  SEQ CHAPTER \h \r 1    

MEMORANDUM

DATE:		August 10, 2010

SUBJECT:	Emission Factors for Existing Stationary SI RICE

FROM:	Bradley Nelson, EC/R, Inc.

		

TO:		Melanie King, EPA OAQPS/SPPD/ESG

1.0	PURPOSE

	The purpose of this memorandum is to present the hazardous air
pollutants (HAP), volatile organic compounds (VOC), carbon monoxide (CO)
and nitrogen oxides (NOx) emission factors that were used for existing
stationary spark ignition (SI) reciprocating internal combustion engines
(RICE) in order to estimate impacts under the national emission
standards for hazardous air pollutants (NESHAP) that these engines are
subject to.

2.0	INTRODUCTION

EPA used information presented in the Compilation of Air Pollutant
Emission Factors (AP-42) to estimate HAP emission factors for 2-stroke
lean burn (2SLB), 4-stroke lean burn (4SLB), and 4-stroke rich burn
(4SRB) engines for the final NESHAP.  The trace organic compounds that
were defined by section 112(b) of the Clean Air Act as HAP were summed
for each engine type (i.e., 2SLB, 4SLB, 4SRB).  Based on comments
received during public comment interagency review period, EPA determined
that the AP-42 emission factors for HAP would be the most appropriate
and representative to estimate HAP emissions from existing SI engines.

For CO and NOx, EPA developed emission factors for existing stationary
SI engines using test data from the RICE Emissions Database and
supplemented this data, to the extent all information was available,
with emissions data received after the proposal.  The following sections
describe how EPA estimated HAP emission factors from AP-42 information
and CO and NOx emission factors from available emissions data.

3.0	METHODOLOGY FOR DEVELOPING EMISSION FACTORS

	The following section describes the methodology used to develop
emission factors for existing SI engines.  These methodologies were
developed by EPA and used to calculate AP-42 emission factors.  These
methodologies include:

Data Collection and Review,

Data Evaluation and Analysis,

Emission Data Grouping,

Development of Emission Factors.

The data collection and review process included the collection of test
reports that were submitted during the comment period.  The pollutant
test data from the new test reports were added to the existing dataset
to create a revised pollutant data set.  The data evaluation step
included the review of the new test reports to verify that the data was
of proper quality and included the necessary quality assurance and
quality control data (QA/QC).  The emission data grouping step included
separating the data by engine type (2SLB, 4SLB, 4SRB) and pollutant. 
The data sets were further grouped by facility and by engine model.  The
development of emission factors step involved averaging the pollutant
test runs for each engine model located at a facility.  The average
emission factors from each engine model at a facility were then averaged
to calculate the pollutant emission factor for that engine type. 
Section 4.0 presents a summary of the results of the emission factor
development for each of the engine types.

4.0	EMISSION FACTORS

	The HAP emission factors for each of the engine types were calculated
using the Trace Organic Compound emission factors presented in the
Compilation of Air Pollutant Emission Factors (AP-42).  The trace
organic compounds that were defined by section 112(b) of the Clean Air
Act as HAP were summed for each engine type (i.e., 2SLB, 4SLB, 4SRB). 
The resulting engine type AP-42 HAP emission factor was then converted
from pounds per million British Thermal Units (lb/MMBtu) to pounds per
horsepower-hour (lb/HP-hr) using the following equation:  

lb/HP-hr = lb/MMBtu * 0.002546 MMBtu/HP-hr/0.34

where 0.34 is the assumed efficiency for a SI engine.

	

	The VOC emission factor was calculated by dividing the HAP emission
factor in lb/HP-hr for each engine type by 0.194, which was the HAP/VOC
ratio that was established and used to estimate impacts under the New
Source Performance Standards for SI engines and NESHAP for stationary
RICE promulgated in 2008.  

The CO and NOx test data from the RICE Emissions Database were used to
calculate CO and NOx emission factors for each engine type.  In
addition, CO test data received during the comment period was included
in the emission data set for 4SLB and 4SRB engines.  The CO and NOx
emission factors were calculated first by averaging the test data from
each engine model at a facility for each engine type.  The averages of
each of these engine models were then averaged to calculate a CO and NOx
emission factor for the engine type.  A summary of the test data and
calculations for the CO and NOX emission factors are presented in
Appendix A of this memorandum.

Table 1.  Summary of SI Engine Emission Factors

Engine Type	Emission Factor

(lb/HP-hr)

	HAP	VOC	CO	NOx

2SLB	5.96E-04	3.07E-03	1.06E-02	4.18E-02

4SLB	5.41E-04	2.78E-03	3.92E-03	1.15E-02

4SRB	2.43E-04	1.25E-03	1.93E-02	1.47E-02





Appendix A

2SLB, 4SLB, and 4SRB CO and NOX Test Data 



Test Data used for 2SLB Engine CO Emission Factor Determination



Test Data used for 4SLB Engine CO Emission Factor Determination



Test Data used for 4SRB Engine CO Emission Factor Determination



Test Data used for 2SLB Engine NOX Emission Factor Determination



Test Data used for 4SLB Engine NOX Emission Factor Determination



Test Data used for 4SRB Engine NOX Emission Factor Determination

 U.S. Environmental Protection Agency, Procedures For Preparing Emission
Factor Document, November 1997, EPA-454/R-95-015 REVISED.

 Compilation of Air Pollutant Emission Factors, Volume I Stationary
Point and Area Sources, Fifth Edition, Chapter 3: Stationary Internal
Combustion Sources, Section 3.2 Natural Gas-fired Reciprocating Engine,
August 2000.

(≤500 HP) Stationary Reciprocating Internal Combustion Engines (RICE),
April 13, 2004 (EPA-HQ-OAR-2005-0030-0009). 

	

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h Proposed NSPS for Stationary SI ICE and NESHAP for Stationary RICE,
May 11, 2006 (EPA-HQ-OAR-2005-0030-0059).

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