March 2003 • NREL/SR-510-31460 

Production of Biodiesels from 

Multiple Feedstocks and

Properties of Biodiesels and

Biodiesel/Diesel Blends 

Final Report 

Report 1 in a series of 6 

J.A. Kinast 

Gas Technology Institute 

Des Plaines, Illinois 

National Renewable Energy Laboratory 

1617 Cole Boulevard 

Golden, Colorado 80401-3393 

NREL is a U.S. Department of Energy Laboratory

Operated by Midwest Research Institute • Battelle • Bechtel 

Contract No. DE-AC36-99-GO10337 
March 2003 • NREL/SR-510-31460 

Production of Biodiesels from 

Multiple Feedstocks and

Properties of Biodiesels and

Biodiesel/Diesel Blends 

Final Report

Report 1 in a series of 6 

J.A. Kinast 

Gas Technology Institute 

Des Plaines, Illinois 

NREL Technical Monitor: K.S. Tyson 

Prepared under Subcontract No. ACG-8-17106-02 

National Renewable Energy Laboratory 

1617 Cole Boulevard 

Golden, Colorado 80401-3393 

NREL is a U.S. Department of Energy Laboratory

Operated by Midwest Research Institute • Battelle • Bechtel 

Contract No. DE-AC36-99-GO10337 
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SUMMARY 

In a project sponsored by the National Renewable Energy Laboratory, the Institute of Gas 

Technology is conducting an investigation of biodiesels (methyl esters) produced from 

vegetable- and animal-based feedstocks. 

Soy biodiesel is predominantly used in the United States, while canola biodiesel is dominant in 

Europe. The high price of biodiesel (over double the price of diesel) is in large part due to the 

high price of the feedstock. However, biodiesel can be made from other feedstocks, including 

beef tallow, pork lard, and yellow grease. This project sought to understand the impact of the 

different feedstocks by generating biodiesel from each feedstock through one producer, to 

minimize the variation in production techniques, and by subjecting the samples to a series of 

tests to quantify the differences between them. 

The production of methyl esters identified a number of conclusions 

• Biodiesel is easier to produce and cleaner with equivalent amounts of processing when 

starting with clean vegetable oil (e.g., soy and canola). The tallow, lard, and yellow grease 

biodiesels need additional processing at the end of transesterification to achieve acceptable 

biodiesel properties, and would benefit from processing before transesterification to reduce 

or eliminate components that may interfere, as for the high free fatty acid yellow grease. 

• Additional investigation should be considered that would focus on methods of economically 

handling free fatty acids and other components, at least to reduce their interference, and 

ideally, contribute to the production of methyl esters. 

• Adequate testing is required during and after the processing to know the state of the fuel. 

Without it, the producer cannot ensure that "fuel grade" methyl esters are produced, instead 

of "commercial grade". 

The properties testing of the biodiesels confirmed that the known advantages and 

disadvantages of soy and canola biodiesels are the same as the biodiesels based on the other 

feedstocks, and that the changes in properties expected from the feedstock variations occur. 

• The test results show that there are problems in operating at lower temperatures (cloud 

point, cold filter plugging point, and pour point), and that the minimum temperatures at which 

biodiesels are usable increase as they move from vegetable to animal sources, due to the 

greater degree of saturation. Yellow grease, although originally vegetable oils, display 

intermediate temperatures. Additives to reduce cloud/plugging/pour point problems would 

help the adoption of biodiesels in areas with low ambient temperatures (much of the United 

States for the tallow and lard biodiesels). 

• Viscosities show the same trends as temperatures, with the lard and tallow biodiesels higher 

than the soy and canola biodiesels. Because of the effect that high viscosities can have on 

injector spray performance, this property should be monitored in biodiesel production. 

• The biodiesels have high boiling points, flash points, and extremely low vapor pressure, as 

well as an inability to smoke under the smoke point test. These results indicate a high level 

of safety for handling biodiesels. 

iii 
The specifications used to identify methyl esters that are acceptable as biodiesel were reviewed 

in light of the properties testing. The biodiesel specifications do not need any additions from the 

test suite conducted in this project. The tests would contribute additional information about the 

composition and properties, but the tests in the specifications adequately identify whether the 

quality of the fuel is acceptable. 

The biodiesel specification and the ASTM D 975 diesel specification can be partially applied to 

B20, with problems when the limiting values differ significantly between the two. 

Biodiesel is mixed with diesel to bring many of the beneficial characteristics to diesel equipment, 

while reducing the overall cost of the fuel. Because biodiesel is usually used blended, the focus 

was to determine the characteristics of biodiesels from different feedstocks in varying 

concentrations with diesel when tested on a consistent basis. It was expected that some 

properties would vary in a non-intuitive manner, e.g., not varying linearly with respect to blend 

fraction. 

The results add data to concentration ranges that have previously been overlooked in the study 

of the potential of biodiesel blends. It also adds information concerning feedstocks that have 

been considered only superficially. 

The properties tested were those that would most affect operation of diesels, and consisted of: 

viscosity, pour point, cloud point, cold filter plugging point, Cetane number, scuffing load BOCLE 

(lubricity), and oxidation stability. Cetane number did not exhibit any unusual characteristics, 

with essentially linear variation with respect to blend fraction. Fuel oxidation stability tests show 

a predominantly linear relation between biodiesel fraction and insolubles produced, moving 

toward the higher levels of the biodiesels. However, two biodiesels showed peaks with 35% 

biodiesel that were significantly higher than pure biodiesel. 

Of particular interest for people considering the use of biodiesels in other than B20 or pure 

applications is the shift in temperature for various properties tested. The biodiesel blends 

exhibited a viscosity depression at low concentrations. Conversely, most biodiesels significantly 

increased pour point, cloud point, and cold filter plugging point at low concentrations (<10-20%), 

then proceeded more linearly above that. Care should be taken in handling and use due to the 

temperature increases that occurred for pour point, cloud point, and cold filter plugging point. 

The effect on lubricity cited by advocates of biodiesel was verified by the test results. Significant 

lubricity increases occur with concentrations at 3% or less of the biodiesels, seeming to confirm 

the concept that biodiesel additives can improve the operation of diesels and extend the life of 

their components. It is fortunate that these concentrations avoid the ranges where temperature 

increases occur. In particular, further study may be warranted to improve the processing of the 

beef tallow and pork lard, with a goal of reducing cost while enhancing the characteristics of the 

methyl esters that improve lubricity. 

iv 
TABLE OF CONTENTS

SUMMARY ............................................................................................................................... III

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

PRODUCTION OF BIODIESEL FROM MULTIPLE FEEDSTOCKS.......................................... 2

BIODIESEL PROCESSING BACKGROUND..................................................................................... 2

FEEDSTOCKS CONSIDERED FOR BIODIESEL............................................................................... 4

BIODIESEL PRODUCTION AND PROBLEMS .................................................................................. 5

PRODUCTION ISSUES AND POTENTIAL SOLUTIONS ..................................................................... 7

ALTERNATE FEEDSTOCK PRODUCTION ...................................................................................... 7

PROPERTIES OF BIODIESELS FROM MULTIPLE FEEDSTOCKS ........................................ 9

FUEL PROPERTIES TESTS......................................................................................................... 9

PROPERTIES OF BIODIESELS....................................................................................................10

EVALUATION OF BIODIESEL SPECIFICATION ....................................................................27

COMPARISON OF BIODIESEL AND DIESEL SPECIFICATIONS ..........................................29

BIODIESEL/DIESEL BLEND TESTING ...................................................................................31

TESTING METHODOLOGY.........................................................................................................31

LOT D-434..............................................................................................................................31

ASTM METHOD ......................................................................................................................31

BIODIESEL/DIESEL BLEND TEST RESULTS.................................................................................33

CONCLUSIONS .......................................................................................................................47

v 
LIST OF FIGURES 

Figure 1. Biodiesel/Diesel Blend Viscosity Test Results ..........................................................34 

Figure 2. Biodiesel/Diesel Blend Viscosity Test Results (0–10% biodiesel blend range) .........34

Figure 3. Biodiesel/Diesel Blend Pour Point Test Results .......................................................36

Figure 4. Biodiesel/Diesel Blend Pour Point Test Results (0–10% biodiesel blend range).......36

Figure 5. Biodiesel/Diesel Blend Cloud Point Test Results......................................................38

Figure 6. Biodiesel/Diesel Blend Cloud Point Test Results (0–10% biodiesel blend range).....38

Figure 7. Biodiesel/Diesel Blend Cold Filter Plugging Point Test Results ................................40

Figure 8. Biodiesel/Diesel Blend Cold Filter Plugging Point Test Results (0–10% biodiesel 

blend range) ............................................................................................................40

Figure 9. Biodiesel/Diesel Blend Cetane Number Test Results ...............................................42

Figure 10. Biodiesel/Diesel Blend Cetane Number Test Results (0–10% biodiesel blend 

range)......................................................................................................................42

Figure 11. Biodiesel/Diesel Blend SLBOCLE Test Results........................................................44

Figure 12. Biodiesel/Diesel Blend SLBOCLE Test Results (0–10% biodiesel blend range).......44

Figure 13. Biodiesel/Diesel Blend Oxidation Stability Test Results............................................46

Figure 14. Biodiesel/Diesel Blend Oxidation Stability Test Results (0–10% biodiesel blend 

range)......................................................................................................................46

vi 
LIST OF TABLES 

Table 1. Biodiesel Specifications (July 1996) (For pure mono alkyl esters of long chain fatty 

acids derived from renewable lipid feedstocks) .................................................................. 5

Table 2. Methods For Testing Properties of Biodiesels .............................................................. 9

Table 3. Test Results for ASTM D 86 — Distillation of Petroleum Products ..............................11

Table 4. Test Results for ASTM D 93 — Flash-Point by Pensky-Martens Closed Cup Tester...12

Table 5. Test Results for ASTM D 97 — Pour Point of Petroleum Products ..............................12

Table 6. Test Results for ASTM D 130 — Detection of Copper Corrosion from Petroleum

Products by the Copper Strip Tarnish Test.........................................................................12

Table 7. Test Results for ASTM D 240 — Heat of Combustion of Liquid Hydrocarbon Fuels by

Bomb Calorimeter, Btu/lb ...................................................................................................13

Table 8. Test Results for D 445 — Kinematic Viscosity of Transparent and Opaque Liquids ....13

Table 9. D 482 — Ash from Petroleum Products.......................................................................14

Table 10. Test Results for D 524 — Ramsbottom Carbon Residue of Petroleum Products.......14

Table 11a. Test Results for ASTM D 613 — Cetane Number of Diesel Fuel Oil (results from

WIlliams Lab) .....................................................................................................................15

Table 11b. Test Results for ASTM D 613 — Cetane Number of Diesel Fuel Oil (results from

CSM) .................................................................................................................................15

Table 12. Test Results for ASTM D 664 — Acid Number of Petroleum Products by

Potentiometric Titration ......................................................................................................15

Table 13. Test Results for ASTM D 971 — Interfacial Tension of Oil Against Water by the Ring

Method...............................................................................................................................15

Table 14. Test Results for ASTM D 1091 — Standard Test Methods for Phosphorus in 

Lubricating Oils and Additives, weight percent ...................................................................16

Table 15. Test Results for ASTM D 1094 — Water Reaction of Aviation Fuels .........................16

Table 16. Test Results for ASTM D 1160 — Distillation of Petroleum Products at Reduced 

Pressure ............................................................................................................................17

Table 17. Test Results for D 1298 — Specific Gravity - by Hydrometer Method........................17

Table 18. Test Results for ASTM D 1322 — Smoke Point of Kerosene and Aviation Turbine 

Fuel....................................................................................................................................18

Table 19. Test Results for ASTM D 1796 — Water and Sediment in Fuel Oils by the Centrifuge

Method (Laboratory Procedure) .........................................................................................19

Table 20. Test Results for ASTM D 1959 — Iodine Value of Drying Oils and Fatty Acids .........19

Table 21. Test Results for ASTM D 2274 — Standard Test Method for Oxidation Stability of

Distillate Fuel Oil (Accelerated Method), mg/100 mL..........................................................20

Table 22. Test Results for ASTM D 2500 — Cloud Point of Petroleum Products ......................20

Table 23. Test Results for D 2622 — Test Method for Sulfur in Petroleum Products by X-Ray

Spectrometry .....................................................................................................................21

Table 24. Test Results for ASTM D 2624 — Electrical Conductivity of Aviation and Distillate

Fuels..................................................................................................................................21

Table 25. Test Results for ASTM D 3231 — Standard Test Method for Phosphorus in Gasoline,

ppm....................................................................................................................................21

Table 26. Test Results for ASTM D 3241 — Thermal Oxidation Stability of Aviation Turbine 

Fuels (JFTOT Procedure) ..................................................................................................22

Table 27. Test Results for ASTM D 3242 — Acidity in Aviation Turbine Fuel (Total Acid 

Number).............................................................................................................................22

Table 28. Test Results for D 4539 — Filterability of Diesel Fuels by Low-Temperature Flow

Test (LTFT) (Cold Filter Plugging Point).............................................................................22

Table 29. Test Results for ASTM D 4629 — Trace Nitrogen in Liquid Petroleum Hydrocarbons 

by Syringe/Inlet Oxidative Combustion and Chemiluminescence Detection .......................23

vii 
Table 30. Test Results for ASTM D 5191 — Vapor Pressure of Petroleum Products (Mini 

Method) .............................................................................................................................23

Table 31. Test Results for ASTM D 5291 — Instrumental Determination of Carbon, Hydrogen,

and Nitrogen in Petroleum Products and Lubricants ..........................................................24

Table 32. Test Results for ASTM D 6078 — Standard Test Method for Evaluating Lubricity of

Diesel Fuels by the Scuffing Load Ball-on-Cylinder Lubricity Evaluator (SLBOCLE) ..........24

Table 33. Test Results for ASTM D 6217 — Standard Test Method for Particulate 

Contamination in Middle Distillate Fuels by Laboratory Filtration........................................24

Table 34. Test Results for Christina Planc method....................................................................25

Table 35. Total Fatty Acids, % ..................................................................................................25

Table 36. Carbon, Hydrogen, Nitrogen, Oxygen Analysis .........................................................25

Table 37. Gas Chromatographic Analysis of Fatty Acids...........................................................26

Table 38. Biodiesel Specifications (July 1996) (For pure mono alkyl esters of long chain fatty

acids derived from renewable lipid feedstocks) .................................................................27

Table 39. Comparison of Biodiesel Specifications and ASTM D 975 Specifications ..................29

Table 40. Certification Diesel Fuel Lot D-434 Properties ...........................................................31

Table 41. Physical and Chemical Tests of Biodiesel Blends......................................................32

Table 42. Biodiesel Blend Viscosity Test Results......................................................................33

Table 43. Biodiesel Blend Pour Point Test Results, °C .............................................................35

Table 44. Biodiesel Blend Cloud Point Test Results, °C............................................................37

Table 45. Biodiesel Blend Cold Filter Plugging Point Test Results, °C ......................................39

Table 46. Biodiesel Blend Cetane Number Test Results ...........................................................41

Table 47. Biodiesel Blend Scuffing Load BOCLE Test Results .................................................43

Table 48. Biodiesel Blend Oxidation Stability Test Results........................................................45

viii 
INTRODUCTION 

In a project sponsored by the National Renewable Energy Laboratory, the Gas Technology 

Institute (formerly Institute of Gas Technology) conducted an investigation of biodiesel fuels 

produced from various vegetable- and animal-based feedstocks. Due to the varying nature of 

the feedstocks and the processes for converting them into suitable biodiesel (methyl esters), an 

important part of the study has been the laboratory testing of the properties to determine the 

characteristics of each fuel. 

