February 2003 • NREL/SR-510-31465

R.L. McCormick, J.R. Alvarez, and M.S. Graboski

Colorado Institute for Fuels and Engine Research 

Colorado School of Mines 

Golden, Colorado 

NOx Solutions for Biodiesel 

Final Report 

Report 6 in a series of 6 

National Renewable Energy Laboratory 

1617 Cole Boulevard 

Golden, Colorado 80401-3393 

NREL is a U.S. Department of Energy Laboratory 

Operated by Midwest Research Institute • Battelle • Bechtel 

Contract No. DE-AC36-99-GO10337 
February 2003 • NREL/SR-510-31465 

NOx Solutions for Biodiesel 

Final Report 

Report 6 in a series of 6 

R.L. McCormick, J.R. Alvarez, and M.S. Graboski

Colorado Institute for Fuels and Engine Research 

Colorado School of Mines 

Golden, Colorado 

NREL Technical Monitor: K.S. Tyson 

Prepared under Subcontract No. XCO-0-30088-01 

National Renewable Energy Laboratory 

1617 Cole Boulevard 

Golden, Colorado 80401-3393 

NREL is a U.S. Department of Energy Laboratory 

Operated by Midwest Research Institute • Battelle • Bechtel 

Contract No. DE-AC36-99-GO10337 
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 i

ACKNOWLEDGEMENT 

The authors of this report wish to acknowledge the assistance of CIFER staff members Jim 

Macomber, Bruce Sater, and Roger Ridley in the completion of the test work described here. 

Short chain fatty acid ester and TBHQ fuel additives were supplied by Dr. Michael Haas and Dr. 

Thomas Foglia of the Eastern Regional Research Center, Agricultural Research Service, USDA, 

Wyndmoor, PA. 
 ii

SUMMARY 

This study has examined a number of approaches for NOx reduction from biodiesel. Blending FT 

diesel at very high percentages can produce a NOx neutral fuel. Lowering the base fuel aromatic 

content from 31.9% to 7.5% (nominally 10% aromatic fuel) was very successful at lowering 

NOx. If all other factors are equal, and if the effect of aromatic content is linear, using a base fuel 

having 25.8% aromatics should provide a NOx neutral B20 (relative to certification diesel having 

nominally a 30% aromatic content). The results also suggest that using kerosene as the base fuel 

could lead to a NOx neutral blend (this occurs at 40% biodiesel, assuming linearity). The cetane 

enhancers di-tert-butyl peroxide (DTBP) and ethyl-hexyl nitrate (EHN) are both effective at 

reducing NOx from biodiesel. The antioxidant TBHQ is also effective but NOx reduction was 

small at the level tested and TBHQ may cause an increase in PM emissions. The idea of using 

antioxidants as NOx reduction additives is clearly something that should be explored in more 

detail. Blending of 2% short chain fatty acid esters was not effective for reducing NOx. The A1 

additive obtained from Bioclean Fuels was effective at NOx reduction but caused an 

unacceptably large increase in PM. Based on these results, use of the additives DTBP and EHN 

is the most practical approach at the present time. Using DTBP at 1 volume percent produces an 

incremental cost increase of $0.16 per gallon. For EHN at 0.5 volume percent the incremental 

cost increase per gallon is $0.05. 

A nominally 10% aromatic fuel was used as a reference point to determine if B20 blends (blends 

of either biodiesel with certification diesel or 10% aromatic diesel) might have emissions levels 

allowing CARB certification. The 10% aromatic fuel met the requirements for sale of diesel fuel 

in California based on composition, it was not a CARB reference diesel. All of the B20 blends 

exhibited PM emissions below those for the CARB diesel. Fuels based on certification diesel did 

not in any case produce NOx emissions equal to or below those of the 10% aromatic fuel. Even 

B20 fuels treated with DTBP have NOx emissions that significantly exceed those of the 10% 

aromatic diesel. For B20 blends based on the 10% aromatic fuel, adding DTBP is effective at 

reducing NOx to the base fuel level. Thus blending biodiesel with a California compliant diesel 

and treating with DTBP may be a route to a CARB certifiable B20. 

Degree of unsaturation appears to be the key difference between soy and yellow grease (YG) 

based biodiesels from the standpoint of emissions performance. The iodine numbers of these 

fuels were 127 and 79, respectively. The cetane number of the YG fuel was correspondingly 

higher. For the B20 blends a significant (about 2%) NOx increase relative to certification diesel 

was observed for soy but no significant increase was observed for YG. Treatment with 1% 

DTBP lowered NOx by about the same amount for both blends. For B100 fuels, the PM 

emissions are approximately the same but YG (Bio3000) exhibits NOx emissions that are lower, 

relative to soy diesel, by nearly 0.4 g/bhp-h. Treatment of B100 fuels with DTBP is effective at 

reducing NOx, but not in proportion to the NOx reduction observed for B20 blends. The facts that 

the NOx reduction for DTBP is the same independent of biodiesel source, and decreases with 

increasing biodiesel content of the fuel seem important. These results may suggest that DTBP 

acts largely to lower the NOx produced by burning the petroleum diesel fuel.
 iii

TABLE OF CONTENTS 

ACKNOWLEDGEMENT............................................................................................................. i

SUMMARY ................................................................................................................................... ii

TABLE OF CONTENTS ............................................................................................................iii

LIST OF FIGURES ...................................................................................................................... v

LIST OF TABLES ....................................................................................................................... vi

INTRODUCTION......................................................................................................................... 1

METHODS .................................................................................................................................... 2

Fuels and Test Matrix................................................................................................................ 2

Task 1. Fuel Quality Testing:.................................................................................................. 2

Task 2. Baseline Regulated Emissions Tests: ......................................................................... 2

Task 3. Testing Fischer-Tropsch/Biodiesel Blends: ............................................................... 2

Task 4. Effectiveness of DTBP Additive in Soy B20: .............................................................. 2

Task 5. Effectiveness of DTBP in Other B20 Fuels:............................................................... 2

Task 6. DTBP Effectiveness in Soy B100: .............................................................................. 3

Task 7. DTBP Effectiveness in Yellow Grease B100:............................................................. 3

Task 8. Additive Testing for USDA Peoria:............................................................................ 3

Task 9. Additive Testing for USDA Philadelphia: .................................................................. 3

Task 10. Bioclean Fuels A1 Additive:..................................................................................... 3

Task 11. Bioclean Fuels A1 Additive-Further Tests:.............................................................. 3

Task 12. K50 Testing: ............................................................................................................. 3

Task 13. Draft Report Preparation:........................................................................................ 3

Task 14. Final Report: ............................................................................................................ 3

Fuel Property Measurement...................................................................................................... 3

Emissions Testing ...................................................................................................................... 4

Test Engine: ............................................................................................................................ 4

Regulated Gaseous Emissions Measurement: ........................................................................ 4

Particle Sampling for Mass: ................................................................................................... 4

Quality Control:...................................................................................................................... 5

RESULTS ...................................................................................................................................... 6

Base Fuel Properties.................................................................................................................. 6

Certification Fuel Tests and Other Controls ............................................................................ 6

Base Fuel Emissions.................................................................................................................. 9

Results for FT Diesel/Soy Diesel Blends................................................................................. 10

Results for DTBP Treated Fuels ............................................................................................. 13

Results for EHN Treated B20 Blends ..................................................................................... 18

Testing of USDA Philadelphia Additives................................................................................ 19

Testing of Bioclean Fuels Additive ......................................................................................... 21

Testing of K50 .......................................................................................................................... 22

DISCUSSION .............................................................................................................................. 25

Effect of Various NOx Reduction Strategies........................................................................... 25
 iv

Use of Cetane Improvers for Biodiesel NOx Reduction ......................................................... 25

Comparisons with 10% Aromatic Diesel................................................................................. 26

Comparison of Soy and YG Biodiesels.................................................................................... 26

CONCLUSIONS ......................................................................................................................... 28

APPENDIX A: ASTM PS121 SPECIFICATION FOR BIODIESEL FUELS ..................... 29

APPENDIX B: ENGINE TORQUE MAP................................................................................ 30

APPENDIX C: EMISSIONS DATA ......................................................................................... 31

APPENDIX D: REFERENCES................................................................................................. 39
 v

LIST OF FIGURES 

Figure 1. NOx and PM emissions results for certification fuel runs performed over the study. All 

data points represent the average of three or more hot start runs..................................... 8 

Figure 2. PM and NOx emissions for blends of FT diesel in soydiesel. ....................................... 11 

Figure 3. Relationship between DTBP blending level and NOx emissions in B20 (soy+cert)..... 15 

Figure 4. Effect of DTBP blending level on percent NOx reduction for B20 (soy+cert). ............ 15 

Figure 5. Comparison of B20 emissions with emissions for 10% aromatic diesel....................... 26 

Figure 6. Comparison of emissions for various soy and yellow grease biodiesel fuels. .............. 27 
 vi

LIST OF TABLES 

Table 1. Fuels utilized in this study. ............................................................................................... 2 

Table 2. DDC Series 60 engine specifications and mapping parameters. ...................................... 4 

Table 3. Results of fuel property testing for base fuels. ................................................................. 7 

Table 4. Results of GC-MS analysis of biodiesel samples for specific species. ............................ 8 

Table 5. Descriptive statistics for daily average NOx emissions from the 1991 DDC Series 60 

engine using EPA certification diesel, January campaign................................................ 9 

Table 6. Descriptive statistics for daily average PM emissions from a 1991 DDC Series 60 

engine using EPA certification diesel, Januray campaign................................................ 9 

Table 7. Descriptive statistics for daily average NOx emissions from the 1991 DDC Series 60 

engine using EPA certification diesel, March campaign.................................................. 9 

Table 8. Descriptive statistics for daily average PM emissions from a 1991 DDC Series 60 

engine using EPA certification diesel, March campaign.................................................. 9 

Table 9. Emissions testing results for base fuels1......................................................................... 10 

Table 10. Fuel property testing results for FT/Soydiesel blends. ................................................. 12 

Table 11. Lubricity test results (HFRR). ...................................................................................... 13 

Table 12. Emissions testing results for soy diesel/FT diesel blends. Reported results are the 

average of at least three hot start runs. ........................................................................... 13 

Table 13. Emissions summary for treatment of B20 (soy+cert) with DTBP, results are averages 

for three or more hot start runs. ...................................................................................... 14 

Table 14. Emissions summary for treatment of various B20 fuels with DTBP (1%), results are 

averages for three or more hot start runs. ....................................................................... 16 

Table 15. Fuel property testing results for B20 blends................................................................. 17 

Table 16. Emission testing results for B100 fuels with and without DTBP, results are average of 

3 or more hot runs........................................................................................................... 18

Table 17. Emissions testing results for EHN in B20 (soy+cert fuel), results are average of three 

or more hot start runs...................................................................................................... 19 

Table 18. Results of t-test for significance of differences in emissions for EHN containing fuels 

(Excel t-test tool, two-sample assuming equal variaances)............................................ 19 

Table 19. Emissions summary results for testing of USDA addtives in B20 (soy+cert), results are 

averages of three or more hot start runs. ........................................................................ 21 

Table 20. Emissions summary for testing of Bioclean Fuels additive A-1, results are average of 

three or more hot start runs............................................................................................. 22 

Table 21. Emissions summary for testing of kerosene/soydiesel blends, results are average of 

three or more hot starts. .................................................................................................. 23 

Table 22. Fuel property testing results for kerosne and K50 fuels. .............................................. 24 

Table 23. Effect of various fuel additives on NOx reduction for B20 (soy+cert)......................... 25 
 1

INTRODUCTION 

Biodiesel is an oxygenated diesel fuel made from vegetable oils and animal fats by converting 

the tri-glyceride fats to esters via various esterification processes. A number of studies have 

shown substantial particulate matter (PM) reductions for biodiesel and biodiesel blended with 

petroleum diesel (1) relative to petroleum diesel. However, most studies also show a significant 

increase in nitrogen oxides (NOx) emissions (1). The cause of this increase in NOx and solutions 

to this problem have been the subject of a considerable body of research under the DOE 

Biodiesel Program at the National Renewable Energy Laboratory (NREL). 

In a previous study for NREL (2,3), we examined biodiesels produced from a variety of realworld feedstocks as well as technical grade fatty acid methyl and ethyl esters. Emissions 

performance in a heavy-duty truck engine using the U.S. heavy-duty federal test procedure 

(transient test) was measured. The objective was to understand the impact of biodiesel chemical 

structure, specifically fatty acid chain length and number of double bonds, on emissions of NOx

and PM. It was found that the molecular structure of biodiesel could have a substantial impact on 

emissions. For neat biodiesels (B100), PM emissions were essentially constant at about 0.07 

g/bhp-h as long as density was less than 0.89 g/cm3 or cetane number was greater than about 45. 

NOx emissions increased with increasing fuel density or decreasing fuel cetane number. 

Increasing the number of double bonds, quantified as iodine number, correlated with increasing 

emissions of NOx. The properties of density, cetane number, and iodine number were highly 

correlated with one another. This result cannot be explained by the well-known NOx/PM tradeoff 

because PM remained constant but NOx changed with fuel properties. Thus the increase in NOx

emissions observed for some biodiesels and for blends of biodiesel in petroleum diesel is not 

driven by thermal NO formation. The study additionally found that for fully saturated fatty acid 

chains NOx emissions were lower than those for petroleum diesel. NOx increased with decreasing 

fatty acid chain length for tests using fuels with 18, 16, and 12 carbon chains. Biodiesel 

composed of technical grade C12 saturated carbon chains (methyl laurate) was NOx equivalent to 

certification diesel. Also, there was no significant difference in NOx or PM emissions for the 

methyl and ethyl esters of identical fatty acids. 

The results of the previous study suggest a number of approaches to reduce NOx emissions by 

modifying biodiesel properties. These might be implemented through chemical modification of 

the fatty acid chain or through plant breeding to develop oils with more suitable properties. In the 

present study, we have examined a number of potential fuel additive and fuel blending solutions 

to the NOx problem. These include blending with Fischer-Tropsch diesel and low aromatic 

diesel, as well as using several fuel additives. The goal of the study was to identify an approach 

for reducing the NOx emissions of soy-based biodiesel by 4% for a B20 blend. The additives 

tested include the cetane improvers di-tert-butyl-peroxide (DTBP) and 2-ethyl-hexyl-nitrate 

(EHN), short chain fatty acid esters, tert-butyl-hydroquinone (TBHQ, a food antioxidant), and a 

proprietary additive called A1 provided by BioClean Fuels. Tests were conducted with biodiesels 

produced from both soy and yellow grease. There were significant differences between the two 

biodiesel-fuels with respect to degree of saturation, cetane number, iodine number, and fuel 

density. Base fuels were certification diesel and a California compliant 10% aromatic diesel. 
 2

METHODS 

Fuels and Test Matrix

The fuels examined in this study are listed in Table 1. A 14-task statement of work defined the 

study design. The fuel testing tasks are outlined below. 

