling facility Project life of 15 years 8000 hours of operation per year 40% tax rate and MACRS depreciation (5 year

accelerated) Nearly 100% regeneration of catalysts PLA demand will meet facility output by start-up

Equipment Costs(in millions of dollars)

Total Grass Roots, for Equipment: $265 million

Vessels $77.300

Pumps $1.340

Towers $2.470

Tanks $1.510

Reactors $97.300

Exchangers $80.830

Compressors $3.860

Manufacturing Costs (in millions of dollars)

CRM$32.04

COL$0.80

CUT$125.88

CWT$0.39

Cost of Manufacturing, without Depreciation: $159 million

Utility Costs(In millions of dollars)

By Equipment

Exchangers $68.22

Pumps $0.23

Reactors $38.03

Vessels $19.40

By Type

Low-Pressure

Steam $82.88

Refrigeration $27.60

Cooling Water

$13.95

High-Pressure

Steam $1.22

Electricity $0.23

Total utility costs: $126 million

Effect of percent change in price of material to ROI

140.00%

141.00%

142.00%

143.00%

144.00%

145.00%

146.00%

147.00%

Percentage change in price

R O

I

DextroseAmmonia1-ButanolSulfuric AcidTolueneMethanolTin Octanoate CatalystZinc Diiminate CatalystWaste w ater

Discounted Cash Flow Diagram

ROI @ $.60/lb: 26.34% ROI @ $1.50/lb: 144.42%

(600.00)

(300.00)

0.00

300.00

600.00

900.00

1200.00

1500.00

1800.00

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Project Life (Years)

Pro

ject

Val

ue

(mill

ion

s o

f d

olla

rs)

$1.50/lb

$.60/lb

Economic Summary

FCI = $265 million DCFROR

At PLA selling price = 101.4%At PET selling price = 28.1%

Payback PeriodAt PLA selling price = 0.8 yearsAt PET selling price = 3.4 years

Recommendations

Further research on alternative catalysts for both the lactide formation and the polymerization steps

Sizing and cost estimates of extruders Continued research on properties of lactide, and

polylactic acid Research alternative methods for

recycle/removal of n-butanol from waste stream Heat integration study Improve water recycle rate

Acknowledgements

Dr. Ryan O’Connor, Cargill Dow LLC Rafael Auras, Michigan State University Dr. Christopher Jones, and Kunquan Yu,

Georgia Institute of Technology

Question Session