Maryland’s highest court has reversed a lower court ruling that would have required Maryland regulators to clamp down on ammonia emissions released into the air outside chicken farms.
The case, Maryland Department of the Environment v. Assateague Coastal Trust, hinged on whether the state’s controls were adequate to address the compound’s potential threats to human health and water quality.

A 6-1 majority of the state Supreme Court ruled in an Aug. 9 opinion that regulators are addressing the air concerns through the state’s 2019 stormwater discharge permit. Although the permit mostly seeks to rein in pollutants in waterways, the MDE acknowledges and has used its authority to curb ammonia emissions on a case-by-case basis, Justice Brynja McDivitt Booth wrote.

“The Department’s decision to evaluate each [animal-feeding operation] individually and to require appropriately tailored best management practices to control these emissions where they present a real risk of discharge, is reasonable and falls within the discretion afforded to the Department by the Legislature under the State’s water pollution control law,” Booth stated.

The case had threatened to upend how the state regulates emissions from concentrated animal-feeding operations, particularly chicken farms on Maryland’s Eastern Shore. In 2021, a Montgomery County Circuit Court judge sided with Assateague Coastal Trust, an environmental group based on the Shore.

That lower court ruling held that the state must regulate ammonia released into the air because some of it falls as nitrogen into waters protected by the federal Clean Water Act, including the nearby Chesapeake Bay.

There, the nutrient in large enough quantities can wreak havoc in aquatic systems, feeding huge algae blooms. When those blooms die off, it can rob the water of oxygen, creating “dead zones.”
The state requires each farm to hire state-certified consultants to develop a plan to control nutrients tailored to each site. Each plan must include practices designed to offset all negative water-quality impacts. The Supreme Court agreed in its 96-page opinion with the state’s argument that its 2019 revised general permit gives officials authority to make farms install practices, such as leafy screens of bush and tree plantings, to filter airborne ammonia.

The chicken industry’s critics in the state lamented the reversal.

“This unfortunate decision by the Supreme Court of Maryland is a lost opportunity for the Chesapeake Bay cleanup effort,” said Eric Schaeffer, executive director of the Environmental Integrity Project. “Ammonia air pollution from the Chesapeake region’s poultry factory farms contributes about 12 million pounds of nitrogen pollution into the Bay every year, more than all the sewage and wastewater from Maryland or Pennsylvania.”

In a dissenting opinion, Justice Shirley Watts urged sending the case back to the circuit court level to determine whether the state’s water-oriented regulations sufficiently control air emissions on the farms. The permit’s language is silent on whether ammonia in the air is subject to regulation as a water pollution, she wrote.
The decision marked the third time since 2009 that Maryland's court system has rejected a challenge by the Assateague group to the state's general stormwater permit.

One of the region's top poultry trade groups hailed the latest rebuke.

“This is the third consecutive time these activists have tried and failed to persuade courts to overrule science-based, legally sound water quality regulations," said Holly Porter, executive director of the Delmarva Chicken Association, in a statement. "We're glad the Maryland Supreme Court recognized the challenge to the 2019 permit lacked merit and mischaracterized the law."