The oxidative pretreatment involves the use of a strong oxidizing reagent such as hydrogen peroxide to achieve delignification. Sometimes sodium silicate of magnesium sulfate is added with hydrogen peroxide to make the solution more stable (Guald 1984). The concentration of hydrogen peroxide used is in the range of 1-10% by volume. More precisely, effective pretreatment requires the ratio of hydrogen peroxide to substrate of at least 0.25 g H2O2/g substrate under alkaline conditions (Guald 1984).

In alkaline conditions, hydrogen peroxide decomposes to form hydroxyl ions that further react with phenolic groups of lignin. Hydrogen peroxide also plays an important role in stabilizing the ends of cellulose and hemicellulose structures (Gupta 2008). Guald (1984) mentioned that alkaline peroxide pretreatment can achieve 50% or more delignification of lignocellulosic biomass with greater than 90% overall theoretical saccharification efficiency. However, the degree of saccharification for oak was 52.5% compared to 93.0% for wheat straw (Guald 1984).