The Role of Emission Factors in a GHG Inventory.

📊Activity Data

Let's start by defining a concept that is essential to understanding the FE: activity data.

This is a metric describing the activity of a company’s emission source. For example, the number of liters of diesel used for business travel, the number of kWh of electricity consumed, the office space in square meters, the number of computer monitors in the company, the number of t.km (metric tons per kilometer) traveled by carriers… The unit depends on the nature of the item in question and the category (or scope, depending on the method used) of the report to which it belongs.

These activity data indicate how the organization uses the emission source— for example , how it uses it or how many it has (depending on the unit in question). However, they do not indicate the carbon footprint (greenhouse gas emissions) resulting from this use. This is where the emission factor comes into play .

✖️A coefficient.

The emission factor is a coefficient that converts the activity data mentioned above into their actual greenhouse gas emissions. It provides the carbon footprint of that activity data.

It allows for the conversion of this data into CO2 equivalent (CO2 eq.) per unit of the activity in question. For example, the carbon footprint (CF) of a printer is expressed in kg CO2 eq./unit. According to ADEME’s Base Empreinte®, the CF of an inkjet printer is precisely 88 kg CO2 eq./unit. In a company’s GHG inventory, this means that owning one inkjet printer results in 88 kg CO2-eq in emissions; owning two printers results in 88 × 2 = 176 kg CO2-eq in emissions, and so on.

The FE for electricity consumption is expressed in kg CO2-eq./kWh, according to ADEME’s Base Empreinte®. The unit changes because the nature of the category changes; we are no longer talking about goods purchased and owned, but rather about energy consumption. For example, the carbon footprint of electricity consumption based on France’s average energy mix in 2022 is 0.0520 kg CO2 eq./kWh.

It’s important to note that the FE varies by region of the world. Using electricity in France does not have the same carbon footprint as using electricity in Japan or the United States, depending on each country’s electricity mix, for example.

🔬A Special Case: The PCF

It is interesting to examine a specific type of environmental indicator: the PCF (Product Carbon Footprint), or the carbon footprint of a product or service.
This is an environmental indicator that is equivalent to a single-criterionLife Cycle Assessment (LCA).

A life cycle assessment (LCA) evaluates the overall environmental impact (on biodiversity, water, GHG emissions, etc.) of products or services provided by a company throughout their life cycle, from design through production, use, and end of life. It is a multi-criteria analysis.

A PCF is a single-criterion LCA, with that criterion being greenhouse gas emissions, or its carbon footprint. It assesses the GHG emissions of the product or service at each stage of its life cycle and is broken down into three different life stages:

• Supplier emissions: emissions associated with the design and production of the product.
• Use: Emissions associated with the use of the product.
• End of life: emissions associated with the end of a product's life (its treatment as waste).

Thus, the “supplier output” FE will generally be used in the “Purchases” category of the balance sheet, while the “use” and “end-of-life” FEs will generally be used in the “Goods Sold” category, according to the Bilan Carbone® method (see definition).

A financial statement is, in fact, divided into several categories, or “scopes,” which may vary depending on the methods used.

The GHG Protocol methodology defines the three scopes:

• Scope 1: The company's direct emissions.
• Scope 2: The company's indirect emissions.
• Scope 3: the company's indirect emissions over which it has no control.

Subsequent methods divide emission sources into 6 categories:

• Direct Emissions
• Indirect Emissions
• Related toenergy⚡
• Transportation-related🚊
• Related to the products you purchased🛒
• Related to products sold💶
• Other indirect emissions.

These PCFs are calculated in accordance with ISO 14067 and can be requested directly from suppliers in order to calculate the GHG emissions resulting from the purchase of their specific products or services, rather than using average emission factors that could apply to any supplier.

Obtaining the PCF from your supplier allows you to calculate emissions more accurately, reduce uncertainty in the emissions inventory, and increase its robustness.

At Decarbo’Solution®, our module Décarbon’Achats® allows you to make this request to your suppliers, give them free access to the platform, and guide them through the process of completing their Carbon Footprint Assessment (CFA), in order to maximize the response rate and supplier engagement.

