Greenhouse gas (GHG) reporting can be voluntary, customer-driven, state-specific, or mandatory under EPA's Greenhouse Gas Reporting Program (GHGRP) in 40 CFR Part 98. Thresholds, deadlines, verification, GWP basis, covered sources, and reporting formats vary by program, so a calculator output should be treated as a planning screen until the applicable rule or protocol is selected.
The arithmetic is still important: activity data such as fuel burned, electricity consumed, or gas released is multiplied by emission factors and global warming potentials to produce a CO2-equivalent screen. The defensible inventory work comes from the harder parts: organizational boundary, operational boundary, complete source list, fuel and meter records, factor source, reporting-year rule text, quality controls, and qualified environmental or legal review.
Scope 1, 2, and 3: Where to Draw the Lines
The GHG Protocol, developed by the World Resources Institute (WRI) and the World Business Council for Sustainable Development (WBCSD), is a widely used framework for categorizing greenhouse gas emissions into three scopes. EPA and other programs may use different covered-source, applicability, GWP, and reporting rules, so scope labels should be paired with the specific rule or protocol being used.
Scope 1 covers direct emissions from sources owned or controlled by your facility. This includes combustion of fuels in boilers, furnaces, generators, and vehicles; process emissions from chemical reactions or manufacturing; fugitive emissions from equipment leaks; and releases of fluorinated gases from refrigeration and air conditioning. Scope 1 is what your facility physically puts into the atmosphere. For most industrial facilities, Scope 1 is dominated by natural gas combustion, with smaller contributions from diesel generators, fleet vehicles, and refrigerant leaks.
Scope 2 covers indirect emissions from purchased electricity, steam, heating, and cooling. A location-based electricity screen can use EPA eGRID regional factors; a market-based inventory may use supplier-specific factors or contractual instruments under the selected protocol. The ToolGrit app uses selected eGRID 2023 location-based factors only and does not evaluate RECs, PPAs, green tariffs, hourly matching, or supplier quality criteria.
Scope 3 covers other indirect emissions in the value chain: business travel, employee commuting, purchased goods and services, transportation and distribution, waste disposal, and downstream use of products. Scope 3 requirements depend on the reporting framework, stakeholder request, and materiality screen. Start with a complete Scope 1 and 2 source list, then add Scope 3 categories when a specific protocol or request requires them.
Scope 1 (Direct): Natural gas, diesel, propane, gasoline you burn; refrigerant leaks; process emissions; company vehicles
Scope 2 (Indirect - Energy): Purchased electricity; purchased steam or hot water; purchased chilled water
Scope 3 (Indirect - Value Chain): Business travel; employee commuting; purchased materials; freight; waste disposal
Start with Scope 1 + Scope 2. These represent the emissions you can directly influence through operational decisions.
CO2 Capture / Carbon Intensity Calculator
Calculate gross and net CO2 emissions with carbon capture, CH4 and N2O equivalents, and carbon intensity per unit output. Uses 40 CFR Part 98 factors.
EPA Mandatory Reporting Rule: 40 CFR Part 98
EPA's Greenhouse Gas Reporting Program (GHGRP), codified at 40 CFR Part 98, requires annual reporting for covered source categories when the applicable rule thresholds and methods are met. The common 25,000 metric ton CO2e value is a review trigger for many facilities, but applicability depends on subpart coverage, direct emissions, source-category rules, exemptions, records, and current rule text.
Part 98 is organized into subparts, each covering a specific source category with its own calculation methods. Subpart C covers stationary fuel combustion and can require calculating CO2, CH4, and N2O by fuel type under the applicable tier. Tables C-1 and C-2 may be relevant, but exact factor use depends on fuel records, HHV, measurement method, CEMS/Part 75 status, biomass treatment, and reporting-year instructions.
Purchased electricity (Scope 2) is not by itself a Part 98 direct-emissions threshold item. A combined Scope 1 plus location-based Scope 2 total can still be useful for voluntary inventory planning, but it is not a Part 98 applicability determination. If the Scope 1 screen is near a threshold, move from app arithmetic to a qualified rule review.
Data quality requirements under Part 98 are source-specific. Fuel quantity, HHV, meter calibration, missing-data procedures, e-GGRT registration, recordkeeping, and resubmission duties depend on the subpart and method. Treat any planning worksheet as a checklist for records to gather, not as a report-ready calculation.
Covered source category and subpart
Direct-emissions threshold and calculation basis
Reporting year and current rule text
e-GGRT registration and designated representative
Fuel records, HHV, meter calibration, and missing-data procedures
Exit provisions, state overlays, and penalty exposure
Verify these items from current EPA/eCFR sources and qualified environmental/legal review before filing decisions.
GHG Reporting Consolidator
Consolidate Scope 1 combustion, fugitive refrigerant, and Scope 2 electricity emissions into a single CO2e inventory with eGRID factors and breakdown by scope.
Global Warming Potentials: Converting Gases to CO2 Equivalent
Greenhouse gas emissions are reported in metric tons of CO2 equivalent (MT CO2e), which normalizes different gases based on their heat-trapping ability relative to CO2. To convert a non-CO2 gas to CO2e, multiply the mass of the gas by its Global Warming Potential (GWP). The required GWP table depends on the reporting program, reporting year, gas identity, and whether the method distinguishes fossil methane or other variants.
ToolGrit's GHG app uses local AR5 planning rows for CH4, N2O, HFC-134a, R-410A, and SF6 because they are useful for a consistent screening basis. Regulated work should verify the current eCFR Table A-1, EPA factor hub, IPCC basis, state program table, or voluntary-framework instructions before using any GWP value.
