Abstract: A contaminated medium (such as soil and/or groundwater) contaminated with petrogenic and/or other organic contaminants such as petroleum hydrocarbons, light non-aqueous phase liquids (NAPLs), dense non-aqueous phase liquids (DNAPLs), persistent organic pollutants (i.e. sulfolane), chlorinated compounds, and volatile organic compounds, can be mixed with enhanced stimulators and be thermally remediated. The enhanced stimulators are heat induced to undergo exothermic reactions, which initiate a series of in-situ chemical reactions to such as to produce hydrogen gas. The hydrogen gas causes hydrocracking of heavy hydrocarbons to produce light hydrocarbons which can be recovered such as for future use.