There's steam methane reforming from natural gas; it converts methane to CO2 and H2, and you separate those. This is already a large scale commercial process (e

There's steam methane reforming from natural gas; it converts methane to CO2 and H2, and you separate those. This is already a large scale commercial process (e.g. used for hardening fat in food or upgrading petroleum to fuel), giving tens of millions of tonnes per year, and recent plants even include CO2 capture and storage, making it a low carbon source.