p.1 

OAR Box 1170 

Prepped by Ollie Stewart 

Document Number: 

54) ll-A-1 

Docket Number: 

A-88-23 

Printed 4/30/2008 10:49:05 AM Sheet 54 of 182 
P.2 

RADIAN /?-"-« 

CORPORATIO N 

01-/9-/ 

258-012-25-01

 ;/ 

DCN: 87-258-012-25-02 

FEASIBILITY AND COST-EFFECTIVENESS 

OF CONTROLLING-EMISSIONS FROM DIESEL ENGINES1, 

IN RAIL. MARINE, CONSTRUCTION, FARM/* 

AND OTHER MOBILE OFF-HIGHWAY EQUIPMENT 

Final Report Under 

EPA Contract No. 68-01-7288 

' Work Assignment 25 

Prepared for: 

Office of Policy Analysis 

. U.S. EPA, PM-221 

401 M Stree t S.W. 

Washington, D.C. 20460 

Prepared by: 

Christophe r S. Weaver, P.E, 

Radian Corporation 

10395 Old Placervill e Road 

Sacramento, CA 95827 

February 1988 

10395 Old Placerville Rd./Sacramento, California 95827/(916)362-5332 
P.3 

EXECUTIVE SUMMARY 

Diese l engines in off-highway vehicle s and othe r off-highway mobile 

equipment, while less numerous than those in highway trucks and buses, ar e 

stil l significant contributors to NO and particulat e inventories in many 

urban areas. These engines are presently exempt from any emissions control 

requirements. Consequently, they produce far more pollution (per unit of fuel 

input or work output) than the otherwise similar emission-controlled engines 

used in on-highway vehicles. The recent promulgation of stringent NO and 

particulat e emissions standards for diesel engines in on-highway vehicles has 

drawn attention to diesel emissions in general, and has raised the question of 

whether similar emissions standards might not be appropriate for off-highway 

diesel engines. 

Background 

Emissions from diesel engines used in on-highway trucks and buses 

have been regulated with increasing stringency since 1972. New Federal 

regulations adopted in 1985 will limit particulat e matter (PM) emissions from 

heavy-duty diesel engines to 0.6 grams per brake horsepower-hour (g/BHP-hr), 

beginning in the 19 88 model year. The NO emissions limit, currently at 10.7 

g/BHP-hr, will be reduced to 6.0 g/BHP-hr in 1990, and to 5.0 g/BHP-hr in 

1991. A new PM limit of 0.25 g/BHP-hr (0.1 g/BHP-hr for buses) is also 

scheduled for 1991, and a PM limit of 0.1 g/BHP-hr for al l vehicles is 

scheduled for 1994. 

Although they are technically very similar to on-highway diesel 

engines, engines used in off-highway mobile equipment such as locomotives, 

farm and construction equipment, boats, and similar applications are presently 

exempt from any emissions controls. The Clean Air Act gives EPA authority to 

regulate "stationary sources" of emissions, and "motor vehicles" , but the term 

"motor vehicle" has traditionally been interpreted to include on-highway 

vehicles only. Since off-highway mobile sources are neither "stationary" nor 
P.4 

"motor vehicles" , EPA appears to have no authority to regulate them. 

If regulations were considered desirable, Congressional action would be needed 

to provide the required authority. 

Scope of This Report 

Radian Corporation was commissioned by the U.S. EPA, Office of 

Policy Analysis to study the feasibility and cost-effectiveness of emissions 

controls in off-highway diesel vehicles. This document is the final report of 

that study. This report addresses the following major categories of 

diesel-engined off-highway equipment: 

• Railroad locomotives; 

• Marine vessels (except large oceangoing ships); 

• Farm equipment; 

• Construction and industrial equipment 

(including mining and forestry equipment); and 

• Mobile Refrigeration Units. 

These categories include the most significant classes of mobile 

diesel engines except for on-highway vehicles (which are already regulated) 

and oceangoing motorships. 

Results and Conclusions 

Based on the estimates developed for this report, tota l pollutant 

emissions from off-highway diesel engines are large both in absolute terms and 

in proportion to their tota l numbers, power output, and fuel consumption. 

Table E-1 summarizes the estimated population, annual fuel consumption, and 

emissions for the five classes of off-highway diesel engines considered in 

this report. Estimated pollutant emissions are reported both in tons per year 

and as a percentage of the estimated tota l emissions of that pollutant by al l 

sources nationwide. Off-highway diesel engines are estimated to produce about 

1 1 
TABLE E-1 . ESTIMATED NATIONWIDE POPULATION AND EMISSIONS FROM DIESEL ENGINES 

USED IN OFF-HIGHWAY APPLICATIONS 

Tota l Fue l 

No. of Horsepowe r Consumption 

Engine s (1,000s) (1,000 gal) HC 

Emission s (tons/yr ) 

CO NO 

Locomotive s 

Medium Speed 1 

Percen t of Nationwid e 

Marine Vessels 

High Speed 

Medium Speed 

Tota l 

Percen t of Nationwid e 

Farm Equipment 

26,10 5 

438.00 0 

5.000 

443.00 0 

61,11 1 

45,47 1 

11,17 3 

56.64 4 

High Speed 3.868.01 9 332.13 9 

Percen t of Nationwid e 

3.409.47 6 30.99 9 308.55 8 

0.13% 0.40% 

915.67 1 

917.607 

1.833.278 

14.65 1 54.48 2 

18.81 1 85.79 6 

33,46 2 140.278 

0.14% 0.18% 

3,021,56 1 108,603 274.669 

0.46% 0.36% 

199.61 6 

244,54 2 

444,15 8 

2.05% 

688.87 4 

3.17% 

PM 

901.64 5 37.04 1 

4.16% 0.48% 

10.98 8 

9.17 6 

20.16 4 

0.26% 

75.10 3 

0.97% 

i i 

Constructio n and Industria l Equipment 

High Speed 1,047.805 124,056 

Percen t of Nationwid e 

3.279.66 1 47.82 0 191.064 590.372 50,02 1 

0.20% 0.25% 2.72% 0.65% 

Mobil e Refrigeratio n 

High Speed 

Percent of Nationwide 

203,000 9,518 494.167 10.921 44.347 

0.05% 0.06% 

115,520 4.991 

0.53% 0.06% 

TOTALS 

High Speed 

Medium Speed 

Total 

Percen t of Nationwid e 

5.556,82 4 

31.10 5 

5.587.92 9 

511.18 4 

72.28 4 

583,46 8 

7,711,06 0 181,995 564.562 1.594.382 141.103 

4.327.08 3 49.81 0 394.35 4 1.146.187 46.21 7 

12.038.14 3 231.805 958.916 2.740.56 9 187.320 

0.98% 1.25% 12.63% 2.43% 

1

 Percen t of nationwid e emission s inventor y fo r tha t pollutan t based on EPA (1986) 
P.6 

2.75 million tons of NO per year, 187,000 tons of particulat e matter, 232,000 

tons of unburned HC, and 959,000 tons of CO. These values are about 12.6 

percent, 2.4 percent, one percent, and 1.25 percent, respectively, of 

estimated nationwide emissions of these pollutants from all sources (EPA, 

1986). 

More significant than the off-highway diesel contribution to the 

tota l emissions inventory is the off-highway contribution to the tota l for al l 

mobile diesel engines, both on and off-highway. Table E-2 shows this 

calculation. As this table indicates, off-highway diesel engines are 

responsible for a disproportionate fraction of the total : accounting for 56 

percent of the NO emissions, 57 percent of CO emissions, and 48 percent of HC 

emissions from mobile diesel engines, but only 41 percent of the diesel fuel 

burned. Their contribution to PM emissions is less than proportionate, 

however, at 36.5 percent of the total . Due to limited data, the numbers in 

Table E-2 are somewhat crude, but the conclusion is inescapable: off-highway 

diesel engines are currently an important source of emissions, comparable in 

magnitude to on-highway diesels. 

Diesel engines in on-highway vehicles have been subject to emission 

regulations for many years, and have recently received a great deal of 

regulatory attention, which will lead to stil l lower emissions in the future. 

Off-highway engines, since they do not fall under EPA's statutory authority, 

have not been regulated. For this reason, pollutant emissions per unit of 

work produced or fuel consumed by an average off-highway diesel are much 

higher than those for an on-highway engine, and the potential for future 

reductions in emissions is correspondingly greater. 

As described in greater detail in Sections Three through Eight of 

this report, emission control technology for on-highway diesel engines is well 

developed, and this technology could readily be transferred to most offhighway engines. Off-highway diesel engines can be divided into high-speed 

and medium-speed classes, having rated operating speeds above or below 1300 

iv 
P.7 

TABLE E-3 . 

-

Locomotives 

NO 

HC31 

PM 

Marine Vessels 

Medium-Speed Engine s 

NO 

HC3' 

PM 

High-Speed Engine s 

NO 

HC* 

PM 

Farm Equipment 

NO 

HC* 

PM 

Constructio n Equipment 

NO 

HC* 

PM 

Mobil e Refrigeratio n 

. NO 

HC* 

PM 

EMISSIONS STANDARDS ESTIMATED 

BY EACH CLASS OF OFF-HIGHWAY 

j 

Int e 

Standar d 

(g/BHP-hr) 

6.0 

0.5 0 

0.5 0 

6.0 

0.5 0 

0.5 0 

6.0 

0.5 0 

0.5 0 

8.0 

0.5 0 

0.5 0 

8.0 

0.5 0 

0.5 0 

6.0 

1.0 

0.5 0 

rmediat e 

Percen t 

Reductio n 

55% 

52% 

1% 

55% 

52% 

1% 

45% 

38% 

17% 

30% 

72% 

60% 

12% 

32% 

36% 

49% 

10% 

2% 

TO BE ACHIEVABLE 

DIESELS 

Advanced 

Standar d 

(g/BHP-hr) 

5 . 0 

0.3 0 

0.2 0 

5 . 0 

0.3 0 

0.2 0 

5 . 0 

0.5 0 

0.2 5 

6.0 

0.2 0 

0.1 5 

6 . 0 

0.2 0 

0.1 5 

5.0 

0.2 0 

0.1 0 

Technology 

Percen t 

Reductio n 

63% 

71% 

60% 

63% 

71% 

60% 

55% 

38% 

59% 

48% 

89% 

88% 

34% 

73% 

81% 

58% 

73% 

80% 

Source: Radian estimates 

vii 
P.8 

and farm equipment would also require a slightly higher NO limit than that 

x 

mandated for on-highway engines, due to the limited potential for 

low-temperature charge cooling. 

The reader is warned that the emissions limits shown in Table E-3 

are engineering estimates only, based on very limited data, and intended only 

to indicate the potential benefits of regulation in this area. As discussed 

below, additional research to confirm these estimates would be essential 

before these or any other emission standards were incorporated into law. 

Figures E-1 through E-3 show the potential effects of introducing 

the emissions standards listed in Table E-3 on NO , HC, and PM emissions from 

x 

each class of off-highway engines. The leftmost bar for each class represents 

the current situation, with no emissions control. The middle bar represents 

the emissions that would be experienced if al l existing engines met the 

"intermediate" emissions standards, and the rightmost bar the emissions that 

would result if al l existing engines met the "advanced technology" standards. 

The net reduction if every off-highway engine in use met the "advanced 

technology" standards would be about 1.4 million tons of NO , 162,000 tons of 

HC, and 146,000 tons of PM per year, or 52 percent, 70 percent, and 78 

percent, respectively, of the current emissions of these pollutants from 

off-highway diesels. In reality , of course this would take a very long time 

to achieve, due to the need to turn over the existing engine population. 

The cost-effectiveness of controlling off-highway diesel emissions 

to at least the intermediate-term standards shown is estimated to be very 

favorable compared to the costs of other available emission control measures 

of similar significance. Estimated cost-effectiveness values for a number of 

specific equipment types are shown in Table E-4. While based on crude 

preliminary cost estimates, these values are believed to somewhat conservative 

(in the sense of over-stating emissions control costs, and thus the costs per 

ton of pollutants eliminated). Despite this, the cost-effectiveness estimates 

for control of NO and HC range from a few hundred to about three thousand 

dollars per ton. 

vii i 
P.9 

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Locomotives 

Marine 

Vessels 

Farm Construction Mobile 

Equipment Equipment Refrigeration 

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Uncontrolled Int. Controls Adv. Controls 

Figure E-1. Estimated Effect of Emissions Controls 

on Total Off-Highway NO Emissions 

x 

ix 
P.10 

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^ 223 

Locomotives 

Marine 

Vessels 

Farm Construction Mobile 

Equipment Equipment Refrigeration 

\ZJm- SS ____\ 

Uncontrolled Int. Controls Adv. Controls 

Figure E-2. Estimated Effect of Emissions Controls 

on Total Off-Highway HC Emissions 
P.11 

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Locomotives 

Marine 

Vessels 

Farm Construction Mobile 

Equipment Equipment Refrigeration 

IZZ 

Uncontrolled 

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Int. Controls 

w& 

Adv. Controls 

Figure E-3. Estimated Effect of Emissions Controls 

on Total Off-Highway PM Emissions 

xi 
P.12 

TABLE E-4. ESTIMATED COST-EFFECTIVENESS OF "INTERMEDIATE LEVEL" 

EMISSIONS CONTROLS POR DIFFERENT CLASSES OF OFF-HIGHWAY 

VEHICLES 

Cost Effectiveness ($/ton) " 

NO + HC PM 

x 

Locomotives 

New 

Retrofit 

$1,073 

1.332 

2 

"2 

Marine Vessels 

Medium Speed 

High-Speed Propulsion 

High-Speed Generator 

Farm Equipment 

Large 4WD Tractor 

Small Tractor 

Combine 

672 

888 

616 

845 

2.960 

848 

2 

"2 

'2 

3,067 

7,607 

1,900 

Construction Equipment 

Hydraulic Excavator 

Industrial Tractor 

Concrete Paver 

748 

1.567 

2,045 

8.969 

5.323 

3,961 

Mobile Refrigerato r 

Railca r Unit 

Truck/Container Unit 

229 

1,909 

2 

"2 

Approximate estimate s based on engineering judgement and limited data . See 

tex t Chapters 4-8 for assumptions and limitations. 

2 

PM reduction s a t "intermediate " contro l leve l ar e estimated as small or 

negative for these categories. This is due t o low PM emissions t o begin with, 

and the effects of the NO /PM tradeoff. 

x n 
P.13 

For comparison, the fuel cost alone for reducing the 1991 NO 

x 

standard for heavy-duty cn-highway engines from 5.0 to 4.0 g/BHP-hr (a step 

which is often suggested) is estimated a t about $2,000 pe r ton (assuming a 4 

percent fuel economy penalty and fuel a t $0.80 per gallon excluding taxes). 

The incremental cost-effectiveness of the 1994 PM standard of 0.1 g/BHP-hr for 

heavy-duty on-highway engines has been estimated a t about seven t o eleven 

thousand dollars per ton (Weaver and Klausmeier, 1987a). 

Re c omme nda t io n s 

1. The development of more accurat e and representativ e duty 

cycles, emission factors, and emission inventorie s for 

off-highway diese l vehicle s would be highly desirable , as would 

the development of suitabl y representativ e emissions test 

procedures. These data and procedures would be valuabl e in 

developing and evaluating any future regulation s in this area . 

However, EPA funding of emissions control experimentation is 

not recommended beyond a very preliminary level . Experience 

has shown tha t this type of work is more appropriatel y left to 

the engine manufacturers. 

2. Were emissions regulation s t o be establishe d for farm and 

construction equipment engines, careful consideration should be 

given to phase-in mechanisms in order t o avoid undue burden on 

the industry . An averaging, trading , and banking approach with 

"crawling" targe t levels, such as tha t discussed in Section 

6.5 , would be one fairl y straightforwar d way t o do this. 

3 . In the event tha t emissions regulation s ar e establishe d for new 

medium-speed marine and locomotive engines, consideration 

should als o be given t o establishin g retrofi t requirements for 

olde r engines in these categories. These requirements could 

most conveniently apply a t the time of rebuild . 

xii i 
P.M 

Limitations and Caveats 

This report presents the results of a preliminary investigation of 

controlling emissions from off-highway diesel vehicles. The principal purpose 

of this investigation was to determine whether these vehicles offer sufficient 

potential for technically feasible and cost-effective emission reductions to 

justify further attention from EPA. The study results indicate that regulation 

of off-highway emissions could potentially result in large, cost-effective 

emission reductions. Thus, further investigation and possible regulatory 

action are indicated. However, this investigation does not conclusively 

demonstrate, and should not be interpreted as demonstrating that the 

levels of emissions control assumed here are technically feasible, or 

achievable within any particular time frame, or at any particula r cost. Many 

issues remain to be resolved before any realisti c emissions standards or 

compliance schedules could be established. 

xiv 
P.15 

TABLE OF CONTENTS 

Section Page 

EXECUTIVE SUMMARY i 

LIST OF TABLES xvii i 

LIST OF FIGURES xxi 

1. 0 INTRODUCTION 1-1 

1.1 Background 1-1 

1.2 Nature and Scope of this Report 1-2 

1.3 Guide to the Remainder of the Report... . 1-4 

1.4 Limitation s and Caveats 1-5 

2.0 DIESEL ENGINE CHARACTERISTICS AND CLASSIFICATION 2-1 

2.1 Engine Classificatio n 2-1 

2.2 Engine Technology 2-5 

2.3 Diese l Emission Fundamentals 2-10 

2.4 Emission Regulations 2-14 

3.0 TECHNOLOGY FOR EMISSION CONTROL 3-1 

3.1 High-Speed Engines 3-1 

3 . 2 Medium-Speed Engines 3-9 

4.0 LOCOMOTIVES 4-1 

4.1 Engine Characteristic s and Operating Conditions 4-1 

4.2 Current Emission Factors 4-3 

4.3 Engine Population and Emissions Inventory 4-8 

4.4 Emissions Test Cycle 4-10 

4.5 Feasibilit y of Emissions Control 4-11 

4.6 Cost-Effectiveness Analysis 4-14 

xv 
P.16 

>«anii«> i p IJ i 

TABLE OF CONTENTS (Continued) 

Section Page 

5.0 MARINE VESSELS 5-1 

5.1 Engine Characteristic s and Operating Conditions 5-1 

5 . 2 Current Emis sion Fact ors 5-3 

5.3 Engine Population and Emissions Inventory 5-6 

5.4 Emissions Test Cycle 5-9 

5.5 Feasibilit y of Emissions Control 5-10 

5.6 Cost-Effectiveness Analysis 5-13 

6.0 FARM EQUIPMENT 6-1 

6.1 Engine Characteristic s and Operating Conditions 6-1 

6.2 Current Emission Factors 6-2 

6.3 Engine Population and Emissions Inventory 6-5 

6.4 Emissions Test Cycles 6-7 

6.5 Feasibilit y of Emissions Control 6-8 

6.6 Cost-Effectiveness Analysis 6-12 

7.0 CONSTRUCTION AND INDUSTRIAL EQUIPMENT 7-1 

7.1 Engine Characteristic s and Operating Conditions 7-1 

7.2 Current Emission Factors 7-2 

7.3 Engine Population and Emissions Inventory 7-4 

7.4 Emis sions Tes t Cycles 7-7 

7.5 Feasibilit y of Emissions Control 7-8 

7.6 Cost-Effectiveness Analysis 7-10 

xvi 
P.17 

LIST OF TABLES 

Table Page 

E-1 Estimated Nationwide Population and Emissions from 

Diese l Engines Used in Off-Highway Applications E-3 

E-2 Comparison of Nationwide Fuel Consumption and 

Emissions Off-Highway VS. On-Highway Diesels E-5 

E-3 Emissions Standards Estimated t o be Achievable by 

Each Class of Off-Highway Diesels E-7 

E-4 Estimated Cost-Effectiveness of "Intermediat e Level " 

Emissions Controls for Different Classes of Off-Highway 

Vehicles E-12 

1-1 Deliverie s of Diese l Fuel for On- and Off-Highway 

Vehicles and Equipment 1-3 

2-1 Characteristic s of Some Common Off-Highway Engine 

Serie s 2-3 

2-2 Federal and Californi a Emissions Regulations for 

Heavy-Duty Diese l Engines 2-15 

3-1 Techniques for Diese l Engine Emissions Control 3-3 

3-2 Effect of Engine Modifications on GM Electro-Motive 

Division (EMD) 16V-64E Engine Performance and Emissions.. . 3-11 

4-1 Measured Locomotive Emissions from Published Studies 

Expressed in Grams Per Horsepower Hour on Line Haul 

Cycles 4-4 

4-2 Emission Factors for Railway Locomotives 4-5 

4-3 Population, Fuel Consumption, and Estimated Emissions 

for Railway Locomotives 4-9 

4-4 Estimated Achievable Emissions Control Standards for 

Locomotive Engines 4-13 

4-5 Estimated Cost-Effectiveness of Emissions Control for 

New Railway Locomotives 4-15 

5-1 Estimated Current Emission Factors for Diesel Engines 

Used in Marine Applications 5-5 

xviii 
P.18 

TABLE OF CONTENTS (Continued) 

Section " Page 

8.0 MOBILE REFRIGERATION UNITS 8-1 

8.1 Engine Characteristic s and Operating Conditions 8-1 

8.2 Current Emission Factors 8-2 

8.3 Engine Population and Emissions Inventory 8-4 

8.4 Emissions Test Cycles 8-4 

8.5 Feasibilit y of Emissions Control 8-6 

8.6 Cost-Effectiveness Analysis 8-6 

9.0 SUMMARY, CONCLUSIONS AND RECOMMENDATIONS 9-1 

9.1 Summary and Conclusions....' 9-1 

9.2 Recommendations 9-10 

10.0 REFERENCES 10-1 

APPENDIX A: DERIVATION OF LOCOMOTIVE EMISSION FACTORS 

xvi i 
P.19 

1 

LIST OF TABLES (Continued) 

Table Page 

8-4 Estimated Cost-Effectiveness of Emissions Control 

for Diese l Engines Used in Mobile Refrigeration 8-8 

9-1 Estimated Nationwide Population and Emissions from 

Diese l Engines Used In Off-Highway Applications 9-2 

9-2 Comparison of Nationwide Fuel Consumption and Emissions 

Off-Highway Vs. On-Highway Diesels 9-3 

9-3 Emissions Standards Estimated t o be Achievable by Each 

Class of Of f-Highway Diesels 9-5 

9-4 Estimated Cost-Effectiveness of "Intermediat e Level " 

Emissions Controls for Different Classes of Off-Highway 

Vehicles 9-11 

xx 
P.20 

••M f Iff * Mill 

LIST OF TABLES (Continued) 

Table Page 

5-2 Estimated Nationwide Population and Emissions from 

Diese l Engines Uised in Marine Applications 5-7 

5-3 Estimated Achievable Emissions Control Standards for 

Marine Diese l Eragin<es 5-11 

5-4 Estimated Cost-Effectiveness of Emissions Control for 

Diese l Engines Used in Marine Applications 5-14 

6-1 Emission Factors for Farm Equipment 6-4 

6-2 Estimated Population, Fuel Consumption, and Emissions 

from Diese l Engines Useid in Farm Equipment 6-6 

6-3 Estimated Achievable Emissions Control Standards for 

Diese l Engines Used in Farm Equipment 6-10 

6-4 Estimated Cost-Effectiveness of Emissions Control for 

Diese l Engines Used in Farm Equipment 6-13 

7-1 Estimated Current Emission Factors for Diesel Engines 

Used in Construction and Industria l Equipment 7-3 

7-2 Estimated Population, Fuel Consumption and Emissions 

from Diese l Engines Used on Construction and Industria l 

Equipment 7-5 

7-3 Estimated Achievable Emissions Control Standards for 

Diesel Engines Used in Construction and Industrial 

Equipme nt 7-11 

7-4 Estimated Cost-Effectiveness of Emissions Control for 

Diese l Engines Used in Construction Equipment 7-13 

8-1 Estimated Current Emission Factors for Diesel Engines 

Used for Mobile Re frige ratio n 8-3 

8-2 Estimated Nationwide Population, Fuel Consumption, and 

Emissions from Diese l Engines Used for Mobile 

Refrigeration 8-5 

8-3 Estimated Achievable Emissions Control Standards for 

Diese l Engines Used in Mobile Refrigeration 8-7 

xix 
LIST OF FIGURES 

Figure Page 

E-1 Effect of Emissions Controls on Total Off-Highway 

NO Emissions E-9 

x 

E-2 Effect of Emissions Controls on Tota l Off-Highway 

HC Emissions E-10 

E-3 Effect of Emissions Controls on Total Off-Highway 

PM Emissions E-l l 

2-1 Diese l Engine Combustion Systems 2-6 

9-1 Effect of Emissions Controls on Total Off-Highway 

NO Emissions 9-7 

x 

9-2 Effect of Emissions Controls on Total Off-Highway 

HC Emis sions 9-8" 

9-3 Effect of Emissions Controls on Tota l Off-Highway 

PM Emis sions 9-9 

xx 1 
P.22 

1.0 INTRODUCTION 

Diesel engines in off-highway vehicle s and othe r off-highway mobile 

equipment, while less numerous than those in highway trucks and buses, ar e 

stil l significan t contributors t o "NO and particulat e inventorie s in many urban 

areas. These engines ar e presentl y exempt from any emissions control require -

ments. Consequently, they produce fa r more pollutio n (per unit of fuel input 

or work output) than the otherwise simila r emission-controlled engines used in 

on-highway vehicles. The recent promulgation of stringen t NO and particulat e 

emissions standards for diese l engines in on-highway vehicle s has drawn atten -

tio n t o diese l emissions in general, and has raised the question of whether 

simila r emissions standards might not be appropriat e for off-highway diese l 

engines. 

1.1 Background 

Emissions from diese l engines used in on-highway trucks and buses 

have been regulated with increasin g stringency since 1972. New Federal regula -

tion s adopted in 1985 wil l limit particulat e matter (PM) emissions from 

heavy-duty diese l engines to 0.6 grams per brake horsepower-hour (g/BHP-hr), 

beginning in the 1988 model year. The NO emissions limit , currentl y a t 10.7 

g/BHP-hr, wil l be reduced t o 6.0 g/BHP-hr in 1990, and to 5.0 g/BHP-hr in 1991. 

A new PM limit of 0.25 g/BHP-hr (0.1 g/BHP-hr for buses) is als o scheduled for 

1991, and a-PM limit of 0.1 g/BHP-hr for al l vehicle s is scheduled for 1994. 

Although they ar e technicall y very simila r to on-highway diese l 

engines, engines used in off-highway mobile equipment such as locomotives, farm 

and construction equipment, boats, and simila r application s ar e presently 

exempt from any emissions standards. The Clean Air Act gives EPA authorit y to 

regulat e "stationar y sources " of emissions, and "motor vehicles" , but EPA 

interprets the term "motor vehicle " to include on-highway vehicle s only. Since 

off-highway mobile sources ar e neithe r "stationary " nor "motor vehicles" , EPA 

1-1 
considers that i t has no authority to regulate them. EPA does have authority 

to regulate emissions from stationary internal-combustion engines used for 

cogeneration, emergency generators, irrigation pumping, and so forth, but New 

Source Performance Standards (NSPS) for these engines have not been? 

promulgated. 

1.2 Nature and Scope of This Report 

Radian Corporation was commissioned by the U.S. EPA, Office of Policy 

Analysis to study the feasibility and cost-effectiveness of emissions controls 

in off-highway diesel vehicles. This document is the final report of that 

study. This report addresses the following major categories of diesel-engined 

off-highway equipment: 

• Railroad locomotives; 

• Marine vessels (except large oceangoing ships); 

• Farm equipment; 

• Construction and industrial equipment 

(including mining and forestry equipment); and 

• Mobile refrigeration units. 

