Environmental and Regulatory Advantages of Natural Gas Generators

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Introduction

In an era of increasing environmental consciousness and tightening regulatory frameworks, the choice of power generation technology carries significant implications. This white paper explores the distinct environmental and regulatory advantages offered by natural gas generators, positioning them as a superior solution for both emergency standby and non-emergency power needs. By examining their cleaner-burning properties, lower emissions profile (compared to diesel generators), and streamlined compliance process, we demonstrate why natural gas generators are often a preferred choice to help businesses maintain sustainable and compliant operations.

Cleaner-Burning Properties and Reduced Emissions

Natural gas stands apart from traditional fossil fuels, particularly diesel, due to its inherently cleaner combustion characteristics. Composed primarily of methane, natural gas burns more completely and efficiently, resulting in a significantly reduced output of harmful pollutants.

Key emission advantages of natural gas generators as compared to diesel include:

• Reduced Nitrogen Oxides (NOx): Natural gas combustion produces substantially lower levels of NOx, a major contributor to smog and acid rain, compared to diesel. This reduction is critical for air quality improvement, especially in 
  urban areas where Hazardous Air Pollutant levels are already high.
• Reduced Carbon Monoxide (CO): While CO is a product of incomplete combustion, natural gas generators typically emit less CO than their diesel counterparts due to more efficient burning.
• Almost Zero Particulate Matter (PM): Perhaps the most significant advantage is the near-elimination of particulate matter emissions. Unlike diesel engines, which produce visible soot and fine particulate matter known for their adverse health impacts and contribution to haze, natural gas combustion is virtually free of PM, leading to cleaner air and reduced health risks.
• No Sulfur Dioxide (SO2): Natural gas is virtually sulfur-free, meaning its combustion does not produce sulfur dioxide, a primary cause of acid rain and respiratory issues. This contrasts sharply with diesel fuel, which, despite 
  advancements in ultra-low sulfur diesel (ULSD), still contains some level of sulfur.
• Non-Methane Hydrocarbons (NMHCs): Natural gas generators typically utilize a three-way catalyst (TWC), which are highly effective in combusting NMHCs, in addition to CO and NOx. Tier 2 and Tier 3 diesel engines require an add-on catalyst to achieve similar emissions reductions.
• Greenhouse Gases (GHGs): Natural gas has lower GHG and carbon dioxide (CO2) emissions compared to diesel fuel, resulting in a lower carbon footprint.

These inherent properties make natural gas a fundamentally cleaner fuel source, providing a clear environmental benefit over other common generator fuels. On average, Generac’s natural gas generators emit 95% less NOx emissions, 98% less NMHC emissions, and 59% less CO emissions as compared to equivalent diesel generators. Over the lifetime of the equipment, this results in significantly less emissions. See graph below:

See Appendix for calculation logic and assumptions

Alignment with Increasingly Stringent Environmental Regulations

The global trend towards stricter environmental regulations, driven by concerns over climate change and public health, places a premium on low-emission technologies. Natural gas generators are uniquely positioned to meet and exceed these evolving standards.

• Air Quality Standards: Agencies like the U.S. Environmental Protection Agency (EPA) and various state and local air quality management districts continuously update National Ambient Air Quality Standards (NAAQS) and implement stricter emission limits for stationary engines. Natural gas generators, with their lower NOx, CO, and PM emissions, are often able to comply with these limits more readily, reducing the need for exhaust after-treatment systems that are frequently required for diesel units.
• Greenhouse Gas Emissions: While natural gas is a fossil fuel and its combustion produces carbon dioxide (CO2), its carbon intensity per unit of energy is lower than that of diesel. Furthermore, the absence of black carbon (a potent short-lived climate pollutant) from PM emissions further improves its environmental profile.

The inherent cleanliness of natural gas as compared to diesel helps ease the path to regulatory compliance, future-proofing investments in power generation infrastructure against tightening environmental mandates.

Navigating Fuel Source Requirements: NFPA 70 and NFPA 110

The National Fire Protection Association (NFPA) codes, specifically NFPA 70 (National Electric Code) and NFPA 110 (Standard for Emergency and Standby Power Systems), provide guidance for emergency power systems. However, guidance 
regarding fuel sources requirements can sometimes appear ambiguous or even contradictory, leading to confusion among specifiers and Authorities Having Jurisdiction (AHJs).

