Sustainable Pathway Design for Plastic Packaging

Often, solutions to grave environmental problems are hand-waving arguments based on empirical relations or expert opinions about macroscopic effects of microscopic alterations. The menace of plastic wastes and floating man-made islands, for one, needs a systemic evaluation of novelty in the field, whether it is product design, process modification, supply chain reformation or policy making. The intent of this project is to tackle this multiple scale design problem using mathematical tools of optimization, dynamics of ecosystem and economy.

This integrated design methodology (subsequently software), aids to find impacts of shocks imposed upon the pathway of plastic packaging, thereby guiding research towards novel chemistry research and governmental decisions like taxes and bans. The trade-off between costs of new businesses or policies and saved environmental impacts can be produced and direction of favored novelty can be found. 

Needless to say, the masses would benefit from prudent decision making on the part of chemical industries and governments towards Circular Economy of plastics.

Problems:

1. Chemical Industry Scale - Design of novel polymers is often misguided or short-sighted. For example, degradable plastics packaging can interfere with polyethylene and polypropylene recycling process, making the net outcome of product reformation detrimental until the sluggish reformation of industry has passed. Product and process design with consideration of life cycle environmental and economic impacts is a challenging problem this modelling framework will solve.

2. Supply Chain Scale - Choices for means and methods of collecting segregated or mixed recyclables and feasible incentives, to ensure overall circularity and social reformation, need to be made based on models and correlations.

3. Economy Scale - Influence of tax and bans on products and competition is the gray area in designing novel pathways, which this framework aims to solve using integrated assessment models.

While the project will potentially influence all consumers, manufacturers and agencies indirectly, by promoting globally optimal strategies; direct influence will be upon

1. Polymer scientists and Research granting committees - to ascertain heuristic impacts of novel packaging materials

2. Governmental bodies and Non-profits - to find optimal supply chain strategies and coping with complicated human behavioral factors of uptake of recycled content 

3. Economists - to be able to find and assign value for environmental impact of wastes, primarily plastics. Hence, eliminating errors due to cheap substitutability of wastes.

This work addresses the aforementioned problems by combining reductionist and holistic approaches towards technology design and decision making. It involves development of a multiple scale modelling framework that accommodates molecular pathways, process flow sheets, supply chain activities and economic scale activities, integrated via inter-scale flows and multi-disciplinary models. A non-linear optimization problem, formulated based on this framework can find an optimal solution for operation of activities involved in any particular technology, product or a class of similar products. The framework also captures life cycle emissions and resource use, not only for a confined process boundary but also along the supply chain till the end of life. 

The strength of the model lies in the fact that it expands the analysis boundary from the process scale to the planetary scale (using Environmentally Extended Input Output Models), considers cross-linked flows and avoids double counting activities within scales by disaggregation. These attributes of the model are directly inspired from the Process to Planet (P2P) framework and Integrated Life Cycle Assessment models. The novelty in this work,is in linking reaction pathways and associated decision variables in the optimization scheme. A molecular reaction network is used as basis for development of the process scale mass and energy flows. These flows between various unit operations are linked either by empirical yield constraints or kinetics/thermodynamics for reaction and separation (based on availability of data). The bottlenecks and influential units in the process scale can be found using sensitivity analysis. The process scale is further linked to value chain and economic scales.

Using effective network analysis optimization methods like Reaction Network Flux Analysis (RNFA), in conjugation with P2P. These models are made compatible to be used together and the scales are connected with flows and cut-offs. This aids in finding an optimal pathway for production of a commodity from a holistic viewpoint.

Therefore, the integrated model can find the best out of a set of proposed novel designs for a commodity sector, while considering its life cycle and eco-system services. Having included molecular components and their networks, it is possible to fill the voids remaining after data acquisition by estimates obtained from group contribution theory.  Hence, this framework can assess whether a novel technology truly abides by the standards  of ‘Eco-Design’ and ‘Green Chemistry’. It can tackle the pathway design problem while considering constraints, emissions and impact credits at multiple scales simultaneously.

The nature of this methodology, namely integrated life cycle analysis, has rarely been used for design of pathways and molecular structures. This way of integrating process design and economic policies to product design has great promise.

- Life Cycle Assessment: Attributional and Consequential

- Optimization using branch and bound algorithms (using GAMS and python interface)

- Spatio-temporal modelling (using ArcGIS)

Naturally, a design methodology which has the potential to reform technologies and policies for increasing circularity with minimal impact to the economy, is crucial for plastics. We intend to address this problem