TotalEnergies Corbion has published the life cycle assessment (LCA) of its chemically recycled Luminy PLA. The company operates a 75,000 tons per year polylactic acid (PLA) production facility in Rayong, Thailand. Since the start of operations in 2018, TotalEnergies Corbion has been chemically recycling its internal waste from virgin Luminity PLA (vPLA) production through a hydrolysis depolymerisation process.
The company published the LCA of virgin Luminy PLA in 2019. Taking it as a reference point, it has now published the results for recycled PLA (rPLA).
Results show that the Global Warming Potential (GWP) of Luminy 30% rPLA, considering its biogenic carbon content, is 0.19 kgCO2/kg of PLA, whereas Luminity vPLA emits 0.51 kgCO2/kg of PLA. The study concludes that the ‘[chemical] recycling of PLA as a production process has a lower impact compared to its production from virgin feedstock’.
Let’s look at how the results were calculated.
The LCA’s methodology is aligned with ISO 14040/4 and was performed using the software SimaPro. The LCA is for PLA from sugarcane in Thailand and considered the feedstock used for rPLA as an average of two waste streams: post-industrial waste from a PLA fibre application in Europe, and post-consumer waste of bottle streams from Asia.
The scope of the study is cradle-to-gate, meaning that use phase and end-of-life are not considered, for both vPLA and rPLA. The functional unit is 1 kg of Luminity PLA. Recycled PLA substitutes virgin PLA in the same amounts because the ‘chemical recycling process ensures identical quality and functional equivalence’, the study says.
Crucially, the Global Warming Potential (GWP) results include the biogenic CO2 in the polymers, corresponding to the uptake of CO2 during the growth of sugarcane and captured in the PLA waste used as feedstock for rPLA. The biogenic CO2 is calculated based on the EN16785 standard.
“This approach considered biogenic carbon as an intrinsic property of the material. By using this approach, the biogenic carbon considered for the rPLA does not correspond to a CO2 uptake but to the biogenic carbon present in the waste used as raw material. Both for virgin and recycled PLA, the emissions of biogenic CO2 shall be considered for the GWP at the ultimate end-of-life,” the study reads.
This means that CO2 release at the ‘grave’ stage, e.g. incineration or compositing, are not considered in these LCAs for vPLA and rPLA. Given that is the case for both polymers, that does not invalidate comparisons in this context.
The cradle-to-gate GWP of virgin lactic acid is 501 kg CO2eq/ton of vPLA, the results show. This value includes the CO2 uptake of 1833 kg CO2/ton of vPLA, calculated based on the biogenic carbon content in the polymer.
The cradle-to-gate GWP for rPLA is significantly lower than for vPLA. “This is explained by the reduction of the high-impact inputs for vPLA manufacture, related to lactic acid production: sugarcane crop cultivation, lactic acid fermentation and purification,” the report found.
Importantly, results show that the depolymerisation via hydrolysis is an energy-efficient process having a low contribution to the GWP of rPLA, as show in the graph below.
"Depolymerising PLA via hydrolysis is an energy-efficient process allowing us to close the loop and increase circularity for a biobased material,” said Maelenn Ravard, regulatory and sustainability manager at TotalEnergies Corbion. “The LCA results only confirm this statement."