I. The Statute

Title V of the Clean Air Act, codified at 42 U.S.C. § 7661a, provides that it is unlawful for any person to operate a major source except in compliance with a permit issued by the permitting authority. The statute defines a “major source” at 42 U.S.C. § 7661(2): generally, any stationary source with the potential to emit 100 tons per year or more of any air pollutant. The Clean Air Act specifies that any air pollution source with emissions of 100 tons per year or more must obtain a Title V permit, a single document incorporating all of the myriad air pollution requirements to which the source is subject.¹

The phrase “any air pollutant” has been litigated to the highest court in the land. In 2007 the Supreme Court held that greenhouse gases are air pollutants under the Act. The agency followed with its endangerment finding. Once the agency regulated greenhouse gases under one section of the Act, the permitting provisions of the statute were, by the agency’s own reading, triggered for every source emitting those gases above the statutory thresholds: 100 tons per year for Title V operating permits, 100 or 250 tons per year for Prevention of Significant Deterioration preconstruction permits, depending on the source category.²

The arithmetic that follows is the agency’s own. It is not disputed by the agency. It is, in fact, the reason the agency spent the better part of a decade explaining why the statute cannot mean what it says.

II. The Source

The source is the domestic cow, Bos taurus, a ruminant. The rumen is a large fermentation chamber populated by billions of microbes, including bacteria, archaea, fungi, and protozoa, that break down fibrous plant material the animal could not otherwise digest. This microbial digestion produces methane as a byproduct, which is expelled through eructation. The trade term is burping. Contrary to popular imagination, enteric fermentation emissions are about 95 percent belching, not flatulence. The source has no stack, no baghouse, and no continuous emissions monitoring system. The monitoring system is the nose of anyone downwind.³

The unit emissions are quantified. The Intergovernmental Panel on Climate Change’s default emission factor for dairy cattle in North America, under the 2019 refinement to the 2006 guidelines, is 138 kilograms of methane per head per year. The Environmental Protection Agency’s own methane overview states that methane traps 28 times more heat than carbon dioxide over 100 years. One dairy cow therefore emits the carbon-dioxide equivalent of 3.86 metric tons per year: 138 kilograms times 28, divided by 1,000. The University of Nebraska places observed output at 150 to 600 liters of methane per cow per day.⁴

Divide 100 by 3.86 and the threshold resolves to 25.9 animals. Twenty-six dairy cows, operating as a single stationary source, emit more than 100 tons per year of a regulated air pollutant. The dairy down the road with a hundred head emits nearly 400 tons. The operation with 2,500 head emits 9,660 tons, or ninety-six times the statutory threshold. The statute’s number is 100. The numbers are not close.

III. The Plume

The emissions are not theoretical, modeled, or estimated from a single animal multiplied by a herd count, though the agency’s inventory does exactly that. They are visible from orbit. In February 2022, satellites operated by the environmental data firm GHGSat detected methane plumes rising from a single cattle feedlot in California’s San Joaquin Valley, the first time bovine burps had been measured from space. The detected rate ranged from 977 to 1,472 pounds of methane per hour; sustained for a year, the single feedlot would release 5,116 tons of methane, enough, if captured, to power more than 15,000 homes.⁵

Consider the regulatory posture of a source whose plume is detectable from low Earth orbit. The satellite can pinpoint the facility. The permitting authority cannot produce the permit, because none exists. The plume is measured in tons per hour. The permit file is measured in pages: zero.

IV. The Scale

The national inventory is compiled by the agency itself. As of January 1, 2024, there were 87.2 million head of cattle and calves on United States farms, according to the Department of Agriculture’s National Agricultural Statistics Service, the lowest inventory since 1951. Of these, 9.36 million were milk cows. The EPA’s Inventory of U.S. Greenhouse Gas Emissions and Sinks attributes 192.6 million metric tons of carbon-dioxide-equivalent emissions to enteric fermentation in 2022 alone. Methane from enteric fermentation and manure management together represented 36.6 percent of all methane emissions from human activity in the United States that year. Agriculture as a whole accounted for 9.4 percent of total gross U.S. greenhouse gas emissions.⁶

