●

A national laboratory of the U.S. Department of Energy 

Office of Energy Efficiency & Renewable Energy 

National Renewable Energy Laboratory 

Innovation for Our Energy Future 

Effects of Biodiesel Blends on Milestone Report 

NREL/MP-540-40554 Vehicle Emissions October 2006 

Fiscal Year 2006 Annual Operating Plan 

Milestone 10.4 

R.L. McCormick, A. Williams, J. Ireland, 

M. Brimhall, and R.R. Hayes 

NREL is operated by Midwest Research Institute Battelle Contract No. DE-AC36-99-GO10337 
Milestone Report

NREL/MP-540-40554

October 2006

Effects of Biodiesel Blends on 

Vehicle Emissions 

Fiscal Year 2006 Annual Operating Plan 

Milestone 10.4 

R.L. McCormick, A. Williams, J. Ireland, 

M. Brimhall, and R.R. Hayes 

Prepared under Task No. FC06.9400 

National Renewable Energy Laboratory

1617 Cole Boulevard, Golden, Colorado 80401-3393 

303-275-3000 • www.nrel.gov

Operated for the U.S. Department of Energy

Office of Energy Efficiency and Renewable Energy

by Midwest Research Institute • Battelle 

Contract No. DE-AC36-99-GO10337
NOTICE

This report was prepared as an account of work sponsored by an agency of the United States government. 

Neither the United States government nor any agency thereof, nor any of their employees, makes any 

warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or

usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not 

infringe privately owned rights. Reference herein to any specific commercial product, process, or service by

trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement,

recommendation, or favoring by the United States government or any agency thereof. The views and

opinions of authors expressed herein do not necessarily state or reflect those of the United States

government or any agency thereof. 

Available electronically at http://www.osti.gov/bridge

Available for a processing fee to U.S. Department of Energy

and its contractors, in paper, from: 

U.S. Department of Energy

Office of Scientific and Technical Information 

P.O. Box 62 

Oak Ridge, TN 37831-0062

phone: 865.576.8401 

fax: 865.576.5728 

email: mailto:reports@adonis.osti.gov

Available for sale to the public, in paper, from: 

U.S. Department of Commerce 

National Technical Information Service 

5285 Port Royal Road 

Springfield, VA 22161 

phone: 800.553.6847 

fax: 703.605.6900 

email: orders@ntis.fedworld.gov

online ordering: http://www.ntis.gov/ordering.htm

Printed on paper containing at least 50% wastepaper, including 20% postconsumer waste
Executive Summary 

Biodiesel is a fuel-blending component produced from vegetable oils, animal fats, or waste grease by 

reaction with methanol or ethanol to produce methyl or ethyl esters. Pure biodiesel contains 

approximately 10 weight percent oxygen. It is typically blended with petroleum diesel at levels up to 

20% (B20). The presence of oxygen in the fuel leads to a reduction in emissions of hydrocarbons 

(HC) and toxic compounds, carbon monoxide (CO), and particulate matter (PM) when biodiesel 

blends are burned in diesel engines. These reductions are robust and have been observed in numerous 

engine and vehicle testing studies. Engine dynamometer studies reviewed in a 2002 report from EPA 

show a 2% increase in oxides of nitrogen (NOx) emissions for B20. This perceived small increase in 

NOx is leading some state regulatory agencies to consider banning the use of biodiesel. Therefore, the 

issue of NOx emissions is potentially a significant barrier to expansion of biodiesel markets. 

The objective of this study was to determine if testing entire vehicles, vs. just the engines, on a heavyduty chassis dynamometer provides a better, more realistic measurement of the impact of B20 on 

regulated pollutant emissions. This report also documents completion of the National Renewable 

Energy Laboratory’s Fiscal Year 2006 Annual Operating Plan Milestone 10.4. This milestone 

supports the U.S. Department of Energy, Fuels Technologies Program Multiyear Program Plan Goal 

of identifying fuels that can displace 5% of petroleum diesel by 2010. 

We reviewed more recently published engine testing studies (Table 3) and found an average change in 

NOx for all recent B20 studies of -0.6%±2.0% (95% confidence intervals are used throughout this 

report). Restricting the average to recent studies of B20 with soy biodiesel yields an average NOx 

impact of 0.1%±2.7%. The EPA review also includes summary of a smaller vehicle testing dataset 

that shows no significant impact of biodiesel on NOx. We reviewed several recently published vehicle 

(chassis) testing studies (Tables 4 and 5) and found an average change in NOx of 1.2%±2.9% for B20 

from soy-derived biodiesel. In addition, we reviewed three portable emissions measurement system 

(PEMS) studies that do not find NOx to increase. 

Eight heavy-duty diesel vehicles were tested, including three transit buses, two school buses, two 

Class 8 trucks, and one motor coach. Four met the 1998 heavy-duty emissions requirement of 4 

g/bhp-h NOx and four met the 2004 limit of 2.5 g/bhp-h NOx+HC. Driving cycles that simulate both 

urban and freeway driving were employed. Each vehicle was tested on a petroleum-derived diesel 

fuel and on a 20 volume percent blend of that fuel with soy-derived biodiesel. On average B20 caused 

PM and CO emissions to be reduced by 16% to 17% and HC emissions to be reduced by 12% relative 

to petroleum diesel. Emissions of these three pollutants nearly always went down, the exception being 

a vehicle equipped with a diesel particle filter that showed very low emissions of PM, CO, and HC; 

and there was no significant change in emissions for blending of B20. The NOx impact of B20 varied 

with engine/vehicle technology and test cycle ranging from -5.8% to +6.2%. A preliminary 

examination of real-time NOx emission data did not reveal any consistent reason for the wide range. 

On average NOx emissions did not change (0.6%±1.8%). If the results of this study are combined 

with the soy B20 chassis results from Tables 4 and 5 (recently published studies), the average change 

in NOx is 0.9%±1.5%, based on data for 15 vehicles. 

Based on the studies reviewed and new data reported here, there does not appear to be a discrepancy 

between engine and chassis testing studies for the effect of B20 on NOx emissions. Individual engines 

may show NOx increasing or decreasing, but on average there appears to be no net effect, or at most a 

very small effect on the order of ±0.5%. The small apparent increase in NOx reported for enginetesting results in EPA’s 2002 review occurred because the dataset was not adequately representative 

of on-highway engines. In particular, nearly half of the NOx observations included in the review were 

for engines from a single manufacturer (DDC). Newer engine and chassis studies, which on average 

show no B20 effect on NOx, are not representative samples either. However, considering all of the 

data available, we conclude that B20 has no net impact on NOx. 

iii 
Table of Contents 

Executive Summary...........................................................................................................iii 

Table of Contents............................................................................................................... iv 

List of Figures ..................................................................................................................... v 

List of Tables ..................................................................................................................... vi 

Acronyms and Abbreviations ............................................................................................. x 

Introduction......................................................................................................................... 1 

Background......................................................................................................................... 2 

Engine Dynamometer Studies......................................................................................... 2 

Vehicle Testing Studies .................................................................................................. 6 

Comparison of Engine and Vehicle Test Results ........................................................... 9 

Fundamental Studies of Biodiesel and NOx Emissions .................................................. 9 

Methodology..................................................................................................................... 12 

Vehicle Emissions Test Lab.......................................................................................... 12 

Chassis Dynamometer .............................................................................................. 12 

Fuel Handling............................................................................................................ 13 

Air Handling and Conditioning ................................................................................ 13 

Emissions Measurement ........................................................................................... 13 

Test Vehicles................................................................................................................. 14 

Driving Cycles .............................................................................................................. 16 

Test Fuels...................................................................................................................... 19 

Results............................................................................................................................... 21 

Transit Bus Results ....................................................................................................... 21 

Class 8 Truck Results.................................................................................................... 23 

iv 
Motor Coach Results..................................................................................................... 24 

School Bus Results ....................................................................................................... 25 

Results Summary .......................................................................................................... 26 

Discussion......................................................................................................................... 29 

Examination of Real Time NOx Emissions Data.......................................................... 30 

Summary and Recommendations ..................................................................................... 34 

Appendix: Detailed Chassis Test Data ............................................................................ 36 

References......................................................................................................................... 54 

List of Figures 

Figure 1. Trends in percentage change in pollutant emissions with biodiesel content as 

estimated from published engine dynamometer data in the EPA study [16]...................... 3 

Figure 2. Percent change in NOx emissions for the engine dynamometer data reviewed 

Figure 3. Percent change in PM emissions for the engine dynamometer data reviewed by

Figure 4. Summary of NOx impact of biodiesel blending from chassis dynamometer 

Figure 11. Comparison of NOx emissions for conventional diesel and B20 for each 

by EPA [16]. ....................................................................................................................... 4 

EPA [16]. ............................................................................................................................ 4 

studies reviewed by EPA [16]............................................................................................. 6 

Figure 5. Chassis Dynamometer Schematic ..................................................................... 12 

Figure 6. The CSHVC cycle. ........................................................................................... 17 

Figure 7. The UDDS cycle............................................................................................... 17 

Figure 8. The CILCC modified cycle. ............................................................................. 18 

Figure 9. The RUCSBC cycle.......................................................................................... 18 

Figure 10. The Freeway cycle.......................................................................................... 19 

vehicle tested and each cycle. ........................................................................................... 27 

v 
Figure 12. Comparison of PM emissions for conventional diesel and B20 for each 

vehicle tested and each cycle. ........................................................................................... 27 

Figure 13. Comparison of CO emissions for conventional diesel and B20 for each 

vehicle tested and each cycle. ........................................................................................... 28 

Figure 14. Comparison of THC emissions for conventional diesel and B20 for each 

vehicle tested and each cycle. ........................................................................................... 28 

Figure 15. Portions of the CSHVC real-time NOx traces for RTD Transit Bus #3. ........ 31 

Figure 16. Portions of the CSHVC real-time NOx traces for the Freightliner Class 8 

truck. ................................................................................................................................. 32 

Figure 17. Portions of the CSHVC real-time NOx traces for the motor coach................ 32 

Figure 18. Portions of the CILCC real-time NOx traces for the International Class 8 

truck. ................................................................................................................................. 33 

List of Tables 

Table 1. Average Change in Emissions for B20 as Estimated from Published Engine

Dynamometer Data in the EPA Study [16]......................................................................... 2 

Table 2. Number of Engines and NOx Emissions Observations for the Data Reviewed by

EPA [16]. ............................................................................................................................ 3 

Table 3. Summary of Percent Change in Emissions for Recent Engine Dynamometer 

Studies of Biodiesel. ........................................................................................................... 5 

Table 4. Summary of Percent Change in Emissions from Recent Vehicle Testing Studies 

of Biodiesel. ........................................................................................................................ 7 

Table 5. Summary of Percent Change in Emission Results from U.S. Navy Study of B20 

Emission Impacts [29]. ....................................................................................................... 8 

Table 6. Description of Vehicles Tested.......................................................................... 15 

Table 7. Cycle Statistics for Various Driving Cycles Used in this Study........................ 16 

Table 8. Properties of Test Fuels. .................................................................................... 20 

Table 9. Emission Test Results for Transit Bus #1 on CSHVC Comparing LSD A and 

B20/BlueSun Biodiesel..................................................................................................... 22 

Table 10. Emission Test Results for Transit Bus #2 on CSHVC Comparing LSD A and 

B20/BlueSun Biodiesel..................................................................................................... 22 

vi
Table 11. Emission Test Results for Transit Bus #3 on CSHVC Comparing LSD A and 

B20/BlueSun Biodiesel..................................................................................................... 22 

Table 12. Emission Test Results for Transit Bus #3 on CSHVC Comparing LSD B and 

B20/Agland Biodiesel....................................................................................................... 22 

Table 13. Emission Test Results for International Class 8 on CILCCmod Comparing 

LSD C and B20/Agland Biodiesel.................................................................................... 23 

Table 14. Emission Test Results for International Class 8 on Freeway Cycle Comparing

LSD C and B20/Agland Biodiesel.................................................................................... 23 

Table 15. Emission Test Results for the Freightliner Class 8 on CSHVC Comparing 

2007 Certification Diesel and B20/Agland Biodiesel....................................................... 24 

Table 16. Emission Test Results for the Freightliner Class 8 on the Freeway Cycle 

Comparing 2007 Certification Diesel and B20/Agland Biodiesel.................................... 24 

Table 17. Emission Test Results for the Motor Coach on CSHVC Comparing 2007 

Certification Diesel and B20/Agland Biodiesel................................................................ 24 

Table 18. Emission Test Results for the Motor Coach on the UDDS Comparing 2007 

Certification Diesel and B20/Agland Biodiesel................................................................ 25 

Table 19. Emission Test Results for the International Green Diesel School Bus on 

CSHVC Comparing 2007 Certification Diesel and B20/Agland Biodiesel. .................... 25 

Table 20. Emission Test Results for the International Green Diesel School Bus on 

RUCSBC Comparing 2007 Certification Diesel and B20/Agland Biodiesel................... 26 

Table 21. Emission Test Results for the International Conventional School Bus on 

CSHVC Comparing 2007 Certification Diesel and B20/Agland Biodiesel. .................... 26 

Table 22. Emission Test Results for the International Conventional School Bus on 

RUCSBC Comparing 2007 Certification Diesel and B20/Agland Biodiesel................... 26 

Table 23. Average Percent Change in Emissions and Fuel Economy for All Vehicles 

Tested................................................................................................................................ 29 

Table 24. Average Percent Change in Emissions for Specific Subsets of the Total 

Dataset, 95% Confidence Interval is Shown..................................................................... 30 

Table 25. RTD Transit Bus #1 – CSHVC – LSD A ......................................................... 36 

Table 26. RTD Transit Bus #1 – CSHVC – B20 (LSD A and BlueSun Biodiesel) ......... 36 

Table 27. RTD Transit Bus #2 – CSHVC – LSD A ........................................................ 37 

Table 28. RTD Transit Bus #2 – CSHVC – B20 (LSD A and BlueSun Biodiesel) ........ 37 

vii 
Table 29. RTD Transit Bus #3 – CSHVC – LSD A ........................................................ 38 

Table 34. International Class 8 Truck – CILCCmod – B20 (LSD C and Agland 

Table 36. International Class 8 Truck – Freeway Cycle – B20 (LSD C and Agland 

Table 38. Freightliner Class 8 Truck – CSHVC – B20 (2007 Cert Diesel and Agland 

Table 40. Freightliner Class 8 Truck – Freeway Cycle – B20 (2007 Cert Diesel and 

Table 46. Green Diesel School Bus – RUCSBC– B20 (2007 Cert Diesel and Agland 

Table 48. Green Diesel School Bus – CSHVC – B20 (2007 Cert Diesel and Agland 

Table 30. RTD Transit Bus #3 – CSHVC – B20 (LSD A and BlueSun Biodiesel) ........ 38 

Table 31. RTD Transit Bus #3 – CSHVC – LSD B ........................................................ 39 

Table 32. RTD Transit Bus #3 – CSHVC – B20 (LSD B and Agland Biodiesel) .......... 39 

Table 33. International Class 8 Truck – CILCCmod – LSD C........................................ 40 

Biodiesel) .......................................................................................................................... 40 

Table 35. International Class 8 Truck – Freeway Cycle – LSD C .................................. 41 

Biodiesel) .......................................................................................................................... 41 

Table 37. Freightliner Class 8 Truck – CSHVC – 2007 Cert Diesel............................... 42 

Biodiesel) .......................................................................................................................... 42 

Table 39. Freightliner Class 8 Truck – Freeway Cycle – 2007 Cert Diesel .................... 43 

Agland Biodiesel) ............................................................................................................. 43 

Table 41. Motor Coach – CSHVC – 2007 Cert Diesel.................................................... 44 

Table 42. Motor Coach – CSHVC – B20 (2007 Cert Diesel and Agland Biodiesel)...... 44 

Table 43. Motor Coach – UDDS – 2007 Cert Diesel ...................................................... 45 

Table 44. Motor Coach – UDDS – B20 (2007 Cert Diesel and Agland Biodiesel) ........ 45 

Table 45. Green Diesel School Bus – RUCSBC– 2007 Cert Diesel ............................... 46 

Biodiesel) .......................................................................................................................... 47 

Table 47. Green Diesel School Bus – CSHVC – 2007 Cert Diesel................................. 48 

Biodiesel) .......................................................................................................................... 49 

Table 49. Conventional School Bus – RUCSBC – 2007 Cert Diesel.............................. 50 

viii 
Table 50. Conventional School Bus – RUCSBC – B20 (2007 Cert Diesel and Agland 

Biodiesel) .......................................................................................................................... 51 

