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Many corporations and nations have pledged to reach net-zero emissions within a few decades. Meeting such targets for greenhouse gases, plastics, etc. requires systematic methods to guide investment in technologies and value-chain alternatives, and develop roadmaps. The proposed framework is a multi-period planning model to guide optimal reforms in cradle-to-cradle life-cycle networks across the time horizon. It aims to meet environmental targets while minimizing the total annualized marginal cost of natural resources and the investment cost associated with adoption of novel technologies. This considers the evolution of technology readiness levels as S-curves or continuous time Markov-chains. Integrated Assessment models account for climate change, decarbonization due to energy mix changes, and carbon taxes. Multiple climate change scenarios and shared socioeconomic pathways are used to model the future. In addition to providing roadmaps, the outputs can also be used to identify technologies that will be robust to future scenarios. 

As the demand for PET plastic products continues to grow, developing effective processes to reduce their pollution is of critical importance. Pyrolysis, a promising technology to produce lighter and recyclable components from wasted plastic products, has therefore received considerable attention. In this work, the rapid pyrolysis of PET was studied by using reactive molecular dynamics (MD) simulations. Mechanisms for yielding gas species were unraveled, which involve the generation of ethylene and TPA radicals from ester oxygen−alkyl carbon bond dissociation and condensation reactions to consume TPA radicals with the products of long chains containing a phenyl benzoate structure and CO2. As atomistic simulations are typically conducted at the time scale of a few nanoseconds, a high temperature (i.e. >1000 K) is adopted for accelerated reaction events. To apply the results from MD simulations to practical pyrolysis processes, a kinetic model based on a set of ordinary differential equations was established, which is capable of describing the key products of PET pyrolysis as a function of time and temperature. It was further exploited to determine the optimal reaction conditions for low environmental impact. Overall, this study conducted a detailed mechanism study of PET pyrolysis and established an effective kinetic model for the main species. The approach presented herein to extract kinetic information such as detailed kinetic constants and activation energies from atomistic MD simulations can also be applied to related systems such as the pyrolysis of other polymers. 

The urgency of action toward mitigating climate change and reducing material leakage into the environment is inspiring a plethora of innovative technologies, supply chains, and policy actions. These are targeted toward reducing greenhouse gas emissions, natural resource uptake, and decoupling technological systems from fossil-based linear economies using circularity strategies. Industrial and governmental stakeholders are keen to rank these proposed eco-innovations and emerging alternatives based on their scope of contributing to a sustainable and circular economy to meet global warming curtailment and pollution mitigation targets. We describe a novel methodological framework that relies on a multiobjective optimization of cradle-to-cradle life-cycle pathways to screen from a large database of conceptual eco-innovations and rank them based on their potential for establishing a Sustainable Circular Economy (SCE). This methodology is implemented for a motivating case study to evaluate numerous packaging eco-innovations based on their improvement potential and readiness for adoption within the grocery bags value-chain network. It is demonstrated that a preliminary screening step identifies the 10 most promising eco-innovations from a large superset of alternatives, which if developed and adopted can help transition the value chain to a future scenario with net-zero emissions and adherence to the recycled and renewable-content targets set by the United States Plastics pact but at a higher cost. 

Global goals like “Net-zero”, “Nature-positive”, and “Socially Just” require human activities to reduce emissions, restore nature, and be socially equitable. This work proposes an approach that includes ecological capacity and social justice requirements to guide engineering decisions and designs. We utilize the supply and demand of ecosystem services to identify the safe and just operating space1,2. The ecologically safe space is determined by the multiscale framework of Techno-Ecological Synergy (TES). The degree of overshoot quantifies the absolute environmental sustainability (AES) at the relevant spatial scale3,4. For the socially just space, we calculate a minimum threshold of necessary goods and services to meet basic food, energy, and water5 needs. We demonstrate this approach by a multiobjective supply chain design of Li-battery which minimizes the ecological and social overshoot simultaneously.