Energy efficiency measures in a kraft pulp mill converted to a biorefinery producing ethanol

Licentiatavhandling, 2010

Large scale, sustainable production of ethanol biofuel will most likely require commercialization of processes using lignocellulosic raw materials. To date no commercial plant exists however, due to the difficulties in reaching production costs that can compete with 1st generation ethanol and fossil fuels. One way of possibly decreasing the production cost is using an unprofitable pulp mill that is converted to ethanol production. The economic benefits of this would be e.g., that existing equipment and infrastructure could be used and that a skilled workforce would be available. These synergetic effects could be important for taking the leap into 2nd generation biofuel production. The objective of the work presented in this thesis has been to analyze a conceptual converted pulp mill ethanol plant with respect to energy efficiency measures and to try and draw some conclusions on the importance of implementation of measures, as well as the profitability of doing so. Furthermore, the ethanol process has been compared in brief with other 2nd generation ethanol processes. Implemented energy efficiency measures have been assessed economically by assuming that steam savings will be turned into increased output of energy in the form of lignin biofuel or electricity. Conclusions that can be drawn from this study are that implementing energy efficiency measures should be considered when converting the pulp mill to ethanol production and that the choice between lignin and electricity as a byproduct is difficult to make. Electricity is a more robust choice with the inputs used in this study but lignin might give higher added value. It is very difficult to assess lignin though, due to the multitude of different uses this product could have in the future.