The Biodiesel Handbook

The second edition of this invaluable handbook covers converting vegetable oils, animal fats, and used oils into biodiesel fuel. The Biodiesel Handbook delivers solutions to issues associated with biodiesel feedstocks, production issues, quality control, viscosity, stability, applications, emissions, and other environmental impacts, as well as the status of the biodiesel industry worldwide.

• Incorporates the major research and other developments in the world of biodiesel in a comprehensive and practical format
• Includes reference materials and tables on biodiesel standards, unit conversions, and technical details in four appendices
• Presents details on other uses of biodiesel and other alternative diesel fuels from oils and fats

• Language: English
• Publisher: Elsevier Science
• Release date: Aug 13, 2015
• ISBN: 9780983507260

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The Biodiesel Handbook

Second Edition

Gerhard Knothe

Jürgen Krahl

Jon Van Gerpen

Table of Contents

Cover image

Title page

Copyright

Preface to the Second Edition

Preface to the First Edition

Contributing Authors

Chapter 1: Introduction

What Is Biodiesel?

Why are Vegetable Oils and Animal Fats Transesterified to Alkyl Esters (Biodiesel)?

Why Can Vegetable Oils, Animal Fats, and Their Derivatives be Used as (Alternative) Diesel Fuel?

Chapter 2: History of Vegetable Oil-Based Diesel Fuels

Rudolf Diesel

Background and Fuel Sources

Technical Aspects

The First Biodiesel

Biodiesel Since the 1970s

Chapter 3: Basics of Diesel Engines and Diesel Fuels

Introduction

Diesel Combustion

New Technologies

Chapter 4: Biodiesel Production

4.1 Basics of the Transesterification Reaction

4.2 Alternate Feedstocks and Technologies for Biodiesel Production

4.3 Catalysis in Biodiesel Processing

4.4 Ion Exchange Resins in Biodiesel Processing

Chapter 5: Analytical Methods

5.1 Analytical Methods for Biodiesel

5.2 A Sensor for Discrimination of Fossil Diesel Fuel, Biodiesel, and Their Blends

Chapter 6: Fuel Properties

6.1 Cetane Numbers—Heat of Combustion—Why Vegetable Oils and Their Derivatives Are Suitable as a Diesel Fuel

6.2 Viscosity of Biodiesel

6.3 Cold Weather Properties and Performance of Biodiesel

6.4 Oxidative Stability of Biodiesel

6.5 Biodiesel Lubricity and Effect of Biodiesel on Lubricants

6.6 Biodiesel Fuels: Biodegradability, Biological and Chemical Oxygen Demand, and Toxicity

6.7 Soybean Oil Composition for Biodiesel

Chapter 7: Exhaust Emissions

7.1 Impacts of Biodiesel Fuel on Pollutant Emissions from Diesel Engines

7.2 Ultrafine Particles from a Heavy Duty Diesel Engine Running on Rapeseed Oil Methyl Ester

Chapter 8: Current Status of the Biodiesel Industry

8.1 Biodiesel in the United States

8.2 Biodiesel in Germany and the European Union

8.3 Biodiesel in South America

8.4 Biodiesel in Asia

8.5 Biodiesel in Japan

8.6 Environmental Implications of Biodiesel (Life-Cycle Assessment)

8.7 Potential Production of Biodiesel in the United States

Chapter 9: Other Uses of Biodiesel

Overview

Fuel Additives

Other Energy-related Applications

Other Applications

Chapter 10: Other Alternative Diesel Fuels from Vegetable Oils and Animal Fats

Introduction

Combustion of Vegetable Oils and Fats

Dilution with Petrodiesel

Microemulsions and Co-Solvent Blends

Pyrolysis

Hydroprocessing (Deoxygenation)

Outlook

Symbols

Chapter 11: Glycerol Technology Options for Biodiesel Industry

Introduction

Crude Glycerol

Refining of Crude Glycerol

Physical Properties of Glycerol

Value-Added Glycerol Markets

Low-Value High-Volume Glycerol Markets

Glycerol Esters and Polymer Applications

Summary

Appendix A: Technical Tables

Appendix B: Biodiesel Standards

Appendix C: Unit Conversions

Appendix D: Internet Resources

Index

Copyright

AOCS Mission Statement

To be a global forum to promote the exchange of ideas, information, and experience, to enhance personal excellence, and to provide high standards of quality among those with a professional interest in the science and technology of fats, oils, surfactants, and related materials.

AOCS Books and Special Publications Committee

M. Mossoba, Chairperson, U.S. Food and Drug Administration, College Park, Maryland

R. Adlof, USDA, ARS, NCAUR-Retired, Peoria, Illinois

M.L. Besemer, Besemer Consulting, Rancho Santa, Margarita, California

W.C. Byrdwell, USDA, ARS, BHNRC, FCMDL, Beltsville, Maryland

P. Dutta, Swedish University of Agricultural Sciences, Uppsala, Sweden

Y.-S. Huang, Yuanpei University of Science and Technology, Taiwan

L. Johnson, Iowa State University, Ames, Iowa

H. Knapp, DBC Research Center, Billings, Montana

G. Knothe, USDA, ARS, NCAUR, Peoria, Illinois

D. Kodali, Global Agritech Inc., Minneapolis, Minnesota

G.R. List, USDA, NCAUR-Retired, Consulting, Peoria, Illinois

J.V. Makowski, Windsor Laboratories, Mechanicsburg, Pennsylvania

T. McKeon, USDA, ARS, WRRC, Albany, California

R. Moreau, USDA, ARS, ERRC, Wyndmoor, Pennsylvania

A. Sinclair, RMIT University, Melbourne, Victoria, Australia

P. White, Iowa State University, Ames, Iowa

R. Wilson, USDA, REE, ARS, NPS, CPPVS-Retired, Beltsville, Maryland

AOCS Press, Urbana, IL 61802

©2010 by AOCS Press. All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means without written permission of the publisher.

