National Renewable Energy Laboratory 

Innovation for Our Energy Future 

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

Office of Energy Efficiency & Renewable Energy

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

Stability of Biodiesel and 

Biodiesel Blends: Interim Report 

R.L. McCormick and T.L. Alleman 

National Renewable Energy Laboratory 

J.A. Waynick and S.R. Westbrook 

Southwest Research Institute 

S. Porter 

Marc-IV Consulting 

Technical Report 

NREL/TP-540-39721 

April 2006 
Stability of Biodiesel and 

Biodiesel Blends: Interim Report 

R.L. McCormick and T.L. Alleman 

National Renewable Energy Laboratory 

J.A. Waynick and S.R. Westbrook 

Southwest Research Institute 

S. Porter 

Marc-IV Consulting 

Prepared under Task No. FC06.9400 

Technical Report 

NREL/TP-540-39721 

April 2006 

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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Table of Contents 

List of Tables..................................................................................................................... iv 

List of Figures.................................................................................................................... iv 

Acronyms and Abbreviations ............................................................................................ iv 

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

Introduction......................................................................................................................... 2 

Experimental Methods........................................................................................................ 3 

B100 and Diesel Samples ............................................................................................... 3 

B100 Stability ................................................................................................................. 3 

Results................................................................................................................................. 5 

B100 Samples ................................................................................................................. 5 

B100 Antioxidant Testing............................................................................................. 10 

Diesel Fuel Samples...................................................................................................... 13 

Discussion and Recommendations ................................................................................... 15 

Appendix: Oxidation Stability Test Data......................................................................... 16 

iii
List of Tables 

Table 1. Biodiesel Samples Obtained and Preliminary Characterization........................... 5 

Table 2. Results of ASTM D6468 Performed at 150°C/180 Minutes/350 ml Sample Size 

with Gravimetric Determination of Deposits...................................................................... 9 

Table 3. Results of Accelerated Stability Tests for Biodiesel Treated with Antioxidant 

Additives........................................................................................................................... 10 

Table 4. Characterization Results for Petroleum Diesel

Samples to be Used in Preparation of B5 and B20 Blends............................................... 14 

Table 5. B100 Samples Selected for Long-Term Storage and Blending Studies............. 15 

List of Figures 

Figure 1. Histogram for B100 Rancimat induction time .................................................... 6 

Figure 2. Histogram for B100 ASTM D525 induction time............................................... 7 

Figure 3. Relationship between Rancimat and ASTM D525 results (Circled data points 

indicate that no oxidation was observed after 780 minutes and the results are simply 

plotted as 780 minutes.)...................................................................................................... 7 

Figure 4. Histogram for B100 ASTM D2274 total insolubles............................................ 8 

Figure 5. Histogram for B100 ASTM D2274 iso-octane insolubles................................. 8 

Figure 6. Histogram for B100 ASTM D2274 acid value................................................... 9 

Figure 7. Additive response curves for unstable biodiesel AL-27138-F.......................... 11 

Figure 8. Additive response curves for moderately stable biodiesel AL-27129-F........... 12 

Acronyms and Abbreviations 

ASTM American Society for Testing and Materials 

B100 100% biodiesel 

B20 20% biodiesel, 80% petrodiesel 

B5 5% biodiesel, 95% petrodiesel 

FAME fatty acid methyl esters 

mg KOH/g milligrams of potassium hydroxide per gram 

mg milligram 

ml milliliter 

NREL National Renewable Energy Laboratory 

ppm parts per million 

ULSD Ultra-low sulfur diesel (petrodiesel having 15 ppm or less sulfur) 

iv
Executive Summary 

In support of the U.S. Department of Energy, Fuels Technologies Program Multiyear Program 

Plan Goal of identifying fuels that can displace 5% of petroleum diesel by 2010, the National 

Renewable Energy Laboratory is performing a study of biodiesel oxidative stability. The 

objective of this work is to develop a database that supports specific proposals for a stability test 

and a specification for biodiesel and biodiesel blends. The overall study includes the following 

steps: 

