Q696. Should combustion emissions from a steam methane reforming (SMR) furnace be reported under subpart C or subpart P?  Is the answer different if the process heater used to provide heat needed for the SMR reaction has a separate exhaust stack from the SMR unit’s tail gas?

A696. For the purposes of the GHGRP, all emissions from the SMR furnace are considered hydrogen production process unit emissions and should be reported in subpart P following the methodologies in subpart P, rather than subpart C, regardless of the fuel(s) used to fire the SMR furnace or how those emissions are released to the atmosphere. This also applies to partial oxidation units and autothermal reforming units. While most SMR, partial oxidation units, and autothermal reforming hydrogen production process units have a common stack that contains combustion emissions and hydrogen production unit tail gas, there may be hydrogen production units that have separate stacks for the combustion and tail gases. Process heaters used to supply heat needed for the SMR reaction are considered part of the hydrogen production process unit regardless of whether these emissions are co-mingled with the process unit’s tail gas. As such, fuel used for process heaters used to supply heat needed for the SMR reaction should be included in the “fuel and feedstock material balance approach” calculation methodology provided in 40 CFR 98.163(b) even if the process heater emissions are emitted in a separate stack from the tail gas. Subpart C should only be used for “each stationary combustion unit other than hydrogen production process units” at the facility.   

Accordingly, a CEMS used on a stack that includes hydrogen production unit tail gas and SMR furnace combustion emissions should be reported using the “single process” monitoring location configuration.  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 combustion-related CO2 emissions for the hydrogen production unit must also include process heater emissions calculated and reported under subpart P using the material balance approach in 40 CFR 98.163(b) considering only the fuel inputs to the hydrogen production unit’s process heater.