Table 1. Fuels utilized in this study. 

Fuel Lot Number Source 

Certification diesel 0KP05202 Phillips Specialty Chemical 

10% Aromatic diesel 0LP10A01 Phillips Specialty Chemical 

Kerosene (No. 1 diesel) Not provided Colorado Petroleum Company 

Fischer-Tropsch diesel Not provided Shell Oil Company (via NREL) 

Soy methyl ester B4-136 AG Environmental Products (Soygold) 

Yellow grease methyl ester Not provided Griffin Industries (Bio3000) 

Task 1. Fuel Quality Testing: 

The base fuels listed in Table 1 were obtained and submitted for analysis to insure that minimum 

standards were met. The specific standards were ASTM PS121 for the biodiesel fuels, ASTM 

D975 for the certification diesel, and CARB standards for the 10% aromatic fuel. 

Task 2. Baseline Regulated Emissions Tests: 

Each of the fuels listed in Table 1 was tested in the DDC Series 60 engine for emissions 

performance. Tests included one cold start and a minimum of three hot starts for all fuels except 

the 10% aromatic for which only three hot starts were conducted. 

Task 3. Testing Fischer-Tropsch/Biodiesel Blends: 

Pure Fischer-Tropsch and blends of 80% FT/20% Soy and 80% Soy/20% FT were tested. 

Samples of FT diesel containing 1%, 3%, and 5% soy were submitted for lubricity analysis. The 

sample having the lowest soy diesel level that met the Engine Manufacturers Association 

recommended maximum High Frequency Reciprocating Rig (HFRR) wear scar maximum of 450 

microns was also tested in the engine. 

Task 4. Effectiveness of DTBP Additive in Soy B20: 

A B20 prepared from soy and certification diesel was tested to demonstrate the NOx increase 

typically observed. This fuel was then treated at 0.5, 1.0, and 1.5 volume percent DTBP and 

these fuels tested in the engine. The objective was to identify a DTBP blending level that 

reduced NOx emissions by 4%. Earlier studies at Southwest Research Institute (SwRI) reported 

that EHN was not effective at reducing NOx from soydiesel. Tests were also conducted to 

confirm this result. 

Task 5. Effectiveness of DTBP in Other B20 Fuels: 

The following B20 fuels were prepared and tested both with and without the DTBP additive at 

the treat rate determined in Task 4: 

• Certification diesel/yellow grease 
 3

• 10% aromatic diesel/soy 

• 10% aromatic diesel/yellow grease 

Task 6. DTBP Effectiveness in Soy B100: 

Neat soydiesel was tested using five times the DTBP treat rate determined for B20 in Task 4. 

Task 7. DTBP Effectiveness in Yellow Grease B100: 

Neat yellow grease biodiesel was tested using five times the DTBP treat rate determined for B20 

in Task 4. 

Task 8. Additive Testing for the U.S. Department of Agriculture (USDA), Peoria: 

This task was not funded and therefore not performed. 

Task 9. Additive Testing for USDA Philadelphia: 

Dr. Michael Haas and Dr. Thomas Foglia of USDA Eastern Regional Research Center supplied 

Colorado School of Mines (CSM) with two fuel additives. These were a sample of short chain 

fatty acid methyl esters (USDA-1) and a food antioxidant, tert-butyl-hyroquinone (USDA-2). A 

B20 prepared from certification diesel and soy diesel was tested using these additives at treat 

rates recommended by Drs. Haas and Foglia. 

Task 10. Bioclean Fuels A1 Additive: 

Bioclean Fuels provided a proprietary additive called A1. A1 was tested in a B20 prepared from 

10% aromatic fuel and soy diesel at a treat rate recommended by Bioclean Fuels. 

Task 11. Bioclean Fuels A1 Additive-Further Tests: 

The A1 additive was tested in a B20 prepared from certification diesel and soy diesel at a treat 

rate identical to that used in Task 10. A second test using soy B100 was planned. Upon direction 

from Dr. Shaine Tyson of NREL this second test was not performed. 

Task 12. K50 Testing: 

A blend of kerosene (No. 1 diesel) with 50% volume percent soydiesel and known as K50 was 

tested. Neat kerosene was also tested for comparison. K50 was then tested using 2.5 times the 

treat rate of the best NOx reducing additive identified in previous tests with B20. 

Task 13. Draft Report Preparation: 

A draft final report is to be prepared and submitted to NREL as well as to several peer reviewers. 

Task 14. Final Report: 

Based on reviewers comments, the final report is to be revised and a final version submitted. 

Fuel Property Measurement 

Williams Laboratory in Kansas City, Missouri performed fuel property measurements with the 

following exceptions. Core Laboratory in Houston, Texas performed analysis of the FT diesel. 

Analysis of the soy and yellow grease biodiesels for fatty acid ester content was performed by 

the Eastern Regional Research Center of the USDA in Wyndmoor, Pennsylvania. Southwest 
 4

Research Institute of San Antonio, Texas conducted lubricity tests using the HFRR (high 

frequency reciprocating rig) test (ASTM-D6079 @ 60°C). 

Emissions Testing 

The system for emissions measurement for regulated pollutants (THC, CO, NOx, and PM) 

includes supply of conditioned intake and dilution air, an exhaust dilution system, and capability 

for sampling of particulate and analysis of gaseous emissions. All components of the emissions 

measurement system meet the requirements for heavy-duty engine emissions certification testing 

as specified in Code of Federal Regulations Title 40, Part 86, Subpart N. 

Test Engine: 

The engine is a 1991 calibration Series 60 production model loaned by the Detroit Diesel 

Corporation. The six cylinder, four stroke engine is nominally rated at 345 bhp (257 kW) at 1800 

rpm and is electronically controlled (DDEC-II), direct injected, turbocharged, and intercooled. 

Engine specifications are listed in Table 2. This is the engine model specified in California Code 

of Regulations Title 13 section 2282, subsection g for certification testing of diesel fuels. 

Table 2. DDC Series 60 engine specifications and mapping parameters. 

Serial Number 6R-544 

Displacement 11.1 L 

Rated Speed/Horsepower 1800 rpm/345 bhp 

Max Torque Speed/Max Torque 1200 rpm/1335 ft-lb 

Idle Speed/CITT 600 rpm/0 ft-lb 

High Idle Speed 1940 rpm 

Intake Depression -16 ± 1 in H2O 

Backpressure 32.6 ± 3 in H2O 

Aftercooler Dp 40 ± 3 in H2O 

Intake Manifold Temperature 44±2°C 

Regulated Gaseous Emissions Measurement: 

All gas mass emissions are determined by background corrected flow compensated integration of 

the instantaneous mass rates. Tedlar bag samples of background air and exhaust sample are also 

collected. The exhaust sample is proportionally sampled through a critical flow orifice. The bag 

compositions are compared with the bag equivalent flow compensated emissions to validate the 

test runs. Agreement is always within 5% for the individual regulated gaseous emissions. 

Particle Sampling for Mass: 

Particulate matter is collected on Pallflex T60A20 70 mm filters of a common lot. Particulate 

matter is sampled through a secondary tunnel that insures a filtered gas temperature below 52°C 

(126°F). Two independent mass flow controllers are used to regulate the total filtered gas sample 

and the secondary dilution air rate. The computer determines the total sample volume by 

integrating the instantaneous flow difference. Flow is made proportional to the diluted exhaust 

by sending a varying secondary air flow set point from the test manager computer which is based 

upon the critical flow venturi (CFV) flow rate which in turn is a function of the diluted exhaust 

temperature at the venturi. The apparent sample flow rate depends on zero flow analog voltage 
 5

outputs from the transmitters. These are logged before and after the test and the corrected 

integrated volume is established with a calibration model that considers the voltage offsets. 

PM Background. Parallel background samples are not collected. Instead, the intake air is filtered 

to 95% ASHRAE efficiency and periodic background checks are made. Demineralized water is 

used for humidity control. The mass collected in the background check made during this 

program was extremely small. No background correction was made to the particulate 

determinations. 

Weigh Room Conditions. Since the PM mass collected, especially for the biodiesel samples, was 

small even minor differences in filter weight due to water adsorption can impact the particulate 

mass emission. Particle filter handling and weighing is conducted in a yellow light, constant 

humidity weigh room held at 9±2°C (48±4°F) dew point, 50% nominal relative humidity, and 

22±1°C (72±2°F). 

Quality Control: 

The testing is carried out in accordance with 40 CFR Part 86 Subpart N. In addition, a number of 

additional measures are taken to insure that the NOx and PM emissions collected in this program 

are both precise and accurate. 

Emission Gas Standards. Emission gases are 1% EPA Protocol Standards. Gas standards were 

not changed during this test program. 

Carbon Balance. As a test quality-assurance check, a carbon balance is performed for each 

transient test. Diesel mass fuel consumption was monitored with a Micromotion DP-25 mass 

flow sensor and by weighing the fuel supply tank before and after a test using a load cell. 

Exhaust carbon is determined from the background corrected THC, CO, CO2, and PM emissions 

data. The fuel analysis is used to estimate the H/C ratio of the THC. PM is assumed to be 100% 

carbon. Runs where carbon balance closure was more than +/-6% in error were generally 

rejected. 

NOx Humidity Correction. Humidity has a large influence on NOx emissions. Humidity is 

measured continuously in the conditioned air inlet by two independently calibrated methods: a 

dew point meter and a polymer membrane sensor. Furthermore, the intake air is controlled to a 

53°F (11.7°C) nominal dew point to insure that the NOx correction factor (40 CFR 1342-

94(d)(8)(iii)) is very near one and essentially constant from test to test. The two humidity 

measurements do not produce NOx correction factors that differ by more than 2%. 

The Effect of Intake Manifold Temperature on NOx Emissions. The engine is equipped with a 

water-cooled turbocharger intercooler. The supply temperature and flow rate of cooling water to 

the intercooler are adjusted during the engine mapping process to match the manufacturer’s 

design temperature for the intake air at rated speed and wide open throttle. The flow and inlet 

temperature are feedback controlled so that the temperature history of the manifold from test to 

test is repeatable. The maximum temperature and stage where it occurred are logged during each 

test to confirm that NOx differences are not related to variations from test to test in the intake air 

temperature profile. 
 6

RESULTS 

Base Fuel Properties 

Base fuel properties and testing methods employed are listed in Table 3. Certification diesel has 

a cetane number of 47 and an aromatic content of 32%. The nominally 10% aromatic diesel has a 

cetane number of 48 and an aromatic content of 7.5%. Note that this fuel is not a CARB 

reference diesel nor is it a fuel certified as emissions equivalent to CARB reference diesel. As a 

fuel with less than 10% aromatic content it meets the requirements for sale in California based on 

composition. Comparison of biodiesels and biodiesel blends with this fuel is intended to provide 

an estimate of suitability of any of these fuels for possible CARB certification. FT diesel has an 

extremely high cetane number, as is typical for these fuels. While not measured, the aromatic 

content of FT diesel is zero. For the biodiesel fuels all of the property specifications of ASTM 

PS121 (shown in Appendix A) are met. Soygold has a cetane number of 47; a value regarded as 

typical for a soy-derived biodiesel (1). The cetane number of Bio3000 is 56. The kerosene or No. 

1 diesel is at the light end of the No. 1 diesel range, and may even meet the specifications of a jet 

fuel. 

The fatty acid makeup of the two biodiesels was also determined and these results are reported in 

Table 4. As expected, the yellow grease fuel contained significantly higher levels of saturated 

and monounsaturated compounds. The “other” column in Table 4 includes unidentified peaks in 

the chromatogram and less than 0.5% of the 20:0 methyl ester. 

Certification Fuel Tests and Other Controls 

The engine was initially mapped on certification diesel fuel and this map (run 5629) was used to 

generate the transient test for all testing on all fuels. A plot of the torque map is shown in 

Appendix B. All emissions testing data for this study are presented in Appendix C, in 

chronological order. Certification fuel runs were performed periodically throughout the test 

program to gauge engine drift. A single lot of certification diesel was used. The testing was 

performed in two campaigns. The first campaign occurred in January 2001 and the second 

campaign in March and early April 2001. Figure 1 shows daily average NOx and PM emissions 

from the certification diesel runs. The two test campaigns are evident. A small (about 2%) 

difference in NOx emissions on certification fuel was observed between the two campaigns. This 

most likely occurred because of repairs made to the NOx analyzer during February, although drift 

of the engine itself cannot be ruled out. Certification fuel PM emissions are also slightly higher 

for the second campaign, although experimental variability is higher in the first campaign. 

Tables 5 through 8 present descriptive statistics for the certification fuel runs in both campaigns. 

Within a given campaign the data are of high repeatability with 95% confidence interval for NOx

of better than ±1% and for PM of better than ±5%. A t-test comparing NOx emissions for the two 

campaigns indicates that they are significantly different at better than 99% confidence 

(p<0.0001). PM emissions for the two campaigns are likely identical (p=0.119). In analyzing the 

data, runs will only be compared with certification fuel runs obtained during the same campaign. 
 7

Table 3. Results of fuel property testing for base fuels. 

