Using xylanase enzymes to remove lignin from kraft pulp reduces the amount of chlorine needed for bleaching, which decreases toxic byproducts in the effluent. The size of the xylanase molecules and the structure of the pulp pores determine how much lignin can be removed. Xylanases with larger molecular sizes remove less lignin. Treating softwood pulp with xylanase and mild cellulase increased pore size, allowing for more efficient lignin removal and reducing chlorine requirements by 31%. For hardwood pulp, this process eliminated 41.8% of the required chlorine for bleaching.