Table 51. Conventional School Bus – CSHVC – 2007 Cert Diesel ................................ 52 

Table 52. Conventional School Bus – CSHVC – B20 (2007 Cert Diesel and Agland 

Biodiesel) .......................................................................................................................... 53 

ix 
Acronyms and Abbreviations 

Bxx biodiesel blend containing xx% biodiesel 

CARB California Air Resources Board 

CFR Code of Federal Regulations 

CILCC combined international local and commuter cycle 

CO carbon monoxide 

CO2 carbon dioxide 

CSHVC city-suburban heavy-vehicle cycle 

CVS constant volume sampling 

DC direct current 

DDC Detroit Diesel Corporation 

DOC diesel oxidation catalyst 

DPF diesel particle filter 

EGR exhaust gas recirculation 

EPA U.S. Environmental Protection Agency 

FTP federal test procedure 

g/bhp-h grams per brake horsepower-hour 

g/cc grams per cubic centimeter 

HC hydrocarbon 

hp horsepower 

IDI indirect injection 

L liter 

lb pounds mass 

LSD low-sulfur diesel (<500 ppm S) 

mph miles per hour 

NO nitric oxide 

NOx oxides of nitrogen 

NREL National Renewable Energy Laboratory 

O2 oxygen 

PEMS portable emissions measurement system 

PM particulate matter 

ppm parts per million 

REE rapeseed ethyl ester 

ReFUEL Renewable Fuels and Lubricants Laboratory 

RME rapeseed methyl ester 

RTD Regional Transportation District 

RUCSBC Rowan University Composite School Bus Cycle 

SME soy methyl ester 

TDI turbocharged-direct injected 

THC total hydrocarbon (the same as HC in this study) 

TxLED Texas low emissions diesel 

UDDS urban dynamometer driving schedule 

ULSD ultra-low-sulfur diesel (<15 ppm S) 

WVU West Virginia University 

x 
Introduction 

Biodiesel is a fuel-blending component produced from vegetable oils, animal fats, or 

waste grease by reaction with methanol or ethanol to produce methyl or ethyl esters 

(transesterification). In the United States, essentially all biodiesel is fatty acid methyl 

esters. Biodiesel production was 75 million gallons in 2005 and is expected to grow 

rapidly with market size, reaching 300 million gallons in 2006 [1]. Roughly 90% of the 

biodiesel produced in the United States today is made from soybean oil. An assessment 

of the resource available to produce biodiesel indicates that today there is adequate 

feedstock available to produce more than 1.7 billion gallons per year [2]. Life cycle 

analysis shows that for soy-derived biodiesel the energy available in the biodiesel product 

is more than three times the fossil energy used in its production [3]. 

Pure biodiesel contains approximately 10 weight percent oxygen. It is typically used as a 

blend with petroleum diesel at levels up to 20% (B20). The presence of oxygen in the 

fuel leads to a reduction in emissions of hydrocarbons (HC) and toxic compounds, carbon 

monoxide (CO), and particulate matter (PM) when biodiesel blends are burned in diesel 

engines [4]. These reductions are robust and have been observed in numerous engine and 

vehicle testing studies. Engine dynamometer studies conducted mainly in the 1990s have 

shown a small increase (2%) in oxides of nitrogen (NOx) emissions for B20, and most 

studies of the impact of biodiesel on pollutant emissions have employed engine 

dynamometer tests. This perceived small increase in NOx is leading some state 

regulatory agencies to consider banning the use of biodiesel. Therefore the issue of NOx 

emissions is potentially a significant barrier to expansion of biodiesel markets. However, 

a 2% increase in NOx is only slightly greater than the measurement repeatability of many 

heavy-duty test labs. Additionally, several engine testing studies have found no increase, 

or even a decrease in emissions of NOx. 

The objective of this study was to determine if testing entire vehicles on a heavy-duty 

chassis dynamometer provides a better, more realistic measurement of the impact of B20 

on regulated pollutant emissions. 

1
Background 

Engine Dynamometer Studies 

A number of studies have examined the emission impacts of biodiesel in 4-stroke, 

electronically controlled, turbocharged, direct injected diesel engines [5, 6, 7, 8, 9, 10, 

11, 12, 13, 14, 15]. These studies as well as others using 2-stroke, indirect injection 

(IDI), and naturally aspirated engines have been reviewed by the U.S. Environmental 

Protection Agency (EPA) [16] and statistical analysis indicated the average emission 

changes for B20 shown in Table 1. Figure 1, taken from the EPA report, shows the 

overall trends with biodiesel blending level for all four regulated pollutants. The small 

increase in NOx emissions for B20 listed in Table 1 is notable because a 2% change in 

NOx is only slightly greater than the test repeatability (coefficient of variation) for NOx 

measurements at the best test laboratories. 

Table 1. Average Change in Emissions for B20 as Estimated from Published 

Engine Dynamometer Data in the EPA Study [16]. 

Pollutant Percent Change 

HC -21.1 

CO -11.0 

NOx +2.0 

PM -10.1 

The results are derived from published data on 43 different engines of varying model 

year. These are grouped by emission standard or technology in Table 2. The dataset is 

dominated by 26 engines in the 1991 to 1993 group (5 g/bhp-h NOx and 0.25 g/bhp-h 

PM) and the 1994 to 1997 group (5 g/bhp-h NOx and 0.1 g/bhp-h PM). Fifteen out of the 

group of 26 engines were from a single manufacturer, Detroit Diesel Corporation (DDC). 

Fully 64% of the 546 NOx observations for this model year range are for DDC engines, 

and these observations make up 44% of the total NOx observations. Because of the high 

concentration of engines from a single manufacturer and in a limited range of model 

years, this group of engines cannot be considered to be representative of on-highway 

engines in the United States. Notably the dataset includes only two engines certified at 4 

g/bhp-h NOx and no engines in technology group B certified at 2.5 g/bhp-h NOx+HC. 

This later group typically employs exhaust gas recirculation (EGR) to obtain lower NOx 

levels. The majority of the engines were on-highway heavy-duty engines and were tested 

over the heavy-duty federal test procedure (FTP) or multimode steady-state cycles. 

Figures 2 and 3 show the NOx and PM emission curves, respectively, as a function of 

biodiesel blend content, along with the individual data points. Examining the B20 

results, a wide range of -60% to +5% is observed for PM; however, PM emissions 

increased in only one test. A wide range is also observed for NOx emissions with 

percentage change ranging from roughly -7% to +7%. 

2
Figure 1. Trends in percentage change in pollutant emissions with biodiesel 

content as estimated from published engine dynamometer data in the EPA study

[16].

Table 2. Number of Engines and NOx Emissions Observations for the Data 

Reviewed by EPA [16].

3
Figure 2. Percent change in NOx emissions for the engine dynamometer data 

reviewed by EPA [16]. 

Figure 3. Percent change in PM emissions for the engine dynamometer data 

reviewed by EPA [16]. 

Additional engine testing studies have been published since the release of the EPA 

review. McGill and coworkers tested two heavy-duty engines (4- to 5-g/bhp-h NOx 

emission range) [17]. Additional details for a Euro 2 Volvo 9.6-L engine are given in 

reference 18. NOx emissions were unchanged for a 5-g/bhp-h NOx Navistar 7.3-L engine 

(B100) but increased for a Euro 2 Volvo engine on B30. Frank and coworkers tested a 4­

g/bhp-h NOx International DT466 and observed NOx to decrease significantly for B20 

when configured with DOC, no change when configured with DPF, and to increase 

slightly when configured with EGR and DPF [19]. A second study tested two 4-g/bhp-h 

NOx Cummins engines and found statistically significant reductions in NOx for B20 in 

4
some tests, and small increases in NOx in others [20]. Notably, the NOx reductions were 

observed for biodiesel from more saturated feedstocks, in agreement with previous 

studies [4]. Researchers at Penn State University tested a 4-g/bhp-h NOx Cummins 

engine and observed a 3% reduction in NOx for a low sulfur base fuel and no change for 

an ultra-low sulfur base fuel [21]. Results for two engines meeting the 2.5-g/bhp-h 

NOx+HC level have also been reported, with NOx found to increase by 3 to 6% [22]. 

Environment Canada has reported testing of a 1998 Caterpillar 3126E with no change in 

NOx [23]. 

The percent change in emissions for these studies relative to the base petroleum fuel is 

listed in Table 3. The average change in NOx for all B20 studies reported in this table is 

-0.6%±2.0% (95% confidence interval). Restricting the average to studies of B20 with 

soy biodiesel only yields an average NOx impact of 0.1%±2.7%. Clearly recent engine 

testing studies continue to see NOx emission results that vary widely and appear to 

depend upon engine manufacturer or engine design. The average PM emission change 

for all B20 studies reported in the table is -14.1%, excluding the two DPF points the PM 

reduction was 16.4%. 

Table 3. Summary of Percent Change in Emissions for Recent Engine 

Dynamometer Studies of Biodiesel.

Reference Engine Cycle %Biodiesel NOx HC CO PM 

17 Navistar 7.3-L (5 

g/bhp-h NOx) 

AVL 8­

Mode 

100 (RME) ≈0 -- -- ≈-20% 

18 Volvo 9.6-L (Euro 

2) 

ECE R49 30 (RME) 1.7 0 -9.4 -24 

19 International 

DT466 (4 g/bhp-h 

NOx with DOC) 

Hot FTP 20 (SME) -10.3 -20 -38 -2.9 

-with DPF 20 (SME) 0 ≈0 ≈0 ≈0

 -with EGR and 

DPF 

 20 (SME) 1.8 ≈0 ≈0 ≈0 

20 Cummins 8.3-L (4 

g/bhp-h NOx Mech) 

Hot FTP 20 (SME) 1.1 -12 -25 -31 

20 (Waste 

Grease) 

0.3 -7.0 -25 -20 

20 (Animal Fat) -1.5 -13 -17 -22 

Cummins 8.3-L (4 

g/bhp-h NOx Elec) 

Hot FTP 20 (SME) 1.7 -21 -28 -17 

20 (Waste 

Grease) 

-4.5 -25 -31 -14 

20 (Animal Fat) -2.9 -30 -25 -7.8 

21 Cummins 5.9-L (4 

g/bhp-h NOx) 

AVL 8­

Mode 

20 (SME, 325 

ppm S Base) 

0 -- -- -27 

20 (SME, 15 ppm 

S Base) 

-3 -- -- -6 

22 Cummins 5.9-L 

(2.5 g/bhp-h NOx) 

Hot FTP 20 (SME) 3.6 -4.2 -10.5 -22 

DDC S60 (4 g/bhph NOx) 

Hot FTP 20 (SME) 6.0 0 0 -26 

23 Caterpillar 3126E 

(4 g/bhp-h NOx) 

Hot FTP 20 (SME) 0 -16 -6.7 -1.1 

5
Vehicle Testing Studies 

EPA’s review [16] also included a summary of chassis dynamometer vehicle testing 

studies. The studies reviewed included data for three transit buses and eight pickup 

trucks and the data for percent change in NOx emissions are shown in Figure 4. While a 

fitted trend line shows a negative slope (i.e., NOx emissions being reduced as biodiesel is 

blended with diesel fuel), the slope of this line is not significantly different from zero 

(p≈0.5), thus for these vehicles blending of biodiesel had no impact on NOx. 

Figure 4. Summary of NOx impact of biodiesel blending from chassis 

dynamometer studies reviewed by EPA [16]. 

A number of chassis studies have been published since the publication of EPA’s review, 

or were not included in that review. Careful review of the data in these publications 

reveals large variation in data quality, with some studies exhibiting extremely poor 

repeatability (likely because an inadequate number of control tests were conducted), or 

basing conclusions on only one or two replicate tests. Application of strict quality 

criteria, and rejection of studies that do not meet them, is required for any discussion of 

chassis testing data. 

Data from many of these studies are shown in Table 4. Clark and Lyons reported testing 

eight Class 8 tractors, ranging in model year from 1989 to 1994 on conventional diesel 

and B35 [24]. NOx emissions over the WVU 5-peak cycle decreased for two vehicles, 

increased for five vehicles and were unchanged for one vehicle. A second report from 

the same research group includes testing of additional vehicles and suggests that NOx 

emissions decrease for vehicles with early 1990s DDC engines, but increase for late 

1980s Cummins engines [25]. However, no individual vehicle results are reported in this 

study, and it is not clear if intake air humidity was controlled or measured in these tests, 

hence they are not considered further. Petersen and coworkers report test results for a 

Dodge pickup equipped with a 1994 Cummins B5.9 [26] (it is not clear if these results 

were included in EPA’s review). Biodiesel from several different sources was tested and 

6
reductions in NOx were observed in all cases for B20 blends. Three replicate tests were 

run only for the B20 produced from rapeseed ethyl ester (REE), which produced a 3.1% 

decrease in NOx. Durbin and coworkers present light-duty FTP results for testing B20 in 

seven light heavy-duty diesel vehicles with model year ranging from 1983 to 1993 [27]. 

However, this study is based on only two replicate runs with inadequate controls and thus 

will not be considered further. Finnish researchers reported testing an Audi turbocharged 

direct injected (TDI) vehicle on the light-duty FTP with B30 and adequate replication and 

controls. They observed no significant change in NOx [18]. Environment Canada tested 

three heavy-duty trucks on B20 and showed that NOx could go up or down depending on 

engine design [28]. Most recently Holden and coworkers have presented a significant 

study of on- and off-highway nontactical vehicles used at military bases [29]. All 

vehicles were tested multiple times with California Air Resources Board (CARB) diesel 

base fuel tests at regular intervals. For the study results taken as a whole, and taking into 

account only changes in emissions that are significant at 90% confidence or better, there 

was no significant impact of B20 on NOx. Results from this study are shown in Table 5. 

The results in Tables 4 and 5 for soy-derived B20 show an average change in NOx of 

1.2%±2.9% (95% confidence interval). Both the chassis studies reviewed by EPA and the 

more recent studies described here are showing no significant impact of B20 on NOx. 

Table 4. Summary of Percent Change in Emissions from Recent Vehicle Testing

Studies of Biodiesel.

Reference Engine Cycle %Biodiesel NOx HC CO PM 

26 1994 Cummins ISB UDDS 20 (REE) -3.1 -36 -37 -12 

18 Audi TDI FTP75 30 (RME) 0 -13 5.5 -22 

28 2003 Cummins ISM UDDS 20 (SME) -3.1 -8.2 -16 -20 

WVU 5 Pk 20 (SME) -2.5 -23 -19 12 

2004 MBE4000 UDDS 20 (SME) 14 -23 -19 -20 

1999 Caterpillar 

C12 UDDS 20 (SME) 3 -21 -17 -27 

WVU 5 Pk 20 (SME) 1.5 -21 -7.6 -2.9 

Another approach to vehicle testing is the use of portable emissions measurement 

systems (PEMS). These are systems that reside on board the vehicle during normal 

operation or operation on a test track, and measure concentrations of pollutants in the raw 

exhaust. EPA will use PEMS to assess in-use compliance of heavy-duty vehicles with 

emission standards beginning in the 2007 model year [30]. Several measurements of the 

impact of B20 on emissions have been conducted using PEMS. Frey and Kim reported 

on testing 12 Department of Transportation dump trucks during their normal operation in 

North Carolina [31]. These included engines from four manufacturers and model years 

from 1998 to 2004. The study measured HC, CO, and NO emissions, but not NOx 

emissions, such that emissions of NO2 are not included. On average, emissions of all 

measured pollutants decreased, with both NO and PM emissions declining by 10%. This 

strongly implies that NOx emissions also decreased because it has been shown that the 

cycle average NO2/NOx ratio does not change for B20 [23]. Researchers at Rowan 

University tested three school buses on a test track with emissions measurement by 

PEMS using a highly aggressive driving cycle developed from bus activity data [32]. The 

school buses included a 1996 Cummins B-series engine and two 1997 International 

7
engines. NOx emissions went up slightly for two buses and down slightly for the third. 

Researchers at the Texas Transportation Institute tested five school buses selected to be 

representative of the school bus fleet in Texas, on a test track using cycles derived from 

bus activity data and emissions measurement by PEMS [33]. All were equipped with inline, 6-cylinder International engines ranging in model year from 1987 to 2004. The tests 

used Texas low emissions diesel (TxLED) as the base fuel (a low aromatic, high cetane 

number fuel), biodiesel derived from soy, and a market average biodiesel blend 

(compositional details were not specified). Changes in NOx emissions were small and 

not statistically significant. 

Table 5. Summary of Percent Change in Emission Results from U.S. Navy Study 

of B20 Emission Impacts [29]. 

