Reactive molecular dynamics was used to explore the thermal decomposition of several biomass model compounds. We used ReaxFF methodology developed by the Goddard group at Cal Tech [van Duin et al. 2001; Strachan et al., 2005; Chenoweth et al., 2008]. It is a general bond-order-dependent potential in which van der Waals and Coulomb forces are included from the beginning. The parameters are obtained from QM calculations and the most recent version is parameterized for CHNO systems, as is necessary to explore biomass reactions. Calculations have been carried out for compounds representative of cellulose (glyceraldehyde, β-D-glucopyanose, β-cellobiose, cellulose I), hemi-cellulose (β-D-xylofuranose, D-mannopyanose), and lignin (methoxybenzene, ethoxybenzene, phenethyl phenyl ether.) In all cases the predicted primary products are those observed experimentally or suspected from bond strength and or transition state analysis.