Biomass can be converted to chemicals through thermochemical or (bio-)chemical pro­cesses. The most promising thermochemical process is direct gasification of biomass, where the whole feedstock is kept at high temperature (>700 °C) with low oxygen levels to produce syngas, a mixture of H2, CO, CO2, and CH4 (Gassner and Marechal, 2009; van Vliet et al.,

2009) . These C-1 building blocks are then reassembled into the desired functional molecules. Other common thermochemical processes are pyrolysis and combustion for heat and power. These thermochemical approaches do not consider the complex molecular structures synthesized by nature, since they destroy the original biomass structure, which should be rather used to the maximum possible extent (Marquardt et al., 2010). Contrarily, the target of (bio-)chemical processes is to access the rich molecular structure already available in biomass without significant degradation of the basic components. For this purpose, the pretreatment step of lignocellulosic biomass is particularly important, since the three main biomass components must be efficiently separated into independent flows, lignin, cellulose, and hemicellulose, to be further processed (Fernandes et al., 2009; Kaparaju and Felby, 2010; Sun and Cheng, 2002). After pretreatment, these highly functionalized polymers have to be selectively depolymerized. Next, the resulting molecular structures need to be isolated and catalytically re-functionalized into target molecules. Such an advanced strategy offers the chance to establish conversion processes with higher carbon efficiency and lower entropic losses compared to conventional thermochemical processes. Although conceptually attrac­tive, its implementation requires the tailoring of the industrial value chains to the nature of the bio-based raw materials. Preserving the natural molecular structures in the raw materials requires a shift from gas-phase reactions at high temperatures, prevalent in petro­leum-based chemical engineering, to liquid-phase reactions at lower temperatures. Likewise, low-temperature separation technologies should be favored over classical distillation if possible. Higher viscosities of the process media and the management of large amounts of water are inevitable side effects offering their own challenges (Marquardt et al., 2010).