Selector

You can use an activity ID for the particular activity you are interested in. As activity IDs can refer to multiple emission factors, you use the other metadata fields that earthemission provides to filter down to those most suitable for your use case.
You can use a unique ID which will always refer to the same emission factor Using Activity ID Emission factors can be queried by specifying a data version, an activity ID and a set of optional attributes. If more than one emission factor match the filtering criteria, the one from most recent year will be selected, followed by the most conservative (e.g. highest) if there is more than one available for the most recent year.

Attribute	Required	Description
data_version	required	The required Data Version string for this request.
activity_id	required	An ID describing the activity that to search for. Multiple emission factors can share the same activity_id, e.g., if they are from a different source or apply to a different region.
source	optional	Emission factor data source name.
source_dataset	optional	The name of the dataset the source published this emission factor under.
region	optional	Geographic region to which the emission factor applies.
region_fallback	optional	Set this to true if you're willing to accept a less specific geographical region than the one you've specified. earthemission will then attempt to fall back to the larger region if it does not find any emission factors with the initial region. Only one fallback can be specified at a time. Default is false.
year_fallback	optional	Set this to true if you're willing to accept a less specific year than the one you've specified. earthemission will then attempt to find an emission factor with a year as close as possible to the one you've provided. Only one fallback can be specified at a time. Default is false.
year	optional	The year in which the emission factor is considered most relevant, according to the source.
source_lca_activity	optional	The Life Cycle Assessment (LCA) activity to which this factor is associated.
calculation_method	optional	The calculation method that will be used to calculate the CO2e emission factor. Learn more about calculation methods here.
allowed_data_quality_flags	optional	A list of data quality flags that you are willing to allow for this estimate. See the guide on data quality flags for more information and defaults. You can supply an empty list [] if you only want to accept emission factors without detected data quality issues.

A selector for one a specific activity, with additional filtering criteria can look like this:

"emission_factor": {
    "data_version": "^3",
    "activity_id": "electricity-supply_grid-source_production_mix",
    "source": "MfE",
    "region": "NZ",
    "year": 2020
}

Using ID

Every emission factor has a unique ID, and if we update an emission factor in a new data version, it gets a new ID, so by using an ID as your selector, you can assure that you get consistent results. This could be useful for audit purposes.

Attribute	Required	Description
id	required	An unique ID for one particular emission factor.
calculation_method	optional	The calculation method that will be used to calculate the CO2e emission factor. Learn more about calculation methods here.

A selector for one specific emission factor, using the unique id for that emission factor can look like this:

"emission_factor": {
    "id": "da80d5f9-7fb2-4cd7-aa45-781479499845",
}