Emissions factors are used and relate a quantity of pollutant emitted (e.g., tons of CO2) per unit of fuel burned. There are factors for each of the six pollutant types corresponding to each main fuel type. To estimate emissions, FEDS multiplies the consumption value for each fuel type by the appropriate emission factor. The emissions factors for certain fuel types, (for example electricity) can vary significantly depending on factors, such as plant type (coal, gas, nuclear, hydropower) and source fuel composition (e.g., sulfur content) such that state average values are applied based on the typical generation resource mix supplying that state.