(385d) De-Plasticization of Expanded Polystyrene (EPS) Wastes into Value-Added Carbon Materials

Expanded polystyrene (EPS) or foam #6, popularly known as “styrofoam”, is widely used in various household and industrial applications, like home and appliance insulation, packaging materials, food containers and insulators, road bank stabilization system, and many others. EPS is one of the highest single-use plastics with minimum recycling value. Approximately 1% of EPS is recycled, 99% is accumulated in the solid waste. EPS-based materials are responsible for 30% of total landfill waste, and in the U.S. alone, about 1,369 tons of EPS is accumulated in the waste every year. EPS is not bio-degradable, and it causes hazardous conditions for both land and aquatic life. In the environment, it may slightly depolymerize to produce traces of styrene which is a suspected carcinogen. As 90% of EPS is air, it is very light, voluminous, and inexpensive. These reasons make the traditional recycling of EPS unprofitable and unacceptable by most recycling plants. Therefore, upcycling EPS-based objects into value-added materials may provide a large impetus toward waste minimization and the economy of EPS.

We have developed the technology to sustainably de-plasticize EPS into (i) Carbon molecular sieve (CMS), (ii) Activated carbon, and (iii) Synthetic graphite. Unlike other plastics, when pristine EPS is pyrolyzed or carbonized, there remains to no carbon or char yield. Our technology will first convert into a stabilizing form, which will yield about 90% carbon upon pyrolysis with respect to pristine EPS. There is an extremely large pool of applications of carbon molecular sieves and activated carbons, including water purification, air purification, gas separation, mercury control, electrodes, supercapacitors, fuel cells, pharmaceutical product purification, medical applications for stomach detoxification, gas masks, and many others. Synthetic graphite is used as an anode of Li-ion batteries, furnace electrodes, coatings, conductive films, and others. Converting EPS wastes to these value-added carbon materials will not only help to remove the pollution caused by EPS but also help the EPS from being banned in the future. In addition, there is a supply chain problem of all these carbon materials and a significant portion of the domestic demands of the United States is met by imported materials from foreign countries. Therefore, domestic manufacturing of these carbon materials will partly solve the current supply chain problem.