The EPA data is hard to interpret. How do you know what portion of the reported power output is gas-generated?
In the EPA CEM reports, some plants provide heat input measured at the point of fuel delivery (“direct approach”), while others estimate the heat input by measuring the quantity of gases or carbon at the emissions stack (“CEMS-based approach”). Plants using the direct-approach submit hourly natural gas and oil input measured in MMBtu (record type 302 and record type 303, respectively). For those plants, it is clear what portion of the heat input is attributable to which fuel for every hour of operation. Plants using the CEMS-based approach submit formulae that can be interpreted to derive the fuel contribution to the heat input. A majority of the CEMS-based approach submittals use an F-factor which is the ratio of either carbon mass or gas volumes to the heat content of the fuel. The portion of each fuel can be derived from the standard formulas used, which are described in record type 520. The formulae have essentially this format: F = Xi * Fi + Xii * Fii…+ Xn*Fn where F is the f fact
