Continuous Polylactic Acid Production Utilizing Dextrose from Corn

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Continuous Production of Polylactic Acid Utilizing Dextrose from CornElizabeth Bol Landon Carlberg Senja Lopac David Roland May 7, 2004


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


Breakdown of Waste


ScopePlant 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 AcidInsoluble 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)


UsesSingle-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 MarketPlastics 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 StepTwo molecules of lactic acid combine to form one molecule of lactide


Chemistry of Polymerization StepThe lactide polymerizes through ring opening polymerization to a molecular weight of approximately 30,000


Block Flow Diagram


Key Design AssumptionsIndustrial scale equipment behaves similarly to laboratory testing equipment Equipment from differing experiments is compatible


Fermentation Step


Polymerization Step


Key Design Decisions - FermentationTwo-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 - NeutralizationCalcium 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 CatalystTin 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


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


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


Economic SummaryFCI = $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

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Last Updated: 8th March 2018

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