8
Comparison of Engine and Vehicle Test Results 

The results in EPA’s 2002 compilation of published studies suggested a discrepancy 

between engine and vehicle tests for B20. In particular, engine tests as reviewed by EPA 

indicate a 2% increase in NOx emissions for B20 while vehicle tests on average tend to 

indicate a smaller or even zero increase. However, a close examination of the data 

included in the review reveals that results are dominated by engines from a single 

manufacturer with a very limited range of model years. Nearly half of the observations 

(44%) were for DDC engines in the 1991to 1997 model year range, and a large majority 

of these are for the Series 60 model. Engine manufacturers certified more than 700 

heavy-duty engine families and 5,000 engine models in 2006 alone [34], although not all 

of these were on-highway or diesel engines. In 2002 there were more than 5 million 

medium, light-heavy, and heavy-heavy duty trucks registered in the United States [35], 

and roughly 50% were 10 years old or older. These vehicles typically stay on the road 

for 15 years or longer. We believe that EPA’s conclusion of a NOx increase is influenced 

by the unrepresentative composition of the engine dataset. A hallmark of the B20 

emission test results is that NOx is highly variable, with percentage change ranging from 

roughly -7% to +7%. Data for the DDC Series 60 engine, which typically exhibits a 

small NOx increase for B20, makes up a large fraction of the data reviewed. Therefore, 

EPA draws a conclusion that is at odds with the results of the more recent studies 

reviewed here. 

An examination of all of the published data suggests that there is no discrepancy between 

engine and vehicle testing and that for B20 on average there is no net impact on NOx. 

However, the reasons for the variability in NOx with engine model are not understood 

and are worthy of further study. It is possible that the variation is caused by differences 

in how engine fuel injection systems and electronic controls respond to the lower energy 

content or other properties of B20. 

Fundamental Studies of Biodiesel and NOx Emissions 

A combustion analysis study of biodiesel and biodiesel blends concluded that biodiesel 

blends had a shorter ignition delay than diesel alone, at both full and light load, and a 

lower premixed burn fraction at full load. However, diffusion burn rates were similar 

[36]. The shorter ignition delay, caused by biodiesel’s higher cetane number, has been 

suggested as being the cause of the NOx increase observed in many studies because the 

advanced combustion timing increases peak pressure and temperature. However, this is 

inconsistent with EPA’s review of cetane number effects, which shows decreasing NOx 

for increasing cetane number [37], although benefits are less for newer engines with more 

highly retarded injection timing. Use of cetane enhancing additives has been shown to 

reduce NOx for B20 in older, more cetane-sensitive engines [15]. 

9
A number of other hypotheses on the cause of the increase in NOx observed for biodiesel 

under some engine operating conditions have been advanced. Increasing NOx may be 

caused by an increase in flame temperature in either premixed or diffusion burn, which is 

caused by reduction in the concentration of carbonaceous soot − a highly effective heat 

radiator. The net result of the PM reduction caused by supplying oxygen to the fuel rich 

zone of the diffusion flame may be to increase flame temperature because of this loss of 

radiant heat transfer [10]. This hypothesis has been investigated by Cheng and coworkers 

using an optically accessible engine and fuels with identical ignition delay [38]. NOx 

emissions were higher for B100, even with matched ignition delay, especially at lower 

loads. Flame luminosity measurement suggested less radiation from the B100 flame, 

particularly under light load conditions where NOx was shown to increase. 

The double bonds present in biodiesel may cause a higher adiabatic flame temperature, 

and hence a higher temperature at the flame front in the diffusion flame. This hypothesis 

is consistent with results showing higher levels of NOx emissions for biodiesel from more 

highly unsaturated feedstocks [14]. Cheng and coworkers present results of equilibrium 

calculations that refute this hypothesis [38]. However, Ban-Weiss and coworkers 

performed calculations of adiabatic flame temperature based on chemical kinetic models 

that suggest a significant impact of unsaturation [39]. 

A second fuel chemistry effect might be enhancement of the formation of prompt (or 

Fenimore) NO, which can account for up to 30% of NOx formation [40]. Prompt NO is 

formed by reaction of radical HC species with nitrogen, ultimately leading to formation 

of NO. Hess and coworkers noted that unsaturated compounds may form higher levels of 

radicals during pyrolysis and combustion, and investigated the potential of radical 

scavenging antioxidant additives for NOx reduction [41]. Some, but not all, antioxidants 

were shown to reduce NOx emissions for their engine. 

Van Gerpen and collaborators have shown that NOx can increase as a result of a shift in 

fuel injection timing caused by different mechanical properties of biodiesel [42, 43]. 

Biodiesel has a higher bulk modulus of compressibility (or speed of sound) than 

petroleum diesel and this was proposed to cause a more rapid transfer of the fuel pump 

pressure wave to the injector needle. This caused earlier needle lift and a small advance 

in injection timing that was proposed to account for a fraction of the NOx increase 

observed under some conditions. Sybist and Boehman also examined this effect [44]. 

They found that soy B100 produces a 1° advance in injection timing and a nearly 4° 

advance in the start of combustion. The bulk modulus effect appears to be applicable to 

pump-line nozzle and unit injection systems, but not for high-pressure common rail 

systems where “rapid transfer of a pressure wave” does not occur. 

A number of more speculative hypotheses have been proposed. For example, reduction 

of the soot concentration in the flame may eliminate NO-carbon reactions. The 

importance of NO-carbon reactions in diesel combustion is unknown. Also, biodiesel has 

been shown to alter injection duration, spray properties, and other aspects of spray fluid 

flow [44]. The impact of these phenomena on NOx emissions in this context is uncertain. 

10
These studies indicate that there may be more than one factor contributing to the effect of 

biodiesel on NOx. Furthermore, which factor is dominant may change with engine speed 

and load or with certain engine design parameters. Given the results of chassis and 

engine tests reviewed in previous sections, fundamental studies of biodiesel’s impact on 

NOx may be most relevant to B100, where it seems clear that an increase in NOx occurs 

in most cases. Additional study is required to quantitatively understand the underlying 

factors causing biodiesel’s impact on NOx. Future studies should include a comparison of 

results from engine operating conditions where NOx increases and where it does not. 

11
Methodology 

Vehicle Emissions Test Lab 

All testing was conducted on a heavy-duty chassis dynamometer at NREL’s ReFUEL test 

facility. The chassis dynamometer test facility includes analytical equipment for 

emissions and fuel economy measurements of on-road heavy-duty diesel vehicles. All 

emissions measurements are conducted in accordance with the Code of Federal 

Regulations (CFR), title 40, part 86, subpart N. 

Chassis Dynamometer 

The chassis dynamometer, as illustrated in Figure 5, is composed of three major 

components: the rolls – which are in direct contact with the vehicle tires during testing, 

the direct current (DC) electric motor (380 hp absorbing/360 hp motoring) dynamometer, 

and the flywheels. The DC electric motor and flywheels are installed in a pit below the 

ground level, such that the only exposed part of the dynamometer is the top of the 40– 

inch-diameter rolls. Two sets of rolls are installed, so that twin-axle vehicles can be 

tested. The dynamometer can simulate up to 80,000-lb vehicles at speeds up to 60 mph. 

Figure 5. Chassis Dynamometer Schematic 

The rolls are the means by which power is absorbed from the vehicle. The rolls are 

attached to gearboxes that increase the speed of the central shaft by a factor of 5. The 

flywheels, mounted on the back of the dynamometer, provide a mechanical simulation of 

the vehicle inertia. 

The energy absorption capability of the dynamometer is used to apply the road load, 

which is a summation of the aerodynamic drag and friction losses that the vehicle 

experiences, as a function of speed. The road load for each test vehicle was estimated 

from standard equations. The electric dynamometer is also used to adjust the simulated 

inertia, either higher or lower than the 31,000-lb base dynamometer inertia. The inertia 

simulation range of the chassis dynamometer is 8,000 to 80,000 lbs. 

The test vehicle is secured with the drive axles over the rolls. A driver’s aid monitor in 

the cab is used to guide the vehicle operator in driving the test trace. A large fan is used 

to cool the vehicle radiator during testing. The chassis dynamometer is supported by 72 

channels of data acquisition, in addition to the emissions measurement, fuel metering, 

and combustion analysis subsystems. 

12
With the vehicle jacked up off the rolls, an automated dynamometer warm-up procedure 

is performed daily, prior to testing, to ensure that parasitic losses in the dynamometer and 

gearboxes have stabilized at the appropriate level to provide repeatable loading. An 

unloaded coast-down procedure is also conducted to confirm that inertia and road load 

are being accurately simulated by the dynamometer control system. Between test runs a 

loaded coast-down procedure is performed to further ensure stability of vehicle and 

dynamometer parasitic losses and accurate road load simulation during testing. 

Fuel Handling 

Fuel supply from the vehicle’s tank is interrupted, allowing for delivery of conditioned 

and metered fuel to the test vehicle. Test fuels are stored and blended, in drum quantities, 

in a temperature-conditioned shed. Test fuels are blended gravimetrically to the 20 

volume percent level (B20). The fuel is delivered from the supply drum to the fuel 

metering and conditioning system, from which fuel is supplied to the vehicle’s fueling 

system. The fuel metering system measures volumetric flow to an accuracy of +/- 0.5% 

of the reading. An in-line sensor measures the density with an accuracy of +/- 0.001 g/cc, 

allowing an accurate mass measurement over the test cycle. 

Air Handling and Conditioning 

Dilution air and the air supplied to the test vehicle for combustion are derived from a 

common source, a roof-mounted system that conditions the temperature of the air and 

humidifies as needed to meet desired specifications. This air is passed through a HEPA 

filter, in accordance with the (2007) CFR specifications, to eliminate background PM as a 

source of uncertainty in particulate measurements. The average inlet air temperature to 

the vehicle was maintained within a window of 24oC +/- 2oC for all test runs, and average 

humidity was controlled to 75 grains/lb (absolute) +/- 4 grains/lb. 

Emissions Measurement 

The emissions measurement system is based on the full-scale exhaust dilution tunnel 

method with a Constant Volume Sampling (CVS) system for mass flow measurement. 

The system is designed to comply with the requirements of the 2007 Code of Federal 

Regulations, title 40, part 86, subpart N. Exhaust from the vehicle flows through 

insulated piping to the full-scale 18-inch-diameter stainless steel dilution tunnel. A static 

mixer ensures thorough mixing of exhaust with conditioned, filtered, dilution air prior to 

sampling of the dilute exhaust stream to measure gaseous and particulate emissions. 

A system with three Venturi nozzles is employed to maximize the flexibility of the 

emissions measurement system. Featuring 500-cfm, 1,000-cfm, and 1,500-cfm Venturi 

nozzles and gas-tight valves, the system flow can be varied from 500-cfm to 3,000-cfm 

flow rates in 500-cfm increments. This allows the dilution level to be tailored to the 

engine size being tested, maximizing the accuracy of the emissions measurement 

equipment. 

The gaseous emissions bench is a Pierburg model AMA-2000. It features continuous 

analyzers for total HC, NOx, CO, carbon dioxide (CO2) and oxygen (O2). The system 

features auto-ranging, automated calibration, zero check and span check features, as well 

13
as integration functions for calculating cycle emissions. There are two heated sample 

trains for gaseous emissions measurement: one for HC, and another for the other gaseous 

emissions. NOx and HC measurements are performed on a wet basis, while CO, CO2 and 

O2, are done on a dry basis. Sample probes are located in the same plane in the dilution 

tunnel. 

The PM sample control bench maintains a desired sample flow rate through the PM 

filters in proportion to the overall CVS flow, in accordance with the CFR. Stainless steel 

filter holders designed to the 2007 CFR requirements house 47-mm-diameter Teflon 

membrane filters through which the dilute exhaust sample flows. 

The PM sampling system is capable of drawing a sample directly from the large full-scale 

dilution tunnel or utilizing secondary dilution to achieve desired temperature, flow, and 

concentration characteristics. A cyclone separator, as described in the CFR requirements, 

is employed to mitigate tunnel PM artifacts. PM filters are handled, conditioned, and 

weighed in a Class 1000 clean room with precise control over the temperature and 

humidity (+/- 1°C for temperature and dew point). The microbalance for weighing PM 

filters features a readability of 0.1 μg (a CFR requirement), a barcode reader for filter 

identification and tracking, and a computer interface for data acquisition. The 

microbalance is installed on a specially designed table to eliminate variation in the 

measurement due to vibration. 

Test Vehicles 

This study includes data collected from chassis dynamometer testing of eight different 

heavy-duty on-road vehicles. Test vehicles included three transit buses, two school 

buses, two Class 8 trucks, and one motor coach. This collection of test vehicles captures 

a variety of engine makes, sizes, emissions control technologies and transmission types, 

but still cannot be considered as representative of on-road heavy-duty vehicles. Engine 

model year varied from 2000 to 2006. Accumulated mileage also varied for each of the 

test vehicles, ranging from 2,274 to 503,468 miles. Information detailing each of the test 

vehicles is provided in Table 6. 

The three transit buses incorporated identical engine and transmission combinations, only 

differing in the accumulated mileage and biodiesel fuel type. This allowed for some 

assessment of the dependence of emission differences on vehicle-to-vehicle and fuel-tofuel variability. 

14
Table 6. Description of Vehicles Tested. 

Motor Coach Freightliner 

Class 8 

Conventional 

School Bus 

Green 

Diesel 

School Bus 

International 

Class 8 

Transit Bus #1 Transit 

Vehicle MY Jan-04 May-99 Jul-04 Jan-06 Jan-06 Sep-00 SepMake Sports Coach 

37' 

Freightliner International International International Orion Orio

Odometer 33,320 503,468 30,441 2,274 3,165 136,610 205,Test Weight 23,500 64,000 26,000 26,000 64,000 35,000 35,0Engine Manufacturer 

Cummins Detroit 

Diesel 

International International Cummins Cummins Cumm

Displacement 5.9 L 12.7 L 7.6 L 7.6 L 10.8 L 10.8 L 10.8 Engine MY 2003 2000 2004 2006 2005 2000 200Engine Model ISB 300 Series 60 D 285 DG 285 ISM 330 ISM 280 ISM Rated HP 300 470 285 285 330 280 28Test Fuels: Certification, 

B20 Agland 

Certification, 

B20 

Certification, 

B20 

Certification, 

B20 

#2 Diesel, B20 #2 Diesel, B20 #2 Dies

Petroleum 2007 Cert 2007 Cert 2007 Cert 2007 Cert Local LSD C Local LSD A Local LBiodiesel Agland Agland Agland Agland Agland BlueSun BlueS

Transmission Type 

Allison Auto Rockwell 

10spd 

Manual 

Allison Auto Allison Auto Eaton 10spd 

Manual 

Friedrichshafen Friedrich

Aftertreatment DOC DPF 

15
Driving Cycles 

Several different driving cycles were employed in this study. Driving cycles were chosen 

to mimic in-use operation for a given vehicle. The City-Suburban Heavy-Vehicle Cycle 

(CSHVC) was used for testing all but one of the vehicles in this study. This cycle, 

developed by West Virginia University (WVU), represents low-speed, stop-and-go 

driving events [45] and is shown in Figure 6. The Urban Dynamometer Driving 

Schedule for Heavy-Duty Vehicles (UDDS) was also employed. This cycle was 

developed from the same dataset used for development of the transient test portion of the 

heavy-duty FTP and is described in the Code of Federal Regulations [46], shown in 

Figure 7. 

The Combined International Local and Commuter Cycle (CILCC) was developed by 

NREL for testing Class 4 to 6 hybrid electric delivery vehicles [47]. The only part of the 

cycle that is specific to hybrids is the length (>45 min). Otherwise, it is intended to 

simulate urban delivery driving for heavy-duty vehicles in general. The cycle was 

developed to use larger amounts of fuel energy so that changes in state of charge (battery 

energy) would be minimal in comparison. The acceleration events of this cycle were 

slightly modified to allow the Class 8 vehicle to achieve the drive trace; the cycle used is 

shown in Figure 8. 

The Rowan University Composite School Bus Cycle (RUCSBC) [32], shown in Figure 9, 

was developed from school bus activity data. Note that the RUCSBC has the highest 

average and maximum acceleration rates and is therefore the most aggressive of these 

driving cycles. The Freeway Cycle [45] was developed from activity data on two heavyduty trucks and includes four-lane highway driving with entrance and exit ramps, shown 

in Figure 10. The Freeway cycle has the highest average and maximum speed, and the 

longest distance. Cycle statistics for each of the drive cycles are shown in Table 7. The 

chosen drive cycles are representative of a wide range of driving styles, including high 

speed interstate driving to low-speed, stop-and-go driving. 

