Scientists in the US and China say they have developed a one-step method to safely turn toxic mixed plastic waste into petrol, with more than 95 per cent efficiency at room temperature.
Compared to conventional ways of turning plastic into fuel, their process requires less energy, less equipment and fewer steps, making it scalable for industrial applications.
At the end of this conversion process are the main components of petrol or gasoline, chemical raw materials, and hydrochloric acid. That means the end product could be used for water treatment, metal processing, pharmaceuticals, food production or the petroleum industry.
“The method supports a circular economy by converting diverse plastic waste into valuable products in a single step,” the researchers wrote in a paper published in the peer-reviewed journal Science on August 14.
The team comprises researchers from the US Department of Energy-funded Pacific Northwest National Laboratory, Columbia University, the Technical University of Munich, and East China Normal University (ECNU).
This is the first time that difficult-to-degrade mixed plastic waste has been efficiently converted into premium petrol at ambient temperature and pressure in just one step, according to a social media post by ECNU on August 18.
Japan’s researchers develop ocean-friendly plastic
These plastics are used in all kinds of items – from packaging and containers to pipes, household appliances, medical devices and clothing.
Global cumulative plastic production has now reached 10 billion tonnes, and most of it is doomed to become hard-to-recycle waste, according to ECNU. PVC is produced using vinyl chloride, a colourless gas that is classed as a carcinogen by the US Environmental Protection Agency. This means that traditional plastic waste-to-energy methods, including incineration, require PVC to be dechlorinated before processing to prevent the release of toxic compounds.
Chemical upcycling methods – which aim to chemically break down the plastic into high-grade chemical components – also require high-temperature dechlorination.
This multi-step process has reduced efficiency and requires high energy consumption, highlighting the need for a simpler process that couples dechlorination together with the other steps.
“We present here a strategy for upgrading discarded PVC into chlorine-free fuel range hydrocarbons and [hydrochloric acid] in a single-stage process,” the researchers said in the paper.
To achieve this, the team combined plastic waste with light isoalkanes, a type of hydrocarbon or organic compound that is available as a byproduct from refinery processes.
The team said their process produced “gasoline range” hydrocarbons, mainly molecules with 6 to 12 carbons, which are the primary component of gasoline.
The recovered hydrochloric acid can be safely neutralised and reused as a raw material in many modern industries, according to the paper. Current hydrochloric acid production relies on several high-temperature, energy-intensive processes.
Plastic-eating superworms with ‘recycling plant’ in their guts might get a job gobbling up waste
Conversion efficiency of the plastic at 30 degrees Celsius (86 degrees Fahrenheit) reached 95 per cent for soft PVC pipes, and 99 per cent for rigid PVC pipes and PVC wires.
The team also tested the conversion of a mixture of PVC materials along with polyolefin waste and found that the solid conversion efficiency was 96 per cent at 80 degrees Celsius (176 degrees Fahrenheit).
“The process is suitable for handling real-world mixed and contaminated PVC and polyolefin waste streams,” the researchers said.
Source : https://www.scmp.com/news/china/science/article/3323139/first-us-china-team-turns-plastic-waste-petrol-one-step
