Methodology

Greenhouse gas emissions data has historically primarily been collected at the country level. The Carbon Majors Database was created by Richard Heede of the Climate Accountability Institute (CAI) to instead link these emissions to companies, or ‘Carbon Majors’. Carbon Majors originally selected extant companies from a variety of sources that met a ≥8MtCO₂/yr threshold. Some entities in the database do not exceed this threshold, for example, companies who met this threshold when this project started but have since shrunk, or smaller companies acquired by larger ones. However, this guideline still applies to ensure a manageable number of entities. The number of entities assessed varies due to mergers and acquisitions, as well as additions to the database.

The assessed entities are divided into three entity types: investor-owned companies, state-owned companies, and nation-state producers. Investor-owned companies include both publicly listed and privately held producers. Nation-state producers are used primarily in the coal sector and are included only when investor-owned or state-owned companies haven’t been established or played a minor role in the relevant country. Examples include North Korea and former Soviet states (the former Soviet Union and separately the Russian Federation, Kazakhstan, Ukraine, etc.). While current production is available for some Chinese coal entities, historic production data is unavailable and it has not been possible to verify the ownership structure of these entities, many of which are reportedly operated or directed by provincial government. Hence, China's coal production has been aggregated and reported as a nation state. State-owned companies are often partially owned by institutional or individual shareholders. These are considered state owned if more than fifty percent of shares are controlled by the state.

The database also tracks mergers and acquisitions. In such cases, the acquired companies’ emissions are attributed to the surviving company. Divestitures are inherently accounted for, as the production from divested assets will not be included in subsequent company disclosures (see Production Data below for further explanation). Assets that have been nationalized or expropriated are also monitored to the extent that equity-owned production is reported accurately by the relevant entities. Historically, breakups, such as that of the Standard Oil Trust, have also been accounted for. In this case, the multiple smaller companies into which the Standard Oil Trust was broken up have evolved to become some of the most recognizable companies in the database today. Some are direct descendants of Standard Oil, like ExxonMobil, with both Exxon and Mobil as descendants separately, and Chevron. Others have resulted from a merger with a descendant of Standard Oil, such as BP and ConocoPhillips.

Due to the importance of transparency in the Carbon Majors approach, self-reported production data by the producing entity is always preferred to and used instead of any other sources. This includes annual reports, company histories, SEC filings, operation reviews, website datasets on production, etc. However, in some cases, reputable third-party sources are used when self-reported data is unavailable, particularly for national companies that irregularly, inaccurately, or simply do not publish production data. Alternative, third-party sources include the U. S. Energy Information Administration (EIA), the Keystone Coal Industry Manual, the Oil & Gas Journal (especially the annual OGJ100/150 issues), and others.

For historical data, complete production records are sought and used where applicable. However, for some entities, production data is unavailable from the establishment of the entity, resulting in minor cases of underreporting, as early production is often overshadowed by later company expansions. This is especially true before the U.S. Securities Act of 1933, which required companies to provide full and accurate financial and operational information. Data gaps sometimes occur, often due to missing annual reports. In such cases, gaps in the data are filled through interpolation of surrounding data, while entity’s missing early production data is left empty.

Net production data is preferred, as gross production often includes output from joint ventures, production-sharing partnerships, or a state resource owner. While reporting gross production was common in the 1960s and early 1970s, it tends to overestimate emissions. In such cases, net production is estimated by applying a net-to-gross ratio. State-owned oil and gas companies typically report total production rather than their equity share. This practice can lead to a potential issue of double counting, where production is recorded both as overseas equity production by multinational oil and gas companies and as production by state-owned entities. To address this, collating data from third-party sources is utilized to adjust self-attributed production. This involves reducing total national production to a percentage representing the portion owned by the state.

Due to variations in how companies report production, the production data is standardized to a common commodity type, each with a standard unit: Oil & NGL (natural gas liquids) in million barrels, Natural Gas in billion cubic feet, and Coal in million tonnes.

To improve data accuracy, coal production is further categorized by rank, such as bituminous or anthracite, or by utilization, such as thermal or metallurgical. Preferably, coal rank data reported by the producing entity is used. However, coal rank is frequently reported in generic terms, but often with data on heat content. Using this information, along with the geographical locations of coal mines, enables coal rank categorization when entities fail to do so themselves. If this information is only available for specific years, this coal rank split may be applied to production data outside these years as an estimation.

Fossil Fuel Emissions

Emission factors for each fuel type are used to estimate the carbon content released when these fossil fuels are combusted. These emissions factors were mostly derived from Tier 1 defaults from the Intergovernmental Panel on Climate Change (IPCC) Guidelines for National Greenhouse Gas Inventories. Other sources, including the International Energy Agency (IEA), United Nations, EIA, US Environmental Protection Agency (EPA), and Carbon Dioxide Information Analysis Center (CDIAC), were also consulted.

