Plastic Recycling

Study on how to simplify chemical recycling

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Through chemical recycling waste products may be turned back into natural resources by physically breaking down plastic into the smaller molecules it was originally produced from. In this sense it ist at the core of a circular economy since from there new products made from recycled plastic can be produced. In their new research Professor Fengqi You and doctoral student Xiang Zhao detail a framework incorporating several mathematical models and methodologies that factor everything from chemical recycling equipment, processes and energy sources, to environmental effects and the market for end products.

You’s framework can quantify the environmental consequences of market dynamics that typical life-cycle sustainability assessments would overlook. It’s also the first to combine superstructure optimization – a computational technique for searching over a large combinatorial space of technology pathways for minimizing cost – with life-cycle analysis, market information and economic equilibrium.

What technology would we use in chemical recycling?

“It’s a chemical process and there are so many possibilities,” You said. “If we want to invest in chemical recycling, what technology would we use? That really depends on the composition of our waste, the variants of polyethylene plastic, and it depends on current market prices for end products like fuels and hydrocarbons.”

Environmental consequences of chemical recycling depend on variables such as supplier process of chemical feedstocks and products. For instance, the framework found that producing butene onsite as opposed to having it supplied can reduce photochemical air pollution from recycling plants by nearly 20%, while onsite use of natural gas increases more than 37% of potentially harmful ionizing radiation.

“There’s always something we can twist and adjust in the technology and process, and that’s the tricky part,” said You, who added that as new chemical recycling techniques emerge and markets change, consequential life-cycle optimization will remain a powerful tool for guiding the emerging industry.