CASE STUDIES OF STATIONARY 

RECIPROCATING DIESEL ENGINE 

RETROFIT PROJECTS 

August 2007 

Manufacturers of Emission Controls Association 

1730 M Street, NW * Suite 206 * Washington, DC 20036 

www.meca.org

www.dieselretrofit.org
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Table of Contents 

1.0 Introduction................................................................................................................. 1 

2.0 Stationary Diesel Engine Case Studies...................................................................... 3 

2.1 Demonstration of Emission Control Technologies on Diesel-Fueled 

Backup Generators ....................................................................................................... 3

 2.2 The Simultaneous Reduction of NOx, PM, HC and Co from Large 

Stationary Diesel Engines Using SCR and Particulate Filters .................................... 5 

 2.3 Kings County, CA, Department of Public Works................................................... 7 

 2.4 National Steel and Shipbulding Company (NASSCO)........................................... 8 

 2.5 Pacific Bell-SBC Telecommunications Facility..................................................... 8 

 2.6 Santa Clara County Building Operations.............................................................. 9 

 2.7 Sierra Nevada Brewing Company, Chico, CA..................................................... 10 

 2.8 Memorial Hospital of Los Banos, Los Banos, CA ............................................... 10 

 2.9 Fresno Regional Medical Center, Fresno, CA .................................................... 11 

 2.10 New Jersey Department of Environmental Protection Stationary Diesel 

Particulate Filter Project............................................................................................ 11 

 2.11 Intel Corporation, San Jose, CA........................................................................ 11 

 2.12 Demonstration of a NOx Control System for Stationary Diesel Engines .......... 11 

 2.13 Evaluation of NH3-SCR Catalyst Technology on a Stationary Diesel 

Genset ......................................................................................................................... 13 

 2.14 Additional SCR Projects .................................................................................... 13 

3.0 Summary.................................................................................................................... 14 
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1.0 Introduction 

Diesel engines provide important fuel economy and durability advantages for 

stationary diesel reciprocating engines. Although they are often the power plant of 

choice for stationary applications, they have the disadvantage of emitting significant 

amounts of particulate matter (PM) and oxides of nitrogen (NOx), and lesser amounts of 

hydrocarbon (HC), carbon monoxide (CO), and toxic air pollutants. 

Stationary diesel engines are significant contributors to air pollution in many 

cities in the U.S. It is estimated that there are some 600,000 existing stationary diesel 

engines that are in use nationwide, with electrical generators accounting for more than 

half of the total. The population of stationary diesel engine is expected to continue to 

grow. In efforts to address air pollution from stationary diesel engines, the U.S. EPA 

issued its final requirements to reduce emissions of air pollutants from stationary CI 

engines on June 28, 2006. The final standards, known as New Source Performance 

Standards (NSPS), limit emissions of nitrogen oxides (NOx), particulate matter (PM), 

sulfur dioxide (SO2), carbon monoxide, (CO), and hydrocarbons (HC) from stationary 

diesel engines to the same stringent levels required by EPA’s Tier 4 nonroad diesel 

engine regulations (see 

http://www.epa.gov/ttn/caaa/t3/fact_sheets/ci_nsps_fnl_fs.html#moreinfo). 

In addition, as part of the Diesel Risk Reduction Plan, California Air Resources 

Board adopted the Airborne Toxic Control Measure (ATCM) for Stationary Compression 

Ignition Engines on September 9, 2005. Stationary diesel engines emit approximately 

950 tons per year of diesel PM in California and the goal of this regulation is to reduce 

diesel PM and criteria pollutant emissions from stationary diesel engines through 

stringent emission limits and operational requirements (see 

http://www.arb.ca.gov/diesel/statport.htm). In order to ensure that a particular emission 

control technology achieves certain level of PM emissions reduction, ARB created a 

technology verification program. Currently, ARB has six PM retrofit technologies 

verified for stationary diesel engine applications. Majority of the verified technologies 

are diesel particulate filters (DPFs), with one system incorporating DPF with an exhaust 

gas recirculation (EGR) system, achieving PM reduction of 85 percent and greater. The 

EGR and DPF technology is also verified for 50 percent NOx reduction. ARB list of 

verified retrofit technologies for stationary diesel engines can be found at: 

http://www.arb.ca.gov/diesel/verdev/vt/stationary.htm. 

