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

Office of Energy Efficiency & Renewable Energy 

National Renewable Energy Laboratory 

Innovation for Our Energy Future 

Technical Report Survey of the Quality and Stability NREL/TP-540-38836 of Biodiesel and Biodiesel Blends October 2005 

in the United States in 2004 

R.L. McCormick, T.L. Alleman, M. Ratcliff, and 

L. Moens 

National Renewable Energy Laboratory 

R. Lawrence 

Magellan Midstream Partners, LLC. 

NREL is operated by Midwest Research Institute ● Battelle Contract No. DE-AC36-99-GO10337 
Survey of the Quality and Stability 

of Biodiesel and Biodiesel Blends 

in the United States in 2004 

R.L. McCormick, T.L. Alleman, M. Ratcliff, and 

L. Moens 

National Renewable Energy Laboratory 

R. Lawrence 

Magellan Midstream Partners, LLC. 

Prepared under Task No. FC05.9400 

Technical Report 

NREL/TP-540-38836 

October 2005 

National Renewable Energy Laboratory 

1617 Cole Boulevard, Golden, Colorado 80401-3393 

303-275-3000 • www.nrel.gov 

Operated for the U.S. Department of Energy 

Office of Energy Efficiency and Renewable Energy 

by Midwest Research Institute • Battelle 

Contract No. DE-AC36-99-GO10337
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iii

Table of Contents 

List of Tables ...................................................................................................................... v 

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

Acronyms and Abbreviations ............................................................................................ vi 

Executive Summary............................................................................................................ 1 

Introduction......................................................................................................................... 3 

Survey of B100 Quality and Stability................................................................................. 4 

Phone Survey Results ..................................................................................................... 5 

Initial Survey............................................................................................................... 5 

Follow-up Phone Survey............................................................................................. 5 

D6751 Testing Results.................................................................................................... 6 

Flash point................................................................................................................... 8

Water and sediment..................................................................................................... 8 

Kinematic viscosity..................................................................................................... 8 

Sulfated ash................................................................................................................. 8 

Sulfur........................................................................................................................... 8 

Copper strip corrosion................................................................................................. 8 

Cetane number ............................................................................................................ 9 

Cloud point.................................................................................................................. 9 

Carbon residue ............................................................................................................ 9 

Acid number................................................................................................................ 9 

Free and total glycerin ................................................................................................ 9 

Phosphorus.................................................................................................................. 9 

Distillation temperature (T90) .................................................................................. 10 

Results of Additional Tests........................................................................................... 10 

Metals........................................................................................................................ 10 

Density ...................................................................................................................... 11

Fatty Acid Speciation................................................................................................ 11 

Testing of B100 Stability.............................................................................................. 12 

Methods..................................................................................................................... 12 

Oxidation Stability Results ....................................................................................... 13 

Oxidation Stability Discussion ................................................................................. 16 

Thermal Stability Results.......................................................................................... 21 

Thermal Stability Discussion.................................................................................... 22 

B100 Summary and Discussion.................................................................................... 24 

B20 Fuel Quality Survey .................................................................................................. 27 

Methods......................................................................................................................... 27 

Results........................................................................................................................... 27 

Biodiesel Content...................................................................................................... 28 

Acid Number............................................................................................................. 29 

Cloud Point ............................................................................................................... 29 

Distillation................................................................................................................. 29

Peroxide Value.......................................................................................................... 30 

Interfacial Tension .................................................................................................... 31 
iv

GM Water Extraction Test........................................................................................ 33 

Oxidation Stability by Rancimat............................................................................... 34 

B20 Summary and Discussion...................................................................................... 36 

Conclusions and Recommendations ................................................................................. 38 

Appendix A: Mono, Di, and Tri-Glyceride Content of B100 Samples ........................... 39 

Appendix B: Results of B100 FAME Analysis ............................................................... 41 

Appendix C: Procedure for Biodiesel Testing Using DPPH Redox Indicator ................ 43 

Appendix D: Additional Modifications to the D2274 Test Method................................ 44 

Appendix E: Detailed Results for B20 Survey ................................................................ 48 

Appendix F: B20 Rancimat Results................................................................................. 51 

References......................................................................................................................... 52 
v

List of Tables 

Table 1 Detailed Requirements for S15 Biodiesel Taken from ASTM D6751-03a.......... 4 

Table 2. Results of Initial Phone Survey ............................................................................ 5 

Table 3. Results of B100 Analysis...................................................................................... 7 

Table 4. Results of Additional Analyses Performed on B100 Samples ........................... 11 

Table 5. Identification of Outliers Via Grubb’s Test........................................................ 26 

Table 6. Tests Conducted for B20 Samples...................................................................... 27 

Table 7. Mono, Di, and Tri-Glyceride Content of B100 Samples.................................... 40 

Table 8. Results of FAME Analysis by GC-MS for B100 Samples................................. 42 

Table 9. D2274 Data with the Control Pad Modification................................................ 45 

Table 10. Rancimat Induction Time, Hours...................................................................... 51 

List of Figures 

Figure 1. Results of analysis of selected B100 samples for FAME content..................... 12 

Figure 2. Rancimat (EN14112) induction time for the B100 quality survey samples...... 14 

Figure 3. Frequency distribution for B100 Rancimat induction times ............................. 15 

Figure 4. ASTM D2274 results for the B100 quality survey samples.............................. 15 

Figure 5. Frequency distribution for D2274 results, B100 ............................................... 16 

Figure 6. Comparison of results for D2274 and Rancimat oxidation stability tests......... 17 

Figure 7. Relationship between relative antioxidant content and D2274 insolubles for 

different groups of biodiesel samples ............................................................................... 18 

Figure 8. Relationship between relative antioxidant content and Rancimat induction time 

for different groups of biodiesel samples.......................................................................... 20 

Figure 9. Relationship between oxidizability and Rancimat induction time for different 

groups of biodiesel samples.............................................................................................. 21 

Figure 10. D6468 results for B100 quality survey samples.............................................. 23 

Figure 11. Frequency distribution for B100 Rancimat induction times ........................... 23 

Figure 12. D5468 gravimetric and reflectance results for several diesel and B100 samples 

[10].................................................................................................................................... 24 

Figure 13. Percent biodiesel content for B20 quality survey samples.............................. 28 

Figure 14. Acid number (WLS-102) of B20 samples as a function of percent biodiesel. 29 

Figure 15. Cloud point (ASTM D2500) as a function of biodiesel content for B20 survey 

samples.............................................................................................................................. 30 

Figure 16. Distillation results (ASTM D86) for B20 quality survey samples.................. 30 

Figure 17. Peroxide value (or number) determined by ASTM D3703 for quality survey 

samples.............................................................................................................................. 31 

Figure 18. Results of water interfacial tension measurements by ASTM D971 for B20 

survey samples.................................................................................................................. 32 

Figure 19. Conductivity results from the GM water extraction test as a function of percent 

biodiesel (top) and peroxide content (bottom).................................................................. 34 

Figure 20. Comparison of B20 Rancimat oxidation stability test results from SwRI and 

Bosch................................................................................................................................. 35 

Figure 21. Frequency distribution for B20 Rancimat stability test results (SwRI data)... 36 

Figure 22. D2274 analysis ................................................................................................ 46 
vi

Acronyms and Abbreviations 

ASTM American Society for Testing and Materials 

B100 100% biodiesel 

B20 20% biodiesel, 80% petrodiesel 

DPPH 2,2-diphenyl-l-picrylhydrazyl 

EN European Normalization 

EPA U.S. Environmental Protection Agency 

FAME fatty acid methyl esters 

GC-MS gas chromatography-mass spectrometry 

GM General Motors 

ICP-AES inductively coupled plasma – atomic emission spectroscopy 

IFT interfacial tension 

MeOH methyl alcohol (methanol) 

MSD mass selective detector 

NBB National Biodiesel Board 

NREL National Renewable Energy Laboratory 

SwRI Southwest Research Institute 

T90 temperature at which 90% of a sample has distilled (or 90% recovery 

temperature) 
1

Executive Summary 

This document reports results gathered from quality surveys of biodiesel and 20% 

biodiesel in petroleum diesel in the United States. This report also documents completion 

of the National Renewable Energy Laboratory’s (NREL) Fiscal Year 2005 Annual 

Operating Plan Milestone 10.3.1, which is also Corporate Planning System Milestone 

21670. These milestones support the U.S. Department of Energy (DOE), Fuels 

Technologies Program Multiyear Program Plan Goal of identifying fuels that can 

displace 5% of petroleum diesel by 2010. 

For these quality surveys researchers collected 27 biodiesel (B100) samples and 50 

biodiesel blend (B20) samples from blenders and distributors nationwide. These 

companies tended to be petroleum terminal operators or wholesalers. The following 

conclusions are based on the results of the B100 and B20 quality surveys conducted: 

 Biodiesel blenders and distributors rely almost entirely on the biodiesel manufacturer 

to ensure fuel quality. Little or no downstream product testing is conducted. 

 The B100 samples included 4 produced from waste oils, 1 produced from tallow, and 

the balance produced from soy (based on a gas chromatography – mass spectrometry 

analysis and cloud point). 

 Of the B100 samples collected, 85% met all of the requirements of American Society 

for Testing and Materials (ASTM) D6751. 

 Samples failing one requirement generally exhibited outlier or failing results for a 

second requirement. 

 Distributors were not, at the time of this survey, distinguishing between S15 (15 ppm 

sulfur maximum) and S500 (500 ppm sulfur maximum) grades of biodiesel. 

 Nearly all of the B100 samples exhibited Na+K and Mg+Ca levels below 5 ppm, a 

level thought to be acceptable for protection of fuel injection equipment. 

 A typical U.S. biodiesel exhibits 5 mg/100 ml of deposits on the ASTM D2274 

accelerated stability test and less than 1 hour induction time on the European 

Normalization (EN) 14112 Rancimat oxidation stability test. There is currently no 

oxidation stability specification for diesel fuels in the United States. 

 The main factors affecting the stability of B100 are natural antioxidant content, 

polyunsaturated fatty ester content, and the level of mono and di-glycerides. 

 An issue with splash blending of B20 blends was identified when it was discovered 

that 18 out of the 50 samples collected were not nominally B20. It is believed that 

insufficient turbulence or splashing occurred during the preparation of these blends. 

 B20 samples showed high levels of peroxides, reinforcing the need for an oxidation 

stability requirement for B100 and perhaps for B20. While peroxide levels were not 

measured for B100, the formation of peroxides is well known as the initial step in fuel 

oxidation. 

 The B20 samples exhibited low levels of water interfacial tension, indicating that 

water separators on engine fuel systems will not perform as intended. The high 

peroxide levels may contribute to the low interfacial tension. 
2

 A typical B20 showed a less than 2 hour Rancimat (EN14112) induction time, but 

this may have been caused by storing the samples used in this study for 6 months 

prior to testing. 

The following are recommendations based on the results of this study: 

 Additional B100 and B20 surveys should be conducted on an ongoing basis to 

monitor the progress of the industry in meeting fuel quality requirements. 

 A future B20 survey should be conducted in winter to allow an assessment of the 

impact of biodiesel blending on low-temperature performance properties. 

 For future studies it is important that all analyses be performed within one month of 

sample collection, especially oxidation stability. 

 Understanding of oxidation stability issues would be greatly enhanced by collection 

of field samples that have undergone significant oxidation. 
3

Introduction 

This document reports results of quality and stability surveys of biodiesel (B100) and 

20% biodiesel (B20) in the United States that were performed for the U.S. Department of 

Energy by the National Renewable Energy Laboratory. Biodiesel is a diesel replacement 

fuel that is becoming increasingly popular in the United States and is being used 

primarily as a fuel extender at blending levels up to 20 volume percent. Approximately 

36 million gallons of biodiesel were consumed in the United States during 2004 [1]. 

While this is only about 0.1% of the total on-road diesel market in the United States, 

biodiesel is still the most widely used renewable diesel fuel. Biodiesel consists of fatty 

acid methyl esters (FAME) produced from vegetable oils, animal fats, or waste cooking 

oil via transesterification with methanol. The primary feedstocks for biodiesel in the 

United States are soybean oil and waste cooking oil (yellow grease). Engine and vehicle 

manufacturers have expressed concern about the quality of this renewable fuel and the 

potential for poor quality fuels to cause excessive wear or premature failure of certain 

engine components. Potential quality issues include the presence of glycerine and 

glycerides, residual inorganic salts from the biodiesel production process, free fatty acids, 

and deposits formed from fuel oxidation. 

