Biodiesel 

Handling and Use Guide 

Fourth Edition

NREL/TP-540-43672

Revised January 2009 National Renewable Energy Laboratory

Innovation for Our Energy Future
Notice

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 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 1 

1.0 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.0 Biodiesel Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.1 What Is Biodiesel? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.2 Benefits of Biodiesel Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.3 Other Biodiesel Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.0 Biodiesel (B100) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.1 B100 Quality Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3.2 Variation in Biodiesel Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.3 Energy Content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

3.4 Low-Temperature Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3.5 Cetane Number . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

3.6 Transport and Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

3.6.1 Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

3.6.2 Microbial Contamination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.6.3 Cleaning Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.6.4 Materials Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.6.5 Storage Tanks and Dispensing Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3.6.6 Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3.7 Use of B100 and High Blend Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.0 Biodiesel Blends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.1 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.1.1 B5 and Lower Blends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.1.2 B6 to B20 Blends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.2 Low-Temperature Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

4.3 Lubricity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

4.4 Blending, Storage, and Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

4.4.1 Blending . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

4.4.2 Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

4.4.3 Cleaning Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

4.4.4 Materials Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

5.0 BQ-9000 Program for Supply Chain Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

6.0 Engine Warranties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

7.0 Taxes and Incentives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

7.1 Off-Road Diesel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

8.0 Safety, Health, and Environmental Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

8.1 Signs, Labels, and Stickers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

8.2 Fire Safety Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

9.0 Frequently Asked Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

10.0 Information Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

11.0 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Appendix A. Sample Biodiesel Material Safety Data Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Appendix B. Renewable Identification Number . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Appendix C. Biodiesel Use as an EPAct Alternative Fuel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Contents
2 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

Appendix D. Density and Viscosity as a Function of Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Appendix E. Biodiesel Materials Compatibility Summary Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Elastomers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Appendix F. BQ-9000 Sample Certificate of Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 3 

Figure 1. Basic Transesterification Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Figure 2. Average Emission Impacts of Biodiesel Fuels in CI Engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Figure 3. Composition of Various Biodiesel Feedstocks in Order of Increasing Saturated Fatty Acid Content . . . . . . . . . 16

Figure 4. Cetane Number of Two Petroleum Diesels and Several Biodiesels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 5. ASTM D4625 Long-Term Storage Stability for B100 Samples Having a Range of Initial Induction Periods. . . . . 20

Figure 6. Biodiesel/Diesel Blend Cloud Point Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Figure 7. Biodiesel/Diesel Blend Cloud Point Test Results (0%–10% Biodiesel Blend Range) . . . . . . . . . . . . . . . . . . . . . 26

Figure 8. Biodiesel/Diesel Blend Pour Point Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Figure 9. Biodiesel/Diesel Blend Pour Point Test Results (0%–10% Biodiesel Blend Range) . . . . . . . . . . . . . . . . . . . . . . 26

Figure 10. Biodiesel/Diesel Blend Cold Filter Plugging Point Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Figure 11. Biodiesel/Diesel Blend Cold Filter Plugging Point Test Results (0%–10% Biodiesel Blend Range) . . . . . . . . . . . 26

Figure 12. Adjusting Cloud Points of B20 Fuels with Blends of No. 1 and No. 2 Diesel . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 13. Cold Flow Properties of Some Soy Biodiesel Blends, oF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Figure 14. HFRR Lubricity as a Function of Biodiesel Content for a No. 1 and a No. 2 Diesel Fuel . . . . . . . . . . . . . . . . . . 29

Figure 15. D4625 Storage Results for B5 Blends Made from B100 with Varying Levels of Oxidation Stability as 

Measured by the OSI Induction Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Figure 16. D4625 Storage Results for B20 Blends Made from B100 with Varying Levels of Oxidation Stability as 

Measured by OSI or Rancimat Induction Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Figures

Table 1. Select Properties of Typical No. 2 Diesel and Biodiesel Fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Table 2. Requirements for Biodiesel (B100) Blend Stock as Listed in ASTM D6751-08a . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Table 3. Fuel Properties as a Function of Fuel Composition in Diesel Engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Table 4. Heating Value of Diesel and Some Biodiesel (B100) Fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Table 5. Cold Flow Data for Various B100 Fuels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Table 6. ASTM D7467 Specification for Diesel Blends B6 to B20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Tables
4 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

AFV . . . . . . alternative fuel vehicle

ASTM . . . . . ASTM International

B100 . . . . . .100% biodiesel

B20 . . . . . . 20% biodiesel, 80% petroleum diesel

Btu . . . . . . . British thermal unit

Ca . . . . . . . calcium

CFPP . . . . . cold filter plug point

CI . . . . . . . . compression ignition

CO . . . . . . . carbon monoxide

COA . . . . . . certificate of analysis

CO2

 . . . . . . . carbon dioxide

DOE . . . . . . U.S. Department of Energy

DOT . . . . . . U.S. Department of Transportation

ECRA . . . . . Energy Conservation Reauthorization Act of 1998

EPA . . . . . . . U.S. Environmental Protection Agency

EPAct . . . . . Energy Policy Act of 1992 (amended in 1998)

FAME . . . . . fatty acid methyl esters

GHG . . . . . . greenhouse gas

HC . . . . . . . hydrocarbon

HFRR . . . . . high-frequency reciprocating rig 

IRS . . . . . . . Internal Revenue Service

K . . . . . . . . potassium

KOH . . . . . . potassium hydroxide

LTFT . . . . . . low-temperature flow test

Mg . . . . . . . magnesium

MSDA . . . . . material safety data sheet

MSHA . . . . . U.S. Department of Labor Mining Safety Health Administration

Na . . . . . . . sodium

NBB . . . . . . National Biodiesel Board

NOx . . . . . . nitrogen oxides

NFPA . . . . . National Fire Protection Association

NREL . . . . . National Renewable Energy Laboratory

OEM . . . . . . original equipment manufacturer

OSHA . . . . . Occupational Safety and Health Administration

OSI . . . . . . . Oil Stability Index

PAH . . . . . . polyaromatic hydrocarbons

PM . . . . . . . particulate matter

ppm . . . . . . parts per million

RCRA . . . . . Resource Conservation & Recovery Act of 1976

RFS . . . . . . Renewable Fuels Standard

SO2

 . . . . . . . sulfur dioxide

UL . . . . . . . Underwriters Laboratories

VOC . . . . . . volatile organic compound

Abbreviations and Acronyms
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 5 

This document is a guide for those who blend, store, distribute, and use biodiesel and biodiesel blends. It provides 

basic information on the proper and safe use of biodiesel and biodiesel blends in compression-ignition engines 

and boilers, and it is intended to help fleets, individual users, blenders, distributors, and those involved in related 

activities understand procedures for handling and using biodiesel fuels. 

Biodiesel is manufactured from plant oils, animal fats, and recycled cooking oils. Biodiesel’s advantages are 

as follows:

• It is renewable. 

• It is energy efficient. 

• It displaces petroleum-derived diesel fuel.

• It can be used as a 20% blend in most diesel equipment with no or only minor modifications.

• It can reduce global warming gas emissions.

• It can reduce tailpipe emissions, including air toxics.

• It is nontoxic, biodegradable, and suitable for sensitive environments.

In this report, biodiesel refers to the fuel produced from renewable sources that meets ASTM International 

D6751, the standard for biodiesel. A number following the “B” indicates the percentage of biodiesel in a gallon of 

fuel; the remainder of the gallon can be No. 1 or No. 2 diesel, kerosene, jet A, JP8, heating oil, or any other distillate fuel. Pure biodiesel is also known as B100. 

Biodiesel is most commonly used as a blend with petroleum diesel. At concentrations of up to 5 vol % (B5) in 

conventional diesel fuel, the mixture will meet the ASTM D975 diesel fuel specification and can be used in any 

application as if it were pure petroleum diesel; for home heating oil, B5 will meet the D396 home heating oil 

specification. At concentrations of 6% to 20%, biodiesel blends can be used in many applications that use diesel 

fuel with minor or no modifications to the equipment, although certain manufacturers do not extend warranty 

coverage if equipment is damaged by these blends. The B6 to B20 blends are covered by the ASTM D7467 specification that was approved in June 2008 and will be published later in 2008. Biodiesel can even be used as a fuel 

in its pure form (B100) if proper precautions are taken. 

B20 is the most commonly used biodiesel blend in the United States because it provides a good balance between 

material compatibility, cold weather operability, performance, emission benefits, and costs. B20 is also the 

minimum blend level allowed for compliance with the Energy Policy Act of 1992 (EPAct), which requires the use 

of renewable fuels and/or alternative fuel vehicles (AFVs) by certain covered fleets. Equipment that can use B20 

includes compression-ignition (CI) engines, fuel oil and heating oil boilers, and turbines. 

B100 or higher blend levels such as B50 require special handling and may require equipment modifications. 

These issues can potentially be managed with heaters and/or changing engine seal and gasket materials. However, 

because the level of special care needed is high, the National Renewable Energy Laboratory (NREL) and the U.S. 

Department of Energy (DOE) do not recommend the use of high-level biodiesel blends, except where human 

exposure to diesel particulate matter (PM) is elevated and health concerns merit the additional attention to equipment and fuel handling. Always consult your engine or combustion equipment manufacturer for further information about procedures before using biodiesel blends higher than B20.

1.0 Introduction
6 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

2.0 Biodiesel Basics

This section provides a basic overview of biodiesel. You can also refer to Section 9 (Frequently Asked Questions) 

for answers to general questions from your management, customers, or reporters. Technical details about many 

aspects of biodiesel are provided in Sections 3 to 8.

2.1 What Is Biodiesel?

Biodiesel is a diesel replacement fuel for use in CI engines. It is manufactured from plant oils (soybean oil, cottonseed oil, canola oil), recycled cooking greases or oils (e.g., yellow grease), or animal fats (beef tallow, pork 

lard). Because plants produce oils from sunlight and air, and can do so year after year on cropland, these oils are 

renewable. Animal fats are produced when the animal consumes plants or animals, and these too are renewable. 

Used cooking oils are mostly plant based, but may also contain animal fats. Used cooking oils are both recycled 

and renewable. 

The biodiesel manufacturing process converts oils and fats into chemicals called long-chain mono alkyl esters, or 

biodiesel. These chemicals are also referred to as fatty acid methyl esters (FAME) and the process is referred to 

as transesterification. Figure 1 provides a simplified diagram of the transesterification process. Roughly speaking, 

100 pounds of oil or fat are reacted with 10 pounds of a short-chain alcohol (usually methanol) in the presence of 

a catalyst (usually sodium hydroxide [NaOH] or potassium hydroxide [KOH]) to form 100 pounds of biodiesel 

and 10 pounds of glycerin. Glycerin is a sugar, and is a coproduct of the biodiesel process. 

Raw or refined plant oil, or recycled greases that have not been processed into biodiesel, are not biodiesel 

and should be avoided. Research shows that plant oils or greases used in CI engines at concentrations as low as 

10% to 20% can cause long-term engine deposits, ring sticking, lube oil gelling, and other maintenance problems 

and can reduce engine life. These problems are caused mostly by the greater viscosity, or thickness, of the raw oils 

(around 40 mm2

/s) compared with that of the diesel fuel, for which the engines and injectors were designed (1.3 to 

4.1 mm2

/s). Through the process of converting plant oils or greases to biodiesel by transesterification, the viscosity 

of the fuel is reduced to values similar to conventional diesel fuel (biodiesel values are typically 4 to 5 mm2/s). 

Vegetable Oil/

Animal Fat/Waste

Crude

Biodiesel

Crude Glycerin

Biodiesel

Glycerin

Methanol

plus Catalyst Transesterification

Glycerine

Refining

Methanol

Recovery

Refining

Figure 1. Basic Transesterification Process
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 7 

Biodiesel is a legally registered fuel and fuel additive with the U.S. Environmental Protection Agency (EPA). The 

EPA registration includes all biodiesel that meets the ASTM biodiesel specification, ASTM D 6751,2 and does not 

depend on the oil or fat used to produce the biodiesel or the specific production process employed. 

Other products, many of which are offered to consumers without the benefit of EPA registration or extensive 

testing and demonstrations, are mislabeled as “biofuels.” If you purchase methyl ester that does not meet ASTM 

biodiesel standards, it is not legal biodiesel and should not be used in diesel engines or other equipment designed 

to operate on diesel fuel. Methyl esters are used as an industrial lubricant and solvent in some applications, so be 

sure to purchase only ASTM grade methyl esters (biodiesel). 

ASTM International3

 is a consensus-based standards group that comprises engine and fuel injection equipment 

companies, fuel producers, and fuel users whose standards are recognized in the United States by most government entities. The specification for biodiesel (B100) is ASTM D6751. This specification is a compilation of efforts 

from researchers, engine manufacturers, petroleum companies and distributors, and many other fuel-related entities, and it is intended to ensure the quality of biodiesel used as a blend stock at 20% and lower blend levels. Any 

biodiesel used in the United States for blending should meet ASTM D6751 standards.4

The ASTM D6751 definition of biodiesel states that biodiesel is composed of mono-alkyl esters of long-chain 

fatty acids derived from plant oils or animal fats. The term mono-alkyl esters indicates that biodiesel contains 

only one ester linkage in each molecule. Plant oils contain three ester linkages and are therefore not legally 

biodiesel. Biodiesel can be made from methyl, ethyl, isopropyl, and other alcohols, but most biodiesel research 

focuses on methyl esters. Virtually all commercial production in the United States today is based on methyl 

esters. Some research has been conducted on ethyl esters (biodiesel produced with ethanol as the alcohol rather 

than methanol); however, higher ethanol prices relative to methanol, lower ethyl ester conversions, and the difficulty of recycling excess ethanol internally in the process have hampered ethyl ester production in the marketplace. Therefore, in this document we will consider only methyl esters. 

The definition of biodiesel recognized by both the EPA for fuel registration purposes and the Internal Revenue 

Service (IRS) for the blender’s tax credit is essentially the same as the definition in ASTM D6751: 

A fuel comprised of mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats, designated B100, and meeting the requirements of ASTM D 6751. 

Biodiesel is a recognized alternative fuel under the Energy Policy Act of 1992 (EPAct), as amended in 1998. 

EPAct requires that more than 75% of new vehicle purchases by certain federal, state, and alternative fuel provider fleets be alternative fuel vehicles (AFVs). As a recognized alternative fuel, any vehicle certified to run on 

B100 could qualify under the AFV purchase provisions of EPAct, but no generally available vehicles are intended 

to run on B100. B100 is more expensive than other alternative fuel options, and the original equipment manufacturer (OEM) community has had little interest in certifying vehicles on B100, so this vehicle credit has not 

created a market for biodiesel. 

EPAct was amended in 1998 by the Energy Conservation and Reauthorization Act (ECRA). The amendment 

allowed qualified fleets to use B20 in existing vehicles to generate AFV purchase credits, with some limitations. 

This has created significant demand for B20 by government and alternative fuel provider fleets. 

2.2 Benefits of Biodiesel Use

Biodiesel Provides a High Energy Return and Displaces Imported Petroleum

Life-cycle analyses show that biodiesel contains 2.5 to 3.5 units of energy for every unit of fossil energy input in 

its production, and because very little petroleum is used in its production, its use displaces petroleum at nearly a 

1-to-1 ratio on a life-cycle basis.5,6,7 This value includes energy used in diesel farm equipment and transportation 

equipment (trucks, locomotives); fossil fuels used to produce fertilizers, pesticides, steam, and electricity; and 

methanol used in the manufacturing process. Because biodiesel is an energy-efficient fuel, it can extend petroleum supplies.
8 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

Biodiesel Reduces Life-Cycle Greenhouse Gas Emissions

When biodiesel displaces petroleum, it significantly reduces greenhouse gas (GHG) emissions. By one estimate, 

GHG emissions (including carbon dioxide [CO2

], methane, and nitrogen oxide [NOx]) are reduced by 41%, if 

biodiesel is produced from crops harvested from fields that were already in production.5 When plants such as 

soybeans grow, they take CO2 from the air to make the stems, roots, leaves, and seeds (soybeans). After the oil is 

extracted from the soybeans, it is converted into biodiesel. When the biodiesel is burned, CO2

 and other emissions 

are released and return to the atmosphere. This cycle does not add to the net CO2 concentration in the air because 

the next soybean crop will reuse the CO2

 as it grows. When fossil fuels such as coal or diesel fuel are burned, 

however, 100% of the CO2 released adds to the CO2 concentration levels in the air. 

Biodiesel Reduces Tailpipe Emissions

Biodiesel reduces tailpipe PM, hydrocarbon (HC), and carbon monoxide (CO) emissions from most modern 

four-stroke CI or diesel engines. These benefits occur because biodiesel contains 11% oxygen by weight. The fuel 

oxygen allows the fuel to burn more completely, so fewer unburned fuel emissions result. This same phenomenon 

reduces air toxics, which are associated with the unburned or partially burned HC and PM emissions. Testing has 

shown that PM, HC, and CO reductions are independent of the biodiesel feedstock. The EPA reviewed 80 biodiesel emission tests on CI engines and has concluded that the benefits are real and predictable over a wide range of 

biodiesel blends (Figure 2).8

 EPA’s review also indicated that B20 increased NOx by about 2% relative to petroleum diesel use. A more detailed analysis of the database examined by EPA, plus more recently published results, 

confirms the positive impact of B20 on emissions of HC, CO, and PM.9 However, examination of the NOx results 

shows that the effect of biodiesel can vary with engine design, calibration, and test cycle. At this time, the data 

are insufficient for users to conclude anything about the average effect of B20 on NOx, other than that it is likely 

very close to zero.

