Special edition spring 2022


Cost competitiveness of sustainable bioplastic feedstocks – A Monte Carlo analysis for polylactic acid

By Claudia Wellenreuther, André Wolf, Nils Zander

The HWWI is part of the EU Horizon 2020 project “BIOPLASTICS EUROPE”. Our work within this project focuses on the economical and ecological assessment of product life cycles, namely bioplastic products. The following peer-reviewed paper is a result of these assessments. We estimated the costs of PLA (a type of bioplastic polymer) when using different feedstocks in production.

For the production of PLA, different feedstocks from food production (corn, wheat, sugar cane) are used at present. To avoid competition between bioplastic and food production, the search for alternative feedstocks is necessary. Our estimations could show that PLA from corn stover (a by-product of corn production) is already competitive with PLA from corn grain in terms of cost structure in parts and thus could be an alternative in PLA production.

This study undertakes the first meta-analysis of the costs of producing bio-based plastic polymer PLA from the two alternative feedstocks corn grain and corn stover. While PLA production based on corn grain has long been established on a large scale, the feedstock alternative corn stover, which is interesting from the perspective of land use savings, has not yet reached the stage of mass production. As far as the current cost situation is concerned, we estimate that corn stover-based PLA is already competitive with corn grain-based PLA in terms of variable costs. Higher energy expenses in the corn stover scenario are compensated by lower costs of feedstock procurement, given that corn stover is generated as a by-product of corn cultivation. However, this is overshadowed by the disadvantage of higher fixed costs.

Our Monte Carlo simulations demonstrate that this is a fairly consistent result despite the high degree of data uncertainty in recent studies. Moreover, we enrich the literature with a future perspective, by estimating long-term scenarios based on external price forecasts. They indicate that technological progress will continue to be essential for cost competitiveness in the future. Expected long-term changes in the prices of crucial inputs alone are estimated to be insufficient for leveling the playing field for the two feedstock alternatives. Instead, a key issue will be the extent to which the two production alternatives can benefit from learning effects in the context of production increases. In this regard, the fact that corn stover-based PLA represents the less mature technology generally implies higher learning potentials. However, the degree to which these potentials can be realized will also depend on the speed at which corresponding production capacities can be built up. In the upscaling phase, capacity growth is likely to be restrained by the demand side. To reach a state of competitiveness, it will be crucial for producers to convince end users of the environmental superiority of such a feedstock switch. The current public debate on land usage of the bioeconomy sector can be supportive here. However, for a market-wide feedstock switch, additional policy incentives are likely to be required. This can take the form of feedstock-specific adjustments in areas such as labelling and taxation, thereby taking more holistic view on the plastic life cycle in policy-making.

At the same time, one needs to be aware that corn stover is only one of many innovative feedstock options that have proven to be technically feasible. Achieving an optimal balance of cost competitiveness and ecological impacts will require consistent life cycle comparisons between different second- and third-generation feedstock technologies. This represents an important task for future research.

Read the full text of the article in the journal "Cleaner Engineering and Technology" here.

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Dr. Claudia Wellenreuther
Nils Zander

HWWI Research Paper

Cost structure of bio-based plastics: A Monte-Carlo-Analysis for PLA