Table 7. Cycle Statistics for Various Driving Cycles Used in this Study. 

CSHVC UDDS CILCC mod RUCSBC Freeway 

Total Time (sec) 

Time at Idle (%) 

Average Cycle Speed (mph) 

Average Speed While Driving 

(mph)

Maximum Speed (mph) 

Total Distance (mi) 

Number of Stops (stops/mi) 

Average Acceleration Rate 

(ft/sec2

)

Maximum Acceleration Rate 

(ft/sec2

)

1,700 

23.24 

14.15 

 18.44 

43.8 

6.68 

1.95 

1.31 

3.81 

1,060 

36.32 

18.81 

29.56 

58 

5.54 

1.26 

1.57 

6.01 

3,192 

15.57 

14.25 

16.89 

55 

12.64 

1.98 

1.44 

3.67 

1,310 

21.15 

20.95 

26.59 

49.7 

7.63 

1.44 

2.1 

12.17 

1,640 

9.27 

34.03 

37.52 

60.7 

15.51 

0.58 

0.67 

4.69 

16 
50 

60 

70 

speed (

mph) speed (mph) 40 

30

20

10

0 

0 200 400 600 800 1000 1200 1400 1600

time (sec) 

Figure 6. The CSHVC cycle. 

70

60

50

40

30

20

10

0 

0 200 400 600 800 1000

time (sec) 

Figure 7. The UDDS cycle. 

17
speed (

mph) speed (

mph) 70 

60

50

40

30

20

10

0 

0 500 1000 1500 2000 2500 3000 3500

time (sec) 

Figure 8. The CILCC modified cycle. 

70

60

50

40

30

20

10

0 

0 200 400 600 800 1000 1200

time (sec) 

Figure 9. The RUCSBC cycle. 

18
70 

60 

50 

40

speed (

mph) 30 

20 

10 

0 

0 200 400 600 800 1000 1200 1400 1600 

time (sec) 

Figure 10. The Freeway cycle. 

Test Fuels 

Each vehicle was tested with a petroleum-derived diesel fuel and a 20% blend of soybased biodiesel blended with the petroleum diesel base fuel (B20). In each case the B20 

was splash blended on a volumetric basis. Two supplies of the soy-based biodiesel were 

used: a standard commercial grade fuel supplied by Agland, and a specialized biodiesel 

containing a proprietary multifunctional additive package supplied by BlueSun Biodiesel. 

Four separate supplies of petroleum diesel were used. Three on-highway low-sulfur 

diesels (LSD) were obtained locally, with LSD A and LSD B obtained from the local bus 

company at different times. LSD C was obtained from a local fuel jobber. The fourth 

fuel was ultra low sulfur 2007 certification diesel (2007 Cert) obtained from 

ChevronPhillips. Properties of these test fuels are listed in Table 8, while Table 6 notes 

which fuels were tested in each vehicle. The B20 blends were prepared using a highly 

accurate gravimetric procedure. Note that aromatic content is not reported for the B20 

blends because the method used to measure fuel aromatic content, ASTM D1319, gives 

false high values for biodiesel and biodiesel blends. The aromatic content of B100 is 

zero, thus B20 blends will have 20% lower aromatic content than the diesel fuel in which 

they are blended. 

19
Table 8. Properties of Test Fuels. 

LSD A B20 

LSD A/ 

BlueSun 

LSD B B20 

LSD B/ 

Agland 

LSD C B20 

LSD C/ 

Agland 

2007 

Cert 

B20 

Cert/ 

Agland 

Distillation T90, oC (D86) 325 340 310 331 316 333 299 327 

Flash Point, oC (D93) 66 71 59 63 58 64 82 81 

Copper Corrosion (D130) 1a 1a 1a 1a 1a 1a -- 1a 

Kinematic Viscosity, cSt@40oC 

(D445) 

2.438 2.726 2.247 2.548 2.382 2.687 2.3 2.527 

Ash, %Mass (D482) <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 

Carbon Residue, %mass (D524) 0.04 <0.010 0.11 0.08 0.13 0.11 -- 0.09 

Cetane Number (D613) 40.6 47 44.4 45.8 47.0 52.3 41 47.3 

Cloud Point, oC (D5773) -18 -14 -20 -28 -17 -13 -- -19 

Total Sulfur, ppm (D5453) 364 280 320 264 304 245 12 8.6 

Water & Sediment, %Vol (D2709) 0.010 0.010 0.01 0.01 0.010 0.010 -- 0.010 

Aromatics, %Vol (D1319) -- 28.5 25.0 -- 23.8 -- 28.8 -- 

Acid Number, mg KOH/gram 

(D664) 

0.01 0.16 <0.05 <0.05 <0.05 <0.05 -- <0.05 

Peroxide Number, ppm (D3703) 0 8.1 2.6 24.8 0 39.0 -- 57.7 

20
Results 

Average results for each vehicle and drive cycle are shown in Tables 9 through 22. 

Percent differences as a result of biodiesel are also shown. Graphical representations of 

relative NOx, PM, CO and HC emissions for each vehicle and drive cycle are shown in 

Figures 11 through 14. All results are averages of three or more individual runs, and a 

tabulation of individual run results is found in the Appendix. 

Transit Bus Results 

Data showing average emissions and fuel economy results for the three transit buses 

tested on the CSHVC are in Tables 9 through 12. Buses #1 and #2 were initially tested as 

part of a fleet evaluation project with the goal of measuring the effect of biodiesel usage 

with the actual in-use fuels [48]. Thus, these buses were tested on LSD A used by the 

bus company and the same fuel blended with soy biodiesel obtained from BlueSun 

Biodiesel and containing a proprietary multifunctional diesel additive. Both exhibit the 

roughly 2% fuel economy reduction expected for B20 based on fuel volumetric energy 

content. NOx was reduced by 5.8% for bus #1 and by 3.9% for bus #2. To determine if 

the multifunctional additive was responsible for the NOx reduction, a third, identical bus 

was tested using LSD A and biodiesel from BlueSun containing the additive LSD B with 

biodiesel from a second source (Agland) with no additive. These results are shown in 

Tables 11 and 12. Biodiesel from both sources produced a roughly 3 to 4% reduction in 

NOx, suggesting that the NOx reduction occurs generally for biodiesel for this enginetransmission combination on this drive cycle. However, because the base fuels are not 

identical, this is not a definitive comparison. All changes in NOx are significant at 95% 

confidence or better. PM emission reductions were in the 15 to 20% range for all three 

buses with all changes significant at 90% confidence or better. 

21
Table 9. Emission Test Results for Transit Bus #1 on CSHVC Comparing LSD A 

and B20/BlueSun Biodiesel. 

NOx PM CO THC Fuel Econ Fuel Cons 

(g/mile) (g/mile) (g/mile) (g/mile) (mpg) (g/mile) 

Diesel 19.80 0.2740 3.60 0.871 4.67 688 

95% conf 0.34 0.0333 0.31 0.071 0.07 11 

B20 18.65 0.2264 2.63 0.625 4.56 708 

95% conf 0.15 0.0195 0.22 0.080 0.08 9 

% Difference -5.8% -17.4% -26.8% -28.3% -2.2% 2.9% 

p-value 0.0001 0.0363 0.0006 0.0011 0.0809 0.0214 

Table 10. Emission Test Results for Transit Bus #2 on CSHVC Comparing LSD A 

and B20/BlueSun Biodiesel. 

NOx PM CO THC Fuel Econ Fuel Cons 

(g/mile) (g/mile) (g/mile) (g/mile) (mpg) (g/mile) 

Diesel 19.44 0.3210 3.43 0.794 4.54 709 

95% conf 0.41 0.1170 0.47 0.065 0.13 21 

B20 18.67 0.2150 2.73 0.571 4.45 730 

95% conf 0.26 0.0393 0.32 0.022 0.09 15 

% Difference -3.9% -33.0% -20.3% -28.0% -2.0% 3.0% 

p-value 0.0073 0.0832 0.0276 0.0001 0.2635 0.1304 

Table 11. Emission Test Results for Transit Bus #3 on CSHVC Comparing LSD A 

and B20/BlueSun Biodiesel. 

NOx PM CO THC Fuel Econ Fuel Cons 

(g/mile) (g/mile) (g/mile) (g/mile) (mpg) (g/mile) 

Diesel 19.78 0.3079 3.04 0.824 4.60 695 

95% conf 0.17 0.0267 0.14 0.018 0.02 3 

B20 19.04 0.2447 2.48 0.592 4.51 715 

95% conf 0.15 0.0125 0.18 0.046 0.04 7 

% Difference -3.7% -20.5% -18.6% -28.1% -1.9% 2.8% 

p-value 0.0001 0.0018 0.0007 0.0001 0.0044 0.0005 

Table 12. Emission Test Results for Transit Bus #3 on CSHVC Comparing LSD B 

and B20/Agland Biodiesel. 

NOx PM CO THC Fuel Econ Fuel Cons 

(g/mile) (g/mile) (g/mile) (g/mile) (mpg) (g/mile) 

Diesel 20.24 0.2805 3.07 0.824 4.59 696 

95% conf 0.26 0.0252 0.26 0.017 0.04 6 

B20 19.70 0.2324 2.70 0.659 4.50 716 

95% conf 0.28 0.0100 0.17 0.049 0.04 6 

% Difference -2.7% -17.2% -11.9% -20.0% -1.9% 2.8% 

p-value 0.0185 0.0109 0.0423 0.0001 0.0124 0.0014 

22 
Class 8 Truck Results 

Results for the International Class 8 truck are shown in Tables 13 and 14. This vehicle 

was tested as a baseline vehicle for a heavy-duty hybrid electric vehicle study. Thus the 

CILCC, which was developed to simulate urban driving generally but with features 

designed to exercise hybrid vehicles, was used. Additionally, the Freeway cycle was 

used so that both city and freeway driving were simulated. This vehicle exhibited no 

significant change in NOx for the stop and go CILCC but a 2.3% increase in NOx for 

freeway driving (p<0.05). PM emission reductions on both cycles were quite high, on the 

order of 30%. Fuel economy reduction was the expected 2% on the CILCC but only 

0.5% on the Freeway cycle. 

Results for the Freightliner Class 8 truck are shown in Tables 15 and 16. This vehicle 

was tested exclusively for this study of biodiesel emissions and the CSHVC and Freeway 

cycles were employed. NOx emissions increased 2.1% and 3.6% on these cycles, 

respectively (p<0.05). PM emission reductions were in the 20 to 25% range. Fuel 

economy reduction was about 1.5% on both cycles. 

Table 13. Emission Test Results for International Class 8 on CILCCmod 

Comparing LSD C and B20/Agland Biodiesel.

NOx PM CO THC Fuel Econ Fuel Cons 

(g/mile) (g/mile) (g/mile) (g/mile) (mpg) (g/mile) 

Diesel 11.04 0.2890 4.98 1.192 4.32 740 

95% conf 0.14 0.0083 0.19 0.032 0.05 12 

B20 11.03 0.2103 4.22 0.992 4.22 762 

95% conf 0.19 0.0052 0.09 0.034 0.04 7 

% Difference -0.1% -27.2% -15.3% -16.8% -2.3% 2.9% 

p-value 0.9528 0.0001 0.0020 0.0011 0.0402 0.0429 

Table 14. Emission Test Results for International Class 8 on Freeway Cycle 

Comparing LSD C and B20/Agland Biodiesel.

NOx PM CO THC Fuel Econ Fuel Cons 

(g/mile) (g/mile) (g/mile) (g/mile) (mpg) (g/mile) 

Diesel 6.75 0.2163 2.13 0.515 5.44 586 

95% conf 0.02 0.0104 0.04 0.003 0.02 3 

B20 6.90 0.1412 1.82 0.452 5.41 594 

95% conf 0.10 0.0010 0.03 0.009 0.03 3 

% Difference 2.3% -34.7% -14.5% -12.4% -0.5% 1.4% 

p-value 0.0340 0.0001 0.0002 0.0002 0.2410 0.0180 

23
Table 15. Emission Test Results for the Freightliner Class 8 on CSHVC 

Comparing 2007 Certification Diesel and B20/Agland Biodiesel.

NOx PM CO THC Fuel Econ Fuel Cons 

(g/mile) (g/mile) (g/mile) (g/mile) (mpg) (g/mile) 

Diesel 29.65 1.8303 27.41 0.536 3.49 913 

95% conf 0.40 0.2139 1.51 0.022 0.04 11 

B20 30.26 1.4761 24.49 0.454 3.44 935 

95% conf 0.32 0.0821 20.3 0.019 0.04 12 

% Difference 2.1% -19.4% -10.7% -15.2% -1.5% 2.4% 

p-value 0.0412 0.0129 0.0867 0.0003 0.1283 0.0253 

Table 16. Emission Test Results for the Freightliner Class 8 on the Freeway Cycle 

Comparing 2007 Certification Diesel and B20/Agland Biodiesel.

NOx PM CO THC Fuel Econ Fuel Cons 

(g/mile) (g/mile) (g/mile) (g/mile) (mpg) (g/mile) 

Diesel 22.27 0.4826 8.14 0.200 5.90 539 

95% conf 0.36 0.0650 0.29 0.013 0.03 3 

B20 23.08 0.3563 7.58 0.168 5.81 553 

95% conf 0.37 0.0219 0.12 0.014 0.03 2 

% Difference 3.6% -26.2% -6.9% -16.0% -1.6% 2.6% 

p-value 0.0124 0.0048 0.0058 0.0095 0.0007 0.0001 

Motor Coach Results 

The motor coach (or recreational vehicle) was tested on the CSHVC and UDDS cycles. 

This vehicle exhibited a roughly 3% increase in NOx and 30% reduction in PM for both 

cycles. Fuel economy reduction was roughly 1%. 

Table 17. Emission Test Results for the Motor Coach on CSHVC Comparing 2007 

Certification Diesel and B20/Agland Biodiesel. 

NOx PM CO THC Fuel Econ Fuel Cons 

(g/mile) (g/mile) (g/mile) (g/mile) (mpg) (g/mile) 

Diesel 7.75 0.2538 4.05 0.228 6.63 485 

95% conf 0.11 0.0179 0.31 0.019 0.03 2 

B20 7.96 0.1825 3.15 0.195 6.54 495 

95% conf 0.13 0.0058 0.15 0.007 0.03 3 

% Difference 2.8% -28.1% -22.3% -14.5% -1.3% 2.0% 

p-value 0.0368 0.0001 0.0005 0.0092 0.0048 0.0002 

24
Table 18. Emission Test Results for the Motor Coach on the UDDS Comparing 

2007 Certification Diesel and B20/Agland Biodiesel. 

NOx PM CO THC Fuel Econ Fuel Cons 

(g/mile) (g/mile) (g/mile) (g/mile) (mpg) (g/mile) 

Diesel 6.99 0.2387 3.66 0.138 7.05 456 

95% conf 0.10 0.0079 0.18 0.014 0.18 12 

B20 7.22 0.1672 2.95 0.133 7.00 462 

95% conf 0.19 0.0128 0.09 0.019 0.09 6 

% Difference 3.4% -30.0% -19.2% -3.4% -0.6% 1.4% 

p-value 0.0576 0.0001 0.0001 0.6993 0.6734 0.3700 

School Bus Results 

The two school buses tested in this study were the only vehicles equipped with exhaust 

aftertreatment devices. The conventional International school bus was equipped with a 

diesel oxidation catalyst and the International Green Diesel school bus was equipped with 

a diesel particle filter (DPF). Results for the Green Diesel school bus are shown in 

Tables 19 and 20 for the CSHVC and the highly aggressive RUCSBC, respectively. NOx 

emissions were essentially unchanged on the CSHVC but increased by 2.3% for the 

RUCSBC. The DPF was highly effective at reducing PM emissions with values below 

0.002 g/mile in all cases. This is roughly a factor of 100 below PM emissions measured 

for the other vehicles in this study. While examination of percent change in PM 

emissions for B20 suggests that PM has increased, the actual magnitude of these changes 

is extremely small and not statistically significant (p>0.05). Fuel economy was decreased 

by 1 to 2% for B20 in this vehicle. 

Results for the conventional school bus are shown in Tables 21 and 22. This bus 

exhibited much more highly variable emissions than any of the other vehicles tested, 

reducing our ability to make definitive statements about emission differences. 

Examination of individual run results in the Appendix indicates some difficulty in 

controlling intake air humidity for this test sequence, but also shows large shifts in PM 

emissions with no apparent cause. Results are no change in NOx for the CSHVC but a 

6.2% increase for the RUCSBC. PM emissions were unchanged for the CSHVC but 

decreased by 24% for the RUCSBC. Fuel economy declined by up to 1%. 

