The Portable Renewable Energy System for Enhanced Oil Recovery (“PRESEOR”) is a truck mobile system that reforms biomass into CO2 and hydrogen, following which the gases are separated, with the CO2 sequestered underground for enhanced oil recovery (EOR) and the hydrogen used to generate several megawatts of carbon-free electricity. In contrast to large central power plants that are generally not well-located to support EOR, the small PRESEOR can go directly to the oilfields where it is needed, and do so in a timely manner. The PRESEOR sequesters more biomass-derived carbon than is released by the burning of the oil it yields, thereby producing not only carbon-free electricity but carbon-free oil. Using PRESEOR, over 80 billion barrels of U.S. oil would be made recoverable, without the need to drill new wells in pristine areas.