Property Method Units 

Certification 

Diesel 

10% 

Aromatic 

Diesel 

FT Diesel Soygold Bio-3000

No. 1 

Diesel 

Cetane Number (CN) ASTMD613-86 47.4 48.2 >74.8 47.4 55.6 42.8 

Cetane Index ASTM-D975 48.3 49.4 78.3 -- -- 45.8 

Kinematic Viscosity 

40C 

ASTM-D445 mm2/s 2.7 2.5 3.34 4.066 4.735 1.3 

Iodine Number ASTMD1959 -- -- -- 127.4 78.8 -- 

Cloud Point ASTMD2500 F 3 -20 40 -- -- -61 

Cloud Point ASTMD5773 C -- -- -- -1 7 -- 

Flash Point ASTM-D93 F 153 135 228 288 284 130 

Cold Filter Plugging 

Point 

ASTM-6371 C -- -- 0 -3 3 -- 

Pour Point ASTM-D97 F 0 -- -- -- -- -- 

Total Sulfur by UVF ASTMD5453 wt% -- -- -- 0.000068 0.001468 -- 

Sulfur ASTMD2622 wt% 0.043 0.0057 -- -- -- 0.0138 

Ash Content ASTM-D482 wt% -- -- 0.001 -- -- 0.001 

Sulfated Ash ASTM-D874 wt% 0.003 0.01 -- 

Water Content ASTMD1796 -- -- <0.05 -- -- -- 

Specific Gravity ASTMD4052 0.8476 0.8302 -- -- -- ---- 

Carbon Residue ASTM-D189 wt% -- -- <0.01 -- -- -- 

Carbon Residue ASTM-D524 wt% -- -- -- 0.08 0.05 0.06 

Corrosion, Copper 

strip 

ASTM-D130 1A 1A 1A 1A 1A -- 

Water and Sediment ASTMD2709 vol% -- -- -- <0.005 <0.05 <0.05 

Acid Number ASTM-D664 mgKOH/

g 

-- -- -- 0.03 0.37 -- 

Hydrocarbon Type: ASTMD1319  

Aromatics %vol 31.9 7.5 -- -- -- -- 

Olefins %vol 1.5 2.1 -- -- -- -- 

Saturates %vol 66.6 90.4 -- -- -- -- 

Free Glycerin wt% 0.004 0.016 

Total Glycerin 

ASTM 

D6584 wt% 0.184 0.038 

Distillation ASTM-D86 

IBP F 352 355 454 -- -- 338 

10 F 423 421 500 -- -- 365 

50 F 514 478 556 -- -- 407 

90 F 599 599 618 -- -- 471 

EP F 642 658 638 -- -- 515 
 8

Table 4. Results of GC-MS analysis of biodiesel samples for specific species. 

Fuel C12:0 C14:0 C16:0 C16:1 C18:0 C18:1 C18:2 C18:3 Other

MW 214.351 242.405 270.459 268.443 298.513 296.497 296.497 294.481 

Unsaturations 0 0 0 1 0 1 2 3 

Soygold 0 0 11.96 0 3.88 22.63 54.52 6.6 0.41 

Bio3000 0 0.93 23.30 1.28 9.73 49.65 15.11 0 0 

Testing Date

1/1/2001 2/1/2001 3/1/2001 4/1/2001 5/1/2001

NOx Emissions, g/bhp-h

4.00

4.25

4.50

4.75

5.00

5.25

5.50

Mean NOx=4.723+/-0.041 Mean NOx=4.824+/-0.029

Testing Date

1/1/2001 2/1/2001 3/1/2001 4/1/2001 5/1/2001

PM Emissions, g/bhp-h

0.15

0.20

0.25

0.30

0.35

0.40

Certification Diesel

B20 (Soy+Cert)

Certification Diesel

B20 (Soy+Cert)

Mean PM=0.248+/-0.012 Mean PM=0.260+/-0.007

Figure 1. NOx and PM emissions results for certification fuel runs performed over the study. All 

data points represent the average of three or more hot start runs. 
 9

Also shown in Figure 1 are emissions results for a B20 prepared from soydiesel and certification 

diesel. These runs serve as an additional control. In all cases B20 NOx emissions are between 2% 

and 3% higher than average certification fuel NOx. B20 PM emissions are always at least 20% 

lower than certification fuel PM. Analysis of the fuel additive testing data will be based on a 

comparison of emissions with average B20 runs performed during the same campaign. 

Table 5. Descriptive statistics for daily 

average NOx emissions from the 1991 DDC 

Series 60 engine using EPA certification 

diesel, January campaign. 

Mean 4.7228

Standard Error 0.0189

Median 4.7339

Standard Deviation 0.0683

Range 0.206

Minimum 4.6017

Maximum 4.8073

95% Confidence Interval 0.0413

Count 15

Table 6. Descriptive statistics for daily 

average PM emissions from a 1991 DDC 

Series 60 engine using EPA certification 

diesel, Januray campaign. 

Mean 0.2482

Standard Error 5.589e-3

Median 0.2460

Standard Deviation 0.0202

Range 0.0676

Minimum 0.2192

Maximum 0.2868

95% Confidence Interval 0.0122

Count 15

Table 7. Descriptive statistics for daily 

average NOx emissions from the 1991 DDC 

Series 60 engine using EPA certification 

diesel, March campaign. 

Mean 4.8241

Standard Error 0.0125

Median 4.8407

Standard Deviation 0.0374

Range 0.1067

Minimum 4.7458

Maximum 4.8525

95% Confidence Interval 0.0288

Count 11

Table 8. Descriptive statistics for daily 

average PM emissions from a 1991 DDC 

Series 60 engine using EPA certification 

diesel, March campaign. 

Mean 0.2599

Standard Error 2.981e-3

Median 0.2603

Standard Deviation 8.941e-3

Range 0.0258

Minimum 0.2488

Maximum 0.2746

95% Confidence Interval 0.0069

Count 11

Base Fuel Emissions 

The base fuels for this study were tested for emissions in replicate transient tests. Results are 

reported in Table 9. A lubricity additive called Paradyne 655 was added to the FT diesel at 200 

ppm to protect the engine during testing of this fuel. FT diesel is shown to provide significant 

emissions reductions relative to certification diesel and 10% aromatic diesel. Both soy-based 

biodiesel (Soygold) and yellow grease-based biodiesel (Bio3000) show a significant NOx

increase relative to certification fuel, as well as the PM decrease typical of these fuels. The 

kerosene or No. 1 diesel exhibited NOx emissions similar to the 10% aromatic fuel but had 

significantly lower PM. Importantly, the coefficient of variation for NOx measurements was 

always below 1%. 
 10

Table 9. Emissions testing results for base fuels1. 

Fuel THC NOx CO CO2 PM 

 g/bhp-h g/bhp-h g/bhp-h g/bhp-h g/bhp-h

Cert Lot # 0KP05202 Composite 0.020 4.847 4.865 578 0.232 

January 3, 2001 Average Hot 0.020 4.773 4.604 574 0.233 

 Coefficient of Variation 16.7% 0.4% 1.0% 0.2% 1.8% 

Campaign 1 Average Hot 0.020 4.723 5.029 574 0.248 

Campaign 2 Average Hot 0.020 4.824 5.110 571 0.260 

Shell FT/Paradyne Composite 0.008 4.093 4.036 551 0.176 

Average Hot 0.007 4.026 3.843 548 0.167 

 Coefficient of Variation 73.8% 0.2% 4.4% 0.2% 4.6% 

Soygold Composite 0.014 5.449 3.155 580 0.072 

Average Hot 0.012 5.366 2.973 576 0.068 

 Coefficient of Variation 10.8% 0.2% 2.5% 0.2% 5.5% 

Bio3000 Composite 0.006 5.065 3.289 580 0.083 

Average Hot 0.004 4.981 3.105 576 0.078 

 Coefficient of Variation 71.0% 0.7% 4.3% 0.5% 8.4% 

10%Aro Lot#0LP10A01 Average Hot 0.029 4.478 4.980 569 0.231 

 Coefficient of Variation 24.0% 0.2% 3.1% 0.2% 2.8% 

Kerosene Average Hot 0.086 4.527 4.005 554 0.199 

 Coefficient of Variation 5.1% 0.3% 1.7% 0.1% 2.4% 

1

Composite is the weighted average (1/7 cold+6/7hot average) and include a minimum of 3 hot 

start runs. Hot average is for 3 or more hot start runs. 

Results for FT Diesel/Soy Diesel Blends 

The objective of Task 3 of this project was to quantify the regulated emissions from different 

blends of biodiesel with Fischer-Tropsch (FT) diesel in compression ignition engines. Based on 

previous correlations between fuel density and NOx, blending of a low-density diesel fuel with 

biodiesel was hypothesized to provide a NOx reduction. Because Fischer Tropsch diesel also has 

high cetane and no aromatics, the impact of changing density could not be isolated, but it could 

be examined. Biodiesel has excellent lubricity properties, while FT diesel has poor lubricity. The 

combination of the two low-sulfur diesel fuels might provide a very low emission alternative fuel 

with excellent lubricity properties. 

Fuel property testing results for neat FT diesel, biodiesel (Soygold), and certification fuel as well 

as the different biodiesel-FT blends are presented in Table 10. After blending to 20% soy in FT, 

the cetane number still exceeds 75. Blending 20% FT into soy increases cetane number to 53.3 

and using a linear model suggests a blending cetane number for FT diesel of 77. If this were 

correct, the 20% soy in FT blend would have a calculated cetane number of 71. Cetane number 

measurements above about CN=65 are notoriously inaccurate and within this limitation the 

results are reasonably consistent. Blending soydiesel with FT diesel acts to depress cloud point 

and cold filter plugging point by a few degrees. Table 11 present HFRR lubricity data for several 

blends of biodiesel and FT diesel. The Engine Manufacturers Association recommends a 

maximum HFRR wear scar of 450 microns. A previous report indicates that the Shell FT diesel 

produces HFRR wear scar of more than 500 microns and that addition of 200 ppm of the 
 11

Paradyne 655 lubricity additive reduces this to 210 (4). The average value for 1% biodiesel in FT 

is 300 micron (or 0.300 mm), well below the manufacturers recommended limit. Based on 

direction from Mr. Keith Vertin at NREL, a 1% biodiesel/FT diesel blend was selected for 

testing, along with the FT/B20 and FT/B80 blends specified in our contract. 

The emissions testing results for the different runs are presented in Table 12. The coefficients of 

variation for NOx and PM measurements were always below 1% and 6% respectively. Emissions 

of FT diesel and FT diesel with 1% biodiesel are essentially identical, as expected. Adding 20% 

or larger amounts of biodiesel to FT results in a significant increase in NOx emissions and 

decrease in PM emissions. Note, however, that for FT/B20 the NOx emission is still 0.5 g/bhp-h 

below the certification diesel level. There is a linear relation for both NOx and PM emissions as a 

function of volume percent FT diesel, as shown in Figure 2. The regression equations shown in 

the figure indicate that a blend of 46% FT with soydiesel would have the same NOx emissions as 

certification diesel. 

Percent FT Diesel

0 20 40 60 80 100

NOx, g/bhp-h

3.0

3.5

4.0

4.5

5.0

5.5

6.0

NOx

PM, g/bhp-h

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

PM

Int=5.34

Slope=-0.0133

r 2=0.998

Int=0.0625

Slope=0.0011

r 2=0.986

Figure 2. PM and NOx emissions for blends of FT diesel in soydiesel. 
 12

Table 10. Fuel property testing results for FT/Soydiesel blends. 

Property Method Units Cert fuel F-T Soygold 80%FT/20%SG 20%FT/80%SG

Cetane Number ASTM-D613-86 47.4 >74.8 47.4 >74.8 53.3 

Cetane Index ASTM-D975 48.3 78.3 N/A 70.5 52.2 

Kinematic Viscosity 

at 40 C 

ASTM-D445 mm2/s 2.7 3.34 4.066 3.346 3.822 

Iodine Number ASTM-D1959 127.4 29 97.4 

Cloud Point ASTM-D2500 F 3 40 35 31 

Cloud Point ASTM-D5773 C -1 

Cold Filter Plugging 

Point 

ASTM-6371 C 0 -3 -3 -4 

Pour Point ASTM-D97 F 0 

Flash Point ASTM-D93 F 153 228 288 219 227 

Total Sulfur by UVF ASTM-D5453 wt% 0.000068 

Sulfur ASTM-D2622 wt% 0.043 0.0014 0.0024 

Ash Content ASTM-D482 wt% 0.001 0 0 

Sulfated Ash ASTM-D874 wt% 0.003 

Water Content ASTM-D1796 <0.05 

Specific Gravity ASTM-D4052 0.8476 

API Gravity ASTM-D1298 44.6 32.9 

Carbon Residue ASTM-D189 wt% <0.01 

Carbon Residue 

Ramsbottom 

ASTM-D524 % 0.08 0.03 0.06 

Corrosion, Copper 

strip 

ASTM-D130 1A 1A 1A 1A 1A 

Water and Sediment ASTM-D2709 vol% <0.005 26.6 0 

Acid Number ASTM-D664 mgKOH/

g 

 0.03 

Hydrocarbon Type: ASTM-D1319 %vol 

Aromatics ASTM-D1319 %vol 31.9 

Olefins ASTM-D1319 %vol 1.5 

Saturates ASTM-D1319 %vol 66.6 

Distillation ASTM-D86 F 

IBP ASTM-D86 F 352 454 418 446 

10 ASTM-D86 F 423 500 500 570 

50 ASTM-D86 F 514 556 576 625 

90 ASTM-D86 F 599 618 628 638 

EP ASTM-D86 F 642 638 636 638 
 13

Table 11. Lubricity test results (HFRR). 

Sample Major Axis [mm]Minor Axis [mm] Wear Scar Diameter [mm]

80% Biodiesel in FT 0.16 0.10 0.130 

80% Biodiesel in FT 0.17 0.10 0.135 

80% Biodiesel in FT 0.17 0.10 0.135 

Average 0.133 

20% Biodiesel in FT 0.17 0.12 0.145 

20% Biodiesel in FT 0.19 0.10 0.145 

20% Biodiesel in FT 0.19 0.10 0.145 

Average 0.145 

5% Biodiesel in FT 0.21 0.15 0.180 

5% Biodiesel in FT 0.21 0.12 0.165 

5% Biodiesel in FT 0.21 0.15 0.180 

Average 0.175 

3% Biodiesel in FT 0.22 0.17 0.195 

3% Biodiesel in FT 0.22 0.16 0.190 

3% Biodiesel in FT 0.23 0.15 0.190 

Average 0.192 

1% Biodiesel in FT 0.32 0.26 0.290 

1% Biodiesel in FT 0.33 0.27 0.300 

1% Biodiesel in FT 0.35 0.27 0.310 

Average 0.300 

Table 12. Emissions testing results for soy diesel/FT diesel blends. Reported results are the 

average of at least three hot start runs. 

