The Computational Pyrolysis Consortium, funded by US Department of Energy through the Bioenergy Technologies Office (BETO), complements DOE-funded experimental research programs on the conversion of cellulosic biomass into fuels and fuel feedstocks. This presentation will review the overall goals and structure of the consortium and then discuss one facet of the work at PNNL on condensed phase upgrading, namely capturing the kinetics of the fouling of catalysts for the hydro-upgrading of pyrolysis oil. The coking of catalysts for the hydroprocessing of petroleum-derived streams does not serve as a useful precedent because bio-oils contain functional groups that permit very different pathways for the production of oligomeric, refractory deposits. Rather, classical gelation appears to be a suitable model for the “gunking” reaction. Our work has helped explain the temperature range at which bio-oil should be pre-processed (“stabilized”) to confer longer lifetimes on the catalysts used for more severe processing. Finally, I will discuss the use of stochastic modeling to capture the rates of hydroprocessing and hydrocracking reactions of bio-oil.