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While stationary engines may be one of the smaller, less significant pieces of equipment at an industrial facility, they are regulated by federal regulations that are complex and difficult to navigate.  EPA's National Emission Standards for Hazardous Air Pollutants (NESHAP) rule for Stationary Reciprocating Internal Combustion Engines (commonly referred to as RICE MACT) has undergone numerous changes since its initial promulgation in 2004, including the most recent amendments finalized on January 13, 2013. The table below provides a high level overview of how the applicability of this rule has been broadened over the course of several years to include almost all stationary RICE.


Rule DateApplicability (Affected Units)Federal Register Notice
2004Stationary RICE > 500 HP located at major sources of HAPs169 FR 33473
2008New Stationary RICE ≤ 500 HP located at major sources of HAPs
New stationary RICE (all sizes) located at area sources of HAPs2
73 FR 3568
2010Existing stationary RICE3 ≤ 500 HP located at major sources of HAPs
Existing stationary RICE (all sizes) located at area sources of HAPs
75 FR 9648 and 75 FR 51570

1A major source of HAPs is defined as a site that has the potential to emit ≥ 10 tpy single HAP or ≥ 25 tpy any combination of HAPs.
2 An area source of HAPs is defined as a site that is not a major source of HAPs.
3 Existing sources covered by 2010 amendments are stationary RICE constructed or reconstructed on or after June 12, 2006.


It is important to note that for certain new or reconstructed RICE, compliance with RICE MACT is achieved by compliance with New Source Performance Standards (NSPS) for stationary internal combustion engines codified in subparts IIII (NSPS for compression ignition [CI] internal combustion engines) and JJJJ (NSPS for spark ignition [SI] internal combustion engines).

The latest round of amendments to the rule address issues raised by various stakeholders and include the following key changes:

  • The addition of an alternative compliance demonstration method for existing and new stationary 4-stroke rich burn non-emergency engines > 500 HP located at major sources of HAPs and for existing 4SRB non-emergency engines > 500 HP located at area sources of HAPs.  While these engines are still subject to formaldehyde emissions limitations, the latest amendments allow owner/operators of such engines to demonstrate compliance with the formaldehyde standards by showing that the engine achieves at least a 30% reduction of THC emissions.  This alternate method reduces the cost of compliance significantly.
  • The allowance for owners/operators of stationary emergency RICE to operate their engines as part of an emergency demand response program for up to 100 hours per year (including hours spent for maintenance and testing).  This allowance was increased from 15 hours per year included in the original 2010 RICE MACT amendments.  Also, existing emergency stationary RICE at area sources can operate up to 50 hours per year to provide local system reliability.  These 50 hours would be counted towards the 100 hours/year allowance for maintenance and testing purposes.  With these amendments, EPA has added a provision for emergency CI RICE > 100 HP enrolled in emergency demand response and system reliability programs to burn ultra-low sulfur diesel fuel and record operational hours beginning January 1, 2015.  The definition of emergency engine has been revised in these most recent rule amendments to reflect these changes with respect to demand response participation.  Similar updates were made to NSPS IIII and JJJJ to make the demand response requirements/limitations consistent across all stationary engine rules.  EPA is also extending the applicability of these provisions to existing stationary emergency engines greater than 500 HP at major sources of HAPs.  This category of engines was previously not covered by the 2010 RICE MACT amendments.
  • A provision for existing emergency engines located at area sources to participate in peak shaving (non-emergency demand response) for up to 50 hours per year prior to May 3, 2014.  Currently, there are no federal restrictions on such engines with respect to participation in peak shaving.
  • The creation of a subcategory for existing spark ignition engines located in sparsely populated areas.   Owners/operators of existing stationary non-emergency 4-stroke lean burn (4SLB) and 4-stroke rich burn (4SRB) RICE > 500 HP at area sources that are located in sparsely populated areas remote from human activity are now subject to work practices rather than numerical emissions limits and associated testing and monitoring as originally promulgated.  Remote area is defined as either a Department of Transportation (DOT) Class 1 pipeline location or, if the engine is not on a pipeline, if within a 0.25 mile radius of the facility there are 5 or fewer buildings intended for human occupancy.  For 4-stroke engines greater than 500 HP at area sources located in populated areas, EPA is adopting an equipment standard requiring the installation of a catalyst and associated monitoring to reduce HAP emissions.  These sources are required to test their engines to demonstrate compliance initially, and thereafter only need to perform catalyst activity check-ups and either monitor the catalyst inlet temperature continuously or employ high temperature shutdown devices to protect the catalyst.
  • Additional miscellaneous clarifications, corrections and provisions.  These include some changes with more limited applicability, such as broadening the definition of remote area sources in Alaska and allowing extended compliance deadlines for engines that will need to be upgraded to meet more stringent local or state regulations.

In consideration of the 2013 compliance deadlines for subject stationary RICE, it is critical for owners and operators  to assess specific applicability and compliance obligations closely while bearing the following in mind:

  • HAP status: Is your site a major source or an area source of HAPs?
  • Facility location:  Is your engine located in a sparsely populated area remote from human activity?  Is your engine located in Alaska?  Is your engine located in a state or local district that will require the installation of controls/upgrades to meet more stringent local standards?
  • Stationary determination: Is your RICE stationary or does it qualify as a non-road/mobile/portable engine?
  • Engine dates: Is your stationary RICE "new", "existing", or "reconstructed"? When was the stationary RICE installed, built, purchased, reconstructed or modified?
  • Purpose of RICE: Is your stationary RICE meant to serve emergency or non-emergency use? If you consider your stationary RICE to be for emergency use only, does it meet the regulatory definition for such use? 
  • Fuel type: Is your stationary RICE fueled by diesel, natural gas, gasoline, propane, or landfill gas?
  • Engine type: What is your stationary RICE's horsepower rating? Is it a 2 stroke (2S), 4 stroke (4S), lean burn (LB) or rich burn (RB) stationary RICE?

The RICE MACT is among the most complex and confusing regulations in EPA's entire suite of NSPS and NESHAP regulations and includes a slew of requirements related to testing, notifications, reporting, and recordkeeping. Trinity has tools available to assist in your RICE MACT applicability determinations. To determine whether the RICE MACT has been evaluated accurately at your facility and address its future compliance, contact your local Trinity office at (800) 229-6655.