Q86. 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?

A87. 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.