1. Collection of 19 B100 samples and six diesel samples 

2. Preliminary B100 characterization and measurement of B100 stability using accelerated 

tests 

3. Down selection from 19 B100 samples to eight that cover the range of stability observed 

in accelerated tests and the range of feedstocks 

4. Preparation of B5 and B20 blends from all eight biodiesel fuels and all six diesel fuels 

5. Measurement of the stability of the B5 and B20 blends using accelerated tests 

6. Down selection from 48 B5 and 48 B20 blends to eight of each blend 

7. Testing of the eight B100 samples for stability in a simulated storage environment for 12 

weeks 

8. Testing of the eight B5 and eight B20 blends for stability in a simulated storage 

environment for 12 weeks, and in a simulated vehicle fuel tank for 1 week followed by 

high-temperature stability testing 

9. Selection of two B100 and two diesel fuels for tests of antioxidant additives in all testing 

scenarios. 

This interim report describes characterization and accelerated stability test results for the 19 B100 

samples and six diesel fuels obtained. The B100 samples underwent an initial characterization 

for acid value as well as free and total glycerin content. The samples were then tested for 

stability using the following accelerated stability test methods: 

• Rancimat (EN14112) 

• Stability (modified ASTM D2274, including measurement of iso-octane insolubles) 

• Stability (modified ASTM D6468 150°C for 180 minutes, 350 ml sample, gravimetric 

deposit determination) 

• Stability (ASTM D525). 

Based on the results of these tests, eight samples were selected for a more detailed study and for 

studies as B5 and B20 blends (see Table 5 on page 15). 

Two B100 samples were treated with two commercial antioxidants at different treatment levels 

and characterized by accelerated stability tests. Both antioxidants were effective for increasing 

induction time and reducing deposit formation. 

Five ultra-low sulfur diesel (<15 ppm S) and one low-sulfur diesel (<500 ppm S) were also 

obtained for use in preparing B5 and B20 blends. These were characterized for aromatic content 

because of its potential impact on the solubility of oxidized biodiesel, as well as other properties.

1
Introduction 

In support of the U.S. Department of Energy, Fuels Technologies Program Multiyear 

Program Plan Goal of identifying fuels that can displace 5% of petroleum diesel by 2010, 

the National Renewable Energy Laboratory (NREL) is performing a study of biodiesel 

oxidation stability. The objective of this work is to develop a database that supports 

specific proposals for a stability test and specification for biodiesel and biodiesel blends. 

The overall study includes the following steps: 

1. Collection of 19 B100 samples and six diesel samples 

2. Preliminary B100 characterization and measurement of B100 stability using 

accelerated tests 

3. Down selection from 19 B100 samples to eight based that cover the range of 

stability observed in accelerated tests and the range of feedstocks 

4. Preparation of B5 and B20 blends from all eight biodiesel fuels and all six diesel 

fuels 

5. Measurement of the stability of the B5 and B20 blends using accelerated tests 

6. Down selection from 48 B5 and 48 B20 blends to eight of each blend 

7. Testing of the eight B100 samples for stability in a simulated storage environment 

for 12 weeks 

8. Testing of the eight B5 and eight B20 blends for stability in a simulated storage 

environment for 12 weeks, and in a simulated vehicle fuel tank for 1 week 

followed by high temperature stability testing 

9. Selection of two B100 and two diesel fuels for tests of antioxidant additives in all 

testing scenarios. 

The total data set will be analyzed to determine if any of the accelerated tests are able to 

predict storage stability for B100, along with the effects of antioxidants. The accelerated 

stability test results for the B100 samples will also be used in conjunction with the 

biodiesel blend stability data to determine if a B100 stability specification can ensure the 

stability of blends. If not, the accelerated stability test results for the blends will be 

assessed to determine if they can predict stability on any of the longer-term tests. 