Fuel THC NOx CO CO2 PM 

 g/bhp-h g/bhp-h g/bhp-h g/bhp-h g/bhp-h

Shell FT w/Paradyne Average Hot 0.007 4.026 3.843 548 0.167 

 Coefficient of Variation 73.82% 0.21% 4.41% 0.24% 4.64% 

99%FT/1%Soygold Average Hot 0.004 4.035 3.915 550 0.177 

 Coefficient of Variation 96.75% 0.27% 2.52% 0.53% 3.64% 

80%FT/20%Soygold Average Hot 0.005 4.249 3.608 554 0.146 

 Coefficient of Variation 83.47% 0.40% 3.49% 0.29% 5.68% 

20%FT/80%Soygold Average Hot 0.006 5.048 2.986 571 0.078 

 Coefficient of Variation 10.17% 0.37% 3.02% 0.33% 5.40% 

Results for DTBP Treated Fuels 

The objective of Task 4 of this project was to quantify the effects of di-tert-butyl peroxide 

(DTBP) on regulated emissions from B-20 biodiesel (soy) blends. Tasks 5, 6, and 7 examined 

DTBP in other B20 blends as well as in the neat biodiesel samples. Previous testing using DTBP 

by Southwest Research Institute, showed that 0.5% and 1.0% volume DTBP treat rates reduced 

NOx emissions by approximately 1.1% and 5.2% compared to untreated B20 respectively (5,6). 

Unfortunately in neither case were the data useful in determining an effective DTBP treat rate to 

make the B20 NOx neutral, since the untreated B20 blend had lower NOx emissions than the 

baseline No. 2 diesel fuel. 
 14

A baseline of 6 hot starts for B20 soy biodiesel in certification fuel was initially established. 

Using only the certification fuel runs acquired immediately before and after acquisition of the 

B20 baseline, which averaged 4.754 g/bhp-h, the NOx increase is 3.3%. We prepared a series of 

B20 fuels (certification diesel + soydiesel) containing 0.5, 1.0, and 1.5 volume percent DTBP. 

Hot transient emissions summary results are presented in Table 13. The coefficients of variation 

for NOx and PM measurements were always below 1% and 6% respectively. DTBP was 

effective at reducing NOx at all three treatment-levels (all statistically significant at 95% 

confidence or greater). Figure 3 shows an approximately linear relationship between DTBP treat 

rate and NOx emissions. 

Percent NOx reduction (with respect to untreated B20) versus percent volume DTBP is shown in 

Figure 4 and exhibits an approximately linear relationship (p-value for slope=0.02). Based on the 

linear regression equation shown in Figure 4, an approximate 4% reduction should be achieved 

using 1% volume DTBP. The 95% confidence interval on the slope of the regression in Figure 4 

ranges from –6.23 to –1.42, thus the estimate of 1% volume DTBP is not very precise. 

Table 13. Emissions summary for treatment of B20 (soy+cert) with DTBP, results are averages 

for three or more hot start runs.

Fuel THC NOx CO CO2 PM 

 g/bhp-h g/bhp-h g/bhp-h g/bhp-h g/bhp-h

Certification Fuel Average Hot 0.016 4.734 5.049 574 0.236 

January 15, 2001 Coefficient of Variation 29.96% 0.18% 2.43% 0.0 1.32% 

B20 Soy in CERT fuel Average Hot 0.013 4.912 4.677 576 0.194 

Coefficient of Variation 76.55% 0.05% 3.38% 0.12% 4.00% 

Certification Fuel Average Hot 0.012 4.774 5.005 576 0.250 

January 18, 2001 Coefficient of Variation 32.09% 0.57% 1.62% 0.0 1.34% 

B20 Soy in CERT fuel Average Hot 0.005 4.792 4.414 574 0.197 

w/ 0.5% volume DTBP Coefficient of Variation 74.64% 0.25% 3.05% 0.22% 1.68% 

B20 Soy in CERT fuel Average Hot 0.016 4.754 4.436 575 0.210 

w/ 1.0 % volume DTBP Coefficient of Variation 11.32% 0.15% 1.01% 0.24% 2.32% 

B20 Soy in CERT fuel Average Hot 0.008 4.612 4.218 571 0.196 

w/ 1.5% volume DTBP Coefficient of Variation 83.58% 0.09% 1.82% 0.29% 2.78% 

Because DTBP was successful at reducing NOx from a B20 composed of soy biodiesel and 

certification diesel, additional tests were conducted on its effects on NOx emissions from the 

following B20 blends: 

 Soy in 10% aromatic fuel 

 Yellow grease in certification fuel 

 Yellow grease in 10% aromatic fuel 

Emissions summary results are presented in Table 14, along with some earlier results. The 

coefficients of variation for NOx and PM measurements were always below 1% and 4% 

respectively. DTBP was effective at reducing NOx emissions to the base fuel level or below (by 

3% to 4%) in all cases (significant at 95% confidence or greater). 
 15

Percent DTBP

0.0 0.5 1.0 1.5 2.0

NOX, g/bhp-h

4.55

4.60

4.65

4.70

4.75

4.80

4.85

4.90

4.95

Cert Fuel NOX

Figure 3. Relationship between DTBP blending level and NOx emissions in B20 (soy+cert). 

Percent DTBP

0.0 0.5 1.0 1.5 2.0

Percent Change in NO

X

-7

-6

-5

-4

-3

-2

-1

0

Intercept=-0.056

Slope=-3.822

r 2=0.959

Figure 4. Effect of DTBP blending level on percent NOx reduction for B20 (soy+cert). 
 16

Fuel property testing results for all of these B20 fuels are shown in Table 15. Adding 1% DTBP 

to B20 (Soy+Cert) increased cetane number from 48 to 60. The results in Table 15 indicate an 

even larger cetane boost for B20 (Soy+10%) diesel, from 48 to 67, although a cetane number of 

67 seems unreasonably high. However, cetane number for the yellow grease based B20 fuels did 

not increase significantly, even though a NOx reduction was observed. This observation was 

confirmed by retesting two of the yellow grease containing fuels. Williams Laboratory claims 

that the same person measures all cetane numbers. This result may imply that DTBP does not 

reduce NOx by increasing cetane number but by some other chemical effect. 

A 5% DTBP blending level was used for testing B100. Testing results are shown in Table 16, 

along with other results for completeness. Certification fuel NOx emissions averaged 4.82 g/bhph during Campaign 2 when these tests were conducted. Soy B100 increases NOx to 5.45 g/bhp-h. 

Adding DTBP results in a decrease to 5.18 g/bhp-h. This result represents a statistically 

significant NOx reduction, but it is still well above the certification fuel level. For yellow grease 

B100 (Bio3000) NOx is 5.07 g/bhp-h and adding 5% DTBP reduces NOx to 4.88 g/bhp-h. Again 

this NOx reduction is statistically significant, and has reduced NOx to the certification fuel level 

(emissions for the two fuels are the same with 97% confidence). 

Table 14. Emissions summary for treatment of various B20 fuels with DTBP (1%), results are 

averages for three or more hot start runs.

Fuel THC NOx CO CO2 PM 

 g/bhp-h g/bhp-h g/bhp-h g/bhp-h g/bhp-h

Certification Fuel Average Hot 0.02 4.723 5.011 573 0.248 

Coefficient of Variation 0.35% 1.03% 0.20% 1.93% 8.62% 

B20 (soy+cert) Average Hot 0.013 4.912 4.677 576 0.194 

Coefficient of Variation 76.55% 0.05% 3.38% 0.12% 4.00% 

B20 (soy+cert) Average Hot 0.016 4.754 4.436 575 0.210 

1.0 % volume DTBP Coefficient of Variation 11.32% 0.15% 1.01% 0.24% 2.32% 

B20 (YG+cert) Average Hot 0.009 4.780 4.658 577 0.208 

Coefficient of Variation 22.83% 0.19% 2.34% 0.0 2.67% 

B20 (YG+cert) Average Hot 0.009 4.637 4.498 574 0.208 

1.0 % volume DTBP Coefficient of Variation 75.98% 0.14% 4.23% 0.0 2.75% 

10% Aromatic Average Hot 0.029 4.478 4.980 569 0.231 

Coefficient of Variation 0.240 0.002 0.031 0.002 0.028 

B20 (Soy+10%) Average Hot 0.022 4.606 4.333 567 0.189 

Coefficient of Variation 13.68% 0.09% 4.07% 0.0 4.08% 

B20 (Soy+10%) Average Hot 0.016 4.469 4.445 569 0.201 

1.0 % volume DTBP Coefficient of Variation 24.00% 0.20% 2.13% 0.0 1.68% 

B20 (YG+10%) Average Hot 0.017 4.586 4.427 568 0.191 

Coefficient of Variation 17.21% 0.29% 1.61% 0.0 2.51% 

B20 (YG+10%) Average Hot 0.016 4.414 4.590 566 0.203 

1.0 % volume DTBP Coefficient of Variation 17.22% 0.24% 1.50% 0.0 0.37% 
 17

Table 15. Fuel property testing results for B20 blends.

Property Method Units B20 Soy/

CERT 

B20 

Soy/CERT+1

% DTBP 

B20 

Soy/10% 

Aromatic

B20 Soy/10% 

Aromatic+1% 

DTBP 

B20 

YG/CERT

B20 

YG/CERT+

1%DTBP 

B2

YG/1

Arom

Cetane Number (replicate) 

ASTM-D613-86 47.7 60 48 67.4 44.7 

(46.2) 

45.1 

(49.2) 

47

Cetane Index ASTM-D976 49.5 50.1 50.2 50.1 50Specific Gravity ASTM-D4052 0.852 0.8403 0.8383 0.852 0.8514 0.83Flash Point ASTM-D93 F 165 163 147.2 163 150 16Kinematic Viscosity(at 100F) 

ASTM-D445 mm2/s 2.88 2.702 5.054 2.918 2.855 2.7

Corrosion, Copper strip 

ASTM-D130 1A 1A 1A 1A 1A 1A 

Ash Content ASTM-D482 wt% 0.001 0 0.001 0.04 0.006 0 Carbon Residue Ramsbottom 

ASTM-D524 % 

carbon 

0.07 0.04 0.17 0.04 0.43 0.4

Cloud Point ASTM-D2500 F 10 -2 -2.2 14 16 1Sulfur ASTM-D2622 wt% 0.0263 0.0027 0.0037 0.0268 0.0258 0.00Water and Sediment ASTM-D2709 vol% 0 <0.05 0.01 <0.05 <0.05 <.0API Gravity ASTM-D1298 

/D287 

 36.8 34.5 34.6 37

Distillation ASTM-D86 F 

IBPASTM-D86 F 365 388 169 375 175 39

10ASTM-D86 F 437 431 433 446 440 4350ASTM-D86 F 542 511 510 548 545 5190ASTM-D86 F 631 640 649 632 635 64

FBPASTM-D86 F 654 658 656 659 652 65
 18

Table 16. Emission testing results for B100 fuels with and without DTBP, results are an average 

of 3 or more hot runs. 

Fuel THC NOx CO CO2 PM 

 g/bhp-h g/bhp-h g/bhp-h g/bhp-h g/bhp-h

Cert Fuel Average Hot 0.020 4.824 4.604 574 0.260 

Campaign 2 Avg Coefficient of Variation 16.7% 0.4% 1.0% 0.2% 1.8% 

Soygold Average Hot 0.012 5.366 2.973 576 0.068 

Coefficient of Variation 10.8% 0.2% 2.5% 0.2% 5.5% 

Soygold+5% DTBP Average Hot 0.027 5.184 2.470 556 0.064 

Coefficient of Variation 7.73% 0.61% 3.21% 0.06% 6.08% 

Bio3000 Average Hot 0.004 4.981 3.105 576. 0.078 

Coefficient of Variation 71% 0.7% 4.3% 0.5% 8.4% 

Bio3000+5% DTBP Average Hot 0.016 4.881 2.861 556 0.078 

Coefficient of Variation 12.43% 0.39% 5.22% 0.04% 6.54% 

Results for EHN Treated B20 Blends 

Studies conducted in 1994 at SwRI reported that EHN was not effective for NOx reduction when 

added to soy-based biodiesel (5,6). However, the biodiesel available at that time was likely of 

low quality (high methanol, glycerol, and glyceride content) and it would be interesting to repeat 

those tests using a fuel meeting the requirements of ASTM PS121. Tests were conducted using 

0.5% and 1.0% by volume EHN in B20 (soy+cert) and the results are shown in Table 17. Table 

18 shows the results of statistical tests to quantify the significance of any differences observed. 

When comparing B20 to B20 with EHN (0.5%), it clear that the observed 2.3% NOx reduction 

has a high degree of statistical significance. When comparing certification fuel emissions to 

B20+0.5% EHN is seems likely that EHN has reduced NOx to the certification fuel level. A set 

of runs was also performed with 1.0% EHN and the NOx in this case was statistically identical to 

that observed for 0.5%. Thus, our results do not replicate what was reported by SwRI however 

the SwRI study only tested EHN in a 2-stroke engine. In the present study with a 4-stroke engine 

both of the common cetane improvers, EHN and DTBP, reduced NOx from 

soydiesel/certification diesel blends. 
 19

Table 17. Emissions testing results for EHN in B20 (soy+cert fuel), results are average of three 

or more hot start runs. 

