Emissions

I keep reading that the Hazer process is described as “low emission”. While my rudimentary understanding of the methane cracking process does not produce CO2, then presumably the emissions are either not 100% efficient and therefore some CO2 is created, or the natural gas which itself is not pure methane, contains other impurities. Or is
the CO2 created during the mining of the iron or and also that created from the gas extraction factored into the”low emissions” claim? This is an important point because it may be enough for other processes to accuse the Hazer process of not being green enough.