In contrast, when biodiesel is used in boilers 

or home heating oil applications, NOx tends 

to decrease because the combustion process 

is different (open flame for boilers, enclosed 

cylinder with high-pressure spray combustion 

for engines). The NOx reduction seen with 

biodiesel blends used in boilers appears to be 

independent of the type of biodiesel used. In 

blends with heating oil up to 20% biodiesel, 

NOx is reduced linearly with increasing biodiesel content. For every 1% biodiesel added, NOx 

decreases by 1%. A B20 heating oil fuel will 

reduce NOx by about 20%.10,11 Sulfur dioxide 

(SO2

) emissions were also reduced when the 

two fuels were blended, because biodiesel 

contains much less sulfur than typical heating 

oil does. A 20% blend of biodiesel in heating 

oil will reduce SO2 by about 20%. 

Heating oil and diesel fuel dyed red for off-road use (agriculture, power, boiler fuels, construction, forestry, and 

mining) can contain as much as 500 ppm sulfur. Blending biodiesel into off-road diesel fuel can significantly 

reduce SO2

 emissions. Nonroad diesel will transition to 15 ppm sulfur beginning in 2010.

Biodiesel and Human Health

Some PM and HC emissions from diesel fuel combustion are toxic or carcinogenic. Using B100 can eliminate as 

much as 90% of these air toxics. B20 reduces air toxics by 20% to 40%. The positive effects of biodiesel on air 

toxics have been shown in numerous studies. 

0

-20

-40

-60

-80

0 20 40 60 80 100

Percent Change in Emissions

Percent Biodiesel

Hydrocarbon

Carbon Monoxide

Particulate Water

Figure 2. Average Emission Impacts of Biodiesel Fuels in CI Engines12
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 9 

Recently, the U.S. Department of Labor Mining Safety Health Administration (MSHA) has implemented rules for 

underground mines that limit workers’ exposure to diesel PM. MSHA found that switching from petroleum diesel 

fuels to high blend levels of biodiesel (B50 to B100) significantly reduced PM emissions from underground diesel 

vehicles and substantially reduced workers’ exposure. However, even low concentrations of biodiesel reduce PM 

emissions and provide significant health and compliance benefits wherever humans receive higher levels of exposure to diesel exhaust. 

Biodiesel Improves Engine Operation

Even in very low concentrations, biodiesel improves fuel lubricity and raises the cetane number of the fuel. 

Diesel engines depend on the lubricity of the fuel to keep moving parts, especially fuel pumps, from wearing 

prematurely. One unintended side effect of the federal regulations, which have gradually reduced allowable fuel 

sulfur to only 15 ppm and lowered aromatics content, has been to reduce the lubricity of petroleum diesel. The 

hydrotreating processes used to reduce fuel sulfur and aromatics contents also reduces polar impurities such 

as nitrogen compounds, which provide lubricity. To address this, the ASTM D975 diesel fuel specification was 

modified to add a lubricity requirement (a maximum wear scar diameter on the high-frequency reciprocating rig 

[HFRR] test of 520 microns). Biodiesel can impart adequate lubricity to diesel fuels at blend levels as low as 1%. 

Biodiesel Is Easy To Use

Finally, one of the biggest benefits to using biodiesel is that it is easy. Blends of B20 or lower are literally a “drop 

in” technology. No new equipment and no equipment modifications are necessary. B20 can be stored in diesel 

fuel tanks and pumped with diesel equipment. B20 does present a few unique handling and use precautions, but 

most users can expect a trouble-free B20 experience.

2.3 Other Biodiesel Attributes

Lower Energy Density

Biodiesel contains 8% less energy per gallon than typical No. 2 diesel in the United States and 12.5% less energy 

per pound. The difference between these two measurements is due to the higher density of biodiesel compared 

with diesel fuel. All biodiesel, regardless of its feedstock, provides about the same amount of energy per gallon or 

per pound. Typical values are as follows: 

Btu/lb Btu/gal

Typical Diesel No. 2 18,300 129,050

Biodiesel (B100) 16,000 118,170

The difference in energy content between petroleum diesel and biodiesel can be noticeable with B100. For B20, 

the differences in power, torque, and fuel economy are 1% to 2%, depending on the base petroleum diesel. Most 

users report little difference in fuel economy between B20 and No. 2 diesel fuel. As the biodiesel blend level is 

lowered, differences in energy content become proportionally less significant; blends of B5 or lower cause no 

noticeable differences in performance in comparison to No. 2 diesel.

Low-Temperature Operability

In some areas of the country, the cold flow properties of biodiesel are important. Unlike gasoline, petroleum 

diesel and biodiesel both freeze or gel at common winter temperatures; however, biodiesel’s freeze point may be 

20o to 30oF higher than that of petroleum diesel. If the fuel begins to gel, it can clog filters and eventually become 

so thick that it cannot be pumped from the fuel tank to the engine. However, with proper handling, B20 has been 

used successfully all year in the coldest U.S. climates. 
10 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

This section describes the basic considerations for handling and blending B100. In the United States it is equally 

common to handle B99 and B99.9 blends, as these qualify for a federal blender’s tax credit. The considerations 

in this section also apply to B99 and B99.9. The storage and handling procedures for B100 are very different 

from those for B20 and lower biodiesel blends, and they vary significantly from those of diesel fuel. Table 1 lists 

some of the physical and chemical properties of B100 and petroleum diesel. Using B20 and lower blends significantly reduces or eliminates the effects of these property differences for use as an engine fuel. However, since 

many distributors store and handle B100 before blending, a good understanding of B100 properties is valuable. 

Following are several significant attributes specific to B100 that should be considered when handling, storing, 

and using it.

• B100 is a good solvent. It may loosen or dissolve varnish and sediments in fuel tanks and fueling systems 

left by conventional diesel over time. If your system contains sediments, you should definitely clean your 

tanks and fuel system before handling or using B100. 

• B100 freezes at higher temperatures than most diesel fuel. This must be taken into account if handling or 

using B100, especially in aboveground storage tanks. Most B100 starts to cloud at 35o to 60oF (2o to 15oC), 

so heated fuel lines and tanks may be needed, even in moderate climates, during winter. As B100 begins to 

gel, the viscosity also begins to rise to much higher levels than most diesel fuel does, which can increase the 

stress on pumps. The high cloud point makes B100 use challenging in colder climates.

• B100 is not compatible with some hoses and gaskets. B100 may soften and degrade certain types of rubber 

compounds used for hoses and gaskets (buna-N, nitrile, natural rubber) and may cause them to leak and 

degrade to the point where they crumble and become useless. For bulk handling of B100, seals, gaskets, and 

hoses must be compatible with B100. (See Appendix E for information about material compatibility.) Using 

Soy biodiesel, for example, has a cloud point (the temperature at which crystals begin to form) of 32oF (0oC). In 

contrast, most petroleum diesels have cloud points of about 10o to 20oF (-12o to -5oC). Blending of biodiesel can 

significantly raise the cloud point above that of the original diesel fuel. For example, a recent study13 showed that, 

when soy biodiesel was blended into a specially formulated cold weather diesel fuel (cloud point of -36oF [-38oC]) 

to make a B20 blend, the cloud point of the blend was -4oF (-20oC). In very cold climates, this cloud point may 

still not be adequate for wintertime use. To accommodate biodiesel in cold climates, low cloud point petroleum 

diesel or low-temperature flow additives, or both, are necessary.

Storage Stability

Although biodiesel blends have adequate storage stability for normal use, special precautions must be taken if 

they are to be stored for extended periods. This might occur in a snow plow or farm implement used seasonally, 

or in the fuel tank of a backup generator. If the fuel will be stored for more than a few months, a stability additive 

is recommended, and acidity should be measured monthly.

Finally, biodiesel is generally more susceptible than petroleum diesel to microbial degradation. In the case of 

spills in the environment, this is a positive attribute because it biodegrades more rapidly. However, microbial contamination of fuel storage tanks can plug dispensers and vehicle fuel filters and cause vehicles to stall. This is not 

unheard of for petroleum diesel, but anecdotal evidence suggests it is a greater problem for biodiesel blends. The 

best way to deal with this issue (for both petroleum diesel and biodiesel) is adequate fuel storage tank housekeeping and monitoring, especially minimizing water in contact with the fuel. Water bottoms must be removed from 

tanks, and standing tanks should be sampled and tested for microbial contamination.

3.0 Biodiesel (B100)
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 11 

B100 in an engine constructed with incompatible materials can cause a fuel spill on a hot engine, ruin a fuel 

pump, or clog a filter as the hose material gradually erodes. Use extreme care to ensure any part of the fuel 

system that touches the fuel is compatible with B100. Some systems already have biodiesel-resistant materials, but many do not, because these materials are usually slightly more expensive. 

• B100 is not compatible with some metals and plastics. Biodiesel will degrade and form high sediment levels 

if contacted for long periods by copper or copper containing metals (brass, bronze) or with lead, tin, or zinc 

(galvanized surfaces). These high sediment levels may clog filters. B100 may also permeate some common 

plastics (polyethylene, polypropylene) over time, so these should not be used for storing B100. 

Table 1. Select Properties of Typical No. 2 Diesel and Biodiesel Fuels

Fuel Property Diesel Biodiesel

Fuel Standard ASTM D975 ASTM D6751

Higher Heating Value, Btu/gal ~137,640 ~127,042

Lower Heating Value, Btu/gal ~129,050 ~118,170

Kinematic Viscosity, @ 40oC (104oF) 1.3–4.1 4.0–6.0

Specific Gravity kg/l @ 15.5oC (60oF) 0.85 0.88

Density, lb/gal @ 15.5oC (60oF) 7.1 7.3

Carbon, wt % 87 77

Hydrogen, wt % 13 12

Oxygen, by dif. wt % 0 11

Sulfur, wt % 0.0015 max 0.0–0.0024

Boiling Point, oC (oF) 180–340 (356–644) 315–350 (599–662)

Flash Point, oC (oF) 60–80 (140–176) 100–170 (212–338)

Cloud Point, oC (oF) -35 to 5 (-31 to 41) -3 to 15 (26 to 59)

Pour Point, oC (oF) -35 to -15 (-31 to 5) -5 to 10 (23 to 50)

Cetane Number 40–55 48–65
12 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

3.1 B100 Quality Specification

The ASTM specification for biodiesel (B100) is ASTM D6751. This specification is frequently updated, and as of 

this writing the most current version is D6751-08a, summarized in Table 2. 

Sulfated Ash D874 0.020 max. % mass

Sulfur D5453 0.0015 max. (S15)

0.05 max. (S500) % mass

Copper Strip Corrosion D130 No. 3 max.

Cetane Number D613 47 min.

Cloud Point D2500 Report to customer oC

Carbon Residuea D4530 0.050 max. % mass

Acid Number D664 0.50 max. mg KOH/g

Free Glycerin D6584 0.020 max. % mass

Total Glycerin D6584 0.240 max. % mass

Phosphorus Content D4951 0.001 max. % max.

Distillation Temperature, 90% Recovered (T90)b D1160 360 max. oC

Na and K Combined EN14538 5 max. ppm

Oxidation Stability EN14112 3 min. h

Cold Soak Filterability Annex A1 360 max.c s

a

 Carbon residue shall be run on the 100% sample.

b

 Atmospheric equivalent temperature.

c B100 intended for blending into diesel fuel that is expected to give satisfactory vehicle performance at fuel temperatures at or below 10oF (-12oC) 

shall comply with a cold soak filterability limit of 200 s maximum.

Table 2. Requirements for Biodiesel (B100) Blend Stock as Listed in ASTM D6751

Property Test Method Limits Units

Calcium and Magnesium Combined EN14538 5 max. ppm

Flash Point D93 93.0 min. oC

Alcohol Control - One of the following must be met:

 1. Methanol Content

 2. Flash Point

EN14110

D93

0.2 max.

130 min.

vol % 

oC

Water and Sediment D2709 0.050 max. vol %

Kinematic Viscosity, 40oC D445 1.9–6.0 mm2

/s
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 13 

This specification is intended to ensure the quality of biodiesel to be used as a blend stock at 20% and lower 

levels. Any biodiesel used in the United States for blending must meet ASTM D6751 before blending. ASTM 

D6751 is based on the physical and chemical properties needed for safe and satisfactory diesel engine operation. 

It is not based on the specific raw materials or the manufacturing process used to produce the biodiesel. The finished blend stock must meet the properties specified in Table 2 as well as the following definition:

Biodiesel, noun, a fuel comprised of mono-alkyl esters of long chain fatty acids derived from vegetable oils or 

animal fats, designated B100.

This specification was not intended to be applied to B100 used in a pure form. However, buyers and sellers are 

encouraged to use ASTM D6751 for the commercial trading of biodiesel (B100) whether the fuel is planned for 

B100 use or for blending. Other arrangements or specifications can be legally used if the buyer and seller agree 

as long as they meet pertinent local, state, and federal regulations (EPA sulfur limits, Occupational Safety and 

Health Administration [OSHA] safety limits on flash point, etc.). However, B100 must meet the requirements of 

D6751 for blends to be legal fuels under the Clean Air Act fuel registration requirements, to legally claim the 

biodiesel blender’s tax credit, and to be a legal blending component under many state regulations.

The intent of each quality requirement in Table 2 is described here:

• High levels of Group I and II metals. Sodium (Na), potassium (K), calcium (Ca), and magnesium (Mg) can 

cause deposits to form, catalyze undesired side reactions, and poison emission control equipment. The 

Group I and II metals are limited as the combination of metals in each category, Na+K and Ca+Mg. For each 

combination, the limit is 5 ppm. 

• Flash point. A minimum flash point for diesel fuel is required for fire safety. B100’s flash point is required to 

be at least 93oC (200oF) to ensure it is classified as nonhazardous under the National Fire Protection Association (NFPA) code. 

• Alcohol. It is critical to ensure that the manufacturer has removed excess methanol used in the manufacturing process. Residual methanol in the fuel is a safety issue, because even very small amounts reduce the 

flash point; can affect fuel pumps, seals, and elastomers; and can result in poor combustion properties. The 

intent of the alcohol control requirement is to limit methanol to less than 0.2 wt %. This can be accomplished by meeting a higher flash point requirement of 130oC (266oF); or by measuring methanol content by 

gas chromatography.

• Water and sediment. This refers to free water droplets and sediment particles. The allowable level for B100 is 

set at the same level allowed for conventional diesel fuel. Poor drying techniques during manufacturing or 

contact with excessive water during transport or storage can cause B100 to be out of specification for water 

content. Excess water can lead to corrosion and provides an environment for microorganisms. Fuel oxidation can also raise sediment levels, so this test can be used in conjunction with acid number and viscosity to 

determine if fuels have oxidized too much during storage.

• Viscosity. A minimum viscosity is required for some engines because of the potential for power loss 

caused by injection pump and injector leakage. This is not an issue for B100, and the minimum is set at 

the same level as for petroleum diesel. The maximum viscosity is limited by the design of engine fuel 

injection systems. Higher viscosity fuels can cause poor fuel combustion that leads to deposit formation 

as well as higher in-cylinder penetration of the fuel spray, which can result in elevated engine oil dilution 

with fuel. The maximum allowable viscosity in ASTM D975 for No. 2 diesel is 4.1 mm2/s at 104oF (40oC). 

ASTM D6751 allows for slightly higher viscosity than D975, primarily because that is where the normal 

viscosity of B100 lies. Biodiesel blends of 20 vol % or lower should have a viscosity within the range 

allowed by D975.
14 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

• Sulfated ash test. This test measures the amount of residual alkali catalyst in the biodiesel as well as any 

other ash-forming compounds that could contribute to injector deposits or fuel system fouling. 

• Sulfur. This is limited to reduce sulfate and sulfuric acid pollutant emissions and to protect exhaust catalyst systems when they are deployed on diesel engines in the future. Sulfur content of 15 ppm or lower is 

also required for proper functioning of diesel particle filters. Biodiesel generally contains less than 15 ppm 

sulfur. The test for low-sulfur fuel (ASTM D5453) should be used for accurate results instead of D2622, 

which will provide falsely high results caused by the test’s interference with the oxygen in the biodiesel.

• Copper strip corrosion test. This test is used to indicate potential difficulties with copper and bronze fuel 

system components. The requirements for B100 and conventional diesel are identical, and biodiesel meeting 

other D6751 specifications always passes this test. Copper and bronze may not corrode in the presence of 

biodiesel fuel, but prolonged contact with these catalysts can degrade the fuel and cause sediment to form. 