The case studies discussed in this paper focus on those projects that have been 

completed, or are in progress for retrofitting stationary diesel engines with emission 

controls technologies such as diesel oxidation catalysts (DOCs) and DPFs for controlling 

diesel PM emissions, and selective catalytic reduction (SCR) catalysts for controlling 

NOx emissions. Many of the projects highlight the feasibility of installing verified onroad technologies on stationary diesel engines and relate some of the lessons learned that 

may assist others in planning additional stationary projects. This paper focuses on 

technology based strategies and where available, provides information on specific type of 

technology installed on the type of stationary diesel engines, and the emission reduction 
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that was achieved. More basic information on available emission control retrofit 

technologies is available in MECA’s whitepaper, Retrofitting Emissions Controls on 

Diesel-Powered Vehicle (www.dieselretrofit.org). 

2.0 Stationary Reciprocating Engine Diesel Retrofit Case Studies: 

2.1 Demonstration of Emission Control Technologies on Diesel-Fueled Backup 

Generators 

 The University of California, Riverside (UCR) Bourns College of Engineering – 

Center for Environmental Research and Technology (CE-CERT), as part of the California 

Public Interest Energy Research (PIER) Program, conducted research to measure criteria 

and toxic emissions from a number of uncontrolled diesel-fueled backup generators 

(BUGs) that were representative of those used in California. The project was later 

expanded to incorporate a demonstration program of emission control technology. The 

objectives of this portion of the research were to assess applicable environmental control 

technologies and conduct field tests of BUGs units and control alternatives. 

 During the demonstration project, eight PM control technologies were 

demonstrated, including fuel modification, addition of emissions control retrofit 

technology and combination of both. The durability time of the technology was set to 

167 hours to allow the control technology participants to obtain a conditional verification 

with ARB. The ARB, the Energy Commission, and UCR chose the emission control 

devices based on key elements: the technology’s state of commercialization; the 

willingness of the vendor to supply the technology at no cost; and the need for that 

technology type in the demonstration matrix. The following devices were chosen: 

• Water emulsified fuel (20% water emulsification) 

• Diesel oxidation catalyst (DOC) 

• Active diesel particulate filter (DPF) with online filter regeneration by electrical 

heating 

• Catalyzed DPF (passive DPF) 

• DOC with fuel-borne catalyst 

• Fuel-borne catalyst with DPF 

The engine models that were selected for testing were: 1985 Detroit Diesel (DDC) 

V92 two-stroke diesel engine installed in a 300 kW generator and 2000 Caterpillar 3406 

C four-stroke diesel engine installed in a 350 kW generator. 

 

Emulsified Fuel

The emulsified fuel consisted of a blend of water, conventional diesel fuel, and a 

mixture of special compounds that was added to the fuel to maintain the emulsion, 

enhance cetane number and lubricity, inhibit corrosion, and protect against freezing. The 

formulated fuel contained 77 percent diesel fuel, 20 percent water, and 3 percent additive 

package. This fuel might not be of interest for applications like emergency generators, 
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because the fuel needs to be circulated in order to prevent the suspension from breaking 

down into hydrocarbon and water phases. CE-CERT tested the emulsified fuel in two 

engines, first a modern and post-control (after 1996) unit and second, a unit from 1986 

from the same manufacturer. The fuel tested on the modern BUG showed reductions for 

all load points and an overall reduction in the emission factors of 69 percent and 13 

percent for PM and NOx, respectively. Test with the second BUG, a 1986 CAT 3406B, 

showed less of a reduction in both PM and NOx with the overall reduction of 25 percent 

PM and 4 percent NOx. Because PM reduction is linked to a reduction in the diesel oil 

droplet size in the cylinder and to the injection pressure, CE-CERT believes that the 

much lower injector pressure used on this unit did not provide the same capability of 

reducing droplet size, leading to the reduce effectiveness in reducing PM and NOx. 

Diesel Oxidation Catalyst

 

 Two DOCs, DOC-1 and DOC-2, were installed on a modern CAT 3406C engine. 