Fuel THC NOx CO CO2 PM 

 g/bhp-h g/bhp-h g/bhp-h g/bhp-h g/bhp-h

B20 (Soy+Cert) Average Hot 0.018 4.909 4.674 577 0.196 

January 15, 2001 Coefficient of Variation 6.95% 0.33% 3.28% 0.0 5.74% 

B20 (Soy+Cert) Average Hot 0.007 4.916 4.679 575 0.192 

January 17, 2001 Coefficient of Variation 76.55% 0.05% 3.38% 0.0 4.00% 

Certification Diesel Average Hot 0.041 4.830 5.106 557 0.249 

March 7, 2001 Coefficient of Variation 15.02% 0.73% 3.71% 0.31% 2.26% 

B20 (Soy+Cert) Average Hot 0.037 4.941 4.616 558 0.191 

March 7, 2001 Coefficient of Variation 18.23% 0.23% 1.36% 0.06% 1.11% 

Certification Diesel Average Hot 0.053 4.841 5.113 554 0.264 

March 12, 2001 Coefficient of Variation 2.76% 0.17% 1.37% 0.16% 2.42% 

B20 (Soy+Cert)+0.5% EHN Average Hot 0.024 4.834 4.529 558 0.212 

March 13, 2001 Coefficient of Variation 26.99% 0.39% 3.39% 0.11% 2.39% 

B20 (Soy+Cert)+1.0% EHN Average Hot 0.033 4.804 4.431 559 0.206 

March 13, 2001 Coefficient of Variation 13.16% 0.56% 1.58% 0.11% 1.90% 

Certification Diesel Average Hot 0.029 4.800 5.190 560 0.258 

March 14, 2001 Coefficient of Variation 6.83% 0.55% 2.03% 0.13% 4.00% 

Certification Diesel Average Hot 0.025 4.813 5.144 558 0.252 

April 10, 2001 Coefficient of Variation 12.10% 0.18% 2.51% 0.12% 0.68% 

B20 (Soy+Cert) Average Hot 0.023 4.913 4.784 558 0.201 

April 10, 2001 Coefficient of Variation 17.82% 0.61% 2.25% 0.12% 2.05% 

B20 (Soy+Cert)+0.5% EHN Average Hot 0.018 4.766 4.662 557 0.220 

April 10, 2001 Coefficient of Variation 9.62% 0.74% 2.22% 0.21% 9.59% 

B20 (Soy+Cert) Average Hot 0.018 4.877 4.714 558 0.193 

April 19, 2001 Coefficient of Variation 11.28% 0.18% 2.91% 0.18% 1.18% 

Table 18. Results of t-test for significance of differences in emissions for EHN containing fuels 

(Excel t-test tool, two-sample assuming equal variaances). 

 B20 NOx B20+EHN NOx p-value 

Compare untreated B20 to B20+0.5%EHN 4.9113 4.8002 6.87E-07

 

 Cert NOx B20+EHN NOx p-value 

Compare cert to B20+0.5% EHN 4.8257 4.8002 0.159907

Testing of USDA Philadelphia Additives 

Dr. Michael Haas and Dr. Thomas Foglia of USDA supplied two fuel additives: 

USDA-1: A fuel composed of 90% soy biodiesel and 10% short chain fatty acid esters. The 

USDA fuel was tested as a B20 blend, with the final fuel composed of 80% certification diesel, 

2% short chain esters, and 18 % soy diesel. The composition of the short chain ester mixture 

was: 
 20

 Methyl butyrate 411 ml (41.1 volume %) 

 Methyl caproate 265 ml (26.5 volume %) 

 Methyl caprylate 92 ml (9.2 volume %) 

 Methyl decanoate 233 ml (23.3 volume %) 

This mixture was selected because in our previous study (2) it was demonstrated that shorter 

chain, saturated esters had lower NOx emissions than the long chain unsaturated esters that are 

dominant in soy diesel. This was true even though NOx emissions increased for saturated esters 

when the chain length was shortened. 

USDA-2: A fuel composed of 100% soy biodiesel and 1% tert-butyl-hydroquinone, a food 

antioxidant (also known as TBHQ). The fuel was tested as a B20 with certification diesel; the 

blended fuel contained 0.2 wt% TBHQ. This additive was selected because in our previous study 

(2) it was shown that the increase in NOx is not driven by thermal or Zeldovich NOx formation 

and therefore may involve some pre-combustion chemistry of hydrocarbon free radicals. An antioxidant might react with these free radicals preventing their participation in a NOx forming 

sequence of reactions. 

Emissions summary results for these two fuel blends are presented in Table 19, along with some 

additional results for completeness. The coefficients of variation for NOx and PM measurements 

were always below 1.4% and 4% respectively. The statistical analysis of the results reported here 

utilizes only certification fuel runs and untreated B20 runs from March and early April, 2001. 

USDA-1: Certification fuel runs performed before and after testing of this additive in B20 

averaged 4.85 g/bhp-h. The NOx emission for the USDA-1 fuel was 5.012. The average 

untreated B20 NOx was 4.93. The 3% increase in NOx observed for USDA-1 is statistically 

significant at 98% confidence (p=0.01608). PM emissions are unchanged relative to B20. Thus, 

USDA-1 was not effective for NOx reduction. USDA-1 had no significant impact on PM 

emissions. 

USDA-2. Certification fuel runs performed before and after testing this B20 averaged 4.840 

g/bhp-h of NOx. The NOx emission for the USDA-2 fuel was 4.894 g/bhp-h, 0.044 g/bhp-h 

higher than the bracketing certification fuel mean which is significantly higher at 99% 

confidence. The USDA-2 NOx is 0.035 g/bhp-h lower than the mean B20 NOx of 4.93. This NOx

reduction is significant at 99.5% confidence (p=0.005532) but apparently the treat rate of 0.2wt% 

is not adequate to reduce NOx to the certification fuel level. TBHQ also had a negative effect on 

PM, causing PM to increase by 9% relative to the average B20 PM emission for the second 

testing campaign (significant at 99% confidence). This level of PM is still significantly below the 

PM emission level of certification diesel. Additional testing of TBHQ and other antioxidants is 

clearly warranted. 
 21

Table 19. Emissions summary results for testing of USDA addtives in B20 (soy+cert), results are 

averages of three or more hot start runs.

Fuel THC NOx CO CO2 PM 

 g/bhp-h g/bhp-h g/bhp-h g/bhp-h g/bhp-h

B20 Soy/Cert fuel Average Hot 0.037 4.941 4.616 558 0.191 

March 7, 2001 Coefficient of Variation 18.23% 0.23% 1.36% 0.06% 1.11% 

Cert Fuel Average Hot 0.036 4.853 5.283 560 0.260 

March 28, 2001 Coefficient of Variation 3.36% 0.07% 3.53% 0.07% 1.39% 

B20 (Soy)/USDA-1 Average Hot 0.030 5.012 4.719 562 0.192 

March 28, 2001 Coefficient of Variation 8.23% 1.31% 2.30% 0.22% 2.16% 

Cert Fuel Average Hot 0.034 4.847 5.102 559 0.238 

April 4, 2001 Coefficient of Variation 13.15% 0.04% 2.26% 0.24% 2.15% 

B20 (Soy)/USDA-2 Average Hot 0.028 4.894 4.846 560 0.214 

April 5, 2001 Coefficient of Variation 9.74% 0.26% 2.84% 0.18% 3.35% 

Cert Fuel Average Hot 0.030 4.852 5.386 559 0.232 

April 6, 2001 Coefficient of Variation 11.31% 0.59% 4.09% 0.23% 3.16% 

B20 Soy/Cert fuel Average Hot 0.023 4.913 4.784 558 0.201 

April 10, 2001 Coefficient of Variation 17.82% 0.61% 2.25% 0.12% 1.98% 

Testing of Bioclean Fuels Additive 

The objective of Task 10 of this project was to test a B20 produced from soy and 10% aromatic 

diesel and containing the A-1 additive from Bioclean Fuels. Task 11 was to perform similar tests 

on B20 produced from soy and certification diesel, and on B100 soy. Based on the testing 

results, the NREL technical monitor (Dr. Shaine Tyson) directed us not to perform the B100 test. 

This section presents emissions results for the two fuels tested with A-1. 

The B20 fuels were prepared, as directed by Bioclean Fuels, to contain 1 part in 40 of the liquid 

A-1 additive. The emissions summary results are presented in Table 20 along with some results 

from other tasks for completeness. The coefficients of variation for NOx and PM measurements 

were always below 1% and 4% respectively. 

A-1 in CARB/B20: NOx emissions from CARB diesel were 4.48 g/bhp-h and increased to 4.61 

g/bhp-h upon addition of 20-volume percent soy diesel. Adding A-1 produced NOx emissions of 

4.56 g/bhp-h, which represents no change in NOx emissions at the 99% confidence level. Adding 

A-1 caused PM to increase from 0.189 to 0.237 g/bhp-h; essentially eliminating any PM benefit 

from the biodiesel. 

A-1 in Cert/B20: NOx emissions for certification diesel ran about 4.85 g/bhp-h during late March 

and early April. Adding 20% soy diesel increased this to 4.91 g/bhp-h. Adding A-1 produced a 

NOx emission of 4.84 g/bhp-h, indicating that A-1 successfully reduced NOx by about 2% for 

this fuel. However, PM emissions were about 0.23 g/bhp-h. This is identical to PM emissions 

from certification diesel on bracketing runs and significantly higher than the 0.201 g/bhp-h 

measured for B20 shortly thereafter. This indicates that A-1 eliminates the PM benefit of using 

biodiesel. 
 22

Table 20. Emissions summary for testing of Bioclean Fuels additive A-1; results are an average 

of three or more hot start runs.

Fuel THC NOx CO CO2 PM 

 g/bhp-h g/bhp-h g/bhp-h g/bhp-h g/bhp-h

10% Aromatic Average Hot 0.029 4.478 4.980 569 0.231 

January 12, 2001 Coefficient of Variation 24.05% 0.17% 3.13% 0.0 2.84% 

B20 Soy/10% Aro Average Hot 0.022 4.606 4.333 567 0.189 

January 23, 2001 Coefficient of Variation 13.68% 0.09% 4.07% 0.2% 4.08% 

B20 Soy/Cert fuel Average Hot 0.037 4.941 4.616 558 0.191 

March 7, 2001 Coefficient of Variation 18.23% 0.23% 1.36% 0.06% 1.11% 

Cert Fuel Average Hot 0.034 4.746 5.091 555 0.260 

March 26, 2001 Coefficient of Variation 16.63% 0.42% 2.23% 0.14% 1.40% 

B20 Soy/10% Aro+A1 Average Hot 0.040 4.563 4.949 554 0.237 

March 26, 2001 Coefficient of Variation 6.54% 0.10% 1.79% 0.26% 2.30% 

Cert Fuel Average Hot 0.036 4.853 5.283 560 0.260 

March 28, 2001 Coefficient of Variation 3.36% 0.07% 3.53% 0.07% 1.39% 

Cert Fuel Average Hot 0.034 4.847 5.102 559 0.238 

April 4, 2001 Coefficient of Variation 13.15% 0.04% 2.26% 0.24% 2.42% 

B20 Soy/Cert+A1 Average Hot 0.033 4.848 5.324 563 0.233 

April 4, 2001 Coefficient of Variation 12.34% 0.35% 0.75% 0.18% 1.08% 

Cert Fuel Average Hot 0.030 4.852 5.386 559 0.232 

April 6, 2001 Coefficient of Variation 11.31% 0.59% 4.09% 0.23% 3.68% 

B20 Soy/Cert fuel Average Hot 0.023 4.913 4.784 558 0.201 

April 10, 2001 Coefficient of Variation 17.82% 0.61% 2.25% 0.12% 2.05% 

Cert Fuel Average Hot 0.025 4.813 5.144 558 0.252 

April 10, 2001 Coefficient of Variation 12.10% 0.18% 2.51% 0.12% 0.68% 

Testing of K50 

The objective of Task 12 of this project is to test a blend of No. 1 diesel (also known as 

kerosene) and 50 volume percent soy diesel (this blend is referred to as K50). The best NOx

reduction additive identified under this project is to then be blended with K50 and tested. The 

best NOx reduction additive identified was di-tert-butyl-peroxide (DTBP). For B20 produced 

from soy diesel and certification diesel 0.93, volume percent DTBP was sufficient to reduce NOx

to the certification fuel level. For K50 we elected to employ 2.5 times as much DTBP (2.3%) 

because the fuel contains 2.5 times as much biodiesel. This is the most conservative way to 

insure that a NOx reduction occurs. As the data will show, 2.3% DTBP is more than was needed 

to achieve NOx neutrality with certification diesel. A better approach may have been to note that 

the desired percent NOx reduction was 2.55%. For B20 this could be obtained with 0.624% 

DTBP suggesting that 2.5 times this level, or 1.456% DTBP, might have been adequate for the 

K50 fuel. 

The kerosene was obtained locally. Emissions results for the kerosene without biodiesel were 

obtained for completeness. All emissions results are shown in Table 21. Kerosene produced a 

NOx level of 4.53 g/bhp-h. Testing of 50% soy/50% kerosene produced a NOx emission of 4.94 

g/bhp-h, essentially the same level observed for B20 from certification diesel and 20% soy. 
 23

Addition of 2.3% DTBP reduced NOx to 4.70 g/bhp-h. This is well below the certification fuel 

level of 4.85 g/bhp-h and suggests that between 1% and 1.5% DTBP would have been adequate. 

Fuel analysis results are reported in Table 22. Addition of 2.3% DTBP to K50 was very effective 

at increasing cetane number, causing an increase of 28 cetane units. 

Table 21. Emissions summary for testing of kerosene/soydiesel blends; results are average of 

three or more hot starts.

Fuel THC NOx CO CO2 PM 

 g/bhp-h g/bhp-h g/bhp-h g/bhp-h g/bhp-h

B20 Soy/Cert fuel Average Hot 0.037 4.941 4.616 558 0.191 

March 7, 2001 Coefficient of Variation 18.23% 0.23% 1.36% 0.06% 1.11% 

Cert Fuel Average Hot 0.034 4.852 5.091 555 0.260 

March 22, 2001 Coefficient of Variation 16.63% 0.42% 2.23% 0.14% 1.40% 

Kerosene Average Hot 0.086 4.527 4.005 554 0.199 

March 27, 2001 Coefficient of Variation 5.06% 0.27% 1.66% 0.09% 2.41% 

K50 Average Hot 0.046 4.940 3.611 556 0.115 

March 28, 2001 Coefficient of Variation 6.03% 1.06% 3.51% 0.24% 3.47% 

Cert Fuel Average Hot 0.036 4.853 5.283 560 0.260 

March 28, 2001 Coefficient of Variation 3.36% 0.07% 3.53% 0.07% 1.39% 

Cert Fuel Average Hot 0.030 4.852 5.386 559 0.232 

April 6, 2001 Coefficient of Variation 11.31% 0.59% 4.09% 0.23% 3.68% 

K50+2.3%DTBP Average Hot 0.029 4.701 3.252 556 0.084 

April 6, 2001 Coefficient of Variation 2.41% 0.69% 3.84% 0.09% 8.56% 
 24

Table 22. Fuel property testing results for kerosene and K50 fuels. 