Fuel quality specifications in the United States are set by the American Society for 

Testing and Materials (ASTM) International and are referred to as ASTM standards or 

specifications. ASTM sets these standards using a consensus process that involves 

stakeholders from all interested industries and segments of society who have chosen to 

become members of ASTM. A quality specification for 100% biodiesel (B100) has been 

developed (ASTM D6751). The members of ASTM are currently working to finalize a 

specification for 20% biodiesel blends and to change the conventional diesel fuel 

specification (ASTM D975) to allow inclusion of up to 5% biodiesel. 

This study of biodiesel quality was conducted (1) to determine if B100 in the marketplace 

was meeting the D6751 specification, (2) to provide data on other properties of B100 that 

might be included in an updated specification (including stability), and (3) to assess the 

properties of B20 blends in support of the development of a new quality specification for 

these fuels. Magellan Midstream Partners, LLC, collected all samples during calendar 

year 2004. Testing was performed at the Magellan Midstream Partners, LLC laboratory, 

the National Renewable Energy Laboratory (NREL), and industry partner laboratories as 

noted. 

This report documents completion of NREL Fiscal Year 2005 Annual Operating Plan 

Milestone 10.3.1, which is also Corporate Planning System Milestone 21670. These 

milestones support the DOE Fuels Technologies Program Multiyear Program Plan Goal 

of identifying fuels that can displace 5% of petroleum diesel by 2010. 
4

Survey of B100 Quality and Stability 

The quality specification for 100% biodiesel is ASTM D6751. This standard is for a 

biodiesel blendstock—biodiesel to be blended with petroleum diesel to make B20 and 

lower biodiesel content blends. The biodiesel standard was updated in 2003 to include 

both 15 ppm sulfur (S15) and 500 ppm sulfur (S500) grades (S15 grade summarized in 

Table 1). The purpose of each requirement of the standard is reviewed in the discussion 

of results. 

The survey had four components: initial and follow up phone surveys of the fuel handling 

practices of biodiesel distributors; a sample collection and testing program to assess 

biodiesel conformance with ASTM D6751; and an assessment of biodiesel stability. 

Each sample was subjected to all of the tests outlined in the D6751 specification. 

Analyses were also conducted for several metals of interest, for density, and for FAME 

make up. In addition, the following stability methods were employed: 

 European Normalization (EN) 14112 (Rancimat test) 

 ASTM D2274 Standard Test Method for Oxidation Stability of Distillate Fuel Oil 

 ASTM D6468 Standard Test Method for High Temperature Stability of Distillate 

Fuels. 

Table 1. Detailed Requirements for S15 Biodiesel Taken from 

ASTM D6751-03a 

Property Method Limits Units 

Flash Point D93 100.0 min °C 

Water & Sediment D2709 0.050 max. % vol. 

Kinematic Viscosity, 40oC D445 1.9 - 6.0 mm2/sec. 

Sulfated Ash D874 0.020 max. % mass 

Sulfur* D5453 0.0015 max. % mass 

Copper Strip Corrosion D130 No. 3 max. 

Cetane Number D613 47 min. 

Cloud Point D2500 Report to Customer °C 

Carbon Residue** D4530 0.050 max. % mass 

Acid Number D664 0.80 max. mg KOH/gm 

Free Glycerin D6584 0.020 max. % mass 

Total Glycerin D6584 0.240 max. % mass 

Phosphorus content D4951 0.001 max. % max 

Distillation temperature, T90*** D1160 360 max. °C *

The specification also includes a higher sulfur grade of biodiesel, S500, that allows 0.05 wt% sulfur but all 

other requirements are identical. 

 **Carbon residue shall be run on the 100 % sample. ***Atmospheric equivalent temperature 
5

Phone Survey Results 

Initial Survey 

For this phone survey, a list of biodiesel blenders and sellers was obtained from the 

National Biodiesel Board website (www.biodiesel.org). In addition, contacts for several 

other blenders were provided by Magellan. The survey consisted of a series of questions 

regarding the controls established for assuring that consistent quality products are 

delivered to customers. The questions and a tally of the responses follow in Table 2. 

The majority of the respondents did not have contractual terms with suppliers regarding 

product quality, and did not receive analytical reports or perform subsequent product 

testing. Even in this majority, the general sentiment was that the product received is of 

satisfactory quality and met any applicable specifications. Of the 10 respondents who 

perform inspection upon receipt, only two perform any actual quantitative tests. The 

others simply visually examine the product. 

Thus, the burden for product quality rests with the producer. After the product has left 

the producer, there is little surveillance of product quality and thus no established 

mechanism for identifying poor quality or contaminated fuel. Generally the blending 

procedures are the same as those used for blending two or more petroleum products with 

no special provisions for biodiesel. 

One respondent requires the delivery of only “vegetable-based” biodiesel in the winter. 

Another injects an anti-gel additive in the winter. The majority of the respondents did not 

require or request product from a particular producer and did not know the identity of the 

producers for individual batches. 

Table 2. Results of Initial Phone Survey 

 Yes No 

Don't 

Know 

1) Do you purchase biodiesel from only one marketer? 21 8 

2) Is your biodiesel supplied from multiple producers? 16 8 4 

3) Do your contracts specify receipt of a type of biodiesel, e.g., soy? 6 18 5 

4) Are specifications included in a purchasing agreement? 4 20 5 

5) Do you receive an analytical report with each batch of biodiesel? 12 16 1 

6) Do you perform any inspection upon receipt of each batch? 10 19 

7) Do you blend biodiesel w/ petroleum diesel? 20 9 

8) If yes to '7', do you have formal blending procedures? 16 4 

 Of the respondents, 25 received delivery by truck, 2 by rail, 1 both, and 1 drums. 

Follow-up Phone Survey 

A second survey was conducted after the sample-testing element of this project was 

completed. This survey focused on identification of problems that the distributors had 

encountered and the length of storage periods. The questions and responses follow: 
6

1. Have you encountered any problems handling biodiesel? 

 Yes 5 No 14 

2. If yes, what was the nature of the problem(s)? 

 Cold flow upon receipt 3 

 Haze with sediment 1 

 Dirty delivery truck 1 

3. Have you received any customer complaints? 

 Yes 3 No 16 

 

4. If yes, what was the nature of the complaint? 

Customer stored in steel drums outside resulting in water contamination 

Customer blended with an additive that made it look like rice pudding 

Lost power and engine stalled with a depressed clutch. Operating on B80 

to B100 depending on how much diesel fuel is in the tank when the 

customer adds B100 to the tank. 

5. Has anyone complained of a filter plugging problem or injector fouling? 

 Yes 1 No 18 

6. If yes, what do you think caused the problem? 

 Not sure, thinks it was water and sediment 

7. What is the frequency at which the material in your tank is replaced (frequency of 

turns)? 

 < 1 wk 1 to 4 wks 5 to 8 wks > 8 wks 

 2 8 3 1 

8. How do you utilize your tank, e.g., fill completely and then empty? 

 Fill then empties Maintains volume 

 8 6 

9. Do you retain samples of each product receipt? 

 Yes 7 No 12 

D6751 Testing Results 

Twenty-seven samples were obtained nationwide from biodiesel blenders and sellers. 

Each sample was subjected to all of the tests outlined in the ASTM D6751-03a 

specification. Results for each of the samples are shown in Table 3 and indicate that 4 

out of 27 samples, or roughly 15%, exceeded one or more of the limitations. Each 

requirement is discussed individually in the following paragraphs. 
7

Table 3. Results of B100 Analysis 

All samples also met the water and sediment (D2709) requirement and were 1A for copper corrosion. Italics indicate 

D6751-03a limits. 

Sample ID Flash 

Point 

Viscosity Sulfated 

Ash 

Sulfur Cetane Cloud

Point 

Carbon 

Residue 

Acid No. Free 

Glycerine 

Total 

Glycerin 

Ph

Test D93 D445 D874 D5453 D613 D2500 D524b D664 D6584 D6584 

Limit >130°C 1.9-6.0 mm2/s 0.020 wt% 0.05 wt% 47 min °C 0.05 wt% 0.8 mgKOH/g 0.02 wt% 0.24 wt% 0

A 147 4.489 0.000 0.00029 54.7 2 <0.010 0.25 0.003 0.208 

B 153 4.128 0.000 0.00036 49.6 0 <0.010 0.60 0.002 0.202 C 133 4.085 0.005 0.00003 53.7 -2 <0.010 0.33 0.003 0.147 

D 143 4.361 0.015 0.00827 57.7 -1 0.015 0.24 0.004 0.239 

E 133 4.153 0.003 0.00268 53.7 -1 <0.010 0.59 0.003 0.190 

F 147 3.976 0.003 0.00134 58.3 -1 <0.010 0.11 0.012 0.019 

G 157 4.784 0.001 0.00012 48.0 -1 0.015 0.16 0.014 1.23 H >190 3.991 0.000 0.00026 57.2 -1 <0.010 0.05 0.004 0.032 

I 156 4.099 0.000 0.00003 54.3 -1 <0.010 0.97 0.006 0.023 

J >190 4.145 0.000 0.00069 54.4 0 <0.010 0.35 0.004 0.171 

K >190 4.245 0.003 0.00115 51.9 0 0.018 0.76 0.003 0.192 

L 154 3.970 0.000 0.00032 54.7 -1 <0.010 0.05 0.004 0.037 

N 162 4.159 0.000 0.00105 48.8 0 <0.010 0.48 0.004 0.211 O 152 4.093 0.001 0.00012 51.5 1 <0.010 0.70 0.003 0.198 

P 168 3.927 0.000 0.00005 55.1 -2 <0.010 0.03 0.002 0.011 

Q 152 4.107 0.003 0.00010 54.0 0 <0.010 0.34 0.008 0.067 

R 172 4.010 0.003 0.00035 56.4 -1 <0.010 0.02 0.002 0.013 

S 154 3.928 0.005 0.00089 56.1 -1 <0.010 0.02 0.006 0.020 

T >190 4.560 0.011 0.00145 56.3 2 0.043 1.38 0.018 0.317 

U 174 4.122 0.001 0.00006 57.6 -1 <0.010 0.65 0.004 0.195 V 190 4.800 0.000 0.00127 54.2 5 <0.010 0.42 0.009 0.187 

W 161 4.134 0.000 0.00044 52.3 -1 <0.010 0.48 0.005 0.025 

X >190 4.100 0.002 0.00089 52.7 -2 <0.010 0.54 0.011 0.196 Y 159 4.706 0.000 0.00081 65.0 14 <0.010 0.48 0.006 0.058 

Z 161 4.123 0.001 0.00014 53.3 -2 <0.010 0.34 0.001 0.022 

AA 165 4.610 0.000 0.00048 56.0 8 <0.010 0.52 0.005 0.102 

BB >190 4.087 0.001 0.00067 54.8 -1 0.013 0.35 0.014 0.025 

*Based on rounding to 0.001 wt%, this sample meets the phosphorus requirement. 
8

Flash point 

This requirement ensures that the methanol used in production is completely removed from the 

fuel, because of both fire safety concerns and the corrosive nature of methanol. The flash point 

for the samples ranged from 133°C to greater than 190°C; all samples met the requirement of 

130°C minimum. 

Water and sediment 

This test method determines the sum of free water and sediment. Free water is undesirable 

because it may promote microbial growth and corrode fuel system components. Sediment or solid 

impurities are undesirable because of their potential to cause excessive wear in fuel injection 

equipment. All samples met the requirement 0.05 vol% maximum. 

Kinematic viscosity 

Adequate viscosity is required for lubrication and to prevent leakage in metal/metal seals, but 

viscosity must not be so high as to cause seizure of parts, particularly under low-temperature 

conditions. High-viscosity fuel can also cause higher injection pressures leading to increased 

wear and shorter equipment life. Viscosity of the samples ranged from 3.927 to 4.800 mm2

/s, 

with all samples tested meeting the requirement of 1.9-6.0 mm2

/s. 

Sulfated ash 

The sulfated ash requirement is intended to limit the amount of potassium, sodium, magnesium, 

and calcium in the finished biodiesel fuel. These metals can contribute to injector, fuel pump, 

piston and ring wear, engine deposits, and filter plugging. These impurities may be introduced 

from process chemicals used in biodiesel manufacture. Measured values ranged from zero (below 

detection limit) to 0.015 wt%, with all samples meeting the requirement of 0.020 wt% maximum. 

