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Emission Standards

EU: Nonroad Engines


European emission standards for engines used in new non-road mobile machinery (NRMM) have been structured as gradually more stringent tiers known as Stage I...V standards. Stage I...IV regulations for diesel engines were specified by Directive 97/68/EC and five amending Directives adopted from 2002 to 2012 [2909]. One of the amending Directives [2905] also introduced emission standards for small, spark-ignited nonroad engines. From Stage V, Regulation 2016/1628 [3478] specifies emission requirements for all categories of compression ignition (diesel) and positive ignition mobile nonroad engines, replacing Directive 97/68/EC and its amendments.

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The main regulatory steps in the development of EU nonroad emission standards include:

  • Stage I/II. The first European legislation to regulate emissions from nonroad (off-road) mobile equipment was promulgated on December 16, 1997 [2621]. The regulations for nonroad diesels were introduced in two stages: Stage I implemented in 1999 and Stage II implemented from 2001 to 2004, depending on the engine power output.

    The equipment covered by the standard included industrial drilling rigs, compressors, construction wheel loaders, bulldozers, nonroad trucks, highway excavators, forklift trucks, road maintenance equipment, snow plows, ground support equipment in airports, aerial lifts and mobile cranes. Agricultural and forestry tractors had the same emission standards but different implementation dates [2908]. Engines used in ships, railway locomotives, aircraft, and generating sets were not covered by the Stage I/II standards.

  • Small Utility Engines. On December 9, 2002, the European Parliament adopted Directive 2002/88/EC [2905], amending the nonroad Directive 97/68/EC by adding emission standards for small spark-ignited engines below 19 kW. The Directive also extended the applicability of Stage II standards on constant speed engines. The utility engine emission standards are to a large degree aligned with the US emission standards for small utility engines.
  • Stage III/IV. Stage III/IV emission standards for nonroad engines were adopted on April 21, 2004 [2906], and for agricultural and forestry tractors on February 21, 2005 [2907].

    Two additional Directives were adopted in 2010: Directive 2010/26/EU [2903] provides further technical details on the testing and approvals of Stage IIIB and Stage IV engines, and Directive 2010/22/EU [2904] amends the earlier legislation applicable to agricultural and forestry tractors.

    Stage III standards—which are further divided into Stages IIIA and IIIB—are phased-in from 2006 to 2013, Stage IV enter into force in 2014. The Stage III/IV standards, in addition to the engine categories regulated at Stage I/II, also cover railroad locomotive engines and marine engines used for inland waterway vessels. Stage III/IV legislation applies only to new vehicles and equipment; replacement engines to be used in machinery already in use (except for railcar, locomotive and inland waterway vessel propulsion engines) should comply with the limit values that the engine to be replaced had to meet when originally placed on the market.

  • Stage V. The regulation was proposed in 2014 [3125] and finalized on September 14, 2016 [3478]. Detailed technical requirements have been defined in a series of implementing regulations. The standards are effective from 2019 for engines below 56 kW and above 130 kW, and from 2020 for engines of 56-130 kW. The Stage V regulation introduced a number of important changes, including:
    • Widening of the scope of regulated engines including compression ignition (CI) engines below 19 kW and above 560 kW, spark ignited (SI) engines above 19 kW, and other previously unregulated engines. Under the Stage V regulation, emissions are regulated from the following engine categories:
      1. Category NRE—Engines for mobile nonroad machinery, suited to move or to be moved, that are not included in any of the points below;
      2. Category NRG—Engines above 560 kW used in generating sets;
      3. Category NRSh—SI engines below 19 kW exclusively for use in hand-held machinery;
      4. Category NRS—SI engines below 56 kW that are not included in category NRSh;
      5. Category IWP—Engines above 19 kW used for direct or indirect propulsion of inland waterway vessels;
      6. Category IWA—Auxiliary engines above 19 kW for use in inland waterway vessels;
      7. Category RLL—Engines for the propulsion of railway locomotives;
      8. Category RLR—Engines for the propulsion of railcars;
      9. Category SMB—SI engines used in snowmobiles;
      10. Category ATS—SI engines used in all terrain and side-by-side vehicles.
    • Strengthening emission limits for some engine categories, such as engines of 19-37 kW and engines for inland waterway vessels.
    • Adopting particle number (PN) emission limits for several categories of CI engines between 19 and 560 kW.
  • Future. Stage V legislation commits the European Commission to produce two reports on future emission regulations for nonroad engines:
    • By the end of 2018—An assessment of the possibility of adopting measures for the installation of retrofit emission control devices in existing, in-use nonroad engines.
    • By the end of 2020—An assessment of further pollutant emission reduction potential, and the identification of potentially relevant pollutant types that do not fall within the scope of the Stage V regulation.

