New Chemical Process Can Convert Nearly a Quarter of All Plastic Waste Into Fuel (vice.com)

"Researchers at Purdue University have developed a new chemical process that they say can convert approximately one-quarter of the world's plastic waste into gasoline and diesel-like fuels," writes Slashdot reader dmoberhaus. Motherboard explains how it works: As detailed in a paper published this week in Sustainable Chemistry and Engineering, the chemists discovered a way to convert polypropylene -- a type of plastic commonly used in toys, medical devices, and product packaging like potato chip bags -- into gasoline and diesel-like fuel. The researchers said that this fuel is pure enough to be used as blendstock, a main component of fuel used in motorized vehicles. Polypropylene waste accounts for just under a quarter of the estimated 5 billion tons of plastic that have amassed in the world's landfills in the last 50 years.

To turn polypropylene into fuel, the researchers used supercritical water, a phase of water that demonstrates characteristics of both a liquid and a gas depending on the pressure and temperature conditions. Purdue chemist Linda Wang and her colleagues heated water to between 716 and 932 degrees Fahrenheit at pressures approximately 2300 times greater than the atmospheric pressure at sea level. When purified polypropylene waste was added to the supercritical water, it was converted into oil within in a few hours, depending on the temperature. At around 850 degrees Fahrenheit, the conversion time was lowered to under an hour. The byproducts of this process include gasoline and diesel-like oils. According to the researchers, their conversion process could be used to convert roughly 90 percent of the world's polypropylene waste each year into fuel.

Comments

So...

[Freischutz]

So, they have discovered a method to convert millions of tons of plastic into fossil fuels that can be burned to release yet more sequestered carbon into the atmosphere. That's sure to solve our ongoing problem with carbon emissions causing climate change.

That's not the problem

[Solandri]

There are two classes of plastic trash.

• Plastic thrown away in trash cans and as household garbage. These plastics end up in a landfill, meaning it's buried underground. Which happens to be where the petroleum to make the plastic originally came from. So it has zero net environmental impact (unless you plan to go digging up landfills).
• Plastic thrown away on the streets, in the landscape, and in the water. These plastics mar the environment and cause all the problems we're hearing about (plastic in the oceans, microplastics in the food chain, animals being wrapped up and dying in plastic waste).

Now, if they're going to convert plastic into fuel, which plastic do you think they're going to use? Obviously the former. Meaning (1) it will have zero effect on plastic pollution in the environment, and (2) you're just spending extra energy and money to convert petroleum byproducts into fuel, instead of just using new petroleum as fuel. You're just paying extra to swap carbon sequestered underground as plastics, for carbon sequestered underground as natural petroleum.

Any solution to address environmental plastic pollution must address the non-collection problem. That means either enforcing proper disposal of plastic waste, designing plastic waste to degrade more quickly in the environment, or reducing the use of plastics entirely. This plastic to fuel idea does none of these things. The only thing it does is reduce the space taken up in landfills.