• Cetane number. An adequate cetane number is required for good engine performance. Conventional diesel 

must have a cetane number of at least 40 in the United States. Higher cetane numbers help ensure good cold 

start properties and minimize the formation of white smoke. The ASTM limit for B100 cetane number is set 

at 47, because this is the level identified for “Premium Diesel Fuel” by the National Conference of Weights 

and Measures. Also, 47 has been the lowest cetane number found in U.S. biodiesel fuels. The cetane index 

(ASTM D976) is not an accurate predictor of cetane number for biodiesel or biodiesel blends, because it is 

based on a calculation that uses specific gravity and distillation curve, both of which are different for biodiesel than for petroleum diesel. 

• Cloud point. This is the most commonly used measure of low-temperature operability; fuels are generally 

expected to operate at temperatures as low as their cloud point. The B100 cloud point is typically higher 

than the cloud point of conventional diesel. Cloud point must be reported to indicate biodiesel’s effect on 

the final blend cloud point. Low-temperature properties and strategies for ensuring good low-temperature 

performance of biodiesel blends are discussed in more detail in later sections.

• Carbon residue. This measures the carbon-depositing tendency of a fuel and is an approximation of the tendency for carbon deposits to form in an engine. For conventional diesel fuel, the carbon residue is measured 

on the 10% distillation residue. Because B100 boils entirely at the high end of the diesel fuel range and in a 

very narrow temperature range, it is difficult to leave only a 10% residual when distilling biodiesel. So, biodiesel carbon residue specifies that the entire biodiesel sample be used rather than the 10% distilled residue. 

• Acid number. The acid number for biodiesel is primarily an indicator of free fatty acids (natural degradation 

products of fats and oils) and can be elevated if a fuel is not properly manufactured or has undergone oxidative degradation. Acid numbers higher than 0.50 have been associated with fuel system deposits and reduced 

life of fuel pumps and filters.

• Free and total glycerin. These numbers measure the amount of unconverted or partially converted fats and 

by-product glycerin in the fuel. Incomplete conversion of the fats and oils into biodiesel can lead to high 

total glycerin. Incomplete removal of glycerin can lead to high free glycerin and total glycerin. If these 

numbers are too high, the storage tank, fuel system, and engine can be contaminated. Fuels that exceed 

these limits are highly likely to plug filters and cause other problems. One of the major shortcomings of the 

D6584 gas chromatograph (GC) method is its sensitivity to diesel fuel. Diesel fuel components react differently on the column used in the GC—they make the determination of free glycerin very difficult and 

may damage the column. Thus, many labs are unable to determine free and total glycerin by this method in 

samples with even small amounts of diesel fuel, such as B99.9.

• Phosphorus content. This is limited to 10 ppm maximum in biodiesel because it can damage catalytic converters; phosphorus above 10 ppm can be present in some plant oils. Biodiesel produced in the United States 

generally has phosphorus levels of about 1 ppm.
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 15 

• T90 distillation specification. This specification was incorporated to ensure that fuels have not been contaminated with high boiling materials such as used motor oil. B100 exhibits a boiling point rather than a distillation curve. The fatty acids from which biodiesel are produced are mainly straight-chain HCs with 16 to 18 

carbons that have similar boiling point temperatures. The atmospheric boiling point of biodiesel is generally 

626o to 675oF (330o to 357oC). 

• Oxidation stability. Biodiesel can oxidize during storage and handling, leading to the formation of peroxides, 

acids, gums, and deposits. The minimum oxidation stability requirement is intended to ensure the storage 

stability of B100 and biodiesel blends.

• Cold soak filterability. This is the newest requirement. It was added in 2008 in response to data indicating 

that some B100 could, in blends with petroleum diesel of up to 20%, form precipitates above the cloud point. 

B100 meeting the cold soak filterability requirements does not form these precipitates. This, along with 

cloud point, is needed to predict low-temperature operability. 

The D6751 specification also includes the following workmanship statement: 

The biodiesel fuel shall be visually free of undissolved water, sediment, and suspended matter. 

B100 should be clear, although it may come in a variety of colors. The biodiesel’s color does not indicate fuel quality.

ASTM recently passed specifications for biodiesel blends. These include the allowance of up to 5% biodiesel 

in D975-compliant diesel fuel, with no changes to the allowable diesel fuel performance properties. A separate 

specification for B5 to B20 blends is discussed in Section 4.

3.2 Variation in Biodiesel Properties

As with petroleum-based fuels, the ASTM specifications for biodiesel allow a variety of feedstocks and processes 

to be used in its production. The specifications prescribe a largely feedstock-neutral, performance-based set of 

requirements that ensure the B100 is fit to be used in diesel engines. Biodiesel can be produced commercially 

from a variety of oils and fats:

• Animal fats. Edible, inedible, and all other variations of tallow, lard, choice white grease, yellow grease, 

poultry fats, and fish oils

• Plant oils. Soy, corn, canola, sunflower, rapeseed, cottonseed 

• Recycled greases. Used cooking oils and restaurant frying oils.

Biodiesel can also be made from other oils, fats, and recycled oils such as mustard, palm, coconut, peanut, olive, 

sesame, and safflower oils, trap greases, and even oils produced from algae, fungi, bacteria, molds, and yeast. Some 

properties of finished biodiesel such as cetane number, cloud point, and stability depend heavily on the feedstock. 

Compared with the chemistry of diesel fuel, which contains hundreds of compounds, the chemistries of different 

fats and oils typically used for biodiesel are very similar. Each fat or oil molecule is made up of a glycerin backbone of three carbons, and on each carbon is attached a long-chain fatty acid that reacts with methanol to make 

the methyl ester, or biodiesel. The glycerin backbone is turned into glycerin and sold as a by-product of biodiesel 

manufacturing. The fats and oils contain 10 common types of fatty acids that have 12 to 22 carbons, more than 

90% of which are 16 to 18 carbons. Some of these chains are saturated, some are monounsaturated, and others are 

polyunsaturated. Within the limits of the specifications, the differing levels of saturation can affect some biodiesel fuel properties. 

Each feedstock is set apart from the others because it is made of different proportions of saturated, monounsaturated, and polyunsaturated fatty acids (Figure 3). 
16 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

Under each category of fatty acids in Table 3 is shown its general impact on fuel properties and emissions. These 

are trends only; other factors such as additives may modify these trends.

As with conventional diesel fuel, the best type of biodiesel for your applications will be based on several factors. 

A No. 2 petroleum diesel fuel with a cetane number of 50 and a cloud point of 40oF (4oC) may be suitable for 

December in Texas, but a No. 1 petroleum diesel with a cetane number of 42 and a cloud point of -20oF (-29oC) 

may be best for a December in Minnesota. The considerations and trade-offs are like those made for petroleum 

diesel fuel. The following data provide more detail about B100 properties and considerations.

3.3 Energy Content

With conventional diesel fuels, the inherent energy content of the fuel (typically measured in British thermal 

units [Btu] per gallon) is the largest factor affecting the fuel economy, torque, and horsepower delivered by the 

fuel. The energy content of conventional diesel can vary up to 15% from supplier to supplier and from summer 

to winter. This variability is due to changes in its composition determined by the petroleum feedstock, as well as 

refining and blending practices. No. 2 diesel fuel usually has a higher energy content than No. 1 diesel fuel, and 

blend values are somewhere in between. 

Canola

Safflower

Sunflower

Corn

Olive

Soybean

Peanut

Cottonseed

Yellow Grease

Lard

Beef Tallow

Palm

Coconut

0 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Saturated Monounsaturated Polyunsaturated

Figure 3. Composition of Various Biodiesel Feedstocks in Order of Increasing Saturated Fatty Acid Content

Table 3. Fuel Properties as a Function of Fuel Composition in Diesel Engines

Saturated Monounsaturated Polyunsaturated

Cetane Number High Medium Low

Cloud Point High Medium Low

Stability High Medium Low
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 17 

With biodiesel, or B100, the refining (esterification or transesterification process) and blending methods have 

no significant effect on energy content. B100 varies little because the energy content of the fats and oils used to 

make biodiesel are similar. Therefore, B100 made from most of the common feedstocks will have the same fuel 

economy, power, and torque. Compared with most No. 2 diesel fuel in the United States, B100 has a slightly lower 

energy content (12.5%/lb or 8%/gal). Typical No. 2 diesel fuel has an energy content of around 18,600 Btu/lb. The 

energy in a pound of biodiesel made from several feedstocks is shown in Table 4. Losses in power, torque, and 

fuel economy would be expected to be proportional to the difference in energy content.

The energy content of biodiesel blends and diesel fuel is proportional to the amount of biodiesel in the blend and 

the heating value of the biodiesel and diesel fuel used to make the blend. For example, B20 users experience a 1% 

loss in fuel economy on average and rarely report changes in torque or power.

3.4 Low-Temperature Properties

The low-temperature properties of biodiesel and conventional petroleum diesel are extremely important. Unlike 

gasoline, petroleum diesel and biodiesel can freeze or gel as the temperature drops. Different diesel fuel formulations are sold during the winter in colder climates. If the fuel begins to gel, it can clog filters on dispensing 

equipment and may eventually become too thick to pump. B100 is commonly stored in heated above-ground 

tanks for blending in winter. Important low-temperature performance metrics for handling and blending of 

B100 are as follows:

• Cloud point. The temperature at which small solid crystals are first visually observed as the fuel is cooled. 

Below cloud point, these crystals might plug filters or could drop to the bottom of a storage tank. However, 

fuels can usually be pumped at temperatures below cloud point.

• Pour point. The temperature at which the fuel contains so many agglomerated crystals that it is essentially a 

gel and will no longer flow. Distributors and blenders use pour point as an indicator of whether the fuel can 

be pumped, even if it would not be suitable for use without heating or taking other steps.

These guidelines should be followed for storing biodiesel (B100) in winter:

• B100 should be stored at temperatures at least 5o to 10oF higher than the cloud point. A storage temperature of 40o to 45oF (4o to 7oC) is fine for most B100, although some B100 fuels may require higher storage 

temperatures.

Table 4. Heating Value of Diesel and Some Biodiesel (B100) Fuels14

Fuel Heat of Combustion

Typical No. 2 Diesel About 18,300 Btu/lb

Soy Methyl Ester 15,940 Btu/lb

Canola Methyl Ester 15,861 Btu/lb 

Lard Methyl Ester 15,841 But/lb 

Edible Tallow Methyl Ester 15,881 Btu/lb 

Inedible Tallow Methyl Ester 15,841 Btu/lb 

Low Free Fatty Acid Yellow Grease Methyl Ester 15,887 Btu/lb 

High Free Fatty Acid Yellow Grease Methyl Ester 15,710 Btu/lb
18 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

• B100 can be stored underground in most cold climates without additional considerations because underground storage temperatures are normally above 45oF (7oC). Aboveground storage and handling systems 

should be protected with insulation, agitation, heating systems, or other measures if temperatures regularly 

fall below the cloud point. This precaution includes piping, tanks, and pumping equipment. 

The cloud point of B100 starts at 30o to 32oF (-1o to 0oC) for most plant oils that are composed primarily of monoor polyunsaturated fatty acid chains; the cloud point can go as high as 80oF (27oC) or higher for animal fats or 

frying oils that are highly saturated. Examples of the cloud and pour points of B100 made from various sources 

are listed in Table 5. The pour point of B100 is usually only a few degrees lower than the cloud point, so once 

biodiesel begins to freeze, gelling can proceed rapidly if the temperature drops only a few degrees further.

B100 tanks and fuel lines should be designed for the cold flow properties of the biodiesel used and the local 

climate. Fuel pumps, lines, and dispensers must be protected from the cold and wind chill with properly approved 

heating and insulating equipment. Fuel in aboveground tanks should be heated to 5o to 10oF (-15o to -12oC) 

above the fuel cloud point.

Once crystals begin to form, they will go back into solution as the fuel warms. However, that process can be slow 

if the fuel is heated only slightly above the cloud point. Crystals formed in biodiesel or diesel fuel can drift to the 

bottom of the tank and begin to build up a gel layer. Slow agitation can prevent crystals from building up on the 

tank bottom or, once present in the fuel, can help to bring the crystals back into liquid form. If B100 has gelled 

completely, the B100 should be heated to 100o to 110oF (38o to 43oC) to melt the most highly saturated biodiesel 

components if the fuel needs to be used immediately. Lower temperatures can be used if there is more time to 

allow the biodiesel to liquefy.

Some additive manufacturers provide data that show their cold flow additives can reduce the pour point of a B100 

by as much as 30oF (12oC), but only with very large amounts of additives. At more typical treat rates, benefits 

were below detection levels. 

B100 in the United States cannot be effectively managed with current cold flow additives, as can some petroleum 

diesel or European rapeseed-oil-based biodiesel. The level of saturated compounds in U.S. oils and fats is too 

high for most additives to be effective. Cold flow additives’ effectiveness can also change dramatically, depending 

on the exact type of biodiesel and the processing it has undergone; this is much like the situation with diesel fuel. 

Cold flow additives have been used much more successfully with biodiesel blends. You should work directly with 

the additive manufacturers on this issue.

Table 5. Cold Flow Data for Various B100 Fuels15

Test Method for B100 Fuel Cloud Point (ASTM D2500) Pour Point (ASTM D97)

(oF) (oC) (oF) (oC)

Soy Methyl Ester 32 0 25 -4

Canola Methyl Ester 26 -3 25 -4

Lard Methyl Ester 56 13 55 13

Edible Tallow Methyl Ester 66 19 60 16

Inedible Tallow Methyl Ester 61 16 59 15

Yellow Grease 1 Methyl Ester – – 48 9

Yellow Grease 2 Methyl Ester 46 8 43 6
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 19 

3.5 Cetane Number

Cetane number is a measure of the ignition 

delay (the time from fuel injection into the 

chamber to ignition); higher cetane numbers 

are believed to provide easier starting and 

quieter operation. The ASTM D6751 specification for biodiesel requires a minimum 

cetane number of 47; the cetane number 

required of petroleum diesel fuel is only 

40. B100 produced from highly saturated 

feedstocks (such as lard, tallow, and used 

cooking oils) can have a cetane number of 

60 or higher. Soy-, sunflower-, corn-, and 

canola-based biodiesel will have cetane 

numbers closer to 47. Figure 4 shows the 

cetane numbers of various biodiesel samples 

and compares them with those of diesels.

3.6 Transport and Storage

3.6.1 Stability

Stability can refer to two issues for fuels: long-term storage stability or aging and stability at elevated temperatures or pressures as the fuel is recirculated through an engine’s fuel system. For petroleum diesel, long-term 

storage stability is commonly referred to as oxidative stability. Thermal stability is the common term for the 

stability of fuels at elevated fuel system temperatures. For B100, storage stability is the paramount concern; thus, 

D6751 includes an oxidation stability requirement. 

The oxidation stability test, EN14112 (also referred to as the Oil Stability Index [OSI] or the Rancimat test), 

involves heating a specified quantity of B100 to 230oF (110oC) while air is bubbled through at a specified flow 

rate. The air then passes through a water bath that collects the volatile acids formed in oxidation. A conductivity 

meter is used to monitor the water. A stable B100 can go for many hours under these conditions without forming 

volatile oxidation products. This period of time, before oxidation products form, is called the induction time or 

induction period. The stability requirement in D6751 is that B100 have a minimum three-hour induction time. 

Because this requirement applies at the time of blending, many biodiesel producers make B100 with a four- or 

five-hour induction time. 

In biodiesel, fuel aging and oxidation can lead to high acid numbers, high viscosity, and the formation of gums and 

sediments that clog filters. If the oxidation stability, acid number, viscosity, or sediment measurements exceed the 

limits in ASTM D6751, the B100 is degraded to the point where it is out of specification and should not be used. 

Biodiesel with high oxidation stability (longer induction time) will take longer than biodiesel with low oxidation 

stability to reach an out-of-specification condition. Monitoring the acid number and viscosity of B100 over time can 

indicate whether it is oxidizing. B100 should be tested at receipt to ensure that it is within specification.

In some cases, deposits from the cleaning or solvent effect of B100 have been confused with gums and sediments 

that could form in storage as the B100 ages. Although sediment can clog a filter in either case, care should be 

taken to make sure the reason for the clogging is properly identified. For example, if oxidation stability and acid 

number are within specification, the formation of sediment is most likely due to the cleaning effect and not to 

aging or oxidation.

Guidelines to help identify biodiesel and storage conditions that will provide the highest levels of stability follow: 

• The higher the level of unsaturation, the more likely that the B100 will oxidize. Saturated fatty acids are 

usually stable, and each time the level of unsaturation increases (for example, from a saturated fat to a monoEPA Highway Diesel

CARB Diesel

Lard

Edible Tallow

Inedible Tallow

Yellow Grease 1

Yellow Grease 2

Canola

Soy

0 10 20 30

Cetane Number

40 50 60 70

Figure 4. Cetane Number of Two Petroleum Diesels and Several Biodiesels
20 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

saturated fat), the stability of the fuel decreases by a factor of 10. The points of unsaturation on the biodiesel molecule can react with oxygen, forming peroxides that break down into acids, sediments, and gums. 

• Heat and sunlight will accelerate this process. 

