New breakthrough in polystyrene recycling promises environmental and economic benefits
By George George Idowu
A pioneering method for recycling polystyrene, developed by a team of chemical engineers, could revolutionize plastic recycling and significantly reduce environmental impact.
Researchers from the University of Bath in the UK and Worcester Polytechnic Institute (WPI) in the US have unveiled a novel chemical recycling process, known as pyrolysis, which breaks down polystyrene into its fundamental components.
This technique not only enhances recycling efficiency but also promises to be both cost-effective and energy-efficient.
The new method addresses a long-standing challenge with polystyrene recycling. Traditionally, less than 5% of polystyrene is recycled due to its bulkiness and the inefficiencies of conventional recycling methods.
The innovative pyrolysis technique developed by the collaborative team could enable up to 60% of polystyrene to be recycled into reusable styrene.
“Chemical recycling techniques are a major focus within chemical engineering right now,” explains Dr. Bernardo Castro-Dominguez, senior lecturer at the University of Bath and co-director of the Centre for Digital, Manufacturing & Design (dMaDe). “Cost- and energy-efficient ways to break down plastics like polystyrene are urgently needed.”
Pyrolysis involves heating polystyrene to extremely high temperatures in an oxygen-free environment. This process prevents the material from igniting and instead breaks it down into monomers, which are then purified and reconstituted into new polystyrene.
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Remarkably, producing 2.2 pounds (one kilogram) of this new material requires less than 10 megajoules of energy—equivalent to running a typical microwave for about 30 minutes.
Michael Timko, professor of chemical engineering at WPI, highlights the potential impact of this technique: “Our analysis finds polystyrene to be an ideal candidate for a chemical recycling process. Surprisingly, the process is energetically efficient and potentially economically competitive.
Traditional recycling methods degrade polystyrene over time, compromising its strength and flexibility. Additionally, its bulkiness leads to high transportation costs and limited acceptance at recycling facilities.
In contrast, the new process utilizes a pyrolysis reactor, a heat exchanger, and two distillation columns to decompose polystyrene into high-purity monomer grade styrene and reusable petroleum-like by-products.
The process yields a 60% efficiency rate, meaning 600 grams of 99% pure styrene can be recovered from each kilogram of used polystyrene.
The environmental benefits of this method are significant. The cost to reduce carbon emissions through this process is about $1.5 per ton of CO2, considerably lower than many existing recycling methods.
The researchers also advocate for policies to incentivize polystyrene recycling, which would enhance the economic viability of this new technique and address a major waste management issue.
This breakthrough is part of a broader trend in polystyrene recycling innovation. Earlier research by Dr. Xiaodan Li and Professor Dirk Tischler identified a bacterial enzyme capable of degrading styrene, suggesting future potential for biological recycling methods.
In summary, this new pyrolysis-based recycling process offers a promising solution to the global challenge of polystyrene waste, combining economic feasibility with substantial environmental benefits. As the technique gains traction, it could significantly transform the recycling landscape and contribute to more sustainable plastic management practices.