Table 19. Emission Test Results for the International Green Diesel School Bus on 

CSHVC Comparing 2007 Certification Diesel and B20/Agland Biodiesel. 

NOx PM CO THC Fuel Econ Fuel Cons 

(g/mile) (g/mile) (g/mile) (g/mile) (mpg) (g/mile) 

Diesel 7.70 0.0009 0.15 0.023 5.86 549 

95% conf 0.14 0.0002 0.07 0.015 0.06 6 

B20 7.64 0.0012 0.12 0.031 5.74 565 

95% conf 0.09 0.0001 0.05 0.008 0.06 6 

% Difference -0.8% 28.0% -15.9% 35.2% -2.0% 2.8% 

p-value 0.5484 0.1032 0.5158 0.7179 0.0328 0.0051 

25 
Table 20. Emission Test Results for the International Green Diesel School Bus on

RUCSBC Comparing 2007 Certification Diesel and B20/Agland Biodiesel.

NOx PM CO THC Fuel Econ Fuel Cons 

(g/mile) (g/mile) (g/mile) (g/mile) (mpg) (g/mile) 

Diesel 8.93 0.0014 0.10 0.023 4.97 648 

95% conf 0.08 0.0002 0.03 0.005 0.03 4 

B20 9.14 0.0017 0.06 0.021 4.93 659 

95% conf 0.16 0.0003 0.02 0.009 0.04 5 

% Difference 2.3% 15.6% -41.7% -7.0% -0.8% 1.7% 

p-value 0.0346 0.2209 0.0547 0.7331 0.1561 0.0081 

Table 21. Emission Test Results for the International Conventional School Bus on

CSHVC Comparing 2007 Certification Diesel and B20/Agland Biodiesel.

NOx PM CO THC Fuel Econ Fuel Cons 

Diesel 

(g/mile) 

9.85 

(g/mile) 

0.1929 

(g/mile) 

5.22 

(g/mile) 

0.439 

(mpg) 

5.93 

(g/mile) 

534 

95% conf 0.10 0.0210 0.37 0.041 

6 

0.04 3 

B20 9.79 0.1977 5.72 0.434 5.86 549 

95% conf 0.12 0.0176 0.46 0.047 0.03 3 

% Difference -0.7% 2.5% 9.5% -1.1% -1.1% 2.7% 

p-value 0.4145 0.7368 0.1198 0.8802 0.0074 0.0001 

Table 22. Emission Test Results for the International Conventional School Bus on

RUCSBC Comparing 2007 Certification Diesel and B20/Agland Biodiesel.

NOx PM CO THC Fuel Econ Fuel Cons 

(g/mile) (g/mile) (g/mile) (g/mile) (mpg) (g/mile) 

Diesel 9.78 0.6954 8.95 0.373 5.01 633 

95% conf 0.12 0.0324 0.49 0.074 0.03 4 

B20 10.39 0.5284 6.93 0.300 4.99 645 

95% conf 0.17 0.0393 1.12 0.100 0.05 6 

% Difference 6.2% -24.0% -22.6% -19.6% -0.3% 1.9% 

p-value 0.0001 0.0001 0.0014 0.2665 0.5937 0.0049 

Results Summary 

Figures 11 through 14 summarize the results for NOx, PM, CO, and HC (or total 

hydrocarbon, THC), respectively. As can be seen in the data, not only is the impact of 

B20 on NOx emissions highly dependent on the test vehicle, but it is also dependent on 

the chosen drive cycle. All three of the transit buses demonstrated reductions in NOx 

emissions, regardless of biodiesel supply. The motor coach and the Freightliner Class 8 

truck both showed increases in NOx emissions over each of their test cycles. The 

International Class 8 and both school buses showed increases over one test cycle, and 

reductions or no change over the other test cycle. However, PM emission reductions are 

26
quite robust, independent of technology and driving cycle with the exception of the DPFequipped vehicle. 

Figure 11. Comparison of NOx emissions for conventional diesel and B20 for each 

vehicle tested and each cycle. 

Figure 12. Comparison of PM emissions for conventional diesel and B20 for each 

vehicle tested and each cycle. 

27
Figure 13. Comparison of CO emissions for conventional diesel and B20 for each 

vehicle tested and each cycle. 

Figure 14. Comparison of THC emissions for conventional diesel and B20 for 

each vehicle tested and each cycle. 

28
Discussion 

The average percent change in emissions and fuel economy for each vehicle and drive 

cycle are summarized in Table 23. Note that for Transit Bus #3 results for both B20A 

and B20B have been averaged so that this vehicle is not counted twice in the average. 

Across all vehicle/drive cycle combinations PM, CO and THC showed average 

reductions of 16.4%, 17.1%, and 11.6% respectively. NOx increased on average by 

0.6%. Fuel economy was reduced by an average of 1.4%. Table 23 also shows 95% 

confidence limits for these average values. Note that the confidence interval for NOx 

emissions includes zero, or no change in NOx. It is important to keep in mind, however, 

that this eight-vehicle dataset cannot in any way be considered as representative of in-use 

heavy-duty vehicles, or even of model year 2000 to 2006 vehicles. Nevertheless, the 

results confirm the robustness of PM, CO, and HC reductions found in most other 

studies, and support the conclusion that the impact of B20 on NOx is not significant. 

Additionally, if the results in Table 23 are combined with the soy B20 results from Tables 

4 and 5, the average change in NOx is 0.9%±1.5% (95% confidence interval). 

Table 23. Average Percent Change in Emissions and Fuel Economy for All

Vehicles Tested.

Vehicle 

Transit Bus #1 

Cycle 

CSHVC 

NOx % 

Change 

-5.8 

PM % 

Change 

-17.4 

CO % 

Change 

-26.8 

THC % 

Change 

-28.3 

Fuel Econ 

% Change 

-2.2 

Transit Bus #2 CSHVC -3.9 -33.0 -20.3 -28.0 -2.0 

Transit Bus #3 

(Average) CSHVC -3.2 -18.9 -15.3 -25.1 -1.9 

Freightliner CSHVC 2.1 -19.4 -10.7 -15.2 -1.5 

Class 8 Freeway 3.6 -26.2 -6.9 -16.0 -1.6 

CSHVC 2.8 -28.1 -22.3 -14.5 -1.3 

Motor Coach 

UDDS 3.4 -30.0 -19.2 -3.4 -0.6 

International CILCCmod -0.1 -27.2 -15.3 -16.8 -2.3 

Class 8 Freeway 2.3 -34.7 -14.5 -12.4 -0.5 

Green Diesel CSHVC -0.8 28.0 -15.9 35.2 -2.0 

School Bus RUCSBC 2.3 15.6 -41.7 -7.0 -0.8 

Conventional CSHVC -0.7 2.5 9.5 -1.1 -1.1 

School Bus RUCSBC 6.2 -24.0 -22.6 -19.6 -0.3 

Overall Average % Difference 0.6 -16.4 -17.1 -11.6 -1.4 

95% Confidence Interval ±1.8 ±10 ±6.1 ±8.6 ±0.36 

29
Table 24 shows average change in emissions and fuel economy for subsets of the overall 

dataset. The vehicles tested include four meeting the 4-g/bhp-h NOx requirement that 

went into effect in 1998, and four meeting the 2.5-g/bhp-h NOx+HC requirement that 

went into effect in 2004 (or as early as 2002 for some manufacturers). The first two rows 

of Table 24 examine average emission changes for B20 in vehicles from these two 

technology groups. The most obvious observation is the reduction in NOx observed for 

the 4-g/bhp-h engines compared to the increase observed for 2.5-g/bhp-h engines. 

However, three out of the four 4-g/bhp-h NOx vehicles were identical transit buses. 

Comparisons made with this subset of vehicles may therefore not be applicable to 

4-g/bhp-h NOx vehicles in general and again highlight the fact that this small group of 

vehicles is not a representative sample. 

Table 24. Average Percent Change in Emissions for Specific Subsets of the Total 

Dataset, 95% Confidence Interval is Shown. 

Vehicle NOx % PM % CO % THC % Fuel Econ 

Cycle Change Change Change Change % Change 

4.0-g/bhp-h Engines Only -1.4±3.3 -23.0±5.2 -16.0±6.3 -22.3±5.1 -1.8±0.2 

2.5-g/bhp-h Engines Only 1.9±1.7 -12.2±17 -17.8±9.7 -5.0±12 -1.1±0.5 

CSHVC Only -1.4±2.2 -12.3±15 -14.5±8.2 -10.9±16 -1.7±0.3 

All but one of the vehicles was driven on the CSHVC, thus it is of interest to examine 

results for this urban/suburban driving cycle separately, and the results are shown in 

Table 24. Percent changes for the CSHVC are quite similar to the changes observed 

overall. However, for the CSHVC, NOx emissions decrease slightly. A number of other 

comparisons might be made, for example comparing emission changes for LSD versus 

ULSD, but the eight-vehicle dataset presented here is too small for meaningful 

comparisons of this type to be made. 

Examination of Real Time NOx Emissions Data 

The impact of biodiesel on NOx emissions varies with vehicle, engine technology, and 

chosen drive cycle. An analysis of real-time NOx data illustrates this impact relative to 

different driving events. Figures 15 through 19 show snapshots of real-time NOx data for 

portions of various drive traces and with different vehicles. In each case, the data is 

presented for both test fuels in order to show comparisons of how biodiesel impacts NOx 

emissions through different driving events. 

Figure 15 shows NOx traces for a portion of the CSHVC cycle driven by RTD transit bus 

#3. This is a 4.0-g/bhp-h NOx engine, thus it does not incorporate EGR for NOx control. 

NOx emissions, shown in grams/second, differ under several driving events. During idle 

portions of the drive cycle, B20 causes a significant decrease in NOx emissions. During 

most acceleration events, the peaks in NOx emissions are higher for B20, particularly at 

or just before peak speed. However, for some acceleration events NOx is lower for B20, 

especially during longer accelerations but before peak speed (i.e., 1,140 to1,150 seconds 

and 1,210 to 1,220 seconds in Figure 15). The combination of these effects causes 

30
overall NOx emissions to decrease with the use of B20 in this vehicle. The 4-g/bhp-h 

Freightliner Class 8 truck (Figure 16) shows no difference at idle or during acceleration, 

but higher NOx for B20 at speed peaks. 

Figure 17 shows real-time NOx traces for the same portion of the CSHVC cycle, driven 

by the motor coach. This is a 2.5-g/bhp-h NOx engine, thus incorporating EGR. As can 

be seen, NOx emissions at the idle conditions are controlled to nearly zero grams/second, 

thus there is no difference in NOx emissions between the two fuels. However, this 

vehicle still experiences the higher peaks in NOx emissions with B20 under acceleration 

events or near peak speed, leading to an overall increase in NOx emissions. 

Figure 18 shows the real-time NOx traces for the International Class 8 Truck driven over 

the CILCC drive cycle. Like the motor coach, this vehicle also incorporates a 2.5­

g/bhp-h NOx engine. However, this engine shows slight decreases in the NOx peaks 

during the acceleration events. NOx emissions during steady-state and idle operation are 

the same. The overall NOx emissions for the International Class 8 truck on this drive 

cycle showed slight reductions with B20, but not with statistical confidence (p = 0.9528). 

These results do not reveal any obvious, consistent factor that is causing the variability 

observed for NOx with these vehicles. A much more detailed analysis will be required. 

In particular we recommend an analysis that examines factors such as acceleration rate, 

wheel horsepower, and rate of change of horsepower. A study that employs a 

transmission model to estimate engine torque at various driving conditions may also 

prove valuable [49]. 

Figure 15. Portions of the CSHVC real-time NOx traces for RTD Transit Bus #3. 

31
Figure 16. Portions of the CSHVC real-time NOx traces for the Freightliner Class 8 

truck. 

Figure 17. Portions of the CSHVC real-time NOx traces for the motor coach. 

32
Figure 18. Portions of the CILCC real-time NOx traces for the International Class 8 

truck. 

33
Summary and Recommendations 

The objective of this study was to determine if testing entire vehicles on a heavy-duty 

chassis dynamometer provides a better, more realistic measurement of the impact of B20 

on regulated pollutant emissions. This report also documents completion of the National 

Renewable Energy Laboratory’s Fiscal Year 2006 Annual Operating Plan Milestone 

10.4. This milestone supports the U.S. Department of Energy, Fuels Technologies 

Program Multiyear Program Plan Goal of identifying fuels that can displace 5% of 

petroleum diesel by 2010. 

An EPA review of engine testing studies on biodiesel concluded that on average, for soy 

biodiesel, NOx emissions increase by 2% [16]. Careful examination of the test data on 

which this conclusion is based shows that nearly half of the observations (44%) were for 

DDC engines in the 1991 to 1997 model year range, and a large majority of these are for 

the Series 60 model. We believe that EPA’s conclusion of a NOx increase is influenced 

by the unrepresentative composition of the engine dataset. A hallmark of the B20 

emission test results is that NOx is highly variable, with percentage change ranging from 

roughly -7% to +7%. Because data for the DDC Series 60 engine, which typically 

exhibits a small NOx increase for B20, makes up such a large fraction of the data 

reviewed, EPA draws a conclusion that is at odds with the results of more recent studies. 

Here we review more recently published studies (Table 3) and find an average change in 

NOx for all recent B20 studies of -0.6%±2.0% (95% confidence interval). Restricting the 

average to recent studies of B20 with soy biodiesel yields an average NOx impact of 

0.1%±2.7%. The EPA review also includes summary of a smaller vehicle testing dataset 

that shows no significant impact of biodiesel on NOx. We reviewed several more 

recently published vehicle (chassis) testing studies (Tables 4 and 5) and found an average 

change in NOx of 1.2%±2.9% (95% confidence interval). 

In the work reported here, eight heavy-duty diesel vehicles were tested, including three 

transit buses, two school buses, two Class 8 trucks, and one motor coach. Four of these 

vehicles met the 1998 heavy-duty emissions requirement of 4 g/bhp-h NOx and four met 

the 2004 limit of 2.5 g/bhp-h NOx+HC. Driving cycles that simulate both urban and 

freeway driving were employed. Each vehicle was tested on a petroleum-derived diesel 

fuel and on a 20 volume percent blend of that fuel with soy derived biodiesel. On 

average B20 caused PM and CO emissions to be reduced by 16% to 17% and HC 

emissions to be reduced by 12% relative to petroleum diesel. Emissions of these three 

regulated pollutants nearly always went down, the one exception being a vehicle 

equipped with a DPF that showed very low emissions of PM, CO, and HC. Furthermore, 

there was no significant change in these emissions for blending of B20. The NOx 

emissions impact of B20 varied widely with engine/vehicle technology and test cycle 

ranging from -5.8% to +6.2%. On average, NOx emissions did not change (statistically 

insignificant 0.6% average change). If the results of this study are combined with the soy 

B20 results from Tables 4 and 5 (recently published studies), the average change in NOx 

is 0.9%±1.5% (95% confidence interval). 

34
Based on the studies reviewed and the new data reported here, there does not appear to be 

a discrepancy between engine and chassis testing studies for the effect of B20 on NOx 

emissions. The apparent disagreement that exists between engine testing results and 

chassis testing results in EPA’s 2002 review occurred because neither of these datasets is 

representative of the on-road fleet. Newer studies are not more representative, but if all 

of the available data are viewed together we conclude that B20 has no significant impact 

on NOx. 

A preliminary examination of real-time NOx emissions data did not reveal any consistent 

reason for the wide range in NOx emission results for different vehicles. It is 

recommended that the real-time data be more fully analyzed in a study that considers the 

effect of vehicle speed and acceleration, as well as wheel horsepower and rate of change 

of horsepower. Additionally, modeling of the vehicle transmission to estimate actual 

engine torque output is recommended. Given the significant amount of additional data 

now available, an updating and revision of the EPA review is also recommended. And it 

is further recommended that strict quality criteria be applied, and studies with inadequate 

documentation, methodology, or controls be rejected. 