ISBN: 978-1-893997-62-2

Library of Congress Cataloging-in-Publication Data

The biodiesel handbook / editors, Gerhard Knothe, Jürgen Krahl, Jon Van Gerpen. – 2nd ed.

p. cm.

Includes bibliographical references and index.

ISBN 978-1-893997-62-2 (alk. paper)

1. Biodiesel fuels. I. Knothe, Gerhard. II. Krahl, Jürgen, 1962- III. Van Gerpen, Jon Harlan.

TP359.B46B56 2009

662′.669–dc22

2010009331

Printed in the United States of America.

15 14 13 12 11 10 6 5 4 3 2 1

The paper used in this book is acid-free and falls within the guidelines established to ensure permanence and durability.

Preface to the Second Edition

Five years have passed since the first edition of The Biodiesel Handbook was published. These years have seen a significant increase in biodiesel production around the world, followed by a decrease in many significant biodiesel-producing countries, due partially to the general economic climate as well as changing legislative and regulatory environments. We are optimistic that as the world economy recovers biodiesel production will increase and exceed previous levels.

In the meantime, research on biodiesel has not only continued unabated but has increased significantly, rendering a necessary update of The Biodiesel Handbook. The outline of the book remains the same as that of the first edition. We hope that this second edition incorporates the major research and other developments in the world of biodiesel in a comprehensive fashion and that the reader may find it useful.

As mentioned in the preface to the first edition, any reader noticing an error or inconsistency or having a suggestion for improving this book is encouraged to contact us.

The second edition has again been compiled from the contributions of many authors, who graciously agreed to do so. We are very grateful to all of them. Last but not least, we again express our sincere and deep appreciation to the staff of AOCS Press for their professionalism and cooperation.

Gerhard Knothe, Jürgen Krahl and Jon Van Gerpen

Preface to the First Edition

The technical concept of using vegetable oils or animal fats or even used oils as a renewable diesel fuel is a fascinating one. Biodiesel is now the form in which these oils and fats are being used as neat diesel fuel or in blends with petroleum-based fuels.

The concept itself may appear simple, but that appearance is deceiving since the use of biodiesel is fraught with numerous technical issues. Accordingly, many researchers around the world have dealt with these issues and in many cases devised unique solutions. This book is an attempt to summarize these issues, to explain how they have been dealt with, and to present data and techical information. Countless legislative and regulatory efforts around the world have helped pave the way toward the widespread application of the concept. This book addresses these issues also. To complete the picture, chapters on the history of vegetable oil-based diesel fuels, the basic concept of the diesel engine, and glycerol, a valuable byproduct of biodiesel production, are included.

We hope that the reader may find the information in this book useful and stimulating and that most of the significant issues regarding biodiesel are adequately addressed. If a reader notices an error or inconsistency or has a suggestion to improve a possible future edition of this book, he or she is encouraged to contact us.

This book has been compiled from the contributions of many authors, who graciously agreed to do so. We express our deepest appreciation to all of them. We also sincerely thank the staff of AOCS Press for their professionalism and cooperation in bringing the book to print.

Gerhard Knothe, Jürgen Krahl and Jon Van Gerpen

Contributing Authors

Teresa L. Alleman,     National Renewable Energy Laboratory, Golden, CO 80401

Rajiv Banavali,     Honeywell Inc., Morristown, NJ 07960

Ralf Bantzhaff,     BERU AG, Ludwigsburg, Germany

Dieter Bockey,     UFOP (Union for Promoting Oilseed and Protein Plants), 10117 Berlin, Germany

Neil A. Bringe,     Monsanto Co., St. Louis, MO 63167

Jürgen Bünger,     BGFA – Research Institute of Occupational Medicine, Bochum, Germany

Beth J. Calabotta,     Monsanto Co., Saint Louis, MO 63167

Claudiney Soares Cordeiro,     Federal University of Parana, Curitiba, PR, Brazil

Robert O. Dunn,     USDA, ARS, NCAUR, Peoria, IL 61604

Sven O. Gärtner,     IFEU-Institute for Energy and Environmental Research, Heidelberg, Germany

Jon Van Gerpen,     Department of Biological and Agricultural Engineering, University of Idaho, Moscow, ID 83844

Michael J. Haas,     USDA, ARS, ERRC, Wyndmoor, PA 19038

Steve Howell,     MARC-IV Consulting Inc., Kearney, MO 64060

Hiroaki Imahara,     Graduate School of Energy Science, Kyoto University, Kyoto, Japan

Joe Jobe,     National Biodiesel Board, Jefferson City, MO 65101

Gerhard Knothe,     USDA, ARS, NCAUR, Peoria, IL 61604

Jürgen Krahl,     University of Applied Sciences, Coburg, Germany

Arno Marto,     BERU AG, Ludwigsburg, Germany

Robert L. McCormick,     National Renewable Energy Laboratory, Golden, CO 80401

Gregory Möller,     Department of Food Science and Technology, University of Idaho, Moscow, ID 83844

