Backup generators, monthly test-runs, and what a chronic new source adds to an airshed already overloaded.

We present each company's claim, then what the record adds. The counts below are working estimates where the exact figures have not been disclosed, and we flag which is which. Every claim traces to a named source.

The run-hour cap is what keeps the diesel banks from being a major polluter.

Edged's Atlanta facility runs Volvo Penta diesel generators. For the proposed Prichard site, MEJAC estimates as many as 15–25 generator units plus on-site diesel fuel storage, and expects it would require a "Synthetic Minor Source" air permit under the Clean Air Act. That permit category matters: a synthetic-minor source is one whose unrestricted emissions would cross the major-source line, but which accepts an enforceable cap on run-hours to stay under it. In other words, the run-hour cap is what keeps the diesel banks from being a major polluter.1,2

The independent evidence.

Backup diesel generators can emit 200–600 times more NOx than a natural-gas power plant per unit of electricity. A national review found nearly half of about 700 U.S. data centers sit in census tracts with above-median environmental burdens. Public-health modeling attributed roughly $6 billion in U.S. health damages to data-center-related air pollution in 2023, trending toward $20 billion and 600,000 asthma cases a year by 2028. In many regions the diesel runtime data centers are allowed "would trigger Clean Air Act violations in any other industry."2,3,4

Prichard and Calvert.

Prichard (Edged, ~6–8 MW). 15–25 units is MEJAC's working estimate; the exact count, ratings, fuel-storage volume, and run-hours are not yet disclosed. As of the June 11, 2026 community meeting the project was still at the pre-application stage. No ADEM air permit (or any other permit) had been filed, and Edged said it would hold off on permits until it had more neighbor buy-in. Every legally required public-comment point is still ahead.1,6

Calvert (Beacon, hyperscale). Beacon says the Calvert campus is "designed without backup diesel generators… no on-site emissions, smoke, or engine noise." If that holds, it is a real difference, from the Prichard proposal and from the company's own Kern County, California campus, which runs 15 × 2.5 MW of diesel. Two questions follow. First, what is the backup power for a round-the-clock hyperscale load, batteries, gas turbines, on-site generation, grid-only? None is disclosed. Second, "designed without" is a design intention, not a binding commitment: which permit or agreement would keep diesel off the site for its lifetime? No ADEM filing has surfaced either way.7,8