The equation used to calculate the yearly SO2 emissions (SO2) is as follows:
SO2 = (coal SO2 emissions) + (oil SO2 emissions) (in tons)
If gas is the only fuel, gas emissions are defaulted to 0.
Each fuel type SO2 emissions is calculated on a yearly basis, using the equation:
fuel SO2 emissions (in tons) = (yrly wtd. av. fuel sulfur %) × (AP-42 fact.) × (1−scrb. effic. %/100) × (units conver. fact.) × (yearly fuel burned)
For coal, the yearly fuel burned is in tons/yr and the AP-42 factor (which accounts for the ash retention of sulfur in coal), in lbs SO2 ton coal, is by coal type:
| Coal type
| AP-42 factor
|
|---|
| Bituminous, anthracite | 39 lbs/ton
|
| Subbituminous | 35
|
| Lignite | 30 |
For oil, the yearly fuel burned is in gal/yr. If it is in bbl/yr, convert using 42 gal/bbl oil. The AP-42 factor (which accounts for the oil density), in lbs SO2/thousand gal oil, is by oil type:
| Oil type
| AP-42 factor
|
|---|
| Distillate (light) | 142 lbs/1,000 gal
|
| Residual (heavy) | 157 |
For all fuel, the units conversion factor is 1 ton/2000 lbs.