There are several types of rayon or viscose and they differ very much in their environmental profile. The textile is not named for its raw-material, but for its process, which is confusing for many.
To produce the yarn that is the basis for rayon or vicose, raw-material generally from wood pulp, has to go through a chemical process. The process is much like how one produces paper. Depending on what type of process, the rayon can end up as viscose, modal or lyocell, which also has the brand-name of Tencel®. If we use lycocell as an example, Tencel® produced by Austrian Lenzing uses eucalyptus from sustainable forestry, and they have a project working on sustainable forestry also for their other raw-materials. They have EU-flower classification for both Tencel® and Modal®. These are third- and second-generation viscose, and the lyocell-process is very efficient.
If the bamboo is mechanically treated it can keep its raw-material name
Another raw-material being touted as eco-friendly is bamboo. As both forests and bamboo-plantations capture CO² while they grow, one could argue that they partly neutralize their production-process and CO²-emissions. But there have been concerns about bamboo-farming and the lack of transparency within
Lyocell and modal are also textiles that one tends not to wash so often, which gives them a better eco-profile.