Fuel API

Calculate CO2e emissions from direct fuel combustion (Scope 1) for heating, generators, boilers, and stationary equipment.

Endpoints

Endpoint	Description
`GET /v1/fuel/emissions`	Calculate emissions for fuel combustion
`GET /v1/fuel/types`	List all supported fuel types

Calculate Emissions

<span class="api-method api-method-get">GET</span> /v1/fuel/emissions

Parameters

Parameter	Type	Required	Default	Description
`fuel_type`	string	Yes	-	Fuel type identifier (see table below)
`amount`	number	Yes	-	Quantity of fuel consumed
`unit`	string	No	Auto	Unit of measurement (fuel-specific, see below)
`include_wtt`	boolean	No	`true`	Include Well-to-Tank upstream emissions
`equivalents`	boolean	No	`false`	Include real-world equivalents

Example Request

curl "https://api.emissions.dev/v1/fuel/emissions?\
fuel_type=natural_gas&\
amount=15000&\
unit=kwh" \
  -H "Authorization: Bearer em_live_xxxxxxxxxxxx"

Example Response

{
  "data": {
    "type": "fuel_emission",
    "id": "c9f3a5b2-4d6e-5f7a-b8c9-0d1e2f3a4b5c",
    "attributes": {
      "emissions": {
        "co2e": 3106.1,
        "co2e_unit": "kg",
        "co2e_calculation_method": "ipcc_ar6_gwp100",
        "co2e_grams": 3106100,
        "breakdown": {
          "direct_co2e": 2747.4,
          "direct_co2": 2731.5,
          "direct_ch4": 5.4,
          "direct_n2o": 10.5,
          "wtt_co2e": 358.5,
          "unit": "kg"
        },
        "ghg_protocol_scopes": {
          "scope_1": 2747.4,
          "scope_3_category_3": 358.5
        },
        "source_trail": [
          {
            "data_category": "emission_factor",
            "name": "Natural Gas — 0.18316 kgCO₂e/kwh",
            "source": "DEFRA",
            "source_dataset": "Greenhouse gas reporting: conversion factors 2025",
            "year": "2025",
            "region": "GB",
            "region_name": "United Kingdom"
          }
        ]
      },
      "fuel": {
        "fuel_type": "natural_gas",
        "fuel_label": "Natural Gas",
        "fuel_category": "gaseous",
        "is_biofuel": false,
        "amount": 15000,
        "unit": "kwh",
        "emission_factor": 0.18316,
        "emission_factor_unit": "kgCO2e/kwh",
        "include_wtt": true
      },
      "notices": []
    }
  },
  "meta": {
    "methodology": "DEFRA 2025 - GHG Conversion Factors",
    "emission_factors_year": 2025,
    "standards_compliance": {
      "GHG_Protocol": "Scope 1 (Direct combustion)",
      "ISO_14064": "Part 1 - Organisation level"
    },
    "calculated_at": "2026-02-08T14:00:00Z"
  }
}

List Fuel Types

<span class="api-method api-method-get">GET</span> /v1/fuel/types

Get all supported fuel types with their available units.

Optional Parameters

Parameter	Type	Description
`category`	string	Filter by category: `gaseous`, `liquid`, `solid`, `biofuel`

Example Response

{
  "data": [
    {
      "fuel_type": "natural_gas",
      "label": "Natural Gas",
      "category": "gaseous",
      "is_biofuel": false,
      "available_units": ["kwh", "therm", "m3"],
      "default_unit": "kwh"
    },
    {
      "fuel_type": "diesel",
      "label": "Diesel (Gas Oil)",
      "category": "liquid",
      "is_biofuel": false,
      "available_units": ["kwh", "litre"],
      "default_unit": "litre"
    },
    {
      "fuel_type": "hvo",
      "label": "HVO (Hydrotreated Vegetable Oil)",
      "category": "biofuel",
      "is_biofuel": true,
      "available_units": ["litre"],
      "default_unit": "litre"
    }
  ],
  "meta": {
    "total_fuel_types": 16,
    "categories": ["gaseous", "liquid", "solid", "biofuel"],
    "source": "DEFRA 2025 - GHG Conversion Factors"
  }
}

Fuel Types

Gaseous Fuels

`fuel_type`	Label	Units	Default	Factor (kgCO₂e)
`natural_gas`	Natural Gas	kwh, therm, m3	kwh	0.18316/kWh
`lpg`	LPG	kwh, litre, kg	litre	1.5226/litre
`cng`	CNG	kwh, kg	kg	2.5400/kg
`biogas`	Biogas / Biomethane	kwh	kwh	0.00022/kWh

Liquid Fuels

`fuel_type`	Label	Units	Default	Factor (kgCO₂e)
`diesel`	Diesel (Gas Oil)	kwh, litre	litre	2.5121/litre
`petrol`	Petrol (Gasoline)	kwh, litre	litre	2.1019/litre
`kerosene`	Burning Oil / Kerosene	kwh, litre	litre	2.5403/litre
`fuel_oil`	Fuel Oil (Heavy)	kwh, litre	litre	2.9640/litre
`red_diesel`	Gas Oil (Red Diesel)	kwh, litre	litre	2.5121/litre

Biofuels

`fuel_type`	Label	Units	Default	Factor (kgCO₂e)
`biodiesel`	Biodiesel (B100 / FAME)	litre	litre	0.03461/litre
`hvo`	HVO	litre	litre	0.03820/litre
`bioethanol`	Bioethanol	litre	litre	0.02171/litre
`wood_logs`	Wood Logs	kwh, kg	kg	0.06150/kg
`wood_pellets`	Wood Pellets	kwh, kg	kg	0.07240/kg

Solid Fuels

`fuel_type`	Label	Units	Default	Factor (kgCO₂e)
`coal_industrial`	Coal (Industrial)	kwh, kg	kg	2.2530/kg
`coal_domestic`	Coal (Domestic)	kwh, kg	kg	2.8832/kg

Biofuel Methodology

Biofuel direct CO₂ emissions are classified as biogenic carbon and excluded from Scope 1 totals per GHG Protocol and DEFRA guidance. The co2e figure for biofuels represents only CH₄ and N₂O from incomplete combustion.

Well-to-Tank (WTT) upstream emissions are still significant for some biofuels — for example, bioethanol WTT is 0.618 kgCO₂e/litre.

The response includes a biofuel_biogenic_carbon notice whenever a biofuel is requested.

Gas-by-Gas Breakdown

Every response includes individual gas species:

Field	Gas	Description
`direct_co2`	CO₂	Carbon dioxide from combustion
`direct_ch4`	CH₄	Methane from incomplete combustion
`direct_n2o`	N₂O	Nitrous oxide from combustion
`direct_co2e`	CO₂e	Aggregated using IPCC AR6 GWP100

This is required for ISO 14064 compliance and detailed national inventory reporting.

Error Responses

Invalid Fuel Type

{
  "error": {
    "code": "invalid_fuel_type",
    "message": "Fuel type 'propane' not recognised. Available: natural_gas, lpg, cng, ...",
    "status": 422,
    "available_fuel_types": ["natural_gas", "lpg", "cng", "..."]
  }
}

Invalid Unit

{
  "error": {
    "code": "invalid_unit",
    "message": "Unit 'gallon' not supported for diesel. Available: kwh, litre",
    "status": 422,
    "available_units": ["kwh", "litre"]
  }
}