• Certain metals such as copper, brass, bronze, lead, tin, and zinc will accelerate the degradation process and 

form even higher levels of sediment. B100 should not be stored in systems that contain these metals. Metal 

chelating additives, which deactivate these metals, may reduce or eliminate their negative impact. 

• Some types of feedstock processing and biodiesel processing can remove natural antioxidants, potentially 

lessening stability. Plant oils and fats are produced with natural antioxidants—nature’s way of protecting the 

oil from degradation. Bleaching, deodorizing, or distilling oils and fats, either before or as part of the biodiesel 

process, can remove these natural antioxidants; other processes leave the antioxidants in the finished biodiesel. 

• Keeping oxygen from the biodiesel reduces or eliminates fuel oxidation and increases storage life. Commercially, this is done by using a nitrogen blanket on storage tanks or storing biodiesel in sealed drums or totes.

• Antioxidants, whether natural or incorporated as additives, can significantly increase the storage life or 

stability of B100.

The ASTM D4625 test is used to simulate storage in underground storage tanks. The test is accelerated by a 

factor of 4 for petroleum fuels; that is, one week of storage at D4625 conditions (43oC or 110oF, open to air) simulates one month of storage in an underground tank. This acceleration factor has not been validated for B100, but 

it is still a useful guide. ASTM D4625 data (see Figure 5) indicates that B100 will rapidly lose oxidation stability 

3500

3000

2500

2000

1500

1000

500

0

0 2 4 6 8 10 12

Peroxide Value

Weeks

4.21

3.11

6.52

0.45

5.53

7.76

7.26

0.17

Initial OSI, hr

7

6

5

4

3

2

1

0

0 2 4 6 8 10 12

Total Insoluble, mg/100 ml

Weeks

4.21

3.11

6.52

0.45

5.53

7.76

7.26

0.17

Initial OSI, hr

12

10

8

6

4

2

0

0 2 4 6 8 10 12

Oil Stability Index, hr

Weeks

4

3

2

1

0

0 2 4 6 8 10 12

Acid Value

Weeks

Initial OSI, hr

4.21

3.11

6.52

0.45

5.53

7.76

7.26

0.17

2006 Limit of 0.5

2005 Limit of 0.8

Figure 5. ASTM D4625 Long-Term Storage Stability for B100 Samples Having a Range of Initial Induction Periods
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 21 

under these storage conditions, and even a nearly eight-hour induction time sample can be reduced to less than 

three hours in four weeks (simulated four months of storage). Figure 5 also shows that these materials, with one 

exception, are oxidizing and not just losing “oxidation reserve” because of the increasing peroxide value. Acid 

values remain relatively constant for the first four weeks of storage. Insoluble formation does not become significant until after eight weeks (simulated eight months) of storage. 

B100 should not be stored longer than four months unless it has been treated with synthetic antioxidants. Nonoxidizing storage conditions in containers with little head space or under a nitrogen blanket will also be helpful. In 

fact, when B100 is being stored longer than about two months, it should be tested for oxidation stability every two 

weeks. One of the best ways to stabilize biodiesel is to blend it with petroleum diesel.

3.6.2 Microbial Contamination

Biocides are recommended for conventional and biodiesel fuels wherever biological growth in the fuel has been 

a problem. If biological contamination occurs, water contamination should be suspected and will need to be 

controlled because the aerobic fungus, bacteria, and yeast HC-utilizing microorganisms usually grow at the fuelwater interface. Anaerobic colonies, which usually reduce sulfur, can be active in sediments on tank surfaces 

and cause corrosion. Because the biocides work in the water phase, products that are used with diesel fuels work 

equally well with biodiesel.

3.6.3 Cleaning Effect

Methyl esters have been used as low-VOC (volatile organic compound) cleaners and solvents for decades. Methyl 

esters make excellent parts cleaners, and several companies offer methyl esters as a low-VOC, nontoxic replacement for the volatile solvents used in parts washers. Because B100 comprises methyl esters that meet ASTM 

D6751, it will dissolve the accumulated sediments in diesel storage and engine fuel tanks. These dissolved sediments can plug filters. If this happens, it can cause injector deposits and even fuel injector failure. If you plan to 

use or store B100 for the first time, clean the tanks and any parts in the fuel system where sediments or deposits 

may occur before filling the tanks with B100.

The level of cleaning depends on the amount of sediment in the system (if the system is sediment-free there 

should be no effect) as well as the biodiesel blend level (the higher the blend level, the greater the cleaning potential). The cleaning effect is much greater with B100 and blends with 35% or more biodiesel, in comparison to B20 

and lower blends.

Biodiesel spills should be cleaned up immediately, because biodiesel can damage some types of body and engine 

paint. Biodiesel can also remove decals from tanks or vehicles near fueling areas. All materials that are used to 

absorb biodiesel spills should be considered combustible and stored in a safety can. 

3.6.4 Materials Compatibility

B100 will degrade, soften, or seep through some hoses, gaskets, seals, elastomers, glues, and plastics with prolonged exposure. Some testing has been done with materials common to diesel systems, but more data are needed 

on the wide variety of grades and variations of compounds that can be found in these systems, particularly with 

B100 in U.S. applications. Nitrile rubber compounds, polypropylene, polyvinyl, and Tygon® materials are particularly vulnerable to B100. Before handling or using B100, ask the equipment vendor or OEM if the equipment 

is suitable for B100 or biodiesel. In some cases, the vendor may need the chemical family name for biodiesel (the 

methyl esters of fats and oils) to look up the information or even the exact chemical name of some of the biodiesel components, such as methyl oleate, methyl linoleate, methyl palmitate, or methyl stearate. Oxidized biodiesel 

and biodiesel blends can contain organic acids and other compounds that can significantly accelerate elastomer 

degradation. (Published data on B100 material compatibility are summarized in Appendix E.) There have been no 

significant material compatibility issues with B20, unless the B20 has been oxidized.

If your equipment is not compatible with B100, the materials should be replaced with materials such as Teflon, 

Viton, fluorinated plastics, and nylon. Consult B100 suppliers and equipment vendors to determine materials 

compatibility, and ask B100 vendors in other regions what problems they have experienced and what kind of 
22 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

replacement materials they are using. It is advisable to set up a monitoring program to visually inspect the equipment once a month for leaks, seeps, and seal decomposition. It would be wise to continue these inspections even 

after one year, as experience with B100 is still relatively limited. 

3.6.5 Storage Tanks and Dispensing Equipment

Most tanks designed to store diesel fuel will store B100 with no problem. Acceptable storage tank materials 

include aluminum, steel, fluorinated polyethylene, fluorinated polypropylene, Teflon®, and most fiberglass. If you 

are in doubt, contact the tank vendor or check the National Biodiesel Board (NBB) Web site (www.biodiesel.org). 

Brass, bronze, copper, lead, tin, and zinc may accelerate the oxidation of diesel and biodiesel fuels and create fuel 

insolubles (sediments) or gels and salts when reacted with some fuel components. Lead solders and zinc linings 

should be avoided, as should copper pipes, brass regulators, and copper fittings. The fuel or fittings tend to change 

color, and insolubles may plug fuel filters. Affected equipment should be replaced with stainless steel, carbon 

steel, or aluminum. 

In some locales, an Underwriters Laboratories (UL) listing is required by insurance companies or by state or local 

regulations for the tanks used for fuel storage and for equipment used to dispense fuels. (UL is an independent, 

not-for-profit, nongovernmental organization that tests products for public safety.) As biofuels use has become 

more widespread, the issue of UL listing has become a larger concern as UL-certified equipment for biodiesel and 

biodiesel blend service is extremely limited. Vendors must submit examples of their equipment to UL for testing. 

UL testing programs are currently underway for equipment to be used with biodiesel and biodiesel blends, including dispensers, aboveground steel tanks, underground steel tanks, nonmetallic tanks, aboveground and belowground piping, coatings, sumps, and heating equipment. However, until UL certification is available, the lack of 

permissible equipment may be a barrier to biodiesel and biodiesel blend storage and use in some locations. 

3.6.6 Transport

As with petroleum diesel, B100 must be transported in a way that does not lead to contamination. The following 

procedures are recommended for trucks and railcars and are used by distributors and transporters of petroleumderived diesel:

• Ensure that trucks and railcars are constructed of aluminum, carbon steel, or stainless steel. 

• Ensure proper inspection or washout (washout certificate) before loading.

• Check for previous load carried and residual. Generally only diesel fuel or biodiesel is acceptable as a 

residual. If the vessel has not gone through a washout, some residuals (including food products, raw plant 

oils, gasoline, or lubricants) may not be acceptable.

• Ensure that there is no residual water in the tank.

• Check that hoses and seals are clean and made from materials that are compatible with B100.

• Determine the need for insulation or a method to heat truck or rail car contents if shipping during cold 

weather. B100 is challenging to ship in cold weather. In the winter, most B100 is shipped in one of the following ways:

- Hot (or at least warm), in trucks for immediate delivery at 27o to 54oC (80o to 130oF)

- Hot, around 50oC (122oF), in railcars for delivery in seven to eight days (arrives warm if only one week 

has passed since loading)

- Frozen, in railcars equipped with external steam coils (the fuel in the tank cars is melted at the final destination with steam)

- In a blend with winter diesel, kerosene, or another low-cloud-point fuel in either railcars or trucks.

Regardless of how the biodiesel arrives, procedures that prevent the temperature of B100 from dropping below 

its cloud point must be used to store and handle it. The cloud point of the biodiesel, ambient temperatures, and 

the time the fuel is in transport should all be considered when transporting B100 to ensure that the fuel does 

not freeze. 
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 23 

4.0 Biodiesel Blends

This section focuses on blending B100 with petroleum diesel to make B20, but the approach is similar for other 

blend levels, such as B2 or B5. As discussed in the previous sections, the performance properties of B100 can be 

significantly different from those of conventional diesel. Blending biodiesel into petroleum diesel can minimize 

these property differences and retain some of the benefits of B100. B20 is popular because it represents a good 

balance of cost, emissions, cold weather performance, materials compatibility, and ability to act as a solvent. B20 

is also the minimum blend level that can be used for EPAct compliance for covered fleets. 

4.1 Specifications 

4.1.1 B5 and Lower Blends

The specification for conventional diesel fuel, ASTM D975, allows up to 5 vol % biodiesel to be blended into 

compliant diesel fuels. The biodiesel must meet D6751. The biodiesel blend must meet all the numeric requirements for diesel fuel properties specified in D975; none were changed or relaxed to accommodate biodiesel. 

ASTM Method D7371 Standard Test Method for Determination of Biodiesel (Fatty Acid Methyl Esters) Content 

in Diesel Fuel Oil Using Mid Infrared Spectroscopy (FTIR-ATR-PLS Method) must be used to determine the 

biodiesel blend percentage.

4.1.2 B6 to B20 Blends

A new ASTM specification (D7467) was recently published for blends containing 6 vol % to 20 vol % biodiesel. 

The biodiesel must meet D6751. The requirements of this new specification are shown in Table 6. The requirements are based on those in D975, with some additions. The 90% distillation temperature is allowed to be 5oC 

higher than that for D975 diesel fuel. New requirements for acid number, biodiesel content, and oxidation stability 

are included. The specification is designed such that if a D6751-compliant B100 and a D975-compliant diesel fuel 

3.7 Use of B100 and High Blend Levels

Most biodiesel currently in use involves blends of B20 or lower in a variety of applications. The price and lack 

of regulatory incentives have limited the experience with blend levels of B50 and higher. (One market actively 

involved in high blend levels is the underground mining industry, which is trying to limit workers’ exposure to 

diesel PM.) Thus, most of the information in this section is intended for biodiesel use as a blending component. In 

particular, the D6751 specification does not claim to provide biodiesel of adequate quality for use as a pure fuel. If 

you want to use B100 as a fuel, these recommendations should help:

• Contact other B100 users. The NBB has names of individuals and businesses as well as reference materials 

about B100 storage, handling, and use. If you manage a fleet, contact your Fleet Management Association or 

Clean Cities Coalition to find out if anyone near you has experience with B100. Ask your B100 vendor for 

some recommendations. 

• Ask other users what they did, how they did it, how long it took, how much it cost, what problems they 

encountered, how long they have been using B100, and what kinds of engines and equipment they use B100 in. 

• Discuss your needs with your vehicle dealership and ask for advice, including any recommendations from 

European distributors or other U.S. fleet customers. You are probably not alone.

• Replace materials you know will be problematic and institute a monitoring program based on the information presented in Section 3.6.4, Materials Compatibility. 

• Plan and budget for the time and expense of increased fuel filter changes or cleaning your fuel system when 

first starting to use B100.

• Read “Guidance on Blends Above B20” from the NBB.16
24 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

Table 6. ASTM D7467 Specification for Diesel Blends B6 to B20

Property Test Method

 Grade 

B6 to B20 S15 B6 to B20 S500 j B6 to B20 S5000 k

Acid Number, mg KOH/g, max. D664 0.3 0.3 0.3

Viscosity, mm2/s at 40oC D445 1.9–4.1 a 1.9–4.1 a 1.9–4.1a

Flash Point, oC, min D93 52 b 52 b 52 b

Cloud Point, oC, max D2500 c c c

Sulfur Content, (μg/g)d

mass %, max.

mass %, max.

D5453

D2622 e

D129

15

–

–

-

0.05

–

-

-

0.50

Distillation Temperature, oC, 

90% evaporated, max. D86 343 343 343

Ramsbottom carbon residue on 

10% bottoms, mass %, max. D524 0.35 0.35 0.35

Cetane Number, min. D613 f 40 g 40 g 40 g

One of the following must be met:

(1) Cetane index, min. D976-80 e 40 40 40

(2) Aromaticity, vol %, max. D1319-88 e 35 35 -

Ash Content, mass %, max. D482 0.01 0.01 0.01

Water and Sediment, vol %, max. D2709 0.05 0.05 0.05

Copper Corrosion, 3 h @ 50oC, max. D130 No. 3 No. 3 No. 3

Biodiesel Content, % (V/V) DXXXX h 6–20 6–20 6–20 

Oxidation Stability, hours, min. EN14112 6 6 6 

Lubricity, HFRR @ 60oC, micron, max. D6079 520 i 520 i 520 i

a

 if Grade No. 1-D or blends of Grade No. 1-D and Grade No. 2-D diesel fuel are used, the minimum viscosity shall be 1.3 mm2/s.

b If Grade No. 1-D or blends of Grade No. 1-D and Grade No. 2-D diesel fuel are used, or a cloud point of less than -12oC) is specified, the 

minimum flash point shall be 38oC.

c It is unrealistic to specify low-temperature properties that will ensure satisfactory operation at all ambient conditions. However, satisfactory 

operation below the cloud point (or wax appearance point) may be achieved depending on equipment design, operating conditions, and the use 

of flow-improver additives as described in X3.1.2. Appropriate low-temperature operability properties should be agreed upon between the fuel 

supplier and purchaser for the intended use and expected ambient temperatures. Test Methods D4539 and D6371 may be useful to estimate 

vehicle low temperature operability limits when flow improvers are used, but their use with Bxx blends from a full range of biodiesel feedstock 

sources has not been validated. Because of fuel delivery system, engine design, and test method differences, low-temperature operability tests 

may not provide the same degree of protection in various vehicle operating classes. Tenth percentile minimum air temperatures for U.S. locations 

are provided in Appendix X3 as a means of estimating expected regional temperatures. The tenth percentile minimum air temperatures may be 

used to estimate expected regional target temperatures for use with Test Methods D2500, D4539, and D6371. Refer to X3.1.3 for further general 

guidance on test application.

Footnotes d through k for Table 6 continued on next page.

are blended, the resultant blend will meet the specification. However, diesel fuel that does not meet D975 can also 

be used (for example, by having inadequate lubricity, high sulfur, or high aromatics), and biodiesel can be used to 

blend these properties into compliance.
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 25 

4.2 Low-Temperature Properties 

Blending biodiesel with petroleum diesel moderates the low-temperature operability problems of B100 by dilution. Conventional low-temperature operability additives can be used with blends, as these are believed to be 

effective in the petroleum portion of the blend. Research is ongoing to develop additives that are more effective 

with biodiesel blends and for handling B100 in cold weather. When biodiesel is blended with diesel fuel, the key 

variables are the properties of the diesel fuel, the properties of the biodiesel, the blend level, and the effectiveness 

of cold flow additives. 

There are some critical metrics for low-temperature operability. For blends, these include the following:

• Cloud point. The temperature at which small solid crystals are first visually observed as the fuel is cooled 

(ASTM D2500, D5771, D5772, or D5773). Below the cloud point, these crystals might plug filters or drop to 

the bottom of a storage tank. Cloud point is the most widely used and most conservative estimate of the lowtemperature operability limit. However, fuels can usually be pumped at temperatures below the cloud point. 

A related test is for the wax appearance point, ASTM D3117.

• Pour point. The temperature at which the fuel contains so many agglomerated crystals that it is essentially a 

gel and will no longer flow (ASTM D97, D5949, or D5950). Distributors and blenders use the pour point as 

an indicator of whether the fuel can be pumped, even if it would not be suitable for use without heating or 

taking other steps.

