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article imageEssential Science: Transforming plastic waste into fuel

By Tim Sandle     Feb 18, 2019 in Science
Researchers have developed new technology that can convert plastic waste (the biggest environmental issue associated with modern society) into a clean fuel. This represents one application to address the plastic crisis.
Scientists based at Purdue University have developed a chemical conversion process that can transform a commonly discarded type of plastic waste into clean fuels.
The primary plastic that the technology addresses is polyolefin, which is a form of polymer that represents the largest group of thermoplastics. A thermoplastic is a plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. The two most common types within this group are polyethylene and polypropylene. Polyethylene and polypropylene are very similar as far as physical properties. However, polyethylene can be produced optically clear where polypropylene can only be made translucent. Polypropylenes are also lighter in weight
Microplastics and plastic waste
These types of plastics are used as the basis of most plastic bags and plastic packaging, especially those associated with retail. The ubiquity of these plastic products has accounted for a large proportion of the plastic waste that is causing an adverse environmental impact.
Marine debris litters a beach on Laysan Island in the Hawaiian Islands National Wildlife Refuge  whe...
Marine debris litters a beach on Laysan Island in the Hawaiian Islands National Wildlife Refuge, where it washed ashore.
Susan White / US Fish and Wildlife Service (CC BY 2.0)
As an example, there is currently a global concern with microplastics. Microplastics are particles (fragments) of less than 5 millimeters in diameter. It has been estimated there are between up to fifty-one trillion individual pieces of microplastic in the world’s oceans. These have a combined weight or up to 236,000 metric tons (equal to 40,000 African Bush Elephants).
Some of the impacts of microplastics are covered in the Digital Journal article “Alarm at recovery of plastic waste in human bodies.”
New conversion process
The new process works, as Laboratory Roots reports, through the application of a selective extraction and hydrothermal liquefaction process. By engineering this, the plastic is first transformed into naphtha (a flammable liquid hydrocarbon mixture). This can then be used as the base-point for other chemicals or further separated into specialty solvents or fuels.
According to lead researcher Linda Wang: “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.”
Researchers at Sweden’s Linköping University’s Laboratory of Organic Electronics have developed...
Researchers at Sweden’s Linköping University’s Laboratory of Organic Electronics have developed an energy storage device consisting of nanocellulose and a conductive polymer.
Linköping University
And with the new process: “Our conversion technology has the potential to boost the profits of the recycling industry and shrink the world's plastic waste stock.”
The new technology has the capability to convert in excess of 90 percent of polyolefin waste into fuels, such as high-quality gasoline or diesel fuels.
The video below explains more about the plastic-to-fuel conversion process:
If developed commercially, the 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.
Research paper
The research has been published in the journal ACS Sustainable Chemistry & Engineering. The peer-reviewed paper is titled “Use of Supercritical Water for the Liquefaction of Polypropylene into Oil.”
Essential Science
Molecular structure of glyphosate.
Molecular structure of glyphosate.
This article is part of Digital Journal's regular Essential Science columns. Each week Tim Sandle explores a topical and important scientific issue. Last week we marked the 150th anniversary of the periodic table of elements, and weighed in on the discussion about how big the table might become.
The week before we looked at new medical research which has drawn a connection between climate change and an increase in the proportion of babies born with heart defects.
More about Plastic, Pollution, Fuel, Waste, Environment
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