David A. Morgenstern,     Monsanto Co., Saint Louis, MO 63167

Bryan R. Moser,     USDA, ARS, NCAUR, Peoria, IL 61604

Axel Munack,     Institute of Technology and Biosystems Engineering, Federal Agricultural Research Center, Braunschweig, Germany

Charles L. Peterson,     Department of Biological and Agricultural Engineering (Emeritus), University of Idaho, Moscow, ID 83844

Luiz Pereira Ramos,     Federal University of Parana, Curitiba, PR, Brazil

Guido A. Reinhardt,     IFEU-Institute for Energy and Environmental Research, Heidelberg, Germany

Yvonne Ruschel,     APL – Automobil-Prüftechnik Landau GmbH, Office Wolfsburg, Wolfsburg, Germany

Shiro Saka,     Graduate School of Energy Science, Kyoto University, Kyoto, Japan

Olaf Schröder,     Institute of Technology and Biosystems Engineering, Federal Agricultural Research Center, Braunschweig, Germany

Alfred K. Schultz,     Rohm & Haas Co., Spring House, PA 19477

Hermann Speckmann,     Institute of Technology and Biosystems Engineering, Federal Agricultural Research Center, Braunschweig, Germany

Galen J. Suppes,     University of Missouri, Columbia, MO 65211

Mohd. Basri Wahid,     Malaysian Palm Oil Board, Selangor, Malaysia

Janet Yanowitz,     Ecoengineering, Inc., Boulder, CO

1

Introduction

Gerhard Knothe,     USDA, ARS, NCAUR, Peoria, IL

What Is Biodiesel?

The major components of vegetable oils and animal fats are triacylglycerols (often also called triglycerides). Chemically, triacylglycerols are esters of fatty acids with glycerol (1,2,3-propanetriol; glycerol is often also called glycerine). The triacylglycerols of vegetable oils and animal fats typically contain several different fatty acids. Thus, different fatty acids can be attached to one glycerol backbone. The different fatty acids that are contained in the triacylglycerols comprise the fatty acid profile (or fatty acid composition) of the vegetable oil or animal fat. As different fatty acids have different physical and chemical properties, the fatty acid profile is probably the most important parameter influencing the properties of a vegetable oil or animal fat.

For obtaining biodiesel, the vegetable oil or animal fat is subjected to a chemical reaction termed transesterification. In that reaction, the vegetable oil or animal fat is reacted in the presence of a catalyst (usually a base) with an alcohol (usually methanol) to give the corresponding alkyl esters (when using methanol, the methyl esters) of the fatty acid mixture that is found in the parent vegetable oil or animal fat. Fig 1.1 depicts the transesterification reaction. While the transesterification reaction formally requires a molar ratio of alcohol to oil of 3:1 as shown in Fig. 1.1, in practice a molar ratio of 6:1 needs to be applied in order for the reaction to proceed properly to high yield. Approximate weights of the reactants in the transesterification process are also given in Fig. 1.1.

Fig. 1.1 The transesterification reaction. R is a mixture of various fatty acid chains. The alcohol used for producing biodiesel is usually methanol (R = CH3).

Biodiesel can be produced from a great variety of feedstocks. These feedstocks include most common vegetable oils (soybean, cottonseed, palm, peanut, rapeseed /canola, sunflower, safflower, coconut, etc.) and animal fats (usually tallow) as well as waste oils (used frying oils, etc.). Which feedstock is used depends largely on geography. Depending on the origin and quality of the feedstock, changes to the production process may be necessary.

Biodiesel is miscible with petrodiesel in all ratios. This has led to the use of blends of biodiesel with petrodiesel instead of neat biodiesel in many countries. It is important to note that blending with petrodiesel is not biodiesel. Often blends with petrodiesel are denoted by acronyms such as B20 which is a blend of 20% biodiesel with petrodiesel. Of course, the untransesterified vegetable oils and animal fats should also not be termed biodiesel.

Methanol is used as alcohol for producing biodiesel because it is the least expensive alcohol, although other alcohols, for example ethanol or iso-propanol, may afford a biodiesel fuel with better fuel properties. Often the resulting product is also called FAME (fatty acid methyl esters) instead of biodiesel. Although other alcohols can by definition give biodiesel, many now existing standards are designed in such a fashion that only methyl esters can be used as biodiesel when observing the standards.

Biodiesel has several distinct advantages compared to petrodiesel besides being fully competitive with petrodiesel in most technical aspects:

• Derived from a renewable domestic resource, thus reducing dependence on and preserving petroleum.

• Biodegradability.

• Reduces most regulated exhaust emissions (with the exception of nitrogen oxides, NOx).

• Higher flash point leading to safer handling and storage.

• Excellent lubricity. This fact is steadily gaining significance with the advent of low-sulfur petrodiesel fuels, which have significantly reduced lubricity. Adding biodiesel at low levels (1-2%) restores the lubricity.

Some problems associated with biodiesel are its inherent higher price, which in many countries is offset by legislative and regulatory incentives or subsidies in the form of reduced excise taxes, slightly increased NOx exhaust emissions (as mentioned above), stability when exposed to air (oxidative stability), and cold flow properties which are especially relevant in North America. The higher price can also be (partially) offset by the use of less expensive feedstocks which has sparked the interest in materials such as waste oils (for example, used frying oils).

Why are Vegetable Oils and Animal Fats Transesterified to Alkyl Esters (Biodiesel)?

