Data centers play a vital role in everyday life by ensuring we have uninterrupted access to information. They are on the rise globally, and with that comes increased focus on the environment and air quality.
As the industry strives for sustainable operations and cleaner air, both carbon and nitrogen oxide (NOx) emissions are being reduced. Regulations are playing a major role in this shift, especially when it comes to NOx emissions.
NOx emissions from data centers primarily come from the combustion processes of their boilers and backup generators (gensets). As the heart of a data center's power backup system, gensets play a critical role in maintaining a data center’s smooth operation. However, when they burn fuel – whether it's diesel, hydrotreated vegetable oil (HVO) or another fuel – NOx emissions are released.
The combustion process in boilers used for climate control in data centers also produces NOx emissions. These systems provide necessary cooling to prevent overheating of equipment, and heating during colder months. While these sources of NOx are part of key in data center operations, the industry is implementing strategies to manage and reduce these emissions.
Data centers are becoming more sustainable by proactively reducing their carbon and NOx emissions from gensets use. Data centers are getting ahead of some of the most stringent air permitting regulations, which may vary depending on their location. For instance, local authorities may impose stricter regulations for standby gensets than the Environmental Protection Agency (EPA) and the European Union.
In North America, the EPA has specific stationary engine designations which determine the NOx emissions regulations a genset must comply with. For instance, standby or “emergency” gensets are subject to Tier 2 emission requirements. Standby gensets only run during power failures and regular site maintenance testing. For large data centers classified as major sources of NOx emissions, regulators can impose expensive monitoring requirements, with the ceiling for NOx emissions commonly set at 100 tons per year. There is also a growing number of air quality districts imposing lower limits on data centers.
On the other hand, “non-emergency” gensets must meet stricter Tier 4 emissions requirements. These gensets run in place of or in addition to power from an electricity provider. A Tier 4 certified product also requires gensets to shut down if aftertreatment system issues are sensed.
Beyond North America, requirements may vary globally. Although most regions have similar requirements to Tier 2 and Tier 4, the NOx calculation methodologies may differ. This makes it difficult to directly translate emissions performance between the different standards.
When navigating NOx emissions compliance, data center operators need to be mindful of a few values.
While genset manufacturers provide a nominal value of NOx emissions based on lab testing, some regulations require specific NOx values derived from actual site conditions. To guarantee compliance, it’s important to consider data center’s unique operating environment and choose a genset that meets their requirements.
What options do data centers have to significantly decrease their NOx emissions?
By adopting low NOx engine technology: Engine designs have come a long way in terms of power density and fuel consumption. They now meet the stringent EPA Tier 2 requirements. However, as NOx emissions regulations have become stricter, manufacturers are developing low NOx emissions solutions. It is important to always consult the genset manufacturer to best understand these options.
By installing further exhaust aftertreatment systems: Selective Catalytic Reduction (SCR) systems can reduce NOx emissions by 90 percent or more. This results in a Tier 4 compliant system that is integrated into the packaged generator set system. The process involves adding a reducing agent, typically ammonia-based, to the exhaust stream. This reacts with the catalyst, converting the NOx into nitrogen and water. There are two harmless substances, which are then released into the atmosphere.
By transitioning to cleaner technologies and fuels: Data Centers haven’t adopted natural gas widely due to fuel infrastructure challenges, but there is a growing interest in it due to grid constraints and its ability to reduce NOx. HVO is a promising carbon-reducing diesel alternative, yet it still produces NOx when burned. Increasingly more data centers are exploring new technologies like batteries, fuel cells, and hydrogen combustion engines. These technologies aim to reduce overall emissions of data centers while providing the same level of reliability that diesel generator sets have provided for decades.
Reducing NOx emissions is essential in the journey toward sustainable data center operations. Low NOx emissions engine technology, exhaust aftertreatment options, and cleaner fuels can help data centers to continue reducing NOx emissions and helping the environment.