Production and Evaluation of Biodiesel from Field Pennycress

(Thlaspi arWense L.) Oil†

Bryan R. Moser,* Gerhard Knothe, Steven F. Vaughn, and Terry A. Isbell

National Center for Agricultural Utilization Research, Agricultural Research SerVice,

United States Department of Agriculture, 1815 North UniVersity Street, Peoria, Illinois 61604

ReceiVed April 15, 2009. ReVised Manuscript ReceiVed June 1, 2009

Field pennycress (Thlaspi arVense L.) oil is evaluated for the first time as a feedstock for biodiesel production.

Biodiesel was obtained in 82 wt % yield by a standard transesterification procedure with methanol and sodium

methoxide catalyst at 60 °C and an alcohol to oil molar ratio of 6:1. Acid-catalyzed pretreatment to reduce the

acid value of crude field pennycress oil resulted in a yield after methanolysis of 94 wt %. Field pennycress oil

had high contents of erucic (13(Z)-docosenoic; 32.8 wt %) and linoleic (9(Z),12(Z)-octadecadienoic; 22.4 wt

%) acids with other unsaturated fatty acids comprising most of the remaining fatty acid profile. As a result, the

methyl esters (biodiesel) obtained from this oil exhibited a high cetane number of 59.8 and excellent low

temperature properties, as evidenced by cloud, pour, and cold filter plugging points of -10, -18, and -17 °C,

respectively. The kinematic viscosity and oxidative stability (Rancimat method) of field pennycress oil methyl

esters were 5.24 mm2

/s (40 °C) and 4.4 h (110 °C), respectively. Other fuel properties such as acid value,

lubricity, free and total glycerol content, surface tension, as well as sulfur and phosphorus contents were also

determined and are discussed in light of biodiesel standards such as ASTM D6751 and EN 14214. Also reported

for the first time are cetane numbers of methyl esters of erucic and gondoic (methyl 11(Z)-eicosenoate) acids,

which were found to be 74.2 and 73.2, respectively. In summary, field pennycress oil appears to an acceptable

feedstock for biodiesel production.

1. Introduction

Biodiesel, defined as an alternative fuel composed of monoalkyl

esters of long-chain fatty acids prepared from vegetable oils or

animal fats by the American Society for Testing and Materials

(ASTM),1 has attracted considerable interest as a substitute or

blend component for conventional petroleum diesel fuel (petrodiesel). Technical advantages of biodiesel include derivation

from renewable and domestic feedstocks, displacement of

imported petroleum, inherent lubricity, essentially no sulfur

content, superior flash point and biodegradability, reduced

toxicity, and a reduction in most regulated exhaust emissions.

Important disadvantages versus petrodiesel are inferior oxidative

and storage stability, lower volumetric energy content, inferior

low temperature operability, and in most cases higher NOx

exhaust emissions.2-5 Biodiesel must be satisfactory according

to accepted fuel standards such as ASTM D67511 in the United

States or the Committee for Standardization (CEN) standard

EN 142146 in Europe before combustion in compression-ignition

(diesel) engines.

The high cost of commodity vegetable oils represents a

significant challenge to the biodiesel industry.7,8 Presently,

feedstock acquisition accounts for 80% or more of the costs

associated with biodiesel production.7,8 Feedstock availability

varies with geography and climate, as the most abundant lipids

in a particular region are the most common biodiesel feedstocks.

Thus, rapeseed oil is principally used in Europe, palm oil

predominates in tropical countries, and soybean oil and animal

fats are primarily used in the United States.2,3,9 However, many

commodity vegetable oils are prohibitively expensive and have

competing food-related applications. In addition, if all currently

available commodity vegetable oils were consumed solely for

biodiesel production, the amount of fuel produced would still

not suffice to completely displace petrodiesel at current usage

levels. Consequently, the development of alternative feedstocks

that meet all or most of the following criteria has attracted

considerable research attention: low cost, high oil content, low

agricultural inputs, favorable fatty acid (FA) composition,

compatibility with existing farm equipment and infrastructure,

production in off-season from conventional commodity crops

or in agriculturally undesirable lands, definable growth seasons,

† Disclaimer: Product names are necessary to report factually on available

data; however, the USDA neither guarantees nor warrants the standard of

the product, and the use of the name by USDA implies no approval of the

product to the exclusion of others that may also be suitable.

