Commonly used to make a wide variety of items, low-density polyethylene can be recycled into new plastic, but there's much more waste than recycling facilities can currently handle. With that in mind, scientists have now devised a method of converting the material into something else – jet fuel.
Led by Assoc. Prof. Hanwu Lei, a team at Washington State University started with low-density polyethylene waste obtained from sources such as plastic bags, milk cartons and water bottles. They then ground that plastic into granules measuring approximately 3 mm across, or approximately the size of a grain of rice.
Those granules were then placed inside of what's known as a tube reactor, on top of a bed of activated carbon. The plastic and carbon were subsequently heated to a range of 430 to 571 ºC (806 to 1,060 ºF), resulting in a thermal decomposition process called pyrolysis. With the carbon acting as a catalyst, this caused the plastic to break down and release its stored hydrogen content.
After testing seven different types of activated carbon, the team was ultimately able to obtain a mix of 85 percent jet fuel and 15 percent diesel fuel from the plastic. Those fuels can be separated from one another, plus the carbon can also be separated for subsequent reuse, and can be reactivated once it starts losing its catalytic effect.
Overall, it's claimed to be a very efficient process, and it could reportedly be scaled up to industrial levels with little problem.
"We can recover almost 100 percent of the energy from the plastic we tested," says Lei. "The fuel is very good quality, and the byproduct gasses produced are high quality and useful as well."
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