The most promising way to meet the sustainability goals for the future (including the reduction in GHG emissions, reduced dependence on fossil fuels, etc.) is to promote the utilisation of low-carbon technologies to convert biomass into a
variety of chemicals, biomaterials and energy, maximising the value of the biomass while minimising waste.

This integrated approach has been defined as ‘the biorefinery concept’ and has recently received a great deal of attention in many parts of the world.16,17 The biorefinery of the future will be analogous to today’s petrorefineries18,19 in such a way that many different industrial products will be generated from biomass (Fig. 1.1). These include low-value, high-volume products, such as transportation fuels (e. g. biodiesel, bioethanol, etc.), commodity chemicals and materials, as well as high-value, low-volume products or speciality chemicals, such as cosmetics and nutraceuticals.

Energy and, most precisely, biofuels are the main driver for developments in this area, but other relevant products are expected to be developed as biorefineries become more and more sophisticated with time.

Several types of biorefineries have been described in the literature, mainly phase I, II and III biorefineries, depending on the variety of feedstocks, processes and products obtained in the facilities. Biofuels are part of the products obtained from the treatment of a wide variety of biomass feedstocks, actually playing a major role in the economics of the process. This highly interesting topic will be fully tackled and expanded in the Appendix chapters (Chapters 21 and 22), in which types of integrated biorefineries, processes for biofuels production and by-products and related subjects will be revised.

Last but not least, engine tests are of utmost importance to test the feasibility of biofuels implementation in the future. In this way, Chapter 23 accounts for a nice contribution, combining a revision with experimental results on the implementation of biofuels (both pure and as blends) in engine tests.

1.1 Comparison of petro — versus biorefinery (from Introduction to Chemicals from Biomass, Edited by James Clark and Fabien Deswarte; Copyright John Wiley & Sons, 2008; reproduced with permission).