Styrene Monomer Recovery Technology for Styrofoam: Exploration of Chemical Recycling Combining Volume Reduction and High Purity Recovery Late 1990s to Early 2000s

Styrene Monomer Recovery Technology for Styrofoam: Exploration of Chemical Recycling Combining Volume Reduction and High Purity Recovery Late 1990s to Early 2000s
The styrene monomer recovery technology for styrene foam is a chemical recycling technology that attracted attention from the late 1990s to the early 2000s as the problem of waste plastics became more serious in terms of both quantity and quality. This method, which heats used styrene foam at high temperatures and recovers styrene monomer through a distillation process, was characterized by its ability to recycle approximately 70% of the input as raw material with a purity of 99% or higher.

At the time, styrene foam was widely used in society as food trays, packaging materials, and cushioning materials, but its light weight and bulkiness were major obstacles to its recovery and processing. Its small weight but extremely large volume made collection and transportation inefficient and costly for local governments and businesses. In addition, they were susceptible to staining and coloration from food applications, and material recycling tended to limit their use due to unstable recycled quality.

The styrene monomer recovery technology offers a structural solution to these problems. The primary advantage of this technology is that it fundamentally improves the transportation efficiency problem, as it enables significant volume reduction by eliminating the foam structure through high-temperature heating. Furthermore, the second advantage was that by decomposing the polymer once and returning it to monomer, the effects of contamination and additives can be removed, ensuring quality close to that of virgin raw materials. This is a different approach from material recycling, which assumes quality degradation, and was highly evaluated for its completeness as a raw material cycle.

In Japan in the early 2000s, sorted collection was becoming institutionally established with the enactment of the Containers and Packaging Recycling Law, but the next issue was how to circulate the recovered resources with high added value. In the food tray field, in particular, the requirements for safety and quality are strict, and it has not been easy to expand the use of recycled materials. The styrene monomer recovery technology showed the possibility of returning styrene monomers to these fields as raw materials, and was expected to be one of the few options that could be considered for recycling into food applications.

On the other hand, this technology requires high-temperature processing, which requires large energy consumption and capital investment, so securing business feasibility was always an issue. Therefore, at the time, this technology was often positioned as a complementary technology specialized for styrene foam, which is bulky and difficult to recycle, rather than as a universal technology that can be applied to all plastics.

Nevertheless, this styrene monomer recovery technology is important in that it blurred the boundary between waste treatment and chemical raw material production, and embodied the idea of recycling plastics again as raw materials for the chemical industry. This attempt to simultaneously solve the multiple constraints of volume reduction, transportation, quality, and application symbolized one of the achievements of the chemical recycling philosophy in the early 2000s.