35
Appendix: Detailed Chassis Test Data 

Table 25. RTD Transit Bus #1 – CSHVC – LSD A 

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

2/1/2005 Base 332 John 2002 19.90 0.906 4.18 0.2380 6.65 686 4.68 2/1/2005 Base 333 Stuart 2007 20.56 1.033 3.74 0.2185 6.63 683 4.70 2/2/2005 Base 337 John 2058 19.69 0.816 3.48 0.3055 6.65 714 4.50 2/2/2005 Base 338 Stuart 2023 19.81 0.854 3.08 0.2616 6.64 686 4.68 2/2/2005 Base 339 John 2031 19.33 0.789 3.78 0.3263 6.68 688 4.67 2/2/2005 Base 340 Stuart 1971 19.54 0.829 3.32 0.2940 6.67 672 4.77 

Average 2015 19.80 0.871 3.60 0.2740 6.65 688 4.67 

Standard Deviation 29 0.42 0.089 0.39 0.0416 0.02 14 0.09 

Coefficient of Variation 1.5% 2.1% 10.2% 10.8% 15.2% 0.3% 2.0% 1.9% 

Table 26. RTD Transit Bus #1 – CSHVC – B20 (LSD A and BlueSun Biodiesel) 

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

2/1/2005 B20 326 Stuart 2,003 18.78 0.604 2.48 0.2421 6.62 719 4.43 2/1/2005 B20 328 John 1,979 18.54 0.598 2.94 0.2200 6.66 712 4.54 2/1/2005 B20 329 John 2,013 18.83 0.581 2.69 0.2365 6.67 719 4.50 2/2/2005 B20 345 John 2,012 18.36 0.485 2.97 0.2603 6.71 712 4.55 2/2/2005 B20 346 Stuart 1,985 18.83 0.729 2.35 0.1961 6.64 696 4.65 2/2/2005 B20 347 Stuart 1,952 18.57 0.754 2.36 0.2037 6.68 691 4.69 

Average 1,991 18.65 0.625 2.63 0.2264 6.66 708 4.56 

Standard Deviation 24 0.19 0.100 0.28 0.0244 0.03 12 0.09 

Coefficient of Variation 1.2% 1.0% 16.0% 10.6% 10.8% 0.5% 1.7% 2.1% 

36 
Table 27. RTD Transit Bus #2 – CSHVC – LSD A 

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

2/4/2005 Base 364 Stuart 1,955 19.81 0.806 2.84 0.2178 6.65 689 4.67 2/4/2005 Base 365 Stuart 1,941 19.86 0.818 2.77 0.2001 6.68 689 4.67 2/4/2005 Base 366 John 1,975 19.24 0.724 3.64 0.2901 6.66 704 4.57 2/4/2005 Base 367 John 1,977 19.08 0.938 3.60 0.2804 6.66 699 4.60 2/7/2005 Base 371 Stuart 2,035 19.97 0.731 3.37 0.6017 6.64 760 4.23 2/7/2005 Base 372 John 1,968 18.68 0.747 4.35 0.3358 6.69 712 4.52 

Average 1,975 19.44 0.794 3.43 0.3210 6.66 709 4.54 

Standard Deviation 32 0.52 0.081 0.58 0.1462 0.02 26 0.16 

Coefficient of Variation 1.6% 2.7% 10.2% 17.0% 45.6% 0.3% 3.7% 3.6% 

Table 28. RTD Transit Bus #2 – CSHVC – B20 (LSD A and BlueSun Biodiesel) 

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

2/4/2005 B20 358 John 2,070 19.01 0.542 3.18 0.2583 6.66 765 4.24 2/4/2005 B20 359 Stuart 1,960 18.75 0.566 2.37 0.1933 6.65 750 4.33 2/4/2005 B20 360 John 1,990 18.47 0.546 2.93 0.2439 6.71 743 4.37 2/4/2005 B20 362 Stuart 1,967 19.17 0.564 2.43 0.1581 6.72 730 4.44 2/7/2005 B20 377 John 2,044 18.33 0.533 3.61 0.3261 6.70 729 4.45 2/7/2005 B20 378 Stuart 1,965 18.38 0.597 2.38 0.1868 6.68 707 4.59 2/7/2005 B20 379 John 1,954 18.20 0.616 2.53 0.1821 6.68 703 4.62 2/7/2005 B20 380 Stuart 1,978 19.08 0.608 2.42 0.1714 6.68 713 4.55 

Average 1,991 18.67 0.571 2.73 0.2150 6.68 730 4.45 

Standard Deviation 43 0.38 0.032 0.46 0.0568 0.02 22 0.13 

Coefficient of Variation 2.1% 2.0% 5.6% 16.9% 26.4% 0.4% 3.0% 3.0% 

37
Table 29. RTD Transit Bus #3 – CSHVC – LSD A 

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

9/8/2005 Base 725 Stuart 2,052 19.59 0.781 3.23 0.3421 6.69 693 4.61 9/8/2005 Base 726 Stuart 2,066 20.02 0.845 3.21 0.3457 6.68 697 4.59 9/8/2005 Base 727 Stuart 2,051 20.06 0.835 3.05 0.3144 6.68 689 4.64 

9/12/2005 Base 752 Stuart 2,061 19.63 0.831 3.09 0.2954 6.68 700 4.57 9/12/2005 Base 753 Stuart 2,041 19.78 0.815 2.80 0.2579 6.67 699 4.57 9/12/2005 Base 754 Stuart 2,045 19.61 0.835 2.87 0.2919 6.67 696 4.59 

Average 2,053 19.78 0.824 3.04 0.3079 6.68 695 4.60 

Standard Deviation 9 0.21 0.023 0.18 0.0333 0.01 4 0.03 

Coefficient of Variation 0.5% 1.1% 2.8% 5.8% 10.8% 0.1% 0.6% 0.6% 

Table 30. RTD Transit Bus #3 – CSHVC – B20 (LSD A and BlueSun Biodiesel) 

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

9/8/2005 B20 729 Stuart 2,040 18.92 0.578 2.66 0.2511 6.69 708 4.55 9/8/2005 B20 730 Stuart 2,032 18.96 0.654 2.63 0.2615 6.67 708 4.55 9/8/2005 B20 731 Stuart 2,029 18.79 0.666 2.74 0.2612 6.67 706 4.56 

9/12/2005 B20 749 Stuart 2,090 19.32 0.523 2.27 0.2379 6.67 723 4.47 9/12/2005 B20 750 Stuart 2,095 19.17 0.587 2.23 0.2235 6.69 724 4.46 9/12/2005 B20 751 Stuart 2,101 19.09 0.546 2.33 0.2332 6.69 723 4.47 

Average 2,064 19.04 0.592 2.48 0.2447 6.68 715 4.51 

Standard Deviation 34 0.19 0.057 0.22 0.0157 0.01 9 0.05 

Coefficient of Variation 1.7% 1.0% 9.7% 9.0% 6.4% 0.2% 1.2% 1.1% 

38
Table 31. RTD Transit Bus #3 – CSHVC – LSD B 

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

9/9/2005 Base 735 Stuart 2,055 20.40 0.817 2.69 0.2522 6.68 693 4.61 9/9/2005 Base 736 Stuart 2,042 20.27 0.834 2.80 0.2437 6.67 683 4.68 9/9/2005 Base 737 Stuart 2,068 20.74 0.818 2.87 0.2631 6.68 696 4.59 

9/12/2005 Base 746 Stuart 2,086 20.20 0.860 3.36 0.3192 6.68 708 4.52 9/12/2005 Base 747 Stuart 2,032 19.78 0.803 3.45 0.3061 6.67 697 4.59 9/12/2005 Base 748 Stuart 2,057 20.05 0.810 3.25 0.2989 6.68 699 4.57 

Average 2,057 20.24 0.824 3.07 0.2805 6.68 696 4.59 

Standard Deviation 19 0.32 0.021 0.32 0.0314 0.01 8 0.05 

Coefficient of Variation 0.9% 1.6% 2.5% 10.4% 11.2% 0.1% 1.2% 1.2% 

Table 32. RTD Transit Bus #3 – CSHVC – B20 (LSD B and Agland Biodiesel) 

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

9/9/2005 B20 739 Stuart 2,032 19.94 0.685 2.69 0.2316 6.67 706 4.56 9/9/2005 B20 740 Stuart 2,029 20.07 0.719 2.50 0.2159 6.66 706 4.56 9/9/2005 B20 741 Stuart 2,040 19.96 0.695 2.46 nm 6.70 721 4.46 

9/12/2005 B20 743 Stuart 2,087 19.48 0.545 2.91 0.2435 6.67 718 4.49 9/12/2005 B20 744 Stuart 2,055 19.54 0.667 2.66 0.2250 6.66 717 4.49 9/12/2005 B20 745 Stuart 2,041 19.19 0.644 2.99 0.2458 6.68 724 4.45 

Average 2,047 19.70 0.659 2.70 0.2324 6.67 716 4.50 

Standard Deviation 21 0.35 0.062 0.22 0.0126 0.02 8 0.05 

Coefficient of Variation 1.0% 1.8% 9.3% 8.0% 5.4% 0.2% 1.1% 1.1% 

39
Table 33. International Class 8 Truck – CILCCmod – LSD C 

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

04/19/06 Base 1,105 Greg 2,347 11.18 1.165 4.79 0.2844 12.70 749 4.28 04/19/06 Base 1,106 Greg 2,357 10.98 1.222 5.05 0.2975 12.67 744 4.31 04/19/06 Base 1,107 Greg 2,328 10.96 1.189 5.09 0.2851 12.72 728 4.37 

Average 2,344 11.04 1.192 4.98 0.2890 12.70 740 4.32 

Standard Deviation 15 0.12 0.029 0.16 0.0074 0.03 11 0.05 

Coefficient of Variation 0.6% 1.1% 2.4% 3.3% 2.6% 0.2% 1.5% 1.0% 

Table 34. International Class 8 Truck – CILCCmod – B20 (LSD C and Agland Biodiese

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

04/19/06 B20 1,102 Greg 2,321 11.02 1.01 4.28 0.2141 12.72 760 4.23 04/19/06 B20 1,103 Greg 2,326 11.20 1.01 4.24 0.2052 12.73 756 4.25 04/19/06 B20 1,104 Greg 2,311 10.87 0.96 4.12 0.2116 12.75 769 4.18 

Average 2,320 11.03 0.992 4.22 0.2103 12.73 762 4.22 

Standard Deviation 8 0.16 0.030 0.08 0.0046 0.02 6 0.04 

Coefficient of Variation 0.3% 1.5% 3.0% 2.0% 2.2% 0.1% 0.8% 0.9% 

40
Table 35. International Class 8 Truck – Freeway Cycle – LSD C 

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

04/18/06 Base 1,093 Greg 1,899 6.73 0.51 2.13 0.2259 15.40 588 5.42 04/18/06 Base 1,094 Greg 1,897 6.74 0.52 2.10 0.2077 15.42 583 5.46 04/18/06 Base 1,095 Greg 1,904 6.76 0.51 2.16 0.2152 15.40 586 5.43 

Average 1,900 6.75 0.515 2.13 0.2163 15.41 586 5.44 

Standard Deviation 4 0.02 0.003 0.03 0.0092 0.01 2 0.02 

Coefficient of Variation 0.2% 0.2% 0.5% 1.5% 4.2% 0.1% 0.4% 0.4% 

Table 36. International Class 8 Truck – Freeway Cycle – B20 (LSD C and Agland Biodie

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

04/18/06 B20 1,097 Greg 1,884 7.00 0.45 1.80 0.1410 15.40 594 5.41 04/18/06 B20 1,099 Greg 1,867 6.85 0.44 1.85 0.1404 15.42 591 5.44 04/18/06 B20 1,100 Greg 1,883 6.86 0.46 1.80 0.1422 15.43 596 5.39 

Average 1,878 6.90 0.452 1.82 0.1412 15.42 594 5.41 

Standard Deviation 10 0.09 0.008 0.03 0.0009 0.02 3 0.02 

Coefficient of Variation 0.5% 1.2% 1.8% 1.6% 0.6% 0.1% 0.4% 0.4% 

41
Table 37. Freightliner Class 8 Truck – CSHVC – 2007 Cert Diesel 

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

06/28/06 Base 1,157 Greg 2,886 28.89 0.541 nm 2.1352 6.64 911 3.50 06/28/06 Base 1,158 Greg 2,927 29.64 0.517 nm nm 6.64 923 3.45 

06/28/06 Base 1,159 Greg 2,909 29.26 0.585 nm nm 6.68 915 3.48 07/05/06 Base 1,167 Greg 2,910 29.79 0.543 28.83 1.8259 6.66 931 3.42 07/05/06 Base 1,168 Greg 2,796 30.16 0.519 26.18 1.6310 6.70 890 3.57 07/05/06 Base 1,169 Greg 2,848 30.15 0.509 27.21 1.7292 6.68 908 3.50 

Average 2,879 29.65 0.536 27.41 1.8303 6.67 913 3.49 

Standard Deviation 49 0.50 0.028 1.34 0.2183 0.02 14 0.05 

Coefficient of Variation 1.7% 1.7% 5.2% 4.9% 11.9% 0.4% 1.5% 1.5% 

Table 38. Freightliner Class 8 Truck – CSHVC – B20 (2007 Cert Diesel and Agland Biodi

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

06/28/06 B20 1,160 Greg 2,944 30.44 0.432 nm nm 6.67 947 3.40 06/28/06 B20 1,161 Greg 2,860 29.94 0.438 nm 1.5571 6.67 924 3.48 06/28/06 B20 1,162 Greg 2,910 30.64 0.442 nm 1.4961 6.65 947 3.39 07/05/06 B20 1,164 Greg 2,951 30.73 0.493 23.29 1.4679 6.43 946 3.40 07/05/06 B20 1,165 Greg 2,827 30.02 0.447 23.61 1.3207 6.67 911 3.52 07/05/06 B20 1,166 Greg 2,880 29.78 0.474 26.55 1.5385 6.65 935 3.43 

Average 2,895 30.26 0.454 24.49 1.4761 6.62 935 3.44 

Standard Deviation 49 0.40 0.024 1.80 0.0936 0.10 15 0.05 

Coefficient of Variation 1.7% 1.3% 5.3% 7.3% 6.3% 1.4% 1.6% 1.6% 

42
Table 39. Freightliner Class 8 Truck – Freeway Cycle – 2007 Cert Diesel 

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

07/06/06 Base 1,171 Greg 1,699 22.25 0.216 8.09 0.4767 15.50 538 5.91 07/06/06 Base 1,172 Greg 1,745 22.54 0.209 8.17 0.6062 15.50 545 5.84 

07/06/06 Base 1,173 Greg 1,741 22.08 0.172 7.93 0.5470 15.51 542 5.87 07/07/06 Base 1,183 Greg 1,708 22.11 0.211 8.78 0.4604 15.49 537 5.92 07/07/06 Base 1,184 Greg 1,689 21.65 0.190 8.19 0.4138 15.51 535 5.95 07/07/06 Base 1,185 Greg 1,688 22.98 0.201 7.68 0.3913 15.50 538 5.92 

Average 1,712 22.27 0.200 8.14 0.4826 15.50 539 5.90 

Standard Deviation 25 0.45 0.016 0.37 0.0813 0.01 4 0.04 

Coefficient of Variation 1.5% 2.0% 8.2% 4.5% 16.8% 0.0% 0.7% 0.6% 

Table 40. Freightliner Class 8 Truck – Freeway Cycle – B20 (2007 Cert Diesel and Agland Bi

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

07/06/06 B20 1,176 Greg 1,732 23.31 0.134 7.80 0.4001 15.50 559 5.75 07/06/06 B20 1,177 Greg 1,720 23.04 0.168 7.64 0.3702 15.50 554 5.79 07/06/06 B20 1,178 Greg 1,717 23.04 0.166 7.63 0.3646 15.50 552 5.81 07/07/06 B20 1,180 Greg 1,721 23.69 0.182 7.41 0.3368 15.50 552 5.82 07/07/06 B20 1,181 Greg 1,713 23.10 0.173 7.55 0.3259 15.50 551 5.83 07/07/06 B20 1,182 Greg 1,695 22.27 0.184 7.43 0.3401 15.51 551 5.83 

Average 1,716 23.08 0.168 7.58 0.3563 15.50 553 5.81 

Standard Deviation 12 0.47 0.018 0.15 0.0274 0.00 3 0.03 

Coefficient of Variation 0.7% 2.0% 10.8% 1.9% 7.7% 0.0% 0.5% 0.5% 

43
Table 41. Motor Coach – CSHVC – 2007 Cert Diesel 

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

5/25/2006 Base 1,115 Greg 1,510 7.77 0.21 4.51 0.2686 6.67 487 6.60 5/25/2006 Base 1,116 Greg 1,492 7.87 0.23 4.41 0.2432 6.68 484 6.64 

5/25/2006 Base 1,117 Greg 1,513 7.49 0.27 4.16 0.2926 6.68 489 6.58 5/26/2006 Base 1,127 Greg 1,504 7.78 0.22 4.06 0.2397 6.67 486 6.61 5/26/2006 Base 1,128 Greg 1,489 7.87 0.21 3.63 0.2345 6.68 481 6.68 5/26/2006 Base 1,129 Greg 1,501 7.70 0.23 3.56 0.2439 6.68 482 6.66 

