> For the complete documentation index, see [llms.txt](https://www.bilancarbone-methode.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.bilancarbone-methode.com/english/4-accounting/4.1-methode-de-quantification-des-emissions.md). # 4.1 - Emissions quantification method

Source : Freepik

[Accounting](/english/annexes/glossaire.md#comptabilisation) is defined as the process of collecting and processing the various data required to carry out a Bilan Carbone®. {% hint style="info" %} As a reminder, each emission source of the organisation that must be accounted for is estimated as follows: Emission from a source = [Activity data](/english/4-accounting/4.2-methode-de-collecte-des-donnees-dactivite.md) x [emission factor](/english/4-accounting/4.3-methode-de-selection-des-facteurs-demission.md) = [result](/english/4-accounting/4.5-profil-demission.md) ± [uncertainty](https://github.com/ABC-TransitionBasCarbone/methode-bilan-carbone/blob/translated-en/4-comptabilisation/4.4-methode-destimation-des-incertitudes) {% endhint %} The emissions that **must** be accounted for in a Bilan Carbone® are the emissions of the following gases, predominantly retained under the [Kyoto Protocol](/english/annexes/glossaire.md#protocole-de-kyoto): * Carbon dioxide, CO₂ * Methane, CH₄ * Nitrous oxide, N₂O * Sulphur hexafluoride, SF₆ * [Hydrofluorocarbons](/english/annexes/glossaire.md#h), HFC * [Perfluorocarbons](/english/annexes/glossaire.md#p), PFC * Nitrogen trifluoride, NF₃, not included in the Kyoto Protocol > :mag\_right: *These gases are conventionally taken into account within the* [*main standards*](/english/annexes/bibliographie.md#ressources-sur-la-comptabilisation)*, notably within the regulatory GES assessment, the CSRD, the ISO 14064-1 standard and the GHG Protocol (NF₃ is not mandatory for the latter).* However, a Bilan Carbone® **must also include** other GHGs (if these are emitted by the organisation and data allows), notably water vapour (H₂O) related to aircraft condensation trails where they exist, as well as other GHGs sometimes used as refrigerants, in fire extinguishers or in certain industrial processes (chlorofluorocarbons, bromofluorocarbons, etc.). A quantity of GHGs is expressed in a single unit, the "tonne of CO₂ equivalent" or tCO₂e (or possibly kgCO₂e, depending on the order of magnitude of the emissions). A conversion must therefore be carried out when different GHGs are emitted. The conversion is performed as follows: the various GHGs emitted are considered, and each quantity of GHG is multiplied by the 100-year global warming potential (GWP-100) of the GHG in question. These GWP-100 values are ratios: the radiative forcing associated with a given quantity of CO₂ over a period of 100 years is divided by the radiative forcing associated with the same quantity of the GHG in question over the same period.

Figure 4.1 : Radiative forcing (W/m²) over time (years) of one tonne of various GHGs, on a log-log scale. Source : D. Hauglustaine, LSCE

In the figure above, it can be observed that different GHGs have very different radiative forcings that evolve over time. Some GHGs, such as CF₄ or SF₆, remain in the atmosphere almost indefinitely and therefore have a high radiative forcing for thousands of years. Others, such as methane, have a radiative forcing that decreases significantly over the years (notably due to their lifetime coming to an end). {% hint style="info" %} These GWP-100 values are regularly updated by the [IPCC](/english/annexes/bibliographie.md#evolutions-climatiques) based on various scientific studies. {% endhint %} The emissions from all [identified emission sources](/english/2-scope-of-the-approach/2.4-perimetre-operationnel.md#identification-des-sources-demissions) must be accounted for in the Bilan Carbone®. Given the statistical nature of emission factors and sometimes also of activity data, the accounting of an organisation's GHG emissions remains an **estimate**, associated with an [uncertainty](https://github.com/ABC-TransitionBasCarbone/methode-bilan-carbone/blob/translated-en/4-comptabilisation/4.4-methode-destimation-des-incertitudes) inherent to the use of activity data and emission factors. In certain specific cases, and at the discretion of the organisation, it may also **measure** certain emissions, provided that the associated uncertainty is specified. Emissions from certain combustion processes can, for example, be measured using sensors. In order to obtain the most accurate and precise estimate possible, the organisation's objective should be to **minimise the uncertainties** associated with emissions. Each emission source must then be integrated within one of the [Bilan Carbone® categories](/english/4-accounting/4.5-profil-demission.md#profil-demission-au-format-bilan-carbone-r). The definitions of the categories, the emission sources they include, and the key accounting principles associated with them are detailed in the [Appendix](/english/annexes/annexes/annexe-1-grands-principes-de-comptabilisation-du-bilan-carbone-r.md). > :mag\_right: *For more practical information and examples, organisations are invited to consult the* [*Plan Carbone Général*](/english/annexes/bibliographie.md#plan-carbone-general)*, a reference operational guide that compiles:* > > * *Commonly useful data* > * *Data collection methods* > * *Commonly useful emission factors* > * *Explanations on the practical calculation of uncertainties* > * *Other practical advice on carbon accounting* > * *Sector-specific recommendations* *** *Do you have a question about the content?* [*Consult the FAQ*](/english/annexes/faq.md)*. The method is evolving and therefore subject to change (clarifications, additions): find the* [*change log here*](/english/readme/historique-et-suivi-des-modifications.md)*.* --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://www.bilancarbone-methode.com/english/4-accounting/4.1-methode-de-quantification-des-emissions.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.