Sulfur 

The sulfur requirement is intended to mirror that in ASTM D975 (Standard Specification for 

Diesel Fuel Oils) and to meet the U.S. Environmental Protection Agency (EPA) requirements for 

on-road diesel fuel. Thus, the sulfur limit as of this writing is 0.05 wt% (or 500 ppm, denoted as 

S500) for on-road diesel fuel, but will be dropped to 0.0015 wt% (or 15 ppm, denoted as S15) 

beginning in September 2006. All samples met the 500 ppm requirement, however, two soyderived samples (D and E) exhibited sulfur in excess of 15 ppm. The soy oil used to produce 

these fuels is inherently low in sulfur (much lower than 15 ppm), thus it seems likely that these 

samples were contaminated with small quantities of higher sulfur materials during handling and 

transport. 

Copper strip corrosion 

Corrosion is of concern because of potential damage to copper components of fuel systems, but 

also because dissolved copper can catalyze oxidation reactions leading to the formation of 

deposits and corrosive free acids. This requirement mirrors the D975 requirement for 

conventional diesel and is designed to ensure that biodiesel is equally compatible with and 

resistant to oxidation by, copper. All biodiesel samples tested exhibited a 1A rating on this test, 

easily meeting the standard of 3 maximum. 
9

Cetane number 

An adequate cetane number is required for ignition and operability. Conventional diesel in the 

United States is required to have a minimum cetane number of 40. Biodiesel produced in the 

United States has a significantly higher cetane number, and therefore, the specification limit was 

set at 47 minimum. All samples tested exceeded this level, easily meeting the standard. In fact, 

the mean, median, and mode of the cetane number results are all roughly 54.5. 

Cloud point 

There is no specific cloud point requirement in D6751, only a requirement that it be measured and 

reported. The purpose of a cloud point specification is to ensure operability at low temperatures. 

The soy-derived samples are all in the range of –2°C to 1°C, with yellow grease and tallowderived fuels exhibiting higher values. Based on cloud point (and confirmed by FAME analysis 

reported below) the following samples were likely produced from yellow grease or waste oil: A, 

T, V, and AA. Sample Y was produced from beef tallow. 

Carbon residue 

This test provides an estimate of the carbon depositing tendencies of a fuel and is designed to 

prevent the formation of combustion chamber deposits. All samples tested met this requirement 

of 0.05 wt% maximum. Sample T had the highest value of 0.043 wt%, and also failed the acid 

number and total glycerin tests. High levels of glycerides are expected to contribute to engine 

deposit formation and hence to a higher carbon residue. 

Acid number 

This test measures the presence of corrosive free fatty acids and oxidation products. Two of the 

samples tested exhibited acid numbers above the maximum limit of 0.8 mg KOH/g. For Sample I 

there are no obvious clues in the data as to why acid number is high, and this sample may have 

undergone some oxidation. For Sample T, total glycerin is also high, and carbon residue is the 

highest value observed. 

Free and total glycerin 

Total glycerin includes the sum of free glycerin and mono, di, and tri-glycerides, all reported as 

mass percent glycerin and determined by gas chromatography. Results for the individual 

glycerides can be found in Appendix A. Free glycerin can cause fuel separation and materials 

compatibility problems. Glycerides have much higher boiling points than biodiesel or 

conventional diesel fuel, and can lead to engine deposits and durability problems. All samples 

met the free glycerin requirement of 0.02 wt% maximum, however, two samples failed the total 

glycerin requirement of 0.24 wt% maximum. One of these is Sample T, as already noted. In 

addition, Sample G exhibited high total glycerin but met all other requirements. 

Phosphorus 

The intent of this requirement is to protect exhaust catalysts, which are becoming more and more 

common on diesel equipment. Sample D exhibited 0.003 weight percent phosphorus and thus 

failed to meet the requirement of 0.001 weight percent maximum (10 ppm). Given the high sulfur 

content of this sample, it is possible that it was contaminated with a small amount of motor oil, 

which contains both sulfur and phosphorus as part of the antiwear additive package. Metals 

analysis (discussed in the following section of this report) supports this contention. 
10

Distillation temperature (T90) 

This requirement ensures that the biodiesel has not been altered with significant amounts of high 

boiling components, such as used motor oil. All biodiesel samples exhibited T90 in a narrow 

range from 351°C to 357°C, and thus met this requirement of 360°C maximum. As noted above, 

Sample D appeared to be contaminated with a small amount of motor oil. The amount of oil was 

enough to cause the sample to be out of specification on phosphorus, but not enough to influence 

the T90. 

Results of Additional Tests 

A number of additional tests that are not included in ASTM D6751 were conducted to provide 

additional information and an assessment of the potential usefulness of these tests as added 

requirements in D6751. 

Metals 

The presence of metals in the biodiesel can cause operability problems due to formation of 

deposits and poisoning of emission control devices, or can catalyze reactions that cause undesired 

products. The metals of interest include sodium (Na) and potassium (K), used as catalysts in 

biodiesel production; and magnesium (Mg) and calcium (Ca), used in adsorbents for purifying 

biodiesel. Fuel injection equipment manufacturers have proposed to limit the content of Na+K 

and of Mg+Ca to 5 ppm each. Additionally, we tested for copper (Cu), iron (Fe), and zinc (Zn). 

Each of these metals can catalyze oxidation, however, copper and zinc in particular can be highly 

active for initiating oxidation of polyunsaturated methyl esters [2]. Zinc can enter the fuel if it is 

contaminated by lube oil. Metals analyses were performed in conjunction with testing of the 

samples for phosphorus content via ASTM D4951 by inductively coupled plasma atomic emission 

spectroscopy (ICP-AES), and results are shown in Table 4. 

For all samples potassium levels were below detection limits. All samples but one contained less 

than 5 ppm of sodium. The high-sodium sample is Sample T, which also failed D6751 

requirements for acid number and total glycerin. Clearly this low-quality sample was not 

adequately washed for removal of residual catalyst. B100 samples also exhibited generally low 

levels of magnesium and calcium. However, Sample D exhibits high levels of both of these 

metals. This sample also failed the D6751 phosphorus limit and exhibited 83 ppm of sulfur. 

Table 5 also shows this sample having high levels of zinc. All of these features are consistent 

with contamination by lube oil. For other samples with moderately elevated calcium content (5 or 

6 ppm), the source is likely the use of hard water for product washing. 

Iron levels ranged from 1 to 12 ppm. Dissolved iron can be a potent oxidation catalyst and thus 

may contribute to biodiesel instability. Copper content was typically 0-2 ppm, but one sample (N) 

exhibited 5 ppm. Other than sample D, four samples had zinc content in the 4-8 ppm range. 

However, it is not known if these levels are high enough to cause stability issues. The impact of 

metals content on stability will be explored in the following section of this chapter. 
11

Density 

Density was also measured and is reported in Table 4. The density of B100 is typically 0.88 g/ml, 

significantly higher than is typical of petroleum diesel, which ranges from 0.84 to 0.86 g/ml. 

Table 4. Results of Additional Analyses Performed on B100 Samples 

Results of additional analyses performed on B100 samples 

(a measured value of 0 indicates below detection limit). 

Sample 

ID Calcium Copper Iron Magnesium Potassium Sodium Zinc Density 

 ICP 

D4951 

ppm 

ICP 

D4951 

ppm 

ICP 

D4951 

ppm 

ICP 

D4951 

ppm 

ICP 

D4951 

ppm 

ICP 

D4951 

ppm 

ICP 

D4951 

ppm 

D4052 

 @ 60 °F 

(g/mL) 

A 2 0 1 0 0 3 6 0.8826 

B 4 0 1 0 0 2 4 0.8826 

C 0 0 1 0 0 1 1 0.8845 

D 35 0 1 7 0 2 38 0.8862 

E 6 0 1 0 0 1 4 0.8845 

F 0 0 2 0 0 0 1 0.8835 

G 0 2 1 0 0 2 0 0.8888 

H 1 0 1 0 0 0 0 0.8847 

I 0 0 3 0 0 0 0 0.8838 

J 2 2 1 1 0 1 2 0.8850 

K 0 1 12 0 0 2 2 0.8852 

L 0 0 1 0 0 0 0 0.8837 

N 1 5 1 0 0 2 2 0.8847 

O 0 0 1 0 0 3 0 0.8846 

P 0 0 1 0 0 0 0 0.8836 

Q 5 0 2 0 0 0 1 0.8839 

R 0 1 1 0 0 0 0 0.8838 

S 0 0 1 0 0 0 0 0.8833 

T 1 0 9 1 0 37 0 0.8826 

U 0 0 1 0 0 1 0 0.8827 

V 0 0 1 0 0 1 5 0.8798 

W 2 1 4 0 0 0 1 0.8838 

X 2 0 2 0 0 2 8 0.8831 

Y 1 0 1 0 0 0 0 0.8751 

Z 1 1 1 0 0 1 1 0.8823 

AA 1 0 1 0 0 0 0 0.8768 

BB 0 1 3 0 0 0 2 0.8817 

Fatty Acid Speciation 

A subset of the biodiesel samples was analyzed by gas chromatography with mass spectrometric 

detection (GC-MS). Method details and a complete table of results are found in Appendix B. The 

FAME results are summarized in Figure 1. The results show obvious similarities between most of 

the soy samples (samples B through U). Sample Z is also soy-derived but contains lower C18:3†

and higher C18:2 than the others. The sample A was originally thought to be soy methyl esters, 

 

†

 The notation Cxx:y indicates a methyl ester with an xx carbon atom fatty acid chain containing y double bonds. For 

example, methyl oleate or CH3(CH2)7CH=CH(CH2)7COOCH3 is denoted C18:1. 
12

but contains higher amounts of methyl palmitate and methyl stearate than the soy-derived 

samples; therefore, it is most likely derived from waste cooking oil. The oleate/linoleate ratio is 

higher as well (0.77 versus a more typical 0.44). The data suggest that this sample may contain 

methyl esters from non-soy feedstocks. The other waste grease samples (V and AA) contain 

relatively high amounts of saturated FAME and otherwise indicate variability in composition as 

would be expected. Sample T is also likely derived from waste grease given its slightly high 

cloud point. Sample Y is derived from beef tallow and contains high concentrations of saturated 

C14, C16, and C18 as expected. 

Biodiesel Sample Label

A B F G H K N O R U V Y Z AA

Weight Percent

0

20

40

60

80

100

C16:0

C16:1

C18:0

C18:1

C18:2

C18:3

Figure 1. Results of analysis of selected B100 samples for FAME content 

Only species with concentration greater than 1 wt% shown; detailed analyses in Appendix B. 

Testing of B100 Stability 

Biodiesel, without modifications or treatment with additives, is inherently less stable than a 

typical petroleum diesel. However, there are no limits for stability in the accepted industry 

standard for biodiesel, ASTM D6751. Companies that transport and store biodiesel are concerned 

that the fuel does not form sediment in storage. They are also interested in knowing what 

precautions can be taken to ensure satisfactory storage characteristics. Vehicle and equipment 

operators need assurances that sediment and gum do not form during use. For these reasons, the 

B100 survey was expanded to examine the stability characteristics of fuels in commerce and take 

a more in-depth evaluation of the merits of various stability test methods. 

Methods 

Three accelerated stability test methods were performed on each of the samples collected for the 

survey: ASTM D2274, Standard Test Method, Test Method for Oxidation Stability of Distillate 

Fuel Oil (Accelerated Method), ASTM D6468, Test Method for High Temperature Stability of 

Distillate Fuels, and EN14112 (Rancimat). D2274 and the Rancimat test are designed to predict 
13

storage stability, and the D6468 test provides an indication of thermal or in-use stability. A 

simple procedure for measuring the total antioxidant content of a biodiesel sample was developed 

and applied in this study [3], and method details are given in Appendix C. 

In the Rancimat method, the sample is exposed to a stream of air at 110°C. The stream of air 

carries volatile carboxylic acids (primarily formic acid [4]) that are formed in the oxidation 

reaction into an absorber section that contains demineralized water. The amount of acids that are 

captured is quantified by measuring the increase in the conductivity of the water. The reported 

measurement is the induction period, which is the amount of time from the beginning of the air 

purge until a sharp increase in the conductivity is observed. The induction period is reported in 

terms of hours. 

In the D2274 method, the sample is heated to 95°C and exposed to pure oxygen for a period of 16 

hours. After this reaction time, the amount of sediment (filterable insolubles) and gum (adherent 

insolubles) are determined. The total of these two reaction products is classified as Total 

Insolubles and is reported in terms of milligrams per 100 milliliters of sample. The filtration 

element of the D2274 test method is generally revised for biodiesel due to the tendency for 

biodiesel to dissolve or swell the filter pads that are called for in the method. Normally a Teflon 

filter is used. In this project, glass fiber filters were used. Irrespective of the filtration medium, 

the nature of the material that is retained on the filter poses a problem. Normally the filterable 

insolubles that are generated in the reaction appear as a granular material on the filter pad. The 

material generated in this project was a rather viscous material that appeared to migrate through 

the filter pad with sufficient vacuum and time. For this reason, the analysts attempted to keep the 

duration of the filtration procedure as consistent as possible. 

