Lignocellulosic biomass is the most abundant organic compound on Earth and represents the major portion of the world’s annual production of renewable biomass. The global biomass production is about 150 billion tons annually (Balat and Ayar, 2005). Carbohydrates are by far the most omnipresent compo­nent of lignocellulosic biomass and are therefore often the preferred feedstock for the biobased economy. In fermentative processes there is sometimes more room for feedstock flexibility (proteins, triglycerides /fatty acids) but in the case of catalytic conversions such as the transformation of biomass into furan molecules you are restricted to carbohydrates. Sources of carbohy­drates include conventional forestry, wood processing by-products (e. g. wood chips, sawdust, bark, pulp and paper industrial residue as black liquor), agricul­tural crops and surpluses (e. g. corn stover, wheat and rice straw), and so-called energy crops (e. g. switch — grass, Miscanthus, willow) grown on degraded soils and aquatic biomass (algae, seaweeds). In this chapter we will focus on lignocellulosic biomass. Typical carbohydrate compositions are shown in Table 17.1. The majority of lignocellulosic biomass consists of carbohydrates (60—80%); the other main compo­nent is lignin (20—25%); proteins are mainly found in fresh (green) plant material. Amounts of triglycerides, extractives and inorganic materials are very much species as well as harvest time dependent. The bulk of the carbohydrates present in biomass are composed of poly/oligosaccharides, such as

hemicelluloses, cellulose, starch, and inulin. Sucrose is an omnipresent disaccharide consisting of a glucose and fructose moiety, whereas monosaccharides such as glucose and fructose are present in far lesser amounts. In particular, lignocellulosic plant matter is available in large quantities and is relatively cheap while aquatic biomass is given great potential for the future.