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Natural gas boiler billed in therms: CO2, CH4, N2O and CO2e (EPA inventory guidance example) inside a scope 1, 2 and 3 inventory
| Tool | GHG Emissions Inventory |
| Source | U.S. Environmental Protection Agency (2023). Greenhouse Gas Inventory Guidance: Direct Emissions from Stationary Combustion Sources. Center for Corporate Climate Leadership, December 2023. Example Emissions Calculation, pp. 6-7; factors from U.S. Environmental Protection Agency (2025). Emission Factors for Greenhouse Gas Inventories. GHG Emission Factors Hub, 15 January 2025, Tables 1 and 11. |
| Level | Professional |
Problem
An organization has an on-site natural gas boiler and twelve monthly utility bills totalling 6,000,000 scf at 1,025 Btu/scf, 61,500 therms. Calculate the year's CO2, CH4 and N2O and the total in CO2 equivalent with the AR5 global warming potentials. The tool's default inventory adds illustrative rows around this one (a generator, a fleet, refrigerant top-ups, two sites' electricity, district steam, travel, commuting, freight and waste).
Inputs to Enter
- Stationary combustion row 1: natural gas, 61,500 therm (1 therm = 100,000 Btu = 0.1 mmBtu)
- Hub Table 1 factors for natural gas: 53.06 kg CO2, 1.0 g CH4 and 0.10 g N2O per mmBtu; GWP (AR5, hub Table 11): CH4 28, N2O 265
- Other default rows (illustrative): 500 gal No. 2 oil; 12,000 gal gasoline over 300,000 mi (2020 cars); 8,000 gal diesel over 60,000 mi (2018 trucks); 12 kg R-410A; 5 kg HFC-134a; 1,200,000 kWh in RFCE; 400 MWh in SRVC with 50 % instruments; 800 mmBtu steam; travel, commuting, freight and waste rows
Answers
- Fuel energy 61,500 × 0.1 = 6,150 mmBtu (book 6,150 mmBtu)
- CO2 = 6,150 × 53.06 kg = 326.3 metric tons (book 326.3); CH4 = 6,150 × 1.0 g = 6.15 kg (book 6.15 kg); N2O = 6,150 × 0.10 g = 0.615 kg (book 0.615 kg)
- CO2e = 326.3 + 28 × 0.00615 + 265 × 0.000615 = 326.7 metric tons CO2e (book 326.3 + 0.2 + 0.2 = 326.7)
- Default inventory: scope 1 549.3 t CO2e; scope 2 487.5 t location-based and 433.4 t market-based; scope 1 + 2 1,037 t and 982.6 t; scope 3 (entered categories) 309.4 t
- Default scenarios together (efficiency, half of the gas to a heat pump, 100 % renewable electricity): scope 1 + 2 market-based 412.8 t, −58.0 %
Notes
The tool's default inputs hold this row first; press Submit and read the section 'Calculation of the First Row'. Only the boiler row is a published example; the other default rows are illustrative and their totals are the tool's own (eGRID2023 revision 2 rates). The guidance example, every cell of hub Tables 1 to 12 against the PDF, the AR4 and AR6 values against 40 CFR 98 Table A-1 and the EPA inventory annex, and 20 seeded inventories against numpy are reproduced by test_ghg_emissions_inventory.php (6,697 checks). The guidance's own example is the only numerical one in the four EPA inventory guidance documents.