The practical impact of GWP values is that small quantities of high-GWP gases can dominate a facility's GHG footprint. That makes refrigerant logs, gas purchases, recovery records, SF6 handling, and equipment inventories important source records. The app can show the arithmetic impact, but the source method and GWP basis still need review.
When reporting, calculate CO2e for each gas separately and then sum to get total facility CO2e. For combustion, calculate CO2, CH4, and N2O separately using the fuel-specific factors in Part 98 Table C-1 (for CO2) and Table C-2 (for CH4 and N2O). The CH4 and N2O contributions from natural gas combustion are small (typically less than 1% of total CO2e), but they must be included for regulatory reporting. For oil and coal combustion, the CH4 and N2O contributions are somewhat larger. For fluorinated gases, track each compound separately because GWPs vary widely even within the HFC family.
CO2e = mass of gas (metric tons) × selected GWP
Common planning bases differ: AR4, AR5, AR6, current eCFR Table A-1, and state or voluntary-program tables may not match. Record the basis beside the calculation and verify it before reporting.
Refrigerant Leak CO2 Equivalent Calculator
Calculate CO2 equivalent emissions from refrigerant leaks using EPA GWP values. Supports R-410A, R-134a, R-22, R-404A, R-407C, R-32, R-1234yf, and more. See annual GHG inventory impact in metric tons CO2e.
Calculation Methods: Getting the Numbers Right
GHG calculations for most facilities boil down to three types of sources: stationary combustion, purchased energy, and fugitive emissions. Each has a well-defined calculation method. The key is matching the right data to the right factors and keeping units straight. Most GHG calculation errors come from unit conversion mistakes (therms vs. CCF vs. MCF for natural gas, short tons vs. metric tons, gallons vs. barrels), not from using the wrong method.
For Scope 1 stationary combustion, the basic formula is: fuel consumed in energy units × emission factor = gas mass. For a local natural-gas screen, 50,000 therms is 5,000 MMBtu. CO2 at 53.06 kg/MMBtu is 265,300 kg before adding CH4 and N2O on the selected GWP basis. A regulated report still needs the correct fuel record, HHV, fuel type, tier method, and rule table.
For Scope 2 purchased electricity, a location-based screen is: annual electricity consumption (MWh) × eGRID factor (lb CO2e/MWh) × 0.453592 kg/lb. EPA eGRID2023 Revision 2 lists RFCW at 916.054 lb CO2e/MWh, so 10,000 MWh screens to about 4,155 MT CO2e. Market-based accounting can use different supplier or contractual factors and must be handled under the selected protocol.
For fugitive fluorinated gas emissions (refrigerants, SF6), the screening method is based on purchases: total gas purchased during the year minus gas returned for reclamation or destruction, plus gas in equipment at the beginning of the year minus gas in equipment at end of year. This gives net gas emitted. Multiply by GWP to get CO2e. The mass balance method is more accurate: for each piece of equipment, track beginning charge, gas added, gas recovered, and ending charge. The difference is the emission. For EPA Part 98 reporting, the required method depends on the source category and the facility's situation. Most facilities use the simplified purchase-based approach unless they have detailed equipment-level records.
1 therm = 100,000 BTU
1 CCF natural gas ≈ 1.02 therms (at 1,020 BTU/cf)
1 MCF = 10 CCF = 1,000 cubic feet
1 gallon diesel = 137,381 BTU (HHV)
1 gallon gasoline = 120,238 BTU (HHV)
1 short ton = 2,000 lbs = 0.907 metric tons
1 metric ton = 2,204.6 lbs = 1.102 short tons
1 kg = 2.205 lbs
Double-check units at every step. The most common GHG calculation error is a unit mismatch.
Reporting Requirements and Thresholds
The GHG reporting landscape includes federal, state, local, customer, lender, and voluntary programs, each with different thresholds, reporting formats, deadlines, verification rules, and covered sources. EPA Part 98 is a key federal rule for covered large emitters, but state programs and voluntary frameworks can use different boundaries and factor sources. Check the current program before treating any number as reportable.
Voluntary reporting through CDP, SBTi, The Climate Registry, customer portals, or lender questionnaires often follows GHG Protocol concepts, but the required categories and assurance level vary. A planning screen is useful for organizing activity data and finding major sources; it is not a substitute for the selected protocol, source records, or inventory management plan.
Third-party verification or assurance may be required by some programs or requested by stakeholders. Verification involves review of methodology, data sources, calculations, quality controls, organizational boundaries, operational boundaries, and record retention. Cost, assurance level, and evidence needs vary by program and facility complexity.
Building a defensible GHG inventory system means documenting everything from the start. Create a GHG reporting manual that describes your organizational boundary (which facilities are included), operational boundary (which sources and scopes are included), calculation methodologies for each source, data sources and responsible personnel, quality assurance procedures, and record retention policies. This manual is the first thing a verifier asks for and the last thing most facilities think to create. Write it while you are building the inventory, not after. Future you will be grateful when reporting deadlines arrive and every calculation is traceable to a documented methodology and data source.
Applicable federal, state, local, customer, and voluntary programs
Covered sources and threshold basis
GWP table and reporting year
Scope 2 location-based versus market-based requirement
Scope 3 category requirement or exclusion
Verification or assurance requirement
Record retention and inventory management plan
Do not rely on a generic program comparison for filing decisions; verify the current rule or protocol.