Property Method Units No. 1 Diesel Soygold K50 K50+2.3%DTBP

Cetane Number (CN) ASTM-D613-86 42.8 47.4 44.3 72.2 

Cetane Index ASTM-D975 45.8 -- 51.2 48.7 

Kinematic Viscosity 40C ASTM-D445 mm2/s 1.3 4.066 2.2 2.2 

Iodine Number ASTM-D1959 -- 127.4 -- -- 

Cloud Point ASTM-D2500 F -61 -- 17 16 

Cloud Point ASTM-D5773 C -- -1 -- -- 

Flash Point ASTM-D93 F 130 288 144 126 

Cold Filter Plugging Point ASTM-6371 C -- -3 -- -- 

Pour Point ASTM-D97 F -- -- -- -- 

Total Sulfur by UVF ASTM-D5453 wt% -- 0.000068 -- -- 

Sulfur ASTM-D2622 wt% 0.0138 -- 0.0062 0.0071 

Ash Content ASTM-D482 wt% 0.001 -- -- -- 

Sulfated Ash ASTM-D874 wt% -- 0.003 -- -- 

Water Content ASTM-D1796 -- -- -- -- 

Specific Gravity ASTM-D4052 -- -- -- -- 

Carbon Residue ASTM-D189 wt% -- -- -- -- 

Carbon Residue ASTM-D524 wt% 0.06 0.08 0.01 0.06 

Corrosion, Copper strip ASTM-D130 -- 1A 

Water and Sediment ASTM-D2709 vol% <0.05 <0.005 <0.05 <0.05 

Acid Number ASTM-D664 mgKOH/g -- 0.03 -- -- 

Hydrocarbon Type: ASTM-D1319 

Aromatics %vol -- -- -- -- 

Olefins %vol -- -- -- -- 

Saturates %vol -- -- -- -- 

Free Glycerin wt% 0.004 

Total Glycerin 

ASTM D6584 

wt% 0.184 

Distillation ASTM-D86 

IBP F 338 -- 347 251 

10 F 365 -- 381 380 

50 F 407 -- 522 518 

90 F 471 -- 644 648 

EP F 515 -- 651 648 
 25

DISCUSSION 

Effect of Various NOx Reduction Strategies 

This study has examined a number of approaches for NOx reduction from biodiesel. These are 

compared in Table 23 for B20 (soy+cert). Blending FT diesel at very high percentages can 

produce a NOx neutral fuel. Lowering the base fuel aromatic content from 31.9 to 7.5% 

(nominally 10% aromatic fuel) was very successful at lowering NOx. If all other factors are equal 

and if the effect of aromatic content is linear, using a base fuel having 25.8% aromatics should 

provide a NOx neutral B20. The results also suggest that using kerosene as the base fuel could 

lead to a NOx neutral blend (this occurs at 40% biodiesel, assuming linearity). The cetane 

enhancers DTBP and EHN are both effective at reducing NOx from biodiesel. The antioxidant 

TBHQ is also effective, but may cause an increase in PM emissions. The idea of using 

antioxidants as NOx reduction additives is clearly something that should be explored in more 

detail. It may be that other antioxidants also reduce NOx but have no negative impact on PM 

emissions. The Bioclean Fuels A1 additive is effective at NOx reduction but causes an 

unacceptably large increase in PM. 

Table 23. Effect of various fuel additives on NOx reduction for B20 (soy+cert). 

Additive NOx, g/bhp-h % Reduction‡ Significance (p-value)

Certification Diesel 4.85 -- -- 

B20 (soy+cert) no additive 4.93 -- -- 

46% FT diesel 4.85 1.62 Predicted* 

10% Aromatic base stock 4.61 6.49 <0.001 

1% DTBP 4.75 3.65 0.030 

0.5% EHN 4.83 2.03 <0.001 

2% Short Chain FA Esters (USDA-1) 5.01 -1.62 <0.001 

0.2% TBHQ (USDA-2) 4.89 0.08+ 0.001 

2.5% A1 4.85 1.62+ 0.018 

‡

Relative to B20 (soy+cert) 

*

Predicted from model shown in Figure 2 

+

These additives also caused an increase in PM 

Use of Cetane Improvers for Biodiesel NOx Reduction 

Perhaps the most practical strategy for NOx reduction in the short term is the use of cetane 

improvers. This is because altering the base fuel properties may severely limit the marketability 

of biodiesel, and the other additives caused an increase in PM or had no effect. A recently 

obtained quotation (7) indicates that DTBP can be obtained in truckload quantities for $2.45 per 

lb. Assuming B20 has a density of 7.1 lb/gal, and DTBP has a density of 6.59lb/gal, 1 volume 

percent is 0.066 lb of DTBP. This translates into an incremental cost of $0.162 per gallon. For 

EHN the density is 8.0 lb/gal and 0.04 lb is required to make 0.5 volume percent. EHN has 

recently been quoted on the internet spot market for $1.25/lb or an incremental cost per gallon of 

$0.05. Biodiesel is currently selling at between $1 and $1.70 per gallon (8) while petroleum 

diesel sells for an average of $1.42 per gallon in 49 states and $1.55 per gallon in California (9). 
 26

California diesel fuel averages approximately 16% aromatic content (10) and, as discussed 

above, using a base fuel with less than 25.8% aromatic content should result in B20 NOx

emissions below those for certification diesel. So using a low aromatic California diesel as the 

blending diesel to lower NOx relative to certification diesel, if such a fuel was available, would 

have an incremental cost on the order of $0.13 per gallon.. FT diesel sells for $0.20 to $0.50 

more than California diesel so blending high levels of FT with biodiesel to reduce NOx may not 

be an economically viable alternative. 

Comparisons with 10% Aromatic Diesel 

For a diesel fuel to be legal for sale in California it must meet EPA’s requirements, and in 

addition it must be proven to be emissions equivalent to a 10% aromatic CARB reference diesel 

or have less than 10% aromatic content (California Code of Regulations Title 13 section 2282, 

subsection g). In this study we tested a nominally 10% aromatic fuel as a reference point for 

gauging the potential of B20 blends for possible CARB certification. Results for several B20 

blends are shown in Figure 5 and compared to emissions from the 10% aromatic fuel. All of the 

B20 blends exhibited PM emissions below those measured for the 10% aromatic diesel. 

However, B20 fuels based on certification diesel did not in any case exhibit NOx emissions at or 

below the emissions of the 10% aromatic fuel. B20 blends produced from the 10% aromatic fuel 

and including DTBP were NOx equivalent or better. Thus blending of biodiesel with a California 

compliant diesel and treating it with DTBP may be a route to a CARB certifiable B20. 

NOx, g/bhp-h

01 4 5

PM, g/bhp-h

0.00 0.20

YG+10% Aromatic (1% DTBP)

YG+10% Aromatic

Soy+10% Aromatic (1% DTBP)

Soy+10% Aromatic

YG+Cert Fuel (1% DTBP)

YG+Cert Fuel

Soy+Cert Fuel (1.5% DTBP)

Soy+Cert Fuel (1% DTBP)

Soy+Cert Fuel

10% Aromatic Fuel Emissions (95% Confidence)

Figure 5. Comparison of B20 emissions with emissions for 10% aromatic diesel. 

Comparison of Soy and YG Biodiesels 

Degree of unsaturation appears to be the key difference between soy and yellow grease (YG) 

based biodiesels from the standpoint of emissions performance (2,3). The iodine numbers of 
 27

these fuels were 127 and 79, respectively. The cetane number of the YG fuel was 

correspondingly higher. Figure 6 compares emissions for various fuels containing soy and YG 

biodiesel. For B100 fuels, the PM emissions are approximately the same, but YG (Bio3000) 

exhibited NOx emissions that were lower by nearly 0.4 g/bhp-h. Treating B100 fuels with DTBP 

was effective at reducing NOx, but not in proportion to the NOx reduction observed for B20 

blends. 

For the B20 blends a significant (about 2%) NOx increase relative to certification diesel was 

observed for soy but no significant increase was observed for YG. Treatment with 1% DTBP 

lowered NOx by about the same amount for both blends. The fact that the NOx reduction for 

DTBP is the same independent of biodiesel source, and that it decreases with increasing 

biodiesel content of the fuel may suggest that DTBP acts largely to lower the NOx produced by 

burning the petroleum diesel fuel. The fact that DTBP can reduce NOx emissions from petroleum 

diesel is well documented (11). 

NOx, g/bhp-h

01 4 5 6

PM, g/bhp-h

0.00 0.10 0.20

B20: YG+Cert (1% DTBP)

B20: YG+Cert

B20: Soy+Cert (1% DTBP)

B20: Soy+Cert

Bio3000 (5% DTBP)

Bio3000 (YG)

Soygold (5% DTBP)

Soygold

Figure 6. Comparison of emissions for various soy and yellow grease biodiesel fuels. 
 28

CONCLUSIONS 

This study has examined a number of approaches for NOx reduction from biodiesel. The 

following conclusions can be drawn: 

• The cetane improvers DTBP and EHN are effective for reducing NOx by 4% in B20 

blends. DTBP at 1.0 volume percent will add on the order of $0.16 per gallon and EHN at 

0.5 volume percent will add on the order of $0.05 per gallon to the cost of biodiesel. 

• DTBP is also effective at NOx reduction for B100 fuels but not in proportion to the NOx

reduction observed for B20 blends. This may indicate that cetane improvers act largely to 

lower the NOx produced during burning of the petroleum diesel fuel. 

• Blending with a low aromatic diesel, kerosene, or FT diesel is also effective at reducing 

NOx. 

• The antioxidant TBHQ significantly reduced NOx but also caused a small increase in PM. 

The use of antioxidants in general is worthy of further study. 

• Short chain fatty acid esters were not effective for NOx reduction. 

• Bioclean Fuels A1 additive is effective at NOx reduction but also produces a significant 

increase in PM. 

• No combination of biodiesel with certification fuel and fuel additives produced NOx

emissions levels below that observed for a 10% aromatic fuel, suggesting that CARB 

certification using a 30% aromatic base fuel is not possible. Lowering aromatic content to 

roughly 25% and addition of cetane improver would be necessary for NOx neutrality 

relative to 10% aromatic fuel. 
 29

APPENDIX A: ASTM PS121 SPECIFICATION FOR BIODIESEL FUELS 

Property ASTM 

Method 

Limits Units 

Flash Point 93 100 min °C 

Water and Sediment 2709 0.05 max Vol % 

Carbon Residue 4530 0.05 max Wt % 

or 524 0.09 max Wt% 

Sulfated Ash 874 0.02 max Wt % 

Kinematic Viscosity@40°C 445 1.9-6.0 mm2

/sec 

Sulfur 5453 0.05 max Wt % 

Cetane Number 613 40 min 

Cloud Point 2500 Report °C 

Copper Strip Corrosion 130 No. 3 max 

Acid number 664 0.80 max Mg KOH/gm 

Free Glycerine GC1

 0.02 max Wt % 

Total Glycerine GC1 0.24 max Wt % 
 30

APPENDIX B: ENGINE TORQUE MAP 

The chart below shows the engine map, acquired on certification diesel fuel, that was used to 

generate the transient cycle for all transient runs in this test program (the map is run number 

5629). 

0

200

400

600

800

1000

1200

1400

500 700 900 1100 1300 1500 1700 1900 2100

Engine Speed, rpm

Torque, ft-lb

Series1
 31

APPENDIX C: EMISSIONS DATA 

THC NOx CO 

FUEL Run # Date bhp-h g/bhp-h g/bhp-h g/bhp-h 

Cert Lot # 0KP05202 5746 1/3/01 C 21.791 0.025 5.285 6.430 Cert Lot # 0KP05202 5747 1/3/01 H 21.791 0.016 4.769 4.553 Cert Lot # 0KP05202 5748 1/3/01 H 21.819 0.023 4.759 4.646 Cert Lot # 0KP05202 5749 1/3/01 H 21.836 0.020 4.792 4.612 

Composite 0.020 4.847 4.865 

Hot Average 21.815 0.020 4.773 4.604 

Coefficient of Variation 0.10% 16.70% 0.35% 1.03% 

Shell FT w/ Paradyne 655 5751 1/4/01 C 21.599 0.018 4.491 5.196 Shell FT w/ Paradyne 655 5752 1/4/01 H 21.632 0.012 4.033 4.021 Shell FT w/ Paradyne 655 5753 1/4/01 H 21.571 0.003 4.017 3.823 Shell FT w/ Paradyne 655 5754 1/4/01 H 21.542 0.005 4.029 3.684 

Composite 0.008 4.093 4.036 

Hot Average 21.582 0.007 4.026 3.843 

Coefficient of Variation 0.21% 73.82% 0.21% 4.41% 

Cert Lot # 0KP05202 5755 1/5/01 H 21.814 0.011 4.581 5.077 Cert Lot # 0KP05202 5756 1/5/01 H 21.767 0.018 4.635 4.762 Cert Lot # 0KP05202 5757 1/5/01 H 21.816 0.018 4.651 5.043 

Hot Average 1/5/01 21.799 0.015 4.622 4.961 

Coefficient of Variation 0.13% 25.98% 0.79% 3.49% 

80%FT/20%Soygold 5758 1/5/01 H 21.546 0.010 4.268 3.751 80%FT/20%Soygold 5759 1/5/01 H 21.492 0.001 4.238 3.557 80%FT/20%Soygold 5760 1/5/01 H 21.483 0.004 4.239 3.515 

Hot Average 21.507 0.005 4.249 3.608 

Coefficient of Variation 0.16% 83.47% 0.40% 3.49% 

Cert Lot # 0KP05202 5761 1/8/01 H 21.752 0.018 4.682 5.208 Cert Lot # 0KP05202 5762 1/8/01 H 21.791 0.025 4.696 4.974 

Hot Average 1/8/01 21.771 0.021 4.689 5.091 

Coefficient of Variation 0.13% 21.63% 0.21% 3.25% 

20%FT/80%Soygold 5763 1/8/01 H 21.419 0.006 5.069 3.089 20%FT/80%Soygold 5764 1/8/01 H 21.424 0.007 5.043 2.925 20%FT/80%Soygold 5765 1/8/01 H 21.439 0.006 5.033 2.943 

Hot Average 21.427 0.006 5.048 2.986 

Coefficient of Variation 0.05% 10.17% 0.37% 3.02% 

Cert Lot # 0KP05202 5766 1/9/01 H 21.758 0.014 4.695 5.135 Cert Lot # 0KP05202 5767 1/9/01 H 21.797 0.020 4.715 5.211 

