The development of integrated forest biorefineries is an attractive alternative for pulp and paper mills as they can increase their revenue by producing biofuels and chemicals in addition to their core products. However, the implementation of any biorefinery technology will alter the energy balance of the pulp mill. The purpose of this study was to evaluate the impact of implementing a hemicellulose extraction and conversion stage into a Canadian hardwood Kraft pulp mill on the energy supply and demand, and to identify measures for process optimization to address any increased energy requirement. An approach for energy optimization is proposed to face the energy shortage of the modified process. The approach takes into account energy efficiency measures, such as optimal use of available energy by maximized internal heat exchange, increased water system closure, improved condensate recovery and implementation of an advanced absorption cycle. The proposed measures reduce the steam demand of the Kraft process and satisfy the increased energy requirement during the implementation of a hemicellulose extraction and conversion process. This study shows that energy optimization should be an integral part of any attempt to successfully convert a conventional Kraft pulp mill into a biorefinery. (C) 2009 The Institution of Chemical Engineers. Published by Elsevier B.V All rights reserved.