The D6468 test exposes the sample to air at a temperature of 150°C for a period of 180 minutes. 

After this reaction period, the sediment that is formed during the reaction is captured on a filter 

paper, and the reflectance of the sediment of a particular light source is measured. In this project, 

after the reflectance was measured the amount of sediment on the filter paper was determined 

gravimetrically, and the acidity of the sample was determined. 

Oxidation Stability Results 

The data from the Rancimat tests were widely varied ranging from 0.1 to 6.0 hours, as shown in 

Figure 2, and a frequency distribution is shown in Figure 3. The European standard for biodiesel 

has a stability specification of a minimum induction period of 6.0 hours [5]. Only one sample in 

this sample set would pass the European specification—sample AA. The majority of the samples 

exhibited an induction period of less than one hour. Additionally, there was no correlation of the 

Rancimat results with the initial acid values of the samples (correlation coefficient of 0.05). 

The results for the D2274 test are shown in Figure 4 for total insolubles. The reaction generated 

equal quantities of filterable and adherent insolubles. The average amount of filterables was 2.46 

mg/100mL, and the average amount of adherent insolubles was 2.47 mg/100mL. The standard 

deviations for the filterables and adherent insolubles were 1.6 and 1.2, respectively. Figure 5 

shows a frequency distribution for total insolubles. A typical biodiesel produced on the order of 5 

mg/100 ml. 
14

With the goal of improving accuracy and precision, a number of potential modifications to the 

D2274 test method were investigated. This activity is described in Appendix D. In addition, in 

another project performed for NREL [6], it has been shown that precipitation of insolubles with a 

non-polar solvent such as heptane can approximately double the amount of insolubles collected, 

potentially improving both method precision and accuracy. 

Sample ID

A B C D E F G H I J K L N O P Q R S T U V W X Y Z AABB

Rancimat Induction Time, hr

0

1

2

3

4

5

6

7

Figure 2. Rancimat (EN14112) induction time for the B100 quality survey samples 
15

Rancimat Induction Time, hr

Frequency

0

2

4

6

8

10

12

14

16

18

European Biodiesel 

Stability Standard

<1 1 - 2 2 - 3 3 - 4 4 - 5 5 - 6 6 - 7

Figure 3. Frequency distribution for B100 Rancimat induction times 

Sample ID

A B C D E F G H I J K L N O P Q R S T U V W X Y Z AABB

Total Insolubles (D2274), mg/100 ml

0

2

4

6

8

10

12

Figure 4. ASTM D2274 results for the B100 quality survey samples 
16

D2274 Total Insolubles, mg/100 ml

Frequency

0

2

4

6

8

10

12

14

16

0.46 - 2.4 2.41 - 4.35 4.36 - 6.30 6.31 - 8.24 8.25 - 10.2

Figure 5. Frequency distribution for D2274 results, B100 

Oxidation Stability Discussion 

A comparison of Figures 3 and 5 indicates that Rancimat and D2274 results are not well 

correlated, as is confirmed in Figure 6. While there is a rough inverse correlation, it is clear that 

some samples with short induction times also have fairly low levels of insolubles (note the sample 

with approximately 1 hour Rancimant and 2 mg/100 ml of insolubles), and samples with long 

induction times can have insolubles as high as 4 mg/100 ml. This highlights the fact that these 

two test methods have a very different premise. The D2274 method exposes the fuel for a long 

period of time (16 hrs) to highly oxidizing conditions (oxygen at 95°C). The inherent potential of 

the material being tested to form polymers under these conditions is measured. The Rancimat 

test, on the other hand, measures the length of time at 110°C in air before volatile acidic oxidation 

products begin to form. Thus the Rancimat test seems more suited to predicting how long a 

material can withstand oxidative conditions, not its inherent tendency to form polymers. 
17

Rancimat Induction Time, hr

01234567

D2274 Total Insolubles, mg/100 ml

0

2

4

6

8

10

12

Figure 6. Comparison of results for D2274 and Rancimat oxidation stability tests 

Given the relatively extensive characterization of these samples, it is also possible to utilize the 

data to assess the factors that are important in oxidation stability for biodiesel. One potential 

factor mentioned above is metals content. However, for the samples tested here, there was no 

correlation between D2274 results or Rancimat results, and the concentrations of copper, iron, 

zinc, or the sum of all three metals in these samples. 

There is a significant effect of antioxidant content on the D2274 test results, as shown in Figure 7. 

The first important feature of the data shown in this figure is that the antioxidant content of 

biodiesel had a range of roughly one order of magnitude (less than 0.5 to nearly 6), and that for 

the soy biodiesel samples, insoluble formation can also vary by nearly a factor if 10. For the soy 

diesel samples (which all met D6751 and have very similar C18:2 and C18:3 content) the relative 

antioxidant content was a generally good predictor of insolubles formation. Results for the more 

highly saturated grease and tallow-derived samples generally fall below the line suggested by the 

soy-antioxidant relationship. Finally, samples with total glycerin content exceeding the limit 

defined in ASTM D6751 exhibit significantly higher levels of insolubles formation than 

anticipated based on their antioxidant content or polyunsaturateded fatty ester content. 
18

Relative Antioxidant Content

01234567

D2274, mg/100 ml

0

2

4

6

8

10

12

Soy biodiesel

Grease and tallow biodiesel

High glyceride content (failing D6751)

Tallow

Various Greases

Figure 7. Relationship between relative antioxidant content and D2274 insolubles 

for different groups of biodiesel samples 

A plot similar to Figure 7, but for Rancimat induction time, is shown in Figure 8. Here the effect 

of antioxidant content, total glycerin content, and polyunsaturated content is not as clear; although 

more highly saturated samples and samples with higher antioxidant content do exhibit longer 

induction time. Another way to examine these data is to use some measure of unsaturation as the 

dependent variable. Such a measure is the oxidizability [7], defined as: 

Oxidizability = [0.02(% oleic) + (% linoleic) + 2(%linolenic)]/100 

This derived parameter applies only to biodiesel or fat containing predominantly 18 carbon fatty 

acid chains, such as the samples examined here. The coefficients for oleic (C18:1), linoleic 

(C18:2), and linolenic (C18:3) fatty esters are proportional to the relative rates of oxidation of 

these compounds [8]. The relationship between Rancimat induction time and oxidizability is 

shown in Figure 9. All of the soy biodiesel samples examined have nearly the same fatty acid 

ester composition and hence the same oxidizability. Hence this parameter is not successful at 
19

discriminating between these samples. For the grease and tallow-based biodiesel, however, 

oxidizability seems to be a reasonable predictor of Rancimat induction time. A similar plot for 

D2274 insolubles could be made. 
20

Relative Antioxidant Content

01234567

Rancimat Induction Time, hr

0

2

4

6

8

Soy biodiesel

Grease and tallow biodiesel

High glyceride content (failing D6751)

Tallow

Various Greases

Figure 8. Relationship between relative antioxidant content and Rancimat 

induction time for different groups of biodiesel samples 
21

Oxidizability

0.2 0.4 0.6 0.8 1.0

Rancimat Induction Time, hr

0

2

4

6

8

Soy biodiesel

Grease and tallow biodiesel

High glyceride content (failing D6751)

Figure 9. Relationship between oxidizability and Rancimat induction time for 

different groups of biodiesel samples 

It is clear that additional research is required for a quantitative understanding of the factors that 

impact stability on these tests. However, for the samples examined here, the formation of 

insolubles on the D2274 test is measurably influenced by the antioxidant content, polyunsaturated 

content (or oxidizability), and the total glycerin content. The Rancimat induction time, on the 

other hand, appears to be mainly influenced by the oxidizability and to a lesser extent by the 

antioxidant content. 

Thermal Stability Results 

Gravimetric results for the D6468 test are shown in Figure 10, and a frequency distribution is 

shown in Figure 11. Values ranged from less than 1 mg/100 ml to over 25 mg/100 ml. For 
22

petroleum diesel fuel, the standard test procedure measures filter reflectance rather than mass. 

The sediments that are formed in diesel fuel as a consequence of fuel instability in the D6468 test 

are generally dark. The sediments, when retained on a filter pad, do not reflect light nearly as well 

as the pad itself. Thus, with petroleum diesel fuel, there is a strong correlation between the 

decrease in reflectance and fuel instability. For the test conditions used here (150°C for 180 

minutes) a minimum value of 70% reflectance is typically cited. The sediment that is formed 

during biodiesel instability reactions tends to not be as dark and coarse. Therefore these 

sediments tend to decrease reflectance to a lesser degree. The data associated with the D6468 test 

confirm this. The absolute values of the correlation coefficients associated with the amount of 

gravimetrically determine total insolubles to the reflectance, and the initial acid values were both 

less than 0.10. 

Thermal Stability Discussion 

It is difficult to interpret these results without some reference to gravimetric data on petroleum 

diesel fuels. Westbrook and Stavinoha [6, 9] have presented reflectance and gravimetric data for 

three petroleum diesel and three biodiesel samples. For this small dataset, petroleum fuels with 

less than 70% reflectance also produced approximately 10 mg/100 ml or more of filterable 

insolubles. The three biodiesel samples tested exhibited near 100% reflectance and filterable 

insoluble levels of 4 mg/100 ml or less. Earlier results presented by Lawrence [10], and shown 

here as Figure 12, confirm this approximate level. For the B100 samples examined here, 18 out of 

27 produced filterable insolubles of 10 mg/100 ml or less, the remaining 9 samples were above 

this level. Several of Lawrence’s biodiesel samples also exceeded this level. 

Clearly additional work is required to fully quantify biodiesel thermal stability. While both the 

Southwest Research Institute (SwRI) and Magellan have implemented gravimetric versions of the 

D6468 test, it is not clear that both laboratories are performing insolubles measurements in the 

same way. Additionally, there are no data to allow an assessment of the precision of this modified 

test. 
23

Sample ID

A B C D E F G H I J K L N O P Q R S T U V W X Y Z AABB

D6468 Gravimetric Insolubles, mg/100 ml

0

5

10

15

20

25

30

Figure 10. D6468 results for B100 quality survey samples 

Modified D6468 Total Insolubles, mg/100 ml

Frequency

0

2

4

6

8

10

12

14

16

0.5 - 5.5 5.5 - 10.6 10.6 - 15.6 15.6 - 20.6 20.6 - 25.6

Figure 11. Frequency distribution for B100 Rancimat induction times 
24

0

10

20

30

40

50

60

70

80

90

100

#2 LS Diesel

A

#2 LS Diesel

B

#2 HS Diesel

A

#2 HS Diesel

B

Soydiesel Canola YGdiesel

Fuels

% Reflectance

0

2

4

6

8

10

12

14

16

18

mg / 100 mL

% Reflectance Weight

Figure 12. D5468 gravimetric and reflectance results for several diesel and B100 

samples [10] 

B100 Summary and Discussion 

The phone surveys revealed that the distributors rely almost exclusively on the upstream party to 

deliver an on-specification, quality product. There is little recognition that problems can arise in 

the distribution chain. The data that comprise this survey tend to validate this approach. The offspecification conditions associated with these samples appear to stem from the production 

process. There was no evidence that any of the off-specification conditions or marginal results 

were the consequence of fuel handling practices. Given the lack of problems encountered by the 

distributors, the implementation of a formal quality control program will have to be driven by a 

demand from the downstream customers. 

Of the 27 B100 samples, four (15%) did not comply with the standard specification for at least 

one fuel parameter. One sample was off-specification in terms of phosphorus, two for Total 

Glycerin, and two for Acid Number. Of the four off-specification samples, one was offspecification to the extent that immediate performance problems would probably result, depending 

on the concentration of biodiesel in the final blend. The other three off-specification samples 

would probably cause problems if a vehicle were to operate on the fuel over an extended period of 

time. 

The ASTM specification for diesel fuel, D975, identifies five grades of fuel. From the point of 

production to the retail outlet, the fuel is identified as one of these five grades. None of the survey 

participants identified the biodiesel they handle or the sample that was submitted as being one of 

the two grades found in the ASTM specification for biodiesel. Two of the samples of biodiesel 
25

had sulfur concentrations greater than 15 ppm, the maximum allowable level for S15 grade. 

