Catalytic reforming of biomass derived waste streams in the aqueous phase is a promising process for the production of sustainable hydrogen. Acetic acid will be a major component (up to 20 wt%) in many anticipated gasification feed streams (e.g. the aqueous fraction of pyrolysis oil). Conventional supported (e.g. alumina) catalysts deactivate in the presence of acetic acid rapidly due to coking and metal, support leaching and hence other catalytic systems must be developed to make this process industrially feasible. Carbon nanotubes (CNT) are very resistant to deactivation during acetic acid reforming in supercritical water and are therefore very suitable as catalyst support. Near complete reforming of a 25 wt% acetic acid solution in supercritical water (400 °C, 250 bar) was achieved during 7 h time-on-stream under commercially relevant conditions. The high stability of Ru/CNT for acetic acid reforming in supercritical water has paved the way for studying reforming of real biomass derived waste streams under these conditions.