The sources are consolidating, which is to say the individual unpermitted major sources are getting larger. According to the 2022 Census of Agriculture, 24,094 American farms sold milk that year. The 2,013 farms with 1,000 or more cows accounted for 66 percent of all milk sales. The 834 farms with more than 2,500 cows each operate, by the IPCC’s own factor, at roughly 9,660 tons of carbon-dioxide-equivalent per year from enteric fermentation alone, before counting a single ton of manure methane, before counting a single ton of nitrous oxide, before counting anything at all from the other 86 million head of cattle in the country.⁷

V. The Absurd Result

The agency saw the arithmetic coming and said so, in writing, at length. When the agency promulgated its Greenhouse Gas Tailoring Rule in June 2010, it confronted the plain consequence of applying the statute’s 100- and 250-ton thresholds to greenhouse gases: instead of 300 new Prevention of Significant Deterioration permit applications per year, there would be 40,000. Instead of 11,000 sources subject to Title V permitting nationwide, there would be 6,000,000. The agency’s regulatory impact analysis estimated that, under its tailored thresholds, over six million sources of greenhouse gas emissions would be allowed to operate without a Title V operating permit, representing 95 percent of the total number of stationary sources.⁸

The agency named the unpermitted by category. Its tailoring proposal cited “full regulatory coverage of schools, hospitals, small farms, and restaurants” as the consequence of following the statute. Small farms. The agency’s own example of the absurd result was the farm. The agency estimated that adding 6.1 million permit applications to the 14,700 that permitting authorities then handled would “completely overwhelm” them. Out of what it called administrative necessity, and invoking the legal doctrine of absurd results, the agency set new thresholds of its own choosing: 75,000 tons per year of carbon-dioxide-equivalent in the first step, 100,000 tons in the second.⁹

The statute says 100 tons. The agency wrote 100,000. The multiplier is one thousand. The agency did not amend the statute. It could not. It simply announced that the statute’s numbers would not be enforced against 95 percent of the sources the numbers describe, and called the announcement a rule.

VI. The Cow Tax

The arithmetic escaped into public before the Tailoring Rule was written. On July 30, 2008, the agency issued an Advance Notice of Proposed Rulemaking on regulating greenhouse gases under the Clean Air Act. The Department of Agriculture responded with a comment observing that defining greenhouse gases as air pollution could require the agency to issue permits to farmers for their livestock. The Department indicated that farms with more than 25 dairy cows or 50 beef cattle would need permits for each ton of methane their animals emitted. The American Farm Bureau Federation, assuming a permit price of approximately $45 per ton, calculated the cost at $175 per dairy cow, $87.50 per beef cow, and $20 per hog. A medium-sized dairy farm with 75 to 125 cows would owe between $13,000 and $22,000 per year.¹⁰

Note the Department’s threshold: 25 dairy cows. The Department of Agriculture, performing the agency’s own arithmetic one year before the agency published its own, arrived at 25.9 and rounded down. The Department agreed with this investigation’s math. The episode acquired a name, the “cow tax,” and a bipartisan bill, introduced by Senators Thune and Schumer, to prohibit the agency from imposing Title V operating permits on agricultural operations. In December 2008 the agency announced it would not charge the fee. The permits were never issued. The emissions continued.¹¹

VII. The Reproof

The Tailoring Rule reached the Supreme Court, and the Court was not amused. In Utility Air Regulatory Group v. EPA, 573 U.S. 302 (2014), Justice Scalia, writing for the Court, held that the Act “neither compels nor permits” the agency to require a source to obtain a Prevention of Significant Deterioration or Title V permit on the basis of its greenhouse gas emissions alone, and that the agency’s rewriting of the statutory thresholds was impermissible: “An agency has no power to ‘tailor’ legislation to bureaucratic policy goals by rewriting unambiguous statutory terms.” The opinion continued: “It is hard to imagine a statutory term less ambiguous than the precise numerical thresholds at which the Act requires PSD and Title V permitting. When EPA replaced those numbers with others of its own choosing, it went well beyond the ‘bounds of its statutory authority.’”¹²

The Court described the agency’s posture with unusual color. In the Tailoring Rule, the agency had asserted, in the Court’s words, “newfound authority to regulate millions of small sources—including retail stores, offices, apartment buildings, shopping centers, schools, and churches—and to decide, on an ongoing basis and without regard for the thresholds prescribed by Congress, how many of those sources to regulate.” The Court declined the invitation: “We are not willing to stand on the dock and wave goodbye as EPA embarks on this multiyear voyage of discovery. We reaffirm the core administrative-law principle that an agency may not rewrite clear statutory terms to suit its own sense of how the statute should operate.”¹³

The holding cuts both directions, and the investigation reports both. The Court held the statute does not permit the agency to demand Title V permits for greenhouse gases alone, which is why no cow holds one. The Court also held the agency may not rewrite the numbers, which is why the Tailoring Rule that spared the cows was itself unlawful. The statute says 100 tons. The agency said 100,000. The Court said the agency may say neither, and the cows, unmentioned in the opinion, went unpermitted all the same.

