Plastic bags are a scourge on the environment. Millions upon millions of them are used daily only to be dumped after a single use. Vast amounts of these bags end up in landfills, as litter or as floating pieces of debris in the oceans where they can take centuries to decompose.

“But what if used plastic bags could be made into higher-value products?” a team of researcher wondered … and decided to act on it.

The scientists have devised a new method for converting plastic bags into carbon chips that serve as anodes in lithium-ion batteries. It has long been known that “the polyethylene in plastic bags could be an inexpensive source of energy-storing carbon,” they note. “However, previous methods to upcycle polyethylene into pure carbon have been inefficient or required expensive, complex processes.”

A newly devised simpler approach, however, can convert plastic waste into useful carbon-containing materials. During the process polyethylene plastic bags are immersed in sulfuric acid and sealed inside a solvothermal reactor where they are heated until the polyethylene in them almost begins to melt.

“This treatment caused sulfonic acid groups to be added to the polyethylene carbon-carbon backbone so that the plastic could be heated to a much higher temperature without vaporizing into hazardous gases,” the researchers explain. “Then, [the researchers] removed the sulfonated polyethylene from the reactor and heated it in a furnace in an inert atmosphere to produce pure carbon. The team ground the carbon into a black powder and used it to make anodes for lithium-ion batteries.”

The batteries thus produced performed well when compared with commercial batteries, which means that the process could be applied commercially. Meanwhile, other teams of scientists are working on other ways to turn various pieces of plastic waste into useful products, such as clean fuels.

The idea is that by using discarded plastic bags as valuable raw materials for useful products, we can incentivize the collection and recycling of plastic waste on a large scale.