Limited case study of biorefinery implementation in paper industry has been done through the investigation of fibers component separation from hydropulper reject for papermaking. Pulper rejects was cleaned from metal contaminant, crushing, screening sequentially through the screen 6, 2, and 1size, and drying. Reject fibers (R) then mixed with Old Corrugated Container or OCC (O) in the ratio of R:O as 100:0; 75:25; 50:50; 25:75; and 0:100. The handsheets then made at the basis weight of 70, 125, and 150 g/m2 or GSM, followed by testing and evaluating. The results showed that the furnish of reject and OCC mixing is feasible for papermaking, and still have some opportunities to develope further mechanically, chemically, and or fiber reinforcement. Based on the evaluation of handsheets quality, it
is recommended that improved 70 GSM paper suitable for wrapping paper, while improved 125 and 150 GSM papers supposed to be a lainer board and fluting medium.