This interim report describes characterization and accelerated stability test results for the 

19 B100 samples and six diesel fuels obtained. 

2
Experimental Methods 

B100 and Diesel Samples 

A single drum of B100 was obtained from 14 biodiesel production sites in the United 

States and two more from Canadian production facilities. Additionally, three drums of 

European rapeseed derived biodiesel were obtained. The B100 drums were nitrogen 

purged/blanketed and stored in a dark room at room temperature. The samples were 

tested for acid value (ASTM D664), and for free and total glycerin (ASTM D6584) 

shortly after receipt. Detailed characterization will only be performed on a subset of 

these fuels that is selected for more detailed testing. 

In addition, six samples (two drums each) of petroleum-derived diesel fuel were obtained 

from petroleum refiners in the United States and Canada. These include one 500 ppm 

sulfur fuel, and five others meeting the 15 ppm sulfur limit [ultra-low sulfur diesel 

(ULSD)]. The diesel fuels have been characterized using the following tests: 

• Total particulate contamination, ASTM D6217 

• Flash point, ASTM D93 

• Sulfur, ASTM D5453 

• T90/Carbon Residue, ASTM D86/D524 

• Acid Number, ASTM D664 

• Peroxide Number, ASTM D3703 

• Ash Content, ASTM D482 

• SFC Aromatics, ASTM D5186 

• Oxidation Stability, ASTM D2274 with additional measurement of iso-octane 

insolubles 

• Thermal Stability, ASTM D6468 (150oC, 180 minutes). 

B100 Stability 

All B100 samples were tested using the following accelerated stability tests: 

EN14112: Fatty Acid Methyl Esters (FAME) – Determination of oxidation 

stability (accelerated oxidation test). EN14112 was run using the Rancimat 

apparatus. 

ASTM D525: Standard Test Method for Oxidation Stability of Gasoline 

(Induction Period Method). D525 is a gasoline stability test method measuring an 

induction time for the start of oxygen consumption. This test was shown in a 

recent study1

 to correlate well with Rancimat, but may provide better 

discrimination between fuels with short Rancimat induction times. 

 

1

 Miyata, I.; Takei, Y; Tsurutani, K.; Okada, M. “Effects of Bio-Fuels on Vehicle Performance: 

Degradation Mechanism Analysis of Bio-Fuels,” SAE Technical Paper No. 2004-01-3031 (2004). 

3
ASTM D2274: Standard Test Method for Oxidation Stability of Distillate Fuel 

Oil (Accelerated Method). D2274 is modified to use glass fiber filters and to 

include iso-octane insolubles and acid value. 

 

ASTM D6468: Standard Test Method for High-Temperature Stability of Distillate 

Fuels. This test was run at 150°C for 180 minutes and modified to utilize 350 ml 

sample size and the same gravimetric insolubles procedures used for D2274. 

4
Results 

B100 Samples 

Table 1 lists the 19 B100 samples obtained, their feedstock, and preliminary 

characterization results. These samples appear to cover the full range of feedstocks 

currently used in North America. Two samples failed the ASTM D6751 specification for 

biodiesel: one due to high acid value and a second due to high total glycerin. While these 

samples are included in the accelerated stability tests, they will not be considered for 

down selection and blending because of their poor quality. The samples that are down 

selected will be characterized much more extensively. 

Table 1. Biodiesel Samples Obtained and Preliminary Characterization 

Sample 

Identification 

Feedstock Total Acid 

Number, mg 

KOH/g 

Total Glycerin, 

%(mass) 

Free Glycerin, 

%(mass) 