* To whom correspondence should be addressed. Telephone: (309) 681-

6511. Fax: (309) 681-6340. E-mail: bryan.moser@ars.usda.gov.

(1) American Society for Testing and Materials. Standard specification

for biodiesel fuel blend stock (B100) for middle distillate fuels, ASTM

D6751-08. In ASTM Annual Book of Standards; American Society for

Testing and Materials: West Conshohocken, PA, 2008.

(2) Mittelbach, M.; Remschmidt, C. BiodieselsThe ComprehensiVe

Handbook; M. Mittelbach: Graz, Austria, 2004.

(3) Knothe, G.; Krahl, J.; Van Gerpen, J. The Biodiesel Handbook;

AOCS Press: Champaign, IL, 2005.

(4) McCormick, R. L.; Williams, A.; Ireland, J.; Brimhall, M.; Hayes,

R. R. Fiscal year 2006 annual operating plan milestone 10.4; NREL

Milestone Report 540-40554, 2006; http://www.nrel.gov/docs/fy07osti/

40554.pdf.

(5) Moser, B. R. In Vitro Cell. DeV. Biol.-Plant 2009, 45, 229-266.

(6) European Committee for Standardization (CEN). AutomotiVe fuelsFatty acid methyl esters (FAME) for diesel engines-Requirement methods,

EN 14214:2003; European Committee for Standardization (CEN): Brussels,

Belgium, 2003.

(7) Paulson, N. D.; Ginder, R. G. Working Paper 07-WP 448, Center

for Agricultural and Rural DeVelopment; Iowa State University: Ames, IA,

May 2007.

(8) Retka-Schill, S. Biodiesel Mag. 2008, 5, 64–70. (9) Demirbas, A. Energy ConVers, Manage. 2006, 47, 2271–2282.

Energy & Fuels 2009, 23, 4149–4155 4149

10.1021/ef900337g This article not subject to U.S. Copyright. Published 2009 by the American Chemical Society

Published on Web 07/02/2009

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uniform rates of seed maturation, and viable markets for

coproducts such as seed meal. Selected recent examples of

alternative feedstocks reported in the scientific literature include

desert date (Balanites aegyptica L.),10 moringa (Moringa oleifera

L.),11 karanja (Pongamia pinnata L.),12 and pumpkin (Cucurbita

pepo L.)13 seed oils, among numerous others.5

Field pennycress (Thlaspi arVense L.), also known as stinkweed or French-weed, is a winter annual belonging to the

Brassicaceae family. Native to Eurasia but with an extensive

distribution throughout temperate North America, field pennycress is highly adapted to a wide variety of climatic conditions.14

The Brassicaceae family is a prolific source of biodiesel

feedstocks, as evidenced by canola (or rapeseed, Brassica napus

L.) and recent reports on B. alba L.,15 B. carinata L.,16 Camelina

satiVa L.,17 and Raphanus satiVus L.18 oils, among others.

Generally considered to be an agricultural pest (weed), field

pennycress has potential to serve in a summer/winter rotational

cycle with conventional commodity crops (such as corn or

soybean), thus not displacing existing agricultural production.

Field pennycress is tolerant of fallow lands, requires minimal

agricultural inputs (fertilizer, pesticides, water), is not part of

the food chain, is compatible with existing farm infrastructure,

and has high oil content (20-36 wt %).13,19-21 In addition, each

plant may produce up to 15 000 seeds, and fields heavily infested

with field pennycress are reported to yield up to 1345 kg of

seed/ha.22 More recent results indicate that the yield from wild

populations is in the range of 1120-2240 kg of seed/ha, which

equates to around 600-1200 L of oil/ha versus 450 and

420-640 L/ha in the cases of soybean (SBO)21 and camelina

(C. satiVa L.)23 oils, respectively. Defatted field pennycress seed

meal cannot be used as an animal feed as a result of its high

glucosinolate content, but other applications such as biofumigation have been reported.14

