Life cycle assessment of the manufacture of lactide and PLA biopolymers from sugarcane in Thailand

l-lactide is the monomer for the polymer poly-l-lactic acid (PLLA). PLLA can be made from renewable resources, and is used in an increasing amount of applications. The biopolymer PLLA is one type of polymer of the family of polylactic acids (PLAs). Purac produces l-lactide and d-lactide, and supports partners with know-how to produce their own PLA from lactide. This life cycle assessment (LCA) study supporting market development presents the eco-profile of lactides and PLA biopolymers. An LCA was carried out for l-lactide, d-lactide, PLLA, and two PLLA/PDLA blends made from cane sugar in Thailand, and were compared with that of fossil-based polymers. The LCA complies with ISO standards, and is a cradle-to-gate analysis including sugarcane cultivation, sugarcane milling, auxiliary chemicals production, transport, and production of lactide and PLAs. In the analysis, process data were taken from the designs of full-scale plants for the production of lactic acid, lactides, and PLA. The data were combined with ecoprofiles of chemicals and utilities and recalculated to the following environmental impacts: primary renewable and non-renewable energy, non-renewable abiotic resource usage, farm land use, global warming, acidification, photochemical ozone creation, human toxicity, and eutrophication. On a weight-by-weight basis, PLLA results in significantly lower emissions of greenhouse gasses, and less use of material resources and non-renewable energy, compared to fossil-based polymers. With the present calculations, the Global Warming Potential (GWP) in l-lactide production is 300-600 kg CO2 eq./tonne and for PLLA 500-800 kg CO2 eq./tonne. The range indicates the sensitivity of the GWP to the energy credit for electricity production from bagasse in the sugar mill. The GWP of PLLA/PDLA blends with increased heat resistance is also lower compared to fossil based polymers with similar durable character. Being based on an agricultural system the biobased PLA gives rise to higher contributions to acidification, photochemical ozone creation, eutrophication, and farm land use compared to the fossil polymers. The application spectrum of PLAs is expanding, and there are opportunities to replace various fossil-based polymers. This facilitates climate change mitigation and reduces dependence on fossil and scarce resources while promoting the use of local and renewable resources. It is evident that in emerging green economies agricultural technology will form an integral part in the changeover towards a more sustainable industry and society.