Natural Hydrogen as a Fuel ?
Hydrogen with Oxygen ignites in split seconds with a spark source and goes BANG with the right ratio of Oxygen.
Remember the Nazi's grand Zeppelin Hindenburg ?
https://www.msn.com/en-in/news/techandscience/vast-hydrogen-reserves-discovered-in-earth-s-crust-could-power-the-planet-for-170000-years/ar-AA1EWwp9