• Cold filter plugging point (CFPP). This is the temperature under a standard set of test conditions, as defined in 

ASTM D6371, at which a fuel filter plugs. The CFPP test employs rapid cooling conditions. CFPP results 

more than 10oC below the cloud point should be viewed with suspicion, because they may not reflect the true 

low temperature operability limit. The test simulates the performance of an average or typical vehicle and 

is not protective of the most challenging fuel system designs from a low-temperature operability standpoint, 

which make up roughly one-third of heavy-duty vehicles or one-fifth of light-duty vehicles.

• Low-temperature flow test (LTFT). This test also reports a temperature under a standard set of conditions, 

defined in ASTM D4539, at which a fuel filter plugs. LTFT employs slow cooling at 1oC/h and simulates the 

most severe (and common) fuel system designs in North American heavy-duty trucks from the standpoint of 

low-temperature operability.

It is strongly recommended that you consult Appendix X.4 of ASTM D975 or X.3 of ASTM D7467 to understand 

the history and relative utility of tests for cloud point, CFPP, and LTFT.

B100 cold flow properties depend on the composition, which affects the cold flow properties of blends (Figure 

6 through Figure 11). Measurements of cloud point and pour point are not exact, but have ±2oC (±3.5oF) repeatability. The same is true of diesel fuel. In addition, different No. 2 diesel fuels may have cloud points of -35o to 

d

 Other sulfur limits can apply in selected areas in the United States and in other countries.

e

 These test methods are specified in 40 CFR Part 80.

f

 Calculated cetane index approximation, Test Method D 4737, is not applicable to biodiesel blends.

g Low ambient temperatures as well as engine operation at high altitudes may require the use of fuels with higher cetane ratings. If the diesel fuel 

is qualified under Table 1 of D 975 for cetane, it is not necessary to measure the cetane number of the blend. This is because the cetane number 

of the individual blend components will be at least 40, so the resulting blend will also be at least 40 cetane number.

h

 Where specified, the blend level shall be +/- 2% volume unless a different tolerance is agreed to by the purchaser and the supplier. 

i If the diesel fuel is qualified under Table 1 of D 975 for lubricity, it is not necessary to measure the lubricity of the blend. This is because the 

lubricity of the individual blend components will be at least 520 microns, so the resulting blend will also be at least 520 microns.

j Under U.S. regulations, if Grades B20 S500 are sold for tax-exempt purposes, then, at or beyond terminal storage tanks, it is required by 26 

CFR Part 48 to contain the dye Solvent Red 164 at a concentration spectrally equivalent to 3.9 lb per thousand barrels of the solid dye standard 

Solvent Red 164, or the tax must be collected.

k Under U.S. regulations, Grades B20 S5000 are required by 40 CFR part 80 to contain a sufficient amount of the dye solvent Red 164 so its 

presence is visually apparent. At or beyond terminal storage tanks, they are required by 26 CFR Part 48 to contain the dye Solvent Red 164 at a 

concentration spectrally equivalent to 3.9 lb per thousand barrels of the solid dye standard Solvent Red 26.

Footnotes for Table 6 continued from previous page
26 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

0% 2.5% 5.0% 7.5% 10%

-30.0

Pour Point, °C

Biodiesel Concentration, %

-25.0

-20.0

-15.0

-10.0

0% 2.5% 5.0% 7.5% 10%

-17.5

-15

-10

-7.5

-20.0

Cloud Point, °C

Biodiesel Concentration, %

SME ITME

CME LYGME

LME HYGME

ETME

-12.5

SME ITME

CME LYGME

LME HYGME

ETME

SME ITME

CME LYGME

LME HYGME

ETME

ETME

SME ITME

CME LYGME

LME HYGME

0 20 40 60 80 100

-15

-5

5

15

-25

Cold Filter Plugging Point, °C

Biodiesel Concentration, %

0 2.5% 5.0% 7.5% 10%

-20.00

-15.00

10

-25.00

Cold Filter Plugging Point, °C

Biodiesel Concentration, %

0 20 40 60 80 100

-20

-10

0

10

-30

Pour Point, °C

Biodiesel Concentration, %

0 20 40 60 80 100

-15

-5

5

15

-25

Cloud Point, °C

Biodiesel Concentration, %

SME ITME

CME LYGME

LME HYGME

ETME

SME ITME

CME LYGME

LME HYGME

ETME

Figure 6. Biodiesel/Diesel Blend Cloud Point Test Results

(abbreviations in graphs are defined in reference 18). 

Figure 8. Biodiesel/Diesel Blend Pour Point Test Results

Figure 10. Biodiesel/Diesel Blend Cold Filter Plugging Point 

Test Results

Figure 7. Biodiesel/Diesel Blend Cloud Point Test Results 

(0%–10% Biodiesel Blend Range)

Figure 9. Biodiesel/Diesel Blend Pour Point Test Results 

(0%–10% Biodiesel Blend Range)

Figure 11. Biodiesel/Diesel Blend Cold Filter Plugging Point Test 

Results (0%–10% Biodiesel Blend Range)
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 27 

-5oC (-31o to 23oF) (some fuels can be higher or lower than these figures). No. 1 diesel, jet A, or kerosene may have 

cloud points of -40o to -51oC (-40o to -60oF). Cloud point is the most widely used predictor of the low-temperature 

operability limit. A recent Coordinating Research Council study showed that biodiesel blends (B5 and B20) made 

from B100 meeting D6751-08a would provide operability down to the cloud point. Additives may allow operation 

at even lower temperatures.17

For biodiesel blends prepared from B100 meeting D6751-08a, the cloud point and LTFT will be nearly the same 

value, and CFPP will be 2o to 3oC (3.5o to 5oF) lower, if no low-temperature flow improver additives are used. 

Additives do not usually alter the cloud point, but they can lower LTFT. Thus, for additized fuels LTFT may be a 

better predictor of low-temperature operability.

Blends of No. 1 and No. 2 diesel fuel are frequently used to meet customer cold flow specifications (see Figure 12). Adjusting the blend of 

kerosene (or No. 1 diesel) in the diesel fuel alone 

or with additives can modify the cloud and pour 

point temperatures of B20. An accurate estimate 

of how B20 will perform in the winter months 

requires mixing the biodiesel with the winter 

diesel typically delivered in your area and testing 

the mixture.

Neither ASTM D975 nor ASTM D7467 has a 

specific requirement for the maximum cloud 

point, but the cloud point should be provided to 

the customer. This can be confusing to someone 

new to using diesel fuel or biodiesel. How can 

something be in the specification but not have 

an exact required value? The answer is that the 

cold flow properties needed for the fuel depend 

on where it is being used (for example, Michigan 

or Texas) and what time of year the fuel is being 

used (for example, January or July). A petroleum 

diesel or biodiesel fuel with a cloud point of 7oC 

(20oF) may be fine for a Texas summer, but not for a Michigan winter. 

The appendices to the ASTM D975 and D7467 specifications contain maps of the 10th percentile minimum 

temperature for the central and northern tier states for various winter months. At the 10th percentile temperature, 

only 10% of the days were colder during that month on average, based on data from several decades. Some users 

and distributors use the 10th percentile as the target for their low-temperature operability requirement. Many 

diesel fuel users will specify a cloud point in their purchase contract—for example, that the fuel cloud point be no 

higher than the 10th percentile minimum temperature. Some users do not monitor cold flow properties at all, and 

they rely on their distributors to make sure the low-temperature operability is managed for their location.

The University of Minnesota Center for Diesel Research tested soy B20 made with various diesel fuels available 

in the region. The database of biodiesel blends (0%, 2%, 5%, 10%, 20%, 100%) shows how different diesel fuels 

and soy biodiesel blends alter cold flow properties (cloud point, pour point, and CFPP). CFPP is another measure 

of low-temperature operability that tends to predict an operability limit lower than the cloud point and may not 

protect the most challenging vehicles for low-temperature operability. Some of the data are shown in Figure 13.

No. 1 diesel fuel typically costs more than No. 2, so blenders may prefer to use additives. Many cold flow additives are available for diesel fuel. Most reduce the size of crystals or inhibit crystal formation in some way. Most 

have a limited effectiveness on B100 but work with varying degrees of effectiveness with B20. 

YG 1 YG 2 Veg 1 Veg 2

10

25

35

45

0

Degrees F 

40

30

15

20

5

80/20 is an 80% blend of No. 2 diesel with No. 1 diesel (or kerosene)

60/40 is a 60% blend of No. 2 diesel with 40% No. 1 diesel.

Cloud point of No. 2 is 12°F; cloud point of No. 1 is –54°F.

B100 B20 w 80/20 B20 w D2 B20 w 60/40

Figure 12. Adjusting Cloud Points of B20 Fuels with Blends of No. 1 and 

No. 2 Diesel (YG=yellow grease, Veg=vegetable oil)
28 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

0.0 2.0 4.0 10.0 20.0 100.0

10

20

30

40

% Soy Biodiesel in Low Sulfur No. 2 (a)

-10

0

-20

0.0 2.0 5.0 10.0 20.0 100.0

10

20

30

40

% Soy Biodiesel in Low Sulfur No. 2 (b)

-10

0

-20

0.0 2.0 5.0 10.0 20.0 100.0

5

15

35

% Soy Biodiesel in Low Sulfur No. 2 (c)

-15

-5

0.0 2.0 5.0 10.0 20.0 100.0

10

20

30

40

% Soy Biodiesel in Low Sulfur No. 2 (d)

-10

0

-20

25

0.0 3.0 6.0 15.0 20.0 50.0

-40

-20

40

% Soy Biodiesel in Arctic Diesel

-100

-80

0.0 2.0 5.0 10.0 20.0 100.0

10

30

40

% Soy Biodiesel in 50% No. 1, 

50% No. 2 Low Sulfur

-30

-10

-50

20

0

-60

Cloud Point

Pour Point

C.F.P.P.

Cloud Point

Pour Point

C.F.P.P.

Cloud Point

Pour Point

C.F.P.P.

Cloud Point

Pour Point

C.F.P.P.

Cloud Point

Pour Point

C.F.P.P.

Cloud Point

Pour Point

C.F.P.P.

Figure 13. Cold Flow Properties of Some Soy Biodiesel Blends, oF 
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 29 

Some blenders have specified feedstocks such as soy biodiesel in their purchasing contracts to obtain a biodiesel 

with a lower cloud point (relative to animal-fat-derived biodiesel). A more realistic approach may be to specify the 

cloud point of the B100. This may lock in a certain price range for biodiesel, but it can also ensure that the biodiesel has specific cold weather characteristics. It is important to consider the cost trade-offs of using less expensive 

biodiesel that might be higher in saturates, but require extra No. 1 diesel or additives for low-temperature operability, versus soy biodiesel and No. 2 diesel. A biodiesel supplier may be willing to switch from more highly 

saturated feedstocks in the summer to a more unsaturated feedstock in the winter. If low-temperature operability 

problems occur, a possible solution is to lower the biodiesel content in the blend during the coldest months. Most 

commonly, B20 users require their fuel supplier to ensure adequate low-temperature operability through contractual language. A purchase contract could specify that a fuel must remain crystal free at temperatures as low 

as -26oC (-14oF) (cloud point lower than -26oC) for December, January, and February. Then the blender will work 

independently with the biodiesel and diesel suppliers and the additive firms to address these issues.

4.3 Lubricity

Blending biodiesel into petroleum diesel even 

at low levels can increase the lubricity of diesel 

fuel. As little as 0.25% biodiesel can significantly 

increase fuel lubricity.14 Figure 14 shows the results 

of lubricity testing using the HFRR, the test used 

to determine if diesel fuels meet the ASTM lubricity requirement of a maximum 520 micron wear 

scar diameter. The exact blending level required to 

achieve adequate lubricity depends on the properties of the conventional diesel. Preliminary evidence suggests that 2% biodiesel almost always 

imparts adequate lubricity.

4.4 Blending, Storage, and Transport 

4.4.1 Blending

Most biodiesel users purchase finished B20 or lower blends from their petroleum distributors or biodiesel 

marketers. In this case, the distributor is responsible for ensuring that the biodiesel has been properly blended 

and that the cold flow properties of the finished blend will provide satisfactory performance for the area and 

time of year. Specify in your purchase contract or agreement that the fuel must meet certain low-temperature 

operability requirements.

Biodiesel blending procedures depend on a variety of factors, including the volume of B100 required to make the 

blend, the finished blend level, the volume of blended products being sold, tank and space availability, equipment 

and operational costs, and customer requirements for blends, both now and in the future. Biodiesel is a fuel for 

diesel applications only and is not to be blended with gasoline. 

Generally, biodiesel is blended into diesel fuel via three primary methods: 

• B100 is splash-blended with diesel fuel by the end user in a storage or transport truck.

• B100 is blended (via a variety of means) by a jobber or distribution company and offered for sale as a 

finished blend.

• B100 is blended at a petroleum terminal or rack by a pipeline or terminal company (usually through 

injection blending) and offered as a finished blend. This product is sold directly to customers or to a petroleum jobber or distribution company for further sale to customers. This is the preferred method because it 

ensures complete blending.

0 20 40 60 80 100

300

400

500

700

Volume Percent Biodiesel

HFRR Wear Scar Diameter, microns

No. 2 Diesel

No. 1 Diesel

Maximum Acceptable Scar Diameter 

200

600

Figure 14. HFRR Lubricity as a Function of Biodiesel Content for a 

No. 1 and a No. 2 Diesel Fuel
30 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

The chemical nature of biodiesel allows it to be blended with any kind of distillate or diesel fuel. This includes 

light fuels such as jet fuel, kerosene, No.1 diesel, and military fuels (JP8, JP5), as well as normal diesel fuel such 

as No. 2 diesel for diesel engines and gas turbines and heating oil for boilers and home heating. Once biodiesel 

is blended thoroughly with diesel fuel, it stays together as one fuel and does not separate over time provided it is 

maintained at temperatures above its cloud point. 

In the early days of biodiesel blend use, volumes were too low for the conventional petroleum infrastructure to 

carry and handle the fuel economically. Most of the B20 used was splash-blended by the user after B100 arrived 

from a biodiesel supplier. As volumes increased, customers began to request B20 preblended from their petroleum diesel suppliers. These suppliers would then receive and store the B100, blend the biodiesel with petroleum 

diesel, and supply a finished blend to the customer. In some cases, the supplier might carry B100 and petroleum 

diesel in separate compartments in one truck and blend the two on the customer’s site as the truck was unloaded. 

The B100 should be stored as B20 or as another blend as soon as possible, regardless of the season. B100 is less 

stable than petroleum diesel blends, and cloud point considerations are less of a concern with blends during cold 

weather. If you have only a few B100 customers, you might consider setting aside a tote of B100 indoors or storing 

some underground or in heated tanks, depending on your climate, and blending the rest as soon as possible. 

Always retain a one-quart sample of the diesel and B100 before blending the fuels. Once the customers have run 

through the current batch of fuel with no problems, you can mix them into the new batch of fuel. If any problems 

arise, these samples will help you determine whether they were caused by the fuel or by something else.

Recently, petroleum terminals and pipeline racks have been responding to increasing demand by installing a 

biodiesel blending capability. This is done so jobbers and distributors can receive a biodiesel blend directly from 

the rack and store and distribute only the blended biodiesel. This finished blend can then be sold to fleet or other 

applications that have some type of on-site storage. An increasing number of public pumps and key card pumps 

carry biodiesel blends for individual users or fleets that do not have their own on-site storage capability.

Many blending options are available, depending on your area. As the market matures and volumes continue to 

increase, the point of blending will likely occur further and further upstream in the distribution system, where it 

is most efficient and economical. This is likely to be especially true with lower blends of biodiesel, such as B2. 

Most users find blending their own fuel to be time-consuming and messy, so they increasingly request that their 

petroleum supplier make finished blends available. 

The blending process is usually done by splash blending or in-line blending. 

• Splash blending. Splash blending is appropriate for locations where the biodiesel and diesel fuel are loaded 

separately. In some cases, however, this is appropriate when the fuels are loaded at the same time through 

different incoming sources but at a high enough fill rate that the fuels are sufficiently mixed (several hundred 

gallons per minute for the diesel fuel). In some cases, the tank may need to be recirculated or further mixed 

to thoroughly blend the two fuels. Because biodiesel and diesel fuel mix easily and completely, splash blending can be sufficient to achieve a homogeneous blend, depending on the exact means of adding the fuel, 

the tank geometry, etc. If mixing is not complete, the slightly denser biodiesel will settle to the bottom. If 

the entire load is then pumped into a customer’s tank, this action will usually be enough to cause complete 

mixing. But for loads split between customers, the load must be well mixed at the time of blending.

