Q699. How do I determine the quantity of CO2 emissions produced for hydrogen production process units that use multiple fuels and feedstocks?

A699. For units not monitored by a CEMS, the CO2 emissions should be the sum of the annual emissions associated with each fuel and feedstock used for hydrogen production, using the applicable equations in paragraphs 40 CFR 98.163(b)(1) through 98.163(b)(3).  For example, if your hydrogen production process unit uses refinery fuel gas for fuel and natural gas for feedstock, Equation P-1 should be applied separately for each fuel and feedstock to calculate the CO2 emissions from each.  These CO2 emissions should then be summed and the total reported. For CEMS-monitored units, the CO2 emissions should be determined using the Tier 4 calculation methodology as described in 40 CFR 98.163(a). If a CEMS is used on a stack that only contains hydrogen production unit tail gas and a separate stack contains combustion emissions from the process heaters used to supply heat, the CEMS is used to determine the tail gas CO2 emissions using the Tier 4 calculation methodology as described in 40 CFR 98.163(a) and the combustion-related CO2 emissions for the hydrogen production unit must be calculated and reported using the material balance approach in 40 CFR 98.163(b) considering only the fuel inputs to the hydrogen production unit’s process heater.