The major reason that vegetable oils and animal fats are transesterified to alkyl esters (biodiesel) is that the kinematic viscosity of the biodiesel is much closer to that of petrodiesel. The high viscosity of untransesterified oils and fats leads to operational problems in the diesel engine such as deposits on various engine parts. While there are engines and burners that can use untransesterified oils, the vast majority of engines require the lower viscosity fuel. Typical kinematic viscosity ranges of vegetable oils and biodiesel (in form of methyl esters) are also shown in Fig. 1.1.

Why Can Vegetable Oils, Animal Fats, and Their Derivatives be Used as (Alternative) Diesel Fuel?

The fact that vegetable oils, animal fats, and their derivatives such as alkyl esters are suitable as diesel fuel demonstrates that there must be some similarity to petrodiesel fuel or, at least, to some of its components. Probably the fuel property that shows this suitability best is the cetane number (see Chapter 6.1).

Besides ignition quality as expressed by the cetane scale, several other properties determine the quality of a biodiesel fuel. Heat of combustion, pour point, cloud point, (kinematic) viscosity, oxidative stability and lubricity are probably the most important of these other properties. Biodiesel standards such as ASTM D6751 in the United States and EN 14214 in Europe contain numerous other specifications, which often relate to production or storage issues, to ensure that biodiesel can be used in a diesel engine.

2

History of Vegetable Oil-Based Diesel Fuels

Gerhard Knothe,     USDA, ARS, NCAUR, Peoria, IL

Rudolf Diesel

That vegetable oils and animal fats were investigated as diesel fuels well before the energy crises of the 1970s and early 1980s sparked renewed interest in alternative fuels is generally well known. It is also known that Rudolf Diesel (1858-1913), the inventor of the engine that bears his name, had some interest in these fuels. However, the early history of vegetable oil-based diesel fuels is often presented inconsistently and facts that are not compatible with Diesel’s own statements can be frequently encountered.

Therefore it is appropriate to begin this history with the words of Diesel himself in his book Die Entstehung des Dieselmotors (Diesel 1913a; translatable to The Development (or Creation or Rise or Coming) of the Diesel Engine) in which he describes when the first seed of developing what was to become the diesel engine was planted in his mind. On p. 1 (in the first chapter entitled The Idea of the book), Diesel states (translated): "When my highly respected teacher, Professor Linde, explained to his listeners during the lecture on thermodynamics in 1878 at the Polytechnikum in Munich (note: now the Technical University of Munich) that the steam engine only converts 6-10% of the available heat content of the fuel into work, when he explained Carnot’s theorem and elaborated that during the isothermal change of state of a gas all transferred heat is converted into work, I wrote in the margin of my notebook: Study, if it isn’t possible to practically realize the isotherm! At that time I challenged myself! That was not yet an invention, not even the idea for it. From then on, the desire to realize the ideal Carnot process determined my existence. I left the school, joined the practical side, had to achieve my standing in life. The thought constantly pursued me."

This statement by Diesel clearly shows that he approached the development of the diesel engine from a thermodynamic point of view. The objective was to develop an efficient engine. The currently relatively common assertion that Diesel developed his engine specifically to use vegetable oils as fuel is therefore incorrect.

On p. 115 of his book (in Chapter B Liquid Fuels, beginning p. 94), Diesel addresses the use of vegetable oils as a fuel (again translated from German): "For sake of completeness it needs to mentioned that already in the year 1900 plant oils were used successfully in a diesel engine. During the Paris Exposition in 1900, a small diesel engine was operated on arachide (peanut) oil by the French Otto company. It worked so well that only a few insiders knew about this inconspicuous circumstance. The engine was built for petroleum and was used for the plant oil without any change. In this case also, the consumption experiments resulted in heat utilization identical to petroleum." A total of five diesel engines were shown at the Paris Exposition, according to a biography (Diesel 1937) of Diesel by his son, Eugen Diesel, with apparently one of them being operated on peanut oil.

The statements in Diesel’s book can be compared to a relatively frequently cited source on the initial use of vegetable oils which is a biography entitled Rudolf Diesel: Pioneer of the Age of Power (Nitske and Wilson, 1965). On p. 139 of this biography, the statement is made that as the nineteenth century ended, it was obvious that the fate and scope of the internal-combustion engine were dependent on its fuel or fuels. At the Paris exposition of 1900, a Diesel engine, built by the French Otto Company, ran wholly on peanut oil. Apparently none of the onlookers was aware of this. The engine, built especially for that type of fuel, operated exactly like those powered by other oils.

Unfortunately, the bibliography for the corresponding chapter in the biography by Nitske and Wilson (Nitske and Wilson, 1965) does not clarify where the authors obtained this information nor does it list references to the writings by Diesel discussed here. Thus, according to Nitske and Wilson, the peanut oil-powered diesel engine at the 1900 World’s Fair in Paris was built specifically to use that fuel, which is not consistent with the statements in Diesel’s book (Diesel, 1913a) and the literature cited below. Furthermore, the above texts from the biography (Diesel, 1937) and Diesel’s book (Diesel, 1913a) imply that it was not Diesel who conducted the demonstration and that he was not the source of the idea of using vegetable oils as fuel. According to Diesel, the idea for using peanut oil appears to have originated instead within the French government (see text below). However, Diesel conducted related tests in later years and appeared supportive of the concept.