Average 1,501 7.75 0.23 4.05 0.2538 6.68 485 6.63 

Standard Deviation 10 0.14 0.02 0.39 0.0224 0.01 3 0.04 

Coefficient of Variation 0.6% 1.8% 10.3% 9.7% 8.8% 0.1% 0.6% 0.6% 

Table 42. Motor Coach – CSHVC – B20 (2007 Cert Diesel and Agland Biodiesel) 

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

5/25/2006 B20 1,119 Greg 1,484 8.01 0.18 3.40 0.1797 6.68 491 6.59 5/25/2006 B20 1,120 Greg 1,488 8.23 0.19 3.30 0.1868 6.68 493 6.56 5/25/2006 B20 1,121 Greg 1,496 7.86 0.20 3.18 nm 6.67 497 6.52 5/26/2006 B20 1,123 Greg 1,495 7.80 0.20 2.88 0.1740 6.68 495 6.55 5/26/2006 B20 1,124 Greg 1,503 8.04 0.21 3.10 0.1810 6.67 493 6.57 5/26/2006 B20 1,125 Greg 1,507 7.82 0.20 3.03 0.1910 6.67 500 6.48 

Average 1,496 7.96 0.19 3.15 0.1825 6.67 495 6.54 

Standard Deviation 9 0.16 0.01 0.19 0.0066 0.01 3 0.04 

Coefficient of Variation 0.6% 2.1% 4.5% 6.0% 3.6% 0.1% 0.7% 0.6% 

44
Table 43. Motor Coach – UDDS – 2007 Cert Diesel 

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

5/31/2006 Base 1,142 Stuart 1,378 7.18 0.14 3.73 0.2355 5.53 443 7.23 5/31/2006 Base 1,143 Stuart 1,366 6.98 0.11 4.04 0.2478 5.52 442 7.26 

5/31/2006 Base 1,144 Stuart 1,368 7.07 0.13 3.51 0.2231 5.54 441 7.26 

6/2/2006 Base 1,146 Stuart 1,462 6.80 0.16 3.70 0.2480 5.53 470 6.83 6/2/2006 Base 1,147 Stuart 1,465 6.97 0.15 3.46 0.2448 5.53 470 6.84 6/2/2006 Base 1,148 Stuart 1,462 6.94 0.14 3.49 0.2330 5.53 469 6.85 

Average 1,417 6.99 0.14 3.66 0.2387 5.53 456 7.05 

Standard Deviation 51 0.13 0.02 0.22 0.0099 0.01 15 0.23 

Coefficient of Variation 3.6% 1.9% 12.4% 6.0% 4.2% 0.1% 3.3% 3.2% 

Table 44. Motor Coach – UDDS – B20 (2007 Cert Diesel and Agland Biodiesel) 

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

5/31/2006 B20 1,136 Stuart 1,390 7.58 0.09 2.82 0.1530 5.52 455 7.12 5/31/2006 B20 1,137 Stuart 1,401 7.44 0.14 2.93 0.1552 5.52 461 7.02 5/31/2006 B20 1,140 Stuart 1,445 7.12 0.13 2.85 0.1521 5.53 476 6.80 

6/2/2006 B20 1,149 Stuart 1,418 7.13 0.15 2.99 0.1723 5.53 466 6.95 6/2/2006 B20 1,150 Stuart 1,406 6.95 0.14 3.04 0.1814 5.53 460 7.04 6/2/2006 B20 1,151 Stuart 1,399 7.14 0.15 3.09 0.1892 5.53 457 7.09 

Average 1410 7.22 0.13 2.95 0.1672 5.53 462 7.00 

Standard Deviation 20 0.24 0.02 0.11 0.0160 0.01 8 0.12 

Coefficient of Variation 1.4% 3.3% 17.8% 3.6% 9.6% 0.1% 1.7% 1.7% 

45
Table 45. Green Diesel School Bus – RUCSBC– 2007 Cert Diesel 

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

03/22/06 Base 993 Greg 2,134 8.78 0.03 0.04 0.0016 7.61 651 4.95 03/22/06 Base 994 Greg 2,149 nm 0.04 0.11 0.0019 7.61 654 4.92 

03/22/06 Base 995 Greg 2,098 nm 0.02 0.06 0.0016 7.61 642 5.02 03/22/06 Base 996 Greg 2,091 nm 0.02 0.07 0.0013 7.62 644 5.00 03/23/06 Base 1,007 Greg 2,074 8.90 0.02 0.18 nm 7.63 632 5.10 

03/23/06 Base 1,008 Greg 2,126 8.97 0.03 0.12 nm 7.62 651 4.94 03/23/06 Base 1,009 Greg 2,121 8.92 0.02 0.18 0.0015 7.62 652 4.93 03/23/06 Base 1,010 Greg 2,106 9.12 0.03 0.09 0.0015 7.64 651 4.94 03/24/06 Base 1,017 Greg 2,120 8.84 0.02 0.09 0.0013 7.61 648 4.97 03/24/06 Base 1,018 Greg 2,134 8.98 0.02 0.10 0.0008 7.62 654 4.92 

Average 2,115 8.93 0.02 0.10 0.0014 7.62 648 4.97 

Standard Deviation 23 0.11 0.01 0.05 0.0003 0.01 7 0.06 

Coefficient of Variation 1.1% 1.2% 31.9% 45.5% 22.1% 0.1% 1.1% 1.1% 

46
Table 46. Green Diesel School Bus – RUCSBC– B20 (2007 Cert Diesel and Agland Biodi

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

03/22/06 B20 998 Greg 2,098 8.83 0.05 0.09 0.0016 7.61 652 4.98 03/22/06 B20 999 Greg 2,101 nm 0.02 0.05 0.0019 7.62 647 5.02 03/22/06 B20 1,000 Greg 2,131 nm 0.01 0.03 0.0016 7.62 667 4.86 03/22/06 B20 1,001 Greg 2,110 9.14 0.02 0.03 nm 7.61 656 4.94 03/23/06 B20 1,003 Greg 2,127 9.34 0.02 0.04 0.0019 7.61 660 4.92 03/23/06 B20 1,004 Greg 2,124 9.21 0.02 0.06 0.0020 7.60 667 4.87 03/23/06 B20 1,005 Greg 2,120 9.18 0.02 0.12 0.0011 7.62 661 4.91 

Average 2,116 9.14 0.02 0.06 0.0017 7.61 659 4.93 

Standard Deviation 13 0.19 0.01 0.03 0.0003 0.01 7 0.06 

Coefficient of Variation 0.6% 2.1% 55.0% 55.0% 19.6% 0.1% 1.1% 1.2% 

47
Table 47. Green Diesel School Bus – CSHVC – 2007 Cert Diesel 

Date Fuel Run Driver CO2 

(g/mile) 

NOx 

(g/mile) 

THC 

(g/mile) 

CO 

(g/mile) 

PM 

(g/mile) 

Distance 

(miles) 

Fuel Cons 

(g/mile) 

Fuel Ec

(mpg

03/14/06 Base 950 Greg 1,734 7.99 0.03 0.35 0.0014 6.68 567 5.66 03/14/06 Base 951 Greg 1,700 7.79 0.04 0.09 0.0011 6.70 554 5.80 

03/14/06 Base 952 Greg 1,719 7.38 0.05 0.14 0.0011 6.70 559 5.75 03/15/06 Base 954 Greg 1,716 7.67 -0.05 0.25 0.0012 6.69 555 5.80 03/15/06 Base 955 Greg 1,706 7.47 0.04 0.12 0.0009 6.70 565 5.70 03/15/06 Base 956 Greg 1,693 7.41 0.02 0.07 0.0016 6.70 556 5.78 03/16/06 Base 966 Greg 1,684 8.00 0.02 0.26 0.0009 6.71 536 6.01 03/16/06 Base 967 Greg 1,676 7.67 0.03 0.06 0.0008 6.71 539 5.97 03/16/06 Base 968 Greg 1,670 7.56 0.03 0.08 0.0006 6.71 545 5.91 03/21/06 Base 988 Greg 1,692 7.99 0.04 0.42 0.0007 6.69 544 5.91 03/21/06 Base 989 Greg 1,675 nm -0.01 -0.02 0.0010 6.69 538 5.98 03/21/06 Base 990 Greg 1,684 nm 0.03 0.02 0.0003 6.69 544 5.91 03/21/06 Base 991 Greg 1,662 7.83 0.02 0.07 0.0006 6.69 540 5.96 

Average 1,693 7.70 0.02 0.15 0.0009 6.70 549 5.86 

Standard Deviation 21 0.23 0.03 0.13 0.0004 0.01 11 0.11 

Coefficient of Variation 1.2% 3.0% 118.7% 90.1% 37.3% 0.1% 1.9% 1.9% 

48
Table 48. Green Diesel School Bus – CSHVC – B20 (2007 Cert Diesel and Agland Biodie

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

03/15/06 B20 958 Greg 1,716 7.75 0.02 0.02 0.0011 6.70 568 5.71 03/15/06 B20 959 Greg 1,707 7.54 0.04 0.18 0.0014 6.70 560 5.78 03/15/06 B20 960 Greg 1,721 7.77 0.02 0.13 0.0010 6.69 554 5.85 03/16/06 B20 962 Greg 1,704 7.70 0.04 0.19 0.0012 6.70 574 5.65 03/16/06 B20 963 Greg 1,689 7.60 0.03 0.12 0.0014 6.70 566 5.72 03/16/06 B20 964 Greg 1,685 7.49 0.04 0.09 0.0013 6.70 566 5.73 

Average 1,704 7.64 0.03 0.12 0.0012 6.70 565 5.74 

Standard Deviation 14 0.12 0.01 0.06 0.0002 0.00 7 0.07 

Coefficient of Variation 0.8% 1.5% 31.5% 52.2% 14.5% 0.1% 1.2% 1.2% 

49
Table 49. Conventional School Bus – RUCSBC – 2007 Cert Diesel 

Date Fuel Run Driver CO2 

(g/mile) 

NOx 

(g/mile) 

THC 

(g/mile) 

CO 

(g/mile) 

PM 

(g/mile) 

Distance 

(miles) 

Fuel Cons 

(g/mile) 

Fuel Ec

(mpg

08/09/06 Base 1,228 John 1,984 10.10 0.265 8.03 0.6554 7.61 643 4.93 08/09/06 Base 1,229 John 1,935 9.94 0.266 7.57 0.6193 7.60 622 5.09 

08/09/06 Base 1,230 John 1,937 9.79 0.284 8.31 0.7038 7.65 627 5.05 08/09/06 Base 1,231 John 1,944 9.94 0.278 8.24 0.6731 7.63 624 5.07 08/11/06 Base 1,242 John 1,983 9.63 0.402 8.80 0.7604 7.63 636 4.98 08/11/06 Base 1,243 John 1,990 9.66 0.727 10.10 0.7370 7.63 645 4.91 08/11/06 Base 1,244 John 1,987 9.75 0.483 9.27 0.7303 7.63 640 4.95 08/11/06 Base 1,245 John 1,940 9.81 0.526 9.75 0.6841 7.63 625 5.07 08/17/06 Base 1,268 John 1,998 9.81 0.259 7.97 nm 7.65 640 4.96 08/17/06 Base 1,269 John 1,989 9.38 0.357 10.36 nm 7.63 636 4.98 08/17/06 Base 1,270 John 1,968 nm 0.320 9.50 nm 7.62 626 5.06 08/17/06 Base 1,271 John 1,968 nm 0.298 9.72 nm 7.63 630 5.03 08/17/06 Base 1,272 John 1,973 nm 0.383 8.75 nm 7.62 634 5.00 

Average 1,969 9.78 0.373 8.95 0.6954 7.63 633 5.01 

Standard Deviation 22 0.20 0.137 0.90 0.0467 0.01 8 0.06 

Coefficient of Variation 1.1% 2.0% 36.6% 10.0% 6.7% 0.2% 1.2% 1.2% 

50
Table 50. Conventional School Bus – RUCSBC – B20 (2007 Cert Diesel and Agland Biod

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

08/09/06 B20 1,224 John 1,999 10.78 0.179 5.09 0.4875 7.67 657 4.90 08/09/06 B20 1,225 John 1,968 10.57 0.185 5.68 0.4818 7.60 646 4.98 08/09/06 B20 1,226 John 1,965 10.28 0.197 5.80 0.4818 7.64 641 5.02 08/09/06 B20 1,227 John 1,991 10.41 0.206 6.63 0.5317 7.63 654 4.92 08/11/06 B20 1,247 John 1,928 10.22 0.416 7.85 0.5171 7.62 632 5.10 08/11/06 B20 1,248 John 1,949 10.35 0.459 8.40 0.5820 7.62 643 5.00 08/11/06 B20 1,249 John 1,954 10.12 0.455 9.05 0.6172 7.62 642 5.02 

Average 1965 10.39 0.300 6.93 0.5284 7.63 645 4.99 

Standard Deviation 24 0.22 0.135 1.52 0.0531 0.02 8 0.07 

Coefficient of Variation 1.2% 2.2% 45.2% 21.9% 10.0% 0.3% 1.3% 1.3% 

51
Table 51. Conventional School Bus – CSHVC – 2007 Cert Diesel 

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

08/01/06 Base 1,193 Greg 1,650 10.24 0.338 4.87 0.1954 6.69 533 5.95 08/01/06 Base 1,194 Greg 1,652 10.22 0.336 4.68 0.2016 6.67 544 5.83 

08/01/06 Base 1,195 Greg 1,644 9.90 0.402 4.89 0.1882 6.69 538 5.90 08/02/06 Base 1,206 Greg 1,624 9.89 0.603 5.87 0.2114 6.69 543 5.83 08/02/06 Base 1,207 Greg 1,624 9.76 0.480 6.47 0.2517 6.70 537 5.89 08/03/06 Base 1,209 Greg 1,634 10.04 0.432 5.24 0.1972 6.70 535 5.93 08/03/06 Base 1,210 Greg 1,607 9.88 0.463 5.94 0.2371 6.69 528 6.01 08/03/06 Base 1,211 Greg 1,611 9.85 0.475 6.17 0.2439 6.70 517 6.13 08/03/06 Base 1,212 Greg 1,618 9.67 0.491 6.31 0.2429 6.70 531 5.97 08/10/06 Base 1,233 Greg 1,637 9.94 0.433 4.61 0.1436 6.69 535 5.93 08/10/06 Base 1,234 Greg 1,622 9.85 0.264 4.41 0.1460 6.68 528 6.00 08/10/06 Base 1,235 Greg 1,615 9.60 0.440 4.52 0.1417 6.69 535 5.92 08/10/06 Base 1,236 Greg 1,614 9.58 0.487 5.14 0.1624 6.69 539 5.88 08/10/06 Base 1,237 Greg 1,606 9.73 0.431 4.38 0.1370 6.70 537 5.90 08/10/06 Base 1,239 Greg 1,610 9.66 0.507 4.76 nm 6.70 537 5.90 

Average 1,620 9.85 0.439 5.22 0.1929 6.69 534 5.93 

Standard Deviation 11 0.20 0.081 0.74 0.0414 0.01 7 0.08 

Coefficient of Variation 0.7% 2.0% 18.6% 14.1% 21.5% 0.1% 1.2% 1.3% 

52
Table 52. Conventional School Bus – CSHVC – B20 (2007 Cert Diesel and Agland Biodie

Date Fuel Run Driver CO2 NOx THC CO PM Distance Fuel Cons Fuel Ec

(g/mile) (g/mile) (g/mile) (g/mile) (g/mile) (miles) (g/mile) (mpg

08/01/06 B20 1,198 Greg 1,624 9.83 0.419 6.22 0.2211 6.69 554 5.81 08/01/06 B20 1,199 Greg 1,623 9.65 0.473 7.06 0.2494 6.68 554 5.80 08/01/06 B20 1,200 Greg 1,608 9.51 0.439 6.90 0.2464 6.69 551 5.83 08/02/06 B20 1,202 Greg 1,641 10.21 0.346 4.69 0.1685 6.69 544 5.91 08/02/06 B20 1,203 Greg 1,622 9.73 0.386 5.46 0.1978 6.70 538 5.97 08/02/06 B20 1,204 Greg 1,615 9.63 0.336 5.60 0.2004 6.69 546 5.89 08/02/06 B20 1,205 Greg 1,624 9.60 0.447 6.48 0.2260 6.69 548 5.87 08/03/06 B20 1,214 Greg 1,616 9.95 0.383 6.18 0.2328 6.69 545 5.90 08/03/06 B20 1,215 Greg 1,602 9.67 0.395 5.94 0.2266 6.69 543 5.92 08/03/06 B20 1,216 Greg 1,592 9.82 0.407 6.11 0.2218 6.69 538 5.98 08/04/06 B20 1,218 Greg 1,641 9.96 0.515 5.96 0.2029 6.69 544 5.92 08/04/06 B20 1,219 Greg 1,620 9.61 0.473 5.92 0.1856 6.68 548 5.87 08/04/06 B20 1,220 Greg 1,626 9.71 0.531 5.98 0.1938 6.69 554 5.80 08/04/06 B20 1,221 Greg 1,620 9.77 0.756 6.81 0.2119 6.69 556 5.78 08/04/06 B20 1,222 Greg 1,612 9.53 0.562 6.59 0.2125 6.69 553 5.82 08/15/06 B20 1,251 Greg 1,673 9.55 0.352 4.96 0.1724 6.69 553 5.83 08/15/06 B20 1,252 Greg 1,656 9.55 0.355 4.50 0.1647 6.69 549 5.87 08/15/06 B20 1,254 Greg 1,655 10.43 0.326 3.58 0.1096 6.69 555 5.81 08/15/06 B20 1,255 Greg 1,645 10.24 0.342 3.68 0.1113 6.69 555 5.81 

Average 1,627 9.79 0.434 5.72 0.1977 6.69 549 5.86 

Standard Deviation 20 0.26 0.105 1.01 0.0391 0.00 6 0.06 

Coefficient of Variation 1.2% 2.7% 24.1% 17.7% 19.8% 0.1% 1.0% 1.0% 

53
References 

1. Dtn Energy’s Alternative Fuels Index. Vol. 4, Issue 32, p. 1 (2006). 

2. Tyson, K.; Bozell, J.; Wallace, R. ; Petersen, E. ; Moens, L. “Biomass Oil Analysis: 

Research Needs and Recommendations”, Technical Report, National Renewable 

Energy Laboratory/TP-510-34796, June 2004. 