☁️“CO2-eq,” a unit for comparing greenhouse gases.

Let’s take another look at “CO2 equivalents, ” which are used to express emission factors. This unit of carbon accounting makes it possible to quantify the greenhouse gas (GHG) emissions generated by human activities. These GHGs include carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), among others.

In order to consistently compare the climate impact of each of these gases, it is necessary to convert these impacts into a common unit. The benchmark for comparison is their Global Warming Potential (GWP), which measures each gas’s impact on the climate relative to CO2. By using CO2’s GWP as a reference, emissions of each GHG are converted to “CO2 equivalents, ” allowing for a uniform assessment of their contribution to climate change.

〽️Physicalor monetary

One factor to consider is the nature of the emission factor: physical or monetary.

A physical emission factor represents the amount of CO2 emitted per unit of physical consumption, such as kWh, liters, or other units. It is therefore used to account for physical flows.

A monetary emission factor represents the amount of CO2 emitted per euro spent on the item in question and is expressed in kg CO2-eq./k€ (excl. tax). This is a significant methodological difference. While these factors make it possible to account for non-physical flows (such as the purchase of services), they are inherently less precise than physical factors, particularly because they depend on price fluctuations. One example is the highly volatile energy markets: the relevant emission factors will therefore be very sensitive to this volatility and are likely to change regularly.

It is recommended to use them only for certain categories in the balance sheet (such as purchases of goods or services by businesses), or when the actual data cannot be obtained.

❓Uncertainty

Uncertainty refers to the possible difference between the value assigned to the quantified quantity and the actual value. It is expressed either as a fixed value (5%, 15%, 30%, etc.) or as a range (for example, between 10% and 15% uncertainty) for a given confidence level. If the confidence level is 95%, then there is a 95% chance that the correct value lies within the given interval.

FE models have an inherent uncertainty, which may be due to several factors:

• Incomplete data: Certain measurements or data may not be available because the process is not yet recognized or the measurement method does not yet exist. This leads to an incomplete conceptualization of the emission factor.
• Lack of temporal representativeness: the data and/or the associated emissions calculations are outdated. This can introduce a bias.
• Complex models: Some models used to measure GHG emissions and removals can be very complex. Their use can introduce uncertainties for various reasons. Two examples are:
• These models are simplifications of real-world systems and are therefore not accurate.
• Alternative formulas may result in different estimates.
• Lack of reliability: Data may not be directly measurable, or it may simply not yet exist. In such cases, assumptions may be used as a substitute, or data may be extrapolated.
• Lack of technological representativeness: Emissions associated with a particular process cannot be measured and are therefore modeled using a similar process.
• Measurement error

Determining the value of emission factors is therefore relatively uncertain. The uncertainty surrounding emission factors ranges from 5% to 80% (for monetary emission factors).

The choice of an emission factor also affects the GHG inventory of a company ( whether industrial or commercial), along with its associated uncertainty. The overall uncertainty of an inventory is estimated based on the uncertainty of the selected factors and the available activity data. The more uncertain the selected factors are, the more uncertain the final inventory will be.

📂The various existing databases.

Emission factors (EFs) can be found in databases. Some are public, others require a fee, and still others are specific to GHG inventory tools. There are also databases for factors specific to certain sectors. Some examples include:

• ADEME 's Empreinte®database (public)
• The Ecoinvent database (subscription required)
• The INIES database for the construction sector
• The DEFRA database for the United Kingdom.

🤝Factors directly from suppliers

To obtain the most accurate and relevant emission factor possible regarding corporate purchases, the best approach is to get the emission factor directly from the source: the supplier.

By calculating its Product Carbon Footprint (PCF), the supplier will be able to assess the carbon footprint of its product and thus provide its corporate customers with the most accurate FE possible.

Choosing the right emission factors will thus ensure a high-quality GHG inventory, clearly identified emission sources, an accurately measured carbon footprint, and, consequently , effective measures to reduce that footprint.

Our carbon experts are available to provide a free of our platform, with no obligation. 🚀