Recycling plastic is much harder than many people realize.
Every day, homes and businesses throw away large amounts of plastic, which is collected and sent to recycling facilities.
Before the plastic can be reused, workers and machines must sort it into different types.
This step is essential because mixing different plastics together lowers the quality of recycled materials and makes recycling less effective.
Now, scientists at the University at Buffalo have developed a new technology that could make this process much faster and more accurate. They call the system “three-dimensional transient thermal barcodes.”
The idea is somewhat similar to the barcode scanners used in supermarkets. Traditional barcode readers use light to identify products.
The new system works differently. Instead of reading printed labels, it identifies the unique molecular makeup of different plastics by creating temporary heat patterns.
The researchers shine several wavelengths of mid-infrared light onto pieces of plastic. Mid-infrared light is often called the “molecular fingerprint region” because different materials absorb this light in their own distinctive ways.
When plastic absorbs the light, the molecules inside it begin to vibrate. These vibrations create tiny amounts of heat.
A special thermal camera then captures these temporary heat patterns. Each type of plastic produces its own unique heat signature, or thermal barcode. By reading these thermal barcodes, the system can quickly determine what kind of plastic it is examining.
The team successfully used the method to identify six common types of plastic: polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polyvinyl chloride (PVC). Importantly, the technology can also identify black plastics, which are particularly difficult for many existing recycling systems to detect.
Current sorting methods often have major limitations. Some technologies struggle to accurately distinguish between plastics, work too slowly, or cannot identify certain materials from a distance.
In many facilities, some sorting is still done by hand, which can lead to mistakes and contamination.
Improving plastic sorting could have significant environmental benefits. According to the researchers, recycling one ton of plastic can save about 5.7 megawatts of electricity, 685 gallons of oil, and around 30 cubic yards of landfill space.
Better sorting could therefore increase recycling rates and reduce the amount of plastic ending up in landfills and the environment.
The technology is still in the early stages and is not yet ready for use in recycling plants. The research team is now working to make the system faster and less expensive. They are developing improved hardware, more affordable light sources, and artificial intelligence software that can quickly interpret the thermal barcodes.
Although more work remains, the study shows that transient thermal barcodes have real potential. One day, this innovative technology could help recycling facilities recover more plastic, reduce waste, and move society closer to a true circular economy where materials are reused instead of discarded.
Source: University at Buffalo.
