Eq. (1) shows that the removal of o

Eq. (1) shows that the removal of one CO mole via methanation requires 3 mol of H2. Of these, 2 mol are restored in the CH4 product, which can be reused after PEM FC reactions through re-circulating the anode cell off-gas into the reformer as a feedstock or, in a better thermodynamic way in the case of a steam reformer SR, as a fuel burnable for the SR heating purposes. A PEM FC system, in general, has to be equipped with an off-gas re-circulation line to recover the unreacted H2 that may reach 10–20% of its original feed [18]. Hence, for CO-SMET the actual H2 loss into H2O should be 1 mol for 1-mol of removed CO, if the methanation selectivity toward CO is 1.0 or 100%.