PEER-REVIEWED ARTICLE bioresources.com Cao & Zhao (2015). “Biomass Fenton oxidation,” BioResources 10(3), 5949-5960. 5949 Fenton Depolymerization of Cellulosic Biomass in Modified Cuprammonium Solution Jing Hua Cao* and Joe R. Zhao This preliminary study developed a novel cellulose pretreatment method for cost-effective cellulosic utilization using a modified cuprammonium solution as a solvent to dissolve cellulose followed by molecular oxygen/Fenton depolymerization. The modified cuprammonium solution is composed of cuprammonium solution and a special catalyst that could efficiently enhance cellulosic oxygen sensitivity and therefore improve cellulosic depolymerization. The molecular oxygen depolymerization and Fenton depolymerization of cellulosic biomass dissolved in the modified cuprammonium solution were investigated. The results demonstrate that the Fenton reaction efficiently depolymerized the cellulose dissolved in the modified cuprammonium solution and reached the monomers with no loss of organic carbon, and almost all the cellulose maintained solubility without reagglomeration after cuprammonium was removed. Molecular oxygen oxidation reduced the cellulose average degree of polymerization (DP) to approximately 4 with less cost, and the oxygen pre-oxidation increased the H2O2 utilization in the Fenton depolymerization and remarkably reduced the H2O2 requirement. Keywords: Cellulosic biomass; Fenton reaction; Depolymerization; Modified cuprammonium solution; Cellulosic pretreatment; Cellulosic ethanol Contact information: Tri-Y Environmental Research Institute, 2655 Lillooet St. Vancouver, BC, Canada V5M 4P7; *Corresponding author: briancao@tri-y.com INTRODUCTION Because of concerns about the non-renewability of petroleum and pollution from petroleum energy, the exploitation of cellulosic biomass, including woody and herbaceous plants, has attracted worldwide attention. One ton of cellulosic biomass can produce about three times as much energy as one barrel of petroleum. The Earth can annually supply cellulosic biomass with an energy content equivalent to 34 to 160 billion barrels of oil, more than the world’s current consumption of 30 billion barrels of oil per year. Cellulosic biomass is the only large-scale sustainable source for producing alternative liquid fuels for vehicles. It is a potential solution to the petroleum oil problems. Recently, biofuel generation from cellulosic biomass has been focused primarily on four pathways: (1) Solidification, including biomass pellets, high-density pellets and particulates, and high-carbon charcoal; (2) Gasification of biomass to syngas, which is purified to be used or fermented into ethanol or other alcohols; (3) Liquidation of biomass by high temperature and pressure into a “crude-oil-like” product, which is distilled to different grades; and (4) Fermentation of cellulosic biomass into ethanol or other alcohols. Solidification of biomass is a simple and traditional method. The solidified biomass can be used in boilers and furnaces. During the gasification process, tar is