Recycling and Waste Management

Statement of the Problem: Biodegradable polymers are potential solutions to the environmental problems generated by plastic waste. Every year, 8 million tons of new plastics are dumped into oceans. With growing market volumes of innovative bio-based and biodegradable plastics such as Poly(Lactic Acid (PLA), the recycling of these materials is becoming a more viable option. PLA has attracted particular attention as a substitute for conventional petroleum-based plastics. To increase sustainability and management of plastic waste, new methods to close the recycling loop of PLA are needed. Recycling approaches have limitations in that materials can only undergo a fi nite number of processing cycles before their properties are deteriorated. Production of PLA from recycled components allows substantial energy savings compared to using virgin raw materials.

Methodology: PLA depolymerization by hydrolysis leads to production of high quality LA which can be used to reproduce PLA polymers. This avoids the expensive and complex process of glucose fermentation, which is used to obtain virgin Lactic Acid (LA). In this work, combined chemical and biochemical methods for PLA depolymerization to high value and quality components are developed. Th e hydrolyzed PLA products were characterized by: (1) GC/MS: Evaluation of monomeric and oligomeric content; (2) Chiral GC: Evaluation of D and L-LA enantiomers content; and (3) SEC: Calculation of molecular weight and molecular weights distribution.

Findings: Th e PLA hydrolysis proceeds with higher rates in alkaline conditions with formation of LA monomer without changes in the original composition of D, L isomers. Acidic hydrolysis of PLA produces a mixture of monomeric and oligomeric forms and their composition depends on the reaction conditions.

Conclusion: By alkaline hydrolysis of PLA, LA monomer can be produced and repolymerized aft er conversion in acid form. By hydrolysis of PLA in acidic conditions, oligomeric precursors suitable for further biochemical/enzymatic depolymerization can be produced