Petroleum is a relatively inexpensive, abundant, and convenient source of energy. One of the biggest drawbacks to using it as fuel is that doing so generates copious amounts of carbon dioxide, a greenhouse gas. Researchers in the U.K. and Saudi Arabia have taken a step toward mitigating that problem by demonstrating a CO2-free method for converting petroleum samples to high-purity hydrogen, a clean-burning fuel, and solid carbon, which can be stored underground safely or used commercially. Currently, most hydrogen comes from steam reforming methane, an energy-intensive process that produces a lot of CO2. Developed by Peter P. Edwards of the University of Oxford, John M. Thomas of the University of Cambridge, and coworkers, the new method uses microwaves to directly energize a low-cost iron nanoparticle catalyst, as opposed to using conventional heating, in which the heated fuel activates the catalyst (Energy Environ. Sci. 2018, DOI: 10.1039/c8ee02444h). Tests on diesel, gasoline, and methane show that the microwaves immediately generate gas, more than 90% of which is hydrogen. For heavy crude samples, the purity is roughly 80%. In contrast, the same catalyst, heated conventionally, converted diesel to 65% hydrogen and a mixture of alkanes, alkenes, and other gases.