xAI Installs Eight Converted Jet Engines to Power Its Colossus 2 Data Centre

The units are made by ProEnergy, a company based in Missouri, and each is built around a refurbished CF6-80C2 engine core, the model that powers Boeing 747s, according to the reports. Each unit is rated at 50 megawatts and runs on natural gas, giving the eight a combined capacity of about 400 megawatts. "If anybody's ever flown on a Boeing 747, it's the exact same aircraft engine," ProEnergy executive Landon Tessmer told a conference in Denver in September.

The setup shows how AI developers are building their own power plants rather than waiting for the grid, and what that costs in emissions. Under the state air permit issued on March 11, the ProEnergy units may emit up to 4 parts per million of carbon monoxide in their exhaust, double the limit for the plant's 33 other turbines. Their limit for volatile organic compounds, which contribute to smog, is 25% higher than for those turbines.

Together the two groups make up the 41 turbines Mississippi has permitted at the site. A state order dated July 30 says those turbines "will be the permanent power source" for xAI's computing operations, and it sets retirement dates for 69 portable turbines that MZX Tech, an xAI subsidiary, brought to the site.

The Southern Environmental Law Center appealed the permit in April on behalf of the NAACP and two local groups. They argue that regulators should have required xAI to secure offsets, meaning pollution cuts at other nearby sources. A study cited by the law centre found that fine particulate pollution from the plant would raise health risks for nearby families. Electricity generation "should be getting cleaner over time, not dirtier," Patrick Anderson, a senior attorney at the centre, told the Times.

The Times also reported that ProEnergy has provided "no guarantees or documents" showing that the units meet emissions limits for pollutants such as formaldehyde. Using 2020 census data, the paper counted more than 100,000 people living within five miles of xAI's sites along the state line.

The Portable Turbine Lawsuit

A separate NAACP lawsuit over the 69 portable turbines is still alive. On October 30, US District Judge Debra M. Brown denied the companies' motion to dismiss, ruling that the turbines are not exempt as "mobile sources". State regulators had treated them that way in a July 2025 letter. The Justice Department moved in June to intervene and have the case dismissed on national security grounds. Brown allowed the intervention on October 19 but refused to dismiss the case.

"Our position has been clear: xAI cannot operate gas turbines without the required permits," Abre' Conner, the NAACP's director of environmental and climate justice, said in an October 30 release from the law centre.

Southaven Mayor Darren Musselwhite said the company had "complied with every federal, state and local law". The Mississippi Department of Environmental Quality declined to comment, citing the pending litigation. xAI is one of the technology companies that signed the White House's Ratepayer Protection Pledge in March, following President Donald Trump's call for tech firms to generate their own power.

Mississippi's Permit Board will hold an evidentiary hearing on the appeal on November 9 and 10. The public may attend but will not be able to comment.