The team first uses an iridium-rich compound, which removes the hydrogen atoms from PE. The carbon atoms left behind begin forming double bonds with each other, which are more reactive to certain chemicals than the original single bonds.
The second catalyst, which contains a mixture of aluminum, oxygen, and rhenium, attacks this new vulnerability, and smashes the polymer apart. After this, the liberated hydrogen atoms are once again re-imprisoned back onto the fragmented polymer segments (“monomers”).
The end result of this concoction of chemical wizardry is to turn the original PE object – which in this case included a plastic bag, a bottle, and food packaging – into a fuel. Changing the amount of hydrogens and carbons on a hydrocarbon polymer literally transforms it into a completely different chemical, and this is precisely what this team has managed to achieve without using much heat, and therefore energy, in doing so.
A mixture of hydrocarbon monomers, here represented depressingly by oil pollution in the sea. huyangshu/Shutterstock
Changing the speed of the reaction, or the degree of initial catalytic fragmentation, allows the team to choose whether they want a liquid fuel to emerge at the end, or, alternatively, a type of wax. This process seems to produce relatively clean, low-pollution fuels, with respect to other fossil fuels. Not investing energy into excavating fossil fuels is also a good thing, environmentally speaking.
Hopefully, though, this doesn’t become the go-to future method for producing energy. Recycling plastic to be used as a fuel is a good idea, but really, we should be focusing on energy sources that have a low-to-zero carbon footprint, like renewables, and nuclear. Above all, we should stop wasting so much plastic in the first place.