ASTM D664 ASTM D6584 ASTM D6584 

ASTM D6751-03a Limit: 0.80 0.24 0.02 

AL-27128-F Canola 0.23 0.103 0.009 

AL-27129-F Palm Stearin 0.41 0.081 <0.001 

AL-27137-F Soy 0.05 0.144 0.002 

AL-27138-F Soy 0.33 0.016 0.002 

AL-27140-F Soy 0.20 0.022 0.015 

AL-27141-F Soy 0.13 0.121 0.005 

AL-27142-F Soy 0.07 0.216 0.003 

AL-27144-F Soy 0.39 0.221 0.004 

AL-27145-F Soy 0.49 0.192 0.005 

AL-27146-F Rapeseed 0.08 0.161 <0.001 

AL-27148-F Grease 0.69 0.121 <0.001 

AL-27152-F Rapeseed 0.09 0.15 0.001 

AL-27153-F Rapeseed 0.08 0.15 0.001 

AL-27154-F Grease 1.31 0.132 0.003 

AL-27155-F Soy 0.29 0.298 0.007 

AL-27157-F Soy 0.11 0.225 0.015 

AL-27158-F Soy 0.51 0.158 0.001 

AL-27160-F Tallow 0.46 0.188 0.002 

AL-27161-F Grease 0.37 0.151 0.003 

Oxidation stability data for the 19 B100 samples are tabulated in the Appendix. Figure 1 

shows a frequency plot for Rancimat induction time measured for these 19 samples. The 

samples show a broad distribution with results ranging from less than 1 to over 9 hours. 

Figure 2 shows a frequency plot for ASTM D525 induction time, which also reveals a 

wide range of values. We anticipated that these tests would be somewhat correlated with 

one another, and this relationship is shown in Figure 3. The circled data points indicate 

5
that no oxidation was observed after 780 minutes, and the results are simply plotted as 

780 minutes. Figure 3 indicates only an approximate correlation between these methods 

(r2

 of 0.4). 

Figures 4 through 6 show results for the ASTM D2274 deposit test. Ten out of the 19 

samples tested show deposits of less than 2 mg/100 ml; deposits for the other nine fuels 

cover the range up to nearly 18 mg/100 ml. The filtrate from this test was also mixed 

with iso-octane to precipitate materials that are insoluble in non-polar solvents. Fourteen 

of the samples exhibited less than 20 mg/100 ml, with the balance ranging up to 200 

mg/100 ml. Finally, the acid value of the filtered liquid was also measured and ranged 

from less than 1 to over 5 mg KOH/g. 

Table 2 lists results for the ASTM D6468 thermal stability test modified for gravimetric 

measurement of deposits. All samples produced low levels of deposits, and there is little 

discrimination among the samples. 

Rancimat Induction Time, hr

0 1 2 3 4 5 6 7 8 9 10

Count

0

1

2

3

4

5

6

Figure 1. Histogram for B100 Rancimat induction time 

6
ASTM D525 Induction Time, min

0 200 400 600 800

Count

0

1

2

3

4

5

Figure 2. Histogram for B100 ASTM D525 induction time 

Col 4 vs Col 5 

Rancimat Induction Time, hr

02468 10

ASTM D525 Induction Time, min

0

200

400

600

800

1000

Figure 3. Relationship between Rancimat and ASTM D525 results (Circled data 

points indicate that no oxidation was observed after 780 minutes, and the results are 

simply plotted as 780 minutes.) 