These categories include al l large groups of mobile diesel engines 

except for on-highway vehicles (which are already regulated) and oceangoing 

motorships. Engines used for generators, pumps, and compressors and diesel 

lawn and garden equipment were also included in the original scope of the 

study, and these (along with al l the categories listed above) were examined in 

a preliminary report (Weaver and Pugh, 1986). They were subsequently dropped, 

due to their insignificant contribution to tota l emissions. 

Table 1-1 gives an idea of the relative importance of on-highway and 

off-highway diesel engines. This table lists U.S. Department of Energy 

estimates of the amount of distillat e diesel fuel consumed by each equipment 

1-2 
TABLE 1-1 . DELIVERIES OF DIESEL FUEL FOR ON- AND 

OFF-HIGHWAY VEHICLES AND EQUIPMENT 

Class 

Annual Deliveries 

1000s of Gallons 

Farm 

Locomotive 

Marine Vessels 

Construction and 

Other Off-Highway 

Off-Highway Tota l 

On-Highway Total 

Tota l Mobile Diese l Engines 

Off-Highway as Percent of Total 

3,161,338 

3,209.729 

1.894,265 

1,616,685 

9,882.017 

17.279,650 

27,161,667 

36.4% 

Source: EIA, 1985, 

1-3 
P.25 

category in 1985. As this table indicates, each of the individual categories 

< f off-highway mobile sources considered in this report is small compared to 

on-highway vehicles (trucks, buses, and diesel passenger cars). Collectively, 

however, these sources are quite significant. As can be seen, tota l 

off-highway diesel fuel consumption is equal to 57 percent of the on-highway 

total . Furthermore, some of the fuel used in the on-highway category is used 

for powering mobile refrigeration units. Emissions from these units are 

unregulated, and they are covered in this report. It is apparent that 

off-highway and other unregulated diesel emissions sources must account for a 

very significant fraction of tota l diesel engine emissions in the United 

States. 

1.3 Guide to the Remainder of the Report 

This report is divided into nine sections, of which this Introduction 

is the first . Section Two, following, provides the technical background for 

the succeeding sections. It discusses the classification and general characteristic s of off-highway diesel engines, and the fundamentals of diesel 

emissions. Section Three discusses the current stat e of the art in diesel 

emissions control, based largely on on-highway engine results. Sections Four 

through Eight each deal with one of the equipment categories listed in Section 

1.2 above. Engine characteristic s and operating conditions, estimates of 

current emission factors, and a discussion of applicable emission control 

technology are given for each category. Estimates of the tota l engine population, fuel use, and nationwide pollutant emissions for each category are also 

presented in each section. 

Following the five sections dealing with individual engine 

categories, Section Nine summarizes the results of the study and our 

conclusions. This section also contains our recommendations for further 

research, and for policy action. 

1-4 
1.4 Limitations and Caveats 

This report presents the results of a preliminary investigation of 

controlling emissions from off-highway diesel vehicles. The principal purpose 

of this investigation was to determine whether these vehicles offer sufficient 

potential for technically feasible and cost-effective emission reductions to 

justify further attention from EPA. The study results indicate that regulation 

of off-highway emissions could potentially result in large, cost-effective 

emission reductions. However, this investigation does not demonstrate, and 

should not be interpreted as demonstrating that any particular level of 

emissions control is technically feasible, or achievable within any particular 

time frame, or at any particular cost. 

While this report presents some approximate estimates of the emission 

levels achievable, and the costs of achieving them, the reader is cautioned not 

to misinterpret these. These are preliminary estimates only, made for the 

purpose of assessing what might be achieved through regulations—they are not 

definitive. Many issues remain to be resolved before any realistic emissions 

standards could be specified. These issues include: representative test 

cycles for the different off-highway applications; emissions levels from 

existing engines using these representative test cycles; effects of available 

emission control techniques on emissions''measured over these test cycles; 

actual costs of vehicle redesign to accommodate emission controls; feasibility 

of some emission control techniques in some applications; and the potential for 

emissions compliance through use of alternative fuels such as methanol and 

compressed natural gas. Further research and much more detailed evaluation of 

each of these issues would be required before any regulations could be adopted. 

1-5 
2.0 DIESEL ENGINE CHARACTERISTICS AND CLASSIFICATION 

This section provides an overview of diesel engine characteristics 

and technology, diesel pollutant emissions, and emission regulations. It is 

intended to supply background information for those previously unfamiliar with 

diesel engines and emissions control, and to establish definitions for the more 

technical chapters which follow. 

2.1 Engine Classification 

Diesel engines are conventionally divided into three major classes on 

the basis of size and rotational speed (Lilly, 1984). These classes are : 

1. Slow-speed engines (0-600 RPM) 

2. Medium-speed engines (600-1300 RPM) 

3. High-speed engines (1300 RPM up) 

Slow-speed engines are used only in large ships (where they are 

typically direct-coupled to the propeller driveshaft), and in a very few 

stationary applications. They will not be considered further in this report. 

Medium-speed engines are used in railway locomotives, ships and large boats, as 

well as stationary generating and pumping applications. High-speed engines are 

by far the most numerous class, being used in highway trucks and buses, construction machinery, boats, farm equipment, and numerous other applications. 

Due to the economics of mass production, diesel engines used in 

mobile off-highway applications are typically members of a family or series of 

engines sharing the same basic cylinder dimensions, but with varying types of 

aspiration (naturally aspirated, turbocharged, or turbocharged/aftercooled) and 

numbers of cylinders. Thus, a wide range of power requirements can be 

satisfied using the same basic combustion system. As an extreme example, the 

2-1 
P.28 

venerable Detroit Diesel-Allison 71 series engines are available in roots blown 

and turbocharged versions, with air-air or air-water aftercooling, and with 2, 

3, 4, 6, 8, 12. or 16 cylinders. 

Table 2-1 lists a number of the more popular engine series, along 

with some of their key technical characteristics. These characteristics are 

discussed in Section 2.2. 

As Table 2-1 indicates, off-highway diesel engines can be grouped 

into several general groups. 

1. Medium-speed engines used in railway locomotives and marine 

vessels. 

2. Medium-sized, high-speed engines similar to those used in 

heavy-duty trucks. This is the largest group of off-highway 

diesel engines. Four, six, and eight-cylinder engines in this 

class are commonly used in agricultural and construction machinery and (in emission-controlled versions) for highway trucks. 

Larger 12 and 16-cylinder engines in the same series are used in 

marine and heavy construction applications. 

3. Large high-speed engines, having sizes and power levels greater 

than those used in on-highway truck applications. Turbocharged 

and often intercooled, these engines are used mostly in marine 

and heavy earthmoving applications. 

4. Small high-speed engines (often derived from light-duty automotive technology), and typically ranging from 10 to about 30 

horsepower. These engines are mostly naturally-aspirated, and 

may use eithe r direct or indirect injection. 

2-2 
P.29 

TABLE 2-1 . CHARACTERISTICS OF SOME COMMON OFF-HIGHWAY ENGINE SERIES 

Engin e Disp . 

Serie s (1/cyl ) 

Class 1 : Med 

Bore 

(in. ) 

ium-Speed 

GM Electromotiv e Divisio n 

567 9. 3 8.5 

645 10. 6 9. 1 

710 11. 7 9. 1 

Genera l Electri c 

FDL 

Caterpilla r 

3600 18.5 

Class 2 : High-Speed , 

Caterpilla r 

3200 

3300 

3400 

Cummins 

NH 

LIO 

B 

C 

GM Detroi t D 

92 

71 

John Deer e 

300 

400 

Class Three : 

Caterpilla r 

3500 

300 

1.31 

1.75 

2.4 4 

2.3 3 

1.67 

0.9 8 

1.38 

11. 0 

Truck 

4 . 5 

4 . 8 

5 . 4 

5 . 5 

4 . 9 

4 . 0 

4 .5 

iesel-Allisio n 

1.51 

1.17 4.25 

0.9 8 4.1 9 

1.27 4.5 6 

Asp . 

Types 

B.TA 

B.TA 

TA 

N.TA 

TA 

Type 

N.T.TA 

N.T.TA 

T.TA 

T.TA 

T.TA 

N.T.TA 

N.T.TA 

Divisio n 

B.T.TA 

B.T.TA 

N.T 

N.T.TA 

Larg e High-Speed Engine s 

4.3 1 

4.0 3 

6 . 7 

6 . 3 

TA 

TA 

I n j . 

System 

UI 

UI 

UI 

UI 

UI 

IL 

IL 

IL 

UI 

UI 

IL 

IL 

UI 

UI 

DP 

DP 

UI 

IDI 

V8 

V8 

6L 

Config . 

Offere d 

V8.V12.V16 

V12.V16.V20 

V12.V16.V20 

V8.V12.V16 

.8L.V12.V16 

4L.V8 

4L.6L 

6L.V8.V12 

6L.V12 

6L 

3L.4L.6L 

6L 

V6,V8,V12,V16 

2L,3L,4L,6L, 

V6.V8.V12.V16 

3L.4L.6L 

6L 

V8.V12.V16 

V8.V12.V16 

Horsepower 

Range 

600-275 0 

800-3900 

1800-4800 

1800-3600 

1300-4500 

71-355 

85-335 

215-838 

250-900 

25 0-290 

66-177 

15 0-234 

270-960 

64-760 

56-14 2 

134-226 

600-2000 

500-100 0 

Applicatio n 

R.B.G 

R.B,G,C 

R.B.G 

R 

R,B,G 

T.C.A 

T.C,A.G 

T.C.A.G.B 

T.A.C.B.G 

T.A.C.G' 

T.A.C 

T.A.C 

T.A.C.B.G 

T.A.C.B.G 

C.A.(T) 1 

C.A, (TM 

C.B.G 

C.B.G 

(Continued) 

2-3 
P.30 

TABLE 2-1. (Continued) 

Engine Disp. Bore Asp. Inj. 

Series (1/cyl) (in.) Types System 

Config. Horsepower Application 

Offered Range 

Cummins 

K 3.14 6.25 T.TA 

GM Detroit Diesel-Alliso n Division 

149 2.45 5.75 B.T.TA 

Class Four: Small High-Speed Engines 

UI 6L,12V,16V 450-2000 C.B.G 

UI 8V,12V,16V 530-1800 

Kubot a 

3.23 " St. 

Yanmar 

TN82 

T95 

.37-.4 6 

0.4 6 

0.7 8 

variou s 

3.2 3 

3.7 4 

N.T 

N.T 

N.T 

DP 

DP 

DP 

3L.4L.6L 

3L.4L 

3L.4L 

19-46 

30-47 

44-77 

A.C.L 

A.C.L 

A.C.L 

Aspiratio n 

N - naturall y aspirate d 

B - Roots-blown 

T - turbocharged 

TA - turbocharged/aftercooled 

Combustion System 

UI — DI w unit injectors 

IL — DI w in-lin e pump 

DP — DI w distributo r pump 

IDI - indirec t injectio n 

Applications 

T - On-highway truck s 

A - Agricultura l Equipment 

C - Construction/Mining/ 

Industria l equipment 

B - Boats 

L - Locomotive 

G - Generators/stationar y power 

Rf - Mobile refrigeratio n 

Truck version s of thes e engines ar e under development. 

2-4 
P.31 

This grouping has important implications for emissions control. 

Engine serie s in Group 2, for instance , typicall y have a t least one member used 

in on-highway trucks. As wil l be discussed in Section 3.1 , emission control 

development for on-highway engines is already highly advanced. Transferring 

this technology t o the off-highway engines in the same serie s would, in most 

cases, be straightforward . Similarly, engine technology in Group 3 resembles 

(except for th e large r number of cylinders) tha t used in the heaviest on-highway trucks. The small high-speed engines in Group 4 resemble, in many cases, 

those used or being developed for light-dut y automobiles, and could presumably 

utiliz e simila r emission controls. Group 1 engines, on the othe r hand, have 

never been subject t o stringen t emission control requirements, and have no. 

clos e analogs which have been. Development of emission controls for- this group 

is likel y t o be more time-consuming and expensive than for the othe r groups. 

2.2 Engine Technology 

From an emissions control standpoint, the key technica l feature s of a 

diese l engine ar e the following: 

• combustion system; 

• fuel injectio n system; and 

• aspiratio n (air supply) system. 

This sectio n discusse s the differen t types of systems in use . 

Combustion Systems—Diesel engines in off-highway application s use 

severa l differen t types of combustion systems. The most fundamental differenc e 

is between direc t injectio n (DI) engines and indirec t injectio n (IDI) engines. 

Figure 2-1 shows a typica l combustion chamber of each type . DI engines can 

als o be divided int o high-swirl and low-swirl (quiescent chamber) designs. 

In an indirect-injectio n engine, fuel is injected into a separat e 

"prechamber," where i t mixes and partl y burns before jettin g int o the main 

2-5 
P.32 

•p II WPP T'W^f ' 

(a) Indirect injection 

(b) Direct injection 

Figure 2-1. Diesel Engine Combustion Systems. 

2-6 
RADIAff 

combustion chamber above the piston. In the more common direct-injection 

engine, fuel is injected directly into a combustion chamber hollowed out of the 

top of the piston. Fuel-air mixing in the direct-injection engine is limited 

by the fuel injection pressure and any motion imparted to the air in the 

chamber as it entered. 

In high-swirl DI engines, a strong swirling motion is imparted to the 

air entering the combustion chamber by the design of the intake port. These 

engines typically use moderate-to-high injection pressures, and three to five 

spray holes per nozzle. Low swirl engines rely primarily on the fuel injection 

process to supply the mixing. They typically have very high fuel injection 

pressures and six to nine spray holes per nozzle. 

In the indirect-injection engine, much of the fuel-air mixing is due 

to the air swirl induced in the prechamber as air is forced into it during 

compression, and to the turbulence induced by the expansion out of the prechamber during combustion. These engines typically have better high-speed 

performance than direct-injected engines, and can use cheaper fuel-injection 

systems. Historically, IDI diesel engines have also exhibited lower emission 

levels than DI engines. With recent developments in DI engine emission controls, however, this is no longer necessarily the case. 

Disadvantages of the IDI engine are the extra heat and frictional 

losses due to the prechamber. These result in a 5-10 percent reduction in fuel 

efficiency compared to a DI engine, and a correspondingly greater load on the 

cooling system. Because of these disadvantages, nearly all engines in Groups 

1,2, and 3, now use direct injection, as do an increasing number of those in 

Group 4. 

Fuel Injection Systems—The fuel injection system in a diesel engine 

includes the machinery by which the fuel is transferred from the fuel tank to 

the engine, then injected into the cylinders at the right time for optimal 

combustion, and in the correct amount to provide the desired power output. The 

2-7 
P.34 

quality and timing of fuel injection dramatically affect the engine's power, 

fuel economy, and emissions characteristics, so that the fuel injection system 

is one of the most important components of the engine. 

The fuel injection system normally consists of a low pressure pump to 

transfer fuel from the tank to the system, one or more high-pressure fuel pumps 

to create the pressure pulses that actually send the fuel into the cylinder, 

the injection nozzles through which fuel is injected into the cylinder, and a 

governor and fuel metering system. These determine how much fuel is to be 

injected on each stroke, and thus the power output of the engine. 

Three generic types of fuel injection systems are in common use. 

These are : 

1. Systems with distributor-type fuel pumps, in which a single 

pumping element is mechanically switched to connect to highpressure fuel lines leading to each cylinder in turn; 

2. Systems with unitary fuel pumps having one pumping element per 

cylinder, connected to the injection nozzle by high-pressure 

fuel lines (often called "in-line pumps"); and 

3. Systems using unit injectors, in which the individual pumping 

element for each cylinder is combined in the same unit with the 

injection nozzle, eliminating the high-pressure lines. 

Distributor pumps are relatively inexpensive, but they are limited in 

the injection pressures they can achieve. For this reason, they are used 

mostly in indirect-injection engines. In-line pumps are capable of much higher 

injection pressures, and are used in many Group 2 engines, especially those 

produced by European and Japanese manufacturers. Unit injector systems are 

capable of the highest injection pressures (exceeding 25,000 PSI). These are 

used in al l Group 1 and Group 3 engines, and in an increasing proportion of 

2-8 
Group 2 engines as well. The larger Cummins engines, most Detroit DieselAllison (DDA) engines, and several recently-introduced Caterpillar engines use 

unit injectors. 

Distributor and in-line injection pumps are typically driven by a 

special driveshaft from the engine timing gears. This allows the injection 

timing to be varied by rotating the pump with respect to its driveshaft, using 

a sliding helical spline. The pumping elements in unit injector systems are 

driven by the engine camshaft, in the same way as the intake and exhaust 

valves. Until recently, injection timing in unit injector systems was fixed by 

the system geometry (except for the effects of wear). With the addition of 

electronic controls, however, these systems can provide very flexible control 

of injection timing, as discussed in Section 3.1 . 

Aspiration Systems—The aspiration system is the system by which 

combustion air is provided to the engine. The first four-stroke diesel engines 

relied on the suction created by the intake stroke to draw air into the cylinder. This approach is known as natural aspiration, and it is stil l used on 

many smaller and lower-powered engines today. Since the pressure forcing the 

a ir into the cylinder is limited to that of the atmosphere, the air available 

for combustion (and thus the maximum power output) from these engines is 

limited. 

In the early two-stroke engines, alseparate Roots-type blower, driven 

from the crankshaft, provided combustion air at pressures slightly over atmospheric. This technique, again, is stil l used in many smaller and 

lower-powered two-stroke engines today. Roots-blown two-stroke engines, like 

four-cycle naturally-aspirated engines, are limited in their power output by 

the atmospheric pressure. Although not strictl y accurate, i t is common to lump 

these engines together with four-stroke engines as "naturally aspirated", a 

practice which will be followed here. 

To obtain higher power output from a given engine size and displacement, manufacturers have adopted turbochargers. A turbocharger consists of a 

2-9 
., ip . ninw f if mm 9 y« 

RADIAN 

high-speed centrifugal compressor for the intake air, on the same shaft as and 

driven by a high-speed turbine in the exhaust. By compressing the intake air, 

the turbocharger increases the amount available in the cylinder, and thus the 

maximum power output. 

Compressing the intake air increases its temperature, increasing the 

thermal loading on pistons and other components. Cooling the compressed air in 

a heat exchanger or aftercooler reduces the thermal load, and decreases the air 

volume, further increasing the air mass available in the cylinder and thus the 

maximum power output. Most high-powered diesel engines now incorporate turbocharging and aftercooling. For most such engines, the heat sink for the 

aftercooler is the engine cooling water, at a temperature of 80-95 C. The need 

for lower intake air temperatures in emission-controlled and high-output 

engines has resulted in increasing use of low-temperature aftercooling, using 

eithe r air-to-air or air-to-low-temperature-liquid heat exchangers. These 

developments are discussed further in Section 3.1 . 

2.3 Diesel Emission Fundamentals 

Diesel engines emit significant quantities of oxides of nitrogen 

(NO ), sulfur oxides (SO ), particulat e matter (PM), and unburned hydrocarbons 

(HC). The NO , HC, and most of the PM emissions from diesels are formed during 

the combustion process, and can be controlled by appropriate modifications to 

that process. The sulfur oxides, in contrast, are derived directly from sulfur 

in the fuel, and the only feasible control technology is to reduce fuel sulfur 

content. Most SO is emitted as gaseous S0„, but a small fraction (typically 

2-3 percent) occurs as particulate sulfates. 

Diesel particulat e matter consists mostly of three components: soot 

formed during combustion, heavy hydrocarbons condensed or adsorbed on the soot, 

and particulat e sulfates. In older-technology diesels, soot is typically 40 to 

80 percent of the tota l particulate mass. Developments in in-cylinder 

2-10 
emissions control for on-highway engines have reduced the soot contribution to 

particulat e emissions considerably, however. Most of the remaining particulate 

mass consists of heavy hydrocarbons adsorbed or condensed on the soot. This is 

referred to as the soluble organic fraction of the particulat e matter, or SOF. 

The SOF is derived partly from the lubricating oil , partly from unburned fuel, 

and partly from compounds formed during combustion. 

The particulate SOF and gaseous hydrocarbons from diesel engines 

include many known or suspected carcinogens and other toxic air contaminants. 

These include polynuclear aromatic compounds (PNA) and nitroaromatics, formaldehyde and other oxygenated hydrocarbons. These last are also responsible 

for much of the characteristi c diesel odor. 

N—O /Particulat e Tradeoff—Diesel particulat e and NO emissions result 

x

 r

 x 

from the fundamental nature of the combustion process, making them especially 

difficult to control. As opposed to spark-ignition engines (which use a 

more-or-less homogeneous charge) all diesel engines rely on heterogeneous 

combustion. During the compression stroke, a diesel engine compresses only 

air. Fuel is injected into the combustion chamber in liquid form near the top 

of the compression stroke. The quantity of fuel injected with each stroke is 

determined by the engine power output required. After a brief period known as 

the ignition delay, the fuel is ignited by the hot air and burns. In the 

premixed burning phase, the fuel/air mixture formed during the ignition delay 

period burns rapidly. The subsequent rate of burning is controlled by the rate 

of mixing between the remaining fuel and air, with combustion always occurring 

a t the interface between the two. Most of the fuel burned is burned in this 

diffusion burning stage, except under very light loads. 

The fact that fuel and air must mix before burning means that a 

substantial amount of excess air is needed to ensure complete combustion of the 

fuel within the limited time allowed by the power stroke. Diesel engines, 

therefore, operate at overall air-fuel ratios which are considerably lean of 

2-11 
P.38 

u 11 IIHH '.r * >m 

stoichiometric. The air-fuel ratio during a given stroke is determined by the 

engine power requirements, which govern the amount of fuel injected. 

The minimum air-fuel ratio for complete combustion in a diesel is 

about 21, corresponding to about 50 percent excess air. This rati o is known as 

the smoke limit, since smoke increases dramatically at ratios lower than this. 

The smoke limit establishes the maximum amount of fuel that can be burned per 

stroke, and thus the maximum power output of the engine. 

NO in the diesel engine is primarily NO, which is formed at high 

temperatures close to the flame front in the presence of excess oxygen. The 

rat e of NO formation in diesels is a function of oxygen availability, and is 

exponentially dependent on the flame temperature. In the diesel engine, most 

of the NO emitted is formed early in the combustion process, when the piston 

is stil l near top-dead-center (TDC). This this is when the temperature and 

pressure of the charge are greatest. Recent work by several manufacturers and 

consultants (Wade et al. , 1987; Cartellieri and Wachter, 1987; mfrs. confidentia l data) indicates that most of this NO is actually formed during the 

premixed burning phase, and that reducing the amount of fuel burned in this 

phase can significantly reduce NO emissions. NO can also be reduced by 

actions which reduce the flame temperature during combustion. These actions 

include: delaying combustion past TDC, cooling the air charge going into the 

cylinder, reducing the air-fue l mixing rate near TDC, and exhaust gas recirculation (EGR). Since combustion always occurs under near-stoichiometric conditions, reducing the flame temperature by "lean-burn" techniques, as in sparkignition engines, is impractical. 

Diesel soot is formed only during the diffusion burning phase of 

combustion. Most of the soot formed is subsequently burned during the late r 

portions of the expansion stroke. Soot oxidation is much slower than soot 

formation, however, and the amount of soot oxidized is heavily dependent on the 

availability of high temperatures and adequate oxygen during the late r stages 

of combustion. Actions which decrease the amount of fuel burned in the 

2-12 
diffusion burning stage tend to decrease soot emissions (at the cost of an 

increase in NO ). Actions which reduce the availability of oxygen (such as 

EGR, or operation at low air-fuel ratios), or which reduce the time available 

for soot oxidation (such as retarding the combustion timing or reducing the 

air-fuel mixing rate) tend to increase soot emissions. 

Diesel HC emissions (as well as the unburned-fuel portions of the 

particulat e SOF) occur primarily at light loads, as a result of excessive 

fuel-air mixing, producing a mixture too lean to burn. Other HC sources 

include fuel deposited on the combustion chamber walls by the injection process, fuel retained in the orifices of the injector which vaporizes lat e in 

combustion, and partly reacted mixture which is subjected to bulk quenching by 

too-rapid mixing with air. Advanced injection timing (especially at light 

loads and high speeds), higher bulk gas temperatures, and lower injection 

pressures tend to reduce HC emissions; high air swirl rates and high injection 

pressures tend to increase them. 

It is apparent from the foregoing discussion that there is an inherent conflict between some of the most powerful diesel NO control techniques 

and particulate emissions. This is the basis for the much-discussed "tradeoff" 

relationship between diesel NO and particulat e emissions. This "tradeoff" is 

not absolute—various NO control techniques have varying effects on soot and 

HC emissions, and the importance of these effects varies as a function of 

engine speed and load. These tradeoffs do place limits on the extent to which 

any one of these pollutants can be reduced, however. To minimize emissions of 

a l l three pollutants simultaneously requires careful optimization of the fuel 

injection, fuel-air mixing, and combustion processes over the full range of 

engine operating conditions. 

Visible Smoke—Visible smoke is due primarily to the soot component 

of diesel particulat e matter. Under most operating conditions, the exhaust 

plume from a properly adjusted diesel engine is normally invisible , with a 

tota l opacity (absorbtance and reflectance) of two percent or less. Visible 

2-13 
P.40 

I'P «•! I f.«V ' ' 

smoke emissions from heavy-duty diesels are typically due to operating at 

air-fuel ratios at or below the smoke limit, or to poor fuel-air mixing in the 

cylinder. Poor mixing may occur during "lug-down" (high-torque operation at 

low engine speeds) since turbocharger boost, air swirl level, and fuel injection pressure are typically poorer in these "off-design" conditions. Marginal 

air-fue l ratios also occur in full-power operation of naturally-aspirated 

engines, resulting in some visibl e smoke under these conditions. 

In turbocharged engines, low air-fuel ratios can occur during transient accelerations, since the inerti a of the turbocharger rotor means that the 

a ir supply during the first few seconds of a full-power acceleration is less 

than the air supply in steady-state operation. To overcome this problem, 

turbocharged engines in highway trucks incorporate an acceleration smoke 

limiter, which limits the fuel flow to the engine until the turbocharger has 

time to respond. This reduces the transient power and torque available from 

the engine, however. For this reason, smoke limiters are not commonly used in 

most off-highway applications. 

2.4 Emission Regulations 

Emissions from diesel engines used in on-highway trucks and buses 

have been regulated since 1972. Due to the variety of heavy-duty truck sizes, 

types, and applications, i t has been considered impractical to specify 

heavy-duty emissions limits in terms of pollution per unit of distance travelled (e.g. grams per mile), as is done for light-duty vehicles. Instead, 

heavy-duty emissions regulations are written to apply to the engine, rather 

than the vehicle. The emissions limits are expressed in terms of grams of 

pollution per unit of work output from the engine, as measured over a specified 

test cycle on an engine dynamometer. The specific units of the U.S. regulations are grams of pollution per brake horsepower-hour (g/BHP-hr). 

