Wood is composed of about 70% polysaccharides (a combination of cellulose and hemicellu lose, which is used to make paper) and 30% lignin (which acts as a "glue" to hold the polysaccharide fibers together) In making paper, most of the lignin must be removed, because its presence in paper creates a brown discoloration 12 In addition, significant quantities of lignin in paper that is initially white can cause the paper to "yellow" over time. Almost 80% of the world's paper mills rely on a Kraft process to remove lignin from the raw wood starting material. In this process, logs are chipped into smaller pieces and then placed in a bath of sodium hydroxide and sodium sulfide, which results in depolymerization of the lignin (Figure 1). As the lignin breaks down, the wood chips lose their rigidity, and a slurrylike solution of polysaccharides is formed (pulp).