Both leather and synthetic material undergo chemical processing in order to manufacture the material. This means that both materials do not biodegrade easily, however since leather is produced from an organic material, it has a greater capacity to biodegrade at the end of product life. As an example, Greenpeace has labelled PVC as the “single most environmentally damaging type of plastic”
The manufacturing of both materials use chemically intensive processes, and, in many cases, the finishing chemistries are nearly identical. Therefore, it cannot be assumed that synthetic materials have not used potentially damaging chemical processes. In fact, it is the control of the manufacturing process (or lack of) that causes the most environmental damage in any industry.