Do you know that it needs atleast 12 trees to create a 100 percent non recycled newsprint. And that is just to create a paper, what more in creating a fiat? But if people will use digital currency, no one need to haded over those bills and a single scan in a qr code or tap in a terminal will automatically send your payment. There is also no need to recycle or re create new money because digital currency is intangible and indestructible. The only environmental effect that it bring are the carbon oxide produced by the electric company which powered the mobile phone of bitcoin users.