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With millions of tons of plastic ending up in landfills and oceans each year, there is a massive ecological need to improve recycling efforts.
New recycling methods are designed to increase the amount of plastic waste that can be effectively recycled, either by creating new plastics that are more recycle-friendly or discovering new ways to recycle more effectively.
There are three major issues when it comes to improving plastics recycling. First, plastics must be sorted by type, as different kinds don't mix well when liquified. Second, chemical recycling makes use of a catalyst that break down long-chain plastic molecules into smaller-chain products, a system plagued by high energy costs. Third, plastic recycling mainly involves two types of materials, polyethylene terephthalate (PET), which is found in most water bottles, and polyethylene, one of the most common plastics. This is because many commercial polymers can't be processed with high temperatures.
These challenges are being met, and there are currently a number of machines currently taking plastic recycling to the next level. New methods include processes to recycle more kinds of plastics together in one waste stream, avoiding the costly but necessary sorting of plastics and ways to recycle plastics in a more efficient manner.
Better Sorting Through Spectral Imaging
A lot of plastics include flame-retardant chemicals and the amount of flame retardant used in various plastics ranges significantly, based on application and regulatory standards.
Unfortunately, only plastics with similar types and amounts a flame retardant can be recycled in the same waste stream. Hence, plastics must be sorted before any chemical processes can occur.
According to a recent study, researchers have been able to use near-infrared hyperspectral imaging and complex algorithms to more efficiently sort different types of plastic with differing levels of flame retardant.
The imaging technique is essential for this recycling process because it can recognize specific pieces of plastic and the flame retardant as they pass on a conveyor belt in a recycling facility.
The study team said their sorting process used an analytics process called chemometrics along with the spectral imaging information to differentiate among various plastics with 100 percent accuracy.
Reverse-Engineering Plastic Waste
‘Thermal cracking’ is a technique that involves heating large non-volatile molecules to break them down into smaller molecules, and one UK-based start-up is using the process to essentially convert plastic waste back into range raw materials that can find new uses.
The RT7000 machine by Recycling Technologies pre-treats and breaks down plastic waste, removing biomass, moisture and inert materials. The machine’s first module is a thermal cracker that breaks up the long-chain molecules in waste plastic and removes unwanted chemicals to produce a light hydrocarbon gas. Subsequent modules condense this gas into a proprietary raw material called ‘Plaxx’ – of which there are a number of different varieties. For instance, ‘Plaxx-50’ can be used as a wax for packaging and cosmetics, while ‘Plaxx-30’ can be used as engine fuel.
Recycling Plastic Bags with Organic Chemistry
A California-based start-up called BioCellection has developed a system that is capable of creating useful raw materials from polyethylene plastics such as LDPE and HDPE, which are commonly used in packaging and plastic bags. The BioCellection system uses machinery to facilitate a complex organic chemistry process.
The system begins by shredding waste plastics into tiny bits. A dual-catalyst system transforms the long-chain polymers from shredded plastic into shorter-chain molecules like dibasic acids. Products of this process are recovered via filtration. The dibasic acids are then crystallized and extracted to yield a powder product. Specially-engineered bacteria break down this powder and secrete a compound that can act as a petroleum-product replacement for new plastic products.
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