3. Sheehan, J.; Camobreco, V. ; Duffield, J. ; Graboski, M. ; Shapouri, H. “An Overview 

of Biodiesel and Petroleum Diesel Life Cycles”, National Renewable Energy 

Laboratory/TP-580-24772, May 1998. 

4. McCormick, R.; Alleman, T. “Impact of Biodiesel Fuel on Pollutant Emissions from 

Diesel Engines” in The Biodiesel Handbook, Knothe, G.; Van Gerpen, J.; Krahl, J., 

ed.s, AOCS Press, 2005. 

5. Liotta, F.; Montalvo, D. "The Effect of Oxygenated Fuels on Emissions from a Modern 

Heavy-Duty Diesel Engine", SAE Tech. Pap. No. 932734 (1993). 

6. Rantanen, L.; Mikkonen, S.; Nylund, L.; Kociba, P.; Lappi, M.; Nylund, N. "Effect of 

Fuel on the Regulated, Unregulated and Mutagenic Emissions of DI Diesel Engines", 

SAE Tech. Pap. No. 932686 (1993). 

7. Sharp, C. "Transient Emissions Testing of Biodiesel and Other Additives in a DDC 

Series 60 Engine", Southwest Research Institute, Final Report to the National 

Biodiesel Board, December 1994, available at www.biodiesel.org. 

8. Sharp, C. "Emissions and Lubricity Evaluation of Rapeseed Derived Biodiesel Fuels", 

Southwest Research Institute, Final Report for Montana Department of 

Environmental Quality, November 1996, available at www.biodiesel.org. 

9. Graboski, M.; Ross, J.; McCormick, R. "Transient Emissions from No. 2 Diesel and 

Biodiesel Blends in a DDC Series 60 Engine", SAE Tech. Pap. No. 961166 (1996). 

10. McCormick; R., Ross, J.; Graboski, M. "Effect of Several Oxygenates on Regulated 

Emissions from Heavy-Duty Diesel Engines", Environmental Science & Technology 

31, 1144-1150 1997). 

11. Starr, M. "Influence on Transient Emissions at Various Injection Timings, Using 

Cetane Improvers, Bio-Diesel, and Low Aromatic Fuels", SAE Tech. Pap. No. 

972904(1997). 

12. Clark, N.; Atkinson, C.; Thompson, G.; Nine, R. "Transient Emissions Comparisons 

of Alternative Compression Ignition Fuels", SAE Tech. Pap. No. 1999-01-1117 

(1999). 

13. Sharp, C.; Howell, S.; Jobe, J. "The Effect of Biodiesel Fuels on transient Emissions 

from Modern Diesel Engines, Part I Regulated Emissions and Performance", SAE 

Tech. Pap. No. 2000-01-1967 (2000). 

14. McCormick, R.; Alleman, T.; Graboski, M.; Herring, A.; Tyson, K. “Impact Of 

Biodiesel Source Material and Chemical Structure On Emissions of Criteria 

Pollutants from a Heavy-Duty Engine”, Environmental Science & Technology 35 

1742-1747 (2001). 

15. McCormick, R.; Alvarez, J.; Graboski, M.; Tyson, K.; Vertin, K. “ Fuel Additive and 

Blending Approaches to Reducing NOx Emissions from Biodiesel”, SAE Tech. Pap. 

No. 2002-01-1658 (2002). 

54 
16. United States Environmental Protection Agency. “A Comprehensive Analysis of 

Biodiesel Impacts on Exhaust Emissions”, Draft Technical Report, EPA420-P-02­

001, (2002). 

17. McGill, R.; Storey, J.; Wagner, R.; Irick, D.; Aakko, P.; Westerholm, M.; Nylund, N.; 

Lappi, M. “Emission Performance of Selected Biodiesel Fuels”, SAE Tech. Pap. No. 

2003-01-1866 (2003). 

18. Aakko, P.; Westerholm, M.; Nylund, N.O.; Moissio, M.; Marjamäki, M.; Mäkelä, T.; 

Hillamo, R. “Emission Performance Of Selected Biodiesel Fuels - VTT’s 

Contribution”, Research Report ENE5/33/2000, October 2000. 

19. Frank, B.; Tang, S.; Lanni, T.; Rideout, G.; Beregszaszy, C.; Meyer, N.; Chatterjee, 

S.; Conway, R.; Lowell, D.; Bush, C.; Evans, J. “A Study of the Effects of Fuel Type 

and Emission Control Systems on Regulated Gaseous Emissions from Heavy-Duty 

Diesel Engines”, SAE Tech. Pap. No. 2004-01-1085 (2004). 

20. Souligny, M.; Graham, L.; Rideout, G.; Hosatte, P. “Heavy-Duty Diesel Engine 

Performance and Comparative Emission Measurements for Different Biodiesel 

Blends Used in the Montreal BIOBUS Project”, SAE Tech. Pap. No. 2004-01-1861 

(2004). 

21. Alam, M.; Song, J.; Acharya, R.; Boehman, A.; Miller, K. “Combustion and 

Emissions Performance of Low Sulfur, Ultra Low Sulfur and Biodiesel Blends in a 

DI Diesel Engine”, SAE Tech. Pap. No. 2004-01-3024 (2004). 

22. McCormick, R.; Tennant, C.; Hayes, R.; Black, S.; Ireland, J.; McDaniel, T.; 

Williams, A.; Frailey, M.; Sharp, C. “Regulated Emissions from Biodiesel Tested in 

Heavy-Duty Engines Meeting 2004 Emission Standards”, SAE Tech. Pap. No. 2005­

01-2200 (2005). 

23. Environment Canada. “Emissions Characterization of a Caterpillar 3126E Equipped 

with a Prototype SCRT System with Ultra Low Sulphur Diesel and a Biodiesel 

Blend”, ERMD Report # 2005-32 (2005). 

24. Clark, N.; Lyons, D. “Class 8 Truck Emissions Testing: Effects of Test Cycles and 

Data on Biodiesel Operation”, Transactions of the ASAE 42 (5) 1211-1219 (1999). 

25. Wang, W.; Lyons, D.; Clark, N.; Gautam, M.; Norton, P. “Emissions from Nine 

Heavy Trucks Fueled by Diesel and Biodiesel Blend without Engine Modification”, 

Environmental Science & Technology 34 933-939 (2000). 

26. Peterson, C.; Taberski, J.; Thompson, J.; Chase, C.L. “The Effect of Biodiesel 

Feedstock on Regulated Emissions in Chassis Dynamometer Tests of a Pickup 

Truck”, Transactions of the ASAE 43 (6) 1371-1381 (2000). 

27. Durbin, T.; Cocker, K.; Collins, J.; Norbeck , J.. “Evaluation of the Effects of 

Biodiesel and Biodiesel Blends on Exhaust Emission Rates and Reactivity – 2”, Final 

Report from the Center for Environmental Research and Technology, University of 

California, August 2001. 

28. Environment Canada. “Emission Testing for NRCan Biodiesel Byway Pilot Project”, 

private communication, May 2005. 

29. Holden, B.; Jack, J.; Miller, W.; Durbin, T. “Effect of Biodiesel on Diesel Engine 

Nitrogen Oxide and Other Regulated Emissions”, Technical Report TR-2275-ENV, 

Naval Facilities Engineering Command, Port Hueneme, California. May 2006. 

55
30. United States Environmental Protection Agency. “Final Rule on In-Use Testing 

Program for Heavy-Duty Diesel Engines and Vehicles”, EPA420-F-05-021, June 

2005. 

31. Frey, H.; Kim, K. “Operational Evaluation of Emissions and Fuel Use of B20 versus 

Diesel Fueled Dump Trucks”, Research Project No. 2004-18 FHWA/NC/2005-07, 

September 2005. 

32. Hearne, J.; Toback, A.; Akers, J.; Hesketh, R.; Marchese, A. “Development of a New 

Composite School Bus Test Cycle and the Effect of Fuel Type on Mobile Emissions 

from Three School Buses”, SAE Tech. Pap. No. 2005-01-1616 (2005). 

33. Farzeneh, M.; Zietsman, J.; Perkinson, D. “School Bus Biodiesel (B20) NOx 

Emissions Testing”, Texas Transportation Institute, August 2006. 

34. United States Environmental Protection Agency. Engine Certification Information 

Center: http://www.epa.gov/oms/certdata.htm#largeng, accessed September 19, 2006. 

35. United States Census Bureau. “2002 Economic Census: Vehicle Inventory and Use 

Survey”, EC02TV-US, December 2004. 

36. Zhang, Y.; Van Gerpen, J. “Combustion Analysis of Esters of Soybean Oil in a Diesel 

Engine” SAE Tech. Pap. No. 960765 (1996). 

37. United States Environmental Protection Agency. “The Effect of Cetane Number 

Increase Due to Additives on NOx Emissions from Heavy-Duty Highway Engines”, 

Final Technical Report, EPA420-R-03-002, February 2003. 

38. Cheng, A.; Upatnieks, A.; Mueller, C. "Investigation of the Impact of Biodiesel 

Fuelling On NOx Emissions Using an Optical Direct Injection Diesel Engine", to be 

published: International Journal of Engine Research 7 (4) 297-319 2006. 

39. Ban-Weiss, G.; Chen, J.; Buchholz, B.; Dibble, R. “A Numerical Investigation into 

the Anomalous Slight NOx Increase When Burning Biodiesel: A New (Old) Theory”, 

Prepr. Pap.-Am. Chem. Soc., Div. Fuel Chem. 51(1), 24 (2006) 

40. Miller, J.; Bowman, C. “Mechanism and Modeling of Nitrogen Chemistry in 

Combustion”, Prog. Energy Combust. Sci. 15 287 (1989). 

41. Hess, M.; Haas, M.; Foglia, T.; Marmer, W. “Effect of Antioxidant Addition on NOx 

Emissions from Biodiesel”, Energy & Fuels 19 1749 (2005). 

42. Tat, M.; van Gerpen, J. “Measurement of Biodiesel Speed of Sound and Its Impact on 

Injection Timing”, National Renewable Energy Laboratory, NREL/SR-510-31462, 

February 2003. 

43. Monyem, A.; van Gerpen, J.; Canakci, M. “The Effect of Timing and Oxidation on 

Emissions from Biodiesel-Fueled Engines”, Trans. of the Am. Soc. of Agricultural 

Engineers 44 35 (2001). 

44. Sybist, J.; Boehman, A. “Behavior Of A Diesel Injection System With Biodiesel 

Fuel”, SAE Technical Paper No. 2003-01-1039 (2003). 

45. Clark, N.; Daley, J.; Nine, R.; Atkinson, C.M. “Application of the New CitySuburban Heavy Vehicle Route (CSHVR) to Truck Emissions Characterization”, 

SAE Tech. Pap. No. 1999-01-1467 (1999). 

46. Code of Federal Regulations. Vol. 40, Subpart M. 

47. Zou, Z.; Davis, S.; Beaty, K.; O’Keefe, M.; Hendricks, T.; Rehn, R.; Weissner, S.; 

Sharma, V.K. “A New Composite Drive Cycle for Heavy-Duty Hybrid Electric Class 

4-6 Vehicles”, SAE Tech. Pap. No. 2004-01-1052 (2004). 

56
48. Proc, K.; Barnitt, R.; Hayes, R.; McCormick, R.; Ha, L.; Fang, H. “100,000 Mile 

Evaluation of Transit Buses Operated on Biodiesel Blends (B20)”, SAE Tech. Pap. 

No. 2006-01-3253 (2006). 

49. Yanowitz, J.; Graboski, M.; McCormick, R. “On the Prediction of In-Use Emissions 

of Heavy-Duty Diesel Vehicles from Engine Testing”, Environmental Science & 

Technology 36 270 (2002). 

57
REPORT DOCUMENTATION PAGE Form Approved 

OMB No. 0704-0188 

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Executive Services and Communications Directorate (0704-0188). Respondents 

should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a

currently valid OMB control number. 

PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ORGANIZATION. 

1. REPORT DATE (DD-MM-YYYY) 

October 2006 

2. REPORT TYPE 

Milestone Report 

3. DATES COVERED (From - To) 

10/01/2005 - 09/30/2006 

4. TITLE AND SUBTITLE 

Effects of Biodiesel Blends on Vehicle Emissions: Fiscal Year 2006 

Annual Operating Plan Milestone 10.4 

5a. CONTRACT NUMBER 

DE-AC36-99-GO10337 

5b. GRANT NUMBER 

5c. PROGRAM ELEMENT NUMBER 

6. AUTHOR(S) 

R.L. McCormick, A. Williams, J. Ireland, M. Brimhall, and 

R.R. Hayes 

5d. PROJECT NUMBER 

NREL/MP-540-40554 

5e. TASK NUMBER 

FC06.9400 

5f. WORK UNIT NUMBER 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 

National Renewable Energy Laboratory 

1617 Cole Blvd. 

Golden, CO 80401-3393 

8. PERFORMING ORGANIZATION 

REPORT NUMBER 

NREL/MP-540-40554 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S) 

NREL 

11. SPONSORING/MONITORING 

AGENCY REPORT NUMBER 

12. DISTRIBUTION AVAILABILITY STATEMENT 

National Technical Information Service 

U.S. Department of Commerce 

5285 Port Royal Road 

Springfield, VA 22161 

13. SUPPLEMENTARY NOTES 

NREL Technical Monitor: R. McCormick 

14. ABSTRACT (Maximum 200 Words) 

The objective of this study was to determine if testing entire vehicles, vs. just the engines, on a heavy-duty chassis 

dynamometer provides a better, more realistic measurement of the impact of B20 on regulated pollutant emissions. 

This report also documents completion of the National Renewable Energy Laboratory’s Fiscal Year 2006 Annual 

Operating Plan Milestone 10.4. This milestone supports the U.S. Department of Energy, Fuels Technologies Program 

Multiyear Program Plan Goal of identifying fuels that can displace 5% of petroleum diesel by 2010. Considering all of 

the data available, we conclude that B20 has no net impact on NOx. 

15. SUBJECT TERMS 

biodiesel; B20; testing; pollutant; emissions; chassis; dynamometer; milestone; methanol; ethanol; methyl ester; ethyl 

ester; transesterification; blend; petroleum diesel 

16. SECURITY CLASSIFICATION OF: 17. LIMITATION 

OF ABSTRACT 

UL 

18. NUMBER 

OF PAGES 

19a. NAME OF RESPONSIBLE PERSON 

a. REPORT 

Unclassified 

b. ABSTRACT 

Unclassified 

c. THIS PAGE 

Unclassified 19b. TELEPHONE NUMBER (Include area code) 

Standard Form 298 (Rev. 8/98) Prescribed by ANSI Std. Z39.18 

F1146-E(12/2004)