Emissions Compliance for Emergency Power Supply Systems (EPSS)

Between 2022 and 2030, Goldman Sachs estimated that carbon dioxide emissions from data centers may more than double.

A study by the California Energy Commission estimates that data center power consumption by 2040 is expected to increase by 3-6 times more than 2021 levels, putting a strain on that State’s emissions goals.

Data Center Emissions Regulatory Frameworks

Governments and regulatory bodies worldwide are increasingly recognizing the need to regulate emissions from data centers. Various regulations and mandates have been introduced to ensure that data centers operate sustainably and minimize their impact on air quality and on the environment in general.

European Union (EU) Regulations

In the EU, the European Green Deal aims to make Europe the first climate-neutral continent by 2050. As part of this initiative, the EU has introduced several regulations that impact data centers:

• EU Emissions Trading System (ETS). Data centers that exceed a certain threshold of energy consumption are required to participate in the EU ETS, which mandates the monitoring, reporting, and verification of greenhouse gas (GHG) emissions. Operators must acquire allowances for their emissions, incentivizing reductions.
• Energy Efficiency Directive (EED). This directive sets binding measures to improve energy efficiency, including stringent requirements for energy audits and energy management systems for large data centers.
• Ecodesign for Sustainable Products Regulation (ESPR). This directive sets minimum energy performance standards for energy-related products, including servers and data storage, ensuring that only energy-efficient equipment is used.

United States Regulations

In the United States, several federal and state-level regulations govern emissions from data centers:

• Clean Air Act (CAA). The Environmental Protection Agency (EPA) oversees the implementation of the CAA, which includes regulations on emissions of hazardous air pollutants and greenhouse gases from industrial sources, including data centers. Data centers with on-site generators and other combustion sources must meet National Ambient Air Quality Standards (NAAQS) and obtain State and local air permits.
• Energy Star Program. Managed by the EPA and the Department of Energy (DOE), this voluntary program promotes energy efficiency in data centers through the certification of energy-efficient products and practices. However, recent reports suggest the EPA plans to terminate its Energy Star program as part of the administration’s government efficiency mandates.
• Energy Act of 2020. This law encoded in US Code Title 42, Section 17112 (Energy Efficiency for Data Center Buildings) requires federal agencies to evaluate their data centers for energy efficiency no less frequently than once every four years by a certified practitioner. We expect this law to be reviewed in 2025. Of particular interest is Section 1003 which covers efficiency requirements for data centers.
• State-Level Initiatives. States such as California have introduced their own regulations targeting data center emissions. The California Energy Commission (CEC) has set energy efficiency standards for data centers and other buildings to reduce energy consumption and emissions. Also, the State of Texas has proposed legislation aimed at addressing the strain data centers could place on the grid, establishing interconnection standards for facilities with high energy demands.

Data centers have the potential to impact the environment given the high energy consumption and potential strain on water resources utilized in the cooling systems.  Each jurisdiction’s mix of requirements means that a data center operator must consider the gamut of rules.

Global Initiatives

In addition to regional regulations, several global initiatives encourage data centers to monitor and reduce their emissions:

• Carbon Disclosure Project (CDP). This global disclosure system enables data centers to measure and manage their environmental impact, including greenhouse gas emissions, and report their progress transparently.
• Science-Based Targets Initiative (SBTi). SBTi provides a framework for data centers to set ambitious emissions reduction targets in line with the latest climate science, ensuring their efforts contribute to limiting global warming.
• Greenhouse Gas Protocol (GHGP). While not legally binding, this comprehensive global standard influences regulation and legislation. The GHGP-ICT (Information and Communication Technology) protocol outlines guidance for ICT products with an emphasis on ICT services, which includes data centers supporting efforts to achieves sustainability goals.
• International Standards Organization (ISO). ISO 14001 is the internationally recognized standard for environmental management systems (EMS) and sets reporting standards designed to improve energy efficiency, waste management, and resource management. In fact, Google Cloud implemented an ISO 14001-compliant EMS covering its Ireland and Netherlands data center.

Emission Classification of Data Centers under the GHGP

Data Center emissions can be classified into three areas:

Direct Emissions (Scope 1). These are direct emissions from sources owned or controlled by the data center, such as emissions from combustion of fuel for EPSS backup generators, microgrids, leakage from switchgear, or cooling system releases.

Indirect Emissions (Scope 2). These are indirect emissions from the generation of purchased electricity, steam, heat, and cooling used by the data center. The most common type of Scope 2 emissions from a data center would be associated with emissions from electricity purchased from a utility (i.e., the “grid”).

All Other Indirect Emissions (Scope 3). These include all other indirect emissions that are not included in Scope 1 or 2, encompassing the entire value chain, including emissions from suppliers (e.g., the emissions of vehicles delivering diesel fuel), transportation, and the end-of-life of certain equipment.

EPA Regulations Impacting Data Center EPSS and Microgrid Engines

Regulated Emissions Components Impacting Diesel Generator Backup Systems in Data Centers

Emissions Constituents Regulated for NAAQS. Reciprocating engines powered by diesel or natural gas emit four of the six regulated Criteria Air Pollutants. The EPA has implemented increasingly strict tier standards to reduce these emissions and meet NAAQS healthy air goals.