The objective of the present study was to prepare field

pennycress oil methyl esters (FPME) and evaluate their properties, such as low temperature operability, cetane number,

oxidative stability, kinematic viscosity, lubricity, and surface

tension. Compositional characteristics such as fatty acid (FA)

profile, free and total glycerol content, acid value, and tocopherol, phytosterol, sulfur, and phosphorus contents were of

additional interest, along with a comparison with biodiesel fuel

standards such as ASTM D6751 and EN 14214. Furthermore,

as a member of the Brassicaceae family, field pennycress is

expected to possess a high level of unsaturated FA with a

significant amount contributed by erucic (13(Z)-docosenoic) acid

and therefore may serve as a model biodiesel feedstock for oils

with similar FA profiles.

2. Experimental Section

2.1. Materials. Field pennycress seeds were collected from a

wild population in Peoria County, IL. Methyl erucate (>99%; methyl

13(Z)-docosenoate), methyl gondoate (>99%; methyl 11(Z)-eicosenoate), and fatty acid methyl ester standards were purchased from

Nu-Chek Prep, Inc. (Elysian, MN). Tocopherol standards (g97%

purity), as well as stigmasterol and 5R-cholestane, were obtained

from Matreya, LLC (Pleasant Gap, PA). Campesterol and brassicasterol were purchased from Steraloids (Newport, RI). N,OBis(trimethylsilyl)fluoroacetamide with 1% trimethylchlorosilane

(BSTFA + 1% TMCS) was purchased from Regis, Inc. (Morton

Grove, IL). Each phytosterol standard was g97% purity. All other

chemicals and reagents were obtained from Sigma-Aldrich Corp.

(St. Louis, MO) and used as received.

2.2. Extraction of Field Pennycress Oil. Field pennycress seeds

were cold pressed using a heavy-duty laboratory screw press (Model

L250, French Oil Mill Machinery Co., Piqua, OH). The details of

this expeller are available elsewhere.24 Once extracted, the crude

oil was filtered to remove solid material. Quantification of oil

content by hexane extraction of field pennycress seeds is described

elsewhere.19

2.3. Pretreatment of Field Pennycress Oil. Acid-catalyzed

pretreatment of field pennycress oil (FPO) with an initial acid value

(AV) of 0.61 mg of KOH/g was accomplished in a 500 mL threenecked round-bottom flask connected to a reflux condenser and a

mechanical magnetic stirrer set to 1200 rpm. Initially, FPO (200

g, 220 mL, 0.207 mol) and methanol (78 mL, 1.91 mol, 35 vol %)

were added to the flask, followed by dropwise addition of sulfuric

acid (conccentrated, 2.20 mL, 0.04 mol, 1.0 vol %). The contents

were heated at reflux for 2 h. Upon cooling to room temperature

(RT), the alcoholic phase was removed utilizing a separatory funnel.

The oil phase was washed with distilled water (3 × 20 mL), which

was followed by rotary evaporation under reduced pressure (20

mbar; 30 °C) to remove residual methanol. Finally, treatment with

magnesium sulfate (MgSO4) afforded dried FPO (185.2 g, 93 wt

%) with a final AV of 0.09 mg of KOH/g.

2.4. Methanolysis of Field Pennycress Oil. Transesterification

of FPO was performed on both crude and acid-pretreated oils.

Methanolysis was carried out in a 500 mL three-necked roundbottom flask connected to a reflux condenser and a mechanical

magnetic stirrer set to 1200 rpm. Initially, FPO (180 g, 200 mL,

0.187 mol) and methanol (46 mL, 1.12 mol; 6:1 mol ratio) were

added to the flask and heated to 60 °C (internal reaction temperature

monitored by digital temperature probe), followed by addition of

0.50 wt % sodium methoxide (25 wt % in methanol). After 1.5 h,

the reaction mixture was equilibrated to RT and transferred to a

separatory funnel. The lower glycerol phase was removed by gravity

separation (>2 h settling time) followed by removal of residual

methanol by rotary evaporation under reduced pressure (20 mbar;