B20 is frequently blended in bottom-loading tank trucks. The biodiesel is loaded into the tank truck first, 

followed by the diesel fuel. A homogeneous mixture should be obtained if the flow rate of the diesel fuel 

is adequate (several hundred gallons per minute). When the fuels are pumped from the truck into the B20 

storage tank at the point of use, a final mixing occurs. This is generally enough mixing except in cold 

weather, when the ambient temperature is significantly below the B100 cloud point. Putting B100 into a cold, 

empty tank truck can cause the fuel to gel. Then the two fuels mix poorly or not at all. In cold weather, it is 

better to load half the diesel, then the biodiesel, and then the rest of the diesel fuel. 
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 31 

• In-line blending. In-line blending occurs when the biodiesel is added to a stream of diesel fuel as it travels 

through a pipe or hose in such a way that the biodiesel and diesel fuel become thoroughly mixed by the turbulent movement through the pipe. The biodiesel is added slowly and continuously into the moving stream 

of diesel fuel via a smaller line inserted in a larger pipe, or it can be added in small slug or pulsed quantities spread evenly throughout the time the petroleum diesel is being loaded. This is similar to the way most 

additives are blended into diesel fuel today, and it is most commonly used at pipeline terminals and racks. 

In some cases, distributors that carry B100 and petroleum diesel in separate compartments blend the two 

through in-line blending as they are loading fuel into a customer’s tank. 

In-line blending uses two metered pumps and a dual-fuel injection system, and it requires an investment in 

equipment. This approach is the most accurate and reliable for guaranteeing a specific fuel blend. A variety 

of equipment is available for in-line blending. Systems have to be sized for a specific blend level (B2, B20) 

and generally cannot handle both types of blends. 

In general, blending biodiesel is not difficult if you remember that biodiesel is slightly heavier and more viscous 

than diesel fuel, and the more it is mixed, the better.

Biodiesel has a specific gravity of 0.88 in comparison to No. 2 diesel at 0.85 and No. 1 diesel at 0.80. If biodiesel 

is put into an empty tank and diesel fuel is poured slowly on top, it may not blend properly, if at all. Or if you 

fill the tank with diesel and then slowly add biodiesel, it may go directly to the bottom of the tank (like slowly 

pouring honey into a glass of water). Biodiesel is heavier, so it may stay, unmixed, at the bottom of the tank. 

Most pumps draw from the bottom of a fuel tank, and if the fuel is not properly mixed, this bottom layer can 

contain high concentrations of biodiesel. The problems generally manifest themselves in cold months, as the highconcentration biodiesel fuel has a much higher cloud point, leading to plugging of filters and forming a gel layer 

at the bottom of aboveground tanks. Problems also can include leaks from hoses and gaskets that are compatible with B20 but not with higher blends. Because low-temperature operability problems may not occur in the 

summer, and any adverse effects on hoses and gaskets associated with higher blends may take some time to 

develop, users may go for many months without a problem. Another problem occurs when a concentrated layer 

of biodiesel starts to dissolve tank sediments. Filter clogging in warm months can be caused by this condition.

Two simple tests can be performed to determine if a tank has been thoroughly mixed. 

• A top, middle, and bottom sample of the tank (see ASTM D4057 for the proper way to take a representative sample of a tank) can be taken and analyzed for the percent biodiesel using infrared spectroscopy or by 

measuring the specific gravity or density with any available means (e.g., digital density meter, hydrometer). 

If the values vary by no more than 0.006 specific gravity units from top to bottom, the mix is probably 

adequate. The test procedure for the percent biodiesel by infrared spectroscopy is ASTM D7371-07. Several 

instrument companies currently offer relatively inexpensive equipment to measure the percent biodiesel in 

the field, similar to that used for ethanol in gasoline. 

• Put the samples from the three layers in a freezer with a thermometer and check every five minutes until 

the fuel in one sample begins to crystallize. Record that temperature. Then, check every few minutes until 

all three samples show crystallization. Compare the crystallization temperatures on all three samples; they 

should be within 3oC (5oF) of each other. Otherwise, the fuel will require agitation to mix thoroughly. Alternatively, the cloud point of the three samples could be measured, and values should be within 3oC (5oF) of 

each other.

Cold weather blending is a concern in situations in which the diesel fuel temperature falls below the cloud point 

of the B100 being blended. If the diesel fuel temperature is above the cloud point of the final blend, any crystals 

that form during blending should go back into solution. This process can be assisted by blending equipment that 

agitates the two fuels during blending. That agitation helps disperse the fuels and crystals more uniformly and 

can provide some energy to help the crystals dissolve. 
32 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

Consider an example. Small-scale or hand blending shows the cloud point of the B20 blend will be -18oC (0oF), 

the cloud point of the diesel is -23oC (-10oF), and the biodiesel has a cloud point of 1oC (34oF) and is stored at a 

temperature above cloud point. The diesel fuel temperature is -6oC (21oF) on the day you decide to blend. The 

diesel fuel temperature is lower than the cloud point of your B100. This is an acceptable situation because the 

B20 cloud point is below the temperature of your diesel fuel, and the gap between the temperature of the diesel 

fuel and the target B20 cloud point is pretty generous, about 12oC (21oF). Any crystals that form during blending (because the diesel temperature is below the cloud point of the B100) will return to solution. If the gap were 

smaller, say 3oC (5oF), crystals may be slow to return to solution and have a chance to settle out.

Blends should be stored in tanks that can ensure that the fuel temperature will remain above the cloud point of 

the blend. Blended fuels can be stored below ground in most climates. B20 may be stored in aboveground tanks, 

depending on the cloud and pour points of the blended fuel and the local ambient weather conditions. 

4.4.2 Stability

The storage stability of B5 and B20 blends has been examined recently using the D4625 test that simulates underground storage tank conditions. The test is accelerated by a factor of 4, such that one week of test time simulates 

one month of actual storage. Results for B5 blends are shown in Figure 15. Only one B100 shows increased peroxides, acids, or insolubles over the entire 12-week test, and this B100 did not meet the current stability requirement 

of a three-hour induction time. For B100 with a three-hour or longer induction time, the D4625 test shows no 

indication that oxidation is occurring in B5 blends under these test conditions. Based on these results, B5 blends 

1200

1000

800

600

400

200

0

0 2 4 6 8 10 12

Peroxide Value

Weeks

4.2

3.1

6.5

0.5

5.5

7.8

7.3

0.2

Initial OSI, hr

6

5

4

3

2

1

0

0 2 4 6 8 10 12

Total Insoluble, mg/100 ml

Weeks

4.2

3.1

6.5

0.5

5.5

7.8

7.3

0.2

Initial OSI, hr

0.35

0.30

0.25

0.20

0.15

0.10

0.05

0

0 2 4 6 8 10 12

Acid Value

Weeks

Initial OSI, hr

4.2

3.1

6.5

0.5

5.5

7.8

7.3

0.2

Figure 15. D4625 Storage Results for B5 Blends Made from 

B100 with Varying Levels of Oxidation Stability as 

Measured by the OSI Induction Time
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 33 

made from in-specification B100 can be stored for 

up to one year. However, as biodiesel is still a relatively new fuel, we recommend that you consider 

adding a synthetic antioxidant or monitoring the 

condition of the fuel periodically if you store B5 

for longer than a few months.

Figure 16 shows similar results for B20 blends. As 

for B5, only B100 with an oxidation stability level 

below the current specification shows indications 

of oxidation under these conditions. There may be 

some increase in acid value for one of the blends 

from an in-specification B100 after eight weeks, 

although this may be within the repeatability of the 

method. Thus, these results indicate storage of B20 

for at least eight (and perhaps 12) months appears 

feasible under these conditions. Again, because 

biodiesel is still a relatively new fuel, and until 

more experience is gained in longer term storage, we 

recommend the use of a synthetic antioxidant or periodic monitoring until more data are available.

As biodiesel ages in storage, the induction period decreases, the acid number tends to increase and go out of 

specification, gums and varnish can form, and the viscosity can increase. Induction period, acid number, viscosity, and water and sediment tests can be used to ensure that your biodiesel blend meets ASTM specifications for 

either B6 to B20 or diesel fuel. Some data suggest that when oxidized or aged biodiesel is blended with diesel to 

make B20, some sediments and gums soluble in the B100 become insoluble and come out of solution, forming 

sediments. This information is presented as a warning only. You should never blend out-of-specification B100 into 

diesel to make B20. Make sure the induction period, water and sediment, acid number, and viscosity values are 

all in specification before blending.

Thermal stability is generally meant to indicate that the fuel is degrading when it is subjected to high temperatures for a short period, similar to what would be experienced in the fuel injector or fuel system of a modern 

diesel engine. If the fuel degrades in a hot engine, the primary concern is the potential for fuel pump and injector 

fouling or corrosion. Data suggest that thermal stability should not be a concern with biodiesel. 

4.4.3 Cleaning Effect 

Blends of 20% biodiesel or lower minimize any cleaning or solvent effect issues with accumulated sediments in 

tanks, although minor filter plugging may be observed during the initial weeks of B20 use. Blends higher than 

20% should always be stored in clean, dry tanks as recommended for conventional diesel fuel. Using B20 for a 

year or more will probably not adequately clean your tanks and is not a substitute for a thorough tank cleaning 

when preparing for higher level blends or B100 storage.

Most people do not clean their tanks before B20 use, although it is still wise to keep some extra filters on hand 

and monitor potential filter clogging a little more closely than usual when first starting an engine on B20. The 

cleaning effect of the biodiesel in B20 is sufficiently diluted that most problems are insignificant, but a fuel filter 

may plug up when the fuel is first used. Drivers should be aware that sediments in the vehicle system might plug 

fuel filters during the first few weeks of using B20. Any filter clogging with B20, if it occurs at all, typically goes 

away after the first few times the tank is filled. 

Some consumers who did not encounter problems with B20 assume they can switch to higher blends because 

the B20 has already cleaned their tanks. B20 is too dilute to clean tanks, so caution is still warranted with higher 

blends. The cleaning effect should not be an issue with B5 and lower blends.

4.2

3.1

6.5

0.5

5.5

7.8

7.3

0.2

B100 OSI

200

150

100

50

0

0 2 4 6 8 10 12

Oil Stability Index, hr

Weeks

Figure 16. D4625 Storage Results for B20 Blends Made from B100 with 

Varying Levels of Oxidation Stability as Measured by OSI or 

Rancimat Induction Time
34 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

4.4.4 Materials Compatibility

B20 or lower blends minimize most issues associated with materials compatibility. Experiences over the last 10 

years indicate compatibility with all elastomers in diesel fuel systems, even those, such as nitrile rubber, that are 

sensitive to higher blends. Customers should thus continue to check for and fix leaks. 

Improper or lengthy storage of biodiesel or biodiesel blends can result in oxidation and the formation of corrosive 

materials (including organic acids, water, and methanol) that can adversely affect vulnerable materials. Although 

only limited research has been done on this issue, tests indicate the degree of oxidation may be more important 

than the concentration of biodiesel. Unless they are used within a few months, biodiesel and biodiesel blends 

should be stabilized with antioxidants to reduce compatibility issues.

B20 may degrade faster than petroleum diesel if oxidizing metals such as copper, bronze, brass, or zinc are in the 

fueling systems. If filters clog more frequently with B20 than they do with petroleum diesel, the fueling system 

should be checked for these materials and they should be replaced with biodiesel-compatible parts. Typically, 

these metals are found in lead solders, zinc linings, copper pipes, and brass and copper fittings. Stainless steel, 

carbon steel, and aluminum are good replacements. Data on the materials compatibility of biodiesel blends are 

summarized in Appendix E.

5.0 BQ-9000 Program for Supply Chain Management

The biodiesel industry has developed a voluntary quality control program called BQ-9000 for producers and distributors to ensure biodiesel is produced according to ASTM specifications and ensure that consistent procedures 

are followed to prevent contamination and degradation during distribution, storage, and blending. It is managed 

by an independent organization, the National Biodiesel Accreditation Commission. Several engine manufacturers 

recommend the use of biodiesel from BQ-9000 certified sources. Consumers can avoid the need for independent 

testing by purchasing biodiesel fuels from certified distributors. 

The BQ-9000 Program includes accredited producers and certified marketers, depending on which activity a firm 

specializes in. The firm—not the fuel—receives the accreditation, but the fuel supplied by either an accredited 

producer or a certified marketer must meet all applicable standards for sale and use in the United States. In July 

2008, the NBB reported that 25 BQ-9000 accredited producers accounted for more than 70% of the biodiesel 

produced in the United States in 2008. 

To become an accredited producer, a firm must develop a system for monitoring the production of biodiesel 

through proper sampling, testing, storage, sample retention, and shipping protocols, and these protocols must 

be rigorously followed. A certificate of analysis (COA) must be generated for each production lot with a unique 

identification code and analytical results from a sample (see a sample COA in Appendix F). Testing must include 

at least nine parameters of the current ASTM specification: visual appearance, free and total glycerin, flash point, 

acid number, water and sediment, oxidative stability, sulfur, and cloud point. The producer must also ensure 

the transport vehicles are clean and of appropriate construction for distributing biodiesel.

The certified marketer must either purchase B100 from an accredited producer, or conduct fuel quality testing 

on all biodiesel purchased from nonaccredited producers. The certified marketer must also maintain storage and 

distribution procedures that protect the biodiesel’s quality. 

Regular audits of accredited producers and certified marketers ensure that these standards are enforced.

More specific information on all aspects of the BQ-9000 Program can be found at www.bq-9000.org.
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 35 

6.0 Engine Warranties

7.0 Taxes and Incentives

Among the variety of statements about biodiesel use from engine or vehicle manufacturers, some refer to warranty. Engine and vehicle manufacturers provide a materials and workmanship warranty on their products. Such 

warranties do not cover damage caused by some external condition. Thus, if an engine using biodiesel experiences a failure unrelated to the biodiesel use, it must be covered by the OEM’s warranty. Federal law prohibits the 

voiding of a warranty just because biodiesel was used—it has to be the cause of the failure. If an engine experiences a failure caused by biodiesel use (or any other external condition, such as bad diesel fuel), the damage will 

not be covered by the OEM’s warranty.

Many engine OEMs acknowledge biodiesel use by stating their observations about harmful effects (or lack 

thereof) with various blends in their equipment. Most OEMs declared a lack of harmful effects for B5 and lower 

blends, based on a statement by the leading fuel injection equipment suppliers, as long as the biodiesel meets 

ASTM D6751 or the European biodiesel specification. Some OEMs recognize higher blend levels. More evaluation is underway in the diesel engine industry related to biodiesel and its effects on diesel engines. 

Damage directly attributable to biodiesel will not be covered by an engine OEM’s warranty, but may be covered 

by the fuel supplier’s general liability insurance. New biodiesel users should be sure their biodiesel suppliers 

provide liability coverage on the biodiesel and its blends. For an updated list of OEMs and their position statements, visit the NBB Web site at www.biodiesel.org/resources/fuelfactsheets/standards_and_warranties.shtm. 

Biodiesel is not exempt from federal excise taxes, nor is it exempt from most state and local taxes. This means 

that biodiesel and biodiesel blends are taxed at the same rate as diesel fuel. Some states have passed legislation 

that either reduces fuel excise taxes or provides other incentives. For local exceptions to this statement, contact 

local tax authorities.

If you are using B100 or any blend of biodiesel in a vehicle that uses any public road, you are responsible for 

remitting federal, state, and local taxes on the fuel, including the biodiesel fraction, in a timely manner. This 

requirement applies to biodiesel that you make yourself and to B100 that you purchase and use in your own operations. If you are blending B100 that you purchased, and either using the B20 yourself, or selling it to others, you 

are responsible for remitting the federal, state, and local taxes in a timely way. To clarify, most B100 is sold on a 

pretax basis, so the blender or user is responsible for collecting and remitting taxes. For most commercial blend 

users, the blenders have already included the taxes owed in the sale price of the fuel. Check your invoice or talk to 

your supplier if you have questions. The customer is responsible for ensuring the taxes are paid.

The federal government currently offers some incentives related to biodiesel. Grant programs, tax credits for 

blending biodiesel, and investment opportunities in certain refueling infrastructures are available. The DOE 

Clean Cities Program maintains a Web site that summarizes state and local laws and incentives related to alternative fuels at www.eere.energy.gov/cleancities/vbg/progs/laws.cgi. Another good resource for information about 

federal incentives is the NBB Web site at www.biodiesel.org. 

Since 2005, the federal government has offered a blender’s tax credit of $1.00/gal for agri-biodiesel (derived from 

plant oil or animal fat) and $0.50/gal for recycled oil-derived biodiesel. These tax credits expire on December 31, 

2008. The IRS has defined a blending event as adding 1 gallon of diesel fuel to 999 gallons of B100. Thus, it has 

become common to sell and ship B99.9 and B99. If you are blending B99.9 or B99 to make lower level blends, 

you probably cannot claim the blender’s tax credit, since it was already claimed by the party who added the 0.1% 

or 1% diesel fuel.
36 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

8.0 Safety, Health, and Environmental Issues

Biodiesel contains no hazardous materials and is generally regarded as safe. A number of studies have found that 

biodiesel biodegrades much more rapidly than conventional diesel. Users in environmentally sensitive areas such 

as wetlands, marine environments, and national parks have taken advantage of this property by replacing toxic 

petroleum diesel with biodiesel.

Like any fuel, biodiesel will burn; thus, certain fire safety precautions must be taken as described in this section. 

