What Tier, if any, must be used for a fuel not listed in Table C-1 that is less than 10% of the heat input of a combustion unit?
If the unit is less than or equal to 250 mmBtu/hr, GHG emissions reporting is not required if the fuel or the fuel constituents are not listed in Table C-1. However, if the unit is greater than 250 mmBtu/hr, CO2 emissions reporting for a fuel not listed in Table C-1 is required, using Tier 3, if: (1) combustion of the fuel accounts for 10% or more of the combustion unit’s annual heat input; and (2) the unit is not required to use Tier 4. This response applies only to units that calculate CO2 emissions in accordance with Subpart C. If a combustion unit with a heat input capacity less than 250 mmBtu/hr burns both natural gas and a liquid fuel, and the quantities are known, can Tier 1 be used for the natural gas calculations and Tier 2 for the liquid or must Tier 2 be used for both? The tiering requirements are applied to each fuel in a combustion unit, not to the combustion unit as a whole. Therefore, in this example, different tier calculation methods can be used for the natural gas and
