Not really? It's not different from SMR. Hydrogen is tiny and non-polar, so it's easy to filter only for such small molecules, making storing it a pretty big is

Not really? It's not different from SMR. Hydrogen is tiny and non-polar, so it's easy to filter only for such small molecules, making storing it a pretty big issue. SMR produces a mixture of methane, water, hydrogen and carbon monoxide, which is just as easily filtered into plain dihydrogen. Nevertheless, it's still just storing it somewhere in a cave, not really worth the effort most of the time, and since CO / CO₂ is a lot smaller than methane, it'll find its way out by other means way easier.