An on-line pulp digester control system. More particularly, this invention pertains to a control system which employs real time measurements from ion mobility spectrometry to automatically rapidly and continuously determine the physical and chemical characteristics of wood chip feedstock being fed into a pulp digester and thereby maximize process efficiencies, minimize chemical and energy consumption and improve product uniformity. An intelligent control system which utilizes the moisture content and species of wood chips on-line in a pulping process comprising: (a) conveying wood chips from a wood chip storage facility to a digester; (b) scanning the wood chips as they are conveyed to determine their species and moisture content by heating the wood chips and sensing the moisture content and characterizing the species of the wood chips by species signatures obtained by an ion mobility spectrometer; and (c) regulating steam flow and chemicals supplied to the digester according to the moisture content and the characterization of the wood chip species.