CH4 + H2O ⇌ CO + 3 H2

CO + H2O ⇌ CO2 + H2

For every tonne of hydrogen produced this way, 9 tonnes of CO2 is also produced.

Isnt the ratio closer to ~6 tons of CO2 per ton of H2? You get CO2 + 4 H2, which weigh 44 and 4*2 respectively.

Also, isnt this a non-issue, because (at least in theory) the reaction is contained in your converter plant, where you can collect the CO2?

That's quote from wikipedia. I think you're right with your calculations, so I don't really know where this number came from.

What're you going to do with that collected CO2 other than releasing it to the atmosphere?

Separating from other gasses, followed by sequestering.

I guess that it would cost a lot. Technically you can do that with traditional coal plants.

Those don't produce fuel. They produce electricity.