Rayon is a generalised term for all manufactured fibres made from regenerated cellulose. It was originally developed as a cheaper substitute for silk and is also often used as an alternative of cotton or polyester. There are different types of rayon fibres, including viscose, acetate, lyocell and modal.
Although semi-synthetic fibres are made of renewable natural resources and are biodegradable, most of them are not considered very environmentally friendly due to their heavily polluting manufacturing process. Other concerns include causing deforestation, when woods are not sourced from environmentally responsible suppliers and are not sustainably harvested. However, still, they are considered more sustainable than conventional synthetic fibres.