“Upcycling” is the big idea today in green circles. It’s the concept of turning waste material into something more useful than it was in its first incarnation.
Well, a scientist at Argonne National Laboratories (ANL) in Illinois is giving whole new meaning to the concept. Researcher Vilas G. Pol is converting plastics bags into multiwalled carbon nanotubes that power lithium ion batteries. Pol bakes pieces of polyethylene bags at 700C for two hours with a cobalt acetate catalyst. The polymeric bonds disintegrate at 600C and the carbon migrates to the surface of the cobalt particles. Oxides don’t form, according to Pol. “I have used the as-prepared cobalt-encapsulated nanotubes as an anode material for lithium-ion batteries and they work fantastically,” Pol says in news reports. “The specific capacity of my carbon nanotubes is higher than commercial nanotubes.”
The carbon particles from a single plastic bag create enough nanotubes to power a cell phone. The cobalt acetate is expensive but could theoretically be recovered when the batteries are recycled. Pol says the process has commercial value even if the cobalt catalyst isn’t used. The process can still be used to grow carbon spheres with numerous applications. “Generally carbon is produced from petroleum products, we can save that, use this waste polymer feedstock,” Pol says.
Referring to his process, Pol says: “It has a great significance. If you want to just get rid of plastic waste, this is the way to do it. All other recycling processes have limitations since chemically different polymers can not be mixed together. Thus the final product will not be that high quality.”
Will the technology transfer to a much larger scale? ANL is seeking a licensee for it.
One of the biggest issues may be recovering plastic bags from the waste stream. They currently aren’t recycled. If the economics of Pol’s process are real, other types of plastics may be used. A ton of waste plastic bags may contain contaminant and may be more expensive than fresh-made plastics.
Another issue is that major companies such as Bayer and Nanocyl are opening production-size factories to make carbon nanotubes. Costs are dropping dramatically.
Dr. Pol tells Design News: “I strongly believe that this technology is scalable. The economics of the process will depend on how big a facility we plan to build. (From a) carbon nanotubes’ point of view, all the other methods are energy intensive too. Additionally, we do not use additional flue gases or vacuum environment, which is used by other methods, thus our tech should not be very expensive.”