Federal and California emissions limits established for heavy-duty 

on-highway diesel engines are shown in Table 2-2. Regulated pollutants include 

2-14 
TABLE 2-2. FEDERAL AND CALIFORNIA EMISSIONS REGULATIONS FOR HEAVY-DUTY DIESEL ENGINES 

ro 

^ _ i 

Ln 

Federa l 

1974-1978 

1979-1984 

1985-1987 

1988-1989 

1990 

1991-1993 

1994+ 

Californi a 

1973-1974 

1975-1976 

1977-1979 

1980-1983 

1984-1987 

1988-1990 

1991-1993 

1994+ 

CO 

(g/BHP-hr) 

40 

25 

15.5 

15.5 

15.5 

15.5 

15.5 

40 

30 

25 

25 

15.5 

15.5 

15.5 

15.5 

HC 

(g/BHP1.5 

1.3 

1.3 

1.3 

1.3 

1.3 

1.0 

1.0 

1.3 

1.3 

1.3 

1.3 

h r ) 

1 6 a 

ioa 

1 6 a 

ioa 

6.0 a 

NO 

(g/BHP^hr) 

10.7 

10.7 

6 . 0 

5 . 0 

5 . 0 

7 . 5 

5 . 1 

6 . 0 

5 . 0 

5 . 0 

PM 

(g/BHP-hr) 

NR 

NR 

NR 

0 . 6 

0 . 6 

0.25 

0 . 1 

NR 

NR 

NR 

NR 

NR 

0 . 6 

0.25 

0 . 1 

Test 

Procedure 

13-Mode 

13-Mode 

Transient 

Transient 

Transient 

Transient 

Transient 

13-Mode 

13-Mode 

13-Mode 

13-Mode 

Transient 

Transient 

Transient 

Transient 

Smoke Opacity 

(Ace/Lug/Peak, Z) 

20/15/50 

20/15/50 

20/15/50 

20/15/50 

20/15/50 

20/15/50 

20/15/50 

b 

b 

b 

b 

b 

b 

b 

b 

1 

NR: Not regulated 

Sum of NO plus HC emissions. 

x 

Federal Smoke Standard applies. 
P.42 

carbon monoxide (CO), hydrocarbons (HC), oxides of nitrogen (NOx), and (beginning in model year 1988) particulat e matter (PM). As a practical matter, 

however, only the NO and PM regulations are of much significance, since diesel 

HC and CO emissions are much lower than the standards (which were written for 

gasoline engines). 

A separate regulation also limits the maximum smoke opacity for 

on-highway diesel engines. This had some effect in limiting particulate 

emissions prior to the establishment of the PM standard. However, compliance 

with future PM emissions limits will result in smoke opacity levels far below 

the regulated values, essentially rendering the opacity regulation irrelevant. 

Test procedures—the test cycles and other procedures under which 

emissions are measured are as important as the numerical emissions limits. 

Until 1985, gaseous emissions were measured on the "13-mode" cycle. This cycle 

consisted of steady-state operation at ten different power and speed settings, 

with intervening periods of idle . Since diesel HC, CO, and PM emissions are 

heavily influenced by transient operation, the steady-state 13-mode procedure 

was considered a poor predictor of in-use emissions of these pollutants by 

highway vehicles. For this reason, it has been superseded by the current 

Federal Heavy-Duty Transient Test Procedure. In this procedure, engine speed 

and load are continuously varied according to a fixed schedule, which is 

intended to simulate typical urban driving. 

Unlike highway trucks, most off-highway diesel applications include 

littl e transient operation (construction equipment is the major exception). 

Thus, the 13-mode cycle, with its steady-state operation, may produce more 

representative results than the transient procedure for these engines. This is 

fortunate, since virtuall y all of the available data on off-highway diesel 

emissions are based on the 13-mode or some other steady-state operating cycle. 

Appropriate test cycles for individual classes of equipment are discussed 

further in Sections Four through Eight. 

2-16 
3.0 TECHNOLOGY FOR EMISSIONS CONTROL 

This sectio n summarizes the current stat e of the art in diese l 

emissions control . Emissions control technology for high-speed, on-highway 

diese l engines has advanced rapidl y over th e last few years due t o recent EPA 

and Californi a ARB regulation s imposing "technology forcing" emissions stan -

dards for the 1988, 1991, and 1994 model years. These developments ar e 

described a t length in another Radian report (Weaver and Klausmeier, 1987), 

from which most of Section 3.1 has been adapted. Many of thes e developments 

a r e directl y applicabl e t o high-speed off-highway engines as well . Progress 

in controllin g emissions from medium-speed engines has been much more limited . 

This is a t least partl y due t o the lack of significan t regulator y pressur e on 

this engine class. Emission controls for these two engine classe s ar e 

discussed separatel y below. 

3.1 High-Speed Engines 

Virtually all heavy-duty diesel engine manufacturers have mounted 

intensive research and development efforts in emissions control, in order to be 

able to comply with the 1988 and 1991 emissions standards. Compliance with the 

1988 standards has been attained, and compliance with the far more stringent 

1991 standards of 5.0 g/BHP-hr NO and 0.25 g/BHP-hr PM now appears within 

reach (Weaver and Klausmeier, 1987a). Since on-highway and off-highway 

engines are identical in their underlying technologies, al l of the basic 

research performed in this effort should be applicable to off-highway engines 

as well. Much of the application and design work should also be directly 

applicable to off-highway engines in Group 2, and (to a lesser extent) Group 

3. However, much detailed development and application engineering would stil l 

be needed to adapt these technologies to the different requirements and 

operating patterns of off-highway service. 

Overview—Diesel engine emissions of NO , PM, and HC can be reduced 

by carefully tailoring the air induction, fuel injection, fuel-air mixing, and 

other elements of the combustion process. This in-cylinder emissions control 

3-1 
P.44 

is limited by the tradeoffs discussed in Section 2.3. Diesel emissions can 

also be reduced through aftertreatment—physical or chemical treatment of the 

exhaust gases after they leave the cylinder. Table 3-1 lists the significant 

emission control technologies in use or under development in each of these 

categories for on-highway engines. 

The last few years have seen tremendous progress in the control of 

diesel engine emissions in the cylinder. As a result, i t now appears likely 

that many on-highway engines—especially those used in the largest or 

"heavy-heavy" truck class—may be able to comply with the 1991 emissions 

standards by in-cylinder means alone. If certification testing were conducted 

with low-sulfur fuel, most new heavy-duty on-highway diesel engines would be 

able to meet the 1991 standards without the use of a trap, although some would 

require the use of a catalyti c converter or other non-trap aftertreatment 

technique to reduce particulat e emissions. These advances have also brought 

the 1994 particulate standards of 0.1 g/BHP-hr within the range of 

possibility, given an efficient trap and low-sulfur fuel (Weaver and 

Klausmeier, 1987a). 

In-cylinder emissions control—Recent progress in in-cylinder emissions control has been made possible, in large part, by improved understanding 

of the diesel combustion process, and of the factors affecting pollutant 

formation and destruction. Pollutant formation and destruction in the cylinder 

are determined by the specific course of the diesel combustion process. 

Modifying this process to minimize pollution involves a complex multi-dimensional tradeoff between NO , HC, and PM emissions, fuel economy, power output, 

smoke, cold-start ability , cost, and many other considerations. These changes 

go to the heart of diesel engine design, and they have the potential either to 

dramatically enhance or dramatically degrade an engine's performance relative 

to its competitors. As a result, engine manufacturers have devoted the bulk of 

their research and development resources to this area. 

Most engine manufacturers have followed a broadly similar approach to 

in-cylinder control, although the specific techniques used differ considerably 

3-2 
P.45 

RADIAN 

TABLE 3-1 . TECHNIQUES FOR DIESEL ENGINE EMISSIONS CONTROL 

IN-CYLINDER CONTROLS 

Fuel Injection System 

Low sac/zero sac nozzles 

Retarded (fixed) injection timing 

Variable injection timing 

High injection pressure 

Transient smoke limiter 

Governor curve shaping 

Electronic fuel rate control 

Electronic injection timing control 

Reduced initial rate of injection 

Variable fuel injection rate 

Air charging system 

Turbocharging 

Intercooling 

Jacket Water 

Air-air 

Low flow air-water 

Separate circuit air-water 

Low-inertia turbocharger 

Variable geometry turbocharger 

Externally-driven turbocharger 

Turbocompound engine 

Mechanical supercharger 

Gas-dynamic supercharger 

Combustion Chamber 

Reduced crevice volume 

Optimized compression ratio 

Optimized air swirl ratio 

Variable air swirl ratio 

Re-entrant bowl combustion chamber 

Heat insulation 

Indirect injection 

Air ceil 

Reduced Oil Consumption 

Exhaust Gas Recirculation 

Continued 

3-3 
P.46 

TABLE 3-1 (Continued) 

AFTERTREATMENT CONTROLS 

Trap-oxidizer Systems 

Traps 

Cellular cordierite ceramic monolith 

Cellular mullite fiber trap 

Ceramic foam 

Conductive SiC monolith 

Woven silica-fiber "candle" trap 

Precious metal catalyzed wire-mesh trap 

Regeneration Techniques 

Diesel fuel burner/bypass 

Electric heater/bypass 

Exhaust temperature increase 

Catalyzed trap 

Catalytic fuel additives 

Catalyst injection in exhaust 

Reverse flow/recycling 

Catalytic Converters 

Cellular monolith 

Pellet-type 

Electrostatic Precipitator/agglomerator 

Selective Catalytic Reduction 

RapReNox Process 

3-4 
RADfAN 

from one manufacturer to the next. This typical approach to in-cylinder 

emissions control includes the following major elements. 

• Minimize parasiti c HC and PM emissions (those not directly 

related to the combustion process) by minimizing nozzle sac 

volume and reducing oil consumption to the extent possible 

• Reduce PM emissions at constant NO by refining the turbocharger/engine match and improving engine "breathing" 

characteristics. Many manufacturers are also experimenting 

with variable-geometry turbochargers to improve the 

turbocharger match over a wider speed range. 

• Reduce PM and NO (with some penalty in HC) by cooling the compressed charge air as much as possible, via air-air or lowtemperature air-water aftercoolers. 

• Further reduce NO to meet regulatory targets by severely 

retarding fuel injection timing over most of the speed/load 

range. Minimize the adverse effects of retarded timing on 

smoke, starting, and light-load HC emissions via a flexible 

timing system to advance the timing under these conditions. 

• Recover the PM increase due to retarded timing by increasing the 

fuel injection pressure and injection rate . 

• Improve air utilizatio n (and reduce PM emissions) by minimizing 

parasiti c volumes such as piston/cylinder head clearance and 

piston top land volume. 

• Optimize in-cylinder air motion through changes in combustion 

chamber geometry and intake air swirl to provide adequate mixing 

3-5 
P.48 

at low speeds (to minimize smoke and PM) without over-rapid 

mixing at high speeds (which would increase HC and NO ). 

• Control smoke and particulate emissions in full-power operation 

and transient accelerations through improved governor curve 

shaping and transient smoke limiting (generally through electronic governor controls). 

With a few notable exceptions (such as air-air aftercooling), these 

technologies should be applicable to the great majority of Group 2 and Group 3 

off-highway engines as well. Many would also apply to Group 4 engines, 

although the costs of some technologies (such as turbocharging and aftercooling) might prove prohibitive. 

In addition to these generally used approaches, a number of other 

promising in-cylinder control techniques are under development by various 

manufacturers. These include variable air swirl devices for improved control 

of in-cylinder air motion over a range of speeds; fuel injection pumps with 

electronic control of the fuel injection rate ; proprietary technology to 

minimize the initia l fuel injection rate , thus reducing premixed burning and 

NO emissions; and innovative supercharging technologies to minimize or eliminate turbocharger lag. Turbocompound engines, which are being developed 

primarily for fuel economy reasons, will also help reduce emissions somewhat 

through increased engine efficiency. 

It is striking that most of the in-cylinder emission reductions 

attained to date in on-highway engines have come from painstaking optimization 

and incremental improvements to engine design, rather than from the application 

of major new technologies. Technologies such as electronic timing control and 

governing have played a fairly minor role in reducing emissions, although they 

have certainly helped to offset some of the deleterious effects of emissions 

control on engine performance. This suggests that—as an interim 

solution—fairly substantial improvements in off-highway engine emissions might 

be obtainable quickly and at moderate cost through relatively minor design and 

3-6 
calibration changes. This could result in off-highway emissions levels 

comparable to those in truck engines meeting the 1988 standards. To attain 

emission levels comparable to those mandated for 1991 would require (in most 

cases) complete redesign and re-optimization of the engine—a very 

time-consuming and expensive process. 

Several technologies are conspicuously absent from the list of those 

under development for on-highway engines, due to their adverse effects on fuel 

economy or durability. The most significant of these are exhaust gas 

recirculation (EGR) and indirect injection. Properly modulated, EGR can 

significantly reduce NO emissions with a minimal increase in PM. Oil 

contamination and engine wear rates are increased by EGR, however, and 

manufacturers have been strongly resistant to its use. While relatively low in 

emissions, IDI engines are 5-10 percent less fuel efficient than DI-engines, 

and have lost market share as a result. The primary advantage of these two 

technologies is their low initia l cost. This makes them well suited to the 

small high-speed diesel engines in Group 4, for which their disadvantages of 

increased wear and fuel consumption are least significant. 

Aftertreatment control technologies—Potential exhaust aftertreatment 

technologies include trap-oxidizers and flow-through catalyti c converters, both 

of which would affect primarily PM and HC emissions. Due to the oxidizing 

nature of diesel exhaust, aftertreatment techniques for NO require that a 

separate reducing agent be supplied. Despite considerable publicity given to 

one such system, this approach is considered infeasible for general 

application in vehicles. 

Most of the research and development activity in diesel aftertreatment involves trap-oxidizers. A trap-oxidizer system consists of a durable 

particulat e filte r in the exhaust (the "trap"), along with some means of 

regenerating the filte r by burning off ("oxidizing") the collected particulate 

matter. Development activity is concentrated on the "oxidizer" portion of the 

system, as suitable filte r media have been available for some time. 

3-7 
P.50 

^ 

Progress in trap-oxidizer development has been slow. This is at 

least partly duj to the limited resources being devoted to trap-oxidizer R&D. 

Only a few manufacturers appear to have devoted major efforts to trap-oxidizer 

system development. Foremost among these is Daimler-Benz, which has placed 50 

prototype traps on buses operating in West Germany (Hardenberg, 1987). One 

other U.S. engine manufacturer has also devoted considerable effort to 

trap-oxidizer development, and has successfully accumulated more than 123,000 

miles on a prototype system. Trap-oxidizers have also been tested successfully 

in a number of underground mining applications (Brev et al. , 1987). 

The feasibility of trap-oxidizers in off-highway applications would 

depend on the specific application and operating conditions. The application 

of trap-oxidizers in trucks has been slowed by the need to ensure regeneration 

under al l possible operating conditions (including prolonged low-power 

operation), without intervention from the driver. Engines in many off-highway 

applications are subject to much higher and more consistent load factors than 

those in highway trucks. In addition, off-highway equipment operators tend to 

be more involved in monitoring and maintaining their equipment. A simpler 

(and thus less expensive) regeneration system would be feasible under these 

circumstances—indeed, such systems have seen good acceptance in underground 

mining. On the other hand, safety concerns (e.g. in boats) or packaging 

problems could rule out trap-oxidizer use in some off-highway applications. 

The success of in-cylinder particulate control efforts has led 

several manufacturers to investigate the feasibility of flow-through catalyti c 

converters for reducing particulate emissions. Given the low engine-out 

particulat e levels seen on current development engines, and the high organic 

content of the particulat e matter, the use of a catalyti c converter now appears 

as a possibly viable approach. By oxidizing much of the particulat e SOF, a 

catalyti c converter could reduce particulat e emissions by 25 to 35 percent, 

which would be enough to meet the 1991 standard. A catalyti c converter system 

would be much simpler and less expensive than a trap-oxidizer, since the 

3-8 
P.51 

flow-through design of the catalyti c converter avoids the problem of regeneration. The major drawback to the catalyti c converter approach in trucks is 

sulfate production—they would probably be feasible only with low-sulfur fuel. 

Catalytic converters in off-highway applications would be subject to the same 

safety and packaging concerns discussed above for trap-oxidizers. 

3.2 Medium-Speed Engines 

Due to the lack of regulatory pressure, the development of emission 

controls for the medium-speed diesel engines in Group 1 has lagged considerably 

behind that for high-speed, on-highway engines. Most emissions-related work on 

medium-duty engines has focussed on control of visibl e smoke, or on improving 

power output and fuel economy, with emission reductions only a side-effect. A 

limited amount of work on NO emissions control (primarily for locomotives) has 

also been performed, as will be discussed below. In addition, some studies 

have examined the effects of alternative fuels such as methanol and water/fuel 

emulsions on locomotive emissions and efficiency. 

Smoke/particulate control—Visible smoke from locomotives is an 

annoyance, and has been subjected to regulatory limits in various jurisdictions 

around the U.S. Poor public relations and soiling of railroad properties and 

rolling stock have also led to pressure to reduce smoke emissions. At the same 

time, many technical changes adopted to reduce fuel consumption and/or increase 

power output have also helped to reduce smoke emissions. Some of the changes 

since the early '70s have included: use of low-sac injection nozzles, higher 

fuel injection pressure, increased use of turbocharging, higher boost 

pressures, increased turbocharger efficiency, more effective aftercoolers, 

reduced parasiti c volume, and improvements in cylinder air flow (Kotlin and 

Williams, 1975; EMD, 1978). These have resulted in visibl e smoke levels (at 

sea level) in the 3-5 percent opacity range at full load. 

Due to the exhaust volumes involved, only a few measurements of 

medium-speed engine PM emissions have been performed. However, two sets of 

3-9 
P.52 

measurements on modern turbocharged locomotive engines performed a t Southwest 

Research have shown low t o moderate PM levels. ~Measured emissions ranged from 

about 0.26 g/BHP-hr for an EMD engine t o 0.48 g/BHP-hr for a GE engine in a 

line-hau l operating cycle . For a switch-engine duty cycle , emissions for the 

GE engine increased t o about 0.8 g/BHP-hr, but those for the EMD engine did not 

increas e a t all . These dat a ar e discussed a t greate r length in Section Four. 

The PM emissions from older-technology engines ar e hard t o estimate . 

Measurements by EMD on a 20-cylinder, turbocharged, 1973 model engine gave 

cycle-average PM emissions of 0.445 g/BHP-hr (EMD, 1978). These data may not 

be full y comparable to the SWRI data , however, due t o difference s in 

measurement technique . The only othe r PM emissions dat a extant for 

older-technology engines come from SWRI's Roots-blown 2-567 engine (Baker, 

1980). On 39-cetane fuel, brake-specifi c PM emissions from this engine ranged 

from 1.25 g/BHP-hr a t ful l load t o 0.7 g/BHP-hr a t intermediat e loads, and 

climbed t o about 1.0 g/BHP-hr a t ligh t load. If these laborator y dat a ar e 

representativ e of comparable engines in the field , those engines must be 

emitting substantiall y more than 1.0 g/BHP-hr averaged over their duty cycle . 

NOx control—To date , work on NO controls for medium-speed engines 

has been limite d t o laborator y studies, or t o modifications t o specifi c small 

groups of engines. Actual in-us e NO emissions from locomotive and othe r 

medium-speed engines ar e completely uncontrolled, and—as a result—ver y high. 

Typical NO emission factors for locomotives and medium-speed marine engines 

a r e in the range of 10 t o 16 g/BHP-hr. This is true even for very highly 

rate d turbocharged/aftercooled engines, which would be expected t o have lower 

NO emissions. 

x 

General Motors' Electromotive Division (EMD) has experimented with 

t h e use of retarded injectio n timing and increased injectio n rate s in it s 

645-serie s engines. Data from tests on thre e 16-cylinde r EMD engines with 

thes e modifications ar e shown in Table 3-1 . As th e tabl e indicates, NO 

x 

emissions were reduced by 52-67 percent (t o 6 g/BHP-hr), a t a cost in fuel 

3-10 
TABLE 3-2 . EFFECT OF ENGINE MODIFICATIONS ON GM ELECTRO-MOTIVE 

DIVISION (EMD) 16V-64E ENGINE PERFORMANCE AND EMISSIONS is 

i 

Model Application 

Maxi mum 

Rated 

Output 

(Hp at RPM) Changes 

Gaseous Emissions 

(g/bhp-Hr) 

NO CO HC 

Fuel 

Consumption 

(Lb/bhp-Hr) 

Smoke Opacity 

(%) 

E2, E8 Power Drilling 

u> 

i 

E7 Marine Supply 

2200 at 900 None 

6 degree retard 

6 degree retard, 

add turbo, change, 

piston, liner, 

and camshaft 

2875 at 900 None 

Modify to E7C, 

retard timing 

E9C Oil Well Drilling 3400 at 900 None 

13 degree retard, 

change injectors, 

and camshaft 

18.1 0.8 0.39 0.400 

11.1 1.9 0.39 0.410 

6.0 0.5 0.30 0.427 

12.4 

6.0 

15.1 

6.1 

0.9 

0.6 

0.38 

0.50 

0.3 

0.25 

0.32 

0.26 

— 

— 

0.350 

0.375 

5.0 

6.4 

4.0 

6.6 

Source: Mr. Hugh Williams, EMD, cited in Santa Barbara APCD (1987). 
P.54 

economy of about 7 percent. Smoke opacity was also increased somewhat, but HC 

emissions were reduced. PM emissions were not measured, but they were 

probably affected fairly little . PM emissions consist of soot plus heavy HC; 

the increase in smoke and reduction in HC would tend to offset each other. 

Another NO reduction study was conducted under the direction of the 

Santa Barbara Air Pollution Control District (1987). In this study, emissions 

from two EMD 12-645 engines on the supply boat Chesapeake Seahorse were 

reduced from an estimated 13.9 g/BHP hr in the uncontrolled condition to an 

average 8.3 g/BHP-hr at full load with moderately retarded injection timing. 

Use of room-temperature water (rather than engine cooling water) in the 

aftercooler of the starboard engine reduced the intake temperature by 9 C at 

full load, and gave a further NO reduction from 7.8 g/BHP-hr to 7.1 . Under 

cruise conditions, the reduced coolant temperature gave a 12 C reduction in 

intake air temperature (to about 62 C), reducing NO emissions from 9.2 to 7.6 

g/BHP-h. Air-air intercooling, or a more efficient air-water intercooler 

could have given 3-4 times this temperature reduction, and would likely have 

produced NO emissions in the 6 g/BHP-hr range. 

EPA has also funded studies of NO reduction techniques for EMD 

engines at Southwest Research Institut e (Storment et al. , 1974). The SWRI 

data show that retarded timing and EGR are both effective NO reduction 

x 

techniques. Retarded injection timing reduced NO emissions by 26 to 38 

percent, while 30 percent EGR reduced them by more than 50 percent, at the 

cost of a moderate increase in smoke opacity at full load. These studies were 

conducted with a Roots-blown 2-cylinder EMD 567 engine, however, and may thus 

be unrepresentative of the turbocharged/aftercooled EMD 645-series engines 

which make up most of the current population. 

Only very limited data are available on NO emission reductions in 

four-stroke engines. The most common four-strokes are the GE locomotive 

engines, which have NO emission factors in the 11 to 19 g/BHP-hr range 

(Ingalls, 1985). No emission control data for these engines are available. 

3-12 
Caterpillar was able to provide some limited data on the effects of retarded 

injection timing in its 3600-series engines, however. These data show a 

reduction of 7.2 percent in brake-specific NO emissions at full load (from a 

base of about 10 g/BHP-hr) for every degree of injection timing retardation. 

This is achieved at the cost of a 3.7 percent reduction in power, 0.9 percent 

increase in fuel consumption, and about .06 g/BHP-hr increase in dry 

particulat e matter (i.e . soot) emissions. The dry particulat e matter increase 

was calculated from smoke opacity measurements; actual tota l PM emissions were 

not measured. 

Alternative Fuels—Many medium-speed stationary engines are operated 

either wholly on natural gas or with dual natural gas/diesel fueling. 

Experiments with natural-gas fueled locomotive engines have been undertaken 

(Wakenell, 1987), and at least one locomotive fueled with compressed natural 

gas (CNG) has been tested in service (Olson and Reed, 1987). At present, 

manufacturers of stationary natural-gas engines are routinely guaranteeing NO 

emissions levels of 2.0 g/BHP-hr or less, using lean-burn techniques. The 

same lean-burn technology could conceivably be applied to mobile medium-speed 

engines. 

Some limited experimental work with methanol use in medium-speed 

engines has also been undertaken (Wood and Storment, 1980; Baker, 1981). 

Problems with damaging combustion knock at high methanol substitution levels 

have been found, and the emissions benefits have not been large. 

Feasibility of further emission controls—Although larger and 

slower-running, medium-speed engines are fundamentally similar to heavy truck 

engines in their basic combustion systems. Thus, most of the in-cylinder 

emission control techniques developed for truck engines should be readily 

adaptable to medium-speed engines as well. Some key emission control 

techniques applicable to medium-heavy diesel engines include: retarded 

injection timing in conjunction with increased injection pressure, 

electronically-controlled unit injectors, low-temperature aftercooling, and 

optimization of air flow and fuel-air mixing in the combustion chamber. 

3-13 
P.56 

Given equivalent levels of emissions control development and 

technology, medium-speed engines would be expected to produce lower emissions 

levels than high-speed engines. More time is available for combustion due to 

their lower rotational speed, so that the pre-mixed burning phase (which 

produces much of the NO ) should account for a smaller fraction of the total. 

For the same reason, the time available for the burn-out of soot particles 

formed during combustion is much greater, so that a smaller amount of soot 

should be emitted. 

In addition, lubricating oil from the cylinder walls presently 

accounts for a large fraction of PM emissions in high-speed engines. Due to 

their greater cylinder volumes (resulting in a higher power to wall area 

ratio), i t should account for a smaller fraction of medium-speed PM emissions. 

Finally, medium-speed engines normally operate under steady or quasi-steady 

stat e conditions, as opposed to the highly transient operating conditions 

experienced by truck engines. Assuming that the test cycle adopted reflected 

these conditions, the brake-specific PM and HC emissions from medium-speed 

engines would be expected to be lower for that reason alone. 

3-14 
4 . 0 LOCOMOTIVES 

Railroad locomotives ar e overwhelmingly diese l powered, and their 

larg e numbers and large power output per unit make them one of the most significan t off-highway emission sources. Railroading has undergone major changes in 

the last decade, due to the impact of highe r interest rates, high fuel prices, 

and deregulation . These have resulte d in a smalle r number of locomotives being 

used more intensivel y than in the past , and in considerabl e technica l upgrading 

of existin g locomotives. These trends have probably had the effec t of lowering 

railroa d emissions (as well as fuel consumption) significantly . However, sale s 

of new locomotives have dropped dramatically since the lat e '70s, resultin g in 

a slower turnover of the existin g fleet . 

4.1 Engine Characteristic s and Operating Conditions 

Modern railway locomotives ar e almost exclusivel y diesel-electric . 

In this arrangement, the diese l prime mover drive s an electri c generator; 

current from which drive s the individua l electri c tractio n motors tha t drive 

the wheels. This has the effec t of isolatin g the diese l engine from changes in 

locomotive speed and load. The locomotive control system provides for eight 

engine/generato r power levels or "notches" , plus idl e and dynamic brake (in 

which the wheel motors ar e used as generators t o slow the train) . In any given 

notch, the diese l engine runs a t constant speed and load. Engine RPM and power 

output change only as a result of changes in the notch setting . Thus, 

transien t effects on locomotive emissions ar e probably minimal. 

In 1982, the average horsepower for al l locomotives was 2,341 (Sta -

tistica l Abstrac t of the U.S. , 1985). Individua l locomotives range from under 

1,000 hp to over 7,000 hp (McDonald, 1986). Units 1,500 hp and below ar e 

generall y used exclusivel y for switching and transfe r purposes (moving small 

groups of cars around a switchyard, or deliverin g them within an urban area). 

