Continuous Production of Polylactic Acid Utilizing Dextrose from Corn Elizabeth Bol Landon Carlberg Senja Lopac David 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 ProductsTime to biodegrade Cotton rags1 to 5 months Polylactic acid, composted45 to 60 days Paper2 to 5 months Orange peels6 months Cigarette butts1 to 12 years Plastic coated paper milk cartons5 years Plastic bags10 to 20 years Leather shoes25 to 40 years Nylon fabric30 to 40 years Tin cans50 to 100 years Aluminum cans80 to 100 years Plastic 6-pack holder rings450 years Glass bottles1 million years Plastic bottlesForever

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

Chemistry of Lactide Formation Step 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 recycle  No salt formation  Does not damage cells Electrodialysis  Does not introduce additional chemical for separation

Key Design Decisions – Polymerization Catalyst Tin Octanoate  Catalyst used by Cargill Dow  Less expensive  Harmful to humans and the environment Zinc β diiminate complex catalyst  Gives 94% conversion in 30 minutes  Immobilized in a packed bed

Safety Flammables, corrosives, and explosion hazards  Careful chemical storage placements  Strict personal protective equipment policies Implementation of process control Execution of extensive safety procedures

Environmental Concerns Produces n-butanol waste stream which needs to be treated  Further 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)

Manufacturing Costs (in millions of dollars) Cost of Manufacturing, without Depreciation: $159 million

Utility Costs (In millions of dollars) Total utility costs: $126 million

Effect of percent change in price of material to ROI

Discounted Cash Flow Diagram $.60/lb: 26.34% $1.50/lb: %

Economic Summary FCI = $265 million DCFROR  At PLA selling price = 101.4%  At PET selling price = 28.1% Payback Period  At PLA selling price = 0.8 years  At 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