There are different methods for calculating carbon emissions, ranging from the most accurate direct measurements to the indirect methods, using emissions factors:

• Direct measurements: This method involves using monitoring equipment to measure the concentration and flow rate of GHG emissions in a facility or process. This provides the most accurate data, but it is also the most expensive.

The other methods uses emissions factors that correlate to emission sources:

• Fuel-based method: Using published emission factors for the specific fuel and vehicle type, and multiplying by the fuel consumption.
• Spend-based method: This method estimates emissions for goods and services by collecting data on the economic value of goods and services purchased and multiplying it by relevant secondary emission factors such as average emissions per monetary value of goods.

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Despite its reputation, a spend-based approach can be a powerful way to measure Scope 3 emissions. Read here more about the science behind spend-base methodology >>

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Although these methods are less accurate than direct measurements, they are less expensive and can provide useful data for many organizations. Here is detailed explanation of the deferent categories and Vert for each:

Scope 1

1. Stationary combustion - Fuel consumption to produce electricity, steam, heat, or power. The combustion of fossil fuels by boilers, diesel generators and other equipment emits carbon dioxide, methane, and nitrous oxide into the atmosphere. Therefor the data collection should include type of fuel, fuel Usage, and units for usage (volume, weight or energy). Fuel-based method: Each type of fuel has a different emission factor, Vert uses the UK DEFRA emission factors for the different fuels types. GHG emissions will be calculated based on the purchased quantities of fuels multiple by published emission factors. The calculation is as follows:

   $$ CO2e_{fuel} = Fuel Consumption * Emission Factor(fuel) $$

2. Mobile combustion - Burning of fossil fuels in mobile sources such as vehicles, aircraft, and ships, which are owned or controlled by the organization (unlike categories 4,6, and 7 from scope 3, which refer to traveling or shipping with public or 3rd party vehicles). For each combination of vehicle and fuel type there is an emission factor, that Vert gets from the GHG Protocol. Therefor the data collection should include type of vehicle and fuel consumption. The calculation is also by the fuel-based method as follows:

   $$ CO2e_{mobile} = Fuel Consumption * Emission Factor(fuel, vehicle) $$

3. Refrigerants - Refrigerant gases used in HVAC systems, chillers, and refrigerators can escape through leaks. When refrigerant gases are released into the atmosphere, they have harmful effects on the environment and contribute to global warming. To accurately calculate emissions, the amount of leaked refrigerant gas is assumed to be equal to the amount of gas replaced by the organization HVAC or chiller maintenance company. This information can be found in records or invoices from the maintenance company, includes the amount and type of refrigerant gas (such as Freon, R-22, HFC-134a, or CFC-12) replaced in the systems. This is called “Life-Cycle Stage Approach”. Vert uses the GHG Protocol emission factors for the different refrigerants types:

   $$ CO2e_{refrigerant} = RefrigerantTopup * Emission Factor(refrigerant) $$

4. Physical or chemical processing - Emissions that are generated during the production or treatment of chemicals and materials, such as cement, aluminum, adipic acid, ammonia manufacturing, and waste management, through physical or chemical means. This category need to be calculated according to the specific process, and is currently not supported in Vert

Scope 2

“GHG emissions from the generation of purchased electricity consumed by the company. Purchased electricity is defined as electricity that is purchased or otherwise brought into the organizational boundary of the company. Scope 2 emissions physically occur at the facility where electricity is generated.” (The GHG Protocol). 2 main categories of scope 2:

1. Purchased electricity - In Vert we use ‘market-base’ method, which uses the average emissions intensity of the electricity grid in the region where the company operates or consumes energy. Data required: Energy usage, units (kWh usually), country.
2. Purchased heat and steam - In Vert we use ‘spend-based’ method, by the specific country. Data required: Money spend, currency, country.

Scope 3

Scope 3 emissions refer to the indirect greenhouse gas (GHG) emissions that occur in a company's value chain. These emissions are generated from sources outside of the company's direct control, such as the production of purchased goods and services, transportation of products, and waste disposal.

For companies reporting their GHG emissions, it is becoming mandatory to include Scope 3 emissions when using the Greenhouse Gas Protocol (GHG Protocol) developed by the World Resources Institute (WRI) and the World Business Council for Sustainable Development (WBCSD).

Measuring Scope 3 emissions across these 15 categories can be complex, and companies often need to work with their suppliers, customers, and other stakeholders to gather the necessary data. However, it is an important step in understanding a company's full carbon footprint and identifying opportunities to reduce emissions across its value chain.