VIII. The Rider

Congress, watching this unfold, chose the most direct instrument available: the power of the purse. Beginning with the fiscal year 2010 appropriations, Public Law 111-88, Title IV, Section 424, and renewed in every EPA appropriations act since, Congress has provided that none of the funds made available in the act or any other act may be used to promulgate or implement any regulation requiring the issuance of permits under Title V of the Clean Air Act for carbon dioxide, nitrous oxide, water vapor, or methane emissions resulting from biological processes associated with livestock production. A companion provision bars the agency from implementing mandatory reporting of greenhouse gas emissions from manure management systems.¹⁴

Read the list of covered gases again: carbon dioxide, nitrous oxide, water vapor, or methane. Water vapor. Congress barred the agency from spending a dollar to permit water vapor from livestock, a substance no one proposed to permit, out of what can only be described as an abundance of caution. The rider’s phrasing, “in this or any other Act,” extends the prohibition beyond the appropriations cycle in which it appears. It has been reenacted, in substance, for sixteen consecutive fiscal years.¹⁵

The legal position of the American dairy cow is therefore the following. The Clean Air Act requires a permit for every major source. The cow is a major source by a factor of four at twenty-six head and a factor of ninety-six at 2,500 head. The agency rewrote the threshold by a factor of one thousand and was told by the Supreme Court that it lacked the power to do so. Congress then prohibited the agency from enforcing the original threshold against the cow specifically, by name, in sixteen consecutive appropriations acts. No permit has been applied for. No permit has been issued. No permit can be issued, because Congress will not pay for the paper it would be printed on.

IX. The Penalty

The price of operating a major source without a Title V permit is set by statute and adjusted for inflation. Under 42 U.S.C. § 7413(b), civil penalties for Clean Air Act violations run to $25,000 per day per violation as enacted; the agency’s January 2025 inflation adjustment rule sets the current maximum at $124,426 per day per violation. Each day of unpermitted operation is a separate violation. Each source is a separate violator.¹⁶

Apply the schedule to the national herd. The 2,013 American dairies with 1,000 or more cows each emit roughly 3,860 tons of carbon-dioxide-equivalent per year from enteric fermentation alone, thirty-eight times the statutory threshold, every day of every year. At $124,426 per day per violation, a single large dairy accrues a theoretical maximum penalty exceeding $45 million per year of unpermitted operation. Across the 834 dairies with more than 2,500 head, the theoretical exposure runs into the tens of billions annually. The penalties are theoretical because the permits are forbidden, the enforcement is barred, and the violators are ruminants. The statute does not know this. The statute knows only tons.

X. Conclusion

Title V of the Clean Air Act, 42 U.S.C. § 7661a, requires every major source with the potential to emit 100 tons per year of any air pollutant to hold an operating permit. The IPCC’s default emission factor puts a single North American dairy cow at 138 kilograms of methane per year. Methane traps 28 times more heat than carbon dioxide over a century. One cow emits 3.86 metric tons of carbon-dioxide-equivalent per year; twenty-six cows exceed the statutory threshold. The EPA’s own inventory attributes 192.6 million metric tons of carbon-dioxide-equivalent to enteric fermentation in 2022, 36.6 percent of the nation’s methane from human activity. The agency’s Tailoring Rule conceded that the statutory thresholds would sweep in six million sources including small farms, rewrote 100 tons as 100,000, and was told by the Supreme Court in Utility Air Regulatory Group v. EPA that an agency has no power to tailor legislation to bureaucratic policy goals by rewriting unambiguous statutory terms. Congress has barred the agency from issuing the permits in every appropriations act since fiscal year 2010.

The cow burps 150 to 600 liters of methane per day, 95 percent of it through the mouth, in plumes visible from orbit. It holds no Title V permit. It has never applied for one. Under current law, it never will.

No cow in America holds a Title V operating permit.

Ergo.