However, since the fuel was not identified as either S15 or S500, it is not possible to determine if 

the samples meet the specification. 

In Table 5, data points that are outliers for each parameter are identified. The outliers were 

determined using the Grubbs’ test at a significance level of 0.05. In all cases, an outlier data point 

was accompanied by another outlier data point or an off-specification condition for that sample. 

Of the four samples that had an off-specification condition, three had an outlier data point for a 

different parameter, which was not an off-specification condition. In other words, it is rare for a 

sample to have only one abnormal condition. 

Analysis of the B100 samples for Na and K indicates that the biodiesel has low levels of these 

contaminants in almost all cases. Analysis for Mg and Ca also generally shows low levels, 

however, there are several samples with more than 5 ppm of these metals. We speculate that the 

high levels of Mg and Ca mostly likely resulted from the use of hard water for washing. 

The surveys of B100 stability show that a typical biodiesel has a short Rancimat induction time of 

less than one hour, and generates roughly 5 mg/100 ml of total insolubles in the D2274 

accelerated stability test. However, a broad range of stability is indicated by the results with 

several samples showing much higher stability than typical. Additional research will be required 

to understand the implication of these results for inclusion of a stability requirement in ASTM 

D6751. The main factors affecting insoluble formation were antioxidant content, polyunsaturated 

content, and total glycerin content. The main factors affecting induction time were 

polyunsaturated content and antioxidant content. 

Neither of the two storage stability methods had a significant correlation to the thermal stability 

method (D6468). The correlation coefficients for the D6468 and Rancimat data, and the D6468 

and D2274 data were -0.14 and -0.03 respectively. Even though D6468 is a test for thermal 

stability and the other methods focus on storage stability, in petroleum diesel fuel there is some 

correlation associated with the methods. Results of the gravimetric thermal stability test for the 

biodiesels showed a wide range of results. Based on limited data, several of these samples may 

have produced levels of insolubles high enough for them to be classified as unstable. However, 

because this test is probably most meaningful as a predictor of what will happen to a finished fuel 

in the high temperature environment of an engine’s fuel system, and because B100 samples will 

be used primarily as blending components rather than finished fuels, it is difficult to interpret 

these results. 
26

Table 5. Identification of Outliers via Grubb’s Test 

Sample ID 

D445 

Kinematic 

Viscosity 

@ 40 °C 

(cSt) 

D874 

Sulfated 

Ash (% 

mass) 

D5453 

Sulfur 

(% mass) 

D613 

Cetane 

Number 

D2500 

Cloud 

Point 

(°C) 

D524b 

Carbon 

Residue 

(% mass) 

D664 

Acid 

Number 

(mg 

KOH/g) 

D6584 

Free 

Glycerin 

(% mass) 

D6584 

Total 

Glycerin 

(% mass) 

D4951 

Phosphorus 

Content (% 

mass) 

Specs 1.9 - 6.0 0.020 .0015 & .05 47 Report 0.05 0.8 0.02 0.24 0.001 

A 4.489 0.000 0.00029 54.7 2 <0.010 0.25 0.003 0.208 0.0006 

B 4.128 0.000 0.00036 49.6 0 <0.010 0.60 0.002 0.202 0.0008 

C 4.085 0.005 0.00003 53.7 -2 <0.010 0.33 0.003 0.147 0.0005 

D 4.361 0.015 0.00827 57.7 -1 0.015 0.24 0.004 0.239 0.0030 

E 4.153 0.003 0.00268 53.7 -1 <0.010 0.59 0.003 0.190 0.0007 

F 3.976 0.003 0.00134 58.3 -1 <0.010 0.11 0.012 0.019 0.0007 

G 4.784 0.001 0.00012 48.0 -1 0.015 0.16 0.014 1.227 0.0005 

H 3.991 0.000 0.00026 57.2 -1 <0.010 0.05 0.004 0.032 0.0005 

I 4.099 0.000 0.00003 54.3 -1 <0.010 0.97 0.006 0.023 0.0002 

J 4.145 0.000 0.00069 54.4 0 <0.010 0.35 0.004 0.171 0.0003 

K 4.245 0.003 0.00115 51.9 0 0.018 0.76 0.003 0.192 0.0006 

L 3.970 0.000 0.00032 54.7 -1 <0.010 0.05 0.004 0.037 0.0010 

N 4.159 0.000 0.00105 48.8 0 <0.010 0.48 0.004 0.211 0.0008 

O 4.093 0.001 0.00012 51.5 1 <0.010 0.70 0.003 0.198 0.0010 

P 3.927 0.000 0.00005 55.1 -2 <0.010 0.03 0.002 0.011 0.0003 

Q 4.107 0.003 0.00010 54.0 0 <0.010 0.34 0.008 0.067 0.0013 

R 4.010 0.003 0.00035 56.4 -1 <0.010 0.02 0.002 0.013 0.0002 

S 3.928 0.005 0.00089 56.1 -1 <0.010 0.02 0.006 0.020 0.0004 

T 4.560 0.011 0.00145 56.3 2 0.043 1.38 0.018 0.317 0.0000 

U 4.122 0.001 0.00006 57.6 -1 <0.010 0.65 0.004 0.195 0.0002 

V 4.800 0.000 0.00127 54.2 5 <0.010 0.42 0.009 0.187 0.0000 

W 4.134 0.000 0.00044 52.3 -1 <0.010 0.48 0.005 0.025 0.0001 

X 4.100 0.002 0.00089 52.7 -2 <0.010 0.54 0.011 0.196 0.0002 

Y 4.706 0.000 0.00081 65.0 14 <0.010 0.48 0.006 0.058 0.0004 

Z 4.123 0.001 0.00014 53.3 -2 <0.010 0.34 0.001 0.022 0.0007 

AA 4.610 0.000 0.00048 56.0 8 <0.010 0.52 0.005 0.102 0.0000 

BB 4.087 0.001 0.00067 54.8 -1 0.013 0.35 0.014 0.025 0.0006 

Outliers but not off-spec Outliers and off-spec 

Offspec Marginal result Outliers and not S15 
27

B20 Fuel Quality Survey 

Methods 

Fifty fleets using B20 from across the country were selected to participate in the B20 

quality survey. The basis of selection was two-fold: to represent the range of weatherrelated operating environments across the United States, and to represent all of the U.S. 

major (greater than 1 million gallons annual production) biodiesel producers. However, 

samples were collected in August and September of 2004 so the survey does not reveal 

properties relevant to wintertime operation. 

The test plan consisted of tests or properties to be measured for the B20 samples, as 

shown below in Table 6. Magellan Midstream Partners performed all tests except 

oxidation stability by Rancimat. Robert Bosch Corporation and SwRI supplied replicate 

Rancimat data sets. In addition, Parker-Racor supplied interfacial tension measurements. 

The National Biodiesel Board’s (NBB) B20 Fleet Evaluation Team, a committee of 

primarily automotive industry technical experts, proposed this list of tests. 

Table 6. Tests Conducted for B20 Samples 

Property Test Method 

Water and Sedimenta ASTM D2709 

Visual Appearance ASTM D4176 Procedure 2 

Acid Number WLS-102 (Field Acid Number) 

Kinematic Viscosity ASTM D445 

Silver Strip Test IP227 

Peroxide Number ASTM D3703 

Oxidation Stability EN14112 (Rancimat) 

Water Extraction GM Test Method 

Density ASTM D4062 

Carbon Residue ASTM D524 

Biodiesel Content FTIR Method 

Cloud Point ASTM D2500 

Distillation (T90) ASTM D86 

Sulfur Content ASTM D5453 or D2622, as appropriate a

Test to be conducted only if D4176 haze rating is significant. 

Results 

All test results are listed in Appendix E. Results for the following tests showed no reason 

for concern (i.e., meeting D975 requirements for No. 2 diesel or otherwise within normal 

range): Water and Sediment, Visual Appearance, Kinematic Viscosity, Silver Strip 

Corrosion, Density, and Carbon Residue. The results for the balance of the tests 

conducted are discussed in more detail below. 
28

Biodiesel Content 

Figure 13 shows results of biodiesel content determination for the 50 B20 quality survey 

samples. Thirty-two of the samples were nominally B20 (between 18 and 22 percent 

biodiesel), while the remaining 18 samples exhibited biodiesel content from 7% to 98%. 

We believe that this indicates a serious issue with biodiesel blending practices. However, 

it should be noted that no specific protocol was followed for the collection of these 

samples. Most blenders prepare blends by so-called splash blending, where the blends 

are prepared by pumping biodiesel and petroleum diesel sequentially into a tank 

(typically a transport truck or storage tank). Apparently in many cases a homogeneous 

mixture of biodiesel and petroleum diesel is not being obtained. Because B100 is slightly 

more dense than petroleum diesel, a poorly blended tank will have a high biodiesel 

content on the bottom of the tank and a low biodiesel content at the top of the tank. 

While the use of blends containing less than 20% biodiesel is not a concern from a 

maintenance and durability standpoint, the use of blends with dramatically high biodiesel 

content can cause serious issues. The NBB is currently working with biodiesel producers 

and blenders to make sure that proper blending procedures are followed. These primarily 

involve insuring that adequate splashing or turbulence is occurring during splash 

blending. As the industry grows, a transition from splash blending to in-line blending 

should occur and will eliminate this problem. 

Sample No.

0 5 10 15 20 25 30 35 40 45 50 55

Percent Biodiesel (FTIR Method)

0

20

40

60

80

100

Figure 13. Percent biodiesel content for B20 quality survey samples 
29

Acid Number 

The range of acid numbers of the B20 samples is shown in Figure 14. Two samples 

exhibited high acid number (>0.6 mgKOH/g). 

Percent Biodiesel

0 20 40 60 80 100

Acid Value

0.0

0.2

0.4

0.6

0.8

All samples

Nominally B20

Figure 14. Acid number (WLS-102) of B20 samples as a function of percent 

biodiesel 

Cloud Point 

Figure 15 shows the range of cloud points encountered in the B20 samples. The cloud 

point of the B20 samples range from a low of -21°C (-6oF) to a high of 6°C (42oF). It 

must be noted that these samples were collected in September and October of 2004, prior 

to the beginning of the winter fuel season in most of the country. Thus the observed 

cloud point results are primarily for summertime fuels where cloud point is not 

significantly limited, but the geographic location of the samples may also influence the 

cloud point of the blends. The ASTM diesel fuel specification (D975) does not contain a 

cloud point specification; the cloud point is reported. Fuel manufacturers adjust the cloud 

point of the fuel to ensure consistent product quality on a market-by-market basis. 

Distillation 

Figure 16 shows 90% recovery distillation temperatures for the survey samples. Many of 

the B20 samples meet the 338°C (640oF) upper limit for No. 2 diesel fuel, but a 

significant fraction does not. This suggests that any future B20 quality specification will 

require a slightly higher T90 limit than is currently used for No. 2 diesel. 
30

Percent Biodiesel

0 20 40 60 80 100

Cloud Point, 

o

F

-10

0

10

20

30

40

50

Cloud Point, C

All samples

Nominally B20

-23

-18

-12

-7

-1

4

10

Figure 15. Cloud point (ASTM D2500) as a function of biodiesel content for 

B20 survey samples 

Percent Biodiesel

0 20 40 60 80 100

Distillation T90, 

o

F

600

620

640

660

680

700

Distillation T90, C

All samples

Nominally B20

338

327

316

349

360

371

Figure 16. Distillation results (ASTM D86) for B20 quality survey samples 

(horizontal dashed line shows upper T90 limit for No. 2 diesel fuel). 

Peroxide Value 

Figure 17 shows results of peroxide value measurements for the quality survey samples. 

Peroxides can form as a result of biodiesel or petroleum diesel oxidation, and ultimately 
31

can decompose yielding aldehydes, acids, and polymers. Thus peroxides are 

intermediates in the fuel oxidation process. They are of concern because of the potential 

to form acids and deposits, and also because certain fuel system plastics and elastomers 

may degrade in the presence of certain types of peroxides. The results show a broad 

range of peroxide content from values less than 10 and are not of concern to values of 

several hundred. 

While these high-peroxide values may raise significant issues, there are a number of 

unanswered questions that must be answered in order to understand their significance. 

First, we do not know the peroxide content of a typical diesel fuel, nor do we know the 

tolerance of diesel fuel system elastomers/plastics for diesel fuel derived peroxides. 

