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Emission Standards » United States » Stationary Engines

Stationary 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. In several cases, engine operators are allowed two alternative compliance methods—by either purchasing an emission-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:

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.

Emission Standards

Stationary SI Engines ≤ 19 kW

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

Table 1
NSPS emission standards for SI stationary engines ≤ 19 kW (25 hp)
Engine ClassDisplacement (D)Date†Emission Standards
HC+NOxNMHC+NOx*CO
-cm3-g/kWh (g/hp-hr)
Class I-AD < 662008.0750 (37)-610 (455)
Class I-B66 ≤ D < 1002008.0740 (30)37 (27.6)610 (455)
Class I100 ≤ D < 2252008.0716.1 (12.0)14.8 (11.0)610 (455)
Class IID ≥ 2252008.0712.1 (9.0)11.3 (8.4)610 (455)
† Date of engine manufacture, modification or reconstruction
* NMHC+NOx standards are applicable only to natural gas engines at the option of the manufacturer, in lieu of HC+NOx standards

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].

Table 2
NSPS emission standards for SI stationary gasoline and rich burn LPG engines > 19 kW (25 hp)
Maximum Power (P)Duty CycleDate†Emission Standards
HC+NOxCO
hp--g/kWh (g/hp-hr)
25 < P < 500General2008.072.7 (2.0)4.4 (3.3)
Severe duty*2008.072.7 (2.0)130 (97)
P ≥ 500 General2007.072.7 (2.0)4.4 (3.3)
Severe duty*2007.072.7 (2.0)130 (97)
† Date of engine manufacture
* Severe-duty engines are engines used in, for example, concrete saws, concrete pumps, and similar severe applications where air-cooled engines must be used. There are expected to be very few, if any, severe-duty stationary engines.

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.

Table 3
NSPS emission standards for owners of SI stationary NG and lean burn LPG engines 19-75 kW (25-100 hp)
Maximum Power (P)Duty CycleDate†Emission Standardsa
HC+NOxbCO
hp--g/kWh (g/hp-hr)
25 < P < 100General2008.073.8 (2.8)6.5 (4.8)
Severe duty*2008.073.8 (2.8)200.0 (149.2)
† Date of engine manufacture, modification or reconstruction
* Severe-duty engines are engines used in, for example, concrete saws, concrete pumps, and similar severe applications where air-cooled engines must be used. There are expected to be very few, if any, severe-duty stationary engines.
a If (HC+NOx) × CO0.791 ≤ 16.78, alternative standards of HC+NOx = 3.8 g/kWh and CO = 31.0 g/kWh may be used.
b For natural gas engines, owners/operators can assume HC=0 during compliance testing

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.

Table 4
NSPS emission standards for NG and lean burn LPG engines ≥ 75 kW (100 hp)
Engine TypeMaximum Power (P)Date†Emission Standards
NOxCOa VOC*NOxCOa VOC*
-hp-g/hp-hrppmvd @ 15% O2
SI natural gas and SI lean burn LPG100 ≤ P < 500 2008.072.04.01.016054086
2011.011.02.00.78227060
SI lean burn natural gas and LPG500 ≤ P < 1350 2008.012.04.01.016054086
2010.071.02.00.78227060
SI natural gas and SI lean burn LPG (except lean burn 500 ≤ P < 1350)P ≥ 500 2007.072.04.01.016054086
2010.071.02.00.78227060
† Date of engine manufacture
* VOC emissions do not include formaldehyde
a Owners and operators of engines with a site rating ≥ 250 bhp located at a major source that are meeting the NIESHAP requirements (40 CFR part 63, subpart ZZZZ, Table 2a) do not have to comply with the CO standards

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.

Table 5
NSPS emission standards for new larger SI stationary engines
Engine TypeMaximum Power (P)Date†Emission Standards
NOxCOVOC*NOxCOVOC*
-hp-g/hp-hrppmvd @ 15% O2
Landfill/digester gas (except lean burn 500 ≤ P < 1,350)P < 500 2008.073.05.01.022061080
2010.012.05.01.015061080
P ≥ 500 2007.073.05.01.022061080
2010.072.05.01.015061080
Landfill/digester gas lean burn500 ≤ P < 1350 2008.013.05.01.022061080
2010.072.05.01.015061080
† Date of engine manufacture
* VOC emissions do not include formaldehyde

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).

Table 6
NSPS emission standards for SI stationary emergency engines > 19 kW
Maximum Power (P)Date†Emission Standards
NOxCOVOC*NOxCOVOC*
hp-g/hp-hrppmvd @ 15% O2
25 ≤ P < 1302009.011.0a387----
P ≥ 130 2009.012.04.01.016054086
† Date of engine manufacture
* VOC emissions do not include formaldehyde
a NOx + HC