7
ASTM D2274 Total Insolubles, mg/100 ml

0 2 4 6 8 10 12 14 16 18 20

Count

0

2

4

6

8

10

12

Figure 4. Histogram for B100 ASTM D2274 total insolubles 

ASTM D2274 Iso-Octane Insolubles, mg/100 ml

0 50 100 150 200

Count

0

2

4

6

8

10

12

14

16

Figure 5. Histogram for B100 ASTM D2274 iso-octane insolubles 

8
Count 3 

ASTM D2274 Acid Value, mg KOH/g

0123456

Count

0

1

2

3

4

5

6

7

Figure 6. Histogram for B100 ASTM D2274 acid value 

Table 2. Results of ASTM D6468 Performed at 150°C/180 Minutes/350 ml Sample 

Size with Gravimetric Determination of Deposits 

Sample Identification ASTM D6468 Modified 

 Thermal Stability, deposit, mg 

AL-27128-F 0.3 

AL-27129-F 0.1 

AL-27137-F 0.3 

AL-27138-F 0.3 

AL-27140-F 0.4 

AL-27141-F 0.2 

AL-27142-F 0.3 

AL-27144-F 0.4 

AL-27145-F 0.4 

AL-27146-F 0.5 

AL-27148-F 0.4 

AL-27152-F 0.1 

AL-27153-F 0.5 

AL-27154-F 0.1 

AL-27155-F 0.3 

AL-27157-F 0.3 

AL-27158-F 0.6 

AL-27160-F 0.5 

AL-27161-F 0.2 

9
B100 Antioxidant Testing 

Biodiesel sample AL-27129-F and AL-27138-F were treated with two commercial 

antioxidants. Antioxidant treat rates as well as Rancimat induction times and total 

insolubles from ASTM D2274 are given in Table 3. Both additives are highly effective 

at increasing Rancimat induction time and reducing insoluble formation for these 

samples. The biodiesel fuels were selected to represent unstable fuel (AL-27138-F) with 

Rancimat of 0.45 hr and moderately stable fuel (AL-27129-F) with Rancimat of 3.11 hr. 

Additive response curves for the unstable biodiesel fuel are shown in Figure 7. For 

increasing induction time, additive A seems to be more effective; while for reducing total 

deposits, additive B may be slightly more effective. Both additives were effective for 

reducing iso-octane insoluble formation. For the moderately stable curve only one treat 

rate was tested for each additive, and results are shown in Figure 8. In this fuel, additive 

A is also more effective at increasing induction time. For insoluble formation these data 

are not sufficient to distinguish between the additives, but both are effective. 

These biodiesel samples are currently being tested using ASTM D4625—the 12-week, 

storage-stability test. In addition, B5 and B20 blends are being prepared using two of the 

ULSD fuels, and these will also be subjected to accelerated stability tests and real-world 

aging simulations. 

Table 3. Results of Accelerated Stability Tests for Biodiesel Treated with 

Antioxidant Additives 

Sample 

Number Description 

Rancimat 

Induction 

Time 

ASTM D2274 

Total 

Insoluble 

i-Octane 

Insoluble 

Acid Value 

hr mg/100 ml mg/100 ml mg KOH/g 

AL-27138 with no additive 0.45 7.6 4.4 3.01 

06-0077 AL-27138 plus 1000 ppm additive A 3.18 6.5 1.0 2.35 

06-0078 AL-27138 plus 2000 ppm additive A 5.73 0.3 1.6 0.40 

06-0079 AL-27138 plus 1000 ppm additive B 1.67 3.0 0.6 2.49 

06-0080 AL-27138 plus 2000 ppm additive B 2.64 0.8 0.3 1.28 

AL-27129 with no additive 3.11 1.9 2.6 2.50 

06-0081 AL-27129 plus 1000 ppm additive A 22.82 0.1 0.5 0.45 

06-0082 AL-27129 plus 1000 ppm additive B 6.87 0.2 0.1 0.47 

10
Additive Treat Rate, ppm

0 500 1000 1500 2000 2500

Rancimat Induction Time, hr

0

1

2

3

4

5

6

Additive A

Additive B

Fuel AL-27138-F

Additive Treat Rate, ppm

0 500 1000 1500 2000 2500

ASTM D2274 Insoluble, mg/100 ml

0

2

4

6

8

Additive A -Total Insoluble

Additive A - iso-Octane Insoluble

Additive B - Total Insoluble

Additve B - iso-Octane Insoluble

Fuel AL-27138-F

Figure 7. Additive response curves for unstable biodiesel AL-27138-F 

11
12

Additive Treat Rate, ppm

0 200 400 600 800 1000 1200

Rancimat Induction Time, hr

0

5

10

15

20

25

Additive A

Additive B

Fuel AL-27129-F

Additive Treat Rate, ppm

0 200 400 600 800 1000 1200

ASTM D2274 Insoluble, mg/100 ml

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Additive A - Total Insoluble