Regulatory authorities in the EU, USA, and Japan have been under pressure from engine and equipment manufacturers to harmonize worldwide emission standards, in order to streamline engine development and emission type approval/certification for different markets. Stage I/II limits were in part harmonized with US regulations. Stage III/IV requirements were harmonized to a large degree with the US Tier 3/4 standards. However, at Stage V the harmonization has been largely lost—the Stage V PN limits require diesel particulate filters (DPF) on all affected engines, while the US Tier 4 standards can be met without filters.

EU nonroad emission standards usually specify two sets of implementation dates: (1) type approval dates, after which all newly type approved models must meet the standard, and (2) market placement (or first registration) dates, after which all new engines placed on the market must meet the standard. The dates listed in the following tables are the market placement dates. In most cases, new type approval dates are one year before the respective market placement dates.

Regulatory information on emission standards for nonroad engines can be found in the European Commission web site [2910].

Stage I/II Standards

Stage I and Stage II emission limits are shown in Table 1. The Stage I emissions are engine-out limits and shall be achieved before any exhaust aftertreatment device.

Table 1
EU Stage I/II emission standards for nonroad diesel engines
Cat.Net PowerDate*COHCNOxPM
Stage I
A130 ≤ P ≤ 5601999.
B75 ≤ P < 1301999.
C37 ≤ P < 751999.
Stage II
E130 ≤ P ≤ 5602002.
F75 ≤ P < 1302003.
G37 ≤ P < 752004.
D18 ≤ P < 372001.
* Stage II also applies to constant speed engines effective 2007.01

A sell-off period of up to two years was allowed for engines produced prior to the respective market placement date. Since the sell-off period—between zero and two years—was determined by each Member State, the exact timeframe of the regulations may have been different in different countries.

Emissions were measured on the ISO 8178 C1 8-mode cycle and expressed in g/kWh. Stage I/II engines were tested using fuel of 0.1-0.2% (wt.) sulfur content.

Stage III/IV Standards

Stage III standards—which are further divided into two sub-stages: Stage III A and Stage III B—and Stage IV standards for nonroad diesel engines are listed in Table 2 and Table 3. These limit values apply to all nonroad diesel engines of indicated power range for use in applications other than rail traction and inland waterway vessels.

Table 2
Stage III A/B emission standards for nonroad diesel engines
Cat.Net PowerDateCOHCHC+NOxNOxPM
Stage III A
H130 ≤ P ≤ 5602006.013.5-4.0-0.2
I75 ≤ P < 1302007.015.0-4.0-0.3
J37 ≤ P < 752008.015.0-4.7-0.4
K19 ≤ P < 372007.015.5-7.5-0.6
Stage III B
L130 ≤ P ≤ 5602011.013.50.19-2.00.025
M75 ≤ P < 1302012.015.00.19-3.30.025
N56 ≤ P < 752012.015.00.19-3.30.025
P37 ≤ P < 562013.015.0-4.7-0.025
† Dates for constant speed engines are: 2011.01 for categories H, I and K; 2012.01 for category J.
Table 3
Stage IV emission standards for nonroad diesel engines
Cat.Net PowerDateCOHCNOxPM
Q130 ≤ P ≤ 5602014.
R56 ≤ P < 1302014.

