I love those Ebay kits with H2 tanks that are plastic. I seem to remember H2 being the smallest naturally occurring molecule. So even with it cold (near absolute zero aka -273 Celsius) it still has enough energy to break out of any container, it just slips through the space between the molecules of the container, bit like trying to keep sand in a sieve.
I suppose we could all carry a few farm animals on a trailer behind us, capture the methane and run on that, we'd probably need a whole herd of cattle to supply enough to power an engine at tick-over, let alone under load, but hey why not sell that as an alternative energy source for vehicles. Right I'm off to sell some instruction booklets on Ebay