A method for producing a hydrogen enriched fuel and carbon nanotubes includes the steps of providing a flow of methane gas, and providing a catalyst mixture comprising a Fe based catalyst and carbon. The method also includes the steps of pretreating the catalyst mixture using microwave irradiation and exposure to CH4, heating the catalyst mixture and the methane gas using microwave irradiation at a selected microwave power, directing the flow of methane gas over the catalyst mixture, and controlling the microwave power to produce a product gas having a selected composition and the carbon nanotubes. For producing multi walled carbon nanotubes (MWNTs) only a flow of methane gas into the reactor is required. For producing single walled carbon nanotubes (SWNTs), a combination of hydrogen gas and methane gas into the reactor is required.