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Flight: CO2 emissiefactoren 🇳🇱

💡 High-Level Description:

CO2-emissiefactoren is a distinguished methodology originating from the Netherlands, designed to provide accurate emission factors across various sectors, including passenger aviation. With a focus on delivering clear and precise carbon metrics, the methodology is widely adopted by European stakeholders, offering them a reliable system for understanding and mitigating the carbon footprint of their activities.

Within the aviation sector, CO2-emissiefactoren's approach stands out for its ability to consider multiple factors, such as aircraft type, engine specifications, distance traveled, and fuel efficiency. The methodology is continually updated to reflect the latest research and technological developments, ensuring that the carbon calculations remain both current and comprehensive. By offering detailed insights into the carbon impact of air travel, CO2-emissiefactoren equips airlines, policymakers, and travelers with the tools necessary to make more sustainable choices in the aviation industry.

Versioning: Use methodology_version to pin a published factor year — "2020" for flights in 2020 and 2021, "2022" for flights from 2022 onward. If you omit it, SQUAKE picks the year from departure_date; if neither is given, the latest version is used. See Versions below.

Sample API Requests

A. Without audit mode (for pre-booking/quotes)

{
  "expand": ["items"],
  "items": [
    {
      "audit": false,
      "type": "flight",
      "methodology": "CO2-EMISSIEFACTOREN-NL",
      "external_reference": "string",
      "origin": "MIL",
      "destination": "ORY",
      "booking_class": "first",
      "energy_scope": "wtw",
      "number_of_travelers": 1,
      "radiative_forcing_index": true
    }
  ]
}

B. With audit mode (for finalized/post-booking calculations)

Note: audit_for is optional. Provide when calculating on behalf of a specific Auditable entity; otherwise omit.

Defaults

  • "booking_class": "average"

  • "radiative_forcing_index": true

  • "energy_scope": "wtw"

  • "methodology_version": resolved from departure_date, or the latest version if no date is given

API request items

  • "type": "flight" (required)

  • "methodology": "CO2-EMISSIEFACTOREN-NL" (required)

  • "methodology_version": The published factor year. Supported: 2020 (flights in 2020 and 2021) and 2022 (flights from 2022 onward). Optional; if omitted, the year is taken from departure_date, falling back to the latest version. See Versions below.

  • "departure_date": The date of departure in YYYY-MM-DD format. Used to select the factor year when methodology_version is omitted.

  • "external_reference": A unique identifier that helps you link the resulting emissions to the requested item. Especially useful if multiple items are requested since SQUAKE cannot guarantee to keep the same order. The maximum length is 128 characters.

  • "booking_class": If you don't pass a booking_class, then fare_class and airline are highly recommended. SQUAKE will then automatically resolve the correct booking_class. For CO2-EMISSIEFACTOREN-NL, this is optional with average as the default value. Values are first, premium_economy, economy, or business.

  • "number_of_travelers": Minimum value is 1. The default value is 1.

  • "origin": For airports use IATA/ICAO code (format: ^[A-Z]{3,4}$, e.g. "MUC"), for other locations used in trade and transportation use UN/LOCODE codes (format: ^[A-Z]{2}\W?[A-Z2-9]{3}$, e.g. "DEHAM"). You can also pass lat/long (format: ^[-+]?\d{1,3}\.\d{1,10}\s?,\s?[-+]?\d{1,3}\.\d{1,10}$, e.g. "+40.712,-74.006").

  • "destination": For airports use IATA/ICAO code (format: ^[A-Z]{3,4}$, e.g. "MUC"), for other locations used in trade and transportation use UN/LOCODE codes (format: ^[A-Z]{2}\W?[A-Z2-9]{3}$, e.g. "DEHAM"). You can also pass lat/long (format: ^[-+]?\d{1,3}\.\d{1,10}\s?,\s?[-+]?\d{1,3}\.\d{1,10}$, e.g. "+40.712,-74.006").

  • Multi-leg itineraries: use routing (hyphen-separated airports) instead of origin/destination — see Flight: Routing (multi-leg).

  • "distance_in_km": Prioritized over origin and destination. If you don't have a distance_in_km, you can use origin and destination and the distance will be automatically resolved. If you pass both distance_in_km and origin/destination, then distance_in_km will be used. When routing is set, per-leg computed distances apply; see Flight: Routing.

  • "fare_class": The combination of fare_class and airline is mutually exclusive with booking_class. This is a single letter, e.g., Y, J, etc.

  • "radiative_forcing_index": Controls if a multiplier that factors in gases emitted to the atmosphere when flying at altitude should be applied. The default value is true.

  • "airline": The IATA Designator of an airline, e.g., LH. Airline names are also supported, SQUAKE will then automatically resolve it.

  • "energy_scope": Values are ttw or wtw. The default value is wtw.

  • "sustainable_fuels": Indicates the usage of sustainable fuels. This lowers the computed emissions in SQUAKE but is not part of the current official emissions frameworks.

  • "carbon_reduction_percentage_of_total": The percentage of emissions reduction through the usage of sustainable fuel. The minimum value is 0, and the maximum value is 1. Default value is 0.

  • "audit": boolean (optional). Set to true to create immutable audit records for finalized calculations. Must be enabled for your account.

Sample API Response

Versions

CO2-emissiefactoren publishes flight factors per vintage. SQUAKE supports two:

Version
Applies to
Notes

2020

Flights in 2020 and 2021

Factors are published per haul band only — no travel-class split

2022

Flights from 2022 onward

Factors are published per travel class and haul band

SQUAKE picks the version in this order:

  1. An explicit methodology_version, if you send one. This always wins, even when it disagrees with departure_date.

  2. The year of departure_date, if no version was sent. A flight on 2020-05-01 or 2021-11-30 uses the 2020 factors; a flight on 2023-02-14 uses the 2022 factors.

  3. The latest version, if neither is given.

A year that has no factor set of its own resolves to the most recent earlier year — 2021 resolves to 2020, and 2023 and later resolve to 2022. Years before 2020 are rejected with an invalid_methodology_version error.

The version actually used is returned as methodology_version on each item when you request "expand": ["items"], so a calculation stays reproducible:

Note: the 2020 factors have no travel-class dimension, so booking_class (and the fare_class + airline pair) does not change the result for flights priced with that version. Audit records for those calculations report the travel class actually priced, average.

For more details about RFI: Radiative Forcing Index

Bibliography

  • Lijst emissiefactoren (2025). CO2 emissionfactoren. Retrieved from https://www.co2emissiefactoren.nl/

  • Milieu Centraal (n.a.). Retrieved from https://www.milieucentraal.nl/

  • Emissiefactoren van vliegverkeer in meer detail (Jan, 2022). MilieuCentraal. Retrieved from https://www.co2emissiefactoren.nl/wp-content/uploads/2022/01/37-MilieuCentraal-Emissiefactoren-van-vliegverkeer-in-meer-detail-2022-v1.1.pdf — factors for methodology_version 2022

  • Emissiefactoren van vliegverkeer (2020). MilieuCentraal. Retrieved from https://www.co2emissiefactoren.nl/ — factors for methodology_version 2020

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