Q67. Where the heat input capacity of a combustion unit is less than 250 mmBtu per hour input capacity and the unit is not subject to Tier 3 or 4 per Subpart Y of Part 98, and where there might be more than one fuel type fed to the same combustion unit, can the Tier 2 method be used to calculate emissions by using measured HHV values of input streams or a measured HHV of the mixed stream?

A67. For fuels that are blended prior to combustion, you may: (1) use the weighted HHV value based on the relative proportion of each fuel in the blend and a weighted average CO2 emission factor from Table C-1; or (2) use the HHV value determined by collecting and analyzing a representative sample of the blended fuel and using a weighted average CO2 emission factor from Table C-1, based on the relative portion of each fuel in the blend. See 98.34(a)(3).