DOCs are not expected to be very effective in reducing the solid or elemental carbon 

portion of the diesel exhaust associated with PM. Therefore, the overall reduction 

effectiveness of DOCs depends on the proportion of the PM that is volatile. For DOC-1, 

PM was reduced by 25 percent and NOx was increased by 6 percent. For DOC-2, PM 

was reduced by 6 percent and showed no change in NOx. 

Passive Diesel Particulate Filter

 The passive DPF system used during this demonstration comprised of a 

proprietary platinum-based oxidation catalyst installed upstream of a wall-flow 

particulate filter typically made of cordierite. The platinum catalyst oxidizes a proportion 

of the NO in the exhaust stream to form NO2 and this NO2 is used to combust the soot 

trapped in the DPF. Two passive DPFs (DPF-1 and DPF-2) were retrofitted on a 

MY2000 Caterpillar 3406C diesel generator. Initial emission testing of DPF-1 resulted in 

control efficiencies for PM of just below 85 percent, which is lower than expected. 

When the device was opened, black streaks were noted on the white filter, indicating that 

a leak around the ceramic monolithic filter and housing had occurred. The DPF-1 was 

repaired. The control efficiency of DPF-2 was measured at 91 percent for PM, 98 

percent for non-methane hydrocarbon (NMHC), and 76 percent for CO. Total NOx for 

DPF-2 decreased about 9 percent from the uncontrolled BUG’s emissions. 

 

Active Diesel Particulate Filter

 The active DPF system comprised of three silicon carbide diesel particulate filters 

with an electrical regeneration system designed to provide continuous PM control. The 

triple filter system provides uninterrupted emission filtration during regeneration by 

switching the exhaust flow between filters. The components of the system are the 

ceramic wall-flow filter elements, electronic control unit (ECU), electrical heater system, 

compressed air blower system, and valve system to switch the exhaust flow between 

filters. Because the system operates in two distinct modes, soot and regeneration, 

emission testing was performed in triplicate for both modes. The emission test results 
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show a greater than 99 percent reduction in PM for both modes. Additionally, NMHC 

was reduced by about 45 percent and NOx by 10 percent. Although the PM reduction 

was very high, this system had two areas of concern: 1) Backpressure levels measured 

during durability were higher than expected. The device manufacturer attributes this to 

differences in engine exhaust flows and exhaust hardware between the Caterpillar 3300 

and 3400 Series engines. Presumably, the issue associated with the higher backpressure 

could easily be addressed during the design phase of stationary source retrofitting. 2) 

During the intermittent cold start portion of durability cycling, the soot mode was longer 

than had been indicated by the manufacturer. As a result, filters were not regenerating as 

often as described during cold start operation and backpressure increased. Because the 

regeneration system is controlled only by time and not backpressure sensors, this control 

scheme may need optimization for applications with multiple cold starts. 

Fuel-borne Catalyst and Diesel Oxidation Catalyst

 Originally, a flow-through filter system was retrofitted on a 1985 MY 2-stroke 

Detroit Diesel V92. This system was a passive, flow-through filter combined with a fuelborne catalyst to reduce PM emissions. A DOC, also part of the system, reduced CO and 

HC emissions. However, this system experienced regeneration problems during 

degreening operation. The exhaust temperatures were not sufficient for regeneration and 

the flow-through filter clogged. Therefore, the flow-through filter was removed and the 

DOC, combined with the fuel-borne catalyst, was tested. The fuel-borne catalyst that was 

used contained 4-8 ppm of cerium and platinum in a petroleum distillate solution. The 

control efficiency of the DOC and fuel-borne catalyst system was 38 percent for PM and 

69 percent for NMHC and NOx increased by approximately 4.8 percent. 

Fuel-borne Catalyst and Diesel Particulate Filter

 

 The DPF used in this demonstration is an uncatalyzed ceramic wall flow filter 

combined with a fuel-borne catalyst. This system was installed on a 2000 MY Caterpillar 

3406C diesel generator. The system combines a ceramic monolith trap with a fuel-borne 

catalyst to facilitate regeneration of the DPF. Results from the testing showed that the 

fuel/emission control device combination reduced PM by more than 99 percent for both 

the initial test and after the durability testing. 

More information on this project is available at: 

http://www.energy.ca.gov/pier/final_project_reports/CEC-500-2005-049.html. 