Second, this method for measuring peroxides was not developed specifically for biodiesel 

or biodiesel blends but for testing of gasoline and jet fuel. Thus it is possible that the 

reported high-peroxide values are an experimental artifact of applying this method to a 

substance for which it was not intended, and that peroxide levels are not, in fact, this 

high. Research to answer these questions is currently ongoing. Additionally, in the near 

future, the B100 quality specification will be modified to include an oxidation stability 

requirement. This will presumably prevent or limit the potential for peroxide formation. 

Percent Biodiesel

0 20 40 60 80 100

Peroxide Number, ppm

0

100

200

300

400

All samples

Nominally 20%

Figure 17. Peroxide value (or number) determined by ASTM D3703 for 

quality survey samples 

Interfacial Tension 

Parker-Racor kindly supplied the results for interfacial tension. These tests were 

conducted using ASTM D971 Interfacial Tension of Oil Against Water by the Ring 

Method. Results of water interfacial tension (IFT) measurements are shown in Figure 18. 

Having an adequately high IFT is required for on-board vehicle water separators that 

operate based on coalescence. A coalescer that operates in the upper 95% efficiency 
32

range in high IFT fuel (around 30 dynes/cm) may drop up to 30% efficiency as the IFT 

decreases below 25 dynes/cm depending on the type of medium being used in the 

coalescer (per SAE J1488). So, coalescence as a mechanism for water separators (which 

most water separators depend on) is highly influenced by fuel chemistry (i.e., IFT). 

Of the 33 samples analyzed, only six displayed IFTs above 15 dynes/cm. There were 13 

samples that had IFTs at or below 10 dynes/cm. Of the six samples that had IFTs over 15 

dynes/cm, the highest was only 19.5 dynes/cm. Water separation from diesel begins to 

become unpredictable below 25 dynes/cm. In areas where there is not much water in 

fuel, it would probably not be noticed. In areas where there is often water in diesel fuel, 

this could lead to higher injector maintenance costs, over long periods of time, than 

previously experienced using diesel fuels with higher IFT. 

Thus, these results are a serious concern, but there are a number of outstanding questions. 

It is possible that the low IFT is caused by highly polar compounds in the biodiesel 

blends such as the peroxides noted above. Implementation of an oxidation stability 

requirement would in this case be expected to mitigate the problem of low IFT as well. 

Also, it is possible that other types of coalescer media and other types of water removal 

devices could be implemented. This might include the installation of specifically 

designed water separation filters/devices at the fuel dispenser nozzle for separation of 

water prior to pumping into the vehicle fuel tank. 

Percent Biodiesel

0 20 40 60 80 100

Interfacial Tension, dynes/cm

0

2

4

6

8

10

12

14

16

18

20

22

All samples

Nominally B20

Figure 18. Results of water interfacial tension measurements by ASTM 

D971 for B20 survey samples 
33

GM Water Extraction Test 

The General Motors’ (GM) water extraction test is an indirect way of measuring 

potentially corrosive species such as salts, acids, and bases left over from the 

esterification process. In this test, a 400 mL fuel sample is contacted with 40 mL of 

water. The conductivity and pH of the recovered water are measured, as is the amount of 

water recovered. In general, the pH results from this test do not raise any concerns. The 

water recovered varied considerably, with some tests showing that the B20 had dissolved 

as much as 6 volume percent water. This result seems questionable; it is highly unlikely 

that a B20 can hold this amount of water in solution. Figure 19 shows results for water 

conductivity, which varied over a wide range. There is some evidence to suggest that 

high-conductivity values correlate with high-peroxide content, as also shown in Figure 

19. Thus if high-water conductivity is pointing to some fuel quality issue, it may be 

oxidation stability. 
34

Percent Biodiesel

0 20 40 60 80 100

Extracted Water Conductivity, 

uS/cm (GM Test)

0

50

100

150

200

250

All Samples

Nominally B20

Peroxide Number, ppm

0 100 200 300 400

Extracted Water Conductivity, 

uS/cm (GM Test)

0

50

100

150

200

250

All samples

Nominally B20

r

2

=0.6

Figure 19. Conductivity results from the GM water extraction test as a 

function of percent biodiesel (top) and peroxide content (bottom) 

Oxidation Stability by Rancimat 

SwRI and the Robert Bosch Corporation kindly supplied the Rancimat test results. 

Detailed results are presented in Appendix F and are summarized in graphical form here. 

SwRI provided 20 replicate results for a peanut oil standard showing a mean of 5.04 hr, 

standard deviation of 0.22 hr, and 95% confidence interval of +/-0.1 hr. Figure 20 

compares the average SwRI results (3 replications in most cases) and the Bosch results 

(single test). Results for the two labs correlate well, with a correlation coefficient of 
35

0.84. However, there is a bias towards longer induction times for the samples tested at 

Bosch. Bosch indicated some issues with temperature calibration, and these results 

suggest that temperature was slightly low in their tests. Note that SwRI ended the 

experiment at 24 hours for three samples with very long induction times. 

A striking feature of these results is evident from the frequency plot of Figure 21. 

Twenty-one out of the 36 samples tested exhibited induction times of less than 2.5 hr. 

Much longer induction times were anticipated based on the very long times typically 

reported for petroleum-derived diesel fuel, which makes up a large fraction of the 

composition of these samples. The short induction times may have been observed 

because of the age of these samples when tested. The samples were collected in 

September and October of 2004, and most analyses were conducted soon after. However, 

the Rancimat measurements were made in March and April of 2005, roughly 6 months 

later. Although these small samples were stored in an air-conditioned laboratory 

environment in sealed containers, the “oxidation reserve” of these samples may have 

been depleted during this time. It is recommended that for future quality surveys all tests 

should be conducted within one month of sample collection. 

Rancimat IP, hr (SwRI)

0 5 10 15 20 25

Rancimat IP, hr (Bosch)

0

5

10

15

20

25

r

2

=0.84

parity line

Figure 20. Comparison of B20 Rancimat oxidation stability test results from 

SwRI and Bosch 
36

0.6-2.6

2.7-4.6

4.7-6.6

6.7-8.6

8.7-10.6

10.7-12.612.7-14.614.7-16.6

>16.6

Frequency

0

5

10

15

20

25

Figure 21. Frequency distribution for B20 Rancimat stability test results 

(SwRI data) 

B20 Summary and Discussion 

Because no fuel quality specification currently exists for B20, we cannot compare the 

results of this survey to standard requirements. Most of the properties examined showed 

acceptable levels for use in diesel engines. However, the survey data point to a number 

of issues and potential issues. Chief among these is the biodiesel content of the 

supposedly B20 samples. Only 32 out of the 50 samples contained nominally 20% 

biodiesel. The cause of this is believed to be inadequate mixing during splash blending 

of these fuels. This result is being made widely known to the biodiesel industry in hopes 

that education on proper blending procedures can solve this problem. 

Additionally, many of the B20 samples exhibited high levels of peroxides. This is of 

concern because certain vehicle fuel system components are made of materials that may 

not be compatible with peroxides. However, this contention is based on experience with 

gasoline, and the peroxides that form in biodiesel are chemically much different having a 

much higher molecular weight. It is not known if biodiesel peroxides will produce the 

same effects on fuel system materials. Furthermore, it is widely agreed that the B100 

specification, and perhaps the B20 specification, should include an oxidation stability 

requirement. Should such a requirement be implemented it seems highly likely that 

antioxidant additives would be used to meet it resulting in much lower potential for 

peroxide formation. 

The B20 samples exhibited low IFT with water when tested using the ring method. A 

minimum level of IFT is required for the proper performance of water separators that are 
37

used in engine fuel systems to protect the engine from water in the fuel. There are a 

number of potential causes of this problem, including the presence of highly polar 

materials such as peroxides in the biodiesel. Thus, this is another issue that might be 

resolved by implementation of an oxidation stability requirement. 

The B20 samples were tested for oxidation stability by the Rancimat method. Many of 

the samples exhibited induction times of less than 2 hours, however, the samples had 

been stored for on the order of 6 months prior to the oxidation stability measurements. 

Thus it is not clear if the short induction times are intrinsic properties of these samples or 

are caused by the relatively long storage time where the samples capacity to resist 

oxidation was consumed. 

Future surveys of B20 quality should ensure that all tests are conducted within one month 

of sample collection. Additionally, future surveys should include other oxidation 

stability tests such as ASTM D2274. 
38

Conclusions and Recommendations 

Based on the results of the B100 and B20 quality surveys conducted in 2004 the 

following conclusions were drawn: 

 Biodiesel blenders and distributors rely almost entirely on the biodiesel manufacturer 

to ensure fuel quality. Little or no downstream product testing is conducted. 

 The B100 samples included 4 produced from waste oils, 1 produced from tallow, and 

the balance produced from soy. 

 Of the B100 samples collected, 85% met all of the requirements of ASTM D6751. 

 Samples failing one requirement generally exhibited outlier or failing results for a 

second requirement. 

 Distributors were not, at the time of this survey, distinguishing between S15 (15 ppm 

sulfur maximum) and S500 (500 ppm sulfur maximum) grades of biodiesel. 

 Nearly all of the B100 samples exhibited Na+K and Mg+Ca levels below 5 ppm, a 

level thought to be acceptable for protection of fuel injection equipment. 

 A typical U.S. biodiesel exhibits 5 mg/100 ml of deposits on the ASTM D2274 

accelerated stability test and less than 1 hour induction time on the EN14112 

Rancimat oxidation stability test. There is currently no oxidation stability 

specification for diesel fuels in the United States. 

 The main factors affecting the stability of B100 are natural antioxidant content, 

polyunsaturated fatty ester content, and the presence of high levels of mono and diglycerides. 

 An issue with splash blending of B20 blends was identified when it was discovered 

that 18 out of the 50 samples collected were not nominally B20. It is believed that 

insufficient turbulence or splashing occurred during the preparation of these blends. 

 B20 samples showed high levels of peroxides, reinforcing the need for an oxidation 

stability requirement for B100 and perhaps for B20. While peroxide levels were not 

measured for B100, the formation of peroxides is well known as the initial step in fuel 

oxidation. 

 The B20 samples exhibited low levels of water IFT, indicating that water separators 

on engine fuel systems will not perform as intended. The high peroxide levels may 

contribute to the low IFT. 

 A typical B20 showed a less than 2 hour Rancimat (EN14112) induction time, but 

this may have been caused by storing the samples for 6 months prior to testing. 

The following are recommendations based on the results of this study: 

 Additional B100 and B20 surveys should be conducted on an ongoing basis to 

monitor the progress of the industry in meeting fuel quality requirements. 

 A future B20 survey should be conducted in winter to allow an assessment of the 

impact of biodiesel blending on low-temperature properties. 

 For future studies it is important that all analyses be performed within one month of 

sample collection, especially oxidation stability. 

 Understanding of oxidation stability issues would be greatly enhanced by collection 

of field samples that have undergone significant oxidation. 
39

Appendix A: Mono, Di, and Tri-Glyceride Content of 

B100 Samples 

For calculation of total glycerin in ASTM D 6584, the following equation is used: 

total glycerin = free glycerin + bound glycerin 

 (1) 

where: 

bound glycerin = Σ (GlM, GlD, GlT) 

GlM = 0.2591 Σ (monoglyceride, mass %) 

GlD = 0.1488 Σ (diglyceride, mass %) 

GlT = 0.1044 Σ (triglyceride, mass %) 

