(624a) Towards Sustainable Circular Economy: Design Framework and Application to Grocery Sacks

Numerous directives and strategies [1,2] aim to establish a Circular Economy (CE) by value retention from a consumer discarded product within the technosphere, thereby implicitly reducing the burden on the ecosphere. Many opportunities to recycle, down-cycle or up-cycle products have been identified each contributing to a different degree of circularity. However, for the CE to be sustainable, that is to obtain a Sustainable Circular Economy (SCE), there is a need to holistically evaluate entire value chains of the product and other down-cycled or up-cycled material. Further, there needs to be a method to systemically find the environmental and economic implications of various value chain pathways and quantify the trade-offs with the establishment of circularity. There is also a requirement to analyze the performance of pathways for multiple stakeholders of circularity along the value chain by means of appropriate CE metrics. We propose a life-cycle design based framework to identify optimal pathways that are best aligned with the goals of SCE from the perspective of multiple stakeholders.

Life-cycle assessment (LCA) is a powerful tool for assessing holistic environmental impacts due to a certain configuration of network flows in a value chain. With a few modifications to this tool such as including the consumption and disposal modules, it can be used to represent circular value chain networks. Further, using mathematical properties of matrices, principles of allocation and displacement [3] and flow conservation, we can use LCA to describe superstructure networks of many alternative value chains. Further, we present the use these life-cycle superstructure networks as basis for a multi-objective optimization problem formulation [4], thereby demonstrating the proposed framework.

In this talk, we will present a novel computational framework to model, assess and design sustainable circular systems by means of a superstructure pathway design approach. The framework is capable of quantifying trade-offs between circularity objectives for multiple stakeholders and environmental objectives. Thus, it allows the governing bodies and other stakeholders to make calculated decisions related to establishing value chains to ensure SCE. It can also be used to find the viability of a novel product substitute in a value chain by including it within the superstructure, and identify opportunities for innovation. We apply the framework to a case study for grocery sacks value chain and consider multiple plastic bag options such as HDPE, LDPE, PP and PLA [5]. Further, we also include the choices related to waste management options at the material recovery facility. Using the framework, we are able to obtain optimal value chain pathways under current technosphere constraints that minimize global warming potential, life cycle cost or maximize circularity metrics. Further, we plot the trade-offs as pareto surfaces and perform sensitivity analyses on various parameters such as reuse of bags and consumer littering behavior. It is observed that a combination of reusable polypropylene bags and compostable polylactic acid bags can lead to a favorable pareto optimal solution for SCE. Numerous other insights on the waste management pathways and effectiveness of reuse of bags are also derived from the framework outcomes.

References

[1] EMF - Ellen MacArthur Foundation. Report: What is a Circular Economy?, 2010.

[2] Yuliya Kalmykova, Madumita Sadagopan, and Leonardo Rosado. Circular Economy – From review of theories and practices to development of implementation tools. Resources, Conservation and Recycling, 135: 190-201, 2018.

[3] Dieuwertje L. Schrijvers, Philippe Loubet, and Guido Sonnemann. Critical review of guidelines against a systematic framework with regard to consistency on allocation procedures for recycling in LCA. International Journal of Life Cycle Assessment, 21(7): 994-1008, 2016.

[4] Adisa Azapagic. Life cycle assessment and its application to process selection, design and optimization. Chemical Engineering Journal, 73(1):1-21, 1999.

[5] Didem Civancik-Uslu, Rita Puig, Michael Hauschild, and Pere Fullana-i Palmer. Life cycle assessment of carrier bags and development of a littering indicator. Science of the Total Environment, 685: 621-630, 2019.