The waste product of plants used in the conversion of hide to leather is

Explanation

Tannin is an acidic chemical compound that comes from tree bark. It's used in the process of tanning, which is the final step in turning animal skins into leather. Tannin is used to convert hides into leather. Historically, vegetable based tanning used tannin, an acidic chemical compound derived from the bark of certain trees, in the production of leather.