17. Techno-Economic Aspects in the Evaluation of Biorefineries for Production of Second-Generation Bioethanol

During the past decades, biorefineries have been in the research focus, to a large extent driven by the desire to produce biofuels for replacing fossil sources in the transportation sector. The heterogeneous composition of biological feedstocks opens for the possibility to produce a palette of products from any biorefinery, and this is also true for ethanol production from second-generation feedstock. The complexity of the process increases by using different processing paths, which include, e.g., reactions and separation operations. This complexity leads to difficulties in the understanding of the process and establishing a suitable design of the process. In biorefinery operations, relationships also exist between the outcome in terms of yields of the different products, which can be complicated further by the integration of internal and external processes, such as energy and mass flows. Integration can be used as a means to reduce energy utilization in the process; thus, the production cost can be cut. Techno-economic evaluations play an important part in guiding the development toward more economically and environmentally sustainable processes. In this chapter, we discuss topics, which focus on bioethanol biorefineries based on hydrothermal pretreatment. Some suggestions on how to perform techno-economic evaluations are also presented.