Of much greater concern are biodiesel blends that may contain kerosene or petroleum diesel. Kerosene is highly 

flammable with a flash point of 100° to 162°F (38° to 72°C). Diesel fuel is generally considered flammable; its 

flash point is 126° to 204°F (52° to 96°C). The flash point of biodiesel is higher than 212°F (100C°), so it is considerably less dangerous. However, biodiesel blends will have flash points intermediate to the two liquids. The U.S. 

Department of Transportation (DOT) considers a blend flammable and the Resource Conservation & Recovery 

Act of 1976 (RCRA) considers it to be ignitable if the flash point is lower than 140°F (60°C) or (DOT) combustible if the flash point is 140° to 200°F (60° to 93°C). 

8.1 Signs, Labels, and Stickers

No placards or warning signs are required for the transport of pure biodiesel. However, biodiesel blends with 

diesel and kerosene are required to be transported in placarded trucks if the flash point of the blend is lower than 

200°F (93°C), according to federal DOT regulations. If the flash point is lower than 140°F (60°C), the liquid is 

considered flammable and the Hazard Class 3 flammable placard is required (see Figure 17). Between 

140° and 200°F (60° to 93°C), the liquid is generally considered to be Hazard Class 3 combustible, 

and the combustible placard shown in Figure 17 is 

required for transport. 

Local fire regulations determine the requirements 

for signage on storage containers, but typically, 

tanks containing fuels (including B100) must be 

labeled with NFPA diamonds. The NFPA diamonds 

will indicate whether the fuel is flammable or 

combustible.

8.2 Fire Safety Considerations

Pure biodiesel can be extinguished with dry chemical, foam, halon, CO2, or water spray, although the water 

stream may splash the burning liquid and spread fire. Oil-soaked rags can cause spontaneous combustion if they 

are not handled properly. Before disposal, wash rags with soap and water and dry them in well-ventilated areas. 

Because biodiesel will burn if ignited, keep it away from oxidizing agents, excessive heat, and ignition sources. 

Figure 17. Placards for Transport of Combustible and Flammable Liquids

7.1 Off-Road Diesel

Biodiesel or petroleum diesel intended for off-road use (agriculture, power, boiler fuels, construction, forestry, or 

mining) is not subject to federal excise taxes. However, if it is sold for one of these tax exempt purposes, and no 

tax is collected, the IRS (26 CFR 48.4082-1) requires that it be dyed with the dye solvent Red 164 at a concentration spectrally equivalent to at least 3.9 pounds of the solid dye standard solvent Red 26 per thousand barrels of 

diesel fuel or kerosene.
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 37 

9.0 Frequently Asked Questions 

What is biodiesel made from?

Biodiesel can be made from a variety of renewable sources such as plant oils (soybeans or other crops), recycled cooking grease, or animal fats. These feedstocks are used to manufacture a mixture of chemicals called 

fatty acid methyl esters (i.e., biodiesel).

Which feedstock is best?

Each feedstock can produce a high-quality B100 fuel but with slightly different properties, especially cloud 

point, cetane number, oxidative stability, and NOx emissions. Cost might also factor into the selection process. 

Most operational differences seen with B100 are reduced when B20 is produced. Most remaining differences 

can be managed with additives or diesel fuel blending strategies. 

Does biodiesel affect how my engine operates?

Biodiesel blends of 20% or lower should not noticeably change engine performance. Some users of biodiesel blends notice significant reductions in soot, and CO and HC emissions are reduced. Higher blend levels 

can reduce fuel economy, torque, and power, but they will also produce lower PM, HC, and CO emissions. 

However, NOx may rise at higher blend levels. 

Does using biodiesel void my warranty?

Original equipment manufacturers provide materials and workmanship warranties on their products. Such 

warranties do not cover damage caused by external conditions such as fuel. Thus, if an engine using biodiesel 

experiences a failure unrelated to the biodiesel use, it must be covered by the OEM’s warranty. Federal law 

prohibits the voiding of a warranty just because biodiesel was used—it has to be the cause of the failure. If an 

engine experiences a failure caused by biodiesel (or any other external condition, such as bad diesel fuel), it 

will not be covered by the OEM’s warranty. OEM positions on biodiesel blends and blend levels vary, and can 

be found on the NBB Web site (www.biodiesel.org).

Do I need to modify my vehicle to use biodiesel?

Users’ experiences indicate that no vehicle modifications appear necessary for blends as high as 20% biodiesel 

mixed with diesel fuel. Higher blend levels may require minor modifications to seals, gaskets, and other parts. 

Tank and fuel line/fuel filter heaters (arctic packages) are recommended for blends higher than 20% biodiesel. 

Although a primary focus of NBB and NREL, detailed long-term engine durability data have not been established for B20 in the United States, so good maintenance practices are recommended. 

Do I need to modify my dispensing equipment to use biodiesel?

Dispensing equipment does not need to be modified for blends of 20% biodiesel or lower, unless there is 

an issue with specific elastomers that are not compatible with B20. Occasional fuel filter plugging has been 

reported, and some people filter the biodiesel fuels entering or leaving the tank. Some exposed parts of the 

dispensing systems may need protection from freezing in cold climates. Tank cleaning is recommended before 

switching to B20 fuels.

How do biodiesel (B20 and B100) emissions compare with diesel emissions? 

The EPA has conducted a comprehensive study of 80 biodiesel emission tests in CI engines (see Figure 2 in 

Section 2, which shows emission benefits for different biodiesel blend levels).
38 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

Does biodiesel use raise NOx emissions?

Blends lower than 5% do not have a measurable affect on NOx. For B20 blends, vehicle testing ongoing at 

NREL is finding no significant impact on NOx; however, engine test stand studies find B20 increases NOx 

emissions by about 2% over those of conventional diesel. Some B100 can raise NOx above the certification 

limits of CI engines. The impact of biodiesel on NOx is discussed in Section 2.4.

Biodiesel blends used in heating oil equipment will reduce NOx by 1% for every 1% of biodiesel used in 

the blend.

How much biodiesel is used and produced in the United States? 

The NBB estimated U.S. production capacity for biodiesel at the beginning of 2008 to be 2.24 billion gallons 

per year. During the first four months of 2008, the Energy Information Agency (EIA) estimated that about 196 

million gallons of biodiesel were produced (roughly on track to produce 600 million gallons in 2008). Much of 

the biodiesel production capacity has been built during the last five years. 

Can I use biodiesel in a cold climate?

Users’ experiences with cold weather vary. B20 blends are used in some very cold climates, such as northern 

Minnesota and Wyoming, where temperatures routinely fall below -30°F (1°C) in the winter. For example, 

B20 was used in an airport shuttle fleet for four years in Boston with no problems. Cold flow additives are 

applicable with biodiesel blends. 

Some users have reported using B100 in extremely cold climates, such as in Yellowstone National Park. The 

vehicles were equipped with winterization packages, and no other precautions were noted. Widespread experience with B100 and higher blends in cold climates is lacking in the United States, so users should be alert to 

potential problems and take reasonable steps to prevent them. 

10.0 Information Resources

A number of resources provide additional details and technical information in support of these guidelines. They 

include the following:

The National Biodiesel Board’s online documents library and information number: 

www.biodiesel.org/resources/reportsdatabase/ 

1-800-841-5849 

The National Renewable Energy Laboratory’s technical publications on biodiesel: 

www.nrel.gov/vehiclesandfuels/npbf/pubs_biodiesel.html 

The U.S. Department of Energy’s Alternative Fuels and Advanced Vehicles Data Center: 

http://www.eere.energy.gov/afdc/

The U.S. Department of Energy’s technical publications:

www.eere.energy.gov/biomass/document_database.html 

The U.S. Environmental Protection Agency’s Renewable Fuel Program:

www.epa.gov/otaq/renewablefuels/index.html 

Iowa State University also offers classes in biodiesel production, analytical test methods, and business management and provides an online tutorial on biodiesel: 

www3.me.iastate.edu/biodiesel/Pages/biodiesel1.html.

You may also contact your Clean Cities representative (www.eere.energy.gov/cleancities/) and biodiesel suppliers 

for more information.
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 39 

11.0 Glossary 

Additive: Material added in small amounts to finished fuel products to improve certain properties or 

characteristics.

Antioxidant: Substance that inhibits reactions promoted by oxygen.

Biodiesel: Methyl esters of fatty acids meeting the requirements of ASTM specification D6751.

Biodegradable: Capable of being broken down by the action of microorganisms.

Boiling range: The spread of temperature over which a fuel, or other mixture of compounds, distills.

Cetane index: An approximation that correlates with a diesel fuels aromatic content based on an empirical relationship with density and volatility parameters such as the mid-boiling point; widely mistaken as an approximation of cetane number. This approximation is not valid for biodiesel or biodiesel blends.

Cetane number: A measure of the ignition quality of diesel fuel based on ignition delay in an engine. The higher 

the cetane number, the shorter the ignition delay and the better the ignition quality.

CI: Compression ignition, the ignition process used in a diesel engine.

Cloud point: The temperature at which a sample of a fuel just shows a cloud or haze of wax (or in the case of 

biodiesel, methyl ester) crystals when it is cooled under standard test conditions, as defined in ASTM D2500.

ECRA: Energy Conservation and Reauthorization Act of 1998, amended EPAct to allow qualified fleets to use B20 

in existing vehicles to generate AFV purchase credits, with some limitations. 

Elastomer: A rubber-type material frequently used in vehicle fuel systems (but not necessarily natural or synthetic 

rubber; may also apply to other polymers).

Energy content: The heat produced on combustion of a specified volume or mass of fuel; also known as heating 

value or heat of combustion.

EPAct: Energy Policy Act of 1992. Title III provides incentives to promote the use of alternative fuel vehicles in 

transportation.

FAME: Fatty acid methyl esters. A mono alkyl ester of long-chain fatty acids from naturally occurring plant oils, 

animal fats, and recycled greases.

Fatty acid: Any of the saturated or unsaturated monocarboxylic acids that occur naturally in the form of triglycerides (or mono or diglycerides) or as free fatty acids in fats and fatty oils.

Flash point: The lowest temperature at which vapors from a fuel will ignite when a small flame is applied under 

standard test conditions.

Free fatty acids: Any saturated or unsaturated monocarboxylic acids that occur naturally in fats, oils, or greases 

but are not attached to glycerol backbones. These can lead to high acid fuels and require special processes 

technology to convert into biodiesel.

HC: Hydrocarbon, a compound composed of hydrogen and carbon. Hydrocarbons can refer to fuel components 

and to unburned or poorly combusted components in vehicle exhaust.

Kerosene: A refined petroleum distillate, of which different grades are used as lamp oil, as heating oil, blended 

into diesel fuel, and as fuel for aviation turbine engines.

Lubricity: The ability of a fuel to lubricate.

Microbial contamination: Containing deposits or suspended matter formed by microbial degradation of the fuel.
40 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

OEM: Original equipment manufacturer.

Oxidation: Loosely, the chemical combination of oxygen to a molecule.

Oxidative stability: The ability of a fuel to resist oxidation during storage or use.

Oxygenate: A fuel component that contains oxygen, i.e., biodiesel or ethanol.

PM: Particulate matter, the solid or semi-solid compounds of unburned fuel that are emitted from engines.

Polyunsaturated fatty acids: Fatty acids with more than one double bond.

Pour point: The lowest temperature at which a fuel will just flow when tested under standard conditions, as 

defined in ASTM D97.

Saturation or saturated compound: A paraffinic hydrocarbon or fatty acid, i.e. one with only single bonds and no 

double or triple bonds.

Solvent: A liquid capable of dissolving another substance to form a solution, which is a homogeneous mixture 

composed of two or more substances.

Specific gravity: The ratio of the density of a substance to the density of water.

Splash blending: The fuels to be blended are delivered separately into a tank truck.

Stratification: To separate into layers.

Storage stability: The ability of a fuel to resist deterioration due to oxidation during storage.

Torque: A force that produces rotation.

Viscosity: A measure of the resistance to flow of a liquid.
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 41 

Appendix A: Sample Biodiesel Material Safety Data Sheet

Chemical Product

General Product Name: Biodiesel

Synonyms: Methyl Soyate, Rapeseed Methyl Ester (RME), Methyl Tallowate

Product Description: Methyl esters from lipid sources

CAS Number: Methyl Soyate: 67784-80-9; RME: 73891-99-3; Methyl Tallowate: 61788-71-2

Composition/Information On Ingredients

This product contains no hazardous materials.

Hazards Identification

Potential Health Effects:

INHALATION: Negligible unless heated to produce vapors. Vapors or finely misted materials may irritate the 

mucous membranes and cause irritation, dizziness, and nausea. Remove to fresh air.

EYE CONTACT: May cause irritation. Irrigate eye with water for at least 15 to 20 minutes. Seek medical attention if symptoms persist.

SKIN CONTACT: Prolonged or repeated contact is not likely to cause significant skin irritation. Material is 

sometimes encountered at elevated temperatures. Thermal burns are possible.

INGESTION: No hazards anticipated from ingestion incidental to industrial exposure.

First Aid Measures

EYES: Irrigate eyes with a heavy stream of water for at least 15 to 20 minutes.

SKIN: Wash exposed areas of the body with soap and water.

INHALATION: Remove from area of exposure, seek medical attention if symptoms persist.

INGESTION: Give one or two glasses of water to drink. If gastrointestinal symptoms develop, consult medical 

personnel. (Never give anything by mouth to an unconscious person.)

Fire Fighting Measures

Flash Point (Method Used): 130.0° C min (ASTM 93)

Flammability Limits: None known

EXTINGUISHING MEDIA: Dry chemical, foam, halon, CO2, water spray (fog). Water stream may splash the 

burning liquid and spread fire.

SPECIAL FIRE FIGHTING PROCEDURES: Use water spray to cool drums exposed to fire.

UNUSUAL FIRE AND EXPLOSION HAZARDS: Oil soaked rags can cause spontaneous combustion if not 

handled properly. Before disposal, wash rags with soap and water and dry in well ventilated area. Firefighters 

should use self-contained breathing apparatus to avoid exposure to smoke and vapor.

Accidental Release Measures Spill Clean-Up Procedures

Remove sources of ignition, contain spill to smallest area possible. Stop leak if possible.

Pick up small spills with absorbent materials such as paper towels, “Oil Dry,” sand, or dirt.

Recover large spills for salvage or disposal. Wash hard surfaces with safety solvent or detergent to remove 

remaining oil film. Greasy nature will result in a slippery surface.
42 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

Handling and Storage

Store in closed containers between 50°F and 120°F.

Keep away from oxidizing agents, excessive heat, and ignition sources.

Store and use in well-ventilated areas.

Do not store or use near heat, spark, or flame, store out of sun.

Do not puncture, drag, or slide this container.

Drum is not a pressure vessel; never use pressure to empty.

Exposure Control /Personal Protection

RESPIRATORY PROTECTION: If vapors or mists are generated, wear a NIOSH-approved organic vapor/mist 

respirator.

PROTECTIVE CLOTHING: Safety glasses, goggles, or face shield recommended to protect eyes from mists or 

splashing. PVC-coated gloves recommended to prevent skin contact.

OTHER PROTECTIVE MEASURES: Employees must practice good personal hygiene, washing exposed areas 

of skin several times daily and laundering contaminated clothing before re-use.

Physical and Chemical Properties

Boiling Point, 760 mm Hg:>200°C Volatiles, % by Volume: <2

Specific Gravity (H2O=1): 0.88 Solubility in H2O, % by Volume: insoluble

Vapor Pressure, mm Hg: <2 Evaporation Rate, Butyl Acetate=1: <1

Vapor Density, Air=1: >1

Appearance and Odor: pale yellow liquid, mild odor

Stability and Reactivity

GENERAL: This product is stable and hazardous polymerization will not occur.

INCOMPATIBLE MATERIALS AND CONDITIONS TO AVOID: Strong oxidizing agents

HAZARDOUS DECOMPOSITION PRODUCTS: Combustion produces carbon monoxide, carbon dioxide along 

with thick smoke.

Disposal Considerations

WASTE DISPOSAL: Waste may be disposed of by a licensed waste disposal company. Contaminated absorbent 

material may be disposed of in an approved landfill. Follow local, state, and federal disposal regulations.

Transport Information

UN HAZARD CLASS: N/A

NMFC (National Motor Freight Classification):

PROPER SHIPPING NAME: Fatty acid ester

IDENTIFICATION NUMBER: 144920

SHIPPING CLASSIFICATION: 65

Appendix A: Sample Biodiesel Material Safety Data Sheet
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 43 

Regulatory Information

OSHA STATUS: This product is not hazardous under the criteria of the Federal OSHA Hazard Communication 

Standard 29 CFR 1910.1200. However, thermal processing and decomposition fumes from this product may 

be hazardous, as noted in Sections 2 and 3.

TSCA STATUS: This product is listed on TSCA.

CERCLA (Comprehensive Response Compensation and Liability Act): NOT reportable.

