Environmental footprint of polylactic acid production utilizing cane-sugar and microalgal biomass: An LCA case study

Abstract

Polylactic acid (PLA), a bioplastic widely used in sustainable packaging, offers notable environmental advantages over petro-plastics. However, the environmental footprint of PLA production depends heavily on biomass feedstock. This study provides a comparative life cycle assessment (LCA) of PLA production from cane-sugar and microalgal biomass, analyzing contributions across production stages and performing sensitivity analysis to identify key environmental factors. The study also highlights the recommendations for optimizing processes to reduce environmental burdens. Conducted per ISO 14044:2006 standards, the analysis revealed distinct trade-offs between the feedstocks. Cane-sugar based PLA demonstrated lower global warming potential (GWP) (406 kg CO2 eq/tonne PLA) and energy consumption due to established agricultural practices but required higher land (959 m2 × a crop eq/tonne PLA) and water demand (183 m3 eq/tonne PLA). Conversely, microalgae-based production significantly reduced land use (75 m2 × a crop eq/tonne PLA) due to utilizing non-arable lands but incurred elevated impacts such as freshwater eutrophication (11.93 kg P eq/tonne PLA) due to high energy and nutrient demands. Sensitivity analysis identified fermentable sugar content in microalgae as critical for reducing GWP, emphasizing the importance of strain selection and optimized cultivation. High sensitivity ratios and sensitivity coefficients for energy inputs across both feedstocks highlighted their significant impact on environmental performance. While cane-sugar based PLA currently offers lower impacts, microalgae is a promising alternative for regions with limited arable land, contingent on improvements in energy efficiency and nutrient recycling. These findings contribute to the broader effort of optimizing PLA production systems for enhanced sustainability and reduced environmental footprints.