Where:
Es = Prorated SO2 emission limit (ng/J heat input);
%Ps = Percentage of potential SO2 emission allowed;
x = Percentage of total heat input derived from the combustion of liquid or gaseous fuels (excluding solid-derived fuels); and
y = Percentage of total heat input derived from the combustion of solid fuel (including solid-derived fuels).
40 C.F.R. §60.43Da