Michael Ash, PERI, releases new Greenhouse 100 Suppliers Index tracking corporate fossil fuel emissions

Researchers at the University of Massachusetts Amherst Political Economy Research Institute (PERI) today published a new Greenhouse 100 Suppliers Index, ranking the largest corporate contributors to greenhouse gas emissions from fossil fuel supplies.

The index identifies Marathon Petroleum, Phillips 66, Exxon Mobil and Valero Energy as the top four suppliers. Each produced fossil fuels resulting in more than 250 million metric tons of carbon dioxide-equivalent emissions. Marathon Petroleum, Exxon Mobil and Phillips 66 also process natural gas.

The next two companies—Core Natural Resources, formed by the merger of Arch Resources and CONSOL Energy, and Peabody Energy—rank highly due to coal mining operations. Rounding out the top 10 are Chevron, Enterprise Products Partners, PDVSA (Petróleos de Venezuela S.A.) and PBF Energy. Together, these 10 fossil fuel suppliers account for 44% of greenhouse gas emissions from fossil fuels in the U.S. economy.

The index reports 2023 greenhouse gas emissions resulting from oil, natural gas and coal supplies using the latest—and possibly last—data available from the U.S. Environmental Protection Agency’s Greenhouse Gas Reporting Program. In September 2025, the agency announced its intention to end most of the program and suspend remaining reporting requirements until 2034.

“The Greenhouse 100 Index informs consumers, shareholders, regulators, lawmakers and communities about corporate releases of climate-altering pollutants into our environment,” says Professor Michael Ash, co-director of PERI’s Corporate Toxics Information Project. “The EPA decision to effectively end the Greenhouse Gas Reporting Program removes access to vital public information and leaves public and private decision-makers flying in the dark or relying on a patchwork of voluntary and potentially cherry-picked or greenwashed reports.”

The Greenhouse 100 Suppliers rankings represent the first comprehensive database of corporate responsibility for greenhouse gas emissions and potential liability for resulting climate damage.

The free, open-access online search tool includes all 778 companies reporting to the EPA’s Greenhouse Gas Reporting Program, including privately held companies, such as Koch Industries, which ranks No. 11 on the Suppliers Index, with more than 100 million metric tons of CO2-equivalent releases. It also features state rankings and reports detailing the companies and facilities responsible for each state’s fossil fuel supply. Texas, Louisiana, Wyoming, California and Illinois rank highest. Archives of earlier editions are available.

“In making this information available, we are building on the historic achievements of the right-to-know movement,” Ash adds. “Our goal is to engender public participation in environmental decision-making and to help residents translate the right to know into the right to clean air, clean water and a livable planet.”

The rankings draw on EPA data for oil and natural gas suppliers, combined with coal supplier data from the U.S. Energy Information Administration and the Mine Safety and Health Administration, using methods detailed in a peer-reviewed journal article. Coal suppliers were exempt from Greenhouse Gas Reporting Program requirements.

The PERI indexes track corporate environmental and environmental justice performance across U.S.-based industrial activity using uniform, mandated and comparable data, expanding federal facility-level reporting to the company level.

Top 10 Suppliers of Fossil Fuels in the U.S. (Reporting Year 2023)

Article originally published by UMass News.