A Chemical Abstracts search yields references to other papers by Diesel in which he reflected in greater detail on that event in 1900. Two references (Diesel, 1912; Diesel, 1913b) relate to a presentation Diesel made to the Institution of Mechanical Engineers (of Great Britain) in March 1912 (apparently in the last few years of his life, Diesel spent considerable time traveling to give presentations, according to the biography by Nitske and Wilson). Diesel states in these papers (Diesel, 1912; Diesel, 1913b) that at the Paris Exhibition in 1900 there was shown by the Otto Company a small Diesel engine, which, at the request of the French Government, ran on Arachide (earth-nut or pea-nut) oil, and worked so smoothly that only very few people were aware of it. The engine was constructed for using mineral oil, and was then worked on vegetable oil without any alterations being made. The French Government at the time thought of testing the applicability to power production of the Arachide, or earth-nut, which grows in considerable quantities in their African colonies, and which can be easily cultivated there, because in this way the colonies could be supplied with power and industry from their own resources, without being compelled to buy and import coal or liquid fuel. This question has not been further developed in France owing to changes in the Ministry, but the author resumed the trials a few months ago. It has been proved that Diesel engines can be worked on earth-nut oil without any difficulty, and the author is in a position to publish, on this occasion for the first time, reliable figures obtained by tests: Consumption of earth-nut oil, 240 grammes (0.53 lb.) per brake horsepower-hour; calorific power of the oil, 8600 calories (34,124 British thermal units) per kg, thus fully equal to tar oils; hydrogen 11.8 per cent. This oil is almost as effective as the natural mineral oils, and as it can also be used for lubricating oil, the whole work can be carried out with a single kind of oil produced directly on the spot. Thus this engine becomes a really independent engine for the tropics.

Diesel continued that (note the prescient concluding statement) similar successful experiments have also been made in St. Petersburg with castor oil; and animal oils, such as train-oil, have been used with excellent results. The fact that fat oils from vegetable sources can be used may seem insignificant today, but such oils may perhaps become in course of time of the same importance as some natural mineral oils and the tar products are now. Twelve years ago, the latter were not more developed than the fat oils are today, and yet how important they have since become. One cannot predict what part these oils will play in the Colonies in the future. In any case, they make it certain that motor-power can still be produced from the heat of the sun, which is always available for agricultural purposes, even when all our natural stores of solid and liquid fuels are exhausted.

The following discussion is based on numerous references mostly available by searching Chemical Abstracts or from a publication summarizing literature prior to 1949 on fuels from agricultural sources (Wiebe and Nowakowska, 1949). Since many of the older references are not readily available, the summaries in Chemical Abstracts were used as information source in these cases.

Background and Fuel Sources

The aforementioned background in the papers by Diesel (Diesel, 1912; Diesel, 1913b) on using vegetable oils to provide European tropical colonies, especially those in Africa, with a certain degree of energy self-sufficiency can be found in the related literature throughout the 1940s. Palm oil was often considered as a source of diesel fuel in the historic studies, although the diversity of oils and fats as sources of diesel fuel, an important aspect again today, and striving for energy independence were reflected in other historic investigations. Most major European countries with African colonies - Belgium, France, Italy and the UK with Portugal apparently making an exception - at the time, had varying interest in vegetable oil fuels; although several German papers, mainly from academic sources (Technische Hochschule Breslau), were also published. Reports from other countries also reflect a theme of energy independence. In Belgium a commission established by the government (van den Abeele, 1942; see discussion below) dealt with this issue and in France a syndicat national pour le développement de l’utilisation des huiles végetales combustibles apparently existed with the author of a study (Boiscorjon d’Ollivier, 1939) on this issue (using soybean oil) as secretary general.

Vegetable oils were also used as emergency fuels and for other purposes during World War II. For example, Brazil prohibited the export of cottonseed oil in order to substitute it for imported diesel fuel (Anonymous, 1943). Reduced imports of liquid fuel were also reported in Argentina, necessitating the commercial exploitation of vegetable oils (Martinez de Vedia, 1944). China produced diesel fuel, lubricating oils, gasoline, and kerosene; the latter two by a cracking process, from tung and other vegetable oils (Chang and Wan, 1947; Cheng, 1945). However, the exigencies of the war caused hasty installation of cracking plants based on fragmentary data (Cheng, 1945). Researchers in India, prompted by the events of World War II, extended their investigations on ten vegetable oils for development as a domestic fuel (Chowhury et al., 1942). Work on vegetable oils as diesel fuel ceased in India when petroleum-based diesel fuel again became plentifully at low cost (Amrute, 1947). The Japanese battleship, Yamato, reportedly used edible refined soybean oil as bunker fuel (ref. 1250 in Wiebe and Nowakowska, 1949).

Concerns about the rising use of petroleum fuels and the possibility of resultant fuel shortages in the United States in the years after World War II played a role in inspiring a dual fuel project at The Ohio State University (Columbus, Ohio), during which cottonseed oil (Huguenard, 1951) and corn oil (Lem, 1952), and blends thereof with conventional diesel fuel, were investigated. In a program at the Georgia School of Technology (now Georgia Institute of Technology), neat vegetable oils were investigated as diesel fuel (Baker and Sweigert, 1947). Once again, energy security perspectives have become a significant driving force for the use of vegetable oil-based diesel fuels, although environmental aspects (mainly reduction of exhaust emissions) play a role at least as important as energy security.