2.2 The Simultaneous Reduction of NOx, PM, HC and CO from Large Stationary 

Diesel Engines Using SCR and Particulate Filters 

In late 2003, Snow Summit Mountain Resort purchased generators to use during 

the winter months to make snow. The resort is located at Big Bear Lake and since the 

area only gets an average of 75 inches of annual snow fall, Snow Summit actually makes 
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an addition 36 to 60 inches of snow to cover the trails. Because the Snow Summit 

Mountain Resort comes under the jurisdiction of the South Coast Air Quality 

Management District (SCAQMD), the air permit for the diesel engines required the 

installation of the Best Available Control Technology (BACT) to control emissions from 

these engines. Table 1 below shows the uncontrolled baseline emissions from the 

purchased diesel engine, the SCAQMD regulated emissions level and the required 

percent reduction needed. 

Table 1: Diesel Generator Engine Uncontrolled Emissions and 

SCAQMD Emissions Limits 

Emission Baseline Levels Regulation Levels % Reduction Required 

NOx 8.75 g/bhp-hr 0.60 g/bhp-hr 93.2% 

CO 0.72 g/bhp-hr 0.60 g/bhp-hr 16.7% 

HC 0.20 g/bhp-hr 0.15 g/bhp-hr 25% 

PM 0.30 g/bhp-hr 0.045 g/bhp-hr 85% 

 The supplier of emissions control devices chose to install a combination of 

Selective Catalytic Reduction (SCR) for reducing NOx and a diesel particulate filter 

(DPF) system on two diesel generators. The DPF that was installed on the generators are 

a passive continuously regenerating filter technology that incorporates platinum 

regenerated by the oxidization of NO to NO2. The NO2 in turn combusts the soot that is 

collected in the DPF to regenerate the DPF. The SCR system that was installed uses a 

two-fluid technology of urea and compressed air. 

Emissions Testing Results

 Table 2 and Table 3 show emissions test results from each engines. 

Table 2: Test Results from Engine #1 

Pollutant SCAQMD Emissions 

Limit at 15% O2 

Actual 

Emissions 

% Reduction 

Targeted 

% Reduction 

Achieved 

PM10 0.045 g/bhp-hr <0.005 g/bhp-hr 85% >90% 

NOx 50 ppm 34.90 ppm 93.2% >94% 

TNMEHC 39 ppm 

0.15 g/bhp-hr 

10.80 ppm 

0.05 g/bhp-hr 25% >90% 

NH3 10 ppm 0.01 ppm Surpassed 

Table 3: Test Results from Engine #2 

Pollutant 

SCAQMD 

Emissions Limit at 

15% O2

Actual Emissions % Reduction 

Targeted 

% Reduction 

Achieved 

PM10 0.045 g/bhp-hr <0.005 g/bhp-hr 85% >90% 

NOx 50 ppm 44.27 ppm 93.2% >94% 

CO 89 ppm 3.62 ppm 16.7% >90% 

TNMEHC 39 ppm 

0.15 g/bhp-hr 

3.18 ppm 

0.02 g/bhp-hr 25% >75% 

NH3 10 ppm 0.00 ppm Surpassed 
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 The low PM values, combined with the low NOx, CO, and HC emissions at the 

stack demonstrate that the criteria pollutants from a diesel engine can be simultaneously 

controlled by the DPF and SCR technologies. 

 More information on this project is available at: 

http://www.nj.gov/dep/airworkgroups/docs/1chu.attachment5.pdf. 

2.3 Kings County, CA, Department of Public Works 

 Kings County, located in California’s San Joaquin Valley, subscribes to an 

interruptible power program with the local utility in order to save on electricity costs. As 

a program participant, the county receives a 25 percent lower rate on electricity but must 

disconnect from utility grid after being given 30-minute notice. If the county fails to 

disconnect in 30 minutes, it must pay a large penalty. After a period of frequent 

interruptions during the winter of 2000/2001, the County Council authorized the 

installation of a large generator to supply backup power to most facilities located in the 

Government Center in Hanford. A Caterpillar 3516BB engine powers the backup 

generator and in order to comply with air quality regulations for diesel generators that run 

during voluntary power interruptions, the county installed a DPF system on the engine. 

