Life cycle assessment of single use thermoform boxes made from polystyrene (PS), polylactic acid, (PLA), and PLA/starch: cradle to consumer gate
Suwanmanee, U; Varabuntoonvit, V; Chaiwutthinan, P; Tajan, M; Mungcharoen, T; Leejarkpai, T
Currently, the bio-based plastics have been drawing
considerable attention from the packaging industry as a sustainable solution for replacing
petroleum-based plastics in order to reduce the accumulation of plastic waste in the environment.
This work has benchmarked the environmental impact of bio-based against petroleum-based plastics
for single use boxes. In this paper, the cradle to consumer gate environmental impact data of
these boxes was calculated and reported as part 1. End-of-life options of both bio- and
petroleum-based boxes are an important subject which will be further studied for part 2. The
energy sources in this work were taken from the Thailand energy database namely: Thai electricity
grid mix (TEGM), Thai coal electricity (TCE), Thai natural gas combine cycle (TNGCC), and Thai
coal integrated gasification combine cycle (TIGCC). The materials studied were polystyrene (PS)
derived from petroleum, polylactic acid (PLA) derived from corn, and PLA/cassava starch blend
(PLA/starch). The tray with lid (herein after called box) was processed in a plastic
manufacturing in Thailand using cast sheet extrusion and then thermoforming techniques. The
functional unit is specified as 10,000 units of 8.0 x 10.0 x 2.5 cm of PS, PLA, and PLA/starch
boxes which weigh 447.60, 597.60, and 549.56 kg, respectively. Three impact categories; namely
global warming potential including direct greenhouse gas, and indirect land use change (LUC)
emissions, acidification, and photochemical ozone formation are investigated. Finally, the
normalization results including and excluding LUC consideration were compared and reported. The
results from this study have shown that the total environmental impact including LUC emission of
bio-based boxes were different when the various energy sources were supplied throughout the life
cycle production stage. It can be seen that the PS box has lower environmental impact than PLA
and PLA/starch boxes when TEGM, TCE, TNGCC, and TIGCC were used as energy supplied. LUC of
renewable feedstocks, such as corn and cassava, were considered as the biggest impact of absolute
scores of PLA and PLA/starch boxes. These results are consistent with Piemonte and Gironi (2010).
PLA and PLA/starch boxes give a slightly higher environmental impact than the PS box by 1.59 and
1.09 times, respectively, when LUC was not accounted in the absolute scores and clean energy
TIGCC was used throughout the life cycle.