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Emission Standards

EU: Stationary Engines

Background

Two EU directives have been adopted to control emissions from combustion plants, including emissions from large stationary internal combustion engines:

  • Industrial Emissions Directive [3716], adopted in November 2010, applies to combustion plants with a rated thermal input of P ≥ 50 MWth.
  • Medium Combustion Plant Directive (MCP Directive) [3715], adopted in November 2015, introduces emission limits for plants in the power range 1 ≤ P < 50 MWth.

The MCP Directive also ensures implementation of the obligations arising from the Gothenburg Protocol under the UNECE Convention on Long-Range Transboundary Air Pollution.

Under both directives, it is the responsibility of the combustion plant (engine) operator to monitor and register the emissions of air pollutants and to take the necessary measures to ensure compliance with the directive emission limit values.

Stationary engines below 1 MW—such as generator set engines—may be covered by emission standards for non-road mobile machinery (NRMM).

Industrial Emissions Directive (P ≥ 50 MW)

Emission limits for gas engines ≥ 50 MWth are shown in Table 1 [3716]. No limits have been published for diesel engines. The emission values are defined at normalized conditions (273.15 K, 101.3 kPa) and corrected for water vapor content (dry gas) and oxygen concentration of 15%.

Table 1
Emission standards for gas engines ≥ 50 MWth
CategoryNOxCO
mg/Nm3
Permit or application before 7 January 2013100100
Permit or application after 7 January 201375100

Gas engines for emergency use (below 500 hours per year) and engines on offshore platforms are exempted.

From 1 January 2016, member states should establish an annual inventory of emissions for all combustion plants covered by the Directive. The emission limit values are to be periodically updated via the process for the determination of the best available techniques (BREF process).

Medium Combustion Plant Directive (1 ≤ P < 50 MW)

The MCP Directive is applicable to various types of combustion plants in the power range 1 ≤ P < 50 MWth, fueled by solid, liquid and gaseous fuels [3715]. The Directive sets limits for NOx, PM (dust) and SO2 emissions, and requires monitoring of CO emissions. New MCPs should comply with the emission limits from 20 December 2018. Existing plants with P > 5 MWth should comply from 1 January 2025 and plants with P ≤ 5 MWth from 1 January 2030.

The emission limits for engines fueled by gaseous and liquid fuels are summarized in the following tables. Emission values are defined at normalized conditions: temperature 273.15 K (0°C), pressure 101.3 kPa (1 atm), and corrected for water vapor content (dry gas) and oxygen concentration of 15%.

Table 2
MCP emission standards for gas fueled engines
Fuel TypeCategoryNOxPMSO2
mg/Nm3
Natural gasExisting engines190a--
New engines95b--
Other gaseous fuelsExisting engines190a-15c
New engines190-15d
a 380 mg/Nm3 for dual-fuel engines in gas mode
b 190 mg/Nm3 for dual-fuel engines in gas mode
c 60 mg/Nm3 for biogas engines
d 40 mg/Nm3 for biogas engines
Table 2
MCP emission standards for liquid fueled engines
Fuel TypeCategoryPowerNOxPMSO2
MWthmg/Nm3
Diesel (gas oil)Existing engines1 ≤ P ≤ 5250a--
5 < P < 50190a--
New engines1 ≤ P < 50190b--
Other liquid fuelsExisting engines1 ≤ P ≤ 5250a20120
5 < P ≤ 20225a20120
20 < P < 50190a10120
New engines1 ≤ P ≤ 5190b,c20d120e
5 < P < 50190b,c10d120e
a 1850 mg/Nm3 for (1) diesel engines the construction of which commenced before 18 May 2006 and (2) dual-fuel engines in liquid mode
b 225 mg/Nm3 for dual fuel engines in liquid mode.
c 225 mg/Nm3 for engines with a total rated thermal input ≤ 20 MW with ≤ 1200 rpm
d 75 mg/Nm3 until 1 January 2025 for engines which are part of small (SIS) or micro isolated (MIS) networks
e 590 mg/Nm3 until 1 January 2025 for engines which are part of small (SIS) or micro isolated (MIS) networks

Member states may define exemptions for plants operating less than 500 hours per year. The following types of equipment are exempted from the emission requirements:

  • Combustion plants covered by the Industrial Emissions Directive or by the Non-Road Mobile Machinery regulations;
  • Any technical apparatus used in the propulsion of a vehicle, ship or aircraft;
  • Gas turbines and gas and diesel engines used on offshore platforms;
  • Research, development or testing activities relating to medium combustion plants.

The strict NOx limits imposed by the MCP Directive will likely require the use of aftertreatment such as urea-SCR on many of the affected engines.