Installation of the filter system was a collaborative effort involving the County, the 

system supplier, and the filter installer. The generator engine burns ultra-low sulfur 

diesel fuel. 

 

 Engine emissions testing results before and after installation of the DPFs are 

summarized in the table below. Emissions before DPF system installation were provided 

by Caterpillar, Inc. and represent emissions for the engine operating at 50 percent load, 

the average load the engine carries at the Government Center. Engine-out emissions for 

PM were also reduced by 25 percent as suggested by Caterpillar, Inc. to account for the 

use of cleaner burning California diesel fuel. The DPF was removed after 556 hours to 

inspect soot buildup, which would indicate if the DPF was regenerating properly. The 

inspection results revealed very clean filters, indicating that the engine was reaching and 

sustaining adequate temperatures to ensure regeneration. 

Emissions Reduction Summary 

Pollutant Emission Rate Before 

Control (g/bhp-hr) 

Emission Rater After 

Controls (g/bhp-hr) Percent Reduction 

CO 0.84 0.084 90 

HC 0.33 0.033 90 

PM 0.179a 0.027a 85 

NOx 6.51 NAb NAb

a

 PM emission rate reduced by 25% per Caterpillar, Inc. to account for lower PM emissions from CARB 

diesel fuel 

b

 Not applicable 
8

More information on this project is available at: 

www.nescaum.org/documents/rpt030612diselgenerators.pdf. 

2.4 National Steel and Shipbuilding Company (NASSCO) 

 

NASSCO, located on San Diego Bay, is the largest shipyard engaged in new ship 

construction on the West Coast and builds commercial ships including oil tankers, ferries, 

container ships and research vessels. In 2001, NASSCO purchased a Cummins QST30-

G1 diesel engine and generator to power Crane Number 16, a 300-ton gantry crane. In 

order to meet air quality requirements, the engine was equipped with a DPF to control 

PM and a selective catalytic reduction (SCR) unit to reduce NOx emissions. To keep the 

exhaust gas temperature high enough for the proper operation of DPF and SCR system 

exhaust gas heaters were installed ahead of the emission control system. NASSCO uses 

California #2 diesel fuel to operate Crane Number 16. 

Engine emissions before and after installation of emission controls are 

summarized in the table below. The emissions rates for the engine before the installation 

of emission control devices are from Cummins, Inc. Emissions reductions are based on 

the performance claims of the emission control manufacturer and reflect the typical 

values observed in similar applications. The emission control installer estimates the DPF 

achieves an 85 percent reduction of PM and the SCR unit achieves a 90 percent reduction 

of NOx. Source tests were conducted on the crane by World Environmental, Inc. on 

March 14, 2002 and preliminary source test data confirm the SCR system achieves a 

>90% reduction in NOx. 

Emissions Reduction Summary 

Pollutant Emission Rate Before 

Controls (g/bhp-hr) 

Emission Rate After 

Controls (g/bhp-hr) 

Percent 

Reduction 

CO 0.2 0.85 85 

HC 1.1 0.10 85 

PM 0.03a 0.045a 85 

NOx 8.1b 0.69b 93 

a PM emission rates reduced 25% per Caterpillar, Inc. to account for lower PM emissions from California 

diesel fuel. 

B Nox emission rates reduced 7% per Caterpillar, Inc. to account for lower Nox emissions from California 

diesel fuel. 

More information on this project is available at: 

www.nescaum.org/documents/rpt030612diselgenerators.pdf. 

2.5 Pacific Bell-SBC Telecommunications Facility 

In 1994, the Pacific Bell-SBC installed two emergency generators at their highrise telecommunications facility in San Francisco, CA. To accommodate growth, Pacific 

Bell replaced a turbine with two Caterpillar 3516 engines and their associated generators. 
9

In order to mitigate complaints of smoke and odors, Pacific Bell installed DPF systems 

on the engines. The installed filter systems are capable of reducing PM emissions by 

85% and carbon monoxide and hydrocarbon emissions by 90%. The engine uses regular 

#2 diesel fuel. 

Expected engine emissions before and after installation of the DPFs are 

summarized in table below. 