The effort was conducted in three parts. The first segment of the project involved the production 

of methyl esters from the various feedstocks and a review of the issues encountered with each 

feedstock. In the second part, the biodiesels were subjected to a series of tests to document the 

properties of the methyl esters. With an understanding of the values and importance of each 

test, the specifications for acceptance of biodiesel were reviewed. 

In the third part, the effect of mixing biodiesel and diesel was studied, because an 

understanding of the basic properties does not necessarily indicate what will happen as a result 

of mixing it with diesel fuel. Due to the cost, biodiesel usually is mixed with diesel (instead of 

used straight, or "neat") to bring many of the beneficial characteristics to diesel equipment, while 

reducing the overall cost of the fuel. Because of the different compositions and basic differences 

between biodiesel and diesel, some properties may vary in a non-intuitive manner, e.g., not 

varying linearly with respect to blend fraction. The testing quantifies these effects of blending the 

multi-feedstock biodiesels with diesel over a range of varying compositions. 

1 
PRODUCTION OF BIODIESEL FROM MULTIPLE FEEDSTOCKS 

Biodiesel Processing Background 

At the beginning of this project, there were three common types of biodiesel production 

technology, the use of which depended on feedstock quality and the sophistication of the facility. 

Combinations of some technologies are possible. 

Fats and oils are composed of molecules called triglycerides. Each triglyceride is composed of 

three long-chain fatty acids of 8 to 22 carbons attached to a glycerol backbone. Biodiesel is 

composed of fatty acid chains that are chemically bonded to one methanol molecule. The 

glycerol molecules are almost completely removed from the final biodiesel product. Biodiesel is 

sometimes called fatty acid methyl esters or FAME. The glycerin byproduct has thousands of 

industrial chemical uses in common household products and foods. When the fatty acid chains 

break off the triglyceride, they are known as free fatty acids. Free fatty acids are desirable 

biodiesel feedstocks, but require different conversion processes compared to triglycerides. 

Biodiesel feedstock are classified based on their free fatty acid content as follows: 

 Refined oils, such as soy bean or refined canola oil (FFA <1.5%) 

 Low free fatty acid yellow greases and animal fats (FFA<4%) 

 High free fatty acid greases and animal fats (FFA ≥ 20%) 

There are other potential feedstocks available at this time, namely trap and sewage grease and 

other very high free fatty acid greases whose FFA exceed 50%. Technology improvements 

need to be developed before these feedstocks can be used for biodiesel production. 

Commercial biodiesel technologies can be grouped as follows: 

 Base catalyzed transesterification with refined oils 

 Base catalyzed transesterification with low free fatty acid greases and fats 

 Acid esterification followed by transesterification of low or high free fatty acid greases and 

fats 

Technologies can be run as batch or continuous processes. Given the limited size of the 

domestic market for biodiesel, most U.S. firms have used batch technology. Continuous 

processes used in Europe and in industrial processes in the U.S. (to produce methyl esters for 

uses other than as fuel) can use raw or may require refined oils. Batch processes provide 

excellent opportunities for quality control if variations in feedstock quality are common, such as 

with yellow grease and animal fats. 

The goal of all the technologies is to produce a fuel grade biodiesel whose properties meet 

ASTM PS 121. The key quality control issues involve the complete (or nearly complete) removal 

of alcohol, catalyst, water, soaps, glycerine, and unreacted or partially reacted triglycerides and 

2 
free fatty acids. Failure to remove or minimize these contaminates causes the methyl ester 

product to fail one or more fuel standards. 

There are a wide variety of commercial methyl ester products made for the industrial lubricant 

and chemical processing industries. Processing requirements for these products may not be 

sufficiently robust to produce a fuel-grade biodiesel. The most common problem is the presence 

of high levels of unreacted or partially reacted triglycerides and glycerine, which increases 

viscosity, raises cloud and pour points, causes product separation, and may lead to engine 

damage. Only methyl esters that meet ASTM PS 121 are considered “biodiesel.” 

A brief overview of each major technology follows. 

Base catalyzed transesterification using refined oils has high efficiencies, up to 99.9%, and 

produces good to high quality fuels after removing excess methanol, base catalyst, and 

glycerine. A description of the technology can be found in Sheehan, J.; Camobreco, V.; Duffield, 

J.; Graboski, M.; Shapouri. H. (1998) Life Cycle Inventory of Biodiesel and Petroleum Diesel 

for Use in an Urban Bus: Final Report. 314 pp.; NICH Report No. SR-580-24089. 

The basic chemistry of the reaction requires 3 molecules of methanol (or other alcohol) for every 

molecule of triglyceride (e.g., oil or fat), which corresponds roughly to about 10% the weight of 

methanol per mass of oil processed. The catalyst ratio is roughly 10% of the methanol mass. 

Glycerine is the major byproduct of the process. 

A typical input/output stream is shown below. 

Input streams: 

Refined oil 

Methanol 

KOH 88% 

Acid (sulfuric, acetic, HCL) 

Water 

Electricity 

Output Streams: 

Biodiesel 

Glycerine 88% 

Fertilizer 

Byproduct chemicals 

1,000 kg 

107 kg 

10 kg 

8 kg 

17 kg 

20 kWh 

1,000 kg 

125 kg 

23 kg 

nil 

Small amounts of FFA (less than 1.5%) are converted into soaps. These soaps typically are 

removed with the glycerine or removed during the crude oil refining process. Other commonly 

used base catalysts include sodium hydroxide or sodium methoxide. Sodium catalysts do not 

produce fertilizer byproducts. The acids are used to break emulsifications in the glycerine 

byproducts for partial processing and to neutralize the base catalysts. 

There are numerous variations of this basic technology. Different catalysts, including nonalkaline catalysts can be used. Anhydrous ethanol, isopropyl or butyl alcohols can be 

substituted for methanol, but reaction times are slower, and yields may be lower, resulting in 

more rigorous quality control measures and additional processing. Various grades of glycerin 

can be produced, depending on the scale of the facility. Crude glycerine is often shipped to 

larger facilities for refining. The basic transesterification process is run at standard atmosphere 

3 
and temperatures around 60o

C. However, some continuous technologies use higher 

temperatures and elevated pressures, typically in the super critical range of methanol. 

Distillation is sometimes used for quality control, but not always necessary. 

Base catalyzed transesterification using low free fatty acid feedstocks is a simple variation of the 

technology described above. Typically, a small amount of base catalyst is added to the 

feedstock to react with the free fatty acids and form soaps. The soaps are removed, and the 

transesterification process proceeds. Back yard producers and very small plants tend to recover 

the soap for novelty products or compost it. An equal amount of clean oils tends to be lost with 

the soaps, leading to significant yield losses depending on the free fatty acids level of the 

feedstock. Larger facilities can react the soaps back into free fatty acids and market them as 

agricultural products. The attractiveness of this variation depends on the availability of local 

agricultural markets for the free fatty acids and the value of those products (should be higher 

than biodiesel). 

A more efficient approach to high free fatty acid feedstocks is the last technology to be 

reviewed—acid esterification followed by transesterification. The free fatty acids are reacted 

with methanol (1:1 ratio) and acid catalysts such as sulfuric acid, to form methyl esters. Yields 

on this reaction are typically less than 96%, which means that roughly 4% of the available free 

fatty acids remain in the feedstock stream and will react with the base catalyst in the next step 

to form soaps. Some foaming control processes may be required if the soaps are not removed 

prior to transesterification. The rest of the process is similar to those described above. Resulting 

yields can exceed 99%, depending on the amount of free fatty acids in the original feedstock, 

and the variety of byproducts produced. 

Feedstocks Considered For Biodiesel 

The previous experience with biodiesels has focused on fuel derived from soybean or canola 

(rapeseed) oil. These oils are available in a consistently high quality form, and are the easiest to 

process for making biodiesels. Most of the biodiesel available in the United States is based on 

soybean oil. Soybean and canola oil were included in this project as a reference for the other 

biodiesels. 

In addition to plant oils, three animal (livestock) feedstocks were included in this project. Beef 

tallow consists of the renderings from meat packing and is available in either an edible or 

inedible form. The difference between the two forms is based on what is considered acceptable 

for food products. As a result, there is traditionally a larger variation in the composition of 

inedible beef tallow compared to the edible tallow. Pork lard is the swine-derived counterpart to 

beef tallow, also as a result of the meat packing process. The advantages of tallow and lard are 

their lower cost compared to soybean and canola oil. However, a disadvantage is that they may 

require additional processing to produce an acceptable biodiesel. 

The third class of feedstocks is waste yellow grease. It is soybean oil (or equivalent) which has 

been used for cooking. Characteristic of the feedstock are the larger amounts of free fatty acids 

that have been liberated during the cooking process. Because of seasonal variations, the free 

fatty acid content can range from 2% to 20% or more. However, 4% to 10% is a more typical 

range, and was selected for the two yellow greases. Like the tallows and lard, the variation in 

composition is much wider than the plant oils. 

4 
Acidulated soapstock was considered as another feedstock, but was not available because the 

group developing the process was unable to produce methyl esters in sufficient quantity for 

testing. 

Biodiesel Production and Problems 

Methyl esters were required to meet the specifications shown in Table 1 (which were being 

evaluated by ASTM at the time) to be considered acceptable for use as biodiesels at the start of 

this project. The subsequently released ASTM PS121-99, Provisional Specification for 

Biodiesel Fuel (B100) Blend Stock for Distillate Fuels, is substantially similar to the draft 

standard used in this project. To determine whether the biodiesels were potentially acceptable, 

individuals from IGT, NREL, and the National Biodiesel Board had decided that an Acid Number 

screening test would be used to ensure that each of the biodiesel samples met at least this 

minimum fuel quality requirement before investing money into the complete suite of analyses. 

Table 1. Biodiesel Specifications (July 1996) 

(For pure mono alkyl esters of long chain fatty acids 

derived from renewable lipid feedstocks) 

Property ASTM Method Limits Units 

Flash Point 

Water & Sediment 

Carbon Residue, 100% sample 

Sulfated Ash 

Kinematic Viscosity, 40°C 

Sulfur 

Cetane 

Cloud Point 

Copper Strip Corrosion 

Acid Number 

Free Glycerin 

Total Glycerin 

D93 

D1796 

D5241 

D874 

D445 

D2622 

D613 

D2500 

D130 

D664 

GC2 

GG2 

100.0 min. 

0.050 max. 

0.050 max. 

0.020 max. 

1.9 — 6.5 

0.050 max. 

40 min. 

By Customer 

No. 3b max. 

0.80 max. 

0.020 max. 

0.240 max. 

°C 

vol. % 

wt. % 

wt. % 

mm2/sec (cSt) 

wt. % 

°C 

mg KOH/g 

wt. % 

wt. % 

1

 or equivalent ASTM testing method.

2

 Austrian (Christina Planc) update of USDA test method.

Chemol Company, Inc., agreed to manufacture biodiesel from the feedstocks as part of this 

project. They applied their expertise with producing methyl esters for other purposes to deliver 

biodiesel. The soy, canola, inedible beef tallow, and pork lard feedstocks were supplied by 

Chemol. The low free-fatty-acid yellow grease (nominal 2% to 5%) was from Simplot (Idaho), 

and the edible beef tallow was from HRR Enterprises (Chicago, IL). In processing the 

feedstocks, they used some of their smaller equipment in batch mode. 

5 
There were initial problems in that only two methyl esters passed the Acid Number test (less 

than 0.8 mg KOH/g). These preliminary results indicated that "commercial grade" methyl esters 

may not meet "fuel grade" requirements. It had then been decided that Chemol would reprocess 

the rejected biodiesels. 

The initial soy methyl ester that passed the Acid Number test did not meet the complete 

biodiesel fuel specification. Although the free glycerin level was within the 0.02 wt. % limit, the 

total glycerin value of 0.798 wt. % reported in the analysis considerably exceeded the 0.24 

wt. % maximum value of the specification. The test results for the methyl tallow indicated it 

passed. The total glycerin was 0.102 wt. %, well within the biodiesel requirements. Other 

samples had similar problems during the production of the biodiesel fuels. 

After additional processing and modifications to their facility, Chemol was able to deliver 

adequate methyl esters from each of the feedstocks except for the high free fatty acid yellow 

grease. The high concentration of free fatty acids interfered with their ability to process the 

yellow grease. 

A review of the process indicated a number of problems in producing the methyl esters. At 

Chemol, the heated oil is dried under vacuum since water deactivates the catalyst. 

Transesterification then occurs when the ester reacts with carboxylic acid or alcohol; methanol 

is used when the goal is methyl esters. Sodium methoxide catalyst is added (0.1% to 0.3%) and 

the mixture is allowed to react. After the reaction, the catalyst is removed by water washing or 

acidification. The mixture is then filtered to remove trace soaps and heated under vacuum to 

remove small amounts of fatty acid methyl esters. 