Additive A - iso-Octane Insoluble

Additive B - Total Insoluble

Additive B - iso-Octane Insoluble

Fuel AL-27129-F

Figure 8. Additive response curves for moderately stable biodiesel AL-27129-F 
13

Diesel Fuel Samples 

Characterization results for the six diesel fuel samples are shown in Table 4. Five are 

ULSD, and one is a current on-road diesel fuel. Based on the distillation T90, samples 

AL2715F, AL27166F, and AL27176F are No. 1 diesel fuels; the others are No. 2 diesel 

fuels. Aromatic content is regarded as an important parameter for this study because 

fuels with higher aromatic content may be able to more readily solvate oxidized biodiesel 

molecules, which would otherwise precipitate as deposits in fuels with lower aromatic 

content. Total aromatics for the ULSD samples range from 8.2 to 22.1 mass percent. 

There is great uncertainty as to exactly what commercial ULSD will look like when 

introduced in October 2006. Thus, these ULSD fuels might not be representative of 

commercial ULSD. However, these are the ULSD fuels that the petroleum refining 

industry supplied to NREL in December 2005. All samples exhibited good stability on 

both D2274 and D6468.
14

Table 4. Characterization Results for Petroleum Diesel 

Samples to be Used in Preparation of B5 and B20 Blends 

Sample: ASTM D975

Limit (No. 2 

Diesel) 

AL27150F AL27151F AL27166F AL27171F AL

ASTM D93 Flash Point, oC 52 56 69 59 73 ASTM D5453 Sulfur, ppm 15 or 500 7.4 6.7 5.8 339.6 ASTM D86 T90, oC 282 min 

338 max 

274 313 269 319 

ASTM D524 Carbon Residue (10%), mass% 0.35 0.07 0.04 0.06 0.13 ASTM D664 Acid Number, mg KOH/g none 0.01 0.03 0.01 0.01 ASTM D3703 Peroxide Number none <1 <1 <1 <1 ASTM D2709 Water and Sediment, vol% 0.05 0.01 0.01 0.01 0.01 ASTM D482 Ash Content, mass% 0.01 <0.001 <0.001 <0.001 <0.001 ASTM D5186 Total Aromatics, mass% none 15.7 22.1 18.1 36.2 

Monoaromatics, mass% none 14.4 19.9 17.1 27.6 Polynuclear Aromatics, mass% none 1.3 2.1 1 8.7 

ASTM D2274 Total Insolubles, mg/100 ml none 0.25 0.25 0.5 0.2 ASTM D6468 Thermal Stability, 150oC/180 min 

% Reflectance 

none 100 100 100 -- 

ASTM D6217 Particulate Contamination, mg/L none 0.5 0.4 0.8 0.8 
15

Discussion and Recommendations 

There are 19 B100 samples, and our intent is to select eight for long-term storage tests 

(D4625 for 12 weeks) and for preparation of B5 and B20 blends. The down selection 

was based on covering the full range (high, medium, low) of values for each of the 

accelerated tests (see Appendix) and to include the full range of feedstocks. However, 

results for D6468 showed low levels of deposits (gravimetric) for all samples, so that test 

is not considered here. Additionally, the two B100 samples—which were out of spec for 

either acid value or total glycerin—are not considered further. The samples selected are 

shown in Table 5. Obviously some compromises were made to meet all of the study 

objectives, including covering all feedstocks. If questions arise at a later date, other 

samples can be added to the test matrix. 

