MARYLAND – This series explores the impacts of data centers on water supply, energy use and air quality in the Chesapeake Bay watershed. Data centers house the computer systems that enable internet activity and, increasingly, artificial intelligence. Northern Virginia, in the middle of the Bay watershed, is the global epicenter of these warehouse-like facilities. Their footprint is now spreading into Maryland and Pennsylvania too.
The data centers that increasingly fuel our AI-enabled interactions need to run 24 hours a day to keep the internet going. So, like grocery stores or hospitals, these facilities include backup power generators, often fueled by diesel or natural gas, and intended to run only during emergencies.
But in the Chesapeake Bay region, where exponential data center growth has put unprecedented strain on the power grid, such emergencies are no longer unthinkable.
This past summer, a fire knocked out an electrical substation in the midst of Data Center Alley in Loudoun County, VA. The outage caused data centers served by that station to use backup power for “several days” in late June and early July, according to the Virginia Department of Environmental Quality.
Each data center is equipped with sometimes dozens, sometimes hundreds of tractor trailer-sized generators largely running on diesel or natural gas. Burning these fossil fuels for power emits pollutants such as particulate matter, nitrogen oxides, sulfur dioxides and carbon dioxide. Some of these pose risks to human health while others degrade air quality in general, affecting the environment and the water where pollutants eventually flow.
The global race to build the infrastructure enabling AI is fueling a rash of new data centers that use exponentially more power than their predecessors. And, the more power they use, the more backup power they need.
Virginia’s DEQ requires air permits for each of these generators. These allow them to kick on periodically for 15- or 30-minute increments to ensure they will work in an emergency. The permits restrict when those tests can occur, avoiding hours when heavy commuter traffic is also contributing to air pollution, for example.
DEQ officials wrote in an email to the Chesapeake Bay Journal in September that it has issued permits for 5,447 data center generators in Loudoun County alone. Together, they have the capacity to provide more than 13.6 gigawatts of power. (For comparison, the North Anna Nuclear Generating Station in Louisa County, VA, has the capacity to produce 1.8 gigawatts of power.)
DEQ officials said their database does not break down the generators by the types of fuel they use or by the amount of pollutants each emits. There is some variation among units.
A DEQ guidance document states that “while the vast majority of the existing Virginia gen-set fleet is currently diesel-fired, there are cleaner and more efficient technologies available.”
The U.S. Environmental Protection Agency uses a tiered system for regulating non-road diesel engines that rates the machines for compliance. Tier I means the machine has the least permissible pollution reductions, and Tier IV means it meets the highest pollution reduction standards.
State or local governments can choose to require higher tiers of pollution removal from a project or industry, especially when the technology has been proven available. But such requirements can be costly to an industry that still has a choice when it comes to locations for new projects.
Christie Sayes, a professor of environmental science at Baylor University, said the resistance to costlier, cleaner technologies is not limited to data centers.
“In airplanes and cars, catalytic converters exist that are really efficient,” Sayes said. “But in a race to the bottom to make the most inexpensive vehicle, we don’t use that technology to limit pollution.”
Even so, Loudoun County Supervisor Michael Turner says he’s ready to require more of data centers wanting to locate in Loudoun, which is already home to the highest concentration of them in the world. The county’s board earlier this year ended by-right development of land for data centers so that every data center project must be approved by its members. And Turner would like to see more requirements made of the generators that accompany each project.
“Within the data industry, I’m sure I’m known as the Tier IV-generator guy,” Turner said of his desire for data center generators to use the best pollution reduction measures available.
Doing so could have other advantages in an uncertain energy future where onsite power generation could be the next frontier.
One data center company is now using Tier IV natural gas-fired combustion turbines as a main power source, in addition to diesel backup generators. Vantage began building the onsite power generation after being told by Dominion Energy in 2022 that its $1 billion project would not be able to get power from the constrained grid for up to three years.
The summer of 2022 was a tipping point for the data center power crunch in Virginia. State regulators proposed allowing Northern Virginia data centers to use backup generators in a more continuous manner for a five-month period during which energy “transmission problems” were anticipated. Homeowners’ associations that were already opposing data center projects in their backyards quickly coalesced to contest the proposal. The data center industry ended up asking regulators to rescind it.
But the outsized power demands have only grown since then, especially as more hyperscale data centers enabling AI come online. This past summer, the region faced another test of its grid when power demand for cooling reached record highs during heat waves in June and July.
PJM Interconnection, which manages the grid for the northeastern U.S., issued permission in late June for places with high power consumption to use backup systems instead of the grid to prevent blackouts.
A report commissioned by Virginia’s General Assembly late last year found that backup generators do emit harmful pollutants but that “existing regulations largely curb adverse impacts.” It acknowledges, though, that a “worst-case” scenario involving a widespread power outage could cause hundreds of backup generators to start up in a concentrated area, fouling regional air quality.
“I think the thing that will get everybody’s attention is when Northern Virginia blacks out or the grid fails,” Turner said. “I think we’ve come closer to that this summer than we have before.”