While Table 7 shows total glycerin reported as mass percent (mass%) glycerin, the test 

method requires measurement of the actual glyceride content. It is instructive to examine 

these numbers, and they are shown in the table below. Samples failing or marginal for 

the total glycerin requirement all exhibit relatively high levels of unconverted 

triglycerides. Triglycerides, or fat, have an extremely high boiling point relative to 

biodiesel or diesel fuel and can lead to the formation of fuel injector tip and other 

combustion chamber deposits. The total amount of unconverted or partially converted 

material in the sample can also be quite high. Sample G exhibits a total glycerin five 

times the allowable level of 0.24 wt% and actually contains more than 7 weight percent 

of unconverted or partially converted material (i.e. this sample is less than 93% 

biodiesel). Sample D is right at the allowable limit and contains slightly more than 1% 

unconverted or partially converted material. 
40

Table 7. Mono, Di, and Tri-Glyceride Content of B100 Samples 

 Free Glycerine Total Glycerin Monoglyceride Diglyceride Triglyceride 

Sample % mass % mass % mass % mass % mass 

A 0.003 0.208 0.624 0.213 0.107 

B 0.002 0.202 0.633 0.166 0.109 

C 0.003 0.147 0.475 0.124 0.027 

D 0.004 0.239 0.597 0.374 0.239 

E 0.003 0.19 0.630 0.143 0.025 

F 0.012 0.019 0.028 0.000 0.000 

G 0.014 1.227 1.837 2.802 3.066 

H 0.004 0.032 0.093 0.027 0.000 

I 0.006 0.023 0.059 0.009 0.000 

J 0.004 0.171 0.563 0.127 0.016 

K 0.003 0.192 0.601 0.168 0.075 

L 0.004 0.037 0.106 0.030 0.005 

N 0.004 0.211 0.596 0.213 0.198 

O 0.003 0.198 0.667 0.135 0.017 

P 0.002 0.011 0.035 0.000 0.000 

Q 0.008 0.067 0.172 0.085 0.014 

R 0.002 0.013 0.039 0.000 0.000 

S 0.006 0.02 0.046 0.014 0.000 

T 0.018 0.317 0.687 0.384 0.608 

U 0.004 0.195 0.641 0.152 0.020 

V 0.009 0.187 0.399 0.292 0.293 

W 0.005 0.025 0.070 0.014 0.000 

X 0.011 0.196 0.603 0.163 0.045 

Y 0.006 0.058 0.196 0.009 0.000 

Z 0.001 0.022 0.077 0.009 0.000 

AA 0.005 0.102 0.357 0.030 0.000 

BB 0.014 0.025 0.043 0.000 0.000 
41

Appendix B: Results of B100 FAME Analysis 

A subset of the biodiesel samples were analyzed by gas chromatography with mass 

spectrometric detection (GC-MS). The instrument used is a Hewlett-Packard HP6890 

GC and includes electronic pressure control. The mass selective detector (MSD) is 

model HP5973 and the automatic liquid sampler is model HP7683. The GC was fitted 

with a Varian capillary column designed for FAME analysis: 100m x 250μm, 0.25μm 

film of ‘CP Select’. Helium was the carrier gas at 1.5 mL/min (constant). The injected 

sample volume was 1μL, and an injection split ratio of 100:1 was used. The 

chromatography conditions were: 

• Initial temp: 150oC for 6 minutes 

• Ramp: 4oC/min 

• Final temp: 250oC for 4 minutes 

• Total run time: 35 minutes. 

The MSD was operated in the electron impact ionization mode, scanning masses from 

33-450 amu. 

The biodiesel samples were all prepared gravimetrically (21-26mg) and then dissolved in 

1.0mL of methanol. FAME standard mixtures from Alltech were prepared in the same 

manner and used to calibrate the GC-MS. These were American Oil Chemists Society 

mixtures 1, 3, 5, and 6. For some species there was only a single point calibration; others 

had two to four levels of concentration between the four standard mixtures. In the latter 

case, we had the choice of using an average response factor, or one that was based on the 

slope of a linear regression of the calibrations. The data reported in Table 8 are based on 

average response factors (or a single response factor when only one was available). All 

compounds used mass 74 for quantitation, except methyl linoleate and methyl linolenate, 

which used masses 67 and 79 respectively. 

Detailed results are shown on the following pages. 
42

Table 8. Results of FAME Analysis by GC-MS for B100 Samples 

 Sample A B F G H K N O R U V 

FAME Name Wt % Wt % Wt % Wt % Wt % Wt % Wt % Wt % Wt % Wt % Wt % C8:0 Methyl Caprylate 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

C10:0 Methyl Caprate 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

C12:0 Methyl Laurate 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

C14:0 Methyl Myristate 0.22 0.00 0.00 0.00 0.09 0.00 0.00 0.00 0.00 0.00 0.62 

C16:0 Methyl Palmitate 12.26 9.37 9.45 9.39 9.36 9.41 9.34 9.33 9.37 9.37 15.86 

C16:1 Methyl Palmitoleate 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.99 

C18:0 Methyl Stearate 5.70 3.55 3.86 3.61 3.84 3.55 3.50 3.56 3.92 3.80 9.11 

C18:1 Methyl Oleate (9) 30.27 19.49 19.45 18.97 19.35 19.57 19.36 19.53 19.53 19.27 34.26 

C18:1 Other Isomers C18:2 Methyl Linoleate (9,12) 47.69 57.35 57.68 58.00 58.41 57.30 57.46 57.33 57.54 57.62 35.32 

C18:3 Methyl Linolenate (6,9,12) 3.28 9.85 9.36 9.63 8.77 9.76 9.97 9.85 9.46 9.51 3.41 

C20:0 Methyl Arachidate 0.32 0.22 0.18 0.20 0.18 0.22 0.18 0.22 0.17 0.24 0.25 

C22:0 Methyl Behenate 0.27 0.18 0.00 0.20 0.00 0.18 0.18 0.18 0.00 0.19 0.19 

C22:1 Methyl Eurcate 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

C24:0 Methyl Lignocerate 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

 Mass Closure % 86.9 104.3 103.3 94.1 101.9 103.3 103.5 104.3 104.7 102.5 75.1 
43

Appendix C: Procedure for Biodiesel Testing Using 

DPPH Redox Indicator 

The procedure was a modification of a published method [3].

A 3.35 .10-4 M solution of 2,2-diphenyl-1-picrylhydrazyl (DPPH, free radical purchased 

from Aldrich Chem. Co) in methanol (HPLC-grade, J.T. Baker) was prepared at room 

temperature. Then 3 mL of this standard solution was placed in a quartz cuvette, a 100 

μL sample of biodiesel was added, and the mixture was stirred vigorously for 1 min. The 

change in absorbance was measured using a UV-VIS apparatus (HP 8453) at a fixed 

λmax= 515 nm over regular time intervals (1, 2, 3, 4, 5, 10, 15, 30, 60 min). A sample of 

pure DPPH/MeOH solution served as ‘blank’ to measure the absorbance at t=0 min. The 

change in absorbance for a randomly selected biodiesel sample (Sample R) was 

arbitrarily assigned a value of 1, and all other samples are referenced to this value for a 

relative antioxidant content. 
44

Appendix D: Additional Modifications to the D2274 Test 

Method 

In the fairly recent past, a number of test methods, which include filtration followed by 

weighing the filter media, have incorporated a “tare” or “blank” filter pad for control 

purposes. The inclusion of the blank filter pad allows changes in atmospheric conditions, 

most noticeably relative humidity, from contributing to overall test variability. This takes 

the form of placing a “blank” filter pad under the experimental pad during the course of 

the filtration procedure. The “blank” pad is dried and weighed in the same manner as the 

experimental pad. Once the weights are determined, the change in the weight of the 

“blank” pad is subtracted from the change in the weight of the experimental pad. The 

logic on which the inclusion of the “blank” pad is based is that the sediment material that 

has a greater diameter than the nominal pore size of the filter pad will be retained on the 

experimental pad, and the sediment that has a diameter less than the pore size will pass 

through both the experimental and “blank” pads. 

This is similar to the inclusion of a “tare” beaker in the determination of adherent 

insolubles. This “tare” beaker is handled exactly like the experimental beakers, except no 

sample is introduced into the beaker. Again, once the weights are determined, the change 

in the weight of the “tare” beaker is subtracted from the change in the weight of the 

experimental beakers. 

This similarity is not exact because the “tare” beaker is never exposed to any of the 

sample, and 100% of the oxidized sample goes through the “blank” filter pad. Therefore 

the only contribution to the “tare” beaker is the changes in atmospheric conditions, 

whereas the exposure of the “blank” pad to the sample provides an additional contributor 

to the change in weight of the pad. The exposure of the “blank” pad to biodiesel has a 

much greater impact on the change in weight of the pad than the changes in atmospheric 

conditions. This is due to the atypical characteristics of the sediment associated with 

biodiesel oxidation. 

As a consequence of recognition that the “blank” pad was retaining additional sediment, 

and thus acting as a second experimental pad, the D2274 data was re-examined. Instead 

of subtracting the change in the weight of the “blank” pad, the change in weight was 

added to the increase in the weight of the experimental pad. The results from this reexamination appear in the following table. 
45

Table 9. D2274 Data with the Control Pad Modification

D2274 Data w/ the Control Pad Modification

Data after Adjustments in Calculations Original Dat

Filter A dher T otal 

AS TM D2274 INSOLUBLES In sol Insol Insol ASTM D2274 INSOLUBLES 

Run Filter. Adher Total Ranges Divided by Avera ges A bs A bs Abs Filter. Adher Total Ranges Divided by 

Spl ID mg/.1 L mg/.1 L mg/.1L Filterable Adheren t Total Range Range R ange mg/.1 L mg/.1 L mg/.1L Filterable Adheren t 

A 1 5.09 0.71 5.80 28% 21% 27% 1.63 0.17 1.80 0.86 0.71 1.57 68% 21% 

2 6.71 0.89 7.60 1.74 0.89 2.63

Avg 5.90 0.80 6.70 1.30 0.80 2.10

B 1 2.54 0.54 3.09 32% 93% 47% 0.97 0.94 1.91 -0.03 0.54 0.51 300% 93% 

2 3.51 1.49 5.00 0.14 1.49 1.63

Avg 3.03 1.01 4.04 0.06 1.01 1.07

C 1 13.49 3.14 16.63 12% 8% 11% 1.57 0.23 1.80 1.83 3.14 4.97 47% 8% 

2 11.91 2.91 14.83 2.94 2.91 5.86

Avg 12.70 3.03 15.73 2.39 3.03 5.41

Z 1 8.37 2.14 10.51 5% 44% 3% 0.43 0.77 0.34 2.77 2.14 4.91 10% 44% 

2 8.80 1.37 10.17 2.51 1.37 3.89

Avg 8.59 1.76 10.34 2.64 1.76 4.40

AA 1 0.46 0.11 0.57 92% 136% 105% 0.77 0.49 1.26 0.06 0.11 0.17 86% 136% 

2 1.23 0.60 1.83 0.14 0.60 0.74

Avg 0.84 0.36 1.20 0.10 0.36 0.46

Averages for the entire sam ple set:

Averages o 12.91 2.47 15.38 27% 28% 26% 3.03 0.54 3.31 2.46 2.47 4.93 54% 28% 
46

The most immediate impact associated with adding the increase in the weight of the 

“blank” pad is the significant increase in the filterable insolubles, the average weight 

increased from 2.46 to 12.91 mg/100mL. This modification had a significant impact on 

the precision of the test. The difference in the two filterable insolubles (the range of the 

values) as a percentage of the average result decreased from 54% to 27%. Of course, 

with the significant increase in the filterable insolubles, there was an associated increase 

in the range of results—an increase from 0.83 to 3.03 mg/100mL. 

There was no change in the adherent insoluble test procedure or results, so this had a 

buffering impact on the changes in the filterable insolubles on the total insolubles results. 

The average increase in total insolubles increased from 4.93 to 15.38 mg/100mL. This 

translated to an improvement in the precision of the overall method, as measured by the 

range of the values as a percentage of the average value, of 6% (from 32% to 26%). 

This improvement in precision did have an appreciable impact on how well the D2274 

data correlated to acid values and the Rancimat data. The correlation coefficients for the 

unmodified D2274 results to the initial acid values, final acid values and the change in 

acid values were 0.13, 0.65, and 0.61, respectively. They improved to 0.25, 0.82 and 

0.76 with the recalculated D2274 values. The correlation of the recalculated D2274 data 

to the Rancimat data improved from -0.66 to -0.72. 

The original D2774 data did not correlate to the D6468 data, and that condition did not 

change; the correlation coefficient went from -0.03 to 0.01. 

D2274 Analysis

Correlations: TI to Init. AV .26, TI to Final AV .82, TI to Change in AV .75

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

A

B

C

D

E

F

H

I

J

K

L

N

O

P

Q

R

S

T

U

V

W

X

Y

Z

AA

Sample ID

mg/100 mL and

 mg KOH/g

Total

Insolubles

Initial Acid

Value

Final Acid

Value

Change in

Acid Values

Figure 22. D2274 analysis 
47

The logical conclusion arising from this improvement in how well the D2274 data 

correlates to the other stability indicators is that if the precision of the D2274 method can 

be further improved, there will be a corresponding improvement in the correlations. A 

cursory evaluation of the data from this perspective suggests that a significant 

opportunity for improvement exists. This conclusion is drawn from an examination of 

the variability of the amount of material that is retained on the control filter pad. If the 

amount of material retained on the control pad is consistently 40% of the total filterable 

insolubles (another way to say that is 67% of the weight of the experimental pad) then no 

opportunity for improvement exists. Even if it is known that a substantial amount of 

insolubles passes through both pads, if that amount is biased by a constant amount, then 

no significant improvement in the correlation will be achieved. 