In modern times, biodiesel is derived, or has been reported to be producible from, many different sources, including vegetable oils, animal fats, used frying oils, and even soapstock. Generally, factors such as geography, climate, and economics determine which vegetable oil is of most interest for potential use in biodiesel fuels. Thus, in the United States, soybean oil is considered as a prime feedstock; in Europe, it is rapeseed (canola) oil; and in tropical countries, it is palm oil. As noted above, different feedstocks were investigated in the historic times. These included palm oil, soybean oil, cottonseed oil, castor oil, and somewhat less common oils, such as babassu (Pacheco Borges, 1945) and crude raisinseed oil (Manzella, 1936), as well as non-vegetable sources such as industrial tallow (Lugano and de Medina, 1945) and even fish oils (Kobayashi, 1921a; Kobayashi and Yamaguchi, 1921; Faragher et al., 1932, Lumet and Marcelet, 1927; Marcelet, 1927; Okamura, 1941). In numerous reports, especially from France and Belgium, dating from the early 1920′s, palm oil was probably the feedstock that received the most attention, although cottonseed and some other oils were tested (Mayné, 1920; Ford, 1921; Lazennec, 1921; Mathot, 1921a; Mathot, 1921b; Mathot, 1923;, Anonymous, 1921a; Anonymous, 1921b; Anonymous, 1922; Goffin, 1922; Leplae, 1922; Delahousse, 1923; Lumet, 1924). The availability of palm oil in tropical locations again formed the background as mentioned above. Eleven vegetable oils from India (groundnut, karanj, punnal, polang, castor, kapok, mahua, cottonseed, rapeseed, coconut, and sesame) were investigated as fuels (Chowhury et al., 1942). A Brazilian study reports on fourteen vegetable oils that were investigated as fuel (Pacheco Borges, 1945). Walton (Walton, 1938) summarized results on twenty vegetable oils (castor, grapeseed, maize, camelina, pumpkinseed, beechnut, rapeseed, lupin, pea, poppyseed, groundnut, hemp, linseed, chestnut, sunflower seed, palm, olive, soybean, cottonseed, and shea butter). He also pointed out (Walton, 1938) that "at the moment the source of supply of fuels is in a few hands, the operator has little or no control over prices or qualities, and it seems unfortunate that at this date, as with the petrol engine, the engine has to be designed to suit the fuel whereas, strictly speaking, the reverse should obtain—the fuel should be refined to meet the design of an ideal engine."

Although environmental aspects played virtually no role in promoting the use of vegetable oils as fuel in historic times and no emissions studies were conducted, it is still worthwhile to note some allusions to this subject from that time.

• "In case further development of vegetable oils as fuel proves practicable, it will simplify the fuel problems of many tropical localities remote from mineral fuel, and where the use of wood entails much extra labor and other difficulties connected with the various heating capacities of the wood’s use, to say nothing of the risk of indiscriminate deforestation" (Ford, 1921).

• "It might be advisable to mention, at this juncture, that, owing to the altered combustion characteristics, the exhaust with all these oils is invariably quite clean and the characteristic diesel knock is virtually eliminated" (Walton, 1938).

• Observations by other authors included: invisible or slightly smoky exhausts when running an engine on palm oil (Mathot, 1921a); clearer exhaust gases (Leplae, 1920); in the case of use of fish oils as diesel fuels, the exhaust was described as colorless and practically odorless (Lumet and Marcelet, 1927). However, in one case (Laporte, 1943), the odor from an engine operating on linseed or sunflower oil was described as characteristic, being disagreeable with linseed oil.

The visual observations of yesterday have been confirmed in modern times for biodiesel fuel. Numerous recent studies have shown that most exhaust emissions are reduced when using biodiesel fuel.

Technical Aspects

Many historic publications discuss the satisfactory performance of vegetable oils as fuels or fuel sources although it is often noted that their higher costs relative to petroleum-derived fuel would prevent widespread use.

The kinematic viscosity of vegetable oils is about an order of magnitude greater than that of conventional, petroleum-derived diesel fuel. High viscosity causes poor atomization of the fuel in the engine’s combustion chambers and ultimately results in operational problems, such as engine deposits. Since the renewal of interest during the late 1970s in vegetable oil-derived fuels, four possible solutions to the problem of high viscosity have been investigated: transesterification, pyrolysis, dilution with conventional petroleum-derived diesel fuel, and microemulsification (Schwab et al., 1987). Transesterification is the most common method and leads to monoalkyl esters of vegetable oils and fats, now called biodiesel when used for fuel purposes. As mentioned in the introductory summary, methanol is usually used for transesterification because in many countries it is the least expensive alcohol.

The high viscosity of vegetable oils as a major cause of poor fuel atomization resulting in operational problems such as engine deposits was recognized early (Mathot et al., 1921a; Schmidt, 1932; Schmidt, 1933; Schmidt and Gaupp, 1934; Gaupp, 1937; Boiscorjon d’Ollivier, 1939; Laporte, 1943). Although engine modifications such as higher injection pressure were considered (Schmidt, 1932; Tatti and Sirtori, 1937), reduction of the high viscosity of vegetable oils usually was achieved by heating the vegetable oil fuel (Mathot, 1921a; Schmidt, 1932; Schmidt, 1933; Schmidt and Gaupp, 1934; Gaupp, 1937; Seddon, 1942; Laporte, 1943). Often the engine was started on petrodiesel and, after a few minutes of operation, was then switched to the vegetable oil fuel, although a successful cold-start on high-acidity peanut oil was reported (Gautier, 1933). Advanced injection timing was a technique also employed (Gautier, 1935). Seddon (Seddon, 1942) gives an interesting practical account about a truck that operated successfully on different vegetable oils using preheated fuel. The preheating technique was also applied in a study on the feasibility of using vegetable oils in the transportation facilities needed for developing the tin mines of Nigeria (Seddon, 1942; Smith, 1942).