When processing feedstocks with free fatty acids (FFAs), additional steps must be taken, 

because the FFAs will deactivate the catalyst during reaction. Higher FFA concentrations result 

in more oil that is lost in processing. The FFAs, such as that in yellow grease, are formed from 

triglycerides (principal component of fats and oils). These form naturally from enzymes in oils, 

oxidation, or acids/bases/moisture and heat reactions. Removal of FFAs at Chemol involves 

alkali refining. In this process, the oil is mixed with caustic soda (sodium hydroxide) to form 

soaps. The soap is dispersed in aqueous phase together with phospholipids, pigments, and 

other compounds. Some oil is removed with the soaps (loss) as the soap is separated. The 

processing parameters are a function of FFA content, phospholipids (which act as surfactants), 

and caustic concentration. Soap must be removed to prevent filter clogging in the bleaching 

steps. The soapstock is commonly acidified and then sold as animal feed. The remaining 

material can then be processed into methyl esters. The limitations in the Chemol pilot scale 

process revolve around the composition of the oil after the FFAs are substantially removed. 

Since Chemol’s process requires that less than 1% FFAs enter the transesterification process; 

the full benefits of utilizing inexpensive waste greases may not be realized in this environment. 

After the basic transesterification process, the cleanup is equally important in providing methyl 

esters suitable for use as fuel. Some of the biodiesels had high total glycerin values, which was 

considered not surprising by Chemol. This value is tied to the conversion efficiency of their 

process and the degree of reprocessing. Chemol's ability to control this value was based on the 

reprocessing procedure as well as their ability to accurately determine the total glycerin value. 

Since Chemol was not initially using the C. Planc GC method to determine the free and total 

glycerin levels, they cannot precisely determine the levels of free and total glycerin. Adequate 

testing during the processing was introduced as the project continued. 

6 
CIFER identified a supplier of a suitable high free fatty acid yellow grease, who was also willing 

to produce the biodiesel. The biodiesel was produced in the following steps: 

1. Acid catalyzed pre-esterification of free fatty acids. 

2. Washing and prep. 

3. Conventional Transesterification. 

4. Washing and prep. 

The washing and preparation steps, especially, are part of a patented process described in U.S. 

Patent Nos. 5,399,791 and 5,434,279. By working to convert the free fatty acids into a form that 

wouldn't interfere with the basic transesterification, CIFER's supplier was able to avoid the 

problems that had occurred at Chemol. 

Production Issues and Potential Solutions 

In summary, the basic problems and potential solutions are the following: 

1. Free fatty acids and other compounds interfere with transesterification, reacting with the 

base to form soaps. One approach is to supply additional base to compensate for the 

amount lost and to ensure processing completion in an acceptable period of time. However, 

this increases processing costs. In addition, water is formed during the base and free fatty 

acid reaction, which will interfere with transesterification. The alternatives to this are: 

• Preprocessing to eliminate the free fatty acids. This step can incur additional cost, but 

the cost may be offset by increasing the overall useful yield. It proved successful in the 

production of biodiesel from the high free fatty acid yellow grease. 

• Separation by either physical or chemical means. Again, this can increase cost unless 

the fatty acids can be recovered and sold for higher value products. 

• Adequate processing at the end is necessary to remove components considered 

detrimental to biodiesel. For example, it was felt that additional washing would have 

reduced the total glycerin that was present in the early samples. 

2. Adequate testing is required to ensure completeness of each stage of the process. 

In addition, some processors have suggested the overall process could be improved if it were 

moved from batch to a more continuous mode. However, if the feedstock varies significantly and 

continuous monitoring is not possible, batch mode may better permit adjusting the process to 

the feedstock. Both economies of scale and recycling of some components such as catalysts 

are considered possible. 

Alternate Feedstock Production 

A number of other organizations have been considering the use of alternate feedstocks for 

biodiesel / methyl ester production. The focus has been on acidulated soapstocks. Acidulated 

soapstock is a byproduct created when hexane and other industrial substances are used to 

extract and refine edible oil from soy, canola, cotton, safflower, and sunflower. Cottonseed 

processors generate 60-120 million pounds of soapstock annually. It has traditionally been used 

by fatty acid producers, soap makers, foundries, and animal feed manufacturers. Other uses 

7 
have recently been studied, e.g., it has been considered for dust suppression on highways, 

surfactants, and as a biodegradable coating for various materials. 

IGT investigated the possibility with Agricultural Utilization Research Institute and the University 

of Nebraska. However, they were unable to provide any material. 

NOPEC, a producer of soy-based biodiesel in Florida, investigated the possibility of processing 

acidulated soapstock at IGT's request. They were unable to process the feedstock without 

significant modification to their pilot reactor. 

IGT also contacted Mr. Bob Riley of Feed Energy (Des Moines IA), as a potential source of 

methyl esters produced from acidulated soapstock. In a project with Iowa State, they were able 

to deliver 98% conversion, in small samples. Batch quantities had been produced that were 

measured on the order of pints, not gallons. One focus was to produce methyl esters that meet 

biodiesel specifications, but they were not able to meet those with their initial attempts. The 

concept was being pursued because of the significantly reduced cost of the feedstock, on the 

order of 55% that of soybean oil. Although it was originally indicated that there might be enough 

methyl ester for testing (in exchange for the results), nothing has been delivered. 

Recent activities by the USDA (Philadelphia) have looked at processes that utilize biocatalysts 

to optimize production and improve the economics of enzymatic biodiesel production from fats, 

oils, and greases. A simple two-step chemical procedure for the converting soapstock into 

simple esters for use as biodiesel was developed and a patent application has been filed for this 

technology. Large-scale production of soapstock-based biodiesel was undertaken to evaluate 

soapstock esters as fuels for diesel engines. 

8 
PROPERTIES OF BIODIESELS FROM MULTIPLE FEEDSTOCKS 

Fuel Properties Tests 

The properties selected for study as part of this effort support feedstock-neutral specifications 

for biodiesel. Also of interest were the differences in temperature-dependent properties that 

would affect low-temperature fuel handling as a result of the different feedstocks. The tests that 

were conducted are shown in Table 2, and are discussed in the following section. 

Table 2. Methods For Testing Properties of Biodiesels 

ASTM Title 

D 86 Distillation of Petroleum Products 

D 93 Flash-Point by Pensky-Martens Closed Cup Tester 

D 97 Pour Point of Petroleum Products 

D 130 Detection of Copper Corrosion from Petroleum Products by the 

Copper Strip Tarnish Test 

D 240 Heat of Combustion of Liquid Hydrocarbon Fuels by Bomb 

Calorimeter 

D 445 Kinematic Viscosity of Transparent and Opaque Liquids (the 

Calculation of Dynamic Viscosity) 

D 482 Ash from Petroleum Products 

D 524 Ramsbottom Carbon Residue of Petroleum Products 

D 613 Cetane Number of Diesel Fuel Oil 

D 664 Acid Number of Petroleum Products by Potentiometric Titration (for 

dark, opaque liquids) 

D 971 Interfacial Tension of Oil Against Water by the Ring Method 

D 1091 Phosphorus in Lubricating Oils and Additives 

D 1094 Water Reaction of Aviation Fuels 

D 1160 Distillation of Petroleum Products at Reduced Pressure 

D 1298 Density, Relative Density (Specific Gravity), or API Gravity of Crude 

Petroleum and Liquid Petroleum Products by Hydrometer Method 

D 1322 Smoke Point of Kerosene and Aviation Turbine Fuel 

D 1796 Water and Sediment in Fuel Oils by the Centrifuge Method 

(Laboratory Procedure) 

D 1959 Iodine Value of Drying Oils and Fatty Acids 

D 2274 Oxidation Stability of Distillate Fuel Oil (Accelerated Method) 

D 2500 Cloud Point of Petroleum Products 

D 2622 Sulfur in Petroleum Products by X-Ray Spectrometry 

D 2624 Electrical Conductivity of Aviation and Distillate Fuels 

D 3231 Phosphorus in Gasoline 

9 
Table 2. Methods For Testing Properties of Biodiesels, cont. 

ASTM Title 

D 3241 Thermal Oxidation Stability of Aviation Turbine Fuels (JFTOT 

Procedure) 

D 3242 Acidity in Aviation Turbine Fuel (Total Acid Number) 

D 4539/ 

IP 309 

Filterability of Diesel Fuels by Low-Temperature Flow Test (LTFT) 

(Cold Filter Plugging Point) 

D 4629 Trace Nitrogen in Liquid Petroleum Hydrocarbons by Syringe/Inlet 

Oxidative Combustion and Chemiluminescence Detection 

D 5191 Vapor Pressure of Petroleum Products (Mini Method) 

D 5291 Instrumental Determination of Carbon, Hydrogen, and Nitrogen in 

Petroleum Products and Lubricants 

D 6078 Standard Test Method for Evaluating Lubricity of Diesel Fuels by the 

Scuffing Load Ball-on-Cylinder Lubricity Evaluator (SLBOCLE) 

D 6217 Standard Test Method for Particulate Contamination in Middle 

Distillate Fuels by Laboratory Filtration 

Christina Planc — determination of glycerides 

Total Fatty Acids 

Carbon, Hydrogen, Nitrogen, Oxygen Analysis 

Gas Chromatographic Analysis of Fatty Acids 

Properties of Biodiesels 

Throughout the following, values from ASTM D 975 — Standard Specification for Diesel Fuel 

Oils — are included in the discussion of test results when they are available as a reference for 

comparison. For some tests, the measured values for a low sulfur 2D diesel is included; these 

values are from the testing conducted on diesel-biodiesel mixtures covered in the following 

section. 

The majority of the testing was conducted by System Lab Services, a division of Williams Pipe 

Line Company (Kansas City, KS). Galbraith Laboratories, Inc. (Knoxville, TN) conducted the 

carbon, hydrogen, nitrogen, oxygen analysis, and Phoenix Chemical Laboratory, Inc. (Chicago, 

IL) conducted the phosphorus, total fatty acids, fatty acid analysis, and retested electrical 

conductivity. 

ASTM D 86 — Distillation of Petroleum Products (Table 3) produces a picture of the volatility 

characteristics of the petroleum product being tested. Fuels with similar distillation 

characteristics indicate that the fuels will have similar automotive equipment performance. 

The boiling ranges of the biodiesels are within a fairly limited range, around 600-675°F. It is at 

the upper end of the range of diesel. This may be related to the increased formation of coke 

(also indicated by Ramsbottom Carbon Residue, ASTM D 524). The higher boiling range 

(indicating a greater amount energy required to vaporize the biodiesels), results in a larger 

soluble organic fraction (SOF) in the emissions of biodiesel-fueled engines; testing by others 

has shown that these emissions are composed mostly of unburned biodiesel. 

10 
This distillation test serves as a indication for the fuel composition (as do other tests), which is 

normally difficult to obtain for diesel. Biodiesel differs in comparison to diesel because it is a 

"manufactured" fuel, and can be assessed with fatty acid composition. 

Diesel that meets D 975 (Grade 2-D and 2-D Low Sulfur) has a 90% distillation fraction between 

282°C and 338°C (540°F–640°F). The test results indicated that all but one of the biodiesels 

were above the maximum value; one was 1°C below, while the rest went up to 16°C above the 

maximum. For D 975 to be used with biodiesel, it would need to be amended for biodiesel only, 

based on these results. 

Table 3. Test Results for ASTM D 86 — Distillation of Petroleum Products 

Edible Inedible LFFA HFFA 

Observation Canola Tallow Tallow Yellow Yellow 

Point Soy ME ME Lard ME ME ME Grease ME Grease ME 

IBP, °F 613 600 580 616 611 624 594 

10%, °F 643 615 612 634 631 633 623 

20%, °F 649 628 616 637 634 635 627 

50%, °F 654 636 624 646 639 640 632 

90%, °F 669 645 638 665 658 655 647 

EP, °F 673 671 670 682 675 665 667 

IBP, °C 323 316 304 324 322 329 312 

10%, °C 340 324 322 334 333 334 328 

20%, °C 343 331 324 336 334 335 331 

50%, °C 346 336 329 341 337 338 333 

90%, °C 354 341 337 352 348 346 342 

EP, °C 356 355 354 361 357 352 353 

Recovery, ml 98 99 98.5 98.2 99 99.5 99 

Residue, ml 1.1 0.5 0.5 1.8 0.4 0.4 0.7 

Loss, ml 0.7 0.5 1 0 0.6 0.1 0.3 

ASTM D 93 — Flash-Point by Pensky-Martens Closed Cup Tester (Table 4) measures the 

lowest temperature at which application of the test flame causes the vapor above the sample to 

ignite. It is used to assess the overall flammability hazard of a material. Specifically, flash point 

is used in safety regulations to define "flammable" and "combustible" materials. Higher values 

indicate materials that are less likely to ignite accidentally. A typical value for Number 2 diesel is 

70°C, which is considered safe under normal conditions; D 975 requires a minimum of 52°C 

(126°F). The biodiesels would be considered significantly safer with temperatures between 

128°C and 167°C. 

11 
Table 4. Test Results for ASTM D 93 — Flash-Point by Pensky-Martens Closed Cup Tester 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

Flash Point, °F 333 326 263 344 276 320 297 

Flash Point, °C 167 163 128 173 136 160 147 

ASTM D 97 — Pour Point of Petroleum Products (Table 5) measures the lowest temperature 

at which the oil is observed to flow. It is important because this defines the lowest temperature 

at which the fuel can still be moved, before it has gelled. Fuels with high pour points are more 

difficult to use in areas with lower temperatures because the fuel must be kept warm by some 

method, e.g., electric heaters with insulated tanks. All the biodiesels have significantly higher 

pour points compared to diesel; over 20°C higher or more. The animal and yellow grease 

feedstocks resulted in significantly higher values due to the higher proportion of saturated fatty 

acids. 

Table 5. Test Results for ASTM D 97 — Pour Point of Petroleum Products 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 2D 

Soy ME ME Lard ME ME ME Grease ME Grease ME Diesel 

Pour Pt, °F 30 25 52 56 46 54 46 -17 

Pour Pt, °C -1 -4 11 13 8 12 8 -27 

ASTM D 130 — Detection of Copper Corrosion from Petroleum Products by the Copper

Strip Tarnish Test (Table 6) measures the degree to which the fuel can have a corroding effect 

on various metals. The values obtained with each of the biodiesels are the lowest level of 

corrosiveness, and indicate that corrosion would not be considered a problem (in lieu of any 

specific information). The value of 1A is the lowest indication on the defined scale for this test. It 

should be noted that high levels of free fatty acids or residual levels of acids may results in 

lower values for this test. Because of this, tests like D 664 — Acid Number should be used to 

ensure that the biodiesel does not have those components which would mask the true values of 

this test. D°975 permits a maximum corrosion rating of 3; biodiesel easily meets this diesel 

requirement. 

