Biomass is becoming a more and more attractive source of "low carbon" chemicals, materials and fuels. In our future society, the use of biomass will have a key role for the defossilization of the energy (fuels) and chemical sectors, even if biomass alone cannot satisfy all human needs. While the use of biomass for the generation of thermal energy (the most primitive one, since man developed the capacity to manage fire, and less rewarding use) will have a slowly decreasing role (most likely

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... residual refractory biomass, more than primary biomass), the biomass exploitation as source of complex chemicals, materials and special fuels will undoubtedly grow. As a matter of fact, biomass is an extremely rich raw substance that can be used as a source of many different molecular compounds and polymeric materials, increasing the profit and reducing the environmental burden of its use. Consequently, the conversion of primary biomass into syngas (CO + H 2 ), an approach pursued for decades, is affected by a serious drawback: a complex matter is converted into a C1 molecule (CO), which is then used to build more complex Cn molecules. Such huge change in entropy in using biomass is energetically questionable, especially if primary biomass is used to this end. The application of such technology to residual biomass can be more useful. The direct use of the complexity of biomass is certainly a much clever approach to its best exploitation."Biorefinery" is a concept implemented since a decade for making the most economically profitable and environmentally friendly use of biomass. Noteworthy, the conversion of the latter into market end products heavily implies catalysis of any kind: homogeneous, heterogeneous, enzymatic, and their combination in hybrid catalytic systems. This book aims at giving a quite comprehensive view of the opportunities offered by the implementation of the concept of biorefinery to biomass utilization. The Introduction, written by Dr. Maria Georgiadou of the EU Commission, sets the political basis for the technical chapters that follow, some of which have been written by industrialists deeply involved in the valorization of biomass and implementation of the concept of Bioeconomy. The intelligent use of Biomass is one aspect of the strategic concept of Carbon Cyclic Economy. In Chapter 1, the transition from the Linear to the Circular Economy is discussed, and the relevance of catalysis to Biorefinery is presented, while Chapter 2 opens a window over the future of Biorefinery. Chapter 3 presents the production of a variety of terrestrial biomass according to climatic conditions and soil quality, Note: This second edition of the book on "Biorefineries" contains some new chapters with respect to the first edition, and updated chapters present in the first edition. Chapters 3 and 10 are the same as in the first edition as the authors could not update them due to the pandemic COVID19. They have only been re-edited for matching the format of this book.