It was also recognized that performance of the vegetable oil-based fuels generally was satisfactory but that power output was slightly lower than with petroleum-based diesel fuel and that fuel consumption was slightly higher (Baker and Sweigert, 1947; Lumet and Marcelet, 1927; Okamura, 1941; Lazennec, 1921; Anonymous, 1921a; Mathot, 1921b; Anonymous, 1922; Walton, 1938; Schmidt, 1932; Schmidt and Gaupp, 1934; Gaupp, 1937; Smith, 1942; Gauthier, 1931; Hamabe and Nagao, 1939), although engine load-dependent or opposite effects were reported (Martinez de Vedia, 1944; Huguenard, 1951; Lem, 1952; Manzella, 1935). Ignition lag was reportedly reduced with engines using soybean oil (Hamabe and Nagao, 1939). In many of these publications it was noted that the diesel engines used operated more smoothly on vegetable oils than on petroleum-based diesel fuel. Due to their combustion characteristics, vegetable oils with high oxygen content were suggested to make the use of gas turbines as prime movers practicable (Gonzaga, 1932).

Fuel quality issues were also addressed. It was suggested that when the acid content of the vegetable oil fuels is maintained at a minimum no adverse results are experienced either on the injection equipment or on the engine (Smith, 1942; Seddon, 1942). Relatedly, other authors discussed that the effect of free fatty acids, moisture, and other contaminants on fuel properties is an important issue (Chowhury et al., 1942). The effect of different kinds of vegetable oils on corrosion of neat metals and lube oil dilution and contamination, etc. were studied (Gaupp, 1937).

Pyrolysis, cracking, or other methods of decomposition of vegetable oils to yield fuels of varying nature is an approach that accounts for a significant amount of the literature in historic times. Artificial gasoline, kerosene, and diesel were obtained in China from tung oil (Chang and Wan, 1947) and other oils (Cheng, 1945). Other oils used in such an approach included fish oils (Kobayashi, 1921a; Kobayashi and Yamaguchi, 1921; Faragher et al., 1932), as well as linseed oil (Mailhe, 1921), castor oil (Melis, 1924), palm oil (Morrell et al., 1932), cottonseed oil (Egloff and Morrell, 1932), and olive oil (Gomez Aranda, 1943). Numerous reports from several countries including China, France, and Japan are concerned with obtaining fuels by cracking of vegetable oils or related processes (Kobayashi, 1921b; Mailhe, 1922; Sato, 1922; Sato, 1923; Waterman and Perquin, 1923; Sato and Tseng, 1926; Sato, 1927a; Sato, 1927b; Sato, 1927c; Sato and Ito, 1927; de Sermoise, 1934; Koo and Cheng, 1935a; Koo and Cheng, 1935b; Koo and Cheng, 1936; Ping, 1935a; Ping, 1935b; Ping, 1936; Ping, 1938; Tu and Wang, 1936; Tu and Pan, 1936; Chao, 1937; Banzon, 1937; Michot-Dupont, 1937; Cerchez, 1938; Friedwald, 1937; Dalal and Mehta, 1939; Chang et al., 1941; Suen and Wang, 1941; Sun, 1941; Lo, 1940; Lo and Tsai, 1942a; Lo and Tsai, 1942b; Bonnefoi, 1943; François, 1947; Otto, 1945). The other approaches - dilution with petrodiesel and, especially, microemulsification - appear to have received little or no attention during the historic times. However, some experiments on blending of conventional diesel fuel with cottonseed oil (Huguenard, 1951; Tu and Ku, 1936), corn oil (Lem, 1952), and turnip, sunflower, linseed, peanut, and cottonseed oil (Martinez de Vedia, 1944) were described. Blends of aqueous ethanol with vegetable gasoline were reported (Suen and Li, 1941). Ethanol was also used for improving the atomization and combustion of highly viscous castor oil (Ilieff, 1939).

Besides powering vehicles, the use of vegetable oils for other, related purposes found some attention. The possibility for deriving fuels as well as lubricating oils and greases from vegetable oils in the French African colonies was discussed (Jalbert, 1942). The application of vegetable oils as fuels for heating and power purposes was discussed (Charles, 1923). At least one critique of the use of vegetable oils, particularly olive oil, for fuel and lubricant use was published (Fachini, 1933).

Besides technical literature in journals and reports, several patents from the historic times dealt with vegetable oils or their derivatives as fuels, obtained mainly through cracking or pyrolysis (Physical Chemical Research Co., 1933; Physical Chemical Research Co., 1934; Legé, 1937; Jean, 1938; Standard Oil Development Co., 1939; Bouffort, 1939; Archer, 1941).

The First Biodiesel

Walton (Walton, 1938) recommended that "to get the utmost value from vegetable oils as fuel it is academically necessary to split off the triglycerides and to run on the residual fatty acid. Practical experiments have not yet been carried out with this; the problems are likely to be much more difficult when using free fatty acids than when using the oils straight from the crushing mill. It is obvious that the glycerides have no fuel value and in addition are likely, if anything, to cause an excess of carbon in comparison with gas oil."

