Pyrolysis, biomass cellulose pathways

Pyrolysis as defined is a process of thermal decomposition occurring in the absence of oxygen. Pyrolysis of biomass is a complicated multistage reaction for which many pathways and mechanisms have been proposed.551-558 The best known is the model developed by Broido and Shafizadeh559,560 for pyrolysis of cellulose that can be also applied, at least qualitatively, to whole biomass (Fig. 33.30). 

Pyrolysis of biomass is defined as the chemical degradation of the biopolymers (cellulose, lignin and hemicellulose) constituting the wood fuel which initially requires heat. As can be seen in Figure 51, all reaction pathways making up the pyrolysis are not endothermic, which implies that some of the pyrolysis reactions generate heat. However, overall the pyrolysis process is endothermic. 

Biomass is a complex polymeric material and its thermal deconqiosition is a multistage complicated process. Many pathways and mechanisms have been proposed to illustrate/cxplain the fundamental steps in pyrolysis (e.g. 5, 6, 7, 8, 9, 10, 11, 12, 13). Broido-Shafizadeh type kinetic models are perhaps the most widely used for cellulose pyrolysis but they can be also applied, at least qualitatively, to the whole biomass (see Figure 1). 

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