30 °C). The crude methyl esters were washed until a neutral pH

was obtained with distilled water (4 × 20 mL) and dried with

MgSO4 to provide FPME. The yields of FPME were 82 and 94 wt

% from crude and acid-pretreated FPO, respectively. 1H NMR (500

MHz, CDCl3): δ 5.35 (m, 2H, vinyl), 3.67 (s, 3H, -OCH3), 2.79

(m, 2H, bis-allylic), 2.31 (t, 2H, allylic), 2.03 (m, 2H, R to ester),

1.62 (m, 2H, to ester), 1.28 (m, 28H, methylene), 0.90 (t, 3H,

methyl). 13C NMR (125 MHz, CDCl3): δ 174.30, 174.27, 131.95,

130.26, 130.20, 130.05, 130.00, 129.92, 129.90, 129.87, 129.83,

129.74, 128.27, 128.24, 128.04, 127.90, 127.73, 127.12, 51.40,

34.11, 34.10, 31.90, 31.52, 29.77-29.09 (multiplet of 15 peaks),

27.20, 27.16, 25.63, 25.52, 24.96, 22.67, 22.57, 20.54, 14.25, 14.09,

14.05. FT-IR (neat): 3008, 2923, 2853, 1742, 1462, 1435, 1362,

1245, 1195, 1169, 1117, 1100, 1015, 880, 843, 722 cm-1

.

(10) Chapagain, B. P.; Yehoshua, Y.; Wiesman, Z. Bioresour. Technol.

2009, 100, 1221–1226. (11) Rashid, U.; Anwar, F.; Moser, B. R.; Knothe, G. Bioresour. Technol.

2008, 99, 8175–8179. (12) Naik, M.; Meher, L. C.; Naik, S. N.; Das, L. M. Biomass Bioenerg.

2008, 32, 354–357. (13) Schinas, P.; Karavalakis, G.; Davaris, C.; Anastopoulos, G.; Karonis,

D.; Zannikos, F.; Stournas, S.; Lois, E. Biomass Bioenerg. 2009, 33, 44–

49.

(14) Vaughn, S. F.; Isbell, T. A.; Weisleder, D.; Berhow, M. A. J. Chem.

Ecol. 2005, 31, 167–177. (15) Ahmad, M. Asian J. Chem. 2008, 20, 6402–6403. (16) Bouaid, A.; Martinez, M.; Aracil, J. Bioresour. Technol. 2009, 100,

2234–2239. (17) Frohlich, A.; Rice, B. Ind. Crops Prod. 2005, 21, 25–31. (18) Domingos, A. K.; Saad, E. B.; Wilhelm, H. M.; Ramos, L. P.

Bioresour. Technol. 2008, 99, 1837–1845. (19) Moser, B. R.; Shah, S. N.; Winkler-Moser, J. K.; Vaughn, S. F.;

Evangelista, R. L. Ind. Crops Prod. DOI: 10.1016/j.indcrop.2009.03.007.

(20) Dolya, V. S.; Koreshchuk, K. E.; Shkurupii, E. N.; Kaminskii, N. A.

Chem. Nat. Compd. 1976, 10, 447–449. (21) Marek, L. F.; Bingaman, B.; Gardner, C. A. C.; Isbell, T. 20th

Annual Meeting of the Association for the AdVancement of Industrial Crops

Book of Abstracts, American Association for the Advancement of Industrial

Crops: Maricopa, Arizona, 2008; p 49.

(22) Best, K. F.; McIntyre, G. I. Can. J. Plant Sci. 1975, 55, 279–292. (23) Sawyer, K. Biodiesel Mag. 2008, 5 (7), 82–87. (24) Evangelista, R. L. Ind. Crops Prod. 2009, 29, 189–196.