Switching locomotives make up approximately 19 percent of the U.S. locomotive 

4 - 1 
P.58 

population (Ingalls, 1985). Larger general-purpose locomotives (typically 

2,000 to 4,000 hp) are designed primarily for line-haul (intercity) operation. 

However, many larger general-purpose locomotives (especially older ones) are 

also used in switching and transfer applications. Based on data in Ingalls 

(1985), Radian estimated that about 8,700 of the 22,900 locomotives used in 

1986 by U.S. Class 1 railroads were assigned to line-haul service, with the 

rest being used in switching and transfer applications. Line-haul operation is 

estimated to account for about 72 percent of tota l railroad fuel use, however 

(calculated from Ingalls, 1985). 

The vast majority of diesel-electri c locomotives are powered by 

medium-speed, large-bore diesel engines of 1,000 to 4,000 hp. Ninety-five 

percent of al l U.S. locomotives in use were manufactured by just two companies: 

General Electric (14 percent) and the Electromotive Division (EMD) of General 

Motors (81 percent) (Ingalls, 1985). Most of the remainder were produced by 

Bombardier, a Canadian company, using Alco engines. Some of the 

recently-introduced Caterpillar 3600-series engines have also been used in 

locomotive applications. 

EMD locomotives are powered by EMD-produced, large-bore, medium-speed 

(900-1,000 RPM maximum) two-stroke diesel engines driving electri c generators. 

Current EMD general-purpose units are powered by turbocharged 16-cylinder 

engines of 645 and 710 cubic inch displacement per cylinder, and have a horsepower range from 2,200 hp to 3,950 hp. EMD offers switching locomotives 

powered by eight and twelve-cylinder versions of the 645 engine. These engines 

are typically Roots-blown and generate 1,100 hp to 1,650 hp. 

The EMD 645 and 710-series engine families are direct descendents of 

the EMD 567-series Roots-blown locomotive engines originally introduced in 

1938. This engine family has been continuously improved and uprated over the 

years with the addition of turbocharging, intercooling, increased displacement 

per cylinder (to 645 cubic inches in 1966, 710 in 1985), improved component 

designs, and higher power ratings. As a result of EMD's design philosophy, 

most of the improved components developed over the years can be retrofit to 

4-2 
P.59 

existing engines when they are rebuilt (Kotlin and Williams, 1975). As a 

result, many different versions of the EMD engines are now in service, incorporating varying levels of technology and having varying emissions levels. 

General Electric line-haul and general purpose locomotives are also 

powered by large-bore, medium-speed diesel engines driving electri c generators. 

GE general purpose units are typically powered by GE FDL-12 cylinder, 3,000 

hp turbocharged engines and have a maximum speed of 70 mph. GE (and also ALCO) 

engines differ from EMD engines in using a four-stroke rather than a two-stroke 

cycle. The GE FDL series runs from an 8 cylinder, 1,800 hp unit to a pair of 

16 cylinder, 3,600 hp units (Ingalls, 1985). Most current GE switching units 

are powered by high-speed (1800 RPM) diesel engines purchased from an outside 

supplier—typically twin Cummins 6 or 8 cylinder, 300 to 550 hp, 4 stroke, 

turbocharged engines. 

4.2 Current Emission Factors 

Gaseous emission factors (HC, CO, NO ) and operating cycles for 

locomotives were addressed in a recent report by Southwest Research (Ingalls, 

1985). Ingalls compiled and compared gaseous emission factors from a number of 

published reports and manufacturer's data. Emission factors for a number of 

specific engine technologies are shown in Table 4-1 . Ingalls then combined the 

emission and fuel consumption factors shown in the table , using data on 

locomotive populations, to arrive at the composite emission factors shown in 

Table 4-2. However, Ingalls failed to account for the fact that older 

locomotives are likely to have been rebuilt using newer injector and 

combustion-system technology, and that the older and less-efficient locomotives 

probably see less intensive use. As a result, the composite factors shown in 

Table 4-2 probably overestimate HC and CO emissions somewhat, and may 

underestimate NO . Possible malfunctions and in-use deterioration would tend 

x 

to increase HC and CO, possibly offsetting this effect. 

4-3 
TABLE 4-1. MEASURED LOCOMOTIVE EMISSIONS FROM PUBLISHED STUDIES 

EXPRESSED IN GRAMS PER HORSEPOWER HOUR ON LINE HAUL CYCLES SJO 

Engine Description 

Number 

Tested 

Avg. Emissions, g/bhp-hr. (range) 

HC CO NO a 

ea 

FDL, old speed schedule 4 

(1957 to approx. 1974) 

FDL, new speed schedule 5 

(approx. 1973 to present) 

FDL, new speed sch. low sac injectors 1 

General Electric Engines 

2.2 (1.7 to 2.5) 

2.3 (2.0 to 2.6) 

0.6 

4.2 (3.6 to 4.5) 14.0 (10.9 to 18.9) 

2.5 (2.0 to 3.0) 14.2 (10.4 to 19.7) 

1.8 10.7 

** EMD 567 spherical injectors pre 1959 1 

EMD 567 needle injectors 1959 to 1966 1 

EMD 567 low sac injectors (retrofit 1 

after 1972) 

EMD 645E blown, needle injector unknown 

(1966 to 1972) 

EMD 645E turbo, needle injectors 

(1966 to 1972) 

EMD 645F3B turbo, low sac injectors unknown 

Electromotive Division 

2.7 

1.2 

0.7 

1.1 

0.8 (0.7 to 0.9) 

0.4(a) 

(a) 

v 'on UIC/ORE cycle 

Source: Ingalls (1985) 

6.4 

10.7 

7.4 

10.8 

12.1 

9.8 

13.0 

12.5 

3.2 (2.5 to 4.0) 11.6 (8.7 to 11.6) 

0.6 (a) 14.1 (a) 
P.61 

TABLE 4-2 . EMISSION FACTORS FOR RAILWAY LOCOMOTIVES 

Sourc e HC CO NO PM 

X 

Ingalls (1985) Composite 

Switch 47.4 86.6 468 

Line-haul 38.9 226 558 

Combined 41.3 187 533 

SWRI Studies 

GE 12-7FDL 

Switch 

Line-haul 

Combined 

EMD 12-645E31 

Switch 

Line-haul 

Combined 

Best Estimate 

Switch 

Line-haul 

Combined 

Calculated by Radian using data from SWRI. These tests were described by 

Baker et . al. , (1984) . 

2 Radian estimate , assuming a mix of old and new locomotive engines. 

3 

Radian estimate , assuming 80% EMD and 20% GE engines. 

106 

63 

73 

33 

18 

22 

47.4 

38.4 

41.3 

229 

162 

177 

104 

95 

97 

86.6 

226 

187 

537 

403 

433 

577 

537 

546 

468 

558 

533 

40 

17 

22 

12 

12 

12 

4°3 13J 

20 

4-5 
P.62 

To obtain more representativ e data on railway emissions, the Association of American Railroad-

! (AAR) commissioned measurements on 40 locomotives in 

the earl y '80s. Although these dat a have been released to EPA, they have not 

been made public , and Radian was unable to obtain access t o them. These data , 

if available , would shed additiona l ligh t on the question of appropriat e 

gaseous emission factors for locomotives. 

Due t o the difficult y of building an appropriately-size d dilutio n 

tunnel, data on particulat e emissions from diese l locomotives ar e extremely 

scarce . Our literatur e survey turned up measurements on only four engines, of 

which thre e were conducted a t Southwest Research Institut e (SWRI). The fourth 

was made by EMD, using a differen t procedure, and may not be comparable to the 

thre e SWRI measurements. 

SWRI performed gaseous and particulat e emissions measurements on one 

EMD 12-645E3 and one GE 12-7FDL engine as part of a study of the effects of 

heavy blended fuels (Baker et al. , 1984). Due to uncertaintie s in the mass 

flow measurements, Baker e t al . reported the emissions data in terms of concentration , rathe r than g/BHP-hr. At Radian's request, however, SWRI recalculate d 

the modal emissions data for the baselin e tests (using standard diese l #2) to 

report g/BHP-hr and lb/1000 gallons. From these data , Radian was able to 

calculat e cycle-weighted emission factors for HC, CO, NO and particulat e 

matter. The results of these calculation s ar e als o shown in Table 4-2; the 

data and calculation s themselves ar e given in Appendix A. 

As Table 4-2 indicates, particulat e emissions from the two modern, 

turbocharged/intercooled locomotive engines teste d by SWRI ar e relativel y low 

compared to othe r off-highway diese l engines—corresponding to about .26 and 

.48 g/BHP-hr for the EMD and GE engines, respectively . Earlie r SWRI dat a on an 

EMD 2-567 engine show considerably highe r PM emissions, however (Baker, 1980). 

These data showed PM emission factors on 39-cetane fuel ranging from 0.7 t o 

1.25 g/BHP-hr, depending on operating conditions. At the highe r BSFC of the 

4-6 
P.63 

567 engine, these values correspond to about 50-80 lb PM/1000 gallons. Hydrocarbons were also considerably higher, corresponding to about 100 lb/1000 

gallons at maximum power. 

The 567-series engine used in these tests incorporated older combustion and injection technology, and this is the likely cause of the higher 

emissions. Substantial reductions in locomotive smoke emissions due to improvements in engine technology have been documented (Kotlin and Williams, 

1975). It is also possible that emissions from this laboratory 2-cylinder 

engine may not have been completely representative of those from actual locomotives. 

Our "best-estimate" emission factors for locomotives are shown at the 

bottom of Table 4-2. For gaseous emissions, the factors for switching and 

line-haul duty cycles are taken directly from Ingalls (1985). For particulat e 

emission factors, we assumed that virtually all line-haul operation was performed by relatively low-smoke modern locomotives such as the two 12-cylinder 

engines tested at SWRI. Eighty percent of line-haul operation was assumed to 

be by EMD locomotives, and 20 percent by GE locomotives. 

For switching applications, we assumed that 50 percent of the fuel 

consumption was by older, high-emitting engines, with the other half split 80 

percent to EMD engines and 20 percent to GE engines. The older high-emitting 

engines were assumed to emit about 60 lb of PM per 1000 gallons of fuel 

consumed. The resulting composite PM emission factors are 13 lb/1000 gallons 

for line-haul operation and 39 lb/1000 gallons for switching. 

To combine the line-haul and switching-cycle emission factors into 

one overall factor, the values for the two cycles were weighted by the fraction 

of fuel consumed in each type of operation—72 percent to line haul and 28 

percent switching. These fractions were taken from Ingalls (1985), who used 

the same fractions to weight emissions of HC, CO, and NO in developing his 

composite emission factor estimates. 

4-7 
P.64 

4.3 Engine Population and Emissions Inventory 

Table 4-3 presents fuel consumption, population, and emissions 

estimate s for diesel-electri c locomotives used in switching and line-hau l 

service . These estimate s ar e calculated in two ways: for Class I railroad s 

only; and for al l locomotive engines, including those operated by Class II and 

I I I Railroads. Class I railroad s ar e those having gross operating revenues of 

$87.3 millio n or greater. These railroad s account for about 90 percent of al l 

railroa d revenues and 97 percent of ton-miles travelled . (Assoc, of Am. 

Railroads, 1986). Class II and II I railroad s ar e primarily switching and 

freight-transfe r operations connected with major citie s and ports, or 

short-lin e operations serving a limited geographic area . Because of their 

concentration in and near major cities, the Class II and Class II I railroad s 

include a disproportionat e amount of switchyard operation , and may thus 

contribut e a large r fractio n of the urban emissions. 

Table 4-3a shows the fuel consumption, locomotive population, and 

estimated emissions for Class I railroads. The tota l fuel consumption and 

population data for this tabl e ar e taken from the statistic s of the Association 

of American Railroads (1986), and ar e broken down int o line-hau l and switching 

activitie s following an assumed 72 percent/28 percent split . The AAR fuel 

consumption data do not include AMTRAK, so we added 60 millio n gallons for 

AMTRAK fuel consumption (U.S. Department of Transportation , 1985) to the AAR 

value . AAR locomotive numbers do include AMTRAK, so no adjustment was 

necessary. Total emissions were calculate d from tota l fuel consumption using 

the "best estimate " emission factors from Table 4-2. 

Table 4-3b shows estimate s of the locomotive population , fuel 

consumption, and emissions of Class II and II I railroads. Locomotive 

population data for these railroad s were obtained by summing the numbers of 

locomotives reported for these railroad s by McDonald (1986). All Class II and 

Class III railroa d locomotives were assumed to operat e in a switching cycle , 

with annual fuel consumption per locomotive equal t o tha t of switchers used by 

Class I railroads. 

4-8 
P.65 

TABLE 4-3 . POPULATION, FUEL CONSUMPTION, AND ESTIMATED 

EMISSIONS FOR RAILWAY LOCOMOTIVES 

No. 

Type Units 

(a) Class I Railroads 

Line-Haul 8,6992 

Switch 14.1702 

Total 22.8691 

(b) Class II and II I Railrc 

Switch 3,2364 

Annual 

Fuel Cons. 

(1000 Gal.) 

2.307,2873 

897,2783 

3.204.5651 

ads 

204,91l 2 

HC 

44,877 

21,265 

66,142 

. 4,856 

Emissions 

CO 

260,723 

38,942 

299,665 

8,893 

(Tons/Year) 2 

NOx 

643.733 

209,963 

853.696 

47.949 

PM 

14.997 

17.946 

32,943 

4,098 

(c) All Railroads 

Line-Haul 8,699 

Switch 17,406 

Total 26,105 

DOE Fuel Cons. Est. 

2,307,287 

1,102,189 

3,409,47 6 

3,209,729 

44.877 

26,122 

70,999 

260,723 

47,835 

308,558 

643.733 

257,912 

901,645 

14.997 

22,044 

37,041 

Sources: 

American Association of Railroads, 1986. 

2 Radian estimates. 

3 

Calculated from duty cycle s in Ingalls (1985) 

McDonald, 1986. 

Energy Information Admin., 1985. 

4-9 

J 
P.66 

RADIAN 

For comparison, Table 4-3 also shows the DOE estimate of railway fuel 

deliveries for 1985. This value was based on data obtained from the 

Association of American Railroads, and thus compares well with the data on 

Class I railroad fuel consumption taken from AAR statistics. 

4.4 Emissions Test Cycle 

Since locomotive engines operate in only a few well-defined operating 

conditions, definition of an appropriate test cycle should be relatively 

straightforward. The emission factors in Section 4.3 are based on two such 

test cycles: one for line-haul operation and one for switching. These cycles 

consist essentially of two different sets of weighting factors for the 

steady-state emissions measured for each operating mode. Transient effects (if 

any) are thus ignored. For line-haul operation, this is probably appropriate, 

as the time spent in notch-to-notch transitions is small compared to the tota l 

operating time. Switching duty involves much more transient operation, 

however, and thus may not be adequately modeled by a steady-state test 

sequence. This is a concern, since switching and transfer operation are 

responsible for a large fraction of locomotive emissions in urban areas. 

Further research to clarify this point is recommended. 

In addition to the transient emissions question, the appropriate 

weighting of different operating modes within each cycle, and of switch versus 

line-haul operation, should be re-examined in the light of recent changes in 

operating patterns. Qualitatively, railroads appear to be making more 

efficient use of equipment, and to be shutting locomotives off more when they 

will not be used for a some time. Both of these trends should reduce idling 

time, while increasing the time spent in notches 1-8 and dynamic brake. 

Ingalls (1985) addressed these issues, but without data to resolve them. 

Acquisition of actual current operating data would be needed to fully settl e 

this issue. 

4-10 
4.5 Feasibility of Emissions Control 

H 

From the data presented in Section 3.2, it is clear that a substantia l reduction in locomotive emissions would be possible even with existing 

technology. With additional R&D in the field, even larger emission reductions 

could be expected. In this section, we consider two different levels of 

emissions control for new engines: an intermediate level attainable in the 

relatively short term (about 3 years), and relying essentially on existing 

technology; and an advanced level requiring a longer period for research and 

development. The first of these control levels is intended to be comparable in 

stringency to EPA's 1988 standards for on-highway diesel engines, while the 

second is intended to be comparable to the 1991 standards. The reader is 

warned that these are engineering estimates only, based on very limited data, 

and intended only to indicate the potential benefits of regulation in this 

area. Additional research to confirm these estimates would be, essential before 

these or any other emission standards were incorporated into law. 

Due to the engine manufacturer's practice of making new-technology 

components available for rebuilding older engines, much of the 

emissions-control technology discussed in Section 3.2 would be applicable even 

to existing locomotives. Thus, in addition to new engines emission levels, 

estimates of the feasible emissions control level for existing engines are also 

presented. In most cases, achieving these levels would requir.e rebuilding the 

engine, at a cost of $80,000 to about $200,000, depending on the extent of the 

modifications (Davis, 1986). This need not present a major barrier, however. 

If the engine were being rebuilt anyhow, the additional cost due to the 

emissions control modifications would be relatively small. Regulations to 

require best-available control technology on new, rebuilt, or substantially 

modified locomotives could be reasonable and practical, therefore. 

Intermediate level controls—Feasible intermediate-term emission 

controls for locomotive engines would include retarded injection timing, 

cooling-system modifications to reduce charge air temperature, increased 

4-11 
P.68 

injection pressure, and optimization of combustion chamber geometry, air flow, 

and locomotive notch settings for reduced emissions. Based on the data presented in Section 3.2, we estimate that these modifications could reduce NO 

x 

emissions below 6.0 g/BHP-hr. 

To ensure against an unacceptable increase in PM and HC emissions at 

this low NO level, a regulatory cap on these emissions would be desirable. 

Given the limited data available on PM emissions from these engines, the exact 

PM level achievable at 6.0 NO is unknown. However, based on the PM data 

x 

described above, experience with the on-highway truck standards, and a rela -

tively less stringent steady-state test cycle for locomotives, a PM emissions 

standard of 0.50 g/BHP-hr appears readily achievable. Based on Table 3-1, an 

HC emissions standard of 0.50 g/BHP-hr also appears reasonable. The resulting 

emissions standards and corresponding emission factors are shown in Table 4-4. 

Advanced emission controls—Since so littl e research has been done on 

medium-speed diesel emissions controls, the ultimate form of advanced emission 

controls for these engines is difficult to project. Some technologies which 

clearly could be applied, however, include electronically-controlled unit 

injectors, reduced oil consumption, higher compression ratios, reduced initia l 

rate of injection, and further optimization of fuel-air mixing and combustion. 

Vigorous application of these technologies should make possible a further 

reduction in NO emissions to about 4-5 g/BHP-hr, together with lower PM 

emissions. For this analysis, we assume levels comparable to the 1991 standards for on-highway engines, or 5.0 g/BHP-hr NO and 0.20 g/BHP-hr PM. 

Levels of emission control well below these limits could conceivably 

come about through the use of aftertreatment technologies (i.e . trap-oxidizers, 

catalyti c converters, or selective catalyti c reduction), alternative fuels (CNG 

or methanol), water/fuel emulsions and/or exhaust gas recirculation (EGR). EGR 

in conjunction with a water/fuel emulsion has been shown to be an especially 

effective emissions control technique for medium-speed engines (Wilson et al. , 

1982). Further research to establish the effects of these technologies on 

emissions and durability in actual locomotive engines is required, however. 

4-12 
P.69 

TABLE 4-4 . ESTIMATED ACHIEVABLE EMISSIONS CONTROL STANDARDS 

POR LOCOMOTIVE ENGINES 

Emission s 

Limit 

(g/BHP-hr) 

Equivalent 

Emission 

Factor 

(lb/1000 gal.) 

New Engines 

Intermediate Control Level 

NOx 

HC 

PM 

Advanced Technology 

NOx 

HC 

PM 

6.00 

0.50 

0.50 

5.00 

0.30 

0.20 

238 

20 

20 

198 

12 

8 

Existing Engines (retrofit) 

NOx 

HC 

PM 

8.00 

0.50 

0.50 

317 

20 

20 

Source: Radian estimates, 

4-13 
P.70 

Existing locomotives—Retrofit emission controls for existing locomotives would generally resemble the intermediate-level controls described above. 

However, not al l locomotive models would be equally adaptable to low-emission 

technologies, so some relaxation of the intermediate-level standards would be 

desirable for existing engines. We recommend that this relaxation be in the 

NO standard, since over-reducing NO can cause large increases in PM and HC 

emissions and fuel consumption. Research would be required to identify the 

control levels actually achievable, but a NO standard of 8.0 g/BHP-hr should 

be high enough to avoid any major deterioration in fuel economy or PM emissions. 

4.6 Cost-Effectiveness Analysis 

Table 4-5 presents some very rough estimates of the 

cost-effectiveness of controlling locomotive emissions. Two cases are 

considered: the "intermediate" standards for new engines, and the suggested 

retrofit standards for existing engines when they are overhauled. Both of 

these involve relatively near-term technology. The uncertainty in the cost and 

effectiveness of advanced-technology emission controls is too great to allow 

for any realisti c cost-effectiveness calculations. 

Calculation of cost-effectiveness values where more than one 

pollutant changes poses a difficult cost-allocation problem. The values in 

Table 4-5 were calculated by allocating all the cost of control to the 

reduction in HC and NO emissions, with no debit for the increase in PM. 

x 

Reductions in NO and HC are often combined in this way, since both pollutants 

contribute to ozone formation. Since both the "new" and the "existing" engine 

considered are turbocharged, with relatively modern technology, the major 

effect of emission controls in each case is a reduction in NO , with a minor 

x 

reduction in HC and a small increase in PM. Application of similar standards 

to an older (higher PM) locomotive would result in a PM decrease. 

4-14 
P.71 

TABLE 4-5 . ESTIMATED COST-EFFECTIVENESS OF EMISSIONS 

CONTROL FOR NEW RAILWAY LOCOMOTIVES 

EMISSIONS 

Emission Factors 

Baseline 

NOx 

HC 

PM 

With Controls 

NOx 

HC 

PM 

Annual Emissions 

Baseline 

NOx 

HC 

PM 

With Controls 

NOx 

HC 

PM 

(lb/1000 gal.) 

(tons/locomotive 

Emissions Reduction 

NOx 

HC 

PM 

Cos t-Ef fectiven es s 

NOx + HC 

year) 

(tons/locomotive 

($/ton) 

yea </> 

523 

32 

14 

238 

20 

18 

36.1 

2.2 

1.0 

17.2 

1.4 

1.3 

r) 

18.8 

0.8 

-0.3 

1.073 

New Engine Existin g Engine 

EMISSION CONTROL COSTS 

Initia l Cost $ 80,000 $100,000 

Engine Lif e (yrs) 15 7 

Amortized Cost/yea r @ 10% $ 10,518 $ 20,541 

Fuel Cons. Increas e 5% 3% 

Annua l Fue l Cons. (Gal) 

Baseline 138,000 140,680 

With controls 144,900 144,900 

Added Fuel Cost @ $0.80/gal $ 5.520 $ 3.376 

Addl. Ann. Maintenance $ 5,000 $ 5,000 

Annualized Control Cost $ 21,038 $ 28,917 

Per Locomotive 

533 

41 

20 

238 

20 

20 

37.5 

2.9 

1.4 

17.2 

1.4 

1.4 

20.2 

1.5 

0.0 

$ 1.332 

4-15 
P.72 

The data in Table 4-5 are based on rather high estimates of the costs 

of naeting emissions standards for medium-speed engines. These reflect the 

great cost of the engines themselves, the small sales volume (resulting in a 

greater cost per engine for development and certification), and the small 

amount of existing work on medium-speed engine emission controls. These values 

are considered to be somewhat conservative (in the sense of over-stating the 

cost of control)—actual costs per unit might well be less, but are considered 

unlikely to be significantly more. Despite this, the estimated costs-per-ton 

of NO + HC controlled are rather low compared to most other significant new 

source of NO reductions. Thus, imposition of intermediate-technology emission 

standards both on new locomotives and on existing locomotives when they are 

rebuilt should be a highly cost-effective emissions control strategy. 

4-16 
5.0 MARINE VESSELS 

Marine vessels included in this study include diesel-powered tug and 

towboats, passenger vessels, fishin g vessels, and privat e recreationa l craft , 

but not ocean-going ships. Worldwide, the vast majority of ocean-going ships 

(as well as most smaller non-recreationa l vessels) ar e now diese l powered, due 

t o the superior fuel efficiency of the diese l engine. These ships ar e 

doubtless significan t contributors to the emissions inventorie s in major port 

citie s such as Los Angeles or New York. For historica l reasons, however, few 

U.S.-fla g ships ar e diese l powered. Access of foreign-registere d ships 

(including motorships) t o U.S. ports is controlled by treaty , and would thus 

not be subject to regulatio n by EPA, even if othe r off-highway vehicle s were 

made subjec t t o such regulations. 

5.1 Engine Characteristic s and Operating Conditions 

Except for those used in oceangoing ships, the diese l engines used in 

marine vessels ar e primaril y high-speed engines from Groups 2 and 3, or 

medium-speed engines classed in Group 1. High-speed engines ar e used as the 

main propulsion in smaller craft , and for electri c generation on large r 

vessels. Vessels such as pleasur e craft , fishing boats, small workboats, and 

simila r vessels ar e typicall y powered by Group 2 engines simila r t o those used 

in highway trucks. The large r Group 3 engines ar e used in many tugboats, 

towboats, and simila r vessels. 

Many of the smalle r high-speed marine engines in use ar e 

naturally-aspirated , and the turbocharged ones may or may not be equipped with 

intercoolers. Most of the more powerful Group 2 engines and most Group 3 

engines in marine application s ar e turbocharged and aftercooled , however. To 

increas e power output stil l further, some engines in this group use 

low-temperature aftercooling , cooling the heat exchanger with water pumped from 

5-1 
P.74 

overside. However, many engines in this class stil l use jacket water 

aftercooling, due to t'*e possible corrosion problems involved (especially with 

sea-water). 

Most high-speed diesel engines in marine service in the U.S. were 

built by Detroit Diesel Allison, Caterpillar, or Cummins. The majority of 

these engines are equipped with direct injection combustion systems, and most 

use unit injectors. IDI engines in marine use include the Caterpillar 

300-series and a few light-duty engines used mostly in pleasure craft. The 

300-series IDI engines have been superseded in Caterpillar's product line by 

the direct-injected 35 00 series. They were extremely popular marine engines, 

however, and many remain in use. 

Main propulsion for most large, powerful working vessels such as 

large tugboats, rive r towboats, and offshore oil supply vessels is provided by 

locomotive-derived medium-speed engines such as the EMD 567 and 645 series and 

Alco locomotive engines. These engines are identical in every major respect to 

the similar-model engines used in locomotives. Stil l larger medium-speed 

engines, specifically designed for marine service, power Great Lakes freighters 

and similar vessels, including many oceangoing ships. Slow-speed diesel 

engines are used only in large ocean-going ships, where their very low 

rotational speed allows them to be direct-coupled to the propeller. As this 

report does not deal with ocean-going ships, slow-speed engines will not be 

discussed further. 

High-speed and medium-speed diesel engines used for vessel propulsion 

are normally coupled to the propellers through a set of reducing gears or 

"marine transmission", which provides forward and reverse motion, but only one 

reduction ratio . The engine speed is thus a constant multiple of the propeller 

speed, while the engine power output is determined by the propeller's power 

absorption curve. The vessel's helmsman controls the engines through a set of 

"throttles" , which change the engine speed setpoint of a constant-speed 

5-2 
governor. For a given "throttle " position, therefore, the engine RPM (and thus 

propeller RPM) is held constant, and the governor adjusts engine power output 

as needed to maintain this RPM setting. 

