Assumed NOx/SO2 emission factors

[grgmiller]

For its table of boiler type-specific NOx emissions factors, eGRID uses this table from EIA for emissions factors: https://www.eia.gov/electricity/annual/html/epa_a_02.html.

However, where there is not a specific NOx emission factor in this table (for example for ST prime movers with SUB fuel, but no information about the boiler type, it appears that eGRID assumes the lowest emission factor of all emission factors for this fuel type, rather than using the lower emission factor. In this case the factors for SUB range from 5-24, and eGRID uses 5.

On one hand, this could be considered conservative (ie we know that there is at least this much emissions), but on the other hand, this could be under-counting NOx emissions.

[grgmiller]

Also, there are two sources of data for LFG emission factors. One being the Electric Power Annual Table A-2, and one being table 2.4-4 in the EPA's AP-42 (https://www.epa.gov/sites/default/files/2020-10/documents/d02s04_0.pdf)

[grgmiller]

This issue is also relevant to SO2 factors