Abstract

Poly(lactic acid) (PLA) offers the value proposition of removing 1.83 kg of CO2 from the environment and embodying it into the PLA polymer in complete synch with the natural biological carbon cycle. In the case of plastics made from fossil resources the carbon present has formed over a million year time frame and so cannot be credited with any CO2 removal from the environment even over a 100 year time scale ( the time period used in measuring global warming potential, GWP100). However, this “beginning of life” sustainable value proposition needs to be reinforced with environmentally responsible end-of-life. Single use, short life plastics used in conjunction with food packaging and disposable articles lend themselves to biodegradability as its end-of-life strategy. PLA plastics offers complete biodegradability (complete utilization of the PLA carbon by the compost microorganisms) in industrial composting operations. Durable and engineering PLA plastics do not lend itself to biodegradability but to recycling as its end-of-life option. A viable approach is chemical recycling back to monomer – a virtual cycle of monomer to polymer and back to monomer – a circular biobased economy. This lecture presents the PLA story from laboratory to current commercial operations. NatureWorks LLC (a Cargill subsidiary) manufactures 140,000 tons (300 million pounds) of PLA under the trade name IngeoTM. Traditionally, PLA has been produced in a batch process as a specialty biomedical product in small quantities at high prices around $1000/kg. However to make PLA competitive as a commodity resin competing with PET and polyolefin thermoplastics, engineering and process scale-up studies were needed. We present the chemistry, and process overview from feedstock to sugar to lactic acid to lactide monomer to polymer resin – a complete process that provides for integration and economies of scale to manufacture PLA resin at competitive pricing to current petro based thermoplastic resins. End-of-life options for PLA products, specifically compostability and recycling will be reviewed.