Propeller power absorption increases as the cube of the rotational 

speed. Thus, if the engine and propeller are properly matched, maximum engine 

power is produced only near the engine's rated speed, and the power required 

drops off rapidly as RPMs are reduced. Much of the engine's operating time, 

and most of the BHP-hr produced occur in "cruise" mode. Typical "cruise" RPM 

is about 80-95 percent of rated speed, corresponding to about 40-80 percent of 

maximum power. Like locomotive engines, marine engines also spend a great deal 

of time idling. This is due to the inconvenience of starting large diesel 

engines when cold, and to the need to have engine power available at short 

notice under many conditions. 

In addition to their main propulsion engines, larger marine vessels 

use smaller, high-speed diesel engines to drive generators for electrica l 

power. These engines (typically Class 2 or Class 4) are governed at 

synchronous speed, which is normally 1,800 RPM for U.S. vessels. To provide 

electri c power as needed, they generally run continuously, even when the vessel 

is docked, moored, or otherwise temporarily inactive. Since these engines are 

sized to handle the maximum expected electri c power demand, they run most of 

the time under rather light load. Unlike engines used for main propulsion, 

generator engines tend to be naturally aspirated, and have relatively high NO 

emissions as a result. 

5.2 Current Emission Factors 

Reliable emission factors for marine vessels equipped with either 

high or medium-speed engines are unavailable. While emission factors for these 

vessels are listed in EPA's AP-42 compilation of emission factorsj a review of 

the derivation of these factors (Ingalls, 1985) showed that they were computed 

incorrectly, and that they are based on a narrow range of engines which is no 

5-3 
P.76 

longer representative of those in use. In addition, AP-42 provides no data on 

particulate emissions from marine engines. Thus, we were forced to develop our 

own estimates of emission factors for high-speed and medium-speed diesel 

engines in marine use. 

The emission factors developed in this report are intended to 

represent composite emissions over the entir e engine duty cycle, for a broad 

range of engine horsepower ratings. AP-42, on the other hand, presents 

separate emission factors for each operating mode, and divides them into a 

number of rather narrow horsepower ranges. For these reasons, no direct 

comparison of the Radian and AP-42 emission factors is possible. 

The great majority of medium-speed diesel engines in marine use in 

the U.S. are essentially seagoing locomotive engines. Since the emission 

factors for locomotives are reasonably well defined, and since the duty cycle 

for marine engines is not too dissimilar from that of locomotives, i t was 

decided to apply the "best estimate" emission factors developed for locomotives 

to medium-speed marine engines as well. These factors (which are listed in 

Table 5-1) are the same as the composite of the line-haul and switching duty 

cycles listed in Table 4-3. 

Emission factors for high-speed diesel engines in marine service are 

also liste d in Table 5-1. These values are Radian estimates, based in part on 

the data used in developing the AP-42 emission factor estimates (Engineering 

Science, 1984) and partly on other data sources (Dowdall, 1987; Santa Barbara 

APCD, 1987). The particulat e emissions factors were based primarily on 

measurements in uncontrolled heavy-duty truck engines, (Weaver, et . al. , 1984) 

which may not be fully applicable in this case. All of the factors shown 

should be considered only very rough approximations—acquisition of better data 

through actual testing is strongly recommended. 

5-4 
P.77 

TABLE 5-1 . ESTIMATED CURRENT EMISSION FACTORS FOR DIESEL 

ENGINES USED IN MARINE APPLICATIONS 

EMISSION FACTORS 

g/BHP-hr lb/100 0 gal. 

High Speed Engine s 

HC 

CO 

NOx 

PM 

0.8 

3.0 

11.0 

0.6 

32 

119 

436 

24 

Medium Speed Engines 

HC 

CO 

NOx 

PM 

1.0 

4.7 

13.4 

0.5 

41 

187 

533 

20 

Sources: 

Radian estimate. 

2From Table 4-2. 

5-5 

J 
P.78 

5.3 Engine Population and Emissions Inventory 

Table 5-2 lists the estimated population and nationwide fuel 

consumption data for the major classes of diesel powered, non-oceangoing 

vessels in use in the U.S. These estimates should be understood as being very 

approximate—data on marine vessel populations and usage in the U.S. are 

fragmented, incomplete, and occasionally contradictory. Table 5-2 was patched 

together from 9 independent sources. We relied most heavily on the Army Corps 

of Engineers Summary of U.S. Flag Passenger and Cargo Vessels (Army Corps of 

Engineers, 1983). This report does not include al l relevant vessels, however. 

Data on the number of fishing and pleasure craft were obtained from other 

sources. 

The breakdown of the total horsepower shown in Table 5-2 into 

high-speed and medium-speed engines is based on only very limited data. 

Descriptions of the engines and horsepower ratings for tug and towboats are 

given in the Inland River Record (Owen, 1986). Analysis of a sample of these 

boats showed that only 20 to 25 percent of these boats are powered by 

medium-speed engines, but that these engines are responsible for about 60 

percent of the tota l horsepower for the group. Extrapolating from this limited 

information, we estimated that about 60 percent of dry cargo and/or passenger 

ship horsepower, 50 percent of ferry horsepower, and 20 percent of commercial 

fishing craft (over five tons) horsepower are generated by medium speed 

engines. 

Table 5-2 shows an estimate of the tota l annual fuel consumption by 

each class of marine vessels. These were calculated from the engine load 

factors and annual usage shown in the table , and an assumed fuel consumption of 

0.4 lb/BHP-hr. The load factors and annual usage values shown are Radian 

estimates, based on typical operating patterns for each class. These values 

are only rough approximations, as actual data on load factors and hours of 

operation are lacking. 

5-6 
TABLE 5-2. ESTIMATED NATIONWIDE POPULATION AND EMISSIONS FROM DIESEL ENGINES USED IN MARINE APPLICATIONS 

Diesel 

Vessels 

Total 

Horsepower 

(1000s) 

Load Usage 

Factor (Hr/Yr) 

Ann. Fuel 

Consumption 

(1000 gal) HC 

EMISSIONS (TONS/YR) 

CO NOx PM 

Ln 

I 

Dry Cargo/Passenger 1,893 

High-Speed 

Medium-Speed 

Towboats and Tugboats 5,418 

High-Speed 

Medium-Speed 

1.2.3.4 

1.2 

Railroad Ferries 107 

High-Speed 

Medium-Speed 

General Ferries 1.000 

High-Speed 

Medium-Speed 

Fishing Craft 115.800 

> 5 Net Tons 24,000 

High-Speed 

Medium-Speed 

< 5 Net Tons 

High-Speed 91,800 

Pleasure Craft 

High-Speed 97,000 

1.2 

5.6 

5.6 

5.6 

1.7 

5.494 

2,198 

3.296 

7.988 

3.195 

4.793 

262 

79 

183 

1.000 

500 

500 

24.400 

12.000 

9.600 

2.400 

12,400 

17.500 

50% 

50% 

50% 

50% 

40% 

40% 

40% 

40% 

3.000 

3.000 

3.000 

4.000 

2.000 

2.000 

2.000 

2.000 

30% 

30% 

30% 

50% 

1,500 

2,000 

500 

200 

457.833 

183.133 

274.700 

798.800 

266.267 

532.533 

11,644 

3,493 

8.151 

44.444 

22.222 

22.222 

423.333 

320.000 

240.000 

80.000 

103.333 

97.222 

8.561 

2.930 

5.631 

15.177 

4.260 

10.917 

223 

56 

167 

811 

356 

456 

7,133 

5.480 

3,840 

1,640 

1,653 

1,556 

36.581 

10.896 

25.684 

65.635 

15.843 

49.792 

970 

208 

762 

3.400 

1.322 

2,078 

27.908 

21.760 

14.280 

7.480 

6.148 

5.785 

113.131 

39.923 

73.208 

199.966 

58.046 

141.920 

2.934 

762 

2.172 

10.767 

4.844 

5.922 

96.167 

73,640 

52,320 

21,320 

22,527 

21,194 

4.945 

2.198 

2.747 

8.521 

3.195 

5.325 

123 

42 

82 

489 

267 

222 

4.920 

3.680 

2.880 

800 

1.240 

1.167 

Total 221.218 

High-Speed 218,718 

Medium-Speed 2,500 

DOE Fuel Cons. Estimate 

56,644 

45,471 

11,173 

1.833,278 

915.671 

917.607 

1.894..265 

33.462 

14.651 

18.811 

140.279 

54.482 

85.796 

444.158 

199.616 

244.542 

20.164 

10.988 

9.176 

Radian estimate . 

'Including an estimat e of 

unreported craft (Crowell, 1986) 

,U.S. Army Corps of Engineers, 1983. 

.U.S. Maritime Administration, 1983. 

National Marine Fisherie s Service , 1984. 

John 0'Donnell, 1986. 

Moyat, 1986. 
P.80 

Total fuel consumption by al l classes shown in the table is 

approximately 1.8 billion gallons per year. A DOE report (Energy Information 

Administration, 1985) showing the tota l consumption of distillat e fuel oil for 

vessel bunkering at about 1.9 billion gallons, served to calibrate our 

estimate. The two numbers are not strictl y comparable, since the DOE value 

includes distillat e fuel consumed by oceangoing ships. These ships burn 

primarily residual fuel oil , but some use a certain percentage of distillat e 

fuel oil as well. This is offset to some degree by the fact that some 

non-oceangoing vessels can use residual oil or distillate/residua l blends. 

One other source of information on marine fuel consumption was 

located. Based on the results of a national freight transportation model, 

Argonne Laboratory (Millar et al. , 1982) estimated tota l energy consumption for 

tugs and towboats in the U.S. at about 147 trillio n BTU, or slightly over 1 

billion gallons of diesel fuel equivalent. Even considering that this value 

includes some non-diesel energy consumption, this is somewhat higher than the 

estimates in Table 5-2. 

Estimates of pollutant emissions from the various types of marine 

vessels are also presented and totaled in Table 5-2. These estimates were 

arrived at by multiplying the emission factors in Table 5-1 by the fuel 

consumption data calculated in Table 5-2. 

In terms of regional distribution, 55 percent of dry cargo and/or 

passenger ships are located on the Mississippi and Ohio Rivers, 35 percent 

along the U.S. coastline , and the rest are situated on the Great Lakes. A 

considerably different situation exists for railroad ferries where 90 percent 

are located on the coastline with the remainder on the Great Lakes. For 

towboats and tugboats, the percentages are 31 percent, 66 percent, and 3 

percent for the coastal areas, inland waterways, and Great Lakes, respectively 

(U.S. Army Corps of Engineers, 1983). These these statistic s indicate that a 

large percentage of domestic vessels operate on the Mississippi and Ohio 

5-8 
P.81 

5.5 Feasibility of Emissions Control 

Estimates of achievable emission standards for diesel engines used in 

marine applications are shown in Table 5-3. For new engines, two levels of 

emissions control are considered. The "intermediate" control level is intended 

to correspond in stringency to the 1988 on-highway emissions standards, while 

the "advanced technology" level corresponds to the standards scheduled for 

1991. In addition, Table 5-3 shows our estimates of achievable retrofit 

emission control standards for existing medium-speed and large high-speed 

engines. Again, the reader is warned that these are engineering estimates 

only, based on very limited data, and intended only to indicate the potential 

benefits of regulation in this area. Additional research to confirm these 

estimates would be essential before these or any other emission standards were 

incorporated into law. 

High speed engines 

Intermediate control level—High-speed engines are used both for 

propulsion and as prime movers for electri c generation. Although the duty 

cycles for these two types of operation vary somewhat, the applicable emission 

control technologies are essentially the same. At the intermediate control 

level, these technologies include: turbocharging with low-temperature 

aftercooling; increased boost pressure; retarded injection timing (with timing 

advanced at light loads to reduce HC and PM emissions); and changes in airflow, 

fuel injection, and combustion chamber design to minimize emissions. These 

technologies have al l been well demonstrated in on-highway engines, and the 

combination of high boost pressure with low-temperature aftercooling has seen 

increasing use in marine main propulsion engines as well. Application of these 

technologies across the board should be straightforward, therefore. The 

emissions levels achievable with these technologies should be comparable to the 

1988 standards for on-highway diesels. This is reflected in Table 5-3. 

5-10 
P.82 

Rivers. Since the Mississippi and Ohio Valleys and lower Great Lakes region 

are one of the densest clusters of urbanized areas in the United States, the 

impact of these emissions on humans could be significant. 

Fishing and pleasure craft, on the other hand, are located 

predominately along the U.S. coastline. The only major inland concentration of 

fishing craft is on the Chesapeake Bay, which accounts for 21 percent of 

fishing craft (National Marine Fisheries Service, 1984). Likewise, most 

inboard pleasure craft are operated on the coasts with the Great Lakes being 

the only major inland concentration. About 25 percent of these boats are 

operated on the great lakes (Cmdr. Scarborough, 1986). 

5.4 Emissions Test Cycle 

Relatively littl e investigation of marine engine duty cycles has been 

performed. From the few studies which have been done (e.g., Santa Barbara 

APCD, 1987), as well as discussion with vessel operators, it is clear that most 

of the fuel burned in marine operations is burned in cruise mode, with vessel 

maneuvering and idle making fairly minor contributions. Idle does account for 

a very significant fraction of the operating time, however, which suggests that 

it could be an important contributor to HC and PM emissions. Full-speed, 

full-load operation may also contribute significantly to PM emissions, since 

some vessels "cruise" at full power. Due to the dominance of steady-state 

operating modes, transient effects on emissions are probably negligible . 

These facts suggest that an appropriate test cycle for marine 

propulsion engines could consist of four steady-state operating modes: idle , 

light load/low RPM, "cruise" , and full load, with cruise and idle weighted most 

heavily. For generator engines, a single-speed, multi-power level test cycle 

(e.g. 2, 25, 50, 75, and 100 percent load at 1800 RPM) would give the most 

realisti c representation of in-use conditions. 

5-9 
TABLE 5-3. ESTIMATED ACHIEVABLE EMISSIONS CONTROL STANDARDS 

FOR MARINE DIESEL ENGINES 

Emissions 

Limit 

(g/BHP-hr) 

Equivalent 

Emission 

Factor 

(lb/1000 gal.) 

HIGH-SPEED MARINE ENGINES 

Intermediate Control Level 

NOx 

HC 

PM 

Advanced Technology 

NOx 

HC 

PM 

Existing Engines Over 300 HP (retrofit) 

NOx 

HC 

PM 

6.00 

0.50 

0.50 

5.00 

0.50 

0.25 

8.00 

0.50 

0.50 

238 

20 

20 

198 

20 

10 

317 

20 

20 

MEDIUM-SPEED MARINE ENGINES 

Intermediate Level 

NOx 

HC 

PM 

Advanced 

NOx 

HC 

PM 

Existing 

Technolc 

Engines 

D87 

(re trofit) 

NOx 

HC 

PM 

6.00 

0.50 

0.50 

5.00 

0.30 

0.20 

8.00 

0.50 

0.50 

238 

20 

20 

198 

12 

8 

317 

20 

20 

Source: Radian estimates, 

5-11 
P.84 

Advanced technology—The list of possible advanced emission control 

. .-chnologies for marine engines is essentially the same as the list of 

intermediate control technologies, with the possible addition of electronic 

timing controls. Exhaust gas recirculation would probably be ruled out for 

marine engines, due to its possible impact on engine reliability ; while 

catalysts and trap-oxidizers would likely be ruled out by fire-safety 

considerations. The emissions standards in Table 5-3 reflect these 

limitations. The PM level of 0.25 g/BHP-hr shown for the "advanced technology" 

standards—while numerically identical—is actually somewhat more lenient than 

the 1991 PM standard for on-highway vehicles. This is due to the fact that PM 

for marine vessels would be measured in steady-state operation, while the 

on-highway standard is based on a highly transient operating cycle. 

Retrofits—As with locomotive engines, high-horsepower marine engines 

are commonly upgraded to current technology levels when they are overhauled, 

and they can achieve an indefinite lifespan through repeated overhauls. Thus, 

as with locomotives, i t would make sense to consider requiring retrofit of 

emissions controls to these engines. The major changes required would be the 

pistons, injectors, and camshafts, (most or al l of which would be replaced in 

any event), plus possible changes in the turbocharger and aftercooler system. 

Since the engine would already be dismantled for overhaul, the added cost of 

these changes would be relatively small. For cost-effectiveness reasons, it 

would be desirable to limit this requirement only to the larger engines, which 

tend to see more intensive use. For our purposes, we have drawn the line 

arbitraril y at 300 HP, but further research to determine an appropriate level 

is recommended. 

Medium-speed engines 

The estimates of achievable emissions control levels for 

medium-speed engines in marine service are identical to the estimates 

previously presented for locomotive engines. The modifications required to 

5-12 
these engines would als o be essentiall y the same as those required for 

locomotive engines: upgrading engine compo lents, retardin g injection timing, 

increasing the injectio n rate , and modifying the engine cooling system to 

provide low-temperature aftercooling . Due to the availabilit y of the ocean as 

a heat sink, this last modification would be easie r and less expensive for 

marine engines than for locomotive engines. 

5.6 Cost-Effectiveness Analysis 

Table 5-4 shows some very rough calculation s of the 

cost-effectiveness of emissions control t o the "intermediate " leve l for new 

diese l engines of thre e types: medium-speed and high-speed main propulsion 

engines, and a high-speed generator engine . While they ar e very rough and 

approximate, these calculation s give some idea of the potentia l 

cost-effectiveness of controllin g these engines, compared t o othe r sources of 

potentia l emission reductions. As with locomotives, cost-effectiveness is 

calculate d based on the reduction in NO and HC emissions, and no credit or 

x 

penalty is taken for PM emission changes. No cost-effectiveness estimate s were 

made for "advanced technology" emission controls or for retrofits, due to the 

uncertaint y (and, for retrofits, the great variability ) of costs in these 

cases. 

For the medium-speed engine , the costs of emission control assumed in 

these calculation s ar e less than those assumed for a simila r engine in 

locomotive service . This is due primaril y t o the lower costs assumed for the 

low-temperature aftercooler. In a locomotive, this would requir e an air-ai r 

aftercoole r or a large separat e air-wate r heat exchanger, eithe r of which would 

be difficul t t o engineer into the limited space available . In marine 

operation , an effectivel y infinit e heat sink is availabl e in the water close 

overside , so tha t the cost of low-temperature aftercoolin g would be relativel y 

small. Maintenance costs would als o be lower, due t o the absence of the 

air-ai r heat exchanger and the less intensiv e use . The othe r costs assumed for 

this intermediat e control leve l ar e primaril y design, development, and 

5-13 
P.86 

TABLE 5-4 . ESTIMATED COST-EFFECTIVENESS OF EMISSIONS CONTROL 

POR DIESEL ENGINES USED IN MARINE APPLICATIONS 

Main Propulsio n Engine s 

Medium-Speed High-Speed 

Generato r 

Engine 

EMISSION CONTROL COSTS 

Engine Horsepower 

Initia l Cost 

Engine Lif e (yrs) 

Amortized Cost/year @ 10% 

Fuel Cons. Increas e 

Annual Fuel Cons. (Gal) 

Baseline 

With controls 

Added Fuel Cost @ $0.80/gal 

Addl. Ann. Maintenance 

Annualized Control Cost 

2,500 

$50,000 

20 

$5,873 

5% 

160,000 

168,000 

$6,400 

$3,000 

$15,273 

500 

$3,000 

15 

$394 

55 

12,500 

13,125 

$500 

$200 

$1,094 

200 

$1,000 

15 

$131 

5% 

16,000 

16.800 

$640 

$200 

$971 

P e r Engine 

EMISSIONS 

Emissio n Factors (lb/100 0 gal. ) 

Baselin e 

NOx 

HC 

PM 

With Controls 

NOx 

HC 

PM 

523 

32 

14 

238 

20 

18 

43 6 

32 

24 

238 

20 

20 

43 6 

32 

24 

238 

20 

20 

Annual Emissions (pounds per engine per year) 

Baseline 

NOx 

HC 

PM 

With Controls 

NOx 

HC 

PM 

83.680 

52 120 

2,240 

39,98 4 

3.360 

3,02 4 

5,450 

400 

300 

3,12 4 

263 

263 

6,97 6 

512 

384 

3,99 8 

336 

336 

Emission s Reductio n (pounds per engin e pe r year) 

NOx 43.696 2.32 6 

HC 1B760 138 

PM (784) 38 

2,978 

176 

48 

Cost-Effectiveness ($/ton) 

NOx + HC $672 $888 $616 

5-14 
certification costs, which (while large) would be spread over a large number of 

marine and locomotive engines. The additional manufacturing costs of 

refinements in injectors, combustion chambers, injection timing, etc . are 

relatively small. 

For the two high-speed engines, the approximate emission control 

costs shown were based on existing technology for on-highway truck engines. 

Technologies assumed were: turbocharging (for engines that don't have it 

already), low-temperature aftercooling, retarded injection timing, increased 

boost pressure, and optimization of combustion chamber and injector 

characteristics. The major costs in this package are for the turbocharger and 

aftercooler, and the design and certification costs for the engine. These were 

assumed to be fairly high, as the marine market is limited, and Coast Guard and 

American Bureau of Shipping regulations pose a formidable barrie r to new 

technologies. 

As Table 5-4 indicates, the potential cost-effectiveness of emissions 

control for new marine engines is about $600-$900 per ton. This is quite 

attractive when compared to the costs per ton for other available NO and HC 

reductions. 

5-15 
P.88 

6.0 FARM EQUIPMENT 

Self-powered farm equipment include s tractors, combines, mowers, and 

othe r self-propelle d machinery used in agriculture . For the last 20 years, the 

engines used in these vehicle s have been overwhelmingly diesel , and they ar e 

responsibl e for most diese l fuel consumption on farms. Engines in non 

self-propelle d equipment such as irrigatio n pumps, engine-driven blowers, 

conveyors, etc . ar e responsibl e for a relativel y small fraction of tota l fuel 

consumption and emissions, and ar e not discussed here . 

6.1 Engine Characteristics and Operating Conditions 

The largest group of agricultural diesel engines are those used in 

tractors. Tractor engines tend to be naturally-aspirated, direct-injected, 

4-stroke engines of moderate speed and power output (15-180 HP) and four to six 

cylinders. Engines used in small utilit y tractors are primarily Group 4 

engines of 15-50 HP and Japanese manufacture. Similar engines are also used in 

lawn and garden equipment. Larger tractor engines in the 40-180 HP range are 

often produced by the tractor builder, and are specifically designed for 

tractor use. In addition to supplying motive power, these engines are often an 

integral part of the structural framework of the tractor, with specially 

reinforced oilpans and engine blocks to carry the structura l load. These 

engines are classed in Group II, and a number of them have been adapted for use 

(in a non-structural role) in highway trucks as well. Examples include the 

John Deere 300 and 400-series engines and the Ford 6-cylinder diesel engines. 

Recent years have shown an increasing trend to higher tractor power 

rating and tractors of 400 HP and above are now available in four wheel drive 

tractors. These high-powered engines are generally adapted from those used in 

on-highway trucks, and are often turbocharged and intercooled for increased 

output (Implement and Tractor, 1986). Truck-type engines have also seen 

increasing use in smaller tractors, with makers such as Perkins and Isuzu 

supplying engines to tractor makers such as Massey Ferguson and White. 

6-1 J 
P.89 

Tractors undergo a varied and rigorous duty cycle. In addition to 

plowing, .plantingD cultivating,, hay baling, and other heavy agricultural work, 

tractors are used for mowings pulling wagons, front-end loading, driving fence 

posts, blowing snow, bulldozing^ and even light earthmoving jobs. The smaller 

utilit y tractors, as their name implies, tend to see a greater variety of 

applications, while the larger and more powerful tractors are primarily used 

for heavy field work. 

Combines,, windrowers„ cotton pickers, and other specialized 

non-tractor agricultural equipment undergo a less varied duty cycle. Engines 

for these vehicles are often equipped with medium-heavy duty truck engines such 

as the Navistar DT 466 and the Caterpillar 3208. These may be 

naturally-aspirated or turbocharged. In other cases, adaptations of tractor 

engines or (in a few cases) specially-designed engines are used. 

A weighted average of Harvest Publishing's 1985 Tractor Survey, the 

largest number of tractors in use were made by John Deere and International 

Harvester, both of which had produced about approximately 27 percent of the 

total . Other significant tractor manufacturers include Massey Ferguson, Ford, 

Allis-Chalmers, White, and J„I. Case, all of whom had produced from 7 percent 

to 10 percent of the tractors in use. Historically, John Deere, International, 

Ford, and Case have produced their own tractor engines, while Massey Ferguson, 

Allis, and White tend to use purchased engines. 

The agricultural equipment operations of J.I. Case and International 

Harvester were recently merged,, and new tractors produced by Case-IH will 

presumably be designed around the "B" and "C" engines produced by Case and 

Cummins in a joint venture arrangement. These engines are also targeted for 

the light-heavy and medium-heavy truck markets. 

6.2 Current Emission Factors 

The best data on emission factors for farm equipment are contained in 

a report to the California Air Resources Board by Environmental Research and 

6-2 
Technology (ERT) (1982). This report was sponsored by the farm equipment, 

constructio n equipment, and engint industrie s through their respective 

associations, and summarizes massive amounts of manufacturer-supplied data . 

Although the report deals specificall y with California , th e emission factor 

data contained in i t ar e the best availabl e for remainder of the U.S. as well. 

These data ar e presented in Table 6-1 . 

The dat a in the ERT report suffe r from severa l limitations. The most 

important of these is the absence of particulat e measurements. As a result , 

the PM emission factors in Table 6-1 were taken from AP-42 (EPA, 1985). These 

factors ar e based on emissions measurements on a limited sample of farm and 

constructio n equipment engines teste d a t Southwest Research in the earl y 70's 

(Hare e t al. , 1975). In comments on our Task One interim report , the Engine 

Manufacturer's Association (EMA) criticize d our use of these factors, statin g 

tha t they ar e no longer representativ e of farm and construction equipment 

today (Young, 1987). This criticism has some validity , especiall y for the 

large r truck-derived engines used in higher-powered equipment. No examples of 

these engines were tested in the SWRI program, and i t is not clea r tha t the 

emission factors developed for the smaller engines ar e appropriat e here . As a 

result , we have substitute d a value of 0.80 g/BHP-hr (based on pre-contro l 

particulat e emissions from heavy-duty truck engines) for the EPA emission 

factor for four-wheel drive tractors. 

For two-wheel drive tractors and othe r agricultura l equipment, we 

elected to retai n the EPA emission factors. While i t is tru e tha t many of the 

specifi c engine models tested by Hare et al . ar e no longer in use , ther e is 

littl e evidence to suggest tha t the new engines tha t replaced them ar e any 

cleaner, and no more recent emissions dat a ar e available . Research t o obtain 

more recent and applicabl e emissions data is strongl y recommended. 

Another limitatio n of the ERT dat a is tha t they ar e based on an 

adaptation of the old 13-mode steady-stat e test cycle , and thus do not account 

6-3 
RADIAN 

TABLE 6-1 . EMISSION FACTORS FOR FARM EQUIPMENT 

P.91 

HC1 

EMISSION FACTORS (G/BHP-HR) 

CO NOx PM2 

Equipment Type 

Tractor, 2WD 100+ HP 

Tractor, 4WD 

Tractor, 2WD, 20-90 HP 

Combines, Self-propelled 

Windrower, Self-propelle d 

Field Forage Harvesters 

Cotton Pickers 

Cotton Sprayers 

Orchard Sprayers 

Compact Loaders 

Fuel-Weighted Emission Factors 

lb/1000 gal 

g/BHP-hr 

1.84 

0.89 

2.16 

1.90 

2.21 

0.96 

2.23 

2.23 

2.23 

1.13 

72 

1.81 

4.23 

3.28 

6.42 

3.25 

6.85 

2.84 

3.78 

3.78 

3.78 

4.29 

182 

4.59 

11.59 

10.98 

10.94 

13.36 

10.50 

9.98 

7.78 

7.78 

7.78 

9.69 

456 

11.50 

1.28 

0.80J 

1.28 

1.51 

1.51 

1.51 

1.51 

1.51 

1.51 

1.51 

50 

1.25 

Sources: 

1ERT, 1982. 

