M.S. Thesis: Industrial-scale Processes for Transforming Mixed Plastic Wastes to Oil.

By Yuji Lin

Advisors: Dr. A.C. (Thanos) Bourtsalas and Prof. Nickolas J. Themelis

Department of Earth and Environmental Engineering
Fu Foundation School of Engineering & Applied Science
Columbia University

December 2018

In 2015, the world produced 407 million tons of plastics and generated 302 million tons of plastic wastes. Only 19.5% have been reported as “recycled”; the rest of plastic wastes were discarded in landfills or combusted with energy recovery (“Waste to Energy” or WTE). Since 1950 when plastics came to use, about 4.6 billion tons of plastic wastes have been discarded, mostly in landfills or WTE power plants.

However, landfilling, as the primary waste management for plastic wastes, is not sustainable. Environmental pollution and limited land resources close to urban centers indicate that landfilling is no longer a wise method to manage the increased plastic wastes, and a more efficient and environmental-friendly way should be implemented.

Since plastics are materials derived from petrochemicals, the idea of converting plastic wastes back into oil by pyrolyzing has been pursued. Pyrolysis is a thermal decomposition process at high temperature in the absence of oxygen; plastic materials are composed of high-molecular carbon chains that are cracked into liquid and gas molecules during the pyrolysis process. In this study, some industrial-scale processes for transforming mixed plastic wastes to fuel oil were examined. There are three plastic liquefaction plants in Japan and four plastic pyrolysis companies in China.

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