Table 6. Test Results for ASTM D 130 — Detection of Copper Corrosion 

from Petroleum Products by the Copper Strip Tarnish Test 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

1A 1A 1A 1A 1A 1A 1A 

12 
ASTM D 240 — Heat of Combustion of Liquid Hydrocarbon Fuels by Bomb Calorimeter 

(Table 7) is a measure of the energy available from the fuel. The heat of combustion for Number 

2 diesel is around 18,600 Btu/lb; each of the biodiesels vary from 0.6% below to 0.5% above 

the average (17,161 Btu/lb), which is lower than the diesel by 7.7%. Less energy would be 

carried in weight-constrained applications. When combined with the specific gravity, the lower 

heat of combustion results in a lower volumetric fuel efficiency (126,000 Btu/gal vs. 132,000 

Btu/gal). 

Table 7. Test Results for ASTM D 240 — Heat of Combustion of 

Liquid Hydrocarbon Fuels by Bomb Calorimeter, Btu/lb 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

17153 17241 17165 17144 17061 17215 17154 

ASTM D 445 — Kinematic Viscosity of Transparent and Opaque Liquids (Table 8) 

measures the flow resistance of the fuel, e.g., the time for a volume of liquid to flow under 

gravity through a calibrated glass capillary viscometer. Viscosity is important to diesels and 

biodiesels because it impacts the operation of components such as the fuel pump. Higher 

viscosity interferes with injector operation, resulting in poorer atomization of the fuel spray, and 

has been associated with increased engine deposits. If engines are expected to use higher 

fractions of biodiesel (instead of the 20% in B-20), they would benefit from redesigned injectors 

that would accommodate the higher viscosity to improve spray patterns and atomization. All the 

biodiesels have viscosities significantly higher than diesel. Because of the high values, 

biodiesels would be expected to have problems in this area on diesel engines, if measures 

(such as blending with diesel) are not taken. Acceptable values in D 975 are from a minimum of 

1.9 to a maximum of 4.1; biodiesels would not be able to meet these requirements. The 

significantly higher value of the Low Free Fatty Acid Yellow Grease Biodiesel is probably a 

result of the problems in processing, and would not be expected in general. This is also 

indicated because of the lower value of the High Free Fatty Acid Yellow Grease Biodiesel. 

Table 8. Test Results for D 445 — Kinematic Viscosity of Transparent and Opaque Liquids 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 2D 

Soy ME ME Lard ME ME ME Grease ME Grease ME Diesel 

Visc, cSt 4.546 4.63 4.85 4.908 4.93 5.62 4.66 2.45 

ASTM D 482 — Ash from Petroleum Products (Table 9) measures the amount of ash left 

after a sample is burned. The presence of ash may indicate undesirable impurities or 

contaminants. As such, it provides one measure of the suitability of a product for a given 

application. Both the low and high free fatty acid yellow grease methyl esters produced a 

significant amount of ash. Specifically for use with biodiesels, this can indicate the presence of 

processing catalysts remaining in the fuel, possibly indicating that additional cleanup was 

needed. The maximum acceptable value for diesel meeting D 975 requirements is 0.01%, which 

should be easily met with most of the biodiesels. The higher values for both the yellow grease 

13 
biodiesels (which were produced by two different groups) may indicate that yellow grease 

processing needs are greater, or that greater ash is simply inherent in that biodiesel. 

Table 9. D 482 — Ash from Petroleum Products 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

Ash, % 0 0.003 0 0.001 0 0.01 0.04 

ASTM D 524 — Ramsbottom Carbon Residue of Petroleum Products (Table 10) determines 

the amount of carbon residue left after evaporation and pyrolysis of an oil, indicating its relative 

propensity to form coke. It is a potential indicator of the likelihood that a fuel would form deposits 

from carbon in an engine's combustion chamber. However, experience with additives has 

shown that this is not an absolute indicator. Specifically, some detergent additives contribute to 

ash formation but generally reduce the tendency of the oil to form deposits. The tendency of 

biodiesels to act as a solvents (resulting in plugging of fuel filters with residue when first 

introduced to a fuel system previously run on diesel) may be similar to detergent additives. 

However, use of biodiesels has been associated in the past with forming deposits on engine 

parts. These results indicate that the canola, animal, and yellow grease biodiesels are more 

likely to form deposits than the soy biodiesel. Given that deposits have occurred with soy 

biodiesel, it would be expected that engines using the others would be more likely to form 

deposits. (The value for the edible tallow methyl ester could not be determined by Williams Lab, 

for unspecified reasons.) The D 975 maximum of 0.35% can be easily met by the biodiesels. 

Table 10. Test Results for D 524 — Ramsbottom Carbon Residue of Petroleum Products 

Edible Inedible LFFA HFFA 

Canola Lard Tallow Tallow Yellow Yellow 

Soy ME ME ME ME ME Grease ME Grease ME 

Carbon Residue, % 0.01 0.04 0.04 N/A 0.08 0.04 0.05 

ASTM D 613 — Cetane Number of Diesel Fuel Oil (Table 11) is a measure of the fuel's 

ignition delay. Higher Cetane numbers indicate shorter times between the injection of the fuel 

and its ignition. Higher numbers have been associated with reduced engine roughness and with 

lower starting temperatures for engines. 2D diesel's Cetane numbers are in the range of 40-50; 

the biodiesels all have higher values, so they would tend to improve operation of the engine with 

respect to pure diesel (based on this value alone). The inedible tallow's value is higher than the 

others, but may be as low as it is because of early production problems. Table 11a contains the 

results from Williams Lab, while Table 11b contains the results from CSM. There is no clear 

pattern between the results, or a reasonable explanation for the differences; however, the 

results for soy ME from CSM are more in-line with expected values. The minimum acceptable 

Cetane of 40 from D 975 is met by the biodiesels. 

14 
Table 11a. Test Results for ASTM D 613 — Cetane Number of Diesel Fuel Oil 

(results from WIlliams Lab) 

Edible Inedible LFFA HFFA 2D 

Soy Canola Lard Tallow Tallow Yellow Yellow Diesel 

ME ME ME ME ME Grease ME Grease ME 

Cetane No. 59 53.9 N/A 64.8 54.3 52.2 53.2 47 

Table 11b. Test Results for ASTM D 613 — Cetane Number of Diesel Fuel Oil 

(results from CSM) 

Soy

ME 

Canola 

ME 

Lard 

ME 

Edible 

Tallow 

ME 

Inedible 

Tallow 

ME 

LFFA 

Yellow 

Grease ME 

HFFA 

Yellow 

Grease ME 

Cetane No. 47.2 55 63.6 62.9 61.7 57.8 52.9 

ASTM D 664 — Acid Number of Petroleum Products by Potentiometric Titration (for dark, 

opaque liquids) (Table 12) determines the acidic or basic constituents in petroleum products 

and lubricants. For biodiesels, the acid number is an indicator of the quality of the product. 

Specifically, it detects the presence of any unreacted fatty acids still in the fuel, or of any acids 

that were used in processing. This is also an indication of the condition of the stability of the 

fuel, because the acid number increases as the fuel ages. 

Table 12. Test Results for ASTM D 664 — Acid Number of 

Petroleum Products by Potentiometric Titration 

Edible Inedible LFFA HFFA 

Canola Lard Tallow Tallow Yellow Yellow 

Soy ME ME ME ME ME Grease ME Grease ME 

Acid No., mg KOH/g 0.32 0.13 0.76 0.32 0.44 0.41 0.2 

ASTM D 971 — Interfacial Tension of Oil Against Water by the Ring Method (Table 13) 

covers the measurement of the interfacial tension of mineral oils against water, under 

nonequilibrium conditions. This has been shown to reliably indicate the presence of hydrophilic 

compounds. The missing readings could not be obtained by Williams Lab due to the 

"consistency of the samples". 

Table 13. Test Results for ASTM D 971 — Interfacial Tension 

of Oil Against Water by the Ring Method 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

11.32 15.52 12.19 31.74 N/A N/A N/A 

15 
ASTM D 1091 — Standard Test Methods for Phosphorus in Lubricating Oils and 

Additives (Table 14) covers the determination of phosphorus in unused lubricating oils, 

lubricating oil additives, and their concentrates. The methods that determine the amount of 

phosphorus are independent of the type of phosphorus compounds present, because all are 

converted to orthophosphate ions during analysis. In all cases, the amount of phosphorus 

present was below detectable limits of 0.02 wt %. The other phosphorus test conducted, 

D 3231, confirmed the low values that were identified by this test. 

Table 14. Test Results for ASTM D 1091 — Standard Test Methods 

for Phosphorus in Lubricating Oils and Additives, weight percent 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

< 0.02 < 0.02 < 0.02 < 0.02 < 0.02 < 0.02 < 0.02 

ASTM D 1094 — Water Reaction of Aviation Fuels (Table 15) determines the presence of 

water-miscible components in aviation gasoline and turbine fuels. For biodiesels, it would 

indicate the presence of relatively large quantities of partially water soluble contaminants such 

as surfactants. It may indicate incomplete cleanup at the end of production. Nothing was 

indicated in this test, suggesting that there were no contaminants, either left from the processing 

or otherwise. (N/D = not detectable) 

Table 15. Test Results for ASTM D 1094 — Water Reaction of Aviation Fuels 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

N/D N/D N/D N/D N/D N/D N/D 

ASTM D 1160 — Distillation of Petroleum Products at Reduced Pressure (Table 16) is an 

alternative procedure for determining the volatility characteristics of a petroleum product. ASTM 

acknowledges that these results are not directly comparable to the results from D86 (see 

above). This procedure accommodates products that decompose when distilled at atmospheric 

pressure. 

16 
Table 16. Test Results for ASTM D 1160 — Distillation of 

Petroleum Products at Reduced Pressure 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

IBP, °F 658 658 629 628 606 650 616 

5%, °F 662 662 648 646 642 664 650 

10%, °F 663 663 650 648 648 664 653 

20%, °F 665 663 652 652 653 667 656 

30%, °F 666 663 653 656 655 667 659 

40%, °F 667 664 655 660 659 670 660 

50%, °F 669 664 659 662 662 670 660 

60%, °F 670 664 661 666 665 672 663 

70%, °F 671 666 664 669 667 674 665 

80%, °F 674 668 669 674 670 678 668 

90%, °F 687 672 672 680 678 687 673 

95%, °F 849 685 679 689 695 720 681 

EP, °F 883 814 768 793 895 902 832 

IBP, °C 348 348 332 331 319 343 324 

5%, °C 350 350 342 341 339 351 343 

10%, °C 351 351 343 342 342 351 345 

20%, °C 352 351 344 344 345 353 347 

30%, °C 352 351 345 347 346 353 348 

40%, °C 353 351 346 349 348 354 349 

50%, °C 354 351 348 350 350 354 349 

60%, °C 354 351 349 352 352 356 351 

70%, °C 355 352 351 354 353 357 352 

80%, °C 357 353 354 357 354 359 353 

90%, °C 364 356 356 360 359 364 356 

95%, °C 454 363 359 365 368 382 361 

EP, °C 473 434 409 423 479 483 444 

Recovery, % 97 99 99 98 99 99 99 

Residue + Loss, % 3 1 1 0.2 1 1 1 

ASTM D 1298 — Density, Relative Density (Specific Gravity), or API Gravity of Crude 

Petroleum and Liquid Petroleum Products by Hydrometer Method (Table 17) is a measure 

of the specific gravity of the biodiesels. They are about 3.5% higher than 2D diesel, which was 

not considered significant by Williams Labs. 

Table 17. Test Results for D 1298 — Specific Gravity - by Hydrometer Method 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

0.8877 0.8811 0.8762 0.8708 0.8767 0.8789 0.8767 

17 
ASTM D 1322 — Smoke Point of Kerosene and Aviation Turbine Fuel (Table 18) measures 

the maximum flame height that can be achieved without smoking. This test involves soaking a 

wick in the sample, then burning the wick. Because of the characteristics of the biodiesels, there 

were problems getting the prescribed wicks to absorb biodiesel to be burned, and once soaked, 

they did not burn well. (N/A indicates not available). This result may have been expected, 

because the test had been formulated for lighter fuels. 

Table 18. Test Results for ASTM D 1322 — Smoke Point of 

Kerosene and Aviation Turbine Fuel 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

N/A N/A N/A N/A N/A N/A N/A 

ASTM D 1796 — Water and Sediment in Fuel Oils by the Centrifuge Method (Laboratory

Procedure) (Table 19) determines the amount of water and sediment in fuel oils using a 

centrifuge. The presence of either water or sediment in biodiesel can indicate incomplete 

washing or filtering. The relatively large amount in the lard methyl ester indicated problems in 

processing the lard into methyl ester, in part due to the large amount of sediment in the lard 

which is normally not an issue for users of lard. Chemol indicated that additional filtering would 

have eliminated it; in a commercial process, this may incur additional expense compared to the 

other feedstocks. Although the lard ME was above the acceptable value, in discussions with 

NREL it was decided to continue to use it. 

Related to this is a note from Industrial Uses of Rendered Fats and Oils, Vol. 3 Edible Oil and 

Fat Products, Products and Application Technology, in Bailey's Industrial Oil and Fat Products, 

Fifth Ed., ed. Y.H. Hui, 1996, John Wiley and Sons: 

"Some metalworking formulators have noted 'fallout' problems with methyl lardate and 

methyl tallowate if their products are stored in drums or tanks without agitation, 

especially in cooler weather. Over time, the saturated fatty acid esters tend to crystallize 

and settle, leaving a cloudy or opaque substance in the bottom of the storage container. 

In sample bottles, this settled opaque material can appear to be as much as 50% of the 

volume of the total sample. 

It should be noted that the saturated fractions are a natural portion of the product and 

that this fallout is a natural characteristic of the product. Some users have requested 

methyl lardate with lower levels of fallout or no fallout. In an attempt to provide this 

product, manufacturers have blended certain crystal inhibitors..." 

