Oxalate is an organic compound that contains a central atom or group of atoms known as an oxalyl (C2O4) group. These compounds are formed by the combination of two molecules of carbon dioxide (CO2). Oxalates occur naturally in many plants, and they can also be produced synthetically for various industrial applications. In biological systems, oxalate ions play a role in plant metabolism and can interfere with mineral absorption in humans when present in excessive amounts.