I don't want to be a downer on this because it sounds like a cool system, but it might be worth checking whats in the receipt paper as a lot of it is pretty bad for you:
https://toxicfreefuture.org/press-room/new-study-finds-toxic...
https://toxicfreefuture.org/press-room/new-study-finds-toxic...
Even assuming that "BPA-free" paper I'd buy is really so, and not just BPA-covered one imported from China and said/labeled to be "BPA-free" by someone somewhere in the pipeline...
However, none of them say what their actual 'active ingredient' is and I am curious if these are necessarily known to be better. Most of them describe themselves as 'plastic coated'.