Past experience with biodiesel, including soy biodiesel, has indicated that visible sediments can 

form, especially if the temperature drops below 45°F; this is also true if the biodiesel is mixed 

with cold diesel. Heating the fuel above 100°F causes the solids to go completely back into 

solution. The sediment would be measured by D 1976, so any samples that were subjected to 

lower temperatures should be heated to dissolve the crystallized "sediment", and any fuel 

should be kept at higher temperatures to keep “sediment” from forming before testing. One of 

the possible reasons for the high value for the lard methyl ester was the presence of this 

sediment. 

18 
The current biodiesel standard ASTM PS 121 recommends ASTM D 2709 — Standard Test 

Method for Water and Sediment in Middle Distillate Fuels by Centrifuge — for detecting water 

and sediment. This method has been designed specifically for fuels with the viscosities and 

densities of the various grades of diesels, including biodiesel. D 1796 is intended for higher 

viscosity fuel oils (per the D 2709 scope). 

Table 19. Test Results for ASTM D 1796 — Water and Sediment in Fuel Oils 

by the Centrifuge Method (Laboratory Procedure) 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

Sediment, % 0 0 0.6 0.05 0 0 0.03 

ASTM D 1959 — Iodine Value of Drying Oils and Fatty Acids (Table 20) measures the 

amount of iodine required to saturate the olefinic bonds. The iodine value is an indicator of the 

unsaturation of the fuel, which has been linked with formation of engine deposits and problems 

in storing the fuel. It has been suggested that values over 115 may be unacceptable; the 

biodiesels easily meet this requirement. The problems with this test has resulted in ASTM 5550 

being selected as the preferred method, after this project was running. 

Table 20. Test Results for ASTM D 1959 — Iodine Value of Drying Oils and Fatty Acids 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

Iodine, ppm 2.98 66 53 4.68 17.9 16.8 16.8 

ASTM D 2274 — Standard Test Method for Oxidation Stability of Distillate Fuel Oil 

(Accelerated Method) (Table 21) measures the inherent stability of middle distillate petroleum 

fuel under accelerated oxidizing conditions. In the method, the fuel is aged at 95°C (203°F) for 

16 hours while oxygen is bubbled through the sample at a rate of 3 L/h. The sample is then 

cooled to room temperature before filtering to obtain the filterable insolubles. Adherent 

insolubles are removed from the oxidation cell with trisolvent, which is evaporated to determine 

the quantity. The sum of the two is the total insolubles. Higher numbers indicate that more of the 

fuel has oxidized, and that it is less stable than a sample that produces a lower value. The 

biodiesels were inherently less stable than the 2D diesel sample that was used as a base (and 

the 0% value for the biodiesel/diesel mixtures reported in the next section). This is in agreement 

with previous experience, specifically that biodiesel does not age well, degrading faster than 

diesel. It is interesting to note that the iodine value (D 1959) shown above shows similar results, 

i.e., the canola, lard, and inedible tallow methyl esters have significantly higher numbers than 

the soy and edible tallow methyl esters. However, the values for the yellow grease methyl esters 

do not show this pattern. 

19 
Table 21. Test Results for ASTM D 2274 — Standard Test Method for 

Oxidation Stability of Distillate Fuel Oil (Accelerated Method), mg/100 mL 

Edible Inedible LFFA HFFA 2D 

Canola Lard Tallow Tallow Yellow Yellow Diesel 

Soy ME ME ME ME ME Grease ME Grease ME 

16.0 44.9 72.0 8.1 41.0 6.2 8.2 2.3 

ASTM D 2500 — Cloud Point of Petroleum Products (Table 22) measures the temperature at 

which wax crystals or other small crystals of fuel (in the case of biodiesel) begin to form in the 

liquid causing a haziness as the sample is cooled. It is an indicator of the utility of a petroleum 

oil for some applications. In the case of biodiesel, the haze is made up of crystallized fuel 

molecules, specifically crystallized stearic and/or palmitic methyl esters. Using a product below 

its cloud point may reduce the lubricating properties, and may plug filters. For biodiesel, the 

settled material may not cause lubrication problems, but the remaining liquid may have lower 

properties relative to the fully mixed fuel. 

In D 975, the cloud point is referenced but not specified by a single number. Instead, it 

references the tenth percentile of the ambient temperature for the area being used. Use of flowimprovement additives modifies these values. However, using the temperatures shown for the 

states in the standard (continental U.S.), 18 states are at or below the lowest cloud point in 

October, while over 41 of the 48 states are at or lower for November through March (Nov-45, 

Dec-46, Jan-48, Feb-46, Mar-42). This implies that any of the biodiesels would have problems 

with clouding in most states during these times. Blending with diesel would lessen this problem, 

as would the use of additives. 

Table 22. Test Results for ASTM D 2500 — Cloud Point of Petroleum Products 

Edible Inedible LFFA HFFA 2D 

Canola Lard Tallow Tallow Yellow Yellow Diesel 

Soy ME ME ME ME ME Grease ME Grease ME 

Cloud Pt, °F 36 27 57 68 73 108 46 0 

Cloud Pt, °C 2 -3 14 20 23 42 8 -18 

ASTM D2622 — Test Method for Sulfur in Petroleum Products by X-Ray Spectrometry

(Table 23) measures the amount of sulfur. As part of the fuel, sulfur is converted to sulfur oxides 

and sulfuric acid, affecting the emissions of the engine. The lack of detectable sulfur in the 

biodiesels would result in a reduction in the particulate emissions, in comparison to diesel. 

(<DL = below detectable limits). Subsequent to this project, ASTM D 5453 — Total Sulfur by 

Ultraviolet Florescence — has been adopted for testing biodiesel because of its ability to detect 

lower sulfur levels than D 2622. The maximum value in D 975 for low-sulfur diesel 1D & 2D is 

0.05 % mass. Based on the inability to detect at a level lower than the D 975 requirement, which 

references D 2622 for detecting sulfur, these biodiesels would meet D 975. 

20 
Table 23. Test Results for D 2622 — Test Method for Sulfur 

in Petroleum Products by X-Ray Spectrometry 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

Sulfur, wt% <DL <DL <DL <DL <DL <DL <DL 

ASTM D 2624 — Electrical Conductivity of Aviation and Distillate Fuels (Table 24) 

indicates the conductivity of a fuel. The conductivity is a measure of the ability of a fuel to 

dissipate any electrical charge that has been generated during pumping and filtering. No 

problems are expected from any of the biodiesels. (The retested value was required because of 

the extremely high value initially obtained.) 

Table 24. Test Results for ASTM D 2624 — Electrical Conductivity 

of Aviation and Distillate Fuels 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

Conductivity, pS/m 181 147 122 809 264 663 >9000 

(retested) 470 

ASTM D 3231 — Standard Test Method for Phosphorus in Gasoline (Table 25) indicates the 

amount of phosphorus. This method was developed to be able to detect the levels of 

phosphorus, because it will damage catalytic converters used in automotive emission control 

systems. It detects levels of phosphorus lower than the test reported in a previous section 

(D 1091). 

Table 25. Test Results for ASTM D 3231 — Standard Test Method 

for Phosphorus in Gasoline, ppm 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

20.0 13.3 18.4 44.0 19.6 18.7 28.0 

ASTM D 3241 — Thermal Oxidation Stability of Aviation Turbine Fuels (JFTOT Procedure) 

(Table 26) establishes a procedure to rate the tendencies of gas turbine fuels to form deposits 

within the fuel system, e.g., heated surfaces. When used with biodiesels, it indicates the same 

tendency when the fuel would come into contact with components such as valves, pistons, and 

cylinders. Only the edible tallow methyl ester showed up as higher than the minimum rating 

(tube rating); modifications in processing should be able to improve its rating. 

21 
Table 26. Test Results for ASTM D 3241 — Thermal Oxidation Stability 

of Aviation Turbine Fuels (JFTOT Procedure) 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

Pressure drop 1 0 0 2 0 0 4 

Tube rating 1 1 1 4P 1 1 1 

ASTM D 3242 — Acidity in Aviation Turbine Fuel (Total Acid Number) (Table 27) describes 

the procedure used to determine the acidity of aviation turbine fuel. It provides a measure of the 

acidity in biodiesel, as used here, and may indicate the quality of the biodiesel in a manner 

similar to D 664. Comparison with the values of the D 664 testing (Table 12) shows a high 

correlation between the two sets. Although there are differences in values, the relative position 

of each remained the same. Further study is required to identify whether the differences in value 

are due to a property of the biodiesels, or are a result of differences in technique or reporting. 

Table 27. Test Results for ASTM D 3242 — Acidity in 

Aviation Turbine Fuel (Total Acid Number) 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

Neutralization 

Number, 0.322 0.12 0.76 0.35 0.646 0.492 0.238 

mg KOH/g 

ASTM D 4539 — Filterability of Diesel Fuels by Low-Temperature Flow Test (LTFT) (Cold 

Filter Plugging Point), also known as IP 309, (Table 28) identifies the temperature at which wax

or other crystals (first observed at the Cloud Point) can stop the flow of fuel by plugging the 

engine's fuel filter. The biodiesels have significantly higher temperatures than diesel, a minimum

of 16°C above the diesel value. The lard and tallow biodiesels are the highest (as they were for

cloud point and pour point).

Table 28. Test Results for D 4539 — Filterability of Diesel Fuels by 

Low-Temperature Flow Test (LTFT) (Cold Filter Plugging Point) 

Edible Inedible LFFA HFFA 2D 

Canola Tallow Tallow Yellow Yellow Diesel 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

CFPP, °F 28 24 52 58 50 52 34 -4 

CFPP, °C -2 -4 11 14 10 11 1 -18 

22 
ASTM D 4629 — Trace Nitrogen in Liquid Petroleum Hydrocarbons by Syringe/Inlet 

Oxidative Combustion and Chemiluminescence Detection (Table 29) indicates the amount 

of nitrogen present in the fuel. It could indicate material left from processing, and would be a 

measure of the quality. The edible tallow was high as might have been expected based on the 

comments about processing. The reason for the relatively high levels from the high free fatty 

acid yellow grease could also be processing, or incomplete cleanup, although the other tests did 

not seem to indicate this. 

Table 29. Test Results for ASTM D 4629 — Trace Nitrogen in Liquid Petroleum Hydrocarbons 

by Syringe/Inlet Oxidative Combustion and Chemiluminescence Detection 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

Total Nitrogen, ppm 3 0 3 77 5 4 48 

ASTM D 5191 — Vapor Pressure of Petroleum Products (Mini Method) (Table 30) is a 

measurement of the vapor pressure of the petroleum. The test results indicated that none of the 

biodiesels had a measurable vapor pressure at room temperature. This is in agreement with 

what was observed with the two distillation tests, D 86 and D 1160, and with the flash point test, 

D 93. The high temperatures recorded for those tests indicated that essentially no vapor would 

be expected at lower temperatures. (N/D = no vapor pressure detected) 

Table 30. Test Results for ASTM D 5191 — Vapor Pressure 

of Petroleum Products (Mini Method) 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

N/D N/D N/D N/D N/D N/D N/D 

ASTM D 5291 — Instrumental Determination of Carbon, Hydrogen, and Nitrogen in 

Petroleum Products and Lubricants (Table 31) results in a breakdown of the carbon, 

hydrogen, and nitrogen in a fuel sample. Because of the small amounts of nitrogen in the 

biodiesels, as shown in D 4629 testing, no values were reported for this test. Comparing the 

carbon and hydrogen shows that the vegetable oil-derived methyl esters (soy and canola) are 

less hydrogenated than the others, which are all about 5% higher. This is in agreement with the 

cloud point (D 2500), pour point (D 97), and cold filter plugging point (D 4539), because more 

hydrogenated oils have higher melting points. 

23 
Table 31. Test Results for ASTM D 5291 — Instrumental Determination of 

Carbon, Hydrogen, and Nitrogen in Petroleum Products and Lubricants 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

Carbon, wt% 77.95 77.68 77.36 77.07 75.88 76.2 76.03 

Hydrogen, wt% 11.98 12.25 12.50 12.50 12.69 12.46 12.50 

ASTM D 6078 — Standard Test Method for Evaluating Lubricity of Diesel Fuels by the 

Scuffing Load Ball-on-Cylinder Lubricity Evaluator (SLBOCLE) (Table 32) is an indication 

of the lubricating quality of the fuel. It is reported as the weight that can be maintained on a 

lubricating film in a SLBOCLE test rig Higher lubricity had been linked with less wear, resulting 

in longer engine component life. In all but one case, the biodiesels essentially doubled the 

weight that could be maintained. This supports the benefit claims of biodiesel advocates in 

improving the life of diesel engines. The soy methyl ester is almost double the recommended 

minimum of 3100 by the Engine Manufacturers Association, and may not be higher only for this 

batch. 

Table 32. Test Results for ASTM D 6078 — Standard Test Method for Evaluating Lubricity 

of Diesel Fuels by the Scuffing Load Ball-on-Cylinder Lubricity Evaluator (SLBOCLE) 

Edible Inedible LFFA HFFA 2D 

Canola Lard Tallow Tallow Yellow Yellow Diesel 

Soy ME ME ME ME ME Grease ME Grease ME 

wt, g 6050 >7000 >7000 >7000 >7000 >7000 >7000 3600 

ASTM D 6217 — Standard Test Method for Particulate Contamination in Middle Distillate 

Fuels by Laboratory Filtration (Table 33) indicates the amount of contaminants in fuels by 

weighing the residue left after filtering the product. The original test for particulates planned for 

biodiesel was D 2276. Then D 5452 had been established from the laboratory portion of D 2276 

as a separate standard. However, the thickness of the biodiesel resulted in extremely long 

filtration times, so the test was switched to D 6217, which had been established as the middle 

distillate equivalent. D 6217 is similar to D 1796, indicating contaminants in the fuel, but could 

be significantly different in value because this test ignores the presence of water. Because of 

the sensitivity, it is more likely to detect particulates in very small quantities than D 1796. 

Alternatively, biodiesel has been known to dissolve test filters, and so may have produced the 

results shown, though nothing was mentioned by the lab. 

Table 33. Test Results for ASTM D 6217 — Standard Test Method for 

Particulate Contamination in Middle Distillate Fuels by Laboratory Filtration 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

mg/L 2.56 11 789 74 1,154 N/A 0 

24 
The Christina Planc method is a more sensitive test than other techniques to detect the 

presence of glycerides (Table 34). It had been adopted by the biodiesel industry as a method of 

determining the quality of the biodiesel. The presence of unexpectedly large amounts of 

triglycerides after transesterification would indicate that the process had not been complete. As 

noted in the previous section, it also can be used to identify when further cleanup of the methyl 

ester is required. The high free fatty acid yellow grease methyl ester shows either the most 

conversion or the greatest cleanup, and is probably a result of the second supplier's process 

more than an inherent characteristic. The reason for the higher values for the soy and low free 

fatty acid yellow grease methyl esters is unknown; the results of the other tests do not 

necessarily correlate with these. 

