Stratos at 9GW: the health bill for gas-fired AI compute

A health cost for gas-fired compute

The analysis was prepared by EmPower Analytics Group for NRDC. It models emissions from the proposed Stratos data center in Box Elder County, Utah, near Salt Lake City.

At full build-out the site would draw as much as 9GW of on-site power from burning methane gas.

At that scale, the report estimates air pollution from Stratos's gas generation could cause approximately 5 to 45 additional premature deaths and $75m to $690m in health-related economic damages every year. The main pollutant is fine soot, particulate matter of 2.5 microns or less. For host communities and regulators, that turns a power question into a permitting one: air permits and siting decisions become the place where on-site gas is argued, not the interconnection queue. For operators, the fastest route to power now arrives with a pollution bill attached. What nobody can say yet is whether Stratos gets built at 9GW, or whether the converted jet engines already running in Mississippi are a short bridge or a permanent fixture.

The choice of generator matters more than the headline number. Over 30 years at 9GW, the report estimates 856 to 1,350 premature deaths and $13.5bn to $20.7bn in damages under gas-fired RICE. The same build-out with combined-cycle gas comes to 145 to 253 premature deaths and $2.3bn to $3.8bn. RICE means reciprocating internal combustion engines: many small units running in parallel rather than a few large turbines.

The RICE scenario is not hypothetical. It is patterned on a methane gas-powered data center with 69 RICE generators that the Utah Division of Air Quality permitted in Millard County in early 2026.

Stratos cleared its first hurdle in May. The Box Elder County Commission approved the project under highly contentious circumstances, inside a project area created by Utah's Military Installation Development Authority.

The grid queue pushes operators on-site

The reason operators build their own generation is waiting. Hooking up 100MW to the grid in Northern Virginia takes about seven years, according to the International Energy Agency. Rystad Energy analyst Audun Martinsen told the New York Times that jet-powered units can have a data center running in 24 months.

xAI has already installed eight converted jet-engine turbines in Mississippi to help power its Colossus 2 data center in Memphis, according to a New York Times report cited by TechCrunch on 3 November.

Each unit can produce up to 50MW, normally enough to keep around 15,000 homes running.

ProEnergy, a Missouri company, rebuilds GE engines commonly found on Boeing jets for data-center duty.

The queue is already costing operators business. Microsoft pulled out as anchor customer for Nscale's data center in Loughton, England, after the local utility said it could not deliver enough power until the early to mid-2030s. As of April, half of data center buildouts had been canceled or delayed, with lack of power among the causes.

Efficiency, emissions and equipment limits

The shortcut has its own physics. Converted jet engines are less efficient and pollute more than turbines built for conventional gas plants, and it takes more of them to make the same power, according to the Times.

Permits reflect that. xAI's permits allow a 25% higher limit for volatile organic compounds, and environmentalists have warned about carbon monoxide.

The Southern Environmental Law Center has challenged Mississippi's decision, arguing xAI failed to guarantee the turbines meet standards for pollutants including formaldehyde and undercounted projected emissions.

Supply is the other constraint. Some turbine models are effectively sold out through 2031, according to Data Center Knowledge.

Patrick Hughes, senior vice president at NEMA, told Data Center Knowledge that a standalone AI data center can generate enough on-site power. But he said it is not feasible for a single facility, let alone the whole fleet, to supply 100% of its own power and run reliably around the clock. A hybrid of on-site generation and grid connection is the likely outcome for many sites, he said.

Developers are still lining up. TerraVolt acquired 1,077 acres in Cassia County, Idaho, for a behind-the-meter gas campus with an initial 240MW of on-site generation. It has an agreement for 55,000 MMBtu per day from the Williams Northwest pipeline.

What happens next

Drax signed an agreement with Brookfield and Radiant to develop an AI data center at Drax Power Station in North Yorkshire. Phase one targets up to 100MW of compute capacity operational from the first quarter of 2028, with a further 500MW between 2028 and 2031.

The partners are looking for more than 1GW at the site by an unspecified date. The first phase still needs planning, regulatory and network approvals and a tenant, and final investment decisions have not been made. Drax hopes to clear the approvals needed to supply the data center directly by the early 2030s.

xAI, meanwhile, plans to increase its data center capacity by 7x before the end of 2027, Elon Musk said in August. President Donald Trump said in an Oct. 21 Truth Social post that new, large-scale data centers should generate their own electricity and return excess power to the local community or grid. That post has not been translated into formal policy.

The numbers behind the pivot

• Stratos at 9GW: 5 to 45 additional premature deaths and $75m to $690m in health damages per year.
• 100MW grid connection in Northern Virginia: about seven years, against 24 months for a jet-powered data center.
• xAI's eight converted jet engines: up to 50MW each, enough for around 15,000 homes per unit.
• US data centers: 20% of all power by 2035, an 83% increase over the same forecast made seven months earlier.
• Drax phase one: up to 100MW of compute capacity from Q1 2028, then 500MW between 2028 and 2031, then more than 1GW.
• Turbine supply: some models sold out through 2031.
• xAI capacity: a 7x increase before the end of 2027.