A two-stage optimization approach for the synthesis of an integrated pulp and paper biorefinery

Pulp and paper mills (PPMs) generate large amount of wastewater with high chemical oxygen demand (COD) concentration. Recently, anaerobic digestion receives much attention for the treatment of PPM wastewater. Through anaerobic digestion treatment, biogas can be generated and converted to bioenergy via combined heat and power (CHP). However, there are limited studies on the systematic allocation of bioenergy from CHP to wastewater treatment (WWT) and PPM to form an integrated pulp and paper biorefinery (IPPB). Therefore, the current work explores the potential of energy integration in an IPPB through a two-stage optimization approach. In the first stage, an optimal cost effective WWT for the treatment of PPM wastewater is synthesized. Next, the generated biogas from WWT is converted into four different forms of bioenergy. The detail allocation of the generated bioenergy is then determined in the second stage optimization. A case study is solved to illustrate the proposed approach.