Hot Average 1/9/01 21.778 0.017 4.705 5.173 

Coefficient of Variation 0.13% 21.35% 0.30% 1.03% 
 32

THC NOx CO 

FUEL Run # Date bhp-h g/bhp-h g/bhp-h g/bhp-h 

1% SoyGold in FT 5768 1/9/01 H 21.475 0.004 4.045 3.951 1% SoyGold in FT 5769 1/9/01 H 21.464 0.000 4.024 3.990 1% SoyGold in FT 5770 1/9/01 H 21.500 0.007 4.037 3.803 

Hot Average 21.480 0.004 4.035 3.915 

Coefficient of Variation 0.09% 96.75% 0.27% 2.52% 

Cert Lot # 0KP05202 5772 1/9/01 H 21.756 0.014 4.627 5.141 Cert Lot # 0KP05202 5773 1/9/01 H 21.695 0.017 4.643 4.939 

Hot Average 21.725 0.015 4.635 5.040 

Coefficient of Variation 0.20% 13.99% 0.24% 2.84% 

SoyGold 5774 1/10/01 C 21.374 0.024 5.946 4.245 SoyGold 5775 1/10/01 H 21.448 0.011 5.367 3.047 SoyGold 5776 1/10/01 H 21.391 0.012 5.353 2.899 SoyGold 5777 1/10/01 H 21.409 0.013 5.378 2.973 

Composite 0.014 5.449 3.155 

Hot Average 21.416 0.012 5.366 2.973 

Coefficient of Variation 0.14% 10.82% 0.23% 2.48% 

Cert Lot # 0KP05202 5778 1/10/01 H 21.718 0.026 4.804 5.248 Cert Lot # 0KP05202 5779 1/10/01 H 21.674 0.018 4.785 4.809 

Hot Average 21.696 0.022 4.794 5.029 

Coefficient of Variation 0.14% 27.11% 0.28% 6.17% 

Bio3000 5780 1/11/01 C 21.466 0.020 5.570 4.390 Bio3000 5781 1/11/01 H 21.426 0.000 4.938 3.047 Bio3000 5785 1/11/01 H 21.395 0.004 5.007 3.289 Bio3000 5786 1/11/01 H 21.393 0.006 4.971 2.980 Bio3000 5787 1/11/01 H 21.394 0.007 5.008 3.106 

Composite 0.006 5.065 3.289 

Hot Average 21.402 0.004 4.981 3.105 

Coefficient of Variation 0.07% 70.98% 0.67% 4.28% 

Cert Lot # 0KP05202 5788 1/12/01 H 21.710 0.019 4.742 5.022 Cert Lot # 0KP05202 5789 1/12/01 H 21.747 0.028 4.760 5.113 Cert Lot # 0KP05202 5790 1/12/01 H 21.723 0.025 4.760 4.982 

Hot Average 1/12/01 21.727 0.024 4.754 5.039 

Coefficient of Variation 0.09% 19.75% 0.22% 1.32% 

10% Aro Lot#0LP10A01 5793 1/12/01 H 21.630 0.035 4.474 5.155 10% Aro Lot#0LP10A01 5794 1/12/01 H 21.624 0.021 4.473 4.859 10% Aro Lot#0LP10A01 5795 1/12/01 H 21.605 0.029 4.486 4.924 

Hot Average 21.620 0.029 4.478 4.980 

Coefficient of Variation 0.06% 24.05% 0.17% 3.13% 
 33

THC NOx CO 

FUEL Run # Date bhp-h g/bhp-h g/bhp-h g/bhp-h 

Cert Lot # 0KP05202 5797 1/15/01 H 21.799 0.013 4.728 5.136 Cert Lot # 0KP05202 5798 1/15/01 H 21.814 0.020 4.740 4.962 

Hot Average 1/15/01 21.806 0.016 4.734 5.049 

Coefficient of Variation 0.05% 29.96% 0.18% 2.43% 

20% SoyGold in CERT Lot# 0KP05202 5799 1/15/01 H 21.744 0.019 4.899 4.759 20% SoyGold in CERT Lot# 0KP05202 5800 1/15/01 H 21.730 0.017 4.900 4.497 20% SoyGold in CERT Lot# 0KP05202 5802 1/15/01 H 21.754 0.019 4.928 4.766 

Hot Average 21.743 0.018 4.909 4.674 

Coefficient of Variation 0.05% 6.95% 0.33% 3.28% 

20% SoyGold in CERT Lot# 0KP05202 5807 1/17/01 H 21.730 0.002 4.919 4.862 20% SoyGold in CERT Lot# 0KP05202 5808 1/17/01 H 21.710 0.005 4.915 4.593 20% SoyGold in CERT Lot# 0KP05202 5809 1/17/01 H 21.734 0.012 4.915 4.583 

Hot Average 21.725 0.007 4.916 4.679 

Coefficient of Variation 0.06% 76.55% 0.05% 3.38% 

20% SoyGold in CERT Lot# 0KP05202 + 0.5%DTBP 5810 1/18/01 H 21.737 0.008 4.781 4.548 20% SoyGold in CERT Lot# 0KP05202 + 0.5%DTBP 5811 1/18/01 H 21.747 0.005 4.790 4.279 20% SoyGold in CERT Lot# 0KP05202 + 0.5%DTBP 5814 1/18/01 H 21.740 0.001 4.805 4.416 

Hot Average 21.741 0.005 4.792 4.414 

Coefficient of Variation 0.02% 74.64% 0.25% 3.05% 

Cert Lot # 0KP05202 5815 1/19/01 H 21.820 0.012 4.802 5.036 Cert Lot # 0KP05202 5816 1/19/01 H 21.828 0.008 4.748 5.067 Cert Lot # 0KP05202 5817 1/19/01 H 21.808 0.016 4.772 4.914 

Hot Average 1/19/01 21.819 0.012 4.774 5.005 

Coefficient of Variation 0.05% 32.09% 0.57% 1.62% 

20% SoyGold in CERT Lot# 0KP05202 + 1.0%DTBP 5818 1/19/01 H 21.746 0.019 4.758 4.429 20% SoyGold in CERT Lot# 0KP05202 + 1.0%DTBP 5820 1/19/01 H 21.778 0.015 4.746 4.485 20% SoyGold in CERT Lot# 0KP05202 + 1.0%DTBP 5821 1/19/01 H 21.763 0.016 4.760 4.396 

Hot Average 21.763 0.016 4.754 4.436 

Coefficient of Variation 0.07% 11.32% 0.15% 1.01% 

20% SoyGold in CERT Lot# 0KP05202 + 1.5%DTBP 5718 11/16/00 H 21.681 0.016 4.615 4.303 20% SoyGold in CERT Lot# 0KP05202 + 1.5%DTBP 5719 11/16/00 H 21.677 0.003 4.607 4.155 20% SoyGold in CERT Lot# 0KP05202 + 1.5%DTBP 5720 11/16/00 H 21.676 0.007 4.612 4.194 

Hot Average 21.678 0.008 4.612 4.218 

Coefficient of Variation 0.01% 83.58% 0.09% 1.82% 

THC NOx CO 

FUEL Run # Date bhp-h g/bhp-h g/bhp-h g/bhp-h 

20% Bio-3000 in CERT Lot# 0KP05202 5822 1/22/01 H 21.772 0.007 4.770 4.783 20% Bio-3000 in CERT Lot# 0KP05202 5823 1/22/01 H 21.802 0.012 4.784 4.606 20% Bio-3000 in CERT Lot# 0KP05202 5824 1/22/01 H 21.762 0.009 4.786 4.584 

Hot Average 21.778 0.009 4.780 4.658 

Coefficient of Variation 0.10% 22.83% 0.19% 2.34% 
 34

THC NOx CO 

FUEL Run # Date bhp-h g/bhp-h g/bhp-h g/bhp-h 

Cert Lot # 0KP05202 5825 1/22/01 H 21.790 0.017 4.759 5.137 Cert Lot # 0KP05202 5826 1/22/01 H 21.815 0.018 4.785 4.908 Cert Lot # 0KP05202 5827 1/22/01 H 21.812 0.020 4.805 4.863 

Hot Average 1/22/01 21.806 0.018 4.783 4.969 

Coefficient of Variation 0.06% 7.15% 0.48% 2.96% 

20% Bio-3000 in CERT Lot# 0KP05202 + 1.0%DTBP 5828 1/23/01 H 21.775 0.012 4.630 4.701 20% Bio-3000 in CERT Lot# 0KP05202 + 1.0%DTBP 5829 1/23/01 H 21.796 0.001 4.637 4.470 20% Bio-3000 in CERT Lot# 0KP05202 + 1.0%DTBP 5830 1/23/01 H 21.774 0.013 4.643 4.324 

Hot Average 21.782 0.009 4.637 4.498 

Coefficient of Variation 0.06% 75.98% 0.14% 4.23% 

20% SoyGold in 10%AROMATIC lot # 0LP10A01 5831 1/23/01 H 21.719 0.019 4.610 4.491 20% SoyGold in 10%AROMATIC lot # 0LP10A01 5832 1/23/01 H 21.680 0.025 4.602 4.366 20% SoyGold in 10%AROMATIC lot # 0LP10A01 5833 1/23/01 H 21.695 0.023 4.607 4.143 

Hot Average 21.698 0.022 4.606 4.333 

Coefficient of Variation 0.09% 13.68% 0.09% 4.07% 

Cert Lot # 0KP05202 5834 1/24/01 H 21.806 0.016 4.788 5.171 Cert Lot # 0KP05202 5835 1/24/01 H 21.834 0.022 4.809 4.804 Cert Lot # 0KP05202 5836 1/24/01 H 21.811 0.016 4.825 4.809 

Hot Average 1/24/01 21.817 0.018 4.807 4.928 

Coefficient of Variation 0.07% 18.72% 0.38% 4.26% 

20% Bio-3000 in 10%AROMATIC lot# 0LP10A01 5837 1/24/01 H 21.723 0.014 4.601 4.508 20% Bio-3000 in 10%AROMATIC lot# 0LP10A01 5838 1/24/01 H 21.732 0.019 4.579 4.399 20% Bio-3000 in 10%AROMATIC lot# 0LP10A01 5839 1/24/01 H 21.726 0.019 4.578 4.374 

Hot Average 21.727 0.017 4.586 4.427 

Coefficient of Variation 0.02% 17.21% 0.29% 1.61% 

20% Bio-3000 In 10%Aromatic Lot# 0LP10A01+1.0% DTBP 5840 1/25/01 H 21.652 0.015 4.427 4.659 20% Bio-3000 In 10%Aromatic Lot# 0LP10A01+1.0% DTBP 5841 1/25/01 H 21.651 0.019 4.406 4.590 20% Bio-3000 In 10%Aromatic Lot# 0LP10A01+1.0% DTBP 5842 1/25/01 H 21.636 0.014 4.410 4.521 

Hot Average 21.646 0.016 4.414 4.590 

Coefficient of Variation 0.04% 17.22% 0.24% 1.50% 

20% SoyGold in 10%Aromatic lot # 0LP10A01+1.0 %DTBP 5843 1/25/01 H 21.592 0.016 4.480 4.528 20% SoyGold in 10%Aromatic lot # 0LP10A01+1.0 %DTBP 5844 1/25/01 H 21.653 0.012 4.465 4.465 20% SoyGold in 10%Aromatic lot # 0LP10A01+1.0 %DTBP 5845 1/25/01 H 21.621 0.019 4.463 4.341 

21.622 0.016 4.469 4.445 0.14% 24.00% 0.20% 2.13% 

Cert Lot # 0KP05202 5846 1/31/01 C 21.734 0.003 4.744 5.017 Cert Lot # 0KP05202 5847 1/31/01 H 21.766 0.010 4.707 4.766 Cert Lot # 0KP05202 5848 1/31/01 H 21.807 0.012 4.704 4.793 Cert Lot # 0KP05202 5849 1/31/01 H 21.808 0.013 4.758 4.811 

Hot Average 1/31/01 21.793 0.011 4.723 4.790 

Coefficient of Variation 0.11% 12.47% 0.64% 0.48% 
 35

THC NOx CO 

FUEL Run # Date bhp-h g/bhp-h g/bhp-h g/bhp-h 

Cert Lot # 0KP05202 5879 2/15/01 C 21.810 0.018 5.015 5.850 Cert Lot # 0KP05202 5880 2/15/01 H 21.842 0.016 4.797 5.382 Cert Lot # 0KP05202 5881 2/15/01 H 21.827 0.020 4.832 5.584 

Hot Average 21.826 0.018 4.881 5.605 

Coefficient of Variation 0.07% 10.71% 2.39% 4.19% 

Cert Lot # 0KP05202 5883 2/16/01 H 21.842 0.021 4.871 5.039 Cert Lot # 0KP05202 5884 2/16/01 H 21.871 0.018 4.902 5.144 Cert Lot # 0KP05202 5887 2/16/01 H 21.898 0.017 4.872 4.984 

Hot Average 21.870 0.018 4.882 5.056 

Coefficient of Variation 0.13% 10.82% 0.36% 1.61% 

Cert Lot # 0KP05202 5923 3/7/01 H 21.933 0.039 4.869 5.283 Cert Lot # 0KP05202 5924 3/7/01 H 21.928 0.048 4.818 4.906 Cert Lot # 0KP05202 5925 3/7/01 H 21.927 0.036 4.802 5.129 

Hot Average 21.929 0.041 4.830 5.106 

Coefficient of Variation 0.02% 15.02% 0.73% 3.71% 

20% SoyGold in CERT lot:OKPO5202 5926 3/7/01 H 21.815 0.029 4.947 4.687 20% SoyGold in CERT lot:OKPO5202 5927 3/7/01 H 21.839 0.040 4.949 4.589 20% SoyGold in CERT lot:OKPO5202 5928 3/7/01 H 21.865 0.042 4.928 4.571 

Hot Average 21.840 0.037 4.941 4.616 

Coefficient of Variation 0.11% 18.23% 0.23% 1.36% 

Cert Lot # 0KP05202 5930 3/12/01 H 21.885 0.054 4.831 5.107 Cert Lot # 0KP05202 5931 3/12/01 H 21.911 0.051 4.844 5.047 Cert Lot # 0KP05202 5932 3/12/01 H 21.902 0.053 4.846 5.186 

Hot Average 21.900 0.053 4.841 5.113 

Coefficient of Variation 0.06% 2.76% 0.17% 1.37% 

 20:1 SoyGold + DTBP 5933 3/12/01 H 21.642 0.027 5.208 2.545  20:1 SoyGold + DTBP 5934 3/12/01 H 21.615 0.024 5.148 2.477  20:1 SoyGold + DTBP 5935 3/12/01 H 21.630 0.028 5.194 2.387 

