WSU researchers turn plastic bags and bottles into jet fuel

Melted down bottles and shopping bags could one day power jet planes after researchers successfully converted plastic rubbish into usable fuel.

Landfills in the US received 23.6m tonnes of plastic in 2015, said the team from Washington State University (WSU), while they cited “conservative” estimates of at least 4.4m tonnes of plastic entering the oceans every year.

Hanwu Lei and colleagues at WSU hope to convert that waste into fuel to extract energy from the plastic. The researchers ground low-density polyethylene and a mixture of plastic products including water bottles, milk bottles and plastic bags into rice grain-sized pieces, about 3mm. They then placed the granules in a tube reactor on top of activated carbon, a catalyst with an increased surface area, and heated it to 430-571ºC.

The catalyst broke down chemical bonds in the plastic. The two were then separated, letting the team reuse the catalyst. The best yield was a mixture of 85% jet fuel and 15% diesel, the researchers said.

The announcement of the research did not include assessment of whether burning recycled plastic is better for the environment than putting it into landfill, but Lei told Professional Engineering: "I believe burning jet fuel is better for the environment than putting plastic into landfill or entering the water. The jet fuel produced from waste plastic is pretty clean due to the low sulphur content of plastics. Burning such jet fuel just gives CO₂ and H2O. Many developing countries currently use diesel with relatively high sulphur content."

Plastic-generated jet fuel – which ultimately comes from fossil fuels – could replace a portion of fossil fuels used to power jets, ultimately not increasing the CO₂ emissions rate according to Lei. 

"A large percentage of waste plastic is currently discarded since it cannot be recovered," said Lei. "The waste plastics in the landfill or incinerated result in a serious danger towards the natural environment, human health, and even lives from plankton to whales in oceans and waterways, which brings severe impacts on the ecosystem and economy.

"A new study in Science indicated the horrifying numbers – in 2010, the study found between 4.8m-12.7m tonnes of plastic entered the oceans. Plastic pollution has an incalculably lethal effect on everything from plankton to whales."

The process of pyrolysis is easily scalable, said biological system engineer Lei. It could be installed in large facilities or even farms, he said. “Waste plastic is a huge problem worldwide… this is a very good, and relatively simple, way to recycle these plastics.”