4150 Energy & Fuels, Vol. 23, 2009 Moser et al.

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2.5. Fatty Acid Profile by Gas Chromatography (GC). Fatty

acid methyl esters (FAME) were separated (triplicates, means

reported) using a Varian (Walnut Creek, CA) 8400 GC equipped

with an FID detector and a SP2380 (Supelco, Bellefonte, PA)

column (30 m × 0.25 mm i.d., 0.20 μm film thickness). The

carrier gas was He at 1 mL/min. The oven temperature was

initially held at 150 °C for 15 min, increased to 210 at 2 °C/

min, increased to 220 at 50 °C/min, and then held for 10 min.

The injector and detector temperatures were 240 and 270 °C,

respectively. FAME peaks were identified by comparison to the

retention times of reference standards. The FA profile of FPME

is reported in Table 1.

2.6. Free and Total Glycerol Determination by GC. Free and

total glycerol determinations (Table 2) were made according to

ASTM standard D658425 employing an Agilent (Santa Clara, CA)

Model 7890A GC-FID equipped with a Model 7683B series injector

and an Agilent D8-5HT (15 m × 0.32 mm i.d., 0.10 μm film

thickness) column.

2.7. NMR and Fourier Transform Infrared (FT-IR) Spectroscopy. 1

H and 13C NMR data were recorded using a Bruker AV500 spectrometer (Billerica, MA) operating at 500 MHz (125 MHz

in the case of 13C NMR) using a 5-mm broadband inverse Z-gradient

probe in CDCl3 (Cambridge Isotope Laboratories, Andover, MA)

as solvent. FT-IR spectra were obtained on a Thermo-Nicolet Nexus

470 FTIR spectrometer (Madison, WI) with a Smart ARK accessory

containing a 45 ZeSe trough in a scanning range of 650-4000 cm-1

for 64 scans at a spectral resolution of 4 cm-1. The 1H NMR

spectrum of FPME is depicted in Figure 1.

2.8. Tocopherol Content by HPLC. Tocopherols were quantified (triplicate determinations, means reported) according to AOCS

official method Ce 8-8926 using a hexane/2-propanol mobile phase

on an Inertsil (Varian) silica column (5 μm, 150 Å, 250 mm × 4.6

mm i.d.), Varian HPLC Pro-Star Model 230 pump, Model 410 auto

sampler, and Model 363 fluorescence detector using excitation and

emission wavelengths of 290 and 330 nm, respectively. Peaks were

identified by comparison to the retention times of reference

standards.

2.9. Phytosterol Content by GC. Samples were saponified and

phytosterols were extracted as previously described.27 After saponification, phytosterols were manually injected onto a Varian

3400 GC equipped with an FID and a Supelco SPB-1701 (30 m ×

0.25 mm × 0.25 μm) capillary column. Helium was used as the

carrier gas with a 1:50 injector split. The injector and detector

temperatures were 270 and 290 °C, respectively. The column oven

initial temperature was 250 °C for 0.5 min, increased at 10 °C/min

to 270 °C and held for 27 min, and then increased at 10 °C/min to

280 °C and held for 3.5 min. Phytosterols were identified by

comparison to the retention times (relative to the internal standard)

of reference standards. Phytosterols without commercially available

standards, such as δ5-avenasterol, were identified by their relative

retention times compared to the literature,27 and by comparison with

samples known to contain those phytosterols. Quantification

(triplicates, means reported) was carried out by the internal standard

method developed with available standards. For phytosterols with

no available commercial standard, the response factor for -sitosterol was used for quantification.

2.10. Fuel Properties of Methyl Esters. Cloud (CP, °C) and

pour point (PP, °C) determinations were made following ASTM

standards D577328 and D5949,29 respectively, using a Model PSA70S Phase Technology Analyzer (Richmond, BC, Canada). Cloud

and pour points were rounded to the nearest whole degree (°C).

For a greater degree of accuracy, PP measurements were done with

a resolution of 1 °C instead of the specified 3 °C increment. Cold

filter plugging point (CFPP, °C) was measured in accordance with

(25) American Society for Testing and Materials. Standard test method

for determination of free and total glycerin in B-100 biodiesel methyl esters

by gas chromatography, ASTM D6584-08. In ASTM Annual Book of

Standards; American Society for Testing and Materials: West Conshohocken, PA, 2008.

