Scientists Develop Innovative “Thermal Barcodes” That Could Transform Plastic Recycling

Photo by Nick Fewings on Unsplash

Plastic recycling has long faced a frustrating challenge: accurately sorting different types of plastic quickly and efficiently. Now, a team of researchers at the University at Buffalo (UB) may have found a groundbreaking solution — one that uses heat instead of traditional optical scanners.

Their new technology, called Transient Thermal Barcodes, could significantly improve the way recycling facilities identify and separate plastics, making recycling more effective and reducing the amount of waste that ends up in landfills.

Why Plastic Sorting Is Such a Big Problem

Every day, millions of tons of plastic waste are collected from homes and businesses. Before these materials can be recycled, they must be sorted according to their plastic type.

This process often takes place in material recovery facilities, where plastics are separated from other waste and then sorted into categories such as PET bottles, PVC pipes, or polyethylene packaging.

Unfortunately, current sorting methods are far from perfect.

Many facilities still rely heavily on manual labor, which can lead to mistakes and contamination. Even advanced technologies such as near-infrared spectroscopy and Raman spectroscopy have limitations. Some struggle to identify black plastics, while others operate too slowly or lack the accuracy needed for large-scale industrial recycling.

These challenges contribute to the disappointing global plastic recycling rates seen today.

A New Approach Inspired by Barcodes

Researchers at the University at Buffalo wondered whether a system similar to a barcode scanner could help solve this problem.

Traditional barcode scanners use light to read printed patterns on products. The UB team took a different approach. Instead of reading visible barcodes, they developed a method that reads a plastic’s unique molecular signature.

The result is what they call a three-dimensional transient thermal barcode.

According to Professor Amit Goyal, who led the project, the goal was to create a practical, affordable technology that recycling facilities could eventually integrate into their existing systems.

If successful, the technology could improve sorting accuracy, reduce contamination, and increase the amount of plastic that can be recycled and reused.

How Thermal Barcodes Work

Every type of plastic has a unique molecular structure. The researchers designed a system that shines specific mid-infrared wavelengths onto plastic materials moving along a conveyor belt.

Mid-infrared light is particularly useful because scientists often refer to this region as the “molecular fingerprint” zone. Different plastics absorb these wavelengths in unique ways.

When the plastic absorbs the infrared light, its molecular bonds begin to vibrate. These vibrations generate tiny, temporary heat patterns on the surface of the material.

A thermal camera captures these heat signatures.

The resulting pattern acts like a barcode, revealing the plastic’s identity. Because each type of plastic produces a distinct thermal response, the system can quickly determine what kind of plastic is being analyzed.

Successfully Identifying Common Plastics

During testing, the researchers used six different infrared wavelengths to identify six of the most common plastics found in consumer waste:

• PET (Polyethylene Terephthalate)
• PP (Polypropylene)
• PS (Polystyrene)
• HDPE (High-Density Polyethylene)
• LDPE (Low-Density Polyethylene)
• PVC (Polyvinyl Chloride)

One particularly impressive achievement was the system’s ability to identify black plastics.

Black plastic has traditionally been difficult for many optical sorting technologies to recognize because the dark pigments absorb light differently. As a result, black plastic items often end up in landfills even when they could be recycled.

The thermal barcode approach appears capable of overcoming this obstacle.

Environmental Benefits Could Be Significant

Improving plastic recycling has benefits that extend far beyond waste management.

According to researchers, recycling one ton of plastic can save approximately:

• 5.7 megawatts of electricity
• 685 gallons of oil
• 30 cubic yards of landfill space

By increasing sorting accuracy and reducing contamination, recycling facilities could recover more usable material and reduce the need for producing new plastics from raw petroleum resources.

This would support the development of a more sustainable circular economy, where materials are continuously reused rather than discarded.

Still in Development, but Showing Strong Promise

Although the technology has produced encouraging results, it is not yet ready for widespread industrial use.

The research team is currently focused on several improvements, including:

• Faster hardware capable of handling high-speed conveyor belts
• More affordable infrared light sources
• Systems that can project multiple wavelengths simultaneously
• Artificial intelligence software to speed up identification and decision-making

These upgrades will be essential before the technology can be deployed in commercial recycling facilities.

Looking Ahead

The researchers believe their invention could represent a major step forward for the recycling industry.

By providing a fast, accurate, and scalable way to identify plastics, transient thermal barcodes could help reduce landfill waste, improve recycling efficiency, and limit the environmental damage caused by plastic pollution.

Lead researcher Kunal Singh, whose work played a crucial role in developing the technology, hopes the system will eventually move beyond the laboratory and into real-world recycling operations.

“We hope to further develop the technique so that it can be transferred to industry,” Singh said.

If that happens, the future of plastic recycling may become smarter, cleaner, and far more efficient than ever before.