GHG Emissions Rankings

How we build these rankings

Every ranking on PlainCarbon is built from raw EPA Greenhouse Gas Reporting Program (GHGRP) submissions. Each U.S. facility emitting 25,000 metric tons of CO2-equivalent or more per year is required to file an annual return. We aggregate those filings up to the parent-company level using the GHGRP's "Parent Company" linkage so that a company operating dozens of facilities shows up once on a company ranking, not dozens of times.

Cumulative totals (used in the top-emitters ranking) sum every reporting year for which the EPA has finalized data, typically 2011 through the most recent completed year. This view is most useful for understanding which companies have the largest historical footprint in U.S. industrial reporting. Year-over-year reductions (used in the biggest-reducers ranking) compare the company's earliest reported year against its most recent reported year, calculated only for companies with at least three years of continuous reporting so that reduction figures reflect operational change rather than reporting boundary shifts.

What the rankings reveal

The largest cumulative emitters are dominated by integrated electric utilities, major refining companies, and petrochemical producers, the sectors that ran the largest U.S. industrial footprints during the 2010s. Coal-heavy utilities appear high on the top-emitters list and also high on the biggest-reducers list: these are companies that retired coal capacity and switched to natural gas or renewables over the past decade, so they show both a large historical total and a significant year-over-year decline. Reading the two rankings side by side is more informative than either in isolation.

Methane-specific rankings (in addition to combined CO2-equivalent) call out oil-and-gas systems and landfill operators where methane is the dominant gas. Methane's higher 100-year global warming potential (29.8 per the IPCC AR6 value used by EPA) means that even modest methane reductions show up as large CO2-equivalent reductions on the headline charts. The methane-only view decouples that lever, useful when evaluating sector-specific methane mitigation programs.

Verification and methodology

Every facility and company on a ranking links to its detail page, which in turn links back to the underlying EPA FLIGHT records and includes the company's sector mix, top facilities, and reporting-year coverage. Where a company's legal name has changed (mergers, divestitures, spin-offs), we use the GHGRP's current legal-entity name and note prior reporting names on the detail page so longitudinal comparisons remain traceable. Companies that exit the federal threshold (sell all reporting facilities or shut them down) drop off future rankings but remain in cumulative totals for the years they were active.

Industry sector classifications follow EPA subpart designations (Subpart D for electricity, Subpart W for petroleum & natural gas, Subpart H for cement, etc.), not NAICS economic codes. The two overlap substantially but are not identical; on each company page we surface the EPA subpart mix and link to NAICS where the company has registered one. This dual labeling keeps the rankings aligned with how the EPA itself organizes the dataset while preserving comparability to broader economic statistics published by the Census Bureau and Bureau of Labor Statistics.