Stage III/IV standards also include a limit for ammonia emissions, which must not exceed a mean of 25 ppm over the test cycle.

Stage III B standards introduced a PM limit of 0.025 g/kWh, designed to force the use of diesel particulate filters. In reality, a significant proportion of engines were able to meet the PM limit through in-cylinder technologies, without filters. Stage IV standards introduced a very stringent NOx limit of 0.4 g/kWh, which has triggered a widespread use of NOx aftertreatment (typically urea-SCR) on affected categories of engines.

Testing. To represent emissions during real conditions, a new transient test procedure—the Non-Road Transient Cycle (NRTC)—was developed in cooperation with the US EPA. The NRTC is run twice—with a cold and a hot start. The final emission results are weighted averages of 10% for the cold start and 90% for the hot start run. The new test will be used in parallel with the prior steady-state schedule, ISO 8178 C1, referred to as the Non-Road Steady Cycle (NRSC).

  • The NRSC (steady-state) is used for Stage I, II and III A testing, as well as for constant speed engines at all stages. The NRTC (transient) can be used for Stage III A testing by the choice of the manufacturer.
  • Both NRSC and NRTC cycles must be used for Stage III B and IV testing, for both gaseous and particulate emissions.

Defeat Devices. For Stage III and IV engines, ‘defeat device’ is defined as:

a device which measures, senses or responds to operating variables for the purpose of activating, modulating, delaying or deactivating the operation of any component or function of the emission control system such that the effectiveness of the control system is reduced under conditions encountered during the normal non-road mobile machinery use unless the use of such a device is substantially included in the applied emission test certification procedure.

Also, ‘irrational control strategy’ is defined as:

any strategy or measure that, when the non-road mobile machinery is operated under normal conditions of use, reduces the effectiveness of the emission control system to a level below that expected in the applicable emission test procedures.

While defeat devices and irrational control strategies are prohibited, ‘emission control system’ is not clearly defined.

In 2010, with the introduction of Stage IV measures, Auxiliary Emission Control Strategy (AECS) and Base Emission Control Strategy (BECS) wre introduced similar to that in heavy-duty on road engines, as well as a requirement to fully disclosure details on their operation and justification for their use.

Stage V Standards

Stage V emission limits for engines in nonroad mobile machinery (category NRE) are shown in Table 4. These standards are applicable to diesel (CI) engines from 0 to 56 kW and to all types of engines above 56 kW. Engines above 560 kW used in generator sets (category NRG) must meet standards shown in Table 5 (NRSC and NRTC test cycles). A “v” in the category designation indicates a variable speed engine while a “c” indicates a constant speed engine.

Table 4
Stage V emission standards for nonroad engines (NRE)
CategoryIgn.Net PowerDateCOHCNOxPMPN
NRE-v/c-1CIP < 820198.007.50a,c0.40b-
NRE-v/c-2CI8 ≤ P < 1920196.607.50a,c0.40-
NRE-v/c-3CI19 ≤ P < 3720195.004.70a,c0.0151×1012
NRE-v/c-4CI37 ≤ P < 5620195.004.70a,c0.0151×1012
NRE-v/c-5All56 ≤ P < 13020205.000.19c0.400.0151×1012
NRE-v/c-6All130 ≤ P ≤ 56020193.500.19c0.400.0151×1012
NRE-v/c-7AllP > 56020193.500.19d3.500.045-
a HC+NOx
b 0.60 for hand-startable, air-cooled direct injection engines
c A = 1.10 for gas engines
d A = 6.00 for gas engines
Table 5
Stage V emission standards for generator set engines above 560 kW (NRG)
CategoryIgn.Net PowerDateCOHCNOxPMPN
NRG-v/c-1AllP > 56020193.500.19a0.670.035-
a A = 6.00 for gas engines

Stage V regulation introduced a new limit for particle number emissions. The PN limit is designed to ensure that a highly efficient particle control technology—such as wall-flow particulate filters—be used on all affected engine categories. The Stage V regulation also tightened the mass-based PM limit for several engine categories, from 0.025 g/kWh to 0.015 g/kWh.

