Offset / UV Printing is the greenest option available today in the printing segment. While offset is a  widely used commercial large scale printing technique that produces consistent and high quality printed materials, UV  is the process where inks dry through a photomechanical process getting  exposed to ultra-violet lights as they are printed, immediately turning from a liquid to a solid with very little evaporation of solvents and almost no absorption of ink into the paper stock. You can print on virtually whatever you want when using UV inks!