Both analysts’ observations and the data indicate that significant improvement is 

achievable. The analysts have noted that during some of the filtrations of the oxidized 

biodiesel there is “goo” that passes through the pads and is observed in the filtrate. This 

is not observed in all cases. The increase in weight in the control pad as a percentage of 

the total filterable insolubles varied from 22% to 49% in this data set, with the average 

being 40%. If a dependable means by which the amount of this “filterable insolubles” 

can be quantified, the precision of the test would improve dramatically. At that point, the 

primary source of imprecision would be the ability of the test to generate a consistent 

amount of insolubles in the reaction phase of the test. 
48

Appendix E: Detailed Results for B20 Survey 
49

Sample 

ID 

D2709 Water 

and 

Sediment 

(% vol) 

D4176 

Haze 

Rating 

WLS 102 

Field 

Acid 

Number 

D445 

Kinematic 

Viscosity@ 

40°C (cSt)

MAS001 

Silver 

Strip 

Test 

D3703 

Peroxide 

Number 

(ppm) 

D524 

Carbon 

Residue 

(% mass)

D5773 

Cloud 

Point 

(°F) 

GM 

EXT 

pH 

GM 

EXT 

(μS/cm)

GM EXT 

Water 

Recovered 

(mL) 

D4052 

Density 

(g/mL@

60°F) 

D5

Su

Con

(pp

04070862 NA 1 0.08 2.749 0 35.6 <0.010 4 6.8 51.6 39 0.8571 304070863 NA 1 0.11 3.001 0 27.7 0.017 12 5.5 60.6 40 0.8587 204070864 NA 1 0.06 2.218 0 12.2 <0.010 10 7.2 22.4 37 0.8335 504070865 NA 1 0.14 2.739 0 12.3 0.022 10 7.3 14.5 31 0.8589 204070866 NA 1 0.11 2.838 0 11.3 0.017 4 6.1 42.7 28 0.8632 304070867 NA 1 0.11 2.966 0 46.9 0.021 -6 6.8 56.1 38 0.8497 204070868 NA 1 0.75 2.524 0 12.9 0.018 10 4.4 81.5 33 0.8473 304070869 NA 1 0.08 2.841 0 21.4 0.016 12 7.2 42.8 30 0.8534 204070870 NA 1 0.11 2.154 0 3.8 <0.010 8 5.0 189 38 0.8393 204070871 NA 1 0.03 2.731 0 4.1 0.018 4 6.9 15.2 33 0.8602 204070872 NA 1 0.03 2.774 0 156.0 0.033 2 6.9 57.2 20 0.8610 204070873 NA 1 0.17 2.697 0 199.1 <0.01 14 4.8 115 33 0.8464 904070874 NA 1 0.15 2.603 0 74.9 0.013 -6 5.7 39.7 37 0.8559 104070875 NA 1 0.08 3.330 0 72.3 0.041 4 5.1 53.3 17 0.8683 304070876 NA 1 0.06 2.838 0 33.9 <0.01 10 5.7 27.8 35 0.8593 204070877 NA 1 0.06 3.040 0 241.0 0.018 14 5.5 123 38 0.8621 204070878 Trace 4 0.14 2.739 0 23.5 0.030 2 5.4 24.7 15 0.8560 104070879 NA 1 0.06 2.979 0 67.9 0.016 10 4.6 69.8 30 0.8596 204070880 NA 1 0.06 2.59 0.00 13.0 <0.010 8 6.85 23.4 35 0.8523 104070881 NA 1 0.08 2.900 0 24.0 0.024 -2 6.7 23.3 34 0.8705 304070882 NA 1 0.08 2.745 0 106.1 0.016 8 5.3 150 39 0.8654 304070892 NA 1 0.06 2.684 0 41.8 <0.010 6 7.3 57.3 39 0.8531 204070893 NA 1 0.17 2.299 0 32.5 <0.010 2 6.4 62.5 38 0.8442 104070894 NA 1 0.11 2.857 0 67.6 <0.010 2 5.7 63.4 31 0.8650 204070895 NA 1 0.20 2.945 0 31.3 0.015 16 6.7 19.3 27 0.8542 204070897 NA 1 0.11 3.095 0 29.5 0.015 14 6.2 54.7 39 0.8610 104070898 NA 1 0.06 2.849 0 126.4 <0.01 8 5.1 57.9 40 0.8584 2
50

Sample 

ID 

D2709 Water 

and 

Sediment 

(% vol) 

D4176 

Haze 

Rating 

WLS 102 

Field 

Acid 

Number 

D445 

Kinematic 

Viscosity@ 

40°C (cSt)

MAS001 

Silver 

Strip 

Test 

D3703 

Peroxide 

Number 

(ppm) 

D524 

Carbon 

Residue 

(% mass)

D5773 

Cloud 

Point 

(°F) 

GM 

EXT 

pH 

GM 

EXT 

(μS/cm)

GM EXT 

Water 

Recovered 

(mL) 

D4052 

Density 

(g/mL@

60°F) 

D5

Su

Con

(pp

04070910 NA 1 0.11 3.629 0 16.4 <0.01 42 6.4 25.8 39 0.8359 104070911 NA 1 0.06 2.852 0 47.9 0.103 10 7.3 45.2 26 0.8572 204070912 NA 1 0.11 2.750 0 8.5 0.018 -2 6.9 42.0 33 0.8654 204070913 NA 1 0.14 2.161 0 16.1 <0.010 4 6.1 42.3 40 0.8366 204070914 NA 1 0.28 2.666 0 43.6 0.013 8 5.7 69.2 17 0.8570 204070915 NA 1 0.16 2.491 0 22.4 <0.010 34 6.9 24.6 34 0.8422 04070917 NA 1 0.06 2.547 0 39.0 <0.010 6 6.8 19.1 33 0.8424 04070918 NA 1 0.03 3.042 0 145.6 0.033 12 7.3 32.5 28 0.8688 204070919 NA 1 0.06 2.798 0 1.1 <0.010 8 7.4 28.8 35 0.8598 104070920 NA 1 0.06 3.080 0 76.7 0.016 12 6.6 57.1 33 0.8655 204070921 NA 1 0.11 2.713 0 48.7 <0.010 8 6.6 45.8 33 0.8487 404070922 NA 1 0.06 2.808 0 87.1 0.041 8 4.5 105 39 0.8610 204070923 NA 1 0.08 2.957 0 334.2 0.016 10 4.6 158 40 0.8572 204070960 NA 1 0.11 2.985 0 <1.0 <0.010 10 6.6 45.5 39 0.8637 204070961 NA 1 0.14 2.841 0 <1.0 0.021 12 5.9 48.7 30 0.8632 N04070963 NA 1 0.22 2.882 0 3.1 <0.01 14 7.6 40.7 26 0.8570 204071007 NA 1 0.19 2.883 0 39.1 0.031 8 6.0 22.3 39 0.8662 204071046 NA 1 0.06 2.474 0 203.4 <0.010 2 4.9 106 40 0.8535 104071052 NA 1 0.28 2.308 0 <1.0 0.015 12 7.1 45.3 40 0.8622 N04071072 NA 1 0.68 2.697 0 29.0 0.014 20 4.4 60.7 24 0.8665 104071073 NA 1 0.03 3.126 0 73.7 <0.010 14 7.3 21.1 39 0.8706 104071074 NA 1 0.34 3.568 0 46.9 <0.010 28 5.8 96.0 38 0.8627 104080015 NA 1 0.08 4.113 0 141.4 <0.010 32 6.3 128 35 0.8842 104080628 NA 1 0.42 4.858 0 55.1 0.024 40 3.9 215 35 0.8801 
51

Appendix F: B20 Rancimat Results 

Table 10. Rancimat Induction Time, Hours 

 SwRI Replications SwRI Bosch 

SAMPLE 

ID 

1 2 3 AVG

B20R1 1.16 1.16 1.11 1.14 1.0 

B20R2 >24 >24 >24 >24 - 

B20R3 2.51 2.77 2.83 2.70 3.5 

B20R4 16.13 16.03 17.46 16.54 20.3 

B20R5 1.34 1.56 1.78 1.56 1.6 

B20R6 0.6 0.73 0.66 0.66 0.9 

B20R7 >24 >24 >24 >24 29.8 

B20R8 1.03 1.63 0.52 1.06 1.4 

B20R9 4.72 4.3 4.72 4.58 6.9 

B20R10 3.45 4.84 4.93 4.41 5.9 

B20R11 1.30 2.43 1.17 1.63 1.4 

B20R12 4.62 2.81 2.90 3.44 7.7 

B20R13 1.90 2.39 2.71 2.33 4.2 

B20R14 0.68 0.69 0.73 0.70 1.3 

B20R15 0.89 0.80 0.95 0.88 1.2 

B20R16 2.65 3.10 2.65 2.80 3.9 

B20R17 1.26 0.97 0.87 1.03 1.3 

B20R18 5.83 5.55 5.17 5.52 7.0 

B20R19 0.17 0.47 1.26 0.63 1.0 

B20R20 1.35 0.67 1.19 1.07 1.3 

B20R21 1.46 1.90 1.88 1.75 3.2 

B20R22 0.90 0.79 0.85 1.5 

B20R23 1.93 1.85 1.89 4.2 

B20R24 4.84 5.86 7.23 5.98 16.8 

B20R25 >24 12.88 >24 >24 9.8 

B20R26 1.76 1.88 1.94 1.86 2.6 

B20R27 0.57 0.53 0.79 0.63 1.1 

B20R28 1.98 1.99 1.39 1.79 2.1 

B20R29 1.72 1.7 1.6 1.67 2.7 

B20R30 2.11 2.14 2.06 2.10 2.2 

B20R31 6.55 6.26 6.86 6.56 12.4 

B20R32 4.58 4.41 4.04 4.34 4.8 

B20R33 1.68 1.64 1.64 1.65 2.1 

B20R34 4.56 4.79 4.59 4.65 5.8 

B20R35 0.88 1.51 1.41 1.46 1.6 

B20R36 5.52 6.38 6.51 6.14 11.3 
52

References 

 

1. United States Department of Energy, Energy Information Agency, 

http://www.eia.doe.gov/cneaf/alternate/page/datatables/afvtable10_03.xls. Accessed May 

12, 2005. 

2. Knothe, G.; Dunn R.O. “Dependence of Oil Stability Index of Fatty Compounds on 

Their Structure and Concentration and Presence of Metals.” Journal of the American Oil 

Chemists’ Society; Vol. 80, 2003; p. 1021. 

3. Brand-Williams, W.; Cuvelier, M.E.; Berset, C. “Use of a Free-Radical Method to 

Evaluate Antioxidant Activity.” Food Science Technology - Lebensm.-Wiss; Vol. 28, 

1995; p. 25. 

4. deMan, J.M.; Tie, F.; deMan, L. “Formation of Short Chain Volatile Organic Acids in 

the Automated AOM Method.” Journal of the American Oil Chemists’ Society; Vol. 64, 

1987; p. 1993. 

5. European Committee for Standardization. EN 14214: Automotive Fuels — Fatty Acid 

Methyl Esters (FAME) for Diesel Engines — Requirements and Test Methods. 2003.

6. Westbrook, S. An Evaluation and Comparison of Test Methods to Measure the 

Oxidation Stability of Neat Biodiesel: Final Report. NREL/SR-540-38983. Work 

performed by Southwest Research Institute. Golden, CO: National Renewable Energy 

Laboratory, October 2005. 

7. Neff, W. E.; Selke, E.; Mounts, T. L.; Rinsch, E. N.; Zeitoun, M. A. M. “Effect of 

Triacylglycerol Composition and Structures on Oxidative Germoplasm.” Journal of the 

American Oil Chemists’ Society ; Vol. 69, 1992; p. 111. 

8. Cosgrove, J. P.; Church, D. F.; Pryor, W. A. “The Kinetics of the Autoxidation of 

Polyunsaturated Fatty Acids.” Lipids; Vol. 22., 1987; p. 299. 

9. Westbrook, S.R.; Stavinoha, L.L. “Biodiesel and B20 Blends: Stability Test Methods 

and Stability Characteristics,” IASH 2003, the 8th International Conference on Stability 

and Handling of Liquid Fuels, Steamboat Springs, Colorado, September 14-19, 2003. 

10. Lawrence, R. Results on biodiesel stability presented at the Biodiesel Technical 

Workshop, New Orleans, January 2003. 
F1147-E(12/2004) 

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Survey of the Quality and Stability of Biodiesel and Biodiesel Blends 

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This document reports results gathered from quality surveys in 2004 of biodiesel (B100) and 20 percent biodiesel 

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