(26) American Oil Chemists’ Society. Official Methods and Recommended Practices of the American Oil Chemists’ Society (Method AOCS

Ce 8-89), 5th ed.; Firestone, D., Ed.; American Oil Chemists’ Society:

Champaign, IL, 1999.

(27) Dutta, P. C.; Norme ́n, L. J. Chromatogr., A 1998, 816, 177–184. (28) American Society for Testing and Materials. Standard test method

for cloud point of petroleum products (constant cooling rate method), ASTM

D5773-07. In ASTM Annual Book of Standards; American Society for

Testing and Materials: West Conshohocken, PA, 2007.

(29) American Society for Testing and Materials. Standard test method

for pour point of petroleum products (automatic pressure pulsing method),

ASTM D5949-01. In ASTM Annual Book of Standards; American Society

for Testing and Materials: West Conshohocken, PA, 2001.

Table 1. Fatty Acid Composition (wt %) of Field Pennycress

Oil (FPO)

fatty acida FPO

C14:0 0.1

C16:0 3.1

C16:1 9c 0.2

C18:0 0.5

C18:1 9c 11.1

C18:1 11c 1.5

C18:2 9c, 12c 22.4

C18:3 9c, 12c, 15c 11.8

C20:0 0.3

C20:1 11c 8.6

C20:2 11c, 14c 1.6

C22:0 0.6

C22:1 13c 32.8

C22:2 13c, 16c 0.7

C22:3 13c, 16c, 19c 0.3

C24:1 15c 2.9

unknown (sum) 1.5

∑saturatedb 4.6

∑monounsaturatedc 55.6

∑polyunsaturatedd 38.3

∑C20+e 47.8

a For example, C18:1 9c signifies an 18 carbon fatty acid chain with

one cis (c) double bond located at carbon 9 (methyl 9Z-octadecenoate;

methyl oleate). b ∑saturated ) C14:0 + C16:0 + C18:0 + C20:0 +

C22:0. c ∑monounsaturated ) C16:1 + C18:1 + C20:1 + C22:1 +

C24:1. d ∑polyunsaturated ) C18:2 + C18:3 + C20:2 + C22:2 +

C22:3. e ∑C20+ ) C20:0 + C20:1 + C20:2 + C22:0 + C22:1 +

C22:2 + C22:3 + C24:1.

Table 2. Properties of Field Pennycress Methyl Esters (FPME)

with Comparison to Standards

ASTM D6751 EN 14214 FPME

acid value, mg of KOH/g 0.50 max 0.50 max 0.04 (0.03)/

0.02 (0.02)a,b

free glycerol, mass % 0.020 max 0.020 max 0.005

total glycerol, mass % 0.240 max 0.250 max 0.041

cloud point, °C report - -10 (1)

pour point, °C - --18 (1)

cold filter plugging point, °C - c -17 (1)

oxidative stability (110 °C), h 3 min 6 min 4.4 (0.1)

kinematic viscosity, mm2/s

-10 °C - - 35.52

0 °C - - 16.70

20 °C - - 8.65

40 °C 1.9-6.0 3.5-5.0 5.24 (0.01)

lubricity (HFRR, 60 °C), μm d d 125 (3)

sulfur, ppm 15 max 10 max 7

phosphorus, mass % 0.001 max 0.001 max 0.0000

surface tension, mN/m

24 °C - - 31.0 (0.1)

40 °C - - 29.6 (0.1)

cetane number 47 min 51 min 59.8e

a Values in parentheses are standard deviations from the reported

means (n ) 3; n ) 2 for lubricity; n ) 5 for surface tension). b Values

represent AV of FPME prepared from crude (0.04) and pretreated (0.02)

FPO. All subsequent data are for FPME prepared from crude FPO.

c Variable by location and time of year. d Maximum wear scar values of

460 and 520 μm are specified in petrodiesel standards EN 590 and

ASTM D975. e Derived cetane number.

EValuation of Biodiesel from Field Pennycress Oil Energy & Fuels, Vol. 23, 2009 4151

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ASTM standard D637130 utilizing a Model FPP 5Gs ISL Automatic

CFPP Analyzer provided by PAC, L.P. (Houston, TX). All

experiments were run in triplicate, and mean values are reported

(Tables 2 and 3).