SARA TITLE III (Superfund Amendments and Reauthorization Act):

Section 312 Extremely Hazardous Substances: None

Section 311/312 Hazard Categories: Nonhazardous under Section 311/312

Section 313 Toxic Chemicals: None

RCRA STATUS: If discarded in its purchased form, this product would not be a hazardous waste either by listing 

or by characteristic. However, under RCRA, it is the responsibility of the product user to determine at the 

time of disposal, whether a material containing the product or derived from the product should be classified 

as a hazardous waste (40 CFR 261.20-24)

CALIFORNIA PROPOSITION 65: The following statement is made in order to comply with the California Safe 

Drinking Water and Toxic Enforcement Act of 1986. This product contains no chemicals known to the state 

of California to cause cancer.

Other Information

This information relates only to the specific material designated and may not be valid for such material used in 

combination with any other materials or in any other process. Such information is to the best of the company’s 

knowledge and believed accurate and reliable as of the date indicated. However, no representation, warranty or 

guarantee of any kind, express or implied, is made as to its accuracy, reliability or completeness and we assume 

no responsibility for any loss, damage or expense, direct or consequential, arising out of use. It is the user’s 

responsibility to satisfy himself as to the suitableness and completeness of such information for his own particular use.

Appendix A: Sample Biodiesel Material Safety Data Sheet
44 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

Appendix D: Density and Viscosity as a Function of Temperature

Density as a Function of Temperature

Because the density of biodiesel varies with temperature, and biodiesel is typically sold by volume, the density of 

biodiesel as a function of temperature can be an important factor in biodiesel commerce. The density of biodiesel 

decreases linearly with temperature. Table D-1 shows soy biodiesel density by temperature. At the same temperature, biodiesels from different sources have different densities, so these values should not be used for any fuel 

other than soy biodiesel.

Appendix B: Renewable Identification Number 

As part of the Energy Policy Act of 2005, Congress created a Renewable Fuel Standard (RFS) - a requirement 

that a certain amount of renewable fuel be used in the United States. The RFS was updated and increased in the 

Energy Independence and Security Act of 2007. A Renewable Identification Number is used to track compliance 

with the RFS in terms of volumes of renewable as well as credits, trading, and compliance by obligated parties. 

Additional information is available at EPA’s Web site on the RFS: www.epa.gov/otaq/renewablefuels/index.htm.

Appendix C: Biodiesel Use as an EPAct Alternative Fuel

EPAct was passed by Congress to reduce the nation’s dependence on imported petroleum by requiring certain 

fleets to acquire AFVs, which can operate on nonpetroleum fuels. Compliance with EPAct is met by credits 

awarded for acquisition of AFVs.

ECRA amended EPAct to allow credit for B20 use. DOE’s Biodiesel Fuel Use Credit Interim Final Rule became 

effective in January 2001, allowing covered fleets to meet EPAct requirements by purchasing biodiesel fuel.

One biodiesel fuel use credit, which is counted as one AFV acquisition, is allocated to fleets for each purchase of 

450 gallons of neat biodiesel fuel, for use in diesel vehicles heavier than 8,500 lb gross vehicle weight rating. The 

biodiesel must be neat (B100) or in blends that contain by volume at least 20% biodiesel (B20). Fleets are allowed 

to use these credits to fulfill up to 50% of their EPAct requirements. (Biodiesel fuel providers can meet up to 

100% of their requirements by using biodiesel fuel use credits.) These credits can be claimed only in the year in 

which the fuel is purchased for use, and cannot be traded between fleets. 

For further information, visit the EPAct Web page at 

www.eere.energy.gov/vehiclesandfuels/deployment/fcvt_epact.shtml 
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 45 

Appendix D: Density and Viscosity as a Function of Temperature

Table D-1. Density of Soy Biodiesel as a 

Function of Temperature23

Temperature Density

°F °C Specific 

Gravity lb/gal

35 1.7 0.896 7.48

36 2.2 0.896 7.48

37 2.8 0.896 7.48

38 3.3 0.895 7.47

39 3.9 0.895 7.47

40 4.4 0.895 7.47

41 5.0 0.894 7.46

42 5.6 0.894 7.46

43 6.1 0.894 7.46

44 6.7 0.893 7.45

45 7.2 0.893 7.45

46 7.8 0.892 7.45

47 8.3 0.892 7.44

48 8.9 0.892 7.44

49 9.4 0.891 7.44

50 10.0 0.891 7.44

51 10.6 0.891 7.43

52 11.1 0.890 7.43

53 11.7 0.890 7.43

54 12.2 0.890 7.42

55 12.8 0.889 7.42

56 13.3 0.889 7.42

57 13.9 0.888 7.41

58 14.4 0.888 7.41

59 15.0 0.888 7.41

60 15.6 0.887 7.40

61 16.1 0.887 7.40

62 16.7 0.887 7.40

63 17.2 0.886 7.40

64 17.8 0.886 7.39

65 18.3 0.885 7.39

66 18.9 0.885 7.39

67 19.4 0.885 7.38

Table D-1. Density of Soy Biodiesel as a 

Function of Temperature (cont.)

Temperature Density

°F °C Specific 

Gravity lb/gal

68 20.0 0.884 7.38

69 20.6 0.884 7.38

70 21.1 0.884 7.37

71 21.7 0.883 7.37

72 22.2 0.883 7.37

73 22.8 0.883 7.36

74 23.3 0.882 7.36

75 23.9 0.882 7.36

76 24.4 0.881 7.36

77 25.0 0.881 7.35

78 25.6 0.881 7.35

79 26.1 0.880 7.35

80 26.7 0.880 7.34

81 27.2 0.880 7.34

82 27.8 0.879 7.34

83 28.3 0.879 7.33

84 28.9 0.878 7.33

85 29.4 0.878 7.33

86 30.0 0.878 7.33

87 30.6 0.877 7.32

88 31.1 0.877 7.32

89 31.7 0.877 7.32

90 32.2 0.876 7.31

91 32.8 0.876 7.31

92 33.3 0.876 7.31

93 33.9 0.875 7.30

94 34.4 0.875 7.30

95 35.0 0.874 7.30

96 35.6 0.874 7.29

97 36.1 0.874 7.29

98 36.7 0.873 7.29

99 37.2 0.873 7.29

100 37.8 0.873 7.28
46 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

Appendix D: Density and Viscosity as a Function of Temperature

Viscosity as a Function of Temperature

Fuel viscosity has a significant impact on the operation of engine fuel injection and atomization systems and is 

known to affect engine wear and the rate of injector fouling. Additionally, viscosity can be a factor in the design 

of pumps for the transfer of stockpiled biodiesel. 

Figure D-1 shows the kinematic viscosities predicted from the correlations of three biodiesel fuels over the temperature range of 68° to 572°F (20° to 300°C). 

The relationship between temperature and viscosity typically follows the regression equation:

logη = A + B/T + C/T/T, where

η = viscosity

T = absolute temperature (K).

For the biodiesels tested above, the constants for the best fit regression equation are shown in Table D-2:

0 50 100 150 200 250 300

Temperature (oC)

Kinematic Viscosity (cSt)

0

1

2

3

4

5

6

7

Canola Methyl Ester

Soy Methyl Ester

Fish Oil Ethyl Ester

Figure D-1. Kinematic Viscosity of Three Biodiesel Blends

Table D-2. Constants for Best Fit Regression Equation

Biodiesel Type A B C

Canola Methyl Ester -0.341 -498 338301

Soy Methyl Ester 0.076 -1078 469,741

Fish-Oil Ethyl Ester -0.453 -739 415238
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 47 

Viscosity of Various Biodiesel Blends as a Function of Temperature

Others have found good correlation with measured viscosity when predicting the viscosity of biodiesel blends 

using the standard method for calculating kinematic viscosities of mixtures:

logηB = m1 logη1

 + m2 logη2 , where

ηB = viscosity of the blend

η1

 and η2 = viscosity of the components

m1 and m2

 = mass fraction of the components.

The results of this equation for various blends of a commercial biodiesel are shown in Figure D-2. 

These results suggest that this equation could be used to estimate viscosities of other intermediate blends.

Appendix D: Density and Viscosity as a Function of Temperature

0 20 40 60 80 100

Temperature (oC)

Kinematic Viscosity (cSt)

0

2

4

6

8

10

12

14

100% Biodiesel

75% Biodiesel with No. 2 Diesel

50% Biodiesel with No. 2 Diesel

20% Biodiesel with No. 2 Diesel

No. 2 Diesel

75% Biodiesel with No. 1 Diesel

50% Biodiesel with No. 1 Diesel

20% Biodiesel with No. 1 Diesel

No. 1 Diesel

Figure D-2. Kinematic Viscosity for a Commercial Biodiesel in Various Blends
48 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

Appendix E: Biodiesel Materials Compatibility Summary Tables

Pure biodiesel is not compatible with certain elastomers, metals, and plastics that are commonly used with 

petroleum diesel. Generally, (but not always), biodiesel blends of 20% or lower have a much smaller effect on 

these materials; very small concentrations of biodiesel in B5 or B2 have no noticeable effect on materials compatibility. If in doubt, contact the manufacturer for more information about the compatibility of specific materials 

with biodiesel fuels or fatty methyl esters (see Table E-1).

Elastomers

Table E-1. Elastomer Compatibility with Biodiesel

Material Compatibility with Fresh, Unoxidized Methyl Oleate Unless Noted Reference

Buna-N Not Recommended 3,4

Butadiene Not Recommended 2

Butyl Mild Effect 2,4

Chemraz Satisfactory 4

Ethylene propylene (EPDM) Moderate Effect 2,4

Fluorocarbon Satisfactory 2,4,5

Fluorosilicon Mild Effect; increase swelling 1

Fluorosilicone Mild Effect 2,4

Hifluour Satisfactory 2

Hypalon Not Recommended 2,4

Natural Rubber Not Recommended 2,4

Neoprene Not Recommended 3,4

Neoprene/Chloroprene Not Recommended 2

Nitrile Not Recommended 1,2

Nitrile, high aceto-nitrile Mild Effect with B20, swelling and break strength affected 5

Nitrile, hydrogenated Not Recommended 2,4

Nitrile, peroxide-cured Mild Effect with B20, swelling and break strength affected 5

Nordel Moderate to Severe Effect 3

Nylon Satisfactory 1

Perfluoroelastomer Satisfactory 2

Polypropylene Moderate Effect; increased swelling, hardness reduced 1

Polyurethane Mild Effect; increased swelling 1

Styrene-butadiene Not Recommended 2,4

Teflon Satisfactory 1,3,4

Table E-1 continues on following page
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 49 

Appendix E: Biodiesel Materials Compatibility Summary Tables

Metals

Certain metals may affect the biodiesel by accelerating its oxidation process and creating fuel insolubles. Lead, 

tin, brass, bronze, and zinc significantly increase sediment formation in both B100 and B20. Galvanized metal 

and terne coated sheet metal are not compatible with biodiesel at any blend level.

Table E-1. Elastomer Compatibility with Biodiesel (cont.)

Material Compatibility with Fresh, Unoxidized Methyl Oleate Unless Noted Reference

Viton Satisfactory; type of cure affects compatibility with oxidized biodiesel see 

specific types of Viton below 1,3

Viton A-401C Satisfactory with fresh RME; not recommended for oxidized blends B20 

and above 6

Viton F-605C Satisfactory with fresh RME; not recommended for oxidized blends B20 

and above 6

Viton GBL-S Satisfactory with RME and with all oxidized blends 6

Viton GF-S Satisfactory with RME and with all oxidized blends 6

Wil-Flex Moderate to Severe Effect 3

1

Bessee, G.B. and J.P. Fey. Compatibility of Elastomers and Metals in Biodiesel Fuel Blends. SAE 971690. 1997.

2

Parker O-Ring Handbook, Parker Hannilin Corporation, O-Ring Division, Lexington, KY, 2007. 

3

Chemical Resisitance Guide, Wilden Pump & Engineering Co., Grand Terrace, CA, 2005.

4

O-Ring Chemical Compatibility Guide, www.efunda.com. accessed July 12, 2008.

5

Terry, B., R.L. McCormick, M. Natarajan. Impact of Biodiesel Blends on Fuel System Component Durability. SAE 2006-01-3279, 2006.

6

Thomas, E., R.E. Fuller, K. Terauchi. Fluoroelastomer Compatibility with Biodiesel Fuels, SAE 2007-01-4061, 2007.
50 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

Appendix F: BQ-9000 Sample Certificate of Analysis
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 51 

Appendix F: BQ-9000 Sample Certificate of Analysis
52 • Biodiesel Handling and Use Guide (Fourth Edition) • 2008

References

1 The ASTM standard for B100 to be used as a blend stock is D6751. Diesel fuel is defined in ASTM D975. 

ASTM D396 defines heating oils. A-A-59693A defines B20 for military use.

2 See www.astm.org.

3 See www.astm.org.

4 A copy of the most current ASTM D6751 specifications can be found at www.astm.org. 

5 Sheehan, J.; Camobreco, V.; Duffield, J.; Graboski, M.; Shapouri, H. An Overview of Biodiesel and Petroleum 

Diesel Life Cycles, NREL/TP-580-24772, National Renewable Energy Laboratory, Golden, CO, 1998.

6 Hill, J.; Nelson, E.; Tilman, D.; Polasky, S.; Tiffany, D. “Environmental, economic and energetic costs and benefits of biodiesel and ethanol blends.” Proc. Natl. Acad. Sciences, 103, 11206-11210, 2006.

7 Huo, H.; Wang, M.; Bloyd, C.; Putsche, V. Life-Cycle Assessment of Energy and Greenhouse Gas Effects of 

Soybean-Derived Biodiesel and Renewable Fuels, ANL/ESD/08-2, Argonne National Laboratory, Illinois, 2008.

8 Thirty nine studies were ultimately used in the EPA analysis in Figure 1.

9 Yanowitz, J., McCormick, R.L. In preparation.

10 Krishna, C.R. Biodiesel Blends in Space Heating Equipment, NREL/SR-510-33579. National Renewable Energy 

Laboratory, Golden, CO, 2003.

11 Batey, J.E. Interim report of test results, Massachusetts Oilheat Council Biodiesel Project, 2002. 

12Environmental Protection Agency. Draft Technical Report, A Comprehensive Analysis of Biodiesel Impacts on 

Exhaust Emissions, EPA420-P-02-001, 2002; www.epa.gov/OMS/models/biodsl.htm.

13Coordinating Research Council. Biodiesel Blend Low-Temperature Performance Validation, 2006; www.crcao.

com/reports/recentstudies2008/DP-2a-07/CRC%20650.pdf.

14 Kinast, J.A. Production of Biodiesels from Multiple Feedstocks and Properties of Biodiesels and Biodiesel/

Diesel Blends: Final Report; Report 1 in a Series of 6, p. 13. NREL/SR-510-31460. National Renewable Energy 

Laboratory, Golden, CO, 2003.

15 Kinast, J.A. Production of Biodiesels from Multiple Feedstocks and Properties of Biodiesels and Biodiesel/

Diesel Blends: Final Report, 2003. 

16 See www.biodiesel.org/pdf _ files/fuelfactsheets/Use_of _Biodiesel_Blends_above_%2020.pdf.

17 CRC. Biodiesel Blend Low-Temperature Performance Validation, 2008; www.crcao.com/reports/recentstudies2008/DP-2a-07/CRC%20650.pdf 

18 SME = soy methyl ester, CME = canola methyl ester, LME = lard methyl ester, ETME = edible tallow methyl 

ester, ITME = inedible tallow methyl ester, LYGME = low free fatty acid yellow grease, HYGME = high free 

fatty acid yellow grease. Since these tests, we have found that the free fatty acid content of the starting feedstock, whether it is yellow grease or some type of animal fat, has no effect on fuel properties. So LYGME and 

HYGME can be viewed as two different samples of yellow grease methyl esters.

19 ASTM D4057. Standard Practice for Manual Sampling of Petroleum and Petroleum Products.

20NBB quality program, BQ-9000, www.bq-9000.org/.

21 Table 10.4, Biodiesel Overview. www.eia.doe.gov/mer/pdf/pages/sec10_8.pdf

22NBB. “What’s a RIN, and What Do I Do With It?” www.biodiesel.org/news/RFS/20070919_BDMLetterRINSSept07.pdf.

23Tat, M.E.; van Gerpen, J.V. The Specific Gravity of Biodiesel and Its Blends with Diesel Fuel. JAOCS, 77, 2, 

115-119, 2000.
 2008 • Biodiesel Handling and Use Guide (Fourth Edition) • 53 

Acknowledgements

This publication was prepared by the National Renewable Energy Laboratory, a U.S. Department of Energy national 

laboratory, with the assistance of Janet Yanowitz of Ecoengineering, Inc., and Richard Nelson of Enersol Resources.

Every effort has been made to ensure that this manual is accurate, complete, and comprehensive at the time of publication. 

It is intended to be used as a guide and resource document.
Printed with a renewable-source ink 

on paper containing at least 50% wastepaper 

including 10% postconsumer waste

NREL/TP-540-43672 

Revised January 2009

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

Office of Energy Efficiency & Renewable Energy

National Renewable

Energy Laboratory

Innovation for Our Energy Future