2EPA, AP-42, 1985. 

3 Radian estimate. 

6-4 
RADIAfl 

for any transient effects. This is als o true of the PM data developed by Hare 

e t al . This is not a problem for most categorie s of farm equipment, since 

combines, windrowers, large tractors, etc . tend to be used primarily in nearly 

steady-stat e operation. It may be a problem for the smalle r tractors, however, 

as these units tend t o experience a fair amount of cycli c operation , and i t is 

certainl y a problem for the compact loaders. This issue is discussed furthe r 

in Section 6.4. 

Table 6-1 als o shows a se t of "fuel weighted" emission factors for 

farm equipment. These ar e simply the average of the emission factors for each 

equipment class, with each class' contributio n weighted by its estimated 

fractio n of tota l diese l fuel consumption by farm equipment. The estimate s of 

diese l fuel consumption by each class ar e shown in Table 6-2. 

6.3 Engine Population and Emissions Inventory 

Reasonably complete information on farm equipment populations and 

emission characteristic s is available . Population data ar e availabl e in 

numerous statistica l summaries of the agricultur e sector, and in estimate s 

developed by the Farm Implement and Equipment Institute , the industry 

association . Table 6-2 shows our estimate s of tota l populations, usage, fuel 

consumption, and emissions for the major classe s of self-propelle d farm 

equipment. These estimate s ar e based on FIEI revision s to USDA population 

numbers, and to the ERT estimate s of average horsepower and hours of usage per 

yea r (Young, 1987). As the tabl e indicates, the grea t bulk of agricultura l 

equipment emissions—accounting for about 85 percent of the total—ar e due to 

tractors, with combines the only othe r major source . 

Table 6-2 includes an estimat e of the tota l nationwide fuel consumptio n by agricultura l equipment, calculate d from the FIEI dat a and assuming fuel 

consumption of 0.4 lb/BHP-hr. Also shown in the tabl e is the Department of 

Energy's estimat e of tota l distillat e fuel deliverie s in the agricultura l 

secto r for 1985. This value is closel y comparable to the value calculate d from 

the FIEI data . 

6-5 
TABLE 6-2. ESTIMATED POPULATION, FUEL CONSUMPTION, AND 

EMISSIONS FROM DIESEL ENGINES USED IN FARM EQUIPMENT 

Equipment Typa 

Total Pent. Diesel Usage 

Population Diesel Population (hr/yr) 

Avg., 

H.P/ 

Annual 

Fuel 

A 

Load Consumption 

Factor (1000 Gal) HC 

EMISSIONS (TONS/YEAR) 

CO NOx PM 

I 

CT 

Tractor, 2WD 100+ HP 865,700 94% 813,758 410 

Tractor, 4WD 85,475 100% 85,475 530 

Tractor, 2WD, 20-90 HP 3,597,501 70% 2,518,251 300 

Combines, Self-propelled 500,000 75% 375,000 220 

Windrower, Self-propelled 110,000 20% 22,000 418 

Field Forage Harvesters 9,500 100% 9,500 390 

Cotton Pickers 20,000 70% 14,000 353 

Cotton Spreyers 2,700 70% 1,890 230 

Orchard Sprayers 20,629 10% 2,063 100 

Compact Loaders 113.400 23% 26,082 320 

141 

227 

56 

136 

75 

150 

115 

9 5 5 

70 

37 

0.55 

0.64 

0.34 

0.56 

0.55 

0.78 

0.55 

0.50 

0.35 

0.37 

1 

3 

3 

,437,436 

365,635 

799,125 

349,067 

21,074 

24,0B3 

17,366 

1,147 

281 

6,348 

,021,561 

,181,3386 

52,432 

6,451 

34,218 

13,148 

923 

458 

768 

51 

12 

142 

108,603 

120,536 

23,774 

101,704 

22,489 

2,862 

1,356 

1,301 

86 

21 

540 

274,669 

330,282 

79,586 

173,308 

92,449 

4,387 

4,765 

2,6^8 

•M7 

43 

1.219 

688,874 

36,474 

5,799 

20,277 

10,449 

631 

721 

520 

34 

8 

190 

TOTAL 75,103 

DOE/EIA Fuel Con6. Estimate 

3,868,019 

FIEI adjustments to USDA (1985) [Young, 1987). 

FIEI estimates (Young, 1987). 

FIEI adjustments to ERT (1982). 

.Calculated assuming fuel consumption of 0.4 Ib/BHP-hr. 

Radian estimate. 

Energy Information Admin., 1985, 

-o 

CO 
P.94 

Almost by definition , farm equipment emissions ar e concentrated in 

rura l areas. Although some farming often occurs even in highly urbanized 

regions, such as the South Coast Air Basin of California , diese l farm equipment 

for only 0.25 percent of the NO inventory in the SCAB. For comparison, in the 

heavily agricultura l Fresno are a (which, lik e the SCAB, is not in attainment of 

t h e Federal ozone standards) diese l farm equipment accounts for about 6 percent 

of the NO inventory. These estimate s were obtained by adjusting simila r 

figure s for gasoline and diesel-powered equipment (Ingalls, 1985) to reflec t 

only diese l engine-powered equipment. 

Using regiona l sale s figure s from the July 1985, Petroleum Marketing 

Monthly (EIA, 1985), a good nationa l distributio n of farm equipment emissions 

can be determined. It should be recognized tha t this distributio n is based on 

t h e premise tha t agricultura l sector fuel sale s and engine emissions ar e 

similarl y relate d in al l regions of the country. Using this tack , the New 

England state s account for .4 percent of farm relate d emissions, Mid-Atlantic 

state s account for 2.8 percent and, the rest of the easter n seaboard state s 

make up 8.4 percent. The Midwest accounts for a lion's share 49.2 percent of 

farm generated pollutants. The South and Northwest add another 16.7 percent 

and 6.0 percent, respectively , t o the farm emissions total . Finally , the West 

is responsibl e for the remaining 16.5 percent. 

6.4 Emissions Test Cycles 

As noted in Section 6-2, most types of self-propelle d farm equipment 

ar e used in essentiall y steady-stat e operation . For combines and othe r 

specialize d equipment, the engine generally experiences only a very limited 

range of operating conditions. For tractors, the range of operating conditions 

is larger, varying from high-speed, low load running in ligh t tasks t o 

sustained near-ful l power output in heavy work. For most tasks, however, the 

engine speed and power requirements do not vary greatl y from second to second, 

so tha t a steady-stat e test cycle would probably be adequate for measuring 

emissions. Although tractors in fiel d operation do experience some cycli c 

operation (when turning a t the end of a row, for instance ) these cycles ar e 

6-7 

J 
P.95 

long enough that the transient effects would probably be negligible. However, 

transient emissions measurements (using a realisti c cycle) on actual tractor 

engines would be desirable in order to confirm this assumption. 

An exception to the general rule of steady-state operation would 

occur in the case of compact loaders; and of tractors used for utilit y work 

(such as front-end loading) which involves repeated short-cycle operation. For 

these units, some sort of cyclic, transient duty cycle, similar to the 

construction equipment test cycles discussed in Section 7.3, might be more 

appropriate. At this point, the actual extent and emissions effects of cyclic 

operation in smaller tractors are unclear, and further research to resolve this 

question is recommended. 

6.5 Feasibility of Emissions Control 

As noted above, most tractor and other agricultural equipment engines 

are classed in Group 2, with the remainder being classed in Group 4. As both 

of these engine groups are closely related to on-highway engines, most emission 

control technologies developed for on-highway use should be readily adaptable. 

The differences in duty cycle, application requirements, and environmental 

conditions between the two types of applications will impose some limitations, 

however. In particular, the close integration of the engine and the equipment 

in tractors, loaders, and some other equipment types could result in delays or 

large economic penalties due to the adoption of emission controls. 

Tractors, loaders, and (to a lesser extent) other farm machines are 

literall y designed around the physical dimensions and operational capabilities 

of the engine. The physical dimensions of the engine determine the location of 

the tractor's hood and frame, and any changes to these dimensions may require 

redesign of major portions of the structure . In the same way, gear and final 

drive ratios, hydraulic system characteristics, and other design variables are 

determined by the torque/speed characteristic s of the engine, and any major 

changes in these characteristic s may involve major expense. 

6-8 
P.96 

Unlike passenger cars, which undergo major design changes every few 

years, farm equipment designs have a rathe r long lif e cycle . The economic lif e 

of a tractor or combine design is of the orde r of ten years, afte r which the 

unit wil l be completely re-engineered and re-tooled . At any given time, some 

portio n of a manufacturer's product lin e is undergoing this re-engineering, so 

tha t each manufacturer typicall y brings out some new equipment designs each 

year. 

To avoid undue financia l and engineering burden on the industry , i t 

would be desirabl e t o incorporat e any major changes required for emissions 

contro l in new models as they ar e redesigned, rathe r than imposing a singl e 

requirement across the board. One approach t o implementing this requirement 

would be through an averaging, trading , and banking arrangement, such as is now 

being considered for heavy-duty truck engines. Beginning with some interim 

emissions control leve l which could be achieved without significan t externa l 

changes t o the engine , the required corporate average emissions levels could be 

reduced each year unti l they reached the ultimat e control levels desired . In 

this way, stringen t emission controls could be designed int o new models as they 

a r e released . 

Estimates of the achievable intermediate-term and long-term (advanced 

technology) corporat e average emission control levels for agricultura l engines 

ar e shown in Table 6-3. Two sets of standards ar e presented: one based on a 

steady-stat e test cycle , and the othe r on a test cycle including transien t 

operation . The former would be applicabl e to combines, windrowers, large 

tractors, and othe r equipment operated primaril y in steady-stat e conditions. 

The latte r would apply to loaders, and possibl y to small utilit y tractors. The 

major difference s between these two test cycles ar e in the PM and HC standards 

achievable ; achievabl e NO emissions ar e littl e affected by transien t operating 

conditions. 

6-9 
P.97 

TABLE 6-3 . ESTIMATED ACHIEVABLE EMISSIONS CONTROL STANDARDS 

TOR DIESEL ENGINES USED IN FARM EQUIPMENT 

Emission s 

Limit 

(g/BHP-hr) 

Equivalen t 

Emissio n 

Facto r 

(lb/100 0 gal. ) 

STEADY-STATE TEST CYCLE 

Intermediat e Contro l Leve l 

NOx 

HC 

PM 

8.00 

0.50 

0.50 

317 

20 

20 

Advanced Technology 

NOx 

HC 

PM 

6.0 0 

0.2 0 

0.15 ] 

238 

8 

6 

TRANSIENT TEST CYCLE 

Intermed 

NOx 

HC 

PM 

Advanced 

NOx 

HC 

PM 

Late Control 

Technology 

Level 

8.0 0 

1.00 

0.8 0 

6.0 0 

0.3 0 

0.15 1 

317 

40 

32 

238 

12 

6 

Source : 

1 

Radian estimates. 

Due t o hig h loa d factors , th e abilit y of farm equipment t o meet th e 0. 1 

g/BHP-hr standar d establishe d fo r highway truck s is questionable . We have 

used a more conservativ e estimate . 

6-10 
As with the previous sections, the reader is warned tha t these are 

engineering estimate s only, based on very limited data , and intended only to 

indicat e the potentia l benefits of regulatio n in this area . Additional 

research to confirm these estimate s would be essentia l before these or any 

othe r emission standards were incorporated into law. 

Near-term emissions control technologies applicabl e t o agricultura l 

equipment include : retarded injection timing, increased injectio n pressures, 

improvements in ai r flow and combustion chamber geometry, and simila r engine 

optimization measures. In addition , turbocharging would be feasibl e in many 

(but by no means all ) equipment models which ar e currentl y using naturally -

aspirate d engines. Addition of low-temperature, separat e circui t aftercoolin g 

would als o be possibl e for some existin g turbocharged or turbocharged/aftercooled engines, but again, not al l of them. It should be noted tha t al l of 

thes e step s would involve some economic waste , as the vehicl e drivetrai n would 

be unable , in most cases, to absorb the increased power output availabl e with 

turbocharging and/or aftercooling . This would requir e tha t the engine be 

derated to match its previous power level . 

Other near-term technologies applicabl e t o agricultura l engines 

include exhaust gas recirculatio n (EGR) and/or indirec t injectio n in the small 

Group 4 engines used for utilit y tractors and compact loaders, and possibly in 

higher-powered, low usage engines such as those in combines. EGR is unlikel y 

to see much applicatio n in large tractors, due t o it s adverse effects on engine 

wear and durability . Trap-oxidizers would also be applicabl e in application s 

such as combines, where the high and predictabl e engine load would eliminat e 

regeneratio n problems. 

Advanced emission control technologies, which could be designed int o 

new equipment models as they ar e produced, include turbocharging with 

moderately low-temperature aftercoolin g in most engines, electroni c injectio n 

timing and governor control, furthe r optimization of combustion chamber, 

airflow, and injectio n characteristics, reduced oi l consumption, and trap -

6-11 
P.99 

oxidizers with precious-metal catalysts for HC control . These last would 

requir e the use of low-sulfur fuel, but EPA is presentl y considering mandating 

this in any event. Due to the relativel y high load factors experienced, 

trap-oxidize r regeneration would be much less of a problem in agricultura l 

application s than in on-highway' trucks. For the same reason, however, 

formation of particulat e sulfate s by the catalyst would be more of a problem. 

These considerations ar e reflecte d in the estimate s shown in Table 6-3. 

Because of the limited space availabl e for heat exchangers and the 

adverse operating conditions imposed by fiel d work, air-to-ai r hea t exchangers 

would be infeasibl e for most agricultura l machines. These same conditions 

would limit the siz e and potentia l effectiveness of separate-circui t 

aftercoolers or othe r low-temperature aftercoolin g techniques. For these 

reasons, th e degree of NO reduction achievabl e in farm equipment would be less 

than tha t which could be achieved in on-highway trucks or marine engines. This 

is reflecte d in the higher NO standards shown in Table 6-3 . 

x 

6.6 Cost-Effectiveness Analysis 

Table 6-4 shows some extremely rough calculation s of the costs and 

cost-effectiveness of controllin g emissions to the "intermediate " leve l shown 

in Table 6-3 . Due t o the uncertaint y of costs and technology involved in 

reaching the "advanced technology" level , no meaningful cost-effectiveness 

estimate s for tha t control leve l were possible . 

Cost-effectiveness estimate s ar e presented for thre e differen t types 

of agricultura l equipment: a large four-wheel drive tractor, a small utilit y 

tractor, and a combine. Emission controls assumed for the large tracto r 

include retarded timing, increased injectio n pressure , and a low-temperature 

aftercooler, plus combustion chamber optimization . This technology was assumed 

t o be adapted from on-highway version s of the same engine. For the small 

tractor, retarded injectio n timing retardation , combustion chamber and airflow 

optimization, and moderate EGR were assumed. For the combine engine, we 

assumed the use of a commercially-available truck engine ratin g rathe r than the 

off-highway versio n of the engine, with a corresponding increas e in cost. 

6-12 
p.1 

TABLE 6-4 . ESTIMATED COST-EFFECTIVENESS OF EMISSIONS CONTROL 

FOR DIESEL ENGINES USED IN FARM EQUIPMENT 

Larg e 4WD 

Tracto r 

Small 

Tracto r Combine 

COST OF EMISSION CONTROLS 

Engine Horsepower 

Initial Cost of Controls 

Engine Life (yrs) 

Amortized Cost/year @ 10% 

Fuel Cons. Increase 

Annual Fuel Cons. (Gal) 

Baseline 

With controls 

Added Fue l Cost @ $0.80/ga l 

Addi. Ann. Maintenanc e 

Annualize d Contro l Cost Pe r Unit 

EMISSIONS 

227 56 

$1,500 

15 

$197 

$300 

15 

$39 

2% 

4,30 0 

4.38 6 

$69 

$100 

$306 

5% 

220 

231 

$9 

$30 

$58 

136 

$500 

15 

$66 

5% 

700 

735 

$28 

$50 

$104 

Emissio n Factors 

Baselin e 

NOx 

HC 

PM 

With Controls 

NOx 

HC 

PM 

Annual Emission s 

Baselin e 

NOx 

HC 

PM 

With Controls 

NOx 

HC 

PM 

(lb/100 0 

(lb s pe r 

Emission s Reductio n 

NOx 

HC 

PM 

Cost-Effectiveness 

NOx + HC 

PM 

(lb s 

($/to n 

g a l 

u n i 

per 

) 

.) 

t pe r yes 

unit per 

435 

35 

32 

317 

20 

20 

r) 

1.871 

151 

138 

1.390 

88 

88 

year) 

480 

63 

50 

$845 

$3,067 

$2 

$7 

434 

75 

51 

317 

40 

32 

95 

17 

11 

73 

9 

7 

22 

7 

A 

,960 

,607 

530 

86 

60 

317 

20 

20 

371 

60 

42 

233 

15 

15 

138 

46 

27 

$848 

$1,900 

6-13 
The cost-effectiveness of emissions control for agricultural 

equipment was calculated by allocating (more or less arbitrarily ) 75 percent of 

the control cost to reducing NO and HC emissions, and the remaining 25 percent 

to reducing PM. The resulting cost-effectiveness values of $845 to $3,000 per 

ton of NO plus HC, and $1,900 to $7,600 per ton of diesel PM are in the 

low-to-in id die portion of the cost range for other emissions control strategie s 

that have been promulgated to date. The extent to which these strategies are 

truly comparable is debatable, however, since the major effect of emission 

controls on agricultural equipment would be to reduce emissions in rural areas, 

whereas most other emission control strategie s are aimed at urban sources. 

6-14 
P.3 

RADIAN 

7.0 CONSTRUCTION AND INDUSTRIAL EQUIPMENT 

Construction equipment includes earthmoving and relate d machinery 

such as bulldozers, graders, scrapers, loaders, cranes, backhoes, and 

off-highway trucks. Industria l equipment such as front-end loaders and 

industria l tractors is also included in this category, as ar e specialize d 

mining and logging machines such as log skidders. 

7.1 Engine Characteristics and Operating Conditions 

Diesel engines used in construction and industrial equipment (CIE) 

range from less than 40 HP for forklifts and small loaders to more than 800 HP 

for the largest earthmoving machines and off-highway trucks. Most CIE engines 

are relatively small, naturally-aspirated, moderate-speed engines classed in 

Groups 2 and 4. Many of these are generally specially designed for their 

applications, or adapted from engines used in small agricultural tractors. The 

larger engines used in large earthmoving and similar machinery are less 

numerous, but—due to their high power output and greater utilization—account 

for a significant fraction of the tota l emissions from this category. These 

engines are classed in Groups 2 and 3, and are often adapted from truck engine 

designs (or vice versa). Many of these larger engines use turbocharging and 

(sometimes) intercooling to increase their power output. 

Usage patterns in construction and industrial equipment engines are 

as varied as the equipment types themselves. Hydraulic pumps to power the 

booms, lifts, buckets, blades, and other implements are' a large part of the 

engine load in most types of construction and industrial equipment, and in some 

cases (e.g. hydrostatically driven crawlers) they are nearly the entir e load. 

Some cranes and large earthmoving machines use diesel-electri c systems like 

those in locomotives. In most construction equipment, however, a large part of 

the engine power requirement is for moving the machine, through a direct 

mechanical linkage with the wheels or tracks. 

7-1 
Hydrostati c and diesel-electri c drive systems allow the engine to 

maintain a relativel y constant speed, although the engine torque required a t 

tha t speed may fluctuate . Direct mechanical drive , on the othe r hand, imposes 

large transien t changes in speed and load on the engine . The need t o generate 

ful l or near-ful l engine torque a t low engine speeds in many operating cycles 

leads to high transien t smoke, and probably high particulat e emissions as well. 

Diese l engines in construction machinery must operat e in a bruta l 

physica l environment. This is especiall y tru e of engines in mechanical-drive 

applications, where shock and vibratio n loads may be transmitted through the 

drivetrai n t o the engine . Reliabilit y is als o very important—failur e of a few 

larg e machines could seriousl y disrupt a constructio n schedule . This imposes 

stringen t requirements for robustness and reliabilit y on the engine . To be 

commercially feasible , any emission controls would have t o be similarl y robust 

and reliable . 

7.2 Current Emission Factors 

The best data on emission factors for constructio n and industria l 

equipment ar e contained in a report to the Californi a Air Resources Board by 

Environmental Research and Technology (ERT) (1982). This report was sponsored 

by the farm equipment, construction equipment, and engine industrie s through 

their respectiv e associations, and include s massive amounts of 

manufacturer-supplied data . Although the report deals specificall y with 

California , the emission factor data contained in i t ar e the best availabl e for 

remainder of the U.S. as well. These data ar e presented in Table 7-1 . 

As discussed in Section 6-2, the data in the ERT report suffe r from 

severa l limitations. The most important of thes e is the absence of particulat e 

measurements. As a result , the PM emission factors in Table 7-1 were taken 

from AP-42 (EPA, 1985). EMA's criticism of these emission factors, and our 

response , have already been discussed in Section 6-2. As was als o the case 

with farm equipment, we decided to retai n these factors essentiall y for lack of 

7-2 
TABLE 7-1 . ESTIMATED CURRENT EMISSION FACTORS FOR DIESEL ENGINES 

USED IN CONSTRUCTION AND INDUSTRIAL EQUIPMENT 

P.5 

HCJ 

EMISSION FACTORS (G/BHP-HR) 

COJ NOx 'M2 

Equipment Type 

Track Type Tractor. 90+ HP 

Track Type Tractor 20-89 HP 

Track Type Loader, 90+ HP 

Track Type Loader, 20-89 HP 

Wheel Loader > 2-1/2 cubic yard 

Wheel Loader < 2-1/2 cubic yard. 

Industria l Wheel Tractor 

Skid-Stee r Loader 

Wheel Tractor Scraper 

Off-Highway Truck* 

Motor Grader 

Hydraulic Excavator, All 

Trencher 

Concrete Paver** 

Bituminous Paver 

Rolle r Compactor, Vibratory 

Rolle r Compactor, Stati c 

Crane, Wheel 

Crane, Crawler 

Crane, Hyd., Wheel, 1-Station 

Crane, Hyd., Wheel, Multi-Statio n 

Log Skidder 

Pipe Layer 

Fuel-Weighted Emission Factors 

lb/1000 gal 

g/BHP-hr 

0.37 

1.33 

0.47 

1.80 

0.60 

1.29 

1.76 

1.76 

0.55 

0.37 

0.36 

1.22 

1.10 

1.10 

0.99 • 

1.06 

0.88 

0.59 

0.59 

0.80 

0.68 

0.61 

0.59 

29 

0.74 

1.65 

2.91 

1.56 

3.02 

2.07 

3.26 

7.34 

7.34 

2.45 

2.28 

1.54 

3.18 

4.57 

4.57 

- 5.19 

6.72 

5.33 

4.99 

4.99 

7.80 

3.71 

3.18 

4.99 

117 

2.94 

6.60 

9.63 

7.76 

10.97 

8.31 

9.24 

11.91 

11.91 

7.46 

8.15 

7.14 

11.01 

10.02 

10.02 

11.18 

14.27 

11.84 

12.45 

12.45 

14.69 

12.47 

9.82 

12.45 

360 

9.08 

0.69 

0.66 

0.66 

0.69 

0.81 

0.81 

1.27 

1.27 

0.79 

0.50 

0.63 

0.90 

0.90 

0.90 

0.90 

0.78 

0.78 

0.90 

0.90 

0.90 

0.90 

0.90 

0.90 

31 

0.77 

* Also wheel dozer, pavement cold planer. 

**Also generators, pumps, compressors 

Sources: 

1. ERT, 1982. 

2EPA, AP-42, 1985. 

7-3 
P.6 

any more applicabl e data . As the PM factors used for construction equipment 

a r e generall y lower than those used in farm equipment (reflectin g the more 

modern, larger, and cleaner engines tested) , they may be considered less 

objectionabl e as a result . Research to obtain more recent and applicabl e 

emissions data for construction equipment is strongl y recommended, however. 

Also shown in Table 7-1 ar e a se t of "fuel-weighted" emission factors 

for construction and industria l equipment. These ar e the weighted averages of 

t h e emission factors for each equipment type , with the weighting proportiona l 

t o the fuel consumed by each type of machine. Fuel consumption estimate s for 

each machine type ar e shown in Table 7-2. 

A major limitatio n of both the ERT dat a and the AP-42 particulat e 

factors is the fact tha t both were based on the old 13-mode steady-stat e test 

cycle , and thus do not account for any transien t effects. Since most 

construction equipment operation involves a highly transien t duty cycle , this 

is a much greate r problem for constructio n and industria l equipment than for 

farm equipment. Many construction equipment operating cycles requir e full or 

near-ful l engine torque a t low engine speeds—a situatio n which can produce 

very high particulat e emissions. The frequent puffs of black smoke emitted by 

many constructio n machines operated on such cycles ar e testimony to the 

potentia l for high emissions. As a result , the HC and PM emissions factors 

shown in Table 7-1 may significantl y understat e the rea l emissions. Research 

to resolve this issue is recommended. 

7.3 Engine Population and Emission Factor Data 

Population and emission estimate s for constructio n and industria l 

equipment ar e liste d in Table 7-2. The utilizatio n and duty-cycl e data in 

this tabl e were taken from the ERT report to the Californi a Air Resources Board 

(1982). At the time our Task 1 interim report was prepared, no national-leve l 

population dat a were availabl e for constructio n and industria l equipment. As a 

result , nationa l populations were calculated by scalin g up the Californi a 

7-4 
TABLE 7-2 . ESTIMATED POPULATION, FUEL CONSUMPTION AND EMISSIONS FROM 

DIESEL ENGINES USED ON CONSTRUCTION AND INDUSTRIAL EQUIPMENT 

% 

1 Diesel Usage Avg. Load Consumption 

Population (hr/yr) H.P. Factor (1000 gal) HC 

EMISSIONS (TONS/YEAR) 

CO NOx PM 

i 

Equipment Type 

Track Type Tractor, 90+ HP 

Track Type Tractor 20-89 HP 

Track Type Loader, 90+ HP 

Track Type Loader, 20-89 HP 

Wheel Loader > 2-1/2 cubic yard 

Wheel Loader < 2-1/2 cubic yard 

Industrial Wheel Tractor 

Skid-Steer Loader 

Wheel Tractor Scraper 

Off-Highway Truck 

Motor Grader 

Hydraulic Excavator, All 

Trencher 

Concrete Paver 

Bituminous Paver 

Roller Compactor, Vibratory 

Roller Compactor, Static 

Crane, Wheel 

Crane, Crawler 

Crane, Hyd., Wheel, 1-Station 

Crane, Hyd.. Wheel, Multi-Statio n 

Log Skidder 

Pipe Layer 

84.000 

36.000 

36.000 

28.000 

74.000 

56.000 

212.000 

112.000 

16.400 

20.000 

74.000 

63.000 

50,500 

11.300 

12,000 

14,000 

29,000 

38.000 

14.300 

34.700 

6.100 

25.455, 

750^ 

1350 

865 

1175 

850 

1430 

1035 

556 

500 

750 

2940 

1035 

1430 

572 

500 

820 

1085 

850 

760 

1085 

1085 

760 

1450 

1325 

216 

63 

146 

67 

229 

87 

56 

40 

289 

623 

43 

200 

75 

185 

120 

140 

67 

90 

150 

150 

90 

105 

175 

0.41 

0.38 

0.44 

0.50 

0.40 

0.32 

0.38 

0.32 

0.42 

0.28 

0.41 

0.49 

0.49 

0.38 

0.30 

0.25 

0.38 

0.40 

0.25 

0.25 

0.40 

0.53 

0.23 

557.928 

41.416 

150.964 

44.294 

538.506 

89.645 

139,548 

39.822 

82.943 

569.837 

75.016 

490,490 

58.976 

22.066 

19.680 

29.536 

34,866 

57.760 

32,324 

78,436 

9,272 

114,113 

2,222 

4.092 

1.092 

1.407 

1.581 

6.405 

2.292 

4.869 

1.389 

904 

4.180 

535 

11.863 

1.286 

481 

386 

621 

608 

676 

378 

1.244 

125 

1,380 

26 

18.249 

2.389 

4.669 

2.652 

22.098 

5.793 

20.305 

5.794 

4.028 

25.756 

2.290 

30.920 

5.343 

1.999 

2.025 

3.935 

3.684 

5.714 

3.198 

12.128 

682 

7,194 

220 

72,998 

7.906 

23.223 

9.633 

88,711 

16.420 

32.947 

9.402 

12,266 

92.065 

10,618 

107,054 

11.715 

4.383 

4.362 

8,355 

8.184 

14.256 

7.978 

22,842 

2,292 

22.214 

548 

7.654 

538 

1.960 

608 

8.594 

1.431 

3.513 

1.003 

1.297 

5.671 

929 

8.770 

1.055 

395 

352 

456 

538 

1.033 

578 

1.403 

166 

2.040 

40 

TOTAL 1.047.805 

D0E/EIA "Off-Highway" Fue l Cons, 

3.279.66 1 47.820 191.064 590.37 2 50.02 1 

1,616.68 5 23.572 94.184 6

 291,019 6 24.657 6 

Sources: 

Constructio n Equipment Magazine , March-July , 1987, 

Radian estimate s base d on Californi a data . 

