1 

MEMORANDUM 

DATE: June 26, 2008 

SUBJECT: Existing Population of Stationary RICE 

FROM: Tanya Parise, Alpha-Gamma Technologies, Inc. 

TO: Jaime Pagán, EPA Energy Strategies Group 

The purpose of this memorandum is to present the population of existing 

stationary reciprocating internal combustion engines (RICE) that will be used to 

estimate the national impacts of the national emission standards for hazardous air 

pollutants (NESHAP) for this source category. This memorandum addresses existing 

stationary RICE less than and equal to 500 horsepower (HP) located at major sources 

of HAP emissions and existing stationary RICE of all sizes located at area sources of 

HAP emissions. 

The population of existing stationary RICE is based on information in the Power 

Systems Research’s (PSR) North American Engine PartsLink Database provided by the 

U.S. EPA Office of Transportation and Air Quality. EPA has previously discussed the 

appropriateness for using estimates developed by PSR (see Attachment A to Document 

ID Number EPA-HQ-OAR-2005-0029-0007, available from http://www.regulations.gov.) 

 

 Population estimates have previously been developed for the new source 

performance standards (NSPS) for spark ignition (SI) and compression ignition (CI) 

stationary engines. These memoranda can be obtained from 

http://www.regulations.gov as Document ID Numbers EPA-HQ-OAR-2005-0030-0015, 

EPA-HQ-OAR-2005-0030-0063, and EPA-HQ-OAR-2005-0029-0007. 

Existing Population of Engines

The existing population of engines in the U.S. was based on using the 

information from PSR’s database as the baseline population. The baseline year for CI 

engines was 1998 and the baseline year for SI engines was 2002. The baseline 

population numbers are provided in Table 1. To estimate the existing population in 

2008, engine sales information from PSR was used to project the number of new 

engines that would be sold in the years 1999 through 2007 for CI engines and 2003 

through 2007 for SI engines. EPA applied the same method for determining the number 

of new stationary engines as was done under the CI and SI NSPS. The methodology 
2 

applied to estimate the current population of engines was described in the memoranda 

referenced on page 1 of this memorandum. 

Table 1. Baseline Population of CI and SI Stationary Engines 

(includes all engines at major and area sources)

HP Range Population 

SI (as of 2002) CI (as of 1998) 

25-50 109,075 0 

50-100 21,815 124,064 

100-175 44,262 197,076 

175-300 9,755 130,744 

300-600 9,554 140,058 

600-750 1,116 24,359 

>750 10,369 47,478 

Total 205,946 663,780 

EPA applied the same assumptions that were used to develop the projected 

number of new engines under the CI and SI NSPS for consistency across rulemakings 

addressing similar or the same engines. The main assumptions used to develop the 

necessary population estimates for this rulemaking are as follows: 

• No stationary CI engines below 50 HP. 

• No stationary SI engines below 25 HP. 

• Percent of stationary RICE located at major sources: 40% 

• Percent of stationary RICE located at area sources: 60% 

• CI engines breakdown: 

o Percentage that are prime engines: 20% 

o Percentage that are emergency engines: 80% 

• New SI engines breakdown1,2:

<1,000 HP

o Percentage that are 4SLB: 53% 

o Percentage that are 4SRB: 47% 

1,000-5,000 HP

o Percentage that are 4SLB: 75% 

o Percentage that are 4SRB: 25% 

>5,000 HP

o All 4SLB 

 

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The breakdown for existing engines is 11%, 47%, and 42% for 2SLB, 4SLB, and 4SRB, respectively. 

2

2SLB engines represent less than 0.1 percent of new stationary SI engines. 
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The estimated total existing population of stationary engines and the population of these 

engines at major and area sources is presented in Tables 2, 3, and 4, respectively. 

Table 2. Total 2008 Population of Stationary RICE 

Size Range 

(HP) 

Existing Population 

(2008) 

SI Engines CI Engines 

25-50 142,667 0 

50-100 41,569 262,505 

100-175 76,262 328,759 

175-300 22,576 254,778 

300-600 18,134 191,239 

600-750 1,909 31,807 

>750 21,530 79,976 

Total 324,646 1,149,064 

Table 3. 2008 Population of Stationary RICE at Major Sources 

Size Range 

(HP) 

Existing Population 

Major Sources (2008) 

SI Engines CI Engines 

25-50 57,067 0 

50-100 16,628 105,002 

100-175 30,505 131,504 

175-300 9,030 101,911 

300-500 4,836 50,997 

Total 118,065 389,414 

Table 4. 2008 Population of Stationary RICE at Area Sources 

Size Range 

(HP) 

Existing Population 

Area Sources (2008) 

SI Engines CI Engines 

25-50 85,600 0 

50-100 24,941 157,503 

100-175 45,757 197,255 

175-300 13,545 152,867 

300-600 10,881 114,744 

600-750 1,145 19,084 

>750 12,918 47,986 

Total 194,788 689,438 
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Information received from and developed in conjunction with the Engine 

Manufacturer’s Association (EMA) in order to determine how the population of existing 

CI engines is distributed over various model years is presented in Table 5. A similar 

version of this information was presented in the Advanced Notice of Proposed 

Rulemaking (73 FR 4136). Note that this table is based on earlier population estimates 

and does not match the updated estimates presented in Tables 2 through 4 of this 

memorandum. Table 5 is intended to present an overview of how engines are 

distributed over different model years. The percentages of older engines to newer 

engines is what is relevant in the below table. 

Table 5. Breakdown of Stationary CI RICE by Model Year 

Size 

Range 

(HP)

<1980 1980-

1994 

1994-

2001 

2002-

2005 

Pre1994 1994-

2005 

Totals 

50-100 26,200 62,759 49,919 22,521 88,959 72,440 161,399 

100-175 57,426 92,857 61,572 23,634 150,283 85,206 235,489 

175-300 27,198 63,991 57,739 40,877 91,189 98,616 189,805 

300-600 70,303 53,188 38,778 31,403 123,491 70,181 193,672 

600-750 8,562 12,664 10,743 8,648 21,226 19,391 40,617 

>750 6,899 28,357 33,835 10,520 35,256 44,355 79,611 

Total 196,588 313,816 252,586 137,603 510,404 390,189 900,593 
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References

1. Memorandum from Tanya Parise, Alpha-Gamma Technologies Inc. to Sims Roy, 

U.S. Environmental Protection Agency, OAQPS ESD Combustion Group. June 

20, 2005. Population and Projection of Stationary Engines (EPA-HQ-OAR-2005-

0029-0007). 

2. Memorandum from Tanya Parise, Alpha-Gamma Technologies Inc. to Sims Roy, 

U.S. Environmental Protection Agency, OAQPS ESD Combustion Group. April 

5, 2006. Population and Projection of Stationary Spark Ignition Engines (EPAEPA-HQ-OAR-2005-0030-0063.) 

3. Memorandum from Bradley Nelson, Alpha-Gamma Technologies Inc. to Jaime 

Pagán, U.S. Environmental Protection Agency, EPA Energy Strategies Group. 

April 5, 2006. Population and Projection for Stationary RICE at Major and Area 

Sources (EPA-HQ-OAR-2005-0030-0015). 

4. Memorandum from Melanie Taylor and Chuck Zukor, Alpha-Gamma 

Technologies Inc. to Sims Roy and Jaime Pagán, EPA OAQPS ESD Combustion 

Group. June 22, 2004. Decision on Using Estimates from PSR or the RICE 

NESHAP Population Database for Engines above 500 Horsepower (EPA-HQOAR-2005-0029-0007).