Polylactic acid pellets production from corn and sugarcane molasses: process simulation for scaled-up processing and comparative life cycle analysis

Abstract

Polylactic acid (PLA) is a biodegradable alternative that could mitigate harmful impacts from disposal of single-use polyethylene to the environment. This study compares the scaled-up PLA pellets production using two feedstock options, i.e., corn and sugarcane molasses. The process simulation technique is integrated to scale-up the PLA processing stages of the two feedstocks and retrieve life cycle inventory data for life cycle analysis. A cradle-to-gate life cycle system boundary from the cultivation stage to lactide polymerization stage of the two feedstock routes are modelled, separately, and the process simulation results are validated by comparing with the actual plant data, reported in the published literature. The life cycle net energy analysis indicators and climate change impact are evaluated for the developed life cycle scope. The results indicate that sugarcane molasses consumes around 80% of the total life cycle net energy inputs for PLA pellets production, compared to that of corn. Accordingly, PLA pellets processing from Sri Lankan sugarcane molasses shows a net energy gain with a net energy ratio of 1.09 and a renewability indicator of 5.63. Despite, PLA pellets processing from imported corn corresponds to a net energy loss with an extremely low renewability. In addition, sugarcane molasses is responsible for around one-quarter of the climate change impact (1,470 kg CO2 eq/tonne of PLA), compared to that of corn as a feedstock for PLA pellets production. The variations in environmentally benign aspects of sugarcane molasses as a feedstock for PLA pellets production are discussed along with a sensitivity analysis.