Table 34. Test Results for Christina Planc method 

Edible Inedible LFFA HFFA 

Canola Lard Tallow Tallow Yellow Yellow 

Soy ME ME ME ME ME Grease ME Grease ME 

Free Glycerin 0.001 0.001 0 0 0 0 0.004 

Monoglycerides, wt% 0.87 0.738 0.563 0.320 0.572 0.856 0.250 

Diglyrcerides, wt% 1.358 0.02 0.093 0.120 0.070 0.233 0.076 

Triglycerides, wt% 3.542 0.01 0.005 0.014 0 0 0 

Total Glycerin, wt% 0.798 0.196 0.16 0.102 0.159 0.256 0.080 

Total Fatty Acids (Table 35) is the analysis of the amount of fatty acids present in the 

biodiesel. It is an indication of the conversion efficiency of the original feedstock; these were 

considered good by Williams Labs. 

Table 35. Total Fatty Acids, % 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

94.2 92.3 94.4 90.6 90.6 94.3 90.9 

Carbon, Hydrogen, Nitrogen, Oxygen Analysis (Table 36) results described below were 

determined by Organic Elemental Analysis. It is obtained by flash combustion and GC 

separation. The values are in relative agreement with the values obtained by D 5291, with the 

added benefit of obtaining oxygen. 

Table 36. Carbon, Hydrogen, Nitrogen, Oxygen Analysis 

Edible Inedible LFFA HFFA 

Canola Tallow Tallow Yellow Yellow 

Soy ME ME Lard ME ME ME Grease ME Grease ME 

Carbon, wt % 76.88 76.84 76.01 75.96 76.40 76.39 76.56 

Hydrogen, wt % 11.67 12.03 12.11 12.40 12.46 12.26 12.15 

Nitrogen, wt % <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 

Oxygen, wt % 11.40 10.79 11.60 11.31 11.61 11.15 11.72 

25 
Gas Chromatographic Analysis of Fatty Acids (Table 37) indicates the composition of each 

of the biodiesels. The largest fractions of fatty acids for each of the biodiesels is a potential 

indication of the rest of the properties. The "unknown" entries represent isomers of the fatty 

acids that the lab did not have a standard reference for and so could not be listed, but are 

understood to be connected with the following listed fatty acids. 

The methyl esters follow some patterns. The soy, canola, and two yellow grease ME are mostly 

oleic and linoleic acid (C18, one and two double carbon bonds), while the two largest 

components of the lard, edible tallow, and inedible tallow ME are oleic and palmitic acid (C18, 

one C:C bond, and C16, saturated). 

Table 37. Gas Chromatographic Analysis of Fatty Acids 

Soy

ME 

Canola 

ME 

Lard 

ME 

Edible 

Tallow 

ME 

Inedible 

Tallow 

ME 

LFFA 

Yellow 

Grease ME 

HFFA 

Yellow 

Grease ME 

Lauric C12H24O2 (trace) (trace) 0.12 0.06 0.08 (trace) (trace) 

Unknown (trace) (trace) (trace) (trace) 0.05 (trace) (trace) 

Myristic C14H28O2 0.09 0.07 1.86 2.91 2.08 (trace) 1.08 

Unknown (trace) (trace) 0.09 1.57 1.18 (trace) (trace) 

Palmitic C16H32O2 10.54 5.25 24.49 24.34 23.93 11.53 17.3 

Unknown (trace) (trace) (trace) (trace) (trace) 0.18 (trace) 

Palmitoleic C16H30O2 0.13 .22 2.80 3.44 2.79 (trace) 2.23 

Unknown 0.14 .23 0.89 3.01 2.34 (trace) 0.97 

Stearic C18H36O2 3.75 2.46 14.39 19.10 19.54 13.36 9.54 

Unknown (trace) (trace) (trace) (trace) (trace) (trace) (trace) 

Oleic C18H34O2 23.18 58.09 38.32 40.23 38.54 60.67 45.28 

Unknown (trace) (trace) 0.07 0.24 0.24 12.02 (trace) 

Linoleic C18H32O2 48.92 21.79 13.44 2.58 6.43 0.62 14.48 

Unknown 7.08 6.63 0.70 0.32 0.52 (trace) 0.57 

Linolenic C18H30O2 1.16 0.41 0.33 0.33 0.32 (trace) 1.3 

Unknown 1.47 (trace) (trace) (trace) (trace) (trace) (trace) 

Arachidic C20H40O2 0.24 1.04 0.45 0.29 0.34 0.41 1.06 

Unknown 0.39 0.12 0.10 0.51 0.18 (trace) (trace) 

cis-eicosanoic 0.32 1.57 0.67 0.51 0.46 0.21 1.33 C20H38O2 

Unknown 1.76 0.80 0.86 0.36 0.62 0.49 2.58 

Behenic C22H44O2 0.12 0.37 0.18 0.05 0.06 0.32 0.75 

Unknown 0.10 (trace) (trace) (trace) (trace) (trace) 1.54 

Erucic C22H42O2 0.08 0.37 0.06 0.09 0.06 (trace) (trace) 

Unknown 0.52 0.42 0.19 0.05 0.25 (trace) (trace) 

Nervonic C24H46O2 (trace) 0.18 (trace) 0.00 (trace) 0.17 (trace) 

26 
EVALUATION OF BIODIESEL SPECIFICATION 

The specifications for acceptable biodiesels were to be reviewed as part of this project, based 

on the results of the comprehensive testing on the samples. The specifications are shown in 

Table 38. 

Table 38. Biodiesel Specifications (July 1996) 

(For pure mono alkyl esters of long chain fatty acids 

derived from renewable lipid feedstocks) 

Property ASTM Method Limits Units 

Flash Point 

Water & Sediment 

Carbon Residue, 100% sample 

Sulfated Ash 

Kinematic Viscosity, 40°C 

Sulfur 

Cetane 

Cloud Point 

Copper Strip Corrosion 

Acid Number 

Free Glycerin 

Total Glycerin 

D93 

D1796 

D5241 

D874 

D445 

D2622 

D613 

D2500 

D130 

D664 

GC2 

GG2 

100.0 min. 

0.050 max. 

0.050 max. 

0.020 max. 

1.9 — 6.5 

0.050 max. 

40 min. 

By Customer 

No. 3b max. 

0.80 max. 

0.020 max. 

0.240 max. 

°C 

vol. % 

wt. % 

wt. % 

mm2/sec (cSt) 

wt. % 

°C 

mg KOH/g 

wt. % 

wt. % 

1

 or equivalent ASTM testing method.

2

 Austrian (Christina Planc) update of USDA test method.

The first step would be identifying tests that may not be needed. 

• Flash point is an important measure and should remain a part of the specifications, because 

it ensures the safety of the fuel handlers and provides a measure of the quality of the fuel. A 

high flash point is one indication that the methyl esters have been properly washed, 

eliminating any remaining alcohols. 

• Water and Sediment is another measure of the quality of the fuel, and should remain in the 

specification. High values indicate a problem in the cleanup of the fuel, and may cause 

problems with the flow of the fuel through filters and other components. 

• The Ramsbottom Carbon Residue is an indicator of the tendency of a fuel to form engine 

deposits. Because the other fuel samples had four or more times the value of the soy 

biodiesel, and soy biodiesel has been linked with engine deposits in the past, even though 

the maximum is one-seventh the maximum specified by D 975 for diesel, further experience 

should be gained in a production environment. Experience with a number of different engine 

and injector types would assist in understanding in the direction the biodiesel maximum 

needs to be adjusted, if at all. 

27 
• Sulfated ash is a measure of the residue from oils and additives. The sulfated ash is the 

residue remaining after the sample has been carbonized, then treated with sulfuric acid and 

heated to constant weight. It is typically used to indicate the concentration of known metalcontaining additives in new oils, including barium, calcium, magnesium, zinc, potassium, 

sodium, and tin. ASTM recommends that D 482 should be used instead of D 874 for nonadditive lubricating oils; this would be closer to biodiesel. The production of biodiesel uses 

sodium, potassium, and other metallic catalysts; therefore, this test (or D 482) should 

remain in the specifications. 

• Kinematic viscosity is an important measure of the biodiesel's flow properties. Because high 

viscosity has been associated with poor atomization of the fuel spray from the injectors and 

engine deposits, viscosity should remain a part of the specification. Tracking this number 

ensures that the fuel has been processed to achieve an acceptable viscosity (i.e., as low as 

possible with the fuel), and that nothing has been left behind from the processing. 

• Sulfur is a measure of the sulfur in the fuel. The biodiesels produced as part of this project 

did not contain detectable amounts of sulfur. However, because some processing methods 

use sulfur catalysts to utilize high free fatty acid feedstocks, it should be kept in the set. 

• Cetane is a measure of the ignition delay of the fuel, and is a good indicator of the quality of 

the biodiesel. All of the biodiesels were at least 5 greater than the Cetane number of the 2D 

diesel tested and experience in the industry has shown that biodiesels are generally at the 

higher end of diesels. It should continue as part of the specifications because of its gauge of 

quality of the biodiesel. 

• Cloud point, as the highest of the three temperatures indicating the potential for flow 

problems (the other two are cold filter plugging point and pour point), should be maintained 

in the specifications. 

• Copper strip corrosion indicates the corrosiveness of the fuel on various metals. All 

measurements from the biodiesels indicated the minimum level of corrosiveness. Unless this 

test also serves as a measure of processing quality on a component that is undetected by 

others (e.g., flash point, water & sediment, Cetane number), or there is experience in the 

industry that indicates otherwise, this test is a candidate for removal from the specification. 

• Acid number is a measure of the acidic or basic constituents in a fuel. Because it is a good 

indicator of the quality of the fuel (processing or cleanup), it should remain as part of the 

specifications. 

• Free glycerin and total glycerin (by the Christina Planc method) is a good indicator as to the 

cleanup of the fuel, or of the degree of completion during the reaction. As such, it should 

remain in the specifications for biodiesel. 

In addition to reviewing the existing specifications, the question of whether any other tests 

should be included was addressed. In discussions with biodiesel providers and with testing 

laboratories, and in reviewing the purpose and focus of the complete test suite, the 

recommended set of specifications should continue to be able to qualify biodiesel acceptance. 

Other tests provide additional insight into the properties of the fuel, but it is thought that many 

could be inferred from other results, at least generally. Specifically, there is no test conducted 

that would serve as an indicator of acceptability better than the existing specifications. 

28 
COMPARISON OF BIODIESEL AND DIESEL SPECIFICATIONS 

ASTM D 975 specifies acceptable properties of diesel. The biodiesel samples produced for this 

project met most of the specifications. Their Flash Points were at least 76°C (137°F) above the 

minimum. Ash for the samples were half or less of the maximum acceptable value, except for 

the yellow grease biodiesels (which may have been due to processing and could be corrected 

now that it is known). The Ramsbottom Carbon Residue maximum of 0.35% was met by the 

biodiesels, and all but one met the biodiesel specification of 0.05%. The biodiesels all met the 

requirement of a Cetane number of 40 by at least 7. Sulfur levels in biodiesel were below 

detectable limits for the test method specified by D 975. 

However, the biodiesels have problems meeting D 975 requirements in three areas. For the 

biodiesels, the 90% distillation fraction was at or above the maximum temperature specified by 

D 975. The viscosity of all the biodiesels was above the maximum value of 4.1 centiStokes. 

Cloud Point is a problem for all of the biodiesels because the temperatures are significantly 

higher than the tenth-percentile ambient temperature specified by D 975. Because each of 

these is related to the composition of the biodiesels, D 975 may need to be changed to reflect 

this. 

Table 39 compares the biodiesel specifications with those of D 975. The applicability of these 

specifications for B20 (20% biodiesel / 80% diesel) can be considered. 

Table 39. Comparison of Biodiesel Specifications and ASTM D 975 Specifications 

Property 

Biodiesel 

Limits D 975 Limits Units 

Flash Point 

Water & Sediment 

Carbon Residue, 100% sample 

Sulfated Ash 

Kinematic Viscosity, 40°C 

Sulfur 

Cetane 

Cloud Point 

90% Distillation Fraction Temp 

Copper Strip Corrosion 

Acid Number 

Free Glycerin 

Total Glycerin 

100.0 min. 

0.050 max. 

0.050 max. 

0.020 max. 

1.9 — 6.5 

0.050 max. 

40 min. 

By Customer 

No. 3b max. 

0.80 max. 

0.020 max. 

0.240 max. 

52.0 min. 

0.35 max. 

0.010 max. 

1.9 — 4.1 

0.050 max. 

40 min. 

By Customer 

282 — 338 

°C 

vol. % 

wt. % 

wt. % 

mm2/sec (cSt) 

wt. % 

°C 

°C 

mg KOH/g 

wt. % 

wt. % 

In general, the properties of B20 would be expected to be between the pure components, and 

closer to the pure diesel values than biodiesel values. 

• For sulfur and Cetane number, the limits are the same. 

29 
• The flash point of B20 could be significantly lower than the biodiesel limit, given that diesel 

needs to be at least 52°C, compared with the 100°C biodiesel limit. In B20, the diesel 

components that produce the flash point would be present around the same temperature as 

pure diesel, indicating that the flash point of B20 would be very close to that of the diesel 

used in the mixture. 

• B20 may not meet the biodiesel carbon residue maximum, because diesel can be 7 times 

the maximum of biodiesel and still meet the D 975 specification. 

• The D 975 limit of 0.01% sulfated ash could be exceeded with B20, because the biodiesel 

maximum is twice the value of D 975. 

• Viscosity of B20 could exceed the D 975 maximum, because the biodiesel maximum is 58% 

greater than the diesel limit. 

• There is no value in the biodiesel specification for the temperature of 90% distillation 

fraction, but as noted in the discussion for D 86, biodiesel was above the maximum 

temperature for diesel in D 975. To meet D 975, most of the diesel would have to be 

vaporized, along with over 50% of the biodiesel at the maximum temperature of 338°C. 

Since the 50% distillation fraction temperatures were around the maximum temperature, it is 

possible for B20 to be outside the temperature range from D 975. 

