A by-product is a by-product of a manufacturing process, which is not a product or a residue. It is intentional and unavoidable and is obtained at the same time as the main product.

A by-product can be of plant, mineral or other origin and can be reused for example in the plastics industry as a filler or even as a main component of a mixture.

The addition of by-products to plastics or bioplastics aims to improve the environmental footprint, while providing immediate new functionality and product differentiation.