New data were obtained for production of H2 and reduction of total organic carbon (TOC) by gasification of lactose in supercritical water with(out) the presence of catalysts (NaOH, KOH and Na2CO3) in a continuous Inconel 625 flow reactor. The gasification reactions were carried out at 550-700 °C, 22.5 MPa, lactose concentrations in the range of 0.5-2.5 wt%, feed flow rates of 5 and 7 g min-1 and a total reaction time of 30 min. The optimum condition for the production of H2 yielded approximately 4.5 mol H2/mol lactose with a TOC reduction of ∼95%. In addition, supercritical gasification of whey was carried out using the same operating conditions as the lactose system. A reduction of 92% on the TOC and 0.45 molar fraction of H2 production was achieved, similar to the gasification of lactose at a concentration of 0.5 wt%.