Kinematic viscosity (υ, mm2

/s) was measured with a CannonFenske viscometer (Cannon Instrument Co., State College, PA)

following ASTM standard D445 (Tables 2 and 3).31

Lubricity (duplicates, means reported; Tables 2 and 3) was

measured at 60 °C ((1 °C) according to ASTM standard D607932

using a high-frequency reciprocating rig (HFRR) lubricity tester

(PCS Instruments, London, England) via Lazar Scientific (Granger,

IN). Reported wear scars (μm) were the result of measuring the

maximum lengths of the x- and y-axes of each wear scar using a

Prior Scientific (Rockland, MA) Epimat Model M4000 microscope,

followed by calculating the average of these maximum values.

Oxidative stability (induction period, IP, h) was determined

(triplicates, means reported; Tables 2 and 3) at 110 °C with a

correction factor of 1.5 °C utilizing a Metrohm USA, Inc.

(Riverview, FL) Model 743 Rancimat instrument according to the

standard EN 14112.33

Acid value (AV, mg of KOH/g) was measured (triplicates, means

reported; Tables 2 and 3) as described in AOCS official method

Cd 3d-6334 using a Metrohm 836 Titrando (Westbury, NY)

autotitrator equipped with a Model 801 stirrer and a Solvotrode

electrode. The official method was modified for scale to use 2 g of

sample and 0.02 M KOH. The titration end point was automatically

determined and visually verified using a phenolphthalein indicator.

Surface tension (γ, mN/m) was determined (five times; means

reported; Table 2) at 24 ( 1 and 40 ( 1 °C with a Sita t60 bubble

pressure tensiometer (Dresden, Germany). Dilutions and temperature

control were handled by a Cat Ingenieurbu ̈ ro M. Zipperer GmbH

(Staufen, Germany) M26 stir plate and a Model μ10MC buret. A

bubble lifetime of at least 4 s was used so that dynamic effects

were not a factor in the measurements. The instrument was

calibrated using pure water. Additionally, the surface tensions of

several organic solutions were measured and found to agree with

literature values.

Cetane numbers (CN) were determined as derived cetane

numbers (DCN) (Table 2) by Southwest Research Institute (San

Antonio, TX) utilizing an Ignition Quality Tester (IQT) following

ASTM standard D6890.35 Results generated by ASTM D6890

generally correlate with CN determination by ATSM D613. Sulfur

(S, ppm) and phosphorus (P, mass %) were measured (Tables 2

and 3) by Magellan Midstream Partners, L.P. (Kansas City, KS)

according to ASTM standards D545336 and D4951,37 respectively.

Gardner color (Table 3) was measured on a Lovibond 3-Field

Comparator from Tintometer, Ltd. (Salisbury, England) using

(30) American Society for Testing and Materials. Standard test method

for cold filter plugging point of diesel and heating fuels, ASTM D6371-05.

In ASTM Annual Book of Standards; American Society for Testing and

Materials: West Conshohocken, PA, 2005.

(31) American Society for Testing and Materials. Standard test method

for kinematic viscosity of transparent and opaque liquids (and calculation

of dynamic viscosity), ASTM D445-06. In ASTM Annual Book of Standards;

American Society for Testing and Materials: West Conshohocken, PA, 2006.

(32) American Society for Testing and Materials. Standard test method

for evaluating lubricity of diesel fuels by high frequency reciprocating rig

(HFRR), ASTM D6079-04. In ASTM Annual Book of Standards; American

Society for Testing and Materials: West Conshohocken, PA, 2004.

(33) European Committee for Standardization (CEN). Fat and oil

deriVatiVes. Fatty acid methyl esters (FAME). Determination of oxidatiVe

stability (accelerated oxidation test), EN 14112:2003; European Committee

for Standardization (CEN): Brussels, Belgium, 2003.

(34) American Oil Chemists’ Society. Official Methods and Recommended Practices of the American Oil Chemists’ Society (