If Recycling Plastics Isn't Making Sense, Remake the Plastics
Freeman writes:
https://arstechnica.com/science/2020/10/if-recycling-plastics-isnt-making-sense-remake-the-plastics/
A few years back, it looked like plastic recycling was set to become a key part of a sustainable future. Then, the price of fossil fuels plunged, making it cheaper to manufacture new plastics. Then China essentially stopped importing recycled plastics for use in manufacturing. With that, the bottom dropped out of plastic recycling, and the best thing you could say for most plastics is that they sequestered the carbon they were made of.
[...] The first paper, done by an international collaboration, actually obtained the plastics it tested from a supermarket chain, so we know it works on relevant materials. The upcycling it describes also has the advantage of working with very cheap, iron-based catalysts.
[...] Compared to traditional heating, the microwave heating released over 10 times as much hydrogen from the plastic, leaving very little other than pure carbon and some iron carbide behind. Better yet, the carbon was almost entirely in the form of carbon nanotubes, a product with significant value.
[...] The utility of this is that, by adjusting the average length of the population that comes out of the reaction, it's possible to produce mixtures of hydrocarbons that will work better as fuel, or as lubricants. In other words, you can turn polyethylene into whatever type of hydrocarbon mixture that's most valuable at the time.
Overall, however, there are more significant drawbacks here. Platinum, used in the catalyst, is quite expensive, and it only works on a single type of plastic-although other catalysts might be amenable to being placed at the end of pores. The reactions have to be run at an elevated temperature, and it requires a supply of hydrogen to work. So, it's substantially less flexible than the one run by microwaved iron. But the ability to turn any plastics into liquid fuel certainly has potential utility.
Journal References:
(1) Xiangyu Jie, Weisong Li, Daniel Slocombe, et al. Microwave-initiated catalytic deconstruction of plastic waste into hydrogen and high-value carbons, Nature Catalysis (DOI: 10.1038/s41929-020-00518-5)
(2) Akalanka Tennakoon, Xun Wu, Alexander L. Paterson, et al. Catalytic upcycling of high-density polyethylene via a processive mechanism, Nature Catalysis (DOI: 10.1038/s41929-020-00519-4)
Read more of this story at SoylentNews.