Emissions Reduction Summary 

Pollutant Emission Rate Before 

Controls (g/bhp-hr) 

Emission Rate After 

Controls (g/bhp-hr) Percent Reduction 

CO 1.17 0.12 90 

HC 0.50 0.05 90 

PM 0.239 0.036 85 

NOx 17.04 NA NA 

 More information on this project is available at: 

www.nescaum.org/documents/rpt030612diselgenerators.pdf. 

2.6 Santa Clara County Building Operations 

 

 Santa Clara County operates a back-up generator in San Jose, CA. The generator 

provides emergency back-up power to three buildings. In 1998, Santa Clara County 

purchased the Cummins KTTA50-G2 diesel engine and generator to provide emergency 

power for the County Service Center. To avoid complaints of smoke and odors, Santa 

Clara County installed two catalyzed DPFs on the engine exhaust system. The engine 

uses CARB diesel fuel #2. 

 Expected engine emissions before and after installation of the filter system on the 

engine are summarized in the table below. Emissions reductions are based on 

preliminary source test results provided by the emission control manufacturer for a 

similar emission control system installed at another facility. 

Emissions Reduction Summary 

Pollutant Emission Rate Before 

Controls (g/bhr-hr) 

Emission Rate After 

Controls (g/bhp-hr) Percent Reduction 

CO 2.17 0.22 90 

HC 0.14 0.01 90 

PM 0.083a 0.012a 85 

NOx 12.8 NA NA a

 PM emission rate reduced 25% per Caterpillar, Inc. to account for lower PM emissions from CARB 

diesel fuel. 

More information on this project is available at: 

www.nescaum.org/documents/rpt030612diselgenerators.pdf. 
10

2.7 Sierra Nevada Brewing Company, Chico, CA 

 

 Sierra Nevada Brewing Company (SNBC) purchased two 750 kW generators to 

provide emergency back-up power for brewery operations in 1997 and 1999. Both 

generators are powered by Caterpillar 3412 diesel engines. To meet air quality 

requirements, SNBC installed DPFs on the engines in 1999 and 2000. Two catalyzed 

DPFs were installed in parallel on each engine. The engines operate on CARB diesel fuel. 

 Engine emissions before and after installation of the DPFs are summarized in the 

table below. Emissions before installation of the filter system were provided by 

Caterpillar, Inc. and are emissions for the engine operating at 75% load. SNBC typically 

operates their engines at about 80% load, but the emissions data at 80% were not 

available from Caterpillar, Inc. As suggested by Caterpillar, Inc., uncontrolled engine 

emissions from NOx and PM were reduced by 7% and 25%, respectively, to account for 

the use of cleaner burning CARB diesel fuel. ARB performed source tests on SNBC’s 

engines on March 20-24, 2000. 

Emission Reduction Summary 

Pollutant 

Emission Rate 

Before Controls 

(g/bhp-hr) 

Emission Rate 

After Controls 

(g/bhp-hr) 

Percent Reduction 

CO 0.84 0.084 90 

HC 0.33 0.033 90 

PM 0.164a 0.025a 85 

NOx 6.69b 5.85 12 a PM emission rate reduced 25% per Caterpillar, Inc. to account for lower PM emissions from CARB 

diesel fuel. 

b

 NOx emission rate reduced 7% per Caterpillar, Inc. to account for lower NOx emissions from CARB 

diesel fuel. 

 More information on this project is available at: 

www.nescaum.org/documents/rpt030612diselgenerators.pdf. 

2.8 Memorial Hospital of Los Banos, Los Banos, CA 

 The Memorial Hospital of Los Banos installed a DPF on a 1994 Caterpillar 3406, 

519 horsepower engine operating an emergency backup generator. The DPF was 

installed in 2002 to comply with the San Joaquin Valley Air Pollution Control District 

emission permit requirements. The hospital runs the engine about 30 minutes per week 

for maintenance and testing and the exhaust temperature is monitored during the weekly 

engine test. 
11

2.9 Fresno Regional Medical Center, Fresno, CA 

 Fresno Regional Medical Center installed a catalyzed DPFs on five 2002 

Caterpillar 3516TA, 2680 horsepower engines that power Caterpillar SR4 B emergency 

backup generators. As part of the San Joaquin Valley Air Pollution Control District 

permit, the medical center was required to reduce PM emissions. Emission information 

provided to the medical center stated that a Caterpillar generator produce 0.10 g/bhp-hr of 

PM without an emission control device. The Caterpillar generator running on CARB 

diesel and a DPF has PM emissions reported at 0.01 g/bhp-hr. 

