USA: Stationary Engines: SI Engines (NSPS)

Introduction

The new source performance standards (NSPS) for reciprocating internal combustion engines (RICE) establish US federal emission requirements for a number of categories of spark ignition (SI) engines. The Spark Ignition NSPS rule was adopted in 2008 [3350] and amended in 2011 [3113]. NSPS emission regulations for stationary SI engines are published in the Code of Federal Regulations (CFR), Title 40, Part 60, Subpart JJJJ.

The NSPS regulations for SI engines define a number of emission standards, depending on the engine maximum power, fuel, application, and other factors. Depending on the engine category, the onus for compliance is either on the engine manufacturer or the engine owners/operators. Engines rated at 19 kW or less and non-emergency gasoline and rich burn LPG engines rated above 19 kW require the engine manufacturer to certify the engine. For non-emergency natural gas and lean burn LPG engines as well as all emergency engines rated above 19 kW, engine operators are allowed two alternative compliance methods—by either purchasing a manufacturer certified engine or else by demonstrating compliance through emission testing in the field.

Many of the SI NSPS standards are based on nonroad emission standards for the corresponding non-stationary (i.e., mobile or portable) SI engine categories. These standards are expressed in g/kWh or g/bhp-hr. Some of the in-use standards are also expressed in terms of volumetric concentrations (such as volume ppm, dry, corrected to 15% O₂).

The SI NSPS standards for stationary engines are structured as follows:

• Engines ≤ 19 kW (25 hp)
• Engines > 19 kW (25 hp)
  • Non-emergency engines
    • Gasoline and rich burn liquefied petroleum gas (LPG) engines
    • Natural gas (NG) and lean burn LPG engines
    • Landfill/digester gas engines
  • Emergency engines

Fuel Requirements. In addition to emission standards, the 2008 rule introduced a requirement that owners and operators who use gasoline in their stationary SI engine must use gasoline that meets the requirements of 40 CFR 80.195, which include a gasoline sulfur per gallon cap of 80 ppm.

Test Cycles. For engines that must be certified by the manufacturer or which are voluntarily certified by the manufacturer, discreet or ramped mode cycles with 2-6 modes are used. Engines certified by the engine operator are certified within 10% of 100% peak load or the highest achievable load.

Volatile Organic Compounds (VOC). NSPS standards for some engine types limit VOC emissions. A number of different test procedures are allowed to determine VOCs. Formaldehyde should not be included when determining VOC emissions. Engine manufacturers are allowed to exclude methane and ethane from the determinations of VOCs. Some of the methods allowed for field testing for certification by operators can be operated to exclude methane and ethane.

Emission Standards

Stationary SI Engines ≤ 19 kW

Engine manufacturers must certify their stationary SI engines with a maximum power ≤ 19 kW to the certification emission standards for new nonroad SI engines in 40 CFR part 90, Table 1 [3350].

Gasoline and Rich Burn LPG Engines > 19 kW (Non-Emergency)

Engine manufacturers must certify their stationary non-emergency SI gasoline and rich burn LPG engines > 19 kW to the certification emission standards for new nonroad SI engines in 40 CFR part 1048, Table 2 [3350].

Natural Gas and Lean Burn LPG Engines > 19 kW (Non-Emergency)

Engines < 75 kW (100 hp)

Emission certification of stationary non-emergency SI natural gas engines and lean burn LPG engines between 25 hp and 100 hp is optional [3350]. Engine manufacturers may choose to certify their engines to the certification emission standards for rich burn engines, 40 CFR part 1048, shown in Table 2. Manufacturers may also certify engines between 19 and 30 kW (25-40 hp) with a displacement ≤ 1,000 cc to the nonroad engine standards of 40 CFR part 90, shown in Table 1. In addition, for engines manufactured before 2011, manufacturers could certify to the standards summarized in Table 4, applicable to engines of 100-500 hp.

Owners and operators who purchase stationary SI engines in this category must meet the emission standards in 40 CFR 1048.101(c), Table 3.

Engines ≥ 75 kW (100 hp)

Engine manufacturers may voluntarily certify their stationary non-emergency SI natural gas and lean burn LPG engines ≥ 100 hp to the standards shown in Table 4 [3113], but the certification is not required by the rule. Additionally, for natural gas engines below 500 hp manufactured before 2011, and natural gas engines ≥ 500 hp manufactured prior to 2010.07, manufacturers could certify to the standards for non-severe duty engines in 40 CFR part 1048, Table 2.

Owners and operators of stationary non-certified engines in this category must comply with the standards shown in Table 4. Engine owners/operators may choose to comply with the emission standards in units of either g/hp-hr or ppmvd at 15% O₂.

Landfill/Digester Gas Engines > 19 kW (Non-Emergency)

Emission standards for landfill/digester gas engines are summarized in Table 5 [3113]. The standards are voluntary for engine manufacturers (i.e., the rule does not require engine certification) and mandatory for owners and operators.

Emergency Engines > 19 kW

Owners and operators who purchase stationary emergency engines above 19 kW must comply with the standards shown in Table 6 [3113].

Engine manufacturers may voluntarily certify their stationary emergency SI engines, but the certification is not required by the rule, except for gasoline or rich burn LPG emergency engines that must be certified to the standards in 40 CFR part 90 (for engines < 130 hp) or 40 CFR part 1048 (for engines ≥ 130 hp, Table 2).