Process integration techniques have been applied to study a bisulfite mill which produces pulp and three additional by- products: bioethanol, lignosulfonate and yeast. Particular attention was devoted to the integration of the chemical recycling loops which have a significant impact on the process energy balances and therefore influence the choice of biorefinery integration strategies. This analysis illustrates the trade-off between conversion of materials and of energy and shows the importance of considering simultaneously the heat recovery through heat exchangers and the combined heat and power production.