Simulating the integration of lignocellulosic ethanol into first generation plants
The strong global dependence on fossil fuels results from the intensive use and consumption of petroleum based derivatives. With regard to the risks of diminishing petroleum reserves and growing climate change, there is need for an ecological and political acting. A promising approach is the change-over from a fossil-based chemistry to a bio-based in order to ensure the sustainable supply with basic chemicals and energy. Implementing sustainable biorefinery concepts is thereby seen as a path with great prospects. Due to the multitude of possible raw materials, products, conversion pathways and combinations of technologies, the development and related optimization of sustainable biorefinery concepts turns out to be a major challenge. In the context of sustainability this is especially true for economic and environmental criteria. For this reason it is necessary to provide the process engineers with a robust assessment methodology already during the conceptual design of biorefineries. Process simulation is a very powerful tool for the calculation of mass and energy balances of integrated flowsheets. Its application is especially well-suited during conceptual design. It allows the development and comparison of different flowsheets already at an early stage of process design. Details can be added to the flowsheets as soon as they become available in the course of the project development. On the other hand the different methodologies for sustainability assessment of a conceptual production site are based on inventory data of the needed material and energy input. For the assessment of running facilities, these can be taken from actual in and output balances. During conceptual design, the data can be effectively estimated by process simulation. A methodology on how to integrate the process simulation with subsequent sustainability assessment was therefore developed. The economic assessment can be realized in an early stage of conceptual design by calculation of operational costs and in an advanced stage by dynamic investment calculation. The environmental assessment is conducted by life cycle assessment. Different impact assessment methods like ReCiPe 1.08, EC-RED and others have been used, depending on the aim of the study. Based on the results of these calculations key parameters of the biorefinery concepts can be identified and optimization approaches can be developed. Possibilities for the application of the methodology in different biorefinery concepts will be presented. The products evaluated by the methodology are first and second generation biofuels, biokerosene and biochemicals. The methodology was developed, optimized and applied in different projects throughout the last 5 years. It has helped to identify and develop process configurations with improved sustainability regarding both economic and environmental criteria. The methodology can now be applied to further biorefinery concepts.