A novel Alkaline Thermal Treatment (ATT) reaction has been proposed as a unique bio-energy with carbon capture & sequestration (BECCS) approach. While our previous study demonstrated that high purity H-2 can be produced from cellulose with a Ca(OH)(2) and 10% Ni/ZrO2 mixture while suppressing CO2 formation, its complex reaction pathways are not understood. In order to decouple the solid and gas-phase catalytic reactions and improve the overall ATT of biomass, in-situ and ex-situ catalystic ATT reactions have been carried out. A screening of low loading Fe, Cu, Co, Pd, Pt and Ni catalysts showed that Ni was capable of significantly enhancing H-2 production when placed in-situ or ex-situ. This suggested that the ATT of cellulose involves the reforming of intermediates (i.e., gaseous hydrocarbons) to H-2. Catalyst development and reactor design should consider both solid phase and gas-phase reactions in order to maximize the potential of this BECCS technology. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.