Hot Average 21.629 0.027 5.184 2.470 

Coefficient of Variation 0.06% 7.73% 0.61% 3.21% 

20% SoyGold + 0.5% EHN in Cert lot # OKPO5202 5936 3/13/01 H 21.841 0.017 4.855 4.672 20% SoyGold + 0.5% EHN in Cert lot # OKPO5202 5937 3/13/01 H 21.831 0.028 4.827 4.549 20% SoyGold + 0.5% EHN in Cert lot # OKPO5202 5938 3/13/01 H 21.810 0.028 4.820 4.367 

Hot Average 21.827 0.024 4.834 4.529 

Coefficient of Variation 0.07% 26.99% 0.39% 3.39% 

20% SoyGold + 1.0% EHN in Cert lot # OKPO5202 5939 3/13/01 H 21.792 0.033 4.834 4.438 20% SoyGold + 1.0% EHN in Cert lot # OKPO5202 5940 3/13/01 H 21.868 0.029 4.794 4.498 20% SoyGold + 1.0% EHN in Cert lot # OKPO5202 5941 3/13/01 H 21.843 0.038 4.783 4.358 

Hot Average 21.834 0.033 4.804 4.431 

Coefficient of Variation 0.18% 13.16% 0.56% 1.58% 
 36

THC NOx CO 

FUEL Run # Date bhp-h g/bhp-h g/bhp-h g/bhp-h 

 20:1 Bio-3000 + DTBP 5942 3/14/01 H 21.430 0.018 4.901 3.033  20:1 Bio-3000 + DTBP 5943 3/14/01 H 21.444 0.015 4.863 2.773  20:1 Bio-3000 + DTBP 5944 3/14/01 H 21.451 0.014 4.879 2.776 

Hot Average 21.442 0.016 4.881 2.861 

Coefficient of Variation 0.05% 12.43% 0.39% 5.22% 

Cert Lot # 0KP05202 5945 3/14/01 H 21.834 0.032 4.776 5.292 Cert Lot # 0KP05202 5946 3/14/01 H 21.855 0.028 4.795 5.082 Cert Lot # 0KP05202 5947 3/14/01 H 21.864 0.028 4.828 5.196 

Hot Average 21.851 0.029 4.800 5.190 

Coefficient of Variation 0.07% 6.83% 0.55% 2.03% 

Cert Lot # 0KP05202 5952 3/22/01 C 21.902 0.032 4.866 5.388 Cert Lot # 0KP05202 5953 3/22/01 H 21.918 0.041 4.859 5.072 Cert Lot # 0KP05202 5954 3/22/01 H 21.884 0.036 4.855 5.104 Cert Lot # 0KP05202 5955 3/22/01 H 21.881 0.037 4.843 5.245 

Hot Average 21.894 0.038 4.852 5.140 

Coefficient of Variation 0.09% 7.25% 0.17% 1.79% 

40:1 B-20Soy in 10%Aromatic / A-1 5965 3/26/01 H 21.731 0.037 4.558 5.051 40:1 B-20Soy in 10%Aromatic / A-1 5966 3/26/01 H 21.748 0.042 4.568 4.903 40:1 B-20Soy in 10%Aromatic / A-1 5967 3/26/01 H 21.750 0.042 4.564 4.893 

Hot Average 21.743 0.040 4.563 4.949 

Coefficient of Variation 0.05% 6.54% 0.10% 1.79% 

Kerosene 5968 3/27/01 H 21.486 0.113 5.140 5.837 Kerosene 5969 3/27/01 H 21.420 0.082 4.521 4.069 Kerosene 5970 3/27/01 H 21.421 0.085 4.520 4.011 Kerosene 5971 3/27/01 H 21.401 0.091 4.542 3.937 

Hot Average 21.414 0.086 4.527 4.005 

Coefficient of Variation 0.05% 5.06% 0.27% 1.66% 

K50 (50% Kerosene + 50% SoyGold) 5972 3/28/01 H 21.445 0.044 5.000 3.749 K50 (50% Kerosene + 50% SoyGold) 5973 3/28/01 H 21.483 0.045 4.915 3.500 K50 (50% Kerosene + 50% SoyGold) 5974 3/28/01 H 21.464 0.049 4.904 3.585 

Hot Average 21.464 0.046 4.940 3.611 

Coefficient of Variation 0.09% 6.03% 1.06% 3.51% 

Cert Lot # 0KP05202 5976 3/28/01 H 21.775 0.035 4.850 5.151 Cert Lot # 0KP05202 5977 3/28/01 H 21.806 0.037 4.855 5.415 

Hot Average 21.791 0.036 4.853 5.283 

Coefficient of Variation 0.10% 3.36% 0.07% 3.53% 

18% SoyGold in CERT lot: 0KP05202 + 2% USDA-1 5978 3/28/01 H 21.719 0.032 5.088 4.844 18% SoyGold in CERT lot: 0KP05202 + 2% USDA-1 5979 3/28/01 H 21.727 0.030 4.979 4.641 18% SoyGold in CERT lot: 0KP05202 + 2% USDA-1 5980 3/28/01 H 21.743 0.028 4.970 4.674 

Hot Average 21.730 0.030 5.012 4.719 

Coefficient of Variation 0.06% 8.23% 1.31% 2.30% 
 37

THC NOx CO 

FUEL Run # Date bhp-h g/bhp-h g/bhp-h g/bhp-h 

Cert Lot # 0KP05202 5989 4/4/01 H 21.839 0.030 4.847 5.235 Cert Lot # 0KP05202 5990 4/4/01 H 21.882 0.033 4.846 5.030 Cert Lot # 0KP05202 5991 4/4/01 H 21.863 0.039 4.850 5.042 

Hot Average 21.861 0.034 4.847 5.102 

Coefficient of Variation 0.10% 13.15% 0.04% 2.26% 

40:1 B-20Soy in Cert / A-1 5992 4/4/01 H 21.761 0.032 4.863 5.284 40:1 B-20Soy in Cert / A-1 5993 4/4/01 H 21.765 0.029 4.830 5.364 40:1 B-20Soy in Cert / A-1 5994 4/4/01 H 21.799 0.037 4.852 5.325 

Hot Average 21.775 0.033 4.848 5.324 

Coefficient of Variation 0.10% 12.34% 0.35% 0.75% 

20% SoyGold in Cert lot OKPO5202 + 0.2%wt USDA-2 5995 4/5/01 H 21.794 0.024 4.904 5.044 20% SoyGold in Cert lot OKPO5202 + 0.2%wt USDA-2 5996 4/5/01 H 21.791 0.030 4.879 4.755 20% SoyGold in Cert lot OKPO5202 + 0.2%wt USDA-2 5997 4/5/01 H 21.782 0.029 4.887 4.836 20% SoyGold in Cert lot OKPO5202 + 0.2%wt USDA-2 5998 4/5/01 H 21.791 0.029 4.904 4.750 

Hot Average 21.790 0.028 4.894 4.846 

Coefficient of Variation 0.02% 9.74% 0.26% 2.84% 

Cert Lot # 0KP05202 6000 4/6/01 H 21.825 0.029 4.880 5.473 Cert Lot # 0KP05202 6001 4/6/01 H 21.840 0.033 4.822 5.135 Cert Lot # 0KP05202 6002 4/6/01 H 21.827 0.027 4.855 5.550 

Hot Average 21.831 0.030 4.852 5.386 

Coefficient of Variation 0.04% 11.31% 0.59% 4.09% 

K50 (50% Kerosene + 50% SoyGold) + 2.3% vol. DTBP 6003 4/6/01 H 21.425 0.029 4.739 3.396 K50 (50% Kerosene + 50% SoyGold) + 2.3% vol. DTBP 6004 4/6/01 H 21.432 0.030 4.688 3.185 K50 (50% Kerosene + 50% SoyGold) + 2.3% vol. DTBP 6005 4/6/01 H 21.442 0.029 4.678 3.175 

Hot Average 21.433 0.029 4.701 3.252 

Coefficient of Variation 0.04% 2.41% 0.69% 3.84% 

Cert Lot # 0KP05202 6010 4/10/01 H 21.866 0.024 4.820 5.289 Cert Lot # 0KP05202 6011 4/10/01 H 21.849 0.023 4.816 5.044 Cert Lot # 0KP05202 6012 4/10/01 H 21.840 0.029 4.803 5.099 

Hot Average 21.852 0.025 4.813 5.144 

Coefficient of Variation 0.06% 12.10% 0.18% 2.51% 

20% SoyGold in Cert lot OKPO5202 6013 4/10/01 H 21.810 0.018 4.947 4.660 20% SoyGold in Cert lot OKPO5202 6014 4/10/01 H 21.786 0.026 4.895 4.843 20% SoyGold in Cert lot OKPO5202 6015 4/10/01 H 21.812 0.025 4.896 4.850 

Hot Average 21.803 0.023 4.913 4.784 

Coefficient of Variation 0.06% 17.82% 0.61% 2.25% 

20% SoyGold in Cert lot OKPO5202+0.5%EHN 6025 4/19/01 H 21.832 0.019 4.805 4.781 20% SoyGold in Cert lot OKPO5202+0.5%EHN 6026 4/19/01 H 21.816 0.017 4.735 4.615 20% SoyGold in Cert lot OKPO5202+0.5%EHN 6027 4/19/01 H 21.811 0.020 4.759 4.591 

Hot Average 21.819 0.018 4.766 4.662 

Coefficient of Variation 0.05% 9.62% 0.74% 2.22% 
 38

THC NOx CO 

FUEL Run # Date bhp-h g/bhp-h g/bhp-h g/bhp-h 

20% SoyGold in Cert lot OKPO5202 6028 4/19/01 H 21.833 0.018 4.887 4.824 20% SoyGold in Cert lot OKPO5202 6029 4/19/01 H 21.772 0.015 4.875 4.758 20% SoyGold in Cert lot OKPO5202 6030 4/19/01 H 21.782 0.019 4.870 4.560 

Hot Average 21.796 0.018 4.877 4.714 

Coefficient of Variation 0.15% 11.28% 0.18% 2.91% 
 39

APPENDIX D: REFERENCES 

 

1. Graboski, M.S., R.L. McCormick “Combustion of Fat and Vegetable Oil Derived Fuels in Diesel 

Engines” Progress in Energy and Combustion Science, 24 125 (1998). 

2. Graboski, M.S., McCormick, R.L., Alleman, T.L., Herring, A.M. “Effect of Biodiesel Composition 

on NOx and PM Emissions from a DDC Series 60 Engine” Final Report to National Renewable 

Energy Laboratory, Contract No. ACG-8-17106-02. June 7, 2000. 

3. McCormick, R.L., Graboski, M.S., Alleman, T.L., Herring, A.M. “Impact of Biodiesel Source 

Material and Chemical Structure on Emissions of Criteria Pollutants from a Heavy-Duty Engine” 

Environ. Sci. Technol. 35 1742-1747 (2001). 

4. Norton, P., Vertin, K., Bailey, B., Clark, N. N., Lyons, D.W., Goguen, S., Eberhart, J. “Emissions 

from Trucks using Fischer-Tropsch Diesel Fuel” SAE Technical Paper No. 982526 (1998). 

5. Sharp, C.A. “Transient Emissions Testing of Biodiesel in a DDC 6V-92TA Engine” Final Report to 

NBB, SWRI, Oct. 1994. 

6. Sharp, C.A. “Transient Emissions Testing of Biodiesel and Other Additives in a DDC Series 60 

Engine” Final Report to NBB, SWRI, Dec. 1994.

7. NORAC Company, accessed by telephone 626-334-2908, April 24, 2001. 

8. Tyson, K. S. private communication, April 24, 2001. 

9. Energy Information Agency, U.S.D.O.E. at www.eia.doe.gov accessed April 24, 2001. 

10. Appendix IV-Fuels Report; California Air Resources Board: Sacramento, CA, 2000. 

http://www.arb.ca.gov/diesel/documents/rrpapp4.pdf. 

11. Schwab, S.D., Guinther, G.H., Henly, T.J., Miller, K.T. “The Effects of 2-Ethylhexyl Nitrate and 

Di-tertiary-butyl Peroxide on the Exhaust Emissions from a Heavy-Duty Diesel Engine” SAE 

Technical Paper No. 1999-01-1478 (1999). 
REPORT DOCUMENTATION PAGE Form Approved 

 OMB NO. 0704-0188 

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 this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson 

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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE

February 2003 

3. REPORT TYPE AND DATES COVERED 

Subcontract Report 

4. TITLE AND SUBTITLE

NOx Solutions for Biodiesel: Final Report; Report 6 in a Series of 6 

6. AUTHOR(S) 

R.L. McCormick, J.R. Alvarez, and M.S. Graboski 

5. FUNDING NUMBERS

XCO-0-30088-01 

BBA3.5210 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 

Colorado Institute for Fuels and Engine Research 

Colorado School of Mines 

Golden, Colorado 

8. PERFORMING ORGANIZATION 

REPORT NUMBER 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Renewable Energy Laboratory 

1617 Cole Blvd. 

Golden, CO 80401-3393

10. SPONSORING/MONITORING 

AGENCY REPORT NUMBER

NREL/SR-510-31465 

11. SUPPLEMENTARY NOTES

NREL Technical Monitor: K.S. Tyson 

12a. DISTRIBUTION/AVAILABILITY STATEMENT

National Technical Information Service 

U.S. Department of Commerce 

5285 Port Royal Road 

 Springfield, VA 22161

12b. DISTRIBUTION CODE

 

13. ABSTRACT (Maximum 200 words)

A number of studies have shown substantial particulate matter (PM) reductions for biodiesel, but also a significant increase in

nitrogen oxides (NOx) emissions. This study examines a number of approaches for NOx reduction from biodiesel. 

15. NUMBER OF PAGES

14. SUBJECT TERMS 

Biodiesel; heavy duty engine emissions; nitrogen oxides (NOx); particulate matter (PM) 16. PRICE CODE

17. SECURITY CLASSIFICATION 

OF REPORT

Unclassified 

18. SECURITY CLASSIFICATION 

OF THIS PAGE

Unclassified

19. SECURITY CLASSIFICATION 

OF ABSTRACT

Unclassified

20. LIMITATION OF ABSTRACT

UL 

 NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89) 

Prescribed by ANSI Std. Z39-18 

298-102