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

The researchers identified 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 (about 275 million tons) of carbon dioxide-equivalent emissions.

The next two companies — Core Natural Resources, formed by the merger of Arch Resources and CONSOL Energy, and Peabody Energy — rank highly because of 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 U.S. greenhouse gas emissions.

The index reports 2023 greenhouse gas emissions resulting from oil, natural gas (methane), and coal supplies using the latest — and possibly last — data available from the Environmental Protection Agency’s Greenhouse Gas Reporting Program. Last September, the federal 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,” said 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 Index offers a free, open-access online search tool that 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 (about 110 million tons) of CO2-equivalent releases.

The online tool 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.

“In making this information available, we are building on the historic achievements of the right-to-know movement,” Ash said. “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.”