Based on this, B20 limits would be expected to be closer to diesel limits, but could exceed the 

limitations of D 975 in those values for sulfated ash, viscosity, and distillation fraction 

temperature. B20 could fail on biodiesel specification limits in flash point and carbon residue. 

30 
--

BIODIESEL/DIESEL BLEND TESTING 

Testing Methodology 

The biodiesels used in the blended testing were the fuels produced for this program: the soy 

methyl ester, canola methyl ester, pork lard methyl ester, edible and inedible beef tallow methyl 

esters, low free fatty acid (<4%) yellow grease methyl ester, and high free fatty acid (10%) 

yellow grease methyl ester. 

It was considered important to use a diesel that would represent diesel fuel in general, and that 

could be utilized in other projects as a common baseline. To meet this requirement, IGT 

identified a suitable diesel fuel for use as a reference and as the base for mixing with the 

biodiesels. The reference fuel for this test program was certification diesel fuel obtained from 

Phillips Petroleum (Lot D434). It is the low-sulfur diesel that is currently used for testing engine 

emissions, and because of this use, is known in terms of its quality and characteristics. The 

properties of this fuel are shown in Table 40. 

Table 40. Certification Diesel Fuel Lot D-434 Properties 

Property Lot D-434 ASTM Method 

API Gravity 36.28 D-287 

Viscosity, cS 40°C 2.5 D-445 

Net Heating Value, BTU/lb 18456 D-3338 

Cetane Number 46.0 D-613 

Carbon, wt% 86.6 D-5291 

Hydrogen, wt% 13.4 D-5291 

Oxygen, wt% 0 D-5291 

Sulfur, ppm 300 D-2622 

Nitrogen, ppm D-4629 

IBP, F 353.9 D-86 

T50, F 498.7 D-86 

T90, F 583.7 D-86 

EP, F 646.4 D-86 

Aromatics, vol% 29.2 D-1319 

Olefins, vol% 2.0 D-1319 

Saturates, vol% 68.8 D-1319 

The tests that were selected for the blended fuels were the ones that were expected to vary in a 

non-intuitive fashion, or that may not be proportional with respect to blend rates. They also are 

the tests that have the most direct correlation to handling and use with diesel engines. The tests 

are shown in Table 41. 

31 
Table 41. Physical and Chemical Tests of Biodiesel Blends 

Property ASTM Method Importance 

Viscosity, mm2/s @ 40°C D 445 Fuel flow resistance; higher viscosity 

associated with poorer fuel atomization from 

injectors and increased engine deposits; 

also impacts energy requirements and wear 

of fuel pump and injectors; 

Pour Point, °C D 97 Minimum temperature above which fuel can 

be poured, i.e., is still a liquid and can be 

pumped; affecting use in cold climates 

Cloud Point, °C D 2500 Temperature at which fuel begins to cloud 

(i.e., increases in turbidity), indicating wax is 

beginning to form (potential for plugging) 

Cold Filter Plugging Point, °C D 4539 / IP 309 Temperature at which fuel will plug a fuel 

filter 

Cetane number D 613 Measure of ignition delay of a compression 

ignition fuel; higher values indicate shorter 

ignition lags, fewer deposits, lower starting 

temperatures, reduced engine roughness 

Lubricity D 6078 Measure of the lubricating quality of the fuel; 

higher values indicate better lubrication 

Oxidation Stability D 2274 Measure of change in fuel oil quality; 

indicator of "shelf life" of fuel 

The specific fuel blend fractions were selected to complement the tests that had been 

conducted on the pure biodiesels. They also took into account the range of low-concentration 

biodiesel blends (in the range of diesel fuel additives) that advocates of biodiesel emphasize are 

beneficial, and that present little possibility for unusual changes in properties once the biodiesel 

becomes the dominant component. The fractions of biodiesel that were tested were: 0.25%, 

0.50%, 1%, 3%, 5%, 10%, 20%, 35%, and 50%. In addition, the pure diesel fuel was tested to 

establish the 0% biodiesel point. 

The testing was conducted by outside agencies. The D 6078 (Scuffing Load Ball On Cylinder 

Lubricity Evaluator) tests were conducted by Engineering Test Services, and the other tests 

were conducted by Williams Lab Services. 

32 
Biodiesel/Diesel Blend Test Results 

The following tables display the results of the testing on the various biodiesel / diesel blends. 

The 0% biodiesel concentration is the test result of the pure diesel fuel, and the 100% biodiesel 

concentration has been carried from the section of the pure biodiesel test results. The 

discussion of the results is presented in the following section. 

Table 42 contains the results of the viscosity testing. 

Table 42. Biodiesel Blend Viscosity Test Results 

Biodiesel 

Concentration SME CME LME ETME ITME LYGME HYGME 

0% 2.453 2.453 2.453 2.453 2.453 2.453 2.453 

0.25% 2.505 2.461 2.453 2.453 2.453 2.453 2.453 

0.50% 2.453 2.453 2.453 2.453 2.453 2.476 2.461 

1% 2.461 2.461 2.468 2.468 2.476 2.468 2.490 

3% 2.392 2.400 2.400 2.487 2.409 2.418 2.400 

5% 2.418 2.418 2.444 2.435 2.444 2.452 2.435 

10% 2.461 2.496 2.522 2.513 2.522 2.556 2.513 

20% 2.743 2.743 2.859 2.894 2.930 3.011 2.876 

35% 2.936 2.988 3.145 3.208 3.262 3.387 3.172 

50% 3.189 3.308 3.459 3.531 3.593 3.826 3.495 

100% 4.546 4.63 4.85 4.908 4.93 5.62 4.66 

Figure 1 shows the results of the viscosity tests for each of the biodiesel blends, while Figure 2 

shows an expanded view of the 0-10% biodiesel range. Viscosity affects fuel atomization by the 

injectors, engine deposits (increased viscosities associated with increased deposits), and 

energy use (higher viscosities require more energy by the fuel pump). Figure 2 shows that, at 

low concentrations (<10%), there appears to be a moderate level of viscosity reduction between 

1% and 5%, returning back to a blend fraction-dependent mix of the two fuels' viscosity by the 

10% level. The maximum amount of reduction occurs with the soy methyl ester at 3%, with a 

total reduction of approximately 2.5%. The fact that this occurs with each of the biodiesels 

indicates that it is a general artifact, independent of any particular feedstock-derived 

characteristic. However, because the reduction is minimal and occurs in a small range, it may 

not be worthwhile to take advantage of it. 

33 
5.800 

5.300 

4.800 

4.300 

3.800 

SME 

CME 

LME 

ETME 

ITME 

LYGME 

HYGME 

3.300 

2.800 

2.300 

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 

BIODIESEL CONCENTRATION, % 

Figure 1. Biodiesel/Diesel Blend Viscosity Test 

Results 

2.600 

2.500 

SME 

CME 

LME 

ETME 

ITME 

LYGME 

HYGME 

2.400 

2.300 

0.0% 2.5% 5.0% 7.5% 10.0% 

BIODIESEL CONCENTRATION, % 

Figure 2. Biodiesel/Diesel Blend Viscosity Test Results (0–10% biodiesel blend range) VISCOSITY, cSt VISCOSITY, cSt 

34 
Table 43 shows the results from the pour point testing. 

Table 43. Biodiesel Blend Pour Point Test Results, °C 

Biodiesel 

Concentration SME CME LME ETME ITME LYGME HYGME 

0% -27 -27 -27 -27 -27 -27 -27 

0.25% -27 -21 -24 -24 -24 -24 -24 

0.50% -27 -24 -24 -24 -24 -24 -24 

1% -24 -24 -24 -21 -24 -24 -24 

3% -24 -24 -21 -21 -21 -21 -21 

5% -21 -21 -18 -18 -15 -18 -18 

10% -18 -21 -15 -12 -12 -18 -18 

20% -18 -18 -9 -9 -9 -9 -12 

35% -15 -18 0 -6 -3 -6 -6 

50% -9 -15 3 3 3 0 -3 

100% -1 -4 11 13 8 12 8 

Figure 3 shows the test results for pour point, and Figure 4 shows the expanded view of the 0%-

10% biodiesel range. Pour point, the temperature above which the fuel will pour, is important 

because it directly affects the usability of the fuel in colder climates. The high pour points of 

many of the biodiesels significantly limit their use in the pure form in cold weather. Even though 

the blends show much better pour point temperatures at lower concentrations, handling the pure 

biodiesels before mixing will require insulation and heating of the tanks to ensure that the liquid 

can be moved prior to mixing. It also affects the way in which mixing occurs, so that an 

adequate temperature of the biodiesel is maintained until thorough blending can occur. Unlike 

the viscosity results, the pour point results demonstrate a fairly rapid rise in pour point up to a 

10% concentration, at which time the trend is more linear with respect to blend fraction. This 

indicates that the presence of biodiesel, even at the low concentrations when used as a diesel 

additive, will increase the pour point of the blend by approximately 5°C. The steps that are seen 

in Figure 3 are a result of the step size when the temperature is adjusted while conducting the 

test. 

35 
15 

10 

5 

0 

-5 

-10 

SME 

CME 

LME 

ETME 

ITME 

LYGME 

HYGME 

-15 

-20 

-25 

-30 

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 

BIODIESEL CONCENTRATION, % 

Figure 3. Biodiesel/Diesel Blend Pour Point Test Results 

-10.0 

-12.5 

-15.0 

-17.5 

-20.0 

-22.5 

SME 

CME 

LME 

ETME 

ITME 

LYGME 

HYGME 

-25.0 

-27.5 

-30.0 

0.0% 2.5% 5.0% 7.5% 10.0% 

BIODIESEL CONCENTRATION, % 

Figure 4. Biodiesel/Diesel Blend Pour Point Test Results (0–10% biodiesel blend range) POUR POINT, °C POUR POINT, °C 

36 
Table 44 contains the results of the cloud point testing of the biodiesel blends. 

Table 44. Biodiesel Blend Cloud Point Test Results, °C 

Biodiesel 

Concentration SME CME LME ETME ITME LYGME HYGME 

0% -18 -18 -18 -18 -18 -18 -18 

0.25% -20 -18 -18 -16 -16 -15 -18 

0.50% -17 -18 -17 -16 -17 -14 -15 

1% -16 -18 -17 -15 -17 -16 -15 

3% -16 -17 -16 -13 -14 -16 -15 

5% -16 -17 -15 -12 -13 -16 -14 

10% -15 -17 -14 -9 -10 -13 -13 

20% -14 -15 -3 -2 -6 -6 -8 

35% -9 -12 -3 0 0 5 -6 

50% -9 -10 -2 3 4 13 -3 

100% 2 -3 14 20 23 42 8 

Figure 5 shows the results of the cloud point testing, and Figure 6 shows an expanded view of 

the 0%-10% biodiesel range. The cloud point is an important measure because it is the 

temperature at which components of the fuel begin to crystallize, forming a visible clouding of 

the liquid. When circulating in the fuel system, the components that produce the clouding can be 

captured in filters, or cause components to wear due to the solidification of the lubricants. The 

cloud point exhibits a larger increase at low concentrations of biodiesel, but to a lesser extent 

than the pour point tests. In general, avoiding complications due to this effect will require 

measures similar to those for addressing the high pour point. The fluctuations in the 0.25% and 

0.5% biodiesel measurements may be more noise. 

37 
25 

20 

15 

10 

5 

0 

-5 

SME 

CME 

LME 

ETME 

ITME 

LYGME 

HYGME 

-10 

-15 

-20 

-25 

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 

BIODIESEL CONCENTRATION, % 

Figure 5. Biodiesel/Diesel Blend Cloud Point Test Results 

-5.0 

-7.5 

-10.0 

-12.5 

SME 

CME 

LME 

ETME 

ITME 

LYGME 

HYGME 

-15.0 

-17.5 

-20.0 

0.0% 2.5% 5.0% 7.5% 10.0% 

BIODIESEL CONCENTRATION, % 

Figure 6. Biodiesel/Diesel Blend Cloud Point Test Results (0–10% biodiesel blend range) CLOUD POINT, °C CLOUD POINT, °C 

38 
Table 45 holds the testing results for cold filter plugging point. 

Table 45. Biodiesel Blend Cold Filter Plugging Point Test Results, °C 

Biodiesel 

Concentration SME CME LME ETME ITME LYGME HYGME 

0% -20 -20 -20 -20 -20 -20 -20 

0.25% -20 -20 -20 -20 -21 -20 -20 

0.50% -20 -20 -20 -20 -20 -20 -21 

1% -21 -20 -20 -20 -20 -19 -20 

3% -19 -18 -19 -19 -21 -18 -20 

5% -19 -18 -18 -17 -18 -17 -19 

10% -18 -18 -17 -14 -15 -14 -18 

20% -17 -18 -8 -3 -11 -1 -14 

35% -17 -17 4 5 -6 7 -12 

50% -17 -16 6 6 -1 9 -6 

100% -2 -4 11 14 10 11 1 

Figure 7 shows the results of the cold filter plugging point testing, and Figure 8 shows the 

expanded 0%-10% biodiesel range. The test measures the temperature at which a cold filter 

would be plugged when attempting to handle the fuel. The relationship between increase in 

temperature and biodiesel fraction is more linear than in the pour point or cloud point results for 

most of the biodiesels at the lower concentrations. However, the pork lard, edible beef tallow, 

and low free fatty acid yellow grease methyl esters exhibited higher than expected increases in 

the 20% to 50% concentration range. Since these also had the highest cold filter plugging point 

measurements, it appears that this characteristic is dominant until low biodiesel concentrations 

are reached. Conversely, the soy and canola methyl esters show a temperature depression 

through the same concentration range (20%-50%). These blends were close to the pure diesel 

temperature (within 5°C) through 50%. The biodiesels significantly varied in their effect on cold 

filter plugging point, where three inflated, two depressed, and two had a linear effect on cold 

filter plugging point. Since the two sets of biodiesels from similar sources showed differing 

actions (tallow and yellow grease biodiesels), it does not appear to be feedstock dependent. It is 

possible that processing differences caused the effect, especially since processing of the high 

free fatty acid yellow grease was handled in two steps, unlike the others. 

Researchers have investigated the effectiveness of additives to improve flow characteristics1,2. 

Their results indicate that the additives can keep the crystals from combining, which results in 

lower cold filter plugging points. In addition, the gelling, identified by the pour point, can be 

lowered by appropriate additives. 