2.10 New Jersey Department of Environmental Protection Stationary Diesel 

Particulate Filter Project 

 

 The New Jersey Department of Environmental Protection (NJDEP), in 

collaboration with the Stevens Institute of Technology and an emissions control 

technology manufacturer, initiated a project to install diesel particulate filters on five 500 

kW electric diesel generators located at the Jersey City Total Energy Plant. This energy 

plant is a co-generation facility that supplies heat and air conditioning. These generators 

were retrofitted with catalytic diesel particulate filters that continuously regenerate at 

normal operating temperatures. The DPF is expected to reduce combined PM, CO and 

HC emissions by at least 85 percent. NJDEP will demonstrate the DPF for six months 

and develop an inventory of diesel engines in New Jersey with the associated yearly 

emission estimates. NJDEP will also determine the applicability of DPFs with respect to 

the New Jersey Inventory of stationary sources in reducing stationary diesel emissions. 

2.11 Intel Corporation, San Jose, CA 

 Intel Corporation installed two DPFs on a Caterpillar 3412C, 896 horsepower 

engine that powers an emergency backup generator. The facilities manager stated that 

they have not had any problems with the DPF and there is no extra maintenance. 

2.12 Demonstration of a NOx Control System for Stationary Diesel Engines 

 The Electric Power Research Institute (EPRI), the California Energy Commission 

(CEC), and Hawaiian Electric Company (HECO) have partnered to further develop an 

emerging emission control technology for retrofitting stationary diesel engines. They 

identified an emissions control device manufacturer having unique technical capabilities 

and a novel design for a cost effective, regenerative lean NOx trap system capable of 

greater than 90 percent reduction and an integrated diesel particulate filter. 

 The manufacturer developed a system which consisted of a fuel processor with a 

third-party, commercial lean NOx adsorber trap that will achieve greater than 90 percent 

NOx reduction. The fuel processor converts diesel fuel to reactive reductants, such as H2
12

and CO to rapidly and completely regenerate the NOx trap. These reductants convert the 

trapped NOx to N2. This system was demonstrated on a 8.3 liter, 160 kW, Cummins 

stationary generator set. The demonstration project is planned in three phases: the 

Technology Demonstration (Phase I), Field Demonstration (Phase II), and Pilot 

Production (Phase III). The goal of Phase I is to demonstrate a NOx reduction 

technology on a 160 kW diesel-fueled reciprocating engine that can be scaled up to a size 

range of 250 to 2,000 kW in Phase II. The measurable objective is to achieve 90 percent 

NOx removal using the selected emission control technology for 100 hours of base-load 

operation and to measure the fuel penalty associated with achieving the 90 percent NOx 

reduction. The Phase I Technology Demonstration was completed in December 2004. In 

Phase II, an ARB-verified, regenerative diesel particulate filter will be integrated into the 

system design (consisting of an Emissions System Control Unit (ESCU), a throttle valve, 

the fuel processor, and lean NOx trap (LNT)) and two units will be developed and 

installed on two diesel engines for field demonstration testing. The goal of this phase is 

to achieve 95 percent NOx reduction. Phase II consists of pre-commercial, limited 

release operation at multiple commercial sites. 

Phase I Technology Demonstration:

Task 1: The manufacturer retrofitted the Cummins 8.3 liter, 160 kW generator set with a 

throttle valve and control system to enable automatic control of the fuel/air mixture. 

Task 2: The emissions control device hardware was designed and fabricated. Several fuel 

processor catalyst materials were evaluated and the most suitable were selected. 

Task 3: Several NOx traps were evaluated for their suitability in the system. 

Task 4: Demonstrate the feasibility of a greater than 90 percent NOx reduction system for 

100 hours on a stationary 160 kW diesel generator set. The measured average fuel 

penalty for the entire test was approximately 7 percent, but this fuel penalty was not 

optimized. 