Walton’s statement points in the direction of what is now termed biodiesel by recommending the elimination of glycerol from the fuel, although without mentioning esters. In this connection, some remarkable work performed in Belgium and its former colony the Belgian Congo (known after its independence for a long time as Zaire) deserves more recognition than it has received. On April 1, 1935, a Commission on Fuels (Commission des Carburants) was established in the Belgian Department of Colonies to systematically study the production and use of fuels obtained from local products (van den Abeele, 1942). It appears that Belgian patent 422,877, granted on Aug. 31, 1937, to C. G. Chavanne (University of Brussels) (Chavanne, 1937), then constitutes the first report on what is today known as biodiesel. It describes the use of ethyl esters of palm oil (although other oils and methyl esters are mentioned) as diesel fuel. These esters were obtained by acid-catalyzed transesterification of the oil (base catalysis is now more common). This work has been described in more detail (Chavanne, 1943).

Of particular interest is a related extensive report published in 1942 on the production and use of palm oil ethyl ester as fuel (van den Abeele, 1942; note that this author, who was the director of agriculture in the Belgian Ministry of Colonies, wrote the introduction to this report while no author is given for the extensive technical part; it appears likely that Chavanne and maybe other members of the Commission on Fuels authored the technical section). That work described what was probably the first test of an urban bus operating on biodiesel. A bus fueled with palm oil ethyl ester served the commercial passenger line between Brussels and Louvain (Leuven) in the summer of 1938. Performance of the bus operating on that fuel reportedly was satisfactory. It was noted that the viscosity difference between the esters and conventional diesel fuel was considerably less than that between the parent oil and conventional diesel fuel. Also, the article pointed out that the esters are miscible with other fuels. That work also discussed what is probably the first cetane number (CN) testing of a biodiesel fuel. On p. 52 of that report, CN of palm oil ethyl ester was reported as approximately 83 (relative to a high-quality standard with CN 70.5 and a low-quality standard of CN 18 and diesel fuels with CN of 50 and 57.5). Thus, those results agree with modern work reporting relatively high CN for such biodiesel fuels. A later paper by another author reported the auto-ignition temperature of various alkyl esters of palm oil fatty acids (Duport, 1946).

Biodiesel Since the 1970s

As a result of the energy crises of the 1970′s, vegetable oils were remembered as alternatives to petrodiesel fuel, with work commencing in countries such as Austria, Germany, South Africa, and the United States. Some early research in the 1970′s to 1980 includes work at The Ohio State University on the use of untransesterified waste vegetable oil as diesel fuel supplement (Silvis, 1977; Fishinger, 1980; Fishinger et al., 1981) and use of rapeseed oil as fuel at the German Federal Agricultural Research Institute (Batel et al., 1980). An early overview of such activities was given by Quick (1980). The use of methyl esters of sunflower oil to reduce the viscosity of vegetable oil was reported at several technical conferences in 1980 by South African researchers (Bruwer et al., 1980a, 1980b, 1981) and marks the beginning of the rediscovery and eventual commercialization of vegetable oil esters as biodiesel fuel. Research activities, ongoing since the late 1970′s, have expanded in recent years in conjunction with the increasing interest in alternative fuels. Biodiesel standards were established around the world, including the Austrian standard Ö-Norm C1190 (1991) and the German standard DIN 51606, which were eventually superseded by the establishment of the European standard EN 14214 (2003), as well as the standard ASTM D6751 (2002) in the United States. In the United States, the standard ASTM D7467 for blends of biodiesel with petrodiesel in the range of 6-20% biodiesel in petrodiesel was established in 2008. Trade organizations such as the National Biodiesel Board in the United States (founded originally as the National SoyDiesel Development Board in 1992) and the European Biodiesel Board (established in 1997) promote the development and use of biodiesel. Countless activities in the legislative and regulatory sectors in numerous countries around the world have accompanied the development and production of biodiesel. For example, in the United States, legislation enacted in the 1990′s such as the Clean Air Act Amendments (1990) and the Energy Policy Act (1992) mandated the use of alternative or clean fuels in regulated truck and bus fleets. Amendments to the Energy Policy Act (1998), which provided credits for biodiesel use (also in blends with conventional diesel fuel). More recently the JOBS Creation Act of 2004 (providing an excise tax credit for biodiesel) and the Energy Security and Independence Act of 2007 (amending the Renewable Fuels Standard of 2005) as well as various state mandates are legislative and regulatory driving forces in the United States. In the European Union, EU directives 2003/30/EC and 2003/96/EC are concerned with levels of use and taxation of biofuels. Gremany, as the largest producer and consumer of biodiesel, passed an Energy Tax Act (Energiesteuergesetz), which subjects biodiesel to this kind of excise tax, and a Biofuels Quota Act (Biokraftstoffquotengesetz) to comply with EU directives. The production and use of biodiesel has increased exponentially with the search for additional feedstocks gaining increasing significance.

A final thought should be given to the term biodiesel itself. Although this term was probably coined prior to 1988, a Chemical Abstracts search (using the SciFinder search engine with biodiesel as the key word) yielded first use of the term biodiesel in the technical literature in a Chinese paper published in 1988 (Wang, 1988). The next paper using this term appeared in 1991 (Bailer and de Hueber, 1991) and from then on the use of the word biodiesel in the literature has expanded exponentially.

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van den Abeele, M. L’Huile de palme: matière première pour la préparation d’un carburant lourd utilisable dans