Biodegradability of poly(lactic acid) (PLA)/lactic acid (LA) blends using anaerobic digester sludge

Poly(lactic acid) (PLA) has been highlighted for its excellent biodegradability and hydro-degradability. On the other hand, an estimation of the biodegradability of PLA generally requires lengthy measurements over several months because it is difficult for the terminal decomposer, a microorganism, to uptake and utilize the polymer material, making it difficult to analyze and compare the results quantitatively. In this study, it was hypothesized that the inclusion of mono lactic acid (LA) in a PLA blend improves the level of microbial attachment to the surface of the PLA blend, and increases the biodegradation rate. PLA blend films containing 1%, 2.5%, and 5% of LA were prepared, and their morphological changes to the surface and cross section of films were investigated. The biodegradation of a PLA/LA blend using digester sludge was estimated quantitatively from the specific gas production rate (SGPR) based on the surface area of the blend film. The physical and chemical properties before and after biodegradation were also compared. These results show that PLA/LA blends with a controlled degradation rate can be developed by incorporating readily degradable chemicals, and implemented as environmentally friendly plastics and polymers.