plastic waste dump

Plastic bottles turned into jet fuel could help global waste problem

Image credit: DT

Plastic waste has been transformed into jet fuel with a newly developed process from Washington State University scientists.

The plastic waste was melted at a high temperature with activated carbon - a processed carbon with increased surface area - to produce jet fuel.

“Waste plastic is a huge problem worldwide,” said Hanwu Lei (pictured below), an associate professor in WSU’s Department of Biological System Engineering. “This is a very good, and relatively simple, way to recycle these plastics.”

In the experiment, Lei and colleagues tested low-density polyethylene and mixed a variety of waste plastic products - such as water bottles, milk bottles and plastic bags - and ground them down to beads of around three millimetres, approximately the size of a grain of rice.

The plastic granules were then placed on top of activated carbon in a tube reactor at a high temperature, ranging from 430°C to 571°C.

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The carbon acts as a catalyst, or a substance that speeds up a chemical reaction without being consumed by the reaction.

“Plastic is hard to break down,” Lei said. “You have to add a catalyst to help break the chemical bonds. There is a lot of hydrogen in plastics, which is a key component in fuel.”

Once the carbon catalyst has done its work, it can be separated out and re-used on the next batch of waste plastic conversion. The catalyst can also be regenerated after losing its activity.

After testing several different catalysts at different temperatures, the best result was a combination of 85 per cent jet fuel and 15 per cent diesel fuel.

According to the Environmental Protection Agency (EPA), landfills in the US received 26 million tons of plastic in 2015, the most recent year for which statistics are available.

Meanwhile, China recently stopped accepting plastic recycling from the US and Canada to stem the tide of hazardous “foreign garbage”.

Conservative estimates by scientists say that at least 4.8 million tons of plastic enters the ocean each year worldwide. Not only would this new process reduce that waste, very little of what is produced is wasted.

“We can recover almost 100 per cent of the energy from the plastic we tested,” Lei said. “The fuel is very good quality and the byproduct gasses produced are high quality and useful as well.”

He also said the method for this process is easily scalable. It could work at a large facility or even on farms, where farmers could turn plastic waste into diesel.

“You have to separate the resulting product to get jet fuel,” Lei said. “If you don’t separate it, then it’s all diesel fuel.”

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