Breaking It Down: How Thermoplastic Starch Enhances Poly(lactic acid) Biodegradation in Compost─A Comparative Analysis of Reactive Blends

Abstract

Poly(lactic acid) (PLA) is a sustainable, bio-based, and industrially compostable polymer with a recalcitrant abiotic degradation phase, limiting its organic recovery to well-managed industrial composting facilities. We present a methodology to fully biodegrade PLA in industrial and home composting settings. Thermoplastic starch (TPS) and PLA were reactively blended by adding a chemical modifier and peroxide radicals to obtain a PLA-g-TPS blend by twin screw extrusion and later processed into films by cast extrusion. Biodegradation of the films was investigated using a direct measurement respirometer for 180 days by tracking the CO 2 evolution in compost media at 58 and 37 °C, and the number average molecular weight (M n ) reduction was measured by size exclusion chromatography. The hydrophilic nature of TPS and its role as a nutrient source accelerated the degradation of PLA in both abiotic and biotic phases of the composting process. The kinetic curve of M n reduction showed the positive effect of TPS on accelerating PLA hydrolysis during the lag phase in both mesophilic and thermophilic conditions due to increased chain mobility. This work unlocks the capability of PLA-based films to be successfully composted in industrial and home composting without compromising their desired properties for applications in everyday life.

Speeding it up: dual effects of biostimulants and iron on the biodegradation of poly(lactic acid) at mesophilic conditions

“…These values are very low compared to the degradation of PLA at thermophilic temperatures 4,44 but are similar to earlier reported values. 5,46…”

“…4 However, at the lower temperatures commonly encountered in the home or backyard composting environments (herein referred to as backyard composting), chemical hydrolysis proceeds at a prolonged pace. 5 Boosting the hydrolytic degradation of PLA, particularly in backyard composting, is extremely difficult due to the limitation of high temperature essential to activate the biodegradation process. 3…”

Novel methods to monitor the biodegradation of polylactic acid (PLA) by Amycolatopsis orientalis and Amycolatopsis thailandensis

“…However, most conventional plastics are fossil-based, causing environmental pollution and waste management problems. The durability of plastics hampers their degradation in the biosphere, resulting in the long-term retention of plastic waste in the environment ( Shimao, 2001 ; Mayekar et al, 2023 ). Chemical recycling is at its forefront as an economically viable technology for plastic waste management (JRC Technical Report, 2023).…”

Incorporating organoclays into sustainable starch/polylactide biocomposites for enhanced mechanical and thermal properties

“…In addition, organoclay can improve composites' gas barrier properties, flame retardancy, and biodegradability. 36 Several studies have examined the effects of various parameters such as organoclay loading, clay surface modification, processing conditions, and compatibilizers on the properties of organic TPS/PLA/clay composites or other additives. We refer readers to the prior art for more information from recent reviews and articles.…”

“…Secondly, organoclay acts as a nucleating agent that promotes crystallization and improves various matrices' thermal stability, including PLA. In addition, organoclay can improve composites' gas barrier properties, flame retardancy, and biodegradability 36 . Several studies have examined the effects of various parameters such as organoclay loading, clay surface modification, processing conditions, and compatibilizers on the properties of organic TPS/PLA/clay composites or other additives.…”