The United States recycles less than 10% of generated plastic waste. Low recycling rates create problems including: 1) leakage of waste plastic into the natural environment and accompanying fragmentation into microplastic particulate pollution that negatively affects ecosystems and human health, 2) depletion of our oil and natural gas supplies - the need to use lots of energy to make new plastics, and 3) increased greenhouse gas emissions compared to using recycled materials. The microplastics pollution problem is particularly concerning because these small plastic particles are entering the human food chain, and the effects of microplastic consumption of these very small plastic particles is currently unknown. Furthermore, several analyses have shown enhanced recycling will lead to dramatic job growth; upwards of a million jobs could be created. In this Emerging Frontiers in Research and Innovation project an interdisciplinary and diverse team will work to transform the plastics industries to eliminate end-of-life waste. Revolutionary approaches to sorting, cleaning, and transforming waste plastics enables a transformational outcome; present “end of life†thinking becomes holistic “end of cycle†thinking as more plastics are repeatedly used rather than thrown into a dump. The knowledge and technologies developed through this research will enable greater rates of plastics recycling, more recycling creates jobs while helping to protect the environment and human health. Investing in improved recycling technologies will help the USA remain competitive in the ever-changing global economy. Participation in programmatic activities is inclusive and fostered by novel cross-disciplinary interaction with Community Sustainability programs and through delivery of outreach programs for K-12 and undergraduate college students. A Diversity Team will work in partnership with the tribal colleges of Michigan, which are Minority-serving institutions, to support meaningful participation in STEM research by the Native American community. A deep and culturally diverse awareness of sustainability issues will be fostered through incorporation of traditional learnings into program pedagogy.
The goal of the project is to develop and demonstrate new approaches to recycling plastics. The scope of the project includes novel ways to depolymerize polymers and repolymerize the products into valuable materials. Controlled experimentation complemented by chemical kinetic models, molecular-scale simulations, and machine learning are the primary methods used. Specialized expertise in life cycle analysis (LCA) will be used to assess and establish the utility of the new and innovative approaches. Chemical recycling through depolymerization is accomplished through cascading of chemically and biochemically catalyzed transformations. Consistent with a rapidly emerging innovation trend in the chemical sciences, synergistic combinations of chemically and enzymatically catalyzed transformations will be demonstrated through the case study of chemical oxidation followed by enzymatically catalyzed decarboxylation to create naptha (mixed alkanes). The resulting low-temperature cascaded approach will be compared to the present state-of-the-art of thermal pyrolysis; LCA will guide process improvements and be used to assess if this new cascading approach provides improved sustainability metrics. A direct comparison of a high-temperature pyrolysis process with a low-temperature cascading pathway can substantially advance knowledge in the plastic recycling field; to date, no such comprehensive evaluation is available. However, the implications regarding which of the two pathways deserves future emphasis are profound. The innovative use of combined reactor-separators will be demonstrated and is expected to be a superior approach to producing monomers from waste plastics. Repolymerization will be pursued as a means of “reincarnating†end-of-life plastic into brand new, high-value, specialty polymers for use in their next life. Oxidation of waste polyethylene will be used to produce dicarboxylic acids, and the innovative use of ammonolysis on waste polyethylene terephthalate will provide aromatic diamines. Resulting monomers are to be incorporated into newly formed polymers including polyesters, polyamides, polyaramids, polyesteramides, and polyesteraramids. These resulting polymers are considerably more expensive (2-3x) than the reclaimed waste plastic, providing an economic incentive that can effectively increase recycling rates.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
