Sustainability: Converting vehicle waste plastics into graphene

Automotive waste plastic can be upcycled into graphene, which can be used to make new car parts, using an energy-efficient process described in Communications Engineering. The findings present a potential solution to the landfill waste from over 1.4 billion passenger cars used globally.

Plastic from end-of-life vehicles accounts for a total of more than 1 trillion kilograms of plastic waste destined for landfill, with each car containing between 200–350kg of plastic. Such materials have been difficult to recycle for a number of reasons. For example, many of these materials are engineered plastics, which cannot be recycled; and traditional recycling methods are expensive because they require the separation of different plastic types. Recent research has shown that it is possible to convert plastic waste into graphene, a valuable material (worth between US$60,000–$200,000 per ton) with useful properties, such as high electrical conductivity and high thermal and chemical stabilities. This process could be a feasible route to recycling vehicle plastic into graphene, which is sometimes an additive to some vehicle plastics to improve strength and noise absorption.

James Tour and colleagues demonstrate an energy-efficient process — called flash Joule heating — to convert used automotive plastics into high-quality graphene. The process, in which a flash of electricity heats carbon and turns it into graphene, uses low-cost infrastructure, and does not require separating or sorting of plastics, solvents, furnaces or water. The authors milled together bumpers, gaskets, carpets, mats, seating, and door casings from Ford F-150 pickup trucks to demonstrate the general process. They then used the recycled graphene to enhance new car plastics, and found a comparable performance to new graphene-containing plastic-composites produced by Ford. The authors then took that waste-derived graphene/plastic composite and re-flash Joule heated it to generate more graphene. Additionally, the authors found that flash Joule heating had lower energy demands, global warming potential and water use compared to more conventional graphene production routes.

The findings could be a step towards more environmentally friendly graphene production, the authors suggest.