Polystyrene (PS) is one of the most widely used plastics in the world, and one of the least recycled. Used to make fruit and vegetable baskets, yoghurt pots, takeout boxes and various kinds of packaging, the petroleum-based plastic is responsible for generating significant greenhouse gas (GHG) emissions.
In 2016, global annual polystyrene production reached 24 million tons and consumed 50 billion liters of oil; more than two percent of global oil reserves, according to the World Energy Council. But if we are to limit global warming to a 2 degree Celsius increase, one-third of the world’s oil reserves will have to stay in the ground, according to a study published by science journal Nature in 2015.
In Ville d’Anjou in the suburbs of Montreal, Canada, the young company Polystyvert has been honing a technique that might be one of the most promising solutions yet for this issue. Its recycling process would reduce up to 83 percent of the GHG emissions involved in virgin resin production. “There’s only a handful of existing solutions for treating polystyrene,” said Andrée-Lise Méthot, founder and managing partner of Cycle Capital Management, a cleantech venture capital investment platform with offices in Canada, the United States and China. “Their method involves dissolving the plastic in essential oils so it can be transported more easily.”
According to the most recent data from the Quebec government corporation for recovery, reuse and recycling, Recyc-Québec, 80 percent of polystyrene waste generated by Quebec’s citizens is thrown into the trash can. Existing recycling options for polystyrene are limited — less than one-third of the waste stream gets treated and the activity is hardly profitable.
One of these options is compressing polystyrene into “logs” using a machine, but the approach has three main problems: transportation (this type of plastic occupies a lot of space), contamination (not all contaminants can be removed by hand) and versatility (the logs have limited uses). Another option, transforming solid plastic waste back to a liquid state at a very high temperature, offers more flexibility than compression and a greater variety of products can be made as a result, but it’s highly energy consuming.
The recycling technique developed by Polystyvert involves dissolving polystyrene in a concentrator filled with essential oils. The liquid is then poured through mesh, which catches any undissolved matter, and purified through flocculation – remaining contaminants form flakes that can be easily removed. Finally, an isolation liquid is added to separate 80 percent of the essential oils. The resulting paste is washed to purify the polystyrene, which is then turned into 98 percent pure transparent granules that can be reused to produce a vast variety of products.