On-site production of hydrogen and carbon nanofibers by thermocatalytic decomposition (TCD) of mineral oil waste (MWO) is analyzed. An experimental study carried out at lab scale to estimate the yields that can be expected from TCD of the MWO collected in the Aragon area is presented. Based on these results, mass and energy balance have been carried out to have a preliminary estimation on the products that could be obtained by processing the 10 000 tonnes/year of MWO that can be collected in the Aragon region. The process would consist of four steps: (1) drying, (2) vaporization, (3) primary decomposition, and (4) catalytic decomposition. After drying and vaporization, MWO is converted in step 3 into fuel grade carbon and a gas mixture that mainly contains hydrogen and methane. Methane is partially converted in step 4 into hydrogen and a carbon material that contains carbon nanofibers which could be used to manufacture utilities with high added value. The 10 000 tonnes/year of MWO would yield 705 t/y of H2, 4962 t/y of fuel grade carbon, and 1016 t/y of pure carbon. The mixture obtained (71% H2: 23% CH4) could be used as a hydrogen source to obtain pure hydrogen or hydrogen-natural gas mixtures to fuel a captive fleet of public urban vehicles powered by fuel cells or dedicated ICE, respectively.