In order to accurately simulate the chemical reaction of lignocellulose, it is necessary to have a model of its composition. This involves two main challenges: (i) identifying the precise chemical structure of the lignocellulose, and (ii) creating a compositional model that can approximate this structure. Today, useful progress has been made on (i) but compositional models (ii) are basic and limiting to progress . For both the chemical reaction and compositional modelling challenges, the works of Ranzi and co-workers have made pioneering progress. Normally, only the elemental composition (C/H/O) of lignocellulose is typically reported . Ranzi and coworkers innovate by inferring the biochemical composition of individual lignins and lignocelluloses by relating their C/H/O elemental composition to that of a set of seven reference species. The approach established by Ranzi et al. is to define pseudocomponents (real or virtual model compounds) that contain the main chemical compositional features of actual biomass materials. These pseudo-components are combined in the fractions needed to replicate the C/H/O of the target lignocellulose. The approach is similar to compositional modelling work on liquid fuels by Dooley et al. . In both, there are two key aspects; (i) accurate provision of (lignocellulose) chemical functionalities by pseudo-component definition, and (ii) selection and determination of meaningful indicators of lignocellulose composition. The state-of-art practice has been to directly couple this compositional model to the chemical equations and rate constants that constitute the reaction kinetic model. Models of this type are refered as to (lumped) compositional-kinetic models.