3ERT. 1982. 

-Calculate d by assuming fue l consumption of 0. 4 lb/BHP-hr. 

?EIA. 1985. 

"Fuel-weighted " emissio n factors time s DOE/EIA estimate . 
P.8 

populations estimated as a part of the ERT study. This was accomplished by 

dividing the California population by the ratio oJ 1979 California sales to 

1979 U.S.'sales of construction and industrial equipment. 

In comments on our interim report, the Engine Manufacturer's 

Association accepted this general approach, but suggested that the estimated 

populations be adjusted downward to reflect declining sales of construction and 

industrial equipment since 1979 (Young, 1987). Since that time, however, 

Construction Equipment Magazine has published the result of a nationwide survey 

of construction equipment users, including population estimates for nearly all 

major classes of construction equipment (Landers, 1987). These population 

estimates, adapted to fit the classifications used in the ERT report, are the 

ones shown in Table 7-2. Although the equipment classes in this survey were 

not precisely coincident with those in the ERT report, the correspondence was 

close enough in every case to allow a reasonable allocation to be made. 

Several categories shown in Table 7-2 require some additional 

explanation. The Construction Equipment survey estimated the number of backhoe 

loaders, which the ERT report lumped with other, similar machines as 

"industrial wheel tractors". The Construction Equipment estimate of 189,000 

backhoe loaders was arbitrarily increased by 40 percent to reflect the presence 

of other classes of industrial tractors not included in the survey. This was 

then reduced by 20 percent to reflect the assumed fraction of gasoline engines 

in the population. 

The ERT report included no equipment category for skid-steer loaders, 

although these are extremely common small construction machines. We assumed 

that the emission factors and usage patterns for these machines would be 

similar to those for industrial wheel tractors, and further assumed that 80 

percent of the skid-steer loaders reported were diesel powered. These 

estimates are reflected in Table 7-2. In addition, the Construction Equipment 

survey contained no data for log skidders or pipelayers. Population estimates 

for these equipment types were carried over from our Task 1 interim report. 

7-6 
P.9 

Total fuel consumption and pollutan t emissions by construction and 

industrial equipment were calculate d using the same approach as for farm 

equipment, and ar e als o reported in Table 7-2. As this tabl e indicates, no 

one category of construction and industria l equipment is dominant. The four 

largest categorie s ar e track-type tractors, large wheel loaders, hydrauli c 

excavators, and off-highway trucks, but many othe r equipment categorie s ar e 

als o major contributors. 

Table 7-2 als o shows the tota l fuel consumption calculated from the 

ERT data and, for comparison, the tota l fuel consumption for "off-highway" 

equipment estimated by DOE. As the tabl e shows, th e DOE estimat e is 

only about half of the value calculate d from our estimates. Whether this is 

due to an overestimat e on our part (as a resul t of unrealisticall y high load 

factors, usage- estimates, or average horsepower, for instance), or to an 

underestimate on DOE's part is unclear. As a matte r of interest , the emissions 

which would resul t from assuming tha t the DOE value is correct , and scalin g 

back the ERT estimate s proportionally , ar e als o shown. 

7.4 Emissions Test Cycles 

As discussed in Section 7.2 above, the operating cycles of many types 

of construction machinery include large transien t changes in engine speed and 

load. A front-end loader, for instance , cycle s between ful l engine power and 

low-load operation a t least thre e times in the course of a loading cycle , which 

may take only 15-30 seconds to complete. Hydraulic excavators and othe r 

construction machines exhibit simila r large cycli c swings in engine load and 

speed. These often result in high visibl e smoke emissions, and it is likel y 

tha t they cause high PM emissions as well. 

Due to the large number of machine designs and duty cycles, i t would 

be impractica l t o develop an emissions test cycle reflectin g each specifi c 

operating pattern . However, by recording speed and load measurements on a 

large number of engines in differen t types of construction machines, i t might 

be possibl e to develop a "generic " transien t test cycle which would result in 

7-7 
P.10 

adequate control of transient emissions effects over a wide range of cycles. 

An engine certified on this test cycle could then be used in any conjtruction 

machine. 

To allow for the fact that some construction machinery engines (those 

in paving machines, or compressors, for instance) do not experience large 

transient speed and load changes, the regulations might permit a manufacturer 

to certify an engine using a cycle of his own devising, as long as he could 

show that the cycle was representative of operation in a specific equipment 

model or models. The engine would then be limited to use in that type of 

equipment. This would avoid imposing technologies to control transient or low 

speed/high load emissions on engines which do not experience these operating 

conditions. It would also encourage manufacturers to develop equipment designs 

whose power requirements are more compatible with low emissions. 

7.5 Feasibility of Emissions Control 

Most construction and industrial equipment engines are classed in 

Group 2 or Group 4, with some high-powered earthmoving machinery being equipped 

with Group 3 engines. All three of these engine groups are closely related to 

on-highway engines, so that most emission control technologies developed for 

on-highway use should be readily adaptable. As with farm equipment, however, 

the differences in duty cycle, application requirements, and environmental 

conditions between the two types of applications will impose some limitations. 

In particular, the close integration of the engine and the machine as a whole, 

already discussed in relation to farm equipment, is an important consideration 

for construction and industrial equipment as well. 

Like farm machinery, bulldozers, loaders, compactors, and similar 

machines are literally designed around the physical dimensions and operational 

capabilities of the engine, and any change in physical dimensions or torque 

capabilities may require redesign of major portions of the equipment. As with 

farm machinery, the economic life of an equipment design is of the order of ten 

7-8 
P.11 

years, afte r which the unit wil l be completely re-engineered and re-tooled . 

Thus, to avoid undue financia l and engineering burden on the industry, it would 

be desirabl e t o phase in any emission regulation s stringen t enough t o requir e 

significan t engine changes, using an approach such as the averaging, trading , 

and banking arrangement discussed in Section 6.5 . 

Estimates of the achievable intermediate-term and long-term (advanced 

technology) corporat e average emission control levels for construction and 

industria l equipment engines ar e shown in Table 7-3 . These estimates ar e 

identica l t o the estimate s of achievable farm equipment emissions standards in 

Table 6-3 . Two sets of standards ar e presented: one based on a steady-stat e 

test cycle , and the othe r on a test cycle including transien t operation . The 

former would be applicabl e t o pavers, compressor motors, and othe r engines 

operating in more-or-less steady-stat e conditions, while the latte r would 

apply to the great majority of construction equipment types and models. 

As in the previous sections, the reader is warned tha t these ar e 

engineering estimate s only, based on very limited data , and intended only t o 

indicat e the potentia l benefits of regulatio n in this area . Additional 

research to confirm these estimate s would be essentia l before these or any 

othe r emission standards were incorporated into law. 

Near-term emissions control technologie s applicabl e to constructio n 

and industria l equipment ar e identica l to those for farm equipment. These 

include : retarded injectio n timing, increased injectio n pressures, improvements 

in ai r flow and combustion chamber geometry, and simila r engine optimization 

measures. Turbocharging would als o be feasibl e in some equipment models which 

a r e currentl y using naturally-aspirate d engines, and low-temperature, 

separate-circui t aftercoolin g would be possibl e for in some models currentl y 

using turbocharged or turbocharged/aftercooled engines. As with farm 

equipment, these steps would involve some economic waste , as the vehicl e 

drivetrai n would be unable , in most cases, t o absorb the increased power output 

availabl e with turbocharging and/or aftercooling . Other near-term technologies 

7-9 
P.12 

RADIAN 

applicable to construction and industrial equipment include exhaust gas 

recirculation (EGR) and/or indirect injection in the Group 4 engines. 

Advanced emission control technologies, which could be designed into 

new equipment models as they are produced, include turbocharging with 

moderately low-temperature aftercooling, electronic injection timing and 

governor control, and further optimization of combustion chamber, airflow, and 

injection characteristics. Since many construction machines require high 

torque output at low RPM. variable-geometry turbochargers would also be well 

suited both for emissions control and for improving performance. Finally, 

trap-oxidizers with precious-metal catalysts would be well-suited for PM and HC 

control. Due to the relatively high load factors experienced, trap-oxidizer 

regeneration would be much less of a problem in construction equipment than in 

on-highway trucks, and trap-oxidizers have in fact been applied to some 

underground mining machines (Brev et al. , 1987). The high load factors would 

produce a greater problem with particulate sulfate formation due to the 

catalyst, however. necessitating the use of low-sulfur fuel. These 

considerations are reflected in the estimates shown in Table 7-3. 

As with farm equipment, the constraints of physical space and 

operating environment would rule out the use of air-to-air aftercoolers in most 

construction and industrial equipment, and would limit the applicability of 

other low-temperature aftercooling techniques. Thus, the NO reductions 

achievable would be less than those in on-highway truck engines. This is 

reflected in the higher NO standards shown in Table 7-3. 

x 

7.6 Cost-Effectiveness Analysis 

Table 7-4 shows some extremely rough calculations of the costs and 

cost-effectiveness of controlling emissions to the "intermediate" level shown 

in Table 7-3. The uncertainties in the costs and technology involved in 

reaching the "advanced technology" level were such that no meaningful 

cost-effectiveness estimates for that control level were possible. 

7-10 
P.13 

TABLE 7-3 . ESTIMATED ACHIEVABLE EMISSIONS CONTROL STANDARDS FOR DIESEL 

ENGINES USED IN CONSTRUCTION AND INDUSTRIAL EQUIPMENT 

Emission s 

Limit 

(g/BHP-hr) 

Equivalent 

Emission 

Factor 

(lb/1000 gal.) 

STEADY-STATE TEST CYCLE 

Intermediate Control Level 

NOx 

HC 

PM 

8.00 

0.50 

0.50 

317 

20 

20 

Advanced Technology 

NOx 

HC 

PM 

6.0 0 

0.2 0 

0.15 1 

238 

8 

6 

TRANSIENT TEST CYCLE 

Intermediate Control Level 

NOx 

HC 

PM 

Advanced Technology 

NOx 

HC 

PM 

8 

1 

0 

6 

0 

00 

.00 

80 

00 

30 

0.15 ' 

317 

40 

32 

238 

12 

6 

Source : 

1 

Radian estimates. 

Due t o hig h loa d factors , th e abilit y of constructio n equipment t o achiev e 

t h e 0.10 g/BHP-hr standar d establishe d fo r highway truck s is questionable . 

We have used a more conservativ e estimate . 

7-11 
P.14 

Cost-effectiveness estimate s ar e presented for thre e differen t types 

of construction equipment, a hydrauli c excavator, an industria l utilit y 

tractor, and a concret e paver. The excavator and tracto r represent transien t 

operation a t high and low power levels, respectively , while the concrete paver 

is representativ e of steady-stat e operation. Except for the transien t 

operating cycle experienced by the hydrauli c excavator, these machines exhibit 

very simila r power levels and operating characteristic s to the thre e 

agricultura l equipment types analyzed in Table 6-4. 

Emission controls assumed for the hydraulic excavator included 

retarded timing. increased injectio n pressure , and a separate-circui t 

or air-ai r aftercooler, plus combustion chamber optimization. This technology 

was assumed t o be adaptable from simila r on-highway engines. For the small 

tractor , retarded injectio n timing, combustion chamber and airflow optimization , and moderate EGR were assumed. These control techniques (and indeed, the 

tracto r itself ) ar e identica l t o those assumed for the small agricultura l 

tracto r in Table 6-4. For the concrete paver engine , as with the combine, we 

assumed the use of a commercially-available truck engine ratin g rathe r than the 

off-highway version of the engine . 

The cost-effectiveness of emissions control for construction 

equipment was calculate d in the same way as for farm equipment. We allocated 

75 percent of the control cost, more or less arbitrarily , to reducing NO and 

HC emissions, and the remaining 25 percent t o PM. The resultin g 

cost-effectiveness values of $75 0 t o $2,050 per ton of NO plus HC. and $4,000 

to $9,000 per ton for PM ar e als o in the low-to-middle portio n of the cost 

range for othe r emissions control strategies, and ar e comparable to those for 

farm equipment. Unlike emission reductions from farm equipment, however, these 

reductions would occur primarily in urban areas. These cost-effectiveness 

estimate s ar e thus directl y comparable to those of othe r urban-oriented control 

strategies. 

7-12 
P.15 

RADIAN 

TABLE 7-4 . ESTIMATED COST-EFFECTIVENESS OF EMISSIONS CONTROL 

FOR DIESEL ENGINES USED IN CONSTRUCTION EQUIPMENT 

Hydraulic 

Excavator 

lndust. 

Wheel 

Tractor 

Concrete 

Paver 

COST OF EMISSION CONTROLS 

Engine Horsepower 

Initial Cost of Controls 

Engine Life (yrs) 

Amortized Cost/year @ 10% 

Fuel Cons. Increase 

Annual Fuel Cons. (Gal) 

Baseline 

With controls 

Added Fue l Cost @ $0.80/ga l 

Addi. Ann. Maintenanc e 

Annualized Control Cost 

Per Unit 

200 56 

$1,200 

10 

$195 

$300 

10 

$49 

2% 

7.800 

7.95 6 

$125 

$150 

$470 

5% 

660 

693 

$26 

$40 

$115 

185 

$600 

10 

$98 

5% 

2.000 

2.100 

$80 

$60 

$238 

EMISSIONS 

Emissio n Factors 

Baselin e 

NOx 

HC 

PM 

With Controls 

NOx 

HC 

PM 

Annual Emission s 

Baselin e 

NOx 

HC 

PM 

With Controls 

NOx 

HC 

PM 

Emission s Reduct 

NOx 

HC 

PM 

(lb/100 0 

(lb s pe r 

ion (lb s 

Cost-Effectiveness ($/to n 

NOx + HC 

PM 

gal. ) 

unit per 

pe r unit 

) 

437 

48 

36 

317 

40 

32 

year) 

pe r 

3,409 

374 

281 

2,52 2 

318 

255 

year) 

887 

56 

26 

$748 

$8,969 

472 

70 

50 

317 

40 

32 

312 

46 

33 

220 

28 

22 

92 

18 

11 

$1,567 

$5,323 

$2 

$3 

397 

4A 

36 

317 

20 

20 

794 

88 

72 

666 

42 

42 

128 

46 

30 

.04 5 

.961 

7-13 
P.16 

It is worth noting that the cost per ton of particulate emissions 

eliminateu in Table 7-4 may be greatly overestimated for the excavator and 

industrial tractor, due to the possible substantial under-estimate of the 

emissions reduction. This is due to the fact that the baseline emissions were 

calculated from the steady-state PM emission factors developed by Hare et al. , 

(1975), while the "controlled" emission level is based on engine capabilities 

under transient conditions. Since uncontrolled transient emissions are often 

much higher than those in steady state , the emissions benefits of the 

intermediate-level standards may have been significantly underestimated. 

7-14 
P.17 

8.0 MOBILE REFRIGERATION UNITS 

Small, engine-powere d refrigeratio n units ar e used t o provid e coolin g 

f o r refrigerate d trailers , shippin g containers, truc k bodies, and rai l cars. 

Thes e unit s ar e overwhelmingly diese l powered, due t o th e high efficienc y of 

t h e diese l engin e and th e read y availabilit y of it s fuel. Although they ar e 

individuall y small i n power output, th e larg e number of refrigeratio n units in 

u s e and th e larg e number of operatin g hours pe r unit make them a 

not-inconsiderabl e contributo r t o tota l diese l emissions. 

Mobile refrigeratio n units have receive d relativel y littl e study , 

compared t o th e othe r equipment categorie s considere d i n this report, and th e 

funds availabl e fo r this preliminar y stud y di d no t permit an in-dept h 

investigation . As a result, th e estimate s presente d her e are - even more 

uncertai n than thos e in th e previou s sections. More extensiv e investigation , 

includin g actua l emission s testin g of a sample of refrigeratio n units , is 

strongl y recommended. 

8.1 Engine Characteristic s and Operating Conditions 

Diesel engines used for mobile refrigeratio n ar e typicall y small, 

naturally-aspirated , high-speed engines classed in Group 4. Power rating s 

range from less than 10 H.P. up to around 70 HP for some truck units, while 

railca r refrigeratio n units ar e reported to have an average of 88 H.P. Both 

direct-injecte d (DI) and indirect-injecte d (IDI) engines ar e used, but the 

market trend is toward increased use of DI engines. This is due t o the greate r 

fuel efficiency , lower heat losses, and easie r cold startin g of the DI engines. 

Diesel engines in mobile refrigeratio n units typicall y run 

continuously while the unit is in use, being shut off only when the car or 

traile r wil l not be used for an extended period. In most units, the engine and 

compressor ar e sized t o deal with the maximum anticipate d cooling load. This 

5-1 
P.18 

RADIAN 

may include cooling down a just-loade d cargo, as well as keeping i t cool under 

the most extreme climati c conditions expected. As a result , they ar e 

substantiall y oversized for normal cooling requirements. Most mobile 

refrigeratio n units handle this by cycling between full-power operation with 

t h e compressor running and lettin g the engine idl e when the compressor is not 

needed. Thus, depending on the cooling requirements of the load, the engine 

often spends the grea t bulk it s time idling . 

To reduce fuel consumption, some newer mobile refrigeratio n units ar e 

incorporatin g a more complex control strategy—fo r instance , using full-speed 

operatio n for rapid cooldown when required, and a slower, more fuel-efficien t 

speed for keep-cool operation . Systems allowing automatic shutdown and restart 

of the engine when i t is needed ar e als o available . We were unable to 

determine the degree of market penetration of these systems, but i t is believed 

t o be relativel y small. 

8.2 Current Emission Factors 

Emissions data for engines used in mobile refrigeratio n are 

unavailable . Table 8-1 shows some rough estimate s of these factors, based on 

dat a for simila r engines in other applications. For railca r refrigeratio n 

units, the most common engine is the DDA 2-71. The emission factors shown ar e 

based on a 6V-71 engine (Hare e t al. , 1975). This engine has more cylinders, 

but is otherwise simila r to the 2-71 in combustion technology. The KO 

x 

emissions for this engine reported by Hare, e t al . have been adjusted downward 

somewhat, and the PM emissions adjusted upward to reflec t the effects of 

wear in the injecto r linkage and changes in engine technology since 1975. 

Even less information is availabl e on emissions from engines in truck 

and containe r refrigeratio n units. The emission factors shown in Table 8-1 for 

thes e units ar e Radian estimates, based on typica l emissions performance for 

small DI and IDI diese l engines, and may well be grossly wrong. It is likel y 

tha t thes e emissions values vary greatl y from manufacturer t o manufacturer, so 

even a few emissions data points would not help greatl y to improve the 

estimates. 

8-2 
P.19 

— ^ | 

TABLE 8-1 . ESTIMATED CURRENT EMISSION FACTORS FOR DIESEL 

ENGINES USED FOR MOBILE REFRIGERATION 

EMISSION FACTORS 

g/BHP-hr lb/100 0 gal, 

Railroa d Car Units 

HC 1. 0 40 

CO 4. 0 159 

NOx 16.0 634 

PM 0. 4 16 

2 

Truck/Container Units 

HC 1.2 48 

CO 5.0 198 

NOx 8.0 317 

PM 0.6 24 

Sources: 

Radian estimates based on DDA 2-71 engine. 

2 

Radian estimates based on typical small DI and IDI engines. 

8-3 
P.20 

8.3 Engine Population and Emissions Inventory 

Estimated nationwide population, fuel consumption, and emissions for 

diese l engines used in mobile refrigeratio n units ar e shown in Table 8-2. 

Estimates of the nationa l population of truck and containe r refrigeratio n units 

were obtained by summing annual sale s data (obtained from Refrigerated 

Transporte r magazine) over an estimated 15 yea r useful life . The number of 

refrigerate d trai n units was taken from statistic s of the Association of 

American Railroads (1986). The average horsepower, load factors, and 

hours-of-operation shown for these units ar e Radian estimates, based on limited 

dat a and conversations with persons involved in the industry . 

Like the industrie s which use them, mobile refrigeratio n units should 

tend t o be concentrated in urban areas and their immediate surroundings, as 

these ar e the major termini for refrigerate d railcars and truck trailers. The 

degree of urban operation for these units is probably simila r t o tha t of the 

vehicle s which transport them: train s and on-highway trucks. 

8.4 Emissions Test Cycle 

Emissions from a mobile refrigeratio n unit ar e affected by the 

overall design of the unit , including the compressor, heat-exchangers, and 

control system as well as the engine. An appropriat e test procedure should 

therefor e measure emissions against the useful output of the system: i.e . BTU 

of cooling supplied under specified conditions (which should include cycli c 

operation). This would resul t in emissions credit for shutdown/restart rathe r 

than continuous idle , use of more efficien t compressors, and othe r design 

feature s which would reduce emissions in the rea l world. Unfortunately, 

sufficien t dat a t o specify such a test cycle were unavailabl e for this 

preliminary study. Thus, the discussion of achievable emissions standards in 

Section 8.5 is limited t o g/BHP-hr numbers only. 

8-4 
TABLE 8-2. ESTIMATED NATIONWIDE POPULATION. FUEL CONSUMPTION. AND _. 0| 

EMISSIONS FROM DIESEL ENGINES USED FOR MOBILE REFRIGERATION 

n 

% 

• ' , 

Application 

Train 

Truck/Container 

Est. 

Pop. 

30.OOO1 

173.OOO2 

Avg. 

HP 

88 

27 

3 

Usage 

(hr/yr) 

8000 

5000 

T A3 

Load Factor 

0.2 

0.2 

Fuel . 

Cons. 

(1000 Gal) 

234.667 

259.500 

HC 

4.693 

6,228 

Total Emissions (Tons/Yr) 

CO 

18.656 

25.691 

NOx 

74.389 

41,131 

PM * * 

1.877 

3.114 

TOTAL 203.000 494.167 10.921 44.347 115.520 4.991 

g. Sources: 

i i 

*-" Association of American Railroads, 1986. 

2 Calculated from annual sale s data , assuming 15-year life , 

3 Radian estimate . 

Calculated assuming fuel consumption of 0.4 lb/BHP-hr. 

, TJ 

3 r° 
P.22 

8.5 Feasibilit y of Emissions Control 

Emission control techniques applicabl e t o mobile refrigeratio n 

engines in the intermediat e term include indirec t injection or optimized 

direct-injectio n combustion systems, retarded injectio n timing, combustion 

chamber optimization, and exhaust gas recirculation . The emissions standards 

estimated t o be achievable through these techniques ar e shown in Table 8-3. 

These standards ar e based on the 1988 on-highway truck standards (adjusted t o 

reflec t steady-stat e operation), and ar e probably somewhat conservative . Many 

existin g IDI engines can undershoot these standards by a considerable margin. 

Wade and co-workers (1985) have als o demonstrated the capabilit y t o control 

small DI engine emissions t o levels well below the values shown. As before, 

however, the reader is cautioned tha t these estimate s ar e preliminary only, and 

tha t additiona l research to confirm these estimate s would be needed before 

these or any othe r emission standards were incorporated into law. 

The major advanced emission control technologies applicabl e t o mobile 

refrigeratio n engines would be catalyti c trap-oxidizers, in combination with 

EGR and an electroni c engine control system. The figures for "advanced 

technology" in Table 8-3 reflec t these technologies. The major problem facing 

trap-oxidize r development in motor vehicle s is the unpredictabilit y of the 

operating conditions, which complicates regeneration system design. Since 

the engine in a mobile refrigeratio n unit is under complete independent 

control , the regeneration system could be simple. Successful trap-oxidize r 

operatio n in a simila r applicatio n (a diesel-powered heat-pump) was 

demonstrated some years ago by Volkswagen. 

8.6 Cost-Effectiveness Analysis 

Table 8-4 shows some very rough estimate s of th e cost-effectiveness 

of the "intermediate " emissions control levels in mobile refrigeratio n units 

for railca r and truck/containe r service . The control costs shown assume the 

applicatio n of engine modifications, retarded timing, and eithe r EGR or 

8-6 
P.23 

TABLE 8-3. ESTIMATED ACHIEVABLE EMISSIONS CONTROL STANDARDS 

POR DIESEL ENGINES USED IN MOBILE REFRIGERATION 

Emissions 

Limit 

(g/BHP-hr) 

Equivalent 

Emission 

Factor 

(lb/1000 gal.) 

Intermediate Control Level 

NOx 

HC 

PM 

6.00 

1.00 

0.50 

238 

40 

20 

Advanced Technology 

NOx 

HC 

PM 

5.00 

0.30 

0.10 

198 

12 

4 

Source: Radian estimates, 

8-7 
P.24 

TABLE 8-4 . ESTIMATED COST-EFFECTIVENESS OF EMISSIONS CONTROL 

POR DIESEL ENGINES USED IN MOBILE REFRIGERATION 

Train car 

Truck and 

Container 

COST OF EMISSION CONTROLS 

Engine Horsepower 

Initial Cost of Controls 

Engine Life (yrs) 

Amortized Cost/year @ 10% 

Fuel Cons. Increase 

Annual Fuel Cons. (Gal) 

Baseline 

With controls 

Added Fue l Cost @ $0.80/ga l 

Addi. Ann. Maintenanc e 

Annualize d Contro l Cost Pe r Unit 

EMISSIONS 

88 

$600 

15 

$ 79 

3% 

7.800 

8.034 

$187 

$ 80 

$346 

Emissio n Factors 

Baselin e 

NOx 

HC 

PM 

With Controls 

NOx 

HC 

PM 

Annual Emission s 

Baselin e 

NOx 

HC 

PM 

With Controls 

NOx 

HC 

PM 

(lb/100 0 

(lb s pe r 

Emission s Reductio n (lb s 

NOx 

HC 

PM 

Cost-Effectiveness ($/to n 

NOx + HC 

g a l 

u n i 

per 

) 

.) 

t per 

unit 

yea 

pe r 

r) 

year) 

634 

40 

16 

238 

40 

20 

4.94 5 

312 

125 

1.912 

321 

161 

3.033 

(9) 

(36) 

$229 

27 

$400 

15 

$ 53 

2% 

1.500 

1,530 

$ 24 

$ 40 

$117 

317 

48 

24 

238 

40 

20 

47 6 

72 

36 

364 

61 

31 

U l 

11 

5 

$1,909 

8-8 
P.25 

turbocharging and aftercooling for emission control purposes. These cost 

estimates are highly uncertain—much more investigation of the technology and 

operating constraints would be required to develop reliable cost estimates for 

these engines. 

