Look into updated default emission factors

[grgmiller]

The eGRID2020 technical guide notes that:

The emission factors are primarily from the default CO2 emission factors from the EPA Mandatory Reporting of Greenhouse Gases Final Rule (EPA, 2009, Table C-1). For fuel types that are included in eGRID2020 but are not in the EPA Mandatory Reporting of Greenhouse Gases Final Rule, additional emission factors are used from the 2006 Intergovernmental Panel on Climate Change (IPCC) Guidelines for National Greenhouse Gas Inventories and the EPA Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2015 (IPCC, 2007a; EPA, 2017).

However, it is unclear whether there might be more up to date emissions factors that should be used:

• [ ] Look into whether there are newer default GHG emission factors than those in the 2009 EPA Final Rule
• [ ] Look into whether IPCC emission factors have been updated since 2006
• [ ] Look into whether there are updates to the 2017 EPA Inventory of U.S. Greenhouse Gas Emissions and Sinks

The technical guide also notes:

Several fuel types do not have direct reported emission factors, so emission factors from similar fuel types are used: • The emission factor for natural gas is used to estimate emissions from process gas and other gas; • The emission factor for anthracite, bituminous, and lignite coal are used to estimate emissions from refined coal and waste coal; and • The emission factor for other biomass liquids is used to estimate emissions from sludge waste and liquid wood waste

• [ ] Research whether there are now specific emission factors for process gas (PRG)
• [ ] Research whether there are now specific emission factors for other gas (OG)
• [ ] Research whether there are now specific emission factors for refined coal (RC)
• [ ] Research whether there are now specific emission factors for waste coal (WC)
• [ ] Research whether there are now specific emission factors for sludge waste (SLW)
• [ ] Research whether there are now specific emission factors for liquid wood waste (WDL)

[grgmiller]

The eGRID technical guide also notes that for geothermal emissions:

The three pollutants’ [CO2, SO2, NOx] emission factors, obtained from a 2007 Geothermal Energy Association environmental guide (GEA, 2007), are applied to plant net generation, and differ depending on the type of geothermal plant as identified in various reports from the Geothermal Energy Association (now known as Geothermal Rising) (GEA, 2016)

• [ ] Research whether there are more recent emission factors for these plant types than 2007
• [ ] Research whether geothermal plants can have CH4 and N2O emissions
• [ ] Can geothermal plants actually have NOx and SO2 emissions? The eGRID documentation refers to "hydrogen sulfide combustion" as the source of these emissions.

[grgmiller]

IPCC Factors come from Chapter 2: https://www.ipcc-nggip.iges.or.jp/public/2006gl/pdf/2_Volume2/V2_2_Ch2_Stationary_Combustion.pdf, Table 2.2 To convert from (kg of greenhouse gas per TJ on a Net Calorific Basis) to lb/mmbtu, you must multiply by 0.002326

[grgmiller]

SGC Synthesis Gas from Coal is only burned in a single plant: 1004. We currently use the NG rate for this, but the EIA actually says this factor should be created based on the input fuel to producing the gas.

If you look at the CEMS data for plant 1004, it has a relatively consistent co2 output of about 286.37 lbCO2/mmbtu of fuel, which suggests that this may be the appropriate factor for SGC.