Mechanical pulp, being high in lignin content, is usually brightened by using hydrogen peroxide. This alters the chemical structure of the lignin, lightening its color but leaving it present in the pulp. Lignin-removing chemicals, such as chlorine are not used because this would result in a large reduction in yield.
Hydrogen peroxide has long been used for bleaching mechanical pulp and de-inking waste paper. With the patented Lignox method developed by Eka Chemicals, hydrogen peroxide can remove much of the lignin from the pulp and is today the basis of TCF bleaching.
Hydrogen peroxide is manufactured from oxygen, and extracted from air and hydrogen in a closed process. Hydrogen is obtained as a by-product of, for example, chlorate production, or by the decomposition of natural gas. The effect of hydrogen peroxide on the environment is negligible. Its products of decomposition are oxygen, gas and water.