A similar level of uncertainty surrounds the emission reduction 

estimates. Due to the absence of< data on current emissions, the emission 

reductions available are uncertain, as is the cost-effectiveness of control. 

As Table 8-4 indicates, however, emissions control for these engines could 

potentially be highly cost-effective, with a cost per ton of HC and NO removed 

ranging from $229 to $1,909. This broad range suggests the level of 

uncertainty in the data. Further research to arrive at a more precise 

quantification of this potential is recommended. 

8-9 
9 . 0 SUMMARY, CONCLUSIONS AND RECOMMENDATIONS 

This sectio n pulls togethe r and summarizes th e result s detaile d in 

t h e precedin g fiv e sections, and presents our conclusion s and recommendations. 

9.1 Summary and Conclusions 

As the preceding five section s have shown, tota l pollutan t emissions 

from off-highway diese l engines ar e large both in absolut e terms and in 

proportion t o their tota l numbers, power output, and fuel consumption. Table 

9-1 summarizes the estimated population, annual fuel consumption, and emissions 

for the five classe s of off-highway diese l engines considered in this report . 

Off-highway diese l engines ar e estimated t o produce about 2.75 millio n tons of 

NO per year, 187,000 tons of particulat e matter, 232,000 tons of unburned HC, 

and 959,000 tons of CO. These values are.abou t 12.6 percent, 2.4 percent, one 

percent, and 1.25 percent, respectively , of estimated tota l emissions of these 

pollutants from al l sources nationwide (EPA, 1986). 

More significan t than the off-highway diese l contributio n to the 

tota l emissions inventory is the off-highway contributio n t o the tota l for al l 

mobile diese l engines, both on and off-highway. Table 9-2 shows this 

calculation . As this tabl e indicates, off-highway diese l engines ar e 

responsibl e for a disproportionat e fractio n of the total : accounting for 56 

percent of the NO emissions, 57 percent of CO emissions, and 48 percent of HC 

emissions from mobile diese l engines, but only 41 percent of the diese l fuel 

burned. Their contributio n t o PM emissions is less than proportionate , 

however, a t 36.5 percent of the total . Due t o limited data , the numbers in 

Table 9-2 ar e somewhat crude, but the conclusion is inescapable : off-highway 

diese l engines ar e currentl y an important source of emissions, comparable in 

magnitude to on-highway diesels. 

Diesel engines in on-highway vehicle s have been subject to emission 

regulation s for many years, and have recentl y received a great deal of 

9 - 1 
vO 

I 

ro 

TABLE 9-1 . ESTIMATED NATIONWIDE POPULATION AND EMISSIONS FROM DIESEL ENGINES 

USED IN OFF-HIGHWAY APPLICATIONS 

Tota l Fue l 

No. of Horsepower Consumption 

Engine s (1.000s) (1,000 gal) 

Emission s (tons/yr ) 

HC CO NO 

Locomotive s 

Medium Speed 

Percen t of Nationwid e 

Marine Vessels 

High Speed 

Medium Speed 

Tota l 

Percen t of Nationwid e 

Farm Equipment 

26,10 5 

438,00 0 

5.000 

443.000 

61.11 1 

45.47 1 

11.17 3 

56.64 4 

High Speed 

Percent of Nationwide 

3.868.019 

Construction and Industrial Equipment 

332.13 9 

High Speed 1.047.805 

Percen t of Nationwid e 

Mobil e Refrigeratio n 

High Speed 203.000 

Percen t of Nationwid e 

124.056 

9.51 8 

915.67 1 

917.607 

1.833.27 8 

14,65 1 54.48 2 

18.81 1 85.79 6 

33.46 2 140,278 

0.14% 0.18% 

199.616 

244.54 2 

444.15 8 

2.05% 

PM 

3.409.47 6 30,99 9 308.55 8 901.64 5 37.04 1 

0.13% 0.40% 4.16% 0.48% 

10.98 8 

9.17 6 

20.16 4 

0.26% 

3.021.56 1 108.603 274.669 688.87 4 75.10 3 

0.46% 0.36% 3.17% 0.97% 

3.279.66 1 47.82 0 191.064 590.372 50.02 1 

0.20% 0.25% 2.72% 0.65% 

494.16 7 10.92 1 44.34 7 115.520 4.99 1 

0.05% 0.06% 0.53% 0.06% 

% i 

TOTALS 

High Speed 5.556.82 4 511.18 4 

Medium Speed 31,10 5 72,284 

Tota l 5.587.92 9 583.46 8 

Percen t of Nationwide 

7.711.06 0 181.99 5 564.562 1.594.382 141.103 

4.327.08 3 49.81 0 394.354 1.146.187 46.217 

12.038.14 3 231.80 5 958.91 6 2.740,56 9 187.320 

0.98% 1.25% 12.63% 2.43% 

Percen t of nationwid e emission s inventor y for tha t pollutan t base d on EPA (1986). 
TABLE 9-2 . COMPARISON OF NATIONWIDE FUEL CONSUMPTION AND EMISSIONS 

OFF-HIGHWAY VS. ON-HIGHWAY DIESELS 

Fuel 

Consumption Emissions (tons/yr) 

(1.000 gal) HC CO NO PM 

x 

Off-Highway Diesels (mid-1980s)1 

Locomotives 3,409,476 

Marine Vessels 1,833.278 

Farm Equipment 3.021.561 

Const./Ind. Equipt. 3,279,661 

Mobile Refrigeration 494,167 10.921 

30.999 

33.462 

108.603 

47.820 

10.921 

308.558 

140.278 

274,669 

191,064 

44,347 

901,645 

444,158 

688,874 

590,372 

115,520 • 

37,041 

20,164 

75,103 

50,021 

4,991 

Total Off-Highway 12,038,143 231.805 958,916 2,740,569 187.320 

2 

On-Highway-Diesels (calendar 1984) 

Heavy-Duty Vehicles NA 242,290 693,832 2,136.563 297.357 

Light-Duty Vehicles NA 8.820 28.634 44,052 28.634 

Total On-Highway 17,279.650 251.110 722,466 2,180.615 325.991 

Total: All Mobile 29,317,793 482,915 1,681,382 4,921,184 513.311 

Diesel Engines 

Off-Highway as 41.1% 48.0% 57.0% 55.7% 36.5% 

Percent of All 

Mobile Diesels 

Source: Radian estimates, 

2

Source: EPA (1986). 

9-3 
P.29 

regulator y attention , which wil l lead t o stil l lower emissions in the future . 

Off-highway engines, since chey do not fal l under EPA's statutor y authority , 

have not been regulated . For this reason, pollutan t emissions per unit of 

work produced or fuel consumed by an average off-highway diese l ar e much 

highe r than those for an on-highway engine , and the potentia l for future 

reductions in emissions is correspondingly greater. 

As discussed in Sections Three through Eight, emission control 

technology for on-highway diese l engines is well developed, and this technology 

could be transferre d t o most off-highway engines as well. Off-highway diese l 

engines can be divided int o high-speed and medium-speed classes, having rated 

operating speeds above or below 1300 RPM, respectively . Except for railway 

locomotives, the great majority of off-highway diese l engines ar e high-speed 

types. These share many design feature s with on-highway truck and light-dut y 

vehicl e engines, so tha t most emissions control technologies demonstrated in 

on-highway engines would be readil y transferable . Medium-speed engines ar e 

used in railway locomotives and some marine vessels. Emissions control 

technology for these engines is less developed, but even the littl e work tha t 

has been done shows the potentia l for major reductions in emissions. 

Sections Four through Eight include a case-by-case discussion of 

applicabl e emission control technologies and achievable emissions standards for 

diese l engines used in each class of off-highway equipment. Table 9-3 

summarizes the emissions standards estimated t o be achievable by each class, 

as well as the percentage reduction from present levels represented by these 

standards. In the intermediat e term, engines in al l classe s except farm 

equipment and construction equipment were estimated to be capable of meeting 

emissions standards comparable t o the Californi a 1988 NO and PM standards for 

off-highway vehicles. Construction and farm equipment were estimated t o 

requir e a higher NO limit , due to the limited potentia l for turbocharging and 

aftercooling . 

Given time to develop advanced emission control technology, i t was 

estimated tha t engines in railway locomotives and marine vessels would be able 

t o comply with emissions standards comparable t o the Federal 1991 standards for 

9-4 
P.30 

1 

RADIAfl 

TABLE 9-3 . 

Locomotive s 

NO 

HC* 

PM 

EMISSIONS STANDARDS ESTIMATED 

BY EACH aASS OF OFF-HIGHWAY 

Marine Vessels 

Medium-Speed Engine s 

NO 

HC* 

PM 

High-Speed Engine s 

NO 

HC* 

PM 

Farm Equipment 

NO 

HC* 

PM 

Constructio n Equipmen 

NO 

HC* 

PM 

Mobil e Refrigeratio n 

NO 

HC* 

PM 

t 

Source : Radian estimate s 

Intermed i 

Standar d 

(g/BHP-hr) 

6.0 

0.5 0 

0.5 0 

6.0 

0.5 0 

0.5 0 

6.0 

0.5 0 

0.5 0 

8.0 

0.5 0 

0.5 0 

8.0 

0.50 

0.5 0 

6.0 

1.0 

0.5 0 

a t e 

Percen t 

Reduction 

55% 

52% 

1% 

55% 

52% 

1% 

45% 

38% 

17% 

30% 

72% 

60% 

12% 

3 2% 

36% 

49% 

10% 

2% 

TO BE ACHIEVABLE 

DIESELS 

Advanced 

Standar d 

(g/BHP-hr) 

5 . 0 

0.3 0 

0.2 0 

5 . 0 

0.3 0 

0.2 0 

5.0 

0.50 

0.2 5 

6.0 

0.2 0 

- 0.1 5 

6.0 

0.20 

0.1 5 

5 . 0 

0.20 

0.1 0 

Technology 

Percen t 

Reduction 

63% 

71% 

60% 

63% 

71% 

60% 

55% 

38% 

59% 

48% 

89% 

88% 

34% 

73% 

81% 

58% 

73% 

80% 

9-5 
P.31 

on-highway vehicles, while those in mobile refrigeratio n units should be able 

to comply with standards comparable t o the 1994 on-highway limits. 

Construction and farm equipment could meet PM standards simila r to the 1994 

levels, but—due to their higher load factors—might not be able to achieve 

the leve l of 0.10 g/BHP-hr mandated for on-highway engines. As is also tru e 

of on-highway engines, a reduction in diese l fuel sulfur content might be 

required to achieve these low particulat e levels. In addition , construction 

and farm equipment would als o requir e a slightl y highe r NO limit than tha t 

mandated for on-highway engines, due to the limited potentia l for 

low-temperature charge cooling. 

The reade r is warned tha t the emissions limits shown in Table 9-3 ar e 

engineering estimate s only, based on very limited data , and intended only t o 

indicat e the potentia l benefits of regulatio n in this area . As discussed 

below, additiona l research t o confirm these estimate s would be essentia l before 

these or any othe r emission standards were incorporated into law. 

Figures 9-1 through 9-3 show the potentia l effects of introducing the 

emissions standards liste d in Table 9-3 on NO , HC, and PM emissions from each 

class of off-highway engines. The leftmost bar for each class represents the 

current situation , with no emissions control . The middle bar represents the 

emissions that would be experienced if al l existin g engines met the 

"intermediate " emissions standards, and the rightmost bar the emissions tha t 

would resul t if al l existin g engines met the "advanced technology" standards. 

The net reduction if every off-highway engine in use met the "advanced 

technology" standards would be about 1.4 millio n tons of NO , 162,000 tons of 

HC, and 146,000 tons of PM per year, or 52 percent, 70 percent, and 78 percent, 

respectively , of the current emissions of these pollutants. In reality , of 

course this would take a very long time t o achieve , due t o the need to turn 

over the existin g engine population. 

The cost-effectiveness of controllin g off-highway diese l emissions to 

a t least the intermediate-term standards shown is estimated t o be very 

favorable compared t o the costs of othe r availabl e emission control measures of 

9-6 
P.32 

P-i 

tn 

c 

o 

•*•* /-s 

to 

x c O o 

Z TH 

r-t 

ti) r-l 

•V "H 

C 

o 

CO 

z 

0.9 -| 

0.8 

0.7 

0.6 

0.5 

0.4 

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0 

T: 

^ 

^ 

^ 

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VI 

V 

^ 

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A 22 

P: 

^ 

^ 

^ 

IT: 

20 

Locomotives 

Marine 

Vessels 

Farm Construction Mobile 

Equipment Equipment Refrigeration 

(Z2 X3 wa 

Uncontrolled Int. Controls Adv. Controls 

Figure 9-1. Estimated Effect of Emissions Controls 

on Total Off-Highway NO Emissions 

9-7 
P.33 

110 

U 

>v 

OT 

C 

o 

U /—v 

w CO 

• a 

u c 

X CQ 

cn 

4> 3 

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V ^ 

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^ m 

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^ 

^ 

2a 

5]_ 

Locomotives 

Marine 

Vessels 

Farm Construction Mobile 

Equipment Equipment Refrigeration 

£Z2 SEI ^ 

Uncontrolled Int. Controls Adv. Controls 

Figure 9-2. Estimated Effect of Emissions Controls 

on Total Off-Highway HC Emissions 

9-8 
RADIAN 

P.34 

U 

>. 

tn 

c 

O <-v 

u tn 

c 

2 CO 

O . CO 

3 

CU o 

•O yC 

•H H 3 ^ 

C 

o 

CO Z 

90 "" 

80 -

70 _ 

60 -

50 _ 

40 -

30 -

20 -

10 -

0 -i i i i i •AA w I 

\ 1 

n 

33 33 33 

III 

Locomotives 

Marine 

Vessels 

Farm 

Equipment 

Construction 

Equipment 

Mobile 

Refrigeration 

Uncontrolled 

XS 

Int . Controls 

vzz 

Adv. Controls 

Figure 9-3. Estimated Effect of Emissions Controls 

on Total Off-Highway PM Emissions 

9-9 
P.35 

simila r significance . Estimated cost-effectiveness values for a number of 

specifi c equipment types ar e shown in Table 9-4. While based on crude 

preliminary cost estimates, these values ar e believed t o somewhat conservative 

(in the sense of over-statin g emissions control costs, and thus the costs per 

ton of pollutants eliminated). Despite this, the cost estimate s for control of 

NO and HC range from a few hundred t o about thre e thousand dollars per ton. 

For comparison, the fuel cost alone for reducing the 1991 NO 

x 

standard for heavy-duty on-highway engines from 5.0 t o 4.0 g/BHP-hr (a step 

which is often suggested) is estimated a t about $2,000 per ton (assuming a 4 

percent fuel economy penalty and fuel a t $0.80 per gallon excluding taxes). 

The incremental cost-effectiveness of the 1994 PM standard of 0.1 g/BHP-hr for 

heavy-duty on-highway engines has been estimated a t about seven to eleven 

thousand dollars per ton (Weaver and Klausmeier, 1987a). 

9.2 Recommendations 

• Much research remains t o be done t o develop a more complete 

understanding of off-highway vehicl e emissions, control technology, 

and cost. The following ar e some key areas for furthe r research . 

1. Improved duty cycle characterizatio n for al l off-highway engine 

classes, leading to improved emissions measurements and to the 

development of representativ e test procedures. 

2. Development of suitabl e emissions measurement techniques for 

off-highway vehicle s (such as marine vessels and construction 

equipment) for which dynamometric techniques are impractical. 

This will probably requir e portabl e sampling equipment to 

measure diese l emissions during normal operation of the vehicle . 

3. Extensive emissions measurements on current production engines, 

and on in-use equipment, leading to more accurat e emission 

factors. 

9-10 
TABLE 9-4 . ESTIMATED COST-EFFECTIVENESS OF "INTERMEDIATE LEVEL" 

EMISSIONS CONTROLS FOR DIFFERENT CLASSES OF OFF-HIGHWAY 

VEHICLES 

P.36 

Cost Effectiveness ($/ton) 

NO + HC 

x 

PM 

Locomotives 

New 

Retrofit 

$1,073 

1.332 

2 

"2 

Marine Vessels 

Medium Speed 

High-Speed Propulsion 

High-Speed Generator 

672 

888 

616 

2 

"2 

"2 

Farm Equipment 

Large 4WD Tractor 

Small Tractor 

Combine 

845 

2.960 

848 

3.067 

7.607 

1,900 

Construction Equipment 

Hydraulic Excavator 

Industrial Tractor 

Concrete Paver 

748 

1.567 

2.045 

8.969 

5.323 

3.961 

Mobile Refrigerator 

Railca r Unit 

Truck/Container Unit 

229 

1,909 

Approximate estimate s based on engineering judgement and limited data , 

tex t Chapters 4-8 for assumptions and limitations. 

See 

PM reductions at "intermediate" control level are estimated as small or 

negative for these categories. This is due to low PM emissions to begin with, 

and the effects of the NO /PM tradeoff. 

9-11 
P.37 

4 . Development of improved estimate s of engine populations, age and 

technology, utilization , and fuel consumption in order to 

provide accurat e emissions inventories. 

5. Assessment of urban-area and regional-scal e effects of 

off-highway vehicl e emissions. 

6. Study of effects of availabl e emission control technologies in 

individua l engines and vehicles. It is recommended that EPA 

perform only preliminary studie s in tis area , as experience has 

shown tha t detaile d development and optimization of emissions 

controls is best left t o the manufacturers. 

7. Much more detailed analysis of the costs of control, including 

costs of accommodating any changes in engine performance and/or 

transien t response . 

8. Evaluation of in-use deterioratio n in emissions in off-highway 

equipment, including the effects of tampering and malmaintenance 

of emissions controls. A recent study for the Californi a ARB 

(Weaver and Klausmeier, 1987b) concluded that these effects 

could result in heavy-duty truck PM emissions more than double 

the applicabl e standards, and simila r increases might be 

expected in off-highway engines. 

In the event that emissions regulation s ar e considered for farm and 

constructio n equipment engines, careful consideration should be given 

t o phase-in mechanisms in order to avoid undue burden on the 

industry . An averaging, trading , and banking approach with 

"crawling" targe t levels, such as tha t discussed in Section 

6.5 , would be one fairl y straightforward way t o do this. 

9-12 
P.38 

RADIAN 

In the event that emissions regulations are considered for new 

medium-speed marine and locomotive engines, consideration should also 

be given to establishing retrofit requirements for older engines in 

these categories. These requirements could most conveniently apply 

at the time of rebuild. . 

9-13 
P.39 

1 

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SOO 

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500 

250 

500 

NOTCH 

1 

2 

3 

4 

6 

8 

7 

8 

IDLE 

BRAKE 

OFF 

EMISSIONS, LB/HR 

FUEL RATE 

(lb/hr) (gal/hr 

51.7 

104.8 

205.2 

320.4 

464.8 

690.2 

887.2 

862.1 

88.0 

0.0 

EMISSIONS, La/1000 GAL 

EHO 500 

SOO 

500 

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500 

SOO 

500 

600 

SOO 

SOO 

1 

2 

3 

4 

S 

6 

7 

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56.7 

163.0 

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331.4 

410.4 

564.0 

748.0 

888.0 

88.0 

0.0 

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14.8 

29.1 

45.5 

64.6 

83.8 

88.0 

122.4 

4.0 

13.8 

0.0 

7.8 

23.1 

32.3 

47.1 

68.3 

78.7 

106.4 

126.2 

4.0 

13.8 

0.0 

EMISSIONS ( LB/1000 GALl 

NOx HC CO PN 

680.1 

686.2 

638.7 

542.1 

601.1 

436.8 

408.1 

367.7 

414.6 

642.1 

0.0 

604.7 

608.8 

678.0 

614.0 

580.8 

530.6 

647.3 

622.6 

527.3 

614.0 

0.0 

83.0 

70.3 

61.8 

83.3 

66.6 

68.0 

68.2 

5S.8 

261.0 

63.3 

0.0 

38.3 

19.5 

17.6 

15.8 

13.6 

13.0 

14.7 

16.4 

88.3 

15.8 

0.0 

158.7 

82.7 

85.6 

142.5 

203.0 

268.8 

186.1 

141.0 

505.3 

142.5 

0.0 

83.1 

55.2 

42.5 

68.2 

70.1 

126.3 

134.8 

80.4 

241.3 

68.2 

0.0 

87.0 

41.8 

16.8 

12.6 

12.6 

14.6 

14.4 

14.8 

77.8 

12.5 

0.0 

8.1 

11.2 

10.1 

12.4 

16.8 

16.0 

18.7 

11.5 

13.1 

12.4 

0.0 

TABLE A-2. 

LINE 

4.8 

2.4 

1.8 

4.6 

1.9 

1.9 

2.4 

20.1 

23.3 

3.9 

32.6 

100.0 

4.8 

2.4 

1.9 

4.8 

1.9 

1.9 

2.4 

20.1 

23.3 

3.9 

32.8 

100.0 

CACLOJLATION OF 

X DUTY CYCLE 

-HITCH 

8.6 

4.8 

3.8 

1.8 

1.0 

1.0 

0.0 

0.0 

33.2 

0.0 

44.8 

100.0 

9.8 

4.8 

3.8 

1.8 

1.0 

1.0 

0.0 

0.0 

33.2 

0.0 

44.8 

100.0 

AVO. 

7.76 

3.89 

3.10 

3.01 

1.32 

1.32 

0.82 

7.60 

29.44 

1.46 

40.14 

100.0 

7.76 

3.89 

3.10 

3.01 

1.32 

1.32 

0.82 

7.65 

29.44 

1.48 

40.14 

100.0 

IN 

LINE 

0.35 

0.38 

0.66 

2.18 

1.24 

1.81 

2.38 

24.84 

0.83 

0.53 

0.00 

34.8 

0.38 

0.56 

0.82 

2.25 

1.18 

1.61 

2.57 

2S.41 

0.93 

0.63 

0.00 

35.8 

CYCLE-WERAGE 

FUEL USED 

MOOE/HR (GALl 

SNITCH AVG. 

0.70 

0.71 

1.12 

0.87 

0.B2 

0.80 

0.00 

0.00 

1.33 

0.00 

0.00 

6.2 

0.76 

1.11 

1.24 

0.90 

0.S8 

0.75 

0.00 

0.00 

1.33 

0.00 

0.00 

6.8 

0.67 

0.88 

0.90 

1.37 

0.86 

1.11 

0.91 

9.37 

1.18 

0.20 

0.00 

17.0 

0.61 

0.90 

1.00 

1.42 

0.77 

1.04 

0.98 

8.66 

1.19 

0.20 

0.00 

17.B 

EMISSIONS FOR 

NO. 

THE SHRI 

EMISSIONS 

IN NOOE/HR (LB) 

UNE SWITCH AVG. 

0.20 

0.26 

0.38 

1.18 

0.82 

0.70 

0.88 

9.08 

0.39 

0.29 

0.00 

14.0 

403 

0.23 

0.34 

0.36 

1.38 

0.66 

0.60 

1.41 

13.28 

0.49 

0.33 

0.00 

19.3 

537 

0.41 

0.60 

0.71 

0.47 

0.31 

0.36 

0.00 

0.00 

0.66 

0.00 

0.00 

3.3 

637 

0.46 

0.68 

0.72 

0.66 

0.33 

0.40 

0.00 

0.00 

0.70 

0.00 

0.00 

3.8 

677 

0.33 

0.40 

0.68 

0.74 

0.43 

0.48 

0.37 

3.44 

0.49 

0.11 

0.00 

7.4 

433 

0.37 

0.5S 

0.68 

0.87 

0.46 

0.85 

0.63 

5.06 

0.82 

0.12 

0.00 

8.7 

648 

LOCOMOTIVE ENGINE TESTS 

HC EMIS8I0N8 

IN 

LINE 

0.03 

0.03 

0.03 

0.14 

0.06 

0.09 

8.14 

1.39 

0.24 

0.03 

0.00 

2.2 

83 

0.01 

0.01 

0.01 

0.04 

0.02 

0.02 

0.04 

0.42 

0.08 

0.01 

0.00 

0.7 

18 

NODE/HR (LBI 

SNITCH AVG. 

0.06 

0.06 

0.06 

0.06 

0.04 

0.04 

0.00 

0.00 

0.36 

0.00 

0.00 

0.7 

106 

0.03 

0.02 

0.O2 

0.01 

0.01 

0.01 

0.00 

0.00 

0.12 

0.00 

0.00 

0.2 

33 

0.05 

0.04 

o.oe 

0.08 

0.06 

o.oa 

0.06 

0.62 

0.31 

0.01 

0.00 

1.2 

73 

0.02 

0.02 

0.02 

0.02 

0.01 

0.01 

0.01 

0.16 

0.10 

0.00 

0.00 

0.4 

22 

CO EMISSI0N8 

IN 

UNE 

0.06 

0.03 

0.05 

0.31 

0.25 

0.43 

0.47 

3.47 

0.47 

0.08 

0.00 

5.8 

182 

0.03 

0.03 

0.03 

0.16 

0.08 

0.18 

0.36 

2.30 

0.22 

0.04 

0.00 

3.4 

95 

NOOE/HR (LB) 

SNITCH 

0.11 

0.08 

0.11 

0.12 

0.13 

0.22 

0.08 

0.00 

0.67 

0.00 

0.00 

1.4 

228 

0.08 

0.08 

0.05 

0.08 

0.04 

0.10 

0.00 

0.00 

0.32 

0.00 

0.00 

0.7 

104 

AV8. 

0.09 

0.00 

O.OB 

0.20 

0.17 

a. so 

0.18 

1.32 

0.60 

0.03 

0.00 

3.0 

177 

0.06 

0.05 

0.04 

0.10 

0.06 

0.13 

0.13 

0.87 

0.28 

0.01 

0.00 

1.7 

87 

PH EMI8SI0N8 

IN HW6/HP 

UNE SNITCH 

0.03 

o.oe 

0.01 

0.03 

o.oe 

o.oe 

0.83 

0.36 

0.07 

0.01 

0.00 

0.8 

17 

0.00 

0.01 

0.01 

0.03 

o.oe 

o.oe 

0.06 

0.28 

0.01 

0.01 

0.00 

0.4 

12 

0.06 

0.03 

o.oe 

0.01 

0.01 

0.01 

0.00 

0.00 

0.10 

0.00 

0.00 

o.e 

40 

0.01 

0.01 

0.01 

0.01 

0.01 

0.01 

0.00 

0.00 

o.oe 

0.00 

0.00 

0.1 

12 

(LB) 

AVO. 

0.06 

0.02 

0.02 

0.02 

0.01 

0.02 

0.01 

0.14 

0.09 

0.00 

0.00 

0.4 

22 

0.00 

0.01 

0.01 

0.02 

0.01 

o.oe 

0.02 

0.11 

0.02 

0.00 

0.00 

0.2 

12 
P.42 

RADIAN 

•* 

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10- 1 
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10-3 
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10-4