The regulated diesel exhaust components are:

• Nitrogen Dioxide (NO₂) and Nitric Oxide (NO), commonly referred as Oxides of Nitrogen (NOx). Applying for an air permit authorizing a new diesel Emergency Power Standby System (EPSS) often involves NO₂ and NO emissions (i.e., NOx), especially in high-background NO₂ areas, as they are precursors to ozone formation.
• Particulate Matter (PM) – These result from incomplete fuel combustion and appear as soot in the exhaust.
• Hydrocarbons (HC) or Volatile Organic Compounds (VOCs). These result from incomplete fuel combustion and are precursors for ozone formation.
• Carbon Monoxide (CO). Modern diesel engines emit less CO than older ones, and natural gas engines emit lower levels of CO compared to modern diesel engines.
• Carbon Dioxide (CO₂). Natural gas engines generally produce lower CO₂ emissions compared to diesel engines but still require testing.

EPA Regulations Impacting Diesel Powered EPSS In Data Centers

Diesel generator backup systems are commonly used to assure continuity of operations, especially at critical data centers responsible for emergency response and financial transaction processing. These systems can come under various EPA regulatory mandates, depending on their location and size.

For data centers with EPSS using Stationary Compression Ignition (CI) Reciprocating Internal Combustion Engines (RICE) (i.e., diesel engines), EPA regulations require EPSS over 500 horsepower (HP) to meet Tier 3 standards, and those over 752 HP to comply with Tier 2 standards under NSPS and NESHAP.

The EPA mandates exhaust emissions from non-road diesel engines to meet NAAQS through four tiers. Engine tier depends on the model year and horsepower rating. Tier 1 standards were implemented between 1996 and 2000. Tier 2 standards, which are more stringent, were in effect from 2001 to 2006. Tier 3 standards, even more stringent, were phased in from 2006 to 2008, applying only to engines with power ratings between 37-560 kW.

In 2004 the EPA approved a final rule introducing Tier 4 emission standards, which were phased-in over the period of 2008-2015. Today, Tier 4 standards are currently the most stringent and in effect for newly manufactured prime power and portable diesel generators. Importantly, if an engine is part of an EPSS for emergency standby use, then Tier 4 is not required.

Larger diesel engines must also follow additional regulations, especially in non-attainment areas.

• RICE (Reciprocating Internal Combustion Engine). Existing stationary generator systems could require exhaust after-treatment to ensure the total facility emissions comply with NESHAP (National Emissions Standards for Hazardous Air Pollutants).
• RICE NESHAP. Applies to existing and new large stationary diesel generator systems.
• NSPS (New Source Performance Standards). An EPSS with an engine greater than 500 HP must be Tier 3 and greater than 752 HP must be Tier 2 compliant. Tier 4 does not apply to generators used for emergency purposes.
• NFPA 110 (National Fire Protection Association). Systems such as data centers, that are classified as critical power systems, must be tested in compliance with NFPA 110 level 1. A level 1 EPSS must be tested for at least 4 hours at least once every 36 months. Generators with diesel engines at 500 HP and above can produce exhaust emissions that exceed background air quality limits when a permit is being sought in a non-attainment area.

READ MORE: EPA: Understanding the Stationary Engines Rules

EPA Regulations Impacting Natural Gas-Powered Engine and Turbine EPSS In Data Centers

Natural gas turbines are also used in EPSS applications, and their emissions are regulated under the New Source Performance Standards (NSPS) for stationary combustion turbines outlined in the Code of Federal Regulations under 40 CFR Part 60 Subparts GG and KKKK.  Also, spark ignition internal combustion engines (SI-ICE) can be used as backup and as the primary source of power. The NSPS for this type of equipment is under 40 CFR Part 66 Subpart JJJJ.

• 40 CFR Part 60 Subpart GG applies to stationary turbines that commenced construction, modification, or reconstruction after October 3, 1977.
• 40 CFR Part 60 Subpart KKKK applies to stationary turbines that that commenced construction, modification or reconstruction after February 18, 2005.
• 40 CFR Part 60 Subpart JJJJ applies to spark ignition internal combustion engines (SI-ICE) for various manufacturing years, including both prime and emergency engines meeting various classifications ranging from 19 kilowatts (25 horsepower) up to 1,349 horsepower.

For the most part, emergency natural gas turbines part of an EPSS are exempt from some emissions requirements (i.e., NOx), however, since the regulations are complex we encourage operators to seek qualified counsel for their specific operation(s).

READ MORE: Stationary Gas and Combustion Turbines: New Source Performance Standards (NSPS)

Note that NFPA 110 (National Fire Protection Association) standards apply to natural gas turbine generators used in data center EPSS’s and must be tested in compliance with NFPA 110 level 1.

Microgrids for Data Centers

In some regions, demand for power from data centers is growing faster than local utilities can add capacity and in remote areas no power infrastructure exists. In these cases, operators are turning to self-generation options, including microgrids.

A microgrid is a self-contained electricity generation and distribution network that is not connected to a regulated utility grid. Microgrids use different energy storage systems and power sources, including solar, wind, or gensets using natural gas turbines or reciprocating engines. If your data center uses a microgrid as a primary power source or EPSS, it may be subject to EPA emissions regulations and engine performance testing requirements.