Table 5. B100 Samples Selected for Long-Term Storage and Blending Studies 

Feedstock Rancimat D525 D2274 Total D2274 i-Octane 

Observed 

Range: 

0.2 – 9.4 hr 34 - >780 min 0.3 – 17.6 

mg/100 ml 

0.2 – 198 

mg/100 ml 

AL-27128-F Canola 4.2 (med) 341 (med) 6.5 (med) 198 (high) 

AL-27129-F Palm Stearin 3.1 (med) 169 (med) 1.9 (low) 2.6 (low) 

AL-27137-F Soy 6.5 (high) retesting 1.0 (low) 2.6 (low) 

AL-27138-F Soy 0.5 (low) 80 (low) 7.6 (med) 4.4 (low) 

AL-27141-F Soy 5.5 (high) 335 (med) 0.3 (low) 0.6 (low) 

AL-27148-F Grease 7.8 (high) 325 (med) 0.9 (low) 19 (med) 

AL-27152-F Rapeseed 7.3 (high) 418 (med) 0.5 (low) 6.4 (low) 

AL-27160-F Tallow 0.2 (low) 159 (low) 17.6 (high) 124 (high) 
Appendix: Oxidation Stability Test Data 

Sample Identification Method AL-27128-F AL-27129-F AL-27137-F AL-27138-F AOxidation Stability, hours EN 14112 Replicate 1 4.22 3.09 6.41 0.13  Replicate 2 4.18 3.10 6.55 0.62  Replicate 3 4.24 3.14 6.61 0.59  Mean 4.21 3.11 6.52 0.45 Oxidation Stability, mg/ 100 ml Modified ASTM D2274 

Replicate 1

 Filterable insolubles 4.7 1.3 0.7 6.1  Adherent Insolubles 1.6 1.0 1.1 0.9  Total Insolubles 6.3 2.3 1.8 7.0  Iso-Octane Insolubles 197.4 4.7 2.4 4.0 

Replicate 2

 Filterable insolubles 5.0 1.0 0.2 6.9  Adherent Insolubles 1.6 0.5 0.0 1.3  Total Insolubles 6.6 1.5 0.2 8.2  Iso-Octane Insolubles 198.0 0.4 2.8 4.8 Mean Total Insolubles 6.5 1.9 1.0 7.6 Mean Iso-Octane Insolubles 197.7 2.6 2.6 4.4 Oxidation Stability, Pressure Vessel ASTM D525 Induction Period Method, minutes 341 169 34 80 Thermal Stability, deposit, mg ASTM D6468 Modified 0.3 0.1 0.3 0.3 Total Acid Number, mg KOH/g ASTM D664 0.23 0.41 0.05 0.33 Total Acid Number after D2274, mg KOH/g  Replicate 1 1.84 2.92 0.24 2.75  Replicate 2 2.03 2.07 0.15 3.26  Mean 1.94 2.50 0.20 3.01 Total Glycerin, %(mass) ASTM D6584 0.103 0.081 0.144 0.016 Free Glycerin, %(mass) ASTM D6584 0.009 <0.001 0.002 0.002 

16
Sample Identification Method AL-27142-F AL-27144-F AL-27145-F AL-27146-F A

Oxidation Stability, hours EN 14112 Replicate 1 4.56 3.69 3.70 9.28  Replicate 2 4.46 4.02 4.01 9.33  Replicate 3 4.40 4.10 4.16 9.16  Mean 4.47 3.94 3.96 9.26 Oxidation Stability, mg/ 100 ml Modified ASTM D2274 

Replicate 1

 Filterable insolubles 0.9 2.0 2.0 0.3  Adherent Insolubles 0.2 0.3 0.4 0.1  Total Insolubles 1.1 2.3 2.4 0.4  Iso-Octane Insolubles 0.3 1.4 2.7 0.4 

Replicate 2

 Filterable insolubles 0.9 2.2 2.0 0.2  Adherent Insolubles 0.2 0.1 0.2 0.0  Total Insolubles 1.1 2.3 2.2 0.2  Iso-Octane Insolubles 0.7 1.3 0.7 0.4 Mean Total Insolubles 1.1 2.3 2.3 0.3 Mean Iso-Octane Insolubles 0.5 1.4 1.7 0.4 Oxidation Stability, Pressure Vessel ASTM D525 Induction Period Method, minutes 507 62 721 649 Thermal Stability, deposit, mg ASTM D6468 Modified 0.3 0.4 0.4 0.5 Total Acid Number, mg KOH/g ASTM D664 0.07 0.39 0.49 0.08 Total Acid Number after D2274, mg KOH/g  Replicate 1 1.11 1.91 2.18 0.19  Replicate 2 0.90 1.83 2.13 0.20  Mean 1.01 1.87 2.16 0.20 Total Glycerin, %(mass) ASTM D6584 0.216 0.221 0.192 0.161 Free Glycerin, %(mass) ASTM D6584 0.003 0.004 0.005 <0.001 