These emissions factors were then modified by deducting net non-energy uses of each fuel. This is due to some proportion of the fuel produced being refined into products that effectively store carbon, such as various petrochemicals. Non-energy uses vary by a wide variety of factors, however like other global emissions databases, a common factor must be applied for non-energy uses associated with each fuel type. While this factor may be reasonably accurate on a global scale, it may not precisely represent each specific entity’s non energy uses.

Applying this factor to the standardized production results in the emissions from the combustion of marketed products, comprising nearly 90% of total emissions tracked by the database. These are Scope 3 Category 11 emissions, corresponding to "use of sold products", however this has been modified to quantify emissions from each fossil fuel company’s net production of oil, gas, or coal as opposed to sold products. This was done to avoid double counting, and deliberately excludes emissions from crude oil purchased from other producers, natural gas purchased for re-sale, or coal sold on behalf of other producers.

Emissions factors for the combustion of Oil & NGLs, Natural Gas, and Coal

Commodity	Carbon (kgC/unit)	Carbon Dioxide (kgCO 2 /unit)
Oil & NGL	101.4 kgC/bbl	371.4 kgCO2/bbl
Natural Gas	14.6 kgC/kcf	53.4 kgCO2/kcf
Lignite Coal	328.4 kgC/tonne	1,203.2 kgCO2/tonne
Sub-Bituminous Coal	495.1 kgC/tonne	1,814.1 kgCO2/tonne
Bituminous Coal	665.5 kgC/tonne	2,438.6 kgCO2/tonne
Anthracite Coal	715.4 kgC/tonne	2,621.5 kgCO2/tonne
Metallurgical Coal	727.4 kgC/tonne	2,665.4 kgCO2/tonne
Thermal Coal	581.0 kgC/tonne	2,128.9 kgCO2/tonne

Includes deduction for non-energy uses.

Four further direct Scope 1 emission types are then estimated:

• Flaring of CO₂ at oil and gas facilities, including various upstream and midstream facilities, relevant to oil and gas production.

• Venting of CO₂ from natural gas processing plants, also relevant to oil and gas production.

• Fugitive methane emissions from coal mines, oil extraction and storage, and gas production, processing, and transportation systems, applicable to oil, gas, and coal production.

• CO₂ emissions resulting from entity’s use of their own fuel, limited to gas production, primarily the difference between total gas produced and “gas available for sale”.

Emissions factors for the vented, flared, and fugitive carbon dioxide and methane, and the use of own fuel

Commodity	Combustion (kgCO2/tCO2)	Flaring (kgCO2/tCO2)	Venting (kgCO2/tCO2)	Fugitive Methane (kgCH4/tCO2)	Fugitive Methane (kgCO2e/tCO2)	Own Fuel Use (kgCO2/tCO2)
Oil & NGL	1000	15.94	3.83	1.92	53.86	-
Natural Gas	1000	1.74	28.53	9.88	276.59	57.26
Coal	1000	-	-	4.03	112.97	-

This analyses uses the IPCC AR5 100 year warming potential of 28 x CO₂ for methane.

Cement Emissions

Estimation of CO₂ emission for cement production differs from that for fossil fuel production. Cement-related emissions are estimated as a proportion of gross emissions reported by the major cement companies to the Cement Sustainability Initiative. This proportion of gross emissions estimates the process emissions from the calcining of limestone into clinker or Portland cement and excludes the emissions from fuel and electricity inputs, thus avoiding the double-counting of fuels from fossil fuels producers already accounted for in Carbon Majors. From these calculations, the database tracks the total emissions value in CO₂ equivalent units generated by each entity each year.

Global Fossil Fuel & Cement Emissions

This research compares the emissions tracked by the Carbon Majors database to total fossil fuel and cement emissions since the beginning of the Industrial Revolution in 1750. Data from the Carbon Dioxide Information Analysis Center (CDIAC), and more recently the Global Carbon Project, provides this total from 1750 to date. The CO₂ emissions figures obtained from the above calculations (excluding fugitive methane CO₂ equivalent emissions) are compared to this total to calculate entities' relative contributions to total global fossil fuel and cement emissions.

Units

Note - Metric prefixes are used, e.g., k for the multiplier 10³ or 1,000.

MtCO₂ – Million tonnes of carbon dioxide.

MtCO₂e – Million tonnes of carbon dioxide equivalent.

CH₄ - Methane

Bbl/bbls - Barrel or barrels.

Mbbl – Million barrels, the standard unit for Oil & NGL.

Bcf – Billion cubic feet, the standard unit for Natural Gas.

Kcf - Thousand cubic feet.

Mt – Million metric tonnes, the standard unit for Coal.