o-CNT would be biodegradable.

Ironically, it looks like you have to add oxygen back to that to make it worth money:

Public link: Commercial Methane Pyrolysis Overview https://gemini.google.com/share/918e7883df8a :

> Because the economic model of pyrolysis requires selling the solid carbon byproduct, local carbon black prices dictate profitability

; per/kg:

> Carbon Black: $1.20 - $1.80

> o-CNTs: $150 - $300+