Stationary Reciprocating Internal Combustion Engines (RICE)

A stationary reciprocating internal combustion engine (RICE) is any internal combustion engine which uses reciprocating motion to convert heat energy into mechanical work and is not mobile. Stationary reciprocating engines differ from mobile reciprocating engines in that they are not used in road vehicles or nonroad mobile applications such as bulldozers, mowers, cranes, etc. Some engines are less easily categorized, for example, a generator mounted on a pallet or a trailer would not be considered stationary unless it will stay at a single site for at least a full year or full season, for a seasonal source (more information on stationary, nonroad, transportable, etc.).

There are two basic types of stationary reciprocating engines - spark ignition and compression ignition. Spark ignition engines use a spark (across a spark plug) to ignite a compressed fuel-air mixture. Typical fuels for such engines are gasoline and natural gas. Compression ignition engines compress air to a high pressure, heating the air to the ignition temperature of the fuel, which then is injected. The high compression ratio used for compression ignition engines results in a higher efficiency than is possible with spark ignition engines. Diesel fuel oil is normally used in compression ignition engines, although some are dual-fueled (natural gas is compressed with the combustion air and diesel oil is injected at the top of the compression stroke to initiate combustion).

Several million stationary reciprocating engines are in use throughout the U.S. In general, industry uses these engines to drive process equipment such as compressors, pumps, and other machinery and for standby generator sets.

Air Regulations

EPA air quality requirements for stationary engines differ according to:

• whether the engine is new or existing, and

• whether the engine is located at an area source or major source and whether the engine is a compression ignition or a spark ignition engine. "Spark ignition" engines are further subdivided by power cycle - i.e., two vs. four stroke, and whether the engine is "rich burn" (burning with a higher amount of fuel as compared to air) or "lean burn" (less fuel compared to air) engine.

Several regulations have expanded the number and type of stationary RICE that must comply with federal requirements. These include:

• National Emission Standard for Hazardous Air Pollutants (NESHAP) for Reciprocating Internal Combustion Engines (RICE), 40 CFR 63, Subpart ZZZZ ("the RICE rule").

• New Source Performance Standards (NSPS).- Standards of Performance for Stationary Spark Ignition Internal Combustion Engines, 40 CFR 60, Subpart JJJJ (Scroll to reach the Subpart – "the Spark Ignition NSPS rule").

• Standards of Performance for Stationary Compression Ignition Internal Combustion Engines, 40 CFR 60, Subpart IIII) (Scroll to reach the Subpart "the Compression Ignition NSPS rule").

Which types of engines are covered by the rules?

1. Engines >500 Horsepower (HP) at major source of HAP:
   • Existing engines if constructed before December 19, 2002
   • New engines if constructed on or after December 19, 2002
   • Reconstructed engines if reconstruction began on or after December 19, 2002

2. Engines ≤500 HP located at major source of HAP and engines of all horsepower located at an area source of HAP:
   • Existing engines if constructed before June 12, 2006
   • New engines if constructed on or after June 12, 2006
   • Reconstructed engines if reconstruction began on or after June 12, 2006

Which types of engines are NOT covered by the rules?

1. Motor vehicles, or to non-road engines, which are:
• self-propelled (tractors, bulldozers)
• propelled while performing their function (lawnmowers)
• portable or transportable (has wheels, skids, carrying handles, dolly, trailer or platform). Note: a portable non-road engine becomes stationary if it stays in one location for more than 12 months (or full annual operating period of a seasonal source)
2. Existing emergency engines located at residential, institutional, or commercial area sources and not used for local reliability. Engine must meet Subpart ZZZZ emergency engine operational requirements:
• Unlimited use for emergencies (e.g., power outage, fire, flood)
• Emergency engines may operate for 100 hr/yr for maintenance/testing
• 50 hr/yr of the 100 hr/yr allocation can be used for:
1. non-emergency situations if no financial arrangement
2. local reliability as part of a financial arrangement with another entity if specific criteria met (existing RICE at area sources of HAP only).

For more information, see Controlling Air Pollution from Stationary Engines, Compliance Requirements for Stationary Engines and this EPA RICE Fact Sheet.

More Resources

US EPA: Controlling Air Pollution from Stationary Engines.

Understanding the Stationary Engines Rules. An explanation of EPA air quality requirements for stationary engines.

NESHAP for Reciprocating Internal Combustion Engines. Tools and guidance documents for implementing the NESHAP for Reciprocating Internal Combustion Engines.