• NFPA 70 (2023 Edition) Article 700.12(C) - Fuel Supply Duration: This article addresses the fuel supply duration for emergency systems and historically emphasized the need for an on-site fuel supply. While it might suggest a preference for on-site stored fuels like diesel, it also provides allowance for natural gas. Specifically, it permits the use of natural gas for emergency power systems where the AHJ determines there is a low probability of simultaneous failure of the normal power source and the natural gas supply. 
• NFPA 110 (2022 Edition) Section 5.1 - Energy Sources: Similar to NFPA 70, NFPA 110 outlines requirements for emergency and standby power systems, including energy sources. While it details requirements for on-site fuel storage for liquid fuels, its guidance on the acceptability of utility-supplied natural gas for emergency power systems has also been subject to interpretation. The standard aims to ensure system reliability, and the continuous availability of natural gas through a robust pipeline network is a key consideration.

Despite the perceived ambiguities in these standards, many AHJs across the United States have accepted and approved natural gas-fueled engines for emergency power systems. Historically, only on-site diesel storage would have been allowed. This increase in AHJ acceptance is driven by a practical understanding of natural gas infrastructure reliability, coupled with the environmental benefits. The aftermath of natural disasters like Irene and Sandby helped prove the resilience and improved the acceptance of NG as an acceptable source for emergency and life-safety systems. NFPA NEC 70 Chapter 7 Section 700.12(C)(3) allows natural gas as an acceptable fuel “where there is a low probability of simultaneous failure of both the off-site fuel delivery system and power from the outside electrical utility company.”

Examples of AHJ Acceptance

• New York City: While the NYC Building Code has historically favored on-site fuel for most emergency applications, it explicitly accepts utility gas supply as the primary fuel source for generators in certain scenarios, such as supplying emergency power in Group R-2 occupancies (e.g. multifamily buildings) and for standby power systems, provided the natural gas generator is isolated from other gas-fired appliances.
• Salt Lake City, Utah: Data centers and other critical facilities in areas like Salt Lake City have increasingly gained approval from local AHJs to utilize natural gas generators for emergency backup, leveraging the reliability of the natural gas grid as a viable alternative to large, on-site diesel fuel storage.

This growing trend reflects a pragmatic approach by AHJs, recognizing that the reliability and environmental advantages of natural gas can meet the intent of emergency power requirements, even when the prescriptive language might seem 
to lean towards on-site fuel storage.

Regulatory Landscape, Permitting Considerations, and Ease of Compliance

Navigating the regulatory landscape for power generation equipment can be complex and time-consuming. Natural gas generators offer a comparatively smoother path to permitting and compliance for both emergency standby and non-emergency applications.

• Permitting Ease: Due to their lower emission profiles, natural gas generators often fall into less stringent permitting categories or may even be exempt from certain complex air permits that are typically required for higher-emitting diesel 
  units. This can significantly reduce the time and cost associated with the permitting process. With reduced emissions, natural gas generators can sometimes be permitted with higher operational limits, allowing for increased operational flexibility, and in certain jurisdictions have lower annual permit renewal fees.
• Standby Applications: For standby generators, which operate infrequently during power outages, the regulatory burden is generally lower than for prime power units. However, even within this context, natural gas units often face fewer restrictions on run-time hours and testing schedules compared to diesel, particularly in Hazardous Air Pollutant non-attainment areas where air quality is a concern.
• Non-Emergency Applications: For non-emergency or prime power applications, where generators operate for extended periods, the environmental advantages of natural gas become even more critical. The ability to meet continuous emission monitoring requirements and comply with stricter operational limits without extensive and costly after-treatment systems provides a clear operational and financial benefit.
• Fuel Storage and Handling: Natural gas eliminates the need for on-site fuel storage tanks, which are subject to their own set of stringent environmental regulations (e.g., SPCC plans, storage tank regulations). This not only reduces regulatory compliance burdens but also mitigates risks associated with fuel spills and leaks.

The established infrastructure for natural gas delivery also simplifies fuel supply logistics, further contributing to operational ease and compliance.

Conclusion

Natural gas generators present compelling environmental and regulatory advantages that make them an increasingly attractive choice for modern power generation. Their cleaner-burning properties lead to significantly lower emissions of NOx, CO, and virtually no particulate matter, aligning seamlessly with the growing demand for cleaner air and sustainable practices. This superior environmental performance (as compared to diesel) translates directly into a more favorable regulatory landscape, simplifying permitting processes, helping reduce compliance burdens, and offering greater operational flexibility for both emergency standby and non-emergency applications. By choosing natural gas, organizations can achieve reliable power while demonstrating a commitment to environmental stewardship and helping ensure long-term regulatory compliance.

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