Scope 1 emissions
Scope 1 emissions include carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) that are emitted from stationary and mobile combustion, and from inadvertent fugitive emissions. Fugitive emissions can also include hydrofluorocarbons (HFCs), perfluorinated compounds (PFCs), sulfur hexafluoride (SF6), and nitrogen trifluoride (NF3). This article outlines the calculation methods that Microsoft Sustainability Manager uses for each type of emission source.
Stationary combustion
Microsoft Sustainability Manager follows the methodology of the United States Environmental Protection Agency (EPA) to calculate scope 1 emissions from stationary combustion sources. These sources include standard, biomass, and waste-derived fuels. One of the following two methods is used to calculate stationary combustion emissions, depending on the information that is available for the fuel.
EPA reference document: Greenhouse Gas Inventory Guidance: Direct Emissions from Stationary Combustion Sources (EPA.gov)
Fuel analysis method 1
In this method, the following equation is used to calculate emissions:
Emissions = Fuel × EF1
Here's an explanation of the equation:
- Emissions = Mass of CO2, CH4, or N2O that is emitted
- Fuel = Mass or volume of fuel that is combusted
- EF1 = CO2, CH4, or N2O emission factor per mass or volume unit
Method 1 is used when the heat content of the fuel is unknown, or when the fuel consumption is known only in mass or volume units. Because it has less certainty, this method is less preferred than method 2.
Fuel analysis method 2
In this method, the following equation is used to calculate emissions:
Emissions = Fuel × HHV × EF2
Here's an explanation of the equation:
- Emissions = Mass of CO2, CH4, or N2O that is emitted
- Fuel = Mass or volume of fuel that is combusted
- HHV (higher heating value) = Fuel heat content, in units of energy per mass or volume of fuel
- EF2 = CO2, CH4, or N2O emission factor per energy unit
Method 2 is the preferred method when the fuel usage is provided in energy units such as therms or British thermal units (BTUs), and when the heat content of the fuel is known.
For information about emission factors, see Emission Factors for Greenhouse Gas Inventories (Excel workbook).
Mobile combustion
Microsoft Sustainability Manager follows the EPA methodology to calculate scope 1 emissions from mobile combustion sources. The calculations differ from the calculations for stationary combustion emissions in that there are separate equations for CO2 and for N20 and CH4.
CO2 emissions
For CO2, one of the following two methods are used to calculate mobile combustion emissions, depending on the information that is available for the fuel.
EPA reference document: Greenhouse Gas Inventory Guidance: Direct Emissions from Mobile Combustion Source (epa.gov)
CO2 emission calculation method 1
In this method, the following equation is used to calculate CO2 emissions:
Emissions = Fuel × EF1
Here's an explanation of the equation:
- Emissions = Mass of CO2 that is emitted
- Fuel = Mass or volume of fuel that is combusted
- EF1 = CO2 emission factor per mass or volume unit
Method 1 is the recommended method only when the heat content of the fuel is unknown, and when the quantity of fuel is given in mass or volume units. Because it has less certainty, this method is less preferred than method 2.
CO2 emission calculation method 2
In this method, the following equation is used to calculate CO2 emissions:
Emissions = Fuel × HHV × EF2
Here's an explanation of the equation:
- Emissions = Mass of CO2 that is emitted
- Fuel = Mass or volume of fuel that is combusted
- HHV (higher heating value) = Fuel heat content, in units of energy per mass or volume of fuel
- EF2 = CO2 emission factor per energy unit
Method 2 is the preferred method when the heat value of the fuel is known, and when the consumption of fuel is given in energy units such as therms or BTUs.
N2O and CH4 emissions
For N2O and CH4 emissions, the calculation depends on the vehicle type: on-road (cars, trucks, or buses) or nonroad (construction or agricultural equipment, forklifts, ships, boats, rail vehicles, or aircraft).
On-road vehicle N2O and CH4 emission calculation
For on-road vehicles, the following equation is used to calculate N2O and CH4 emissions:
Emissions = Distance × EF4
Here's an explanation of the equation:
- Emissions = Mass of CH4 or N2O that is emitted
- Distance = Distance that the vehicle traveled
- EF4 = CH4 or N2O emission factor per distance unit
Nonroad vehicle N2O and CH4 emission calculation
For nonroad vehicles, the following equation is used to calculate N2O and CH4 emissions:
Emissions = Fuel × EF5
Here's an explanation of the equation:
- Emissions = Mass of CH4 or N2O that is emitted
- Fuel = Volume of fuel that is combusted
- EF5 = CH4 or N2O emission factor per volume unit
For information about emission factors, see Appendix A of the EPA reference document that was provided at the beginning of this section.
Fugitive emissions
Microsoft Sustainability Manager follows the EPA methodology for using the screening method to estimate scope 1 fugitive emissions from refrigeration, air conditioning, and fire suppression equipment. After the emissions are calculated, they're multiplied by the global warming potential (GWP) for the relevant refrigerant. You can find the GWP for different refrigerants in the tables in the following EPA reference document.
EPA reference document: Greenhouse Gas Inventory Guidance: Direct Fugitive Emissions from Refrigeration, Air Conditioning, Fire Suppression, and Industrial Gases (EPA.gov)
Screening method
The screening method relies on equipment-specific emission factors. Therefore, there's one screening method for refrigeration and air conditioning equipment, and another for fire suppression equipment. Because of the uncertainty in this method, an organization should use one of the other methods if it determines that fugitive emissions are significant.
Refrigeration and air conditioning equipment
Equation 1: Estimated emissions from installation
The following equation is used to estimate emissions from the installation of refrigeration and air conditioning equipment:
Emissions from installation = CN × (k ÷ 100)
Here's an explanation of the equation:
- CN = Amount of refrigerant that was charged into the new piece of equipment
- k = Assembly losses as a percentage of the amount that was charged
Equation 2: Estimated emissions from operation
The following equation is used to estimate emissions from the operation of refrigeration and air conditioning equipment:
Emissions from operation = C × (x ÷ 100) × T
Here's an explanation of the equation:
- C = Refrigerant capacity of the piece of equipment
- x = Annual leak rate as a percentage of the capacity
- T = Time in years that the piece of equipment was used during the reporting period (For example, T equals 0.5 if the equipment was used during half the reporting period and then disposed.)
Equation 3: Estimated emissions from disposal
The following equation is used to estimate emissions from the disposal of refrigeration and air conditioning equipment:
Emissions from disposal = CD × (y ÷ 100) × (1 – z ÷ 100)
Here's an explanation of the equation:
- CD = Refrigerant capacity of the piece of equipment that is being disposed of
- y = Percentage of the capacity that remains at the time of disposal
- z = Percentage of the refrigerant that is recovered
Fire suppression equipment
Emissions from fixed systems are assumed to be 2.5 percent (0.025) of the total capacity of the units for each gas. Emissions from portable equipment are assumed to be 3.5 percent (0.035) of the total capacity of the units for each gas.