17
Sample Identification Method AL-27153-F AL-27154-F AL-27155-F AL-27157-F A

Oxidation Stability, hours EN 14112 Replicate 1 9.36 0.14 2.60 4.67  Replicate 2 9.36 0.18 2.59 4.56  Replicate 3 9.35 0.18 2.27 4.47  Mean 9.36 0.17 2.49 4.57 Oxidation Stability, mg/ 100 ml Modified ASTM D2274 

Replicate 1

 Filterable insolubles 0.2 12.3 9.4 1.5  Adherent Insolubles 0.1 1.3 1.5 0.5  Total Insolubles 0.3 13.6 10.9 2.0  Iso-Octane Insolubles 0.2 87.6 94.6 2.8 

Replicate 2

 Filterable insolubles 0.2 11.1 8.5 1.5  Adherent Insolubles 0.0 1.5 1.3 0.8  Total Insolubles 0.2 12.6 9.8 2.3  Iso-Octane Insolubles 0.2 ND 95.8 2.8 Mean Total Insolubles 0.3 13.1 10.4 2.2 Mean Iso-Octane Insolubles 0.2 87.6 95.2 2.8 Oxidation Stability, Pressure Vessel ASTM D525 Induction Period Method, minutes >780 150 270 487 Thermal Stability, deposit, mg ASTM D6468 Modified 0.5 0.1 0.3 0.3 Total Acid Number, mg KOH/g ASTM D664 0.08 1.31 0.29 0.11 Total Acid Number after D2274, mg KOH/g  Replicate 1 0.21 5.54 3.21 1.05  Replicate 2 0.27 ND 2.93 1.19  Mean 0.24 5.54 3.07 1.12 Total Glycerin, %(mass) ASTM D6584 0.15 0.132 0.298 0.225 Free Glycerin, %(mass) ASTM D6584 0.001 0.003 0.007 0.015 

18
Sample Identification Method AL-27161-F 

Oxidation Stability, hours EN 14112  Replicate 1 5.13  Replicate 2 5.11  Replicate 3 5.09  Mean 5.11 Oxidation Stability, mg/ 100 ml Modified ASTM D2274  Replicate 1  Filterable insolubles 1.0  Adherent Insolubles 0.1  Total Insolubles 1.1  Iso-Octane Insolubles 0.60  Replicate 2  Filterable insolubles 0.8  Adherent Insolubles 0.2  Total Insolubles 1.0  Iso-Octane Insolubles 0.80 Mean Total Insolubles 1.1 Mean Iso-Octane Insolubles 0.7 Oxidation Stability, Pressure Vessel ASTM D525  Induction Period Method, minutes >780 Thermal Stability, deposit, mg ASTM D6468 Modified 0.2 Total Acid Number, mg KOH/g ASTM D664 0.37 Total Acid Number after D2274, mg KOH/g  Replicate 1 1.63  Replicate 2 1.50  Mean 1.57 Total Glycerin, %(mass) ASTM D6584 0.151 Free Glycerin, %(mass) ASTM D6584 0.003 

19
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Stability of Biodiesel and Biodiesel Blends: Interim Report 

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NREL/TP-540-39721 

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FC06.9400 

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R.L. McCormick, T.L. Alleman, J.A. Waynick, S.R. Westbrook, and 

S. Porter 

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This is an interim report for a study of biodiesel oxidative stability. It describes characterization and accelerated 

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biodiesel; biodiesel stability; oxidative stability; B100; biodiesel blends 

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