1 Dunn, R. O., Shockley, M. W., and Bagby, M. O. "Improving the Low-Temperature Properties of

Alternative Diesel Fuels: Vegetable Oil-Derived Methyl Esters." Journal of Amer. Oil Chem. Soc., 73 

(1996): 1719-1728. 

2 Midwest Biofuels Inc. Biodiesel Pour Point and Cold Flow Study. Report to National Soydiesel 

Development Board, September 30, 1993, St. Louis, MO. 

39 
15 

10 

5 

0 

-5 

-10 

-15 

-20 

-25 

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 

BIODIESEL CONCENTRATION, % 

Figure 7. Biodiesel/Diesel Blend Cold Filter Plugging Point Test Results 

-10.00 

-15.00 

-20.00 

-25.00 

0.0% 2.5% 5.0% 7.5% 10.0% 

BIODIESEL CONCENTRATION, % 

Figure 8. Biodiesel/Diesel Blend Cold Filter Plugging Point Test Results 

(0–10% biodiesel blend range) 

COLD FILTER PLUGGING POINT, °C COLD FILTER PLUGGING POINT, °C 

SME 

CME 

LME 

ETME 

ITME 

LYGME 

HYGME 

SME 

CME 

LME 

ETME 

ITME 

LYGME 

HYGME 

40 
Table 46 contains the results of the Cetane number testing of the biodiesel blends. 

Table 46. Biodiesel Blend Cetane Number Test Results 

Biodiesel 

Concentration SME CME LME ETME ITME LYGME HYGME 

0% 47 47 47 47 47 47 47 

0.25% 47.2 47.1 47 47 47.1 46.8 47.1 

0.50% 47.1 46.9 47 47.1 47.1 47.1 47 

1% 47.2 47.3 47.3 47.1 47.3 47.2 47.2 

3% 47.3 47.2 47.4 46.9 47.5 47.3 47.2 

5% 47.4 47.6 47.4 47.3 48 47.5 47.7 

10% 47.7 47.9 48 47.7 48.4 47.6 47.8 

20% 49.2 48.8 47.9 48.4 49.8 48.7 49.3 

35% 50.4 49.6 50 49.2 50.9 50 51.4 

50% 51.4 50.6 51.2 49.8 51.9 50.8 51.6 

100% 59 53.9 64.8 54.3 52.2 53.2 

Figure 9 shows the results of the Cetane number testing, and Figure 10 shows the expanded 

0%-10% biodiesel range. Higher Cetane numbers indicate higher ignition rates, which tend to 

reduce carbon and lacquer formation and engine deposits, and decrease engine roughness. It 

appears to be linear with respect to biodiesel concentration, except for the outlying points for the 

soy and edible tallow methyl esters. 

41 
60 

58 

CETANE NUMBER 

CETANE NUMBER 

56 

54 

52 

50 

48 

46 

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 

BIODIESEL CONCENTRATION, % 

Figure 9. Biodiesel/Diesel Blend Cetane Number Test Results 

50 

49 

48 

47 

46 

0.0% 2.5% 5.0% 7.5% 10.0% 

BIODIESEL CONCENTRATION, % 

Figure 10. Biodiesel/Diesel Blend Cetane Number Test Results 

(0–10% biodiesel blend range) 

SME 

CME 

LME 

ETME 

ITME 

LYGME 

HYGME 

SME 

CME 

LME 

ETME 

ITME 

LYGME 

HYGME 

42 
Table 47 contains the results for scuffing load BOCLE lubricity testing. The high and low 

reference results are those required to verify the accuracy of the SLBOCLE test. 

Table 47. Biodiesel Blend Scuffing Load BOCLE Test Results 

Methyl Ester 

Concentration Soy Canola 

Inedible 

Tallow 

Edible 

Tallow Lard 

Low FFA 

Yellow 

Grease 

High FFA 

Yellow 

Grease 

0% 3600 3600 3600 3600 3600 3600 3600 

0.25% 4700 4600 4050 3800 4400 4700 4650 

0.50% 4950 4750 4700 4300 4700 5100 4850 

1% 5600 4950 5550 4900 5500 5500 5450 

3% 5600 5300 5850 5950 6150 6050 5650 

5% 5400 5950 6550 6100 6500 6550 5800 

10% 6100 6550 >7000 6350 6700 6650 6150 

20% 6150 >7000 >7000 6400 >7000 >7000 >7000 

35% 5850 >7000 >7000 6500 >7000 >7000 >7000 

50% 6000 >7000 >7000 >7000 >7000 >7000 >7000 

100% 6050 >7000 >7000 >7000 >7000 >7000 >7000 

High Reference 

Cat 1K 5950 6200 6250 6250 6000 6000 6100 

Low Reference 

Isopar M 1900 2200 2000 2000 2100 1900 2050 

Figure 11 shows the results of the scuffing load BOCLE tests, and Figure 12 shows the 

expanded view. Although the chart indicates that the blends stopped at 7000 grams, they were 

in fact higher. Due to limitations of the equipment, testing was stopped at 7000 grams. The 

reference line of 3100 grams indicates the minimum acceptable level for EMA specification of 

diesel. The test on the reference fuel from Philips was at 3600 grams. Figure 12 highlights the 

dramatic increase in lubricity with even small amounts of biodiesel present, which is the primary 

reason that advocates recommend the use of biodiesel as an additive even if it is not being 

used as a substantial fraction of the fuel, e.g., as B20. In general, the lubricity improved by 10% 

on average with just 0.25% biodiesel present, and by 30%+ at 0.5%. Most of the blends had 

reached 50% improvement with 1% biodiesel, and all exceeded 50% at 3%. The first blend to 

reach the maximum value was the edible beef tallow at 10%, followed by the pork lard, canola, 

and both yellow grease methyl esters at 20%. Although the soy methyl ester also increased the 

lubricity of the diesel by over two-thirds, it did not reach the maximum test value that the others 

encountered. If the biodiesels derived from tallow, lard, or yellow grease can be produced at a 

cost lower than the soy or canola biodiesels, while retaining their impact on lubricity, they could 

favorably impact the biodiesel additive market. 

43 
8000 

7000 

EMA Spec >3100 grams 

SLBOCLE (gra

ms) SLBOCLE (gra

ms) 

6000 

5000 

4000 

3000 

2000 

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 

Percent Methyl Ester 

Soy ME Canola ME Inedible Tallow Edible Tallow Lard LFFA Yellow Grease HFFA Yellow Grease 

Figure 11. Biodiesel/Diesel Blend SLBOCLE Test Results 

8000 

7000 

6000 

5000 

4000 

3000 

2000 

EMA Spec >3100 grams 

0.0% 2.5% 5.0% 7.5% 

Percent Methyl Ester 

10.0% 

Soy ME Canola ME Inedible Tallow Edible Tallow Lard LFFA Yellow Grease HFFA Yellow Grease 

Figure 12. Biodiesel/Diesel Blend SLBOCLE Test Results 

(0–10% biodiesel blend range) 

44 
Table 48 contains the results of the Oxidation Stability testing of the biodiesel blends. 

Table 48. Biodiesel Blend Oxidation Stability Test Results 

Biodiesel 

Concentration SME CME LME ETME ITME LYGME HYGME 

0% 2.34 2.34 2.34 2.34 2.34 2.34 2.34 

0.25% 3.2 3.6 2.3 1.3 2.4 2.2 0.4 

0.50% 2.3 3.7 2.1 2.4 1.5 2.0 0.8 

1% 2.6 1.2 2.8 1.9 1.8 2.6 1.3 

3% 1.3 4.1 0.7 1.4 3.4 2.9 1.5 

5% 1.0 0.9 1.1 4.8 1.2 1.3 2.8 

10% 0.8 0.9 1.2 25.7 0.7 1.0 1.7 

20% 1.6 83.4 14.0 4.4 0.8 0.7 2.2 

35% 3.0 132.9 110.3 7.6 1.8 0.9 1.8 

50% 7.4 91.8 83.1 4.0 4.5 1.6 1.2 

100% 16.0 44.9 72.0 8.1 41.0 6.2 8.2 

Figures 13 and 14 show the results of the oxidation stability tests. The results appear to indicate 

that the amount of biodiesel affects the degree of aging fairly linearly for most of the biodiesels. 

The peaks shown for the canola methyl ester and the lard methyl ester are of similar shape, and 

occur at the same biodiesel fractions. This might indicate that there was something present that 

reacted with the diesel when the diesel:biodiesel ratio was about 2:1. Further study would be 

required to determine whether this is a general trait or something specific to these batches of 

biodiesel. Given that the other biodiesels did not show the same pattern, it is more likely to be 

unique to these samples. 

Figure 14 shows that, at the lower concentrations (under 10%), the biodiesel does not add 

proportionally to the insolubles, and that it may actually have a slight suppression effect on the 

aging of the fuel. Alternatively, the distribution may be a measure of the noise in this test 

method. Further study would be required to identify the cause of the fluctuations. 

45 
140 

INSOLUBLES, mg/100 mL INSOLUBLES, mg/100 mL 

120 

100 

80 

60 

40 

20 

0 

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 

BIODIESEL CONCENTRATION, % 

Figure 13. Biodiesel/Diesel Blend Oxidation Stability Test Results 

10 

9 

8 

7 

6 

5 

4 

3 

2 

1 

0 

0.0% 2.5% 5.0% 7.5% 10.0% 

BIODIESEL CONCENTRATION, % 

Figure 14. Biodiesel/Diesel Blend Oxidation Stability Test Results 

(0–10% biodiesel blend range) 

SME 

CME 

LME 

ETME 

ITME 

LYGME 

HYGME 

SME 

CME 

LME 

ETME 

ITME 

LYGME 

HYGME 

46 
CONCLUSIONS 

The first set of conclusions concerns the production of methyl esters. Starting with clean 

vegetable oil (e.g., soy and canola) leads to biodiesel that is easier to produce and cleaner with 

equivalent amounts of processing. The animal-based and waste grease-based biodiesels have 

additional needs at the end of transesterification to ensure acceptable properties of the 

biodiesel, and may benefit from processing before transesterification to reduce or eliminate 

components that may interfere, as in the case with the free fatty acids in the yellow grease. 

Further study should identify methods of economically handling free fatty acids and other 

components, so that they do not interfere with processing at a minimum, and ideally, that they 

contribute to the production of methyl esters. It is important to provide adequate testing 

throughout processing to know the state of the fuel. Care must be taken to ensure that "fuel 

grade" methyl esters are produced, instead of the more common "commercial grade." 

Testing indicated there are problems in operating with low temperatures (cloud point, cold filter 

plugging point, and pour point), and that the minimum temperatures at which biodiesels are 

usable increase with the move from vegetable to animal sources, probably due to the greater 

degree of saturation. Yellow grease, having some of the properties of the animal biodiesels 

although they were originally vegetable oils, display intermediate temperatures. The higher 

viscosities showed the same trends as the temperatures, with the lard and tallow biodiesels 

higher than the soy and canola biodiesels. Because of the potential effect that high viscosities 

can have on injector spray performance, this property should be watched in producing biodiesel. 

However, the biodiesels have high boiling points, flash points, and low vapor pressure, as well 

as an inability to smoke under the smoke point test, indicating a high level of safety for handling 

biodiesels. In addition, biodiesels show low levels of reactiveness with other materials (e.g., 

copper corrosion). A focus on additives to forestall the cloud/plugging/pour point problems 

would help the adoption of biodiesels in areas with low ambient temperatures (much of the 

United States for the tallow and lard biodiesels). 

In considering the range of tests performed in this project, the specifications used to identify 

acceptable biodiesels do not need any additions. Other tests would contribute additional 

information about the composition and properties, but the tests in the specifications adequately 

identify whether the quality of the fuel is acceptable. 

The biodiesel specification and the ASTM D 975 specification can be partially applied to B20. 

B20 could exceed D 975 values for sulfated ash, viscosity, and distillation fraction temperature, 

and could exceed biodiesel limits in flash point and carbon residue. 

The objective of the biodiesel/diesel blend testing was to determine if biodiesels from different 

feedstocks exhibit different characteristics in varying concentrations with diesel when tested on 

a consistent basis. Testing covered blending ranges that have previously been overlooked in 

the study of the potential of biodiesel blends. Of particular interest for people considering use of 

biodiesels in ratios other than as B20 or straight are the shifts in temperature for various 

properties tested. Care should be taken in handling and use due to the temperature increases 

that occurred for pour point, cloud point, and cold filter plugging point. In terms of lubricity, the 

significant increase that occurs with even concentrations at 3% or less of the biodiesels appears 

to confirm that biodiesel additives could improve operation of diesels and extend life of their 

components. In particular, further study may be warranted to improve the processing of the beef 

tallow and pork lard, with a goal of reducing cost while enhancing the characteristics of the 

methyl esters that improve lubricity. 

47 
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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 

March 21, 2003 

3. REPORT TYPE AND DATES COVERED 

Subcontract Report 

4. TITLE AND SUBTITLE 

Production of Biodiesels from Multiple Feedstocks and Properties of Biodiesels and 

Biodiesel/Diesel Blends: Final Report; Report 1 in a Series of 6 

6. AUTHOR(S) 

J.A. Kinast 

5. FUNDING NUMBERS 

BFP2.9110 

ACG-8-17106-02 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 

Gas Technology Institute 

Des Plaines, Il 60018 

8. PERFORMING ORGANIZATION 

REPORT NUMBER 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 

National Renewable Energy Laboratory 

1617 Cole Blvd. 

Golden, CO 80401-3393 

10. SPONSORING/MONITORING 

AGENCY REPORT NUMBER 

NREL/SR-510-31460 

11. SUPPLEMENTARY NOTES 

NREL Technical Monitor: K.S. Tyson 

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National Technical Information Service 

U.S. Department of Commerce 

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Springfield, VA 22161 

12b. ISTRIBUTION CODE 

13. ABSTRACT (Maximum 200 words) 

In a project sponsored by the National Renewable Energy Laboratory, the Institute of Gas Technology is conducting an 

investigation of biodiesels produced from vegetable and animal based feedstocks. This subcontract report presents their 

findings. 

15. NUMBER OF PAGES 

14. SUBJECT TERMS 

biodiesel; methyl esters; Institute of Gas Technology 16. PRICE CODE 

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Unclassified 

18. SECURITY CLASSIFICATION 

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Unclassified 

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Unclassified 

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