The Trump administration is arguing that xAI should be allowed to continue using temporary, trailer-mounted gas-fired turbines to power its massive Colossus 2 data center in the Southeast because any delay in the development and training of the company’s Grok models would “directly [threaten] our ongoing national security interests.”
That’s according to the Justice Department’s intervention this week in a federal court case over whether those turbines — which xAI brought in last year to supplement its grid connection at the site — should be exempt from Clean Air Act permitting requirements.
The Department of War (formerly the Department of Defense) relies on xAI’s “Grok Gov” model for a range of military activities, the agency said in a filing, and offers features “that are found in no other frontier AI model.” During Operation Epic Fury, the initial strikes on Iran in early 2026 that kicked off a monthslong conflict that rattled global energy markets, xAI’s models enabled the U.S. to deploy more than 2,000 munitions to distinct targets within 96 hours, the filing continued. The agency uses almost 2 billion Grok tokens every day, it added — roughly the equivalent of 6 million pages of text being processed.
“If xAI is hindered from continuing to improve and upgrade Grok…DOW’s ability to meet its national security mission and keep pace with adversaries will be impaired,” the agency said.
The case is likely to be precedent-setting in the ongoing debate about how to permit behind-the-meter generation for data centers, which is becoming more popular as hyperscalers push to get the facilities online as quickly as possible. But it also comes at a time when scrutiny over electricity prices in the places where data centers are being built is at an all-time high.
Research firm Cleanview estimates that hyperscalers have announced 90 gigawatts of behind-the-meter generation projects in recent years, thanks in part to long timelines for grid connections and challenges with large turbine procurement.
The cost of speed to power
xAI has been rapidly expanding its footprint along the Tennessee-Mississippi border since 2024, when it began construction of Colossus 1 in Memphis, touting it as the world’s largest AI supercomputer. At the time, the site had an eight-megawatt grid connection, and the company added a dozen or so methane-fired turbines onsite to meet the remaining load.
In 2025, the company expanded further, installing at least 20 additional turbines to power its 100,000 GPUs.
The strategy got new computing power online in just 122 days. That speed, which dwarfed the pace of xAI’s developer competitors, sent shock waves through the data center industry, and also sparked immediate backlash over smog and noise pollution. By late 2025, xAI removed most of the temporary turbines after grid station upgrades delivered an additional 150 MW, leaving just a dozen or so permanent turbines on site for backup power.
In March, the Mississippi Department of Environmental Quality gave xAI permission to use trailer-mounted turbines temporarily at Colossus 2, to get the data center up and running until permanent turbines can be constructed.
When the NAACP, Earthjustice, and the Southern Environmental Law Center sued to block xAI’s use of the turbines this spring, they argued that the dozens of unpermitted turbines likely constitute the largest industrial source of nitrogen oxides in the greater Memphis area, increasing health risks in the nearby communities. A Clean Air Act permit, the parties said, would hold xAI to a higher standard when it comes to emissions control technologies.
xAI, for its part, maintains that it relied on the state of Mississippi’s determination that the portable turbines are “mobile” pollution sources, and therefore exempt from the permits required for stationary sources like power plants.
DOJ intervention
In January, the EPA closed a loophole that data center operators — including at xAI — had used to avoid standard air pollution reviews by classifying certain equipment as “non-road engines.” The updated rule clarified that such turbines aren’t exempt from the agency’s rules on stationary turbines, and must obtain Clean Air Act permits before operating.
That ruling, however, also opened a potential legal pathway for the EPA to adopt a new framework classifying backup generators as “mobile sources” rather than stationary sources, said policy research firm Capstone. If that happens, these generators would face fewer requirements, a boon for the speed to power efforts of hyperscalers and data center developers.
If xAI were to prevail in the lawsuit brought by the NAACP, Capstone added, it could also solidify a shortcut for other data center developers around the country to deploy off-grid fossil generation quickly.
At this point, however, DOJ’s intervention is unlikely to change the outcome of the xAI case, Capstone said. The agency is essentially positioning itself to argue against the EPA’s recent ruling, pitting DOJ against another federal agency. The federal court in Mississippi has ordered a hearing on NAACP’s move to block the turbine use for late August.
