A significant fraction of short fibers (fines) is produced while recycling Old Corrugated Containerboards (OCC), which are usually rejected as solid waste stream, requiring landfilling and posing environmental problems. The major component of these fines rejects are primarily cellulose that can be hydrolyzed into sugars for possible fermentation into biofuels, bioplastics or other sugar based products. Use of fines also offers benefits such as negative costs and production of fermentable sugars without requiring complex pretreatment processes, now required to hydrolyze and eliminate inhibitors from hydrolyzate. Enzymatic hydrolysis of reject fines from a recycled OCC mill, employing different strains of cellulases, were investigated. Fillers (up to 30 mass %) in the fines increases the required dosage of enzymes and costs. Enzyme loading can be lowered by addition of surfactants to reduce their inhibitory activity. The nonionic surfactant Triton X-80 improved hydrolysis yields by up to 10 percent points.