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February
12
2019

Chemical conversion process gives plastic waste new life as fuel
Wolf Richter

Chemical engineer Linda Wang (right) led a research team at Purdue University in coming up with a new way to convert a common plastic into oil, opening up some exciting possibilities(Credit: Purdue Research Foundation image/Vincent Walter)

The United Nations estimates that more than 8 million tons of plastics flow into the oceans each year. A new chemical conversion process could transform the world’s polyolefin waste, a form of plastic, into useful products, such as clean fuels and other items.

Millions of metric tons of plastic are produced each year and in reality, very little of it is recycled. But what if there were more ways of turning this waste into something valuable, such as new plastics or different types of fuel? Scientists at Purdue University have taken a promising step towards this goal with a new technology that can turn the majority of a commonly used plastic into the building blocks for all kinds of materials, something they hope can inspire new solutions for our plastic pollution problem. 

Estimates vary on how much plastic winds up in landfill, how much ends up being recycled and how much washes into the ocean, but there's no question plastic waste is a big problem. As an indication, a 2015 paper estimated that somewhere between 5 and 12.7 million metric tons of plastic waste winds up in the ocean each year, and what happens to it from there is a great unknown.

The solution to this problem is far more complex than finding new ways of recycling the ubiquitous material, but it is certainly a step in the right direction. Elsewhere, we have seen promising experimental technologies that can convert plastic bags into high-value carbon nanotubes, turn ocean plastics into usable diesel fuels and turn plastic bottles into other fuels and waxes. 

The work at Purdue University focuses on a type of plastic called polyolefin, the most common type of thermoplastic that features in everything from bottle caps to scientific instruments. 

"Our strategy is to create a driving force for recycling by converting polyolefin waste into a wide range of valuable products, including polymers, naphtha (a mixture of hydrocarbons), or clean fuels," says Linda Wang, chemistry professor at Purdue University and leader of the research team. "Our conversion technology has the potential to boost the profits of the recycling industry and shrink the world's plastic waste stock."

In pursuing this strategy, Wang and her team turned to a technique called hydrothermal liquefaction, a process of heating materials up to moderate temperatures under high pressure to convert them into oil. In this case, the team was able to transform 91 percent of the polyolefin into oil consisting of paraffins, cyclics, aromatics and olefins, unsaturated hydrocarbons that serve as the foundation for polyolefins.

And that opens up a range of possibilities, according to the scientists. This oil and its ingredients can then be turned into gasoline blendstocks and feedstocks for other chemicals. They can also be separated into specialty solvents or fuels such as gasoline or diesel. So much so, the team estimates that the fuels generated from discarded polyolefin could meet around four percent of the globe's demand for gasoline and diesel fuels each year.

To that end, the researchers have now teamed up with Purdue University's Fuel Laboratory of Renewable Energy to try and optimize the conversion process. They are also looking for partners to help demonstrate the technology's potential on a commercial scale. 

You can hear more from Wang in the video below, while the research was published in the journal ACS Sustainable Chemistry and Engineering.

Source: Purdue University

 

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