HC Limits for Gas Engines. For engine categories where an A factor is defined, the HC limit for fully and partially gaseous fueled engines indicated in the table is replaced by the one calculated from the formula:

HC = 0.19 + (1.5 × A × GER)(1)

where GER is the average gas energy ratio over the appropriate cycle. Where both a steady-state and transient test cycle applies, the GER shall be determined from the hot-start transient test cycle. If the calculated limit for HC exceeds the value of 0.19 + A, the limit for HC should be set to 0.19 + A.

Defeat Strategy. The Stage V regulation adopts the following definitions:

‘defeat strategy’ means an emission control strategy that reduces the effectiveness of the emission control system under ambient or engine operating conditions encountered either during normal machine operation or outside the EU type-approval test procedures

‘emission control system’ means any device, system or element of design that controls or reduces emissions

Defeat strategies are prohibited.

Inland Waterway Vessels

Stage III A standards introduced emission limits for engines used in inland waterway vessels, Table 6. Engines are divided into categories based on the displacement (swept volume) per cylinder and net power output. The engine categories and the standards are harmonized with the US standards for marine engines. There are no Stage III B or Stage IV standards for waterway vessels.

Table 6
Stage III A emission standards for engines in inland waterway vessels
CategoryDisplacement (D)DateCOHC+NOxPM
dm3 per cylinderg/kWh
V1:1D ≤ 0.9, P > 37 kW20075.07.50.40
V1:20.9 < D ≤
V1:31.2 < D ≤
V1:42.5 < D ≤ 520095.07.20.20
V2:15 < D ≤
V2:215 < D ≤ 20, P ≤ 3300 kW5.08.70.50
V2:315 < D ≤ 20, P > 3300 kW5.09.80.50
V2:420 < D ≤
V2:525 < D ≤ 305.011.00.50

Emission limits for inland waterway vessels have been significantly tightened under the Stage V regulation. The Stage V limits, Table 7, are applicable to propulsion (IWP) and auxiliary (IWA) engines above 19 kW, including engines of all types of ignition.

Table 7
Stage V emission standards for engines in inland waterway vessels (IWP & IWA)
CategoryNet PowerDateCOHCaNOxPMPN
IWP/IWA-v/c-119 ≤ P < 75 20195.004.70b0.30-
IWP/IWA-v/c-275 ≤ P < 130 20195.005.40b0.14-
IWP/IWA-v/c-3130 ≤ P < 30020193.501.002.100.10-
IWP/IWA-v/c-4P ≥ 300 20203.500.191.800.0151×1012
a A = 6.00 for gas engines
b HC + NOx

Rail Traction Engines

Stage III A and III B standards have been adopted for engines above 130 kW used for the propulsion of railroad locomotives (categories R, RL, RH) and railcars (RC), Table 8. There are no Stage IV standards for rail traction engines.

Table 8
Stage III A/B emission standards for rail traction engines
CategoryNet PowerDateCOHCHC+NOxNOxPM
Stage III A
RC AP > 13020063.5-4.0-0.2
RL A130 ≤ P ≤ 56020073.5-4.0-0.2
RH AP > 56020093.50.5*-6.0*0.2
Stage III B
RC BP > 13020123.50.19-2.00.025
R BP > 13020123.5-4.0-0.025
* HC = 0.4 g/kWh and NOx = 7.4 g/kWh for engines of P > 2000 kW and D > 5 liters/cylinder

Stage V emission standards apply to engines used for the propulsion of rail locomotives (RLL) and railcars (RLR) of any power rating and any type of ignition. The limits are shown in Table 9. Auxiliary engines used in locomotives or railcars should meet emission standards for categories NRE or NRS.

Table 9
Stage V emission standards for rail traction engines
CategoryNet PowerDateCOHCaNOxPMPN
RLL-v/c-1 (Locomotives)P > 020213.504.00b0.025-
RLR-v/c-1 (Railcars)P > 020213.500.192.000.0151×1012
a A = 6.00 for gas engines
b HC + NOx