During Phase I, the cumulative NOx conversion averaged over the entire 100-

hour test was 92 percent. During the first 20 hours of the test, average NOx conversion 

dropped below 90 percent several times while the control system was being tuned and 

refined. After fine-tuning the control system, NOx conversion remained between 90 

percent and 94 percent with the cumulative time weighted average NOx conversion 

increasing with time after the first 20 hours. The manufacturer discovered that the actual 

capacity of the full-scale LNTs was significantly less than predicted, based on the subscale LNT test results. The LNT vendor suggested that the capacity difference was due 

to their prototype production process depositing a non-uniform washcoat loading on the 

full-scale traps. The vendor explained that this performance shortfall would not be 

expected from commercially manufactured traps. The NOx trapping capacity shortfall 

resulted in the inability of the prototype hardware to maintain 90 percent NOx reduction 

for an extended period of time. As a result, a fourth trap had to be added to the system to 

meet the performance objectives of the 100-hour test. 

The next phase of the project, Phase II development and field trials, will include: 

• Integrating the LNT system with an ARB-certified diesel particulate filter and 

produce two integrated units for field trials with design goals of 95 percent NOx 
13

and 85 percent diesel particulate matter (PM) removal at minimal fuel penalty. 

One unit will be sized for a 500 kW engine and the second for a 1,000 kW engine. 

• Installing these two units on existing diesel engines at two different locations and 

operated for 1,000 hours each under normal operating conditions. 

At the conclusion of Phase II field demonstration, the results will be analyzed and 

a decision will be made as to whether to proceed with Phase III, where this NOx control 

technology will be made available to the general public on a limited release basis while 

the pilot manufacturing details are worked out and preparations are made for a full 

commercial release. More information on this project is available at: 

http://www.energy.ca.gov/pier/final_project_reports/CEC-500-2005-129.html. 

2.13 Evaluation of NH3-SCR Catalyst Technology on a Stationary Diesel Genset 

 Three technology manufacturers and U.S. Navy, Naval Surface Warfare Center 

collaborated together to demonstrate “proof-of-concept” of ammonia-selective catalytic 

reduction (SCR) and diesel oxidation catalyst system on a 250 kW diesel genset. The 

SCR and DOC were installed on a Caterpillar 3306 diesel generator set engine, rated at 

1800 rpm, 250 kW. The catalyst system was a four bank system, each bank with two 5 

liter SCRs and one 2.5 liter DOC brick. The emissions testing for the system was 

conducted by a third party, GE Energy Management Services. During the field testing, 

the engine was maintained at 90 percent load, using U.S. #2 diesel fuel. Data was 

collected at different weather conditions by running the engine for 500 hours at 90 

percent load. Exhaust gas analysis (NO, NO2, CO, CO2, and O2) was conducted 

upstream and downstream of the catalytic converter. Secondary emissions of NH3, CO, 

VOCs, and PM were verified by the third party GE Management Services. Results from 

the emissions testing showed 70 to 80 percent conversion of NOx to N2 at 90 percent load 

and NH3/NOx of about 0.8. 

 More information on this project is available at: 

http://www1.eere.energy.gov/vehiclesandfuels/pdfs/deer_2005/poster2/2005_deer_malya

la.pdf. 

2.14 Additional SCR projects: 

 There have also been several projects involving installation of SCR systems on 

stationary, natural gas fired, reciprocating engines to comply with NOx regulations. For 

more information on these projects, go to: 

http://www.icac.com/i4a/pages/index.cfm?pageid=3356#Multi-p. 
14

3.0 Summary 

As shown by the above case studies, experiences with retrofitting stationary diesel 

engines with emission control devices are growing. These stationary engine case studies 

are another example of the successful transfer of diesel retrofit technology originally 

developed for reducing diesel particulate and/or NOx emissions from on-road diesel 

engines into off-road diesel engine applications. The availability of ultra-low sulfur 

diesel (ULSD) fuel for non-road diesel engines will expand significantly now that the 

national rollout of ULSD for highway applications has been completed. This should 

facilitate even wider application of retrofit filter technologies on stationary diesel engines. 

Areas of the country with severe ozone problems are also prime targets for EGR or SCR 

retrofits on stationary engines for reducing NOx emissions from these sources. The 

examples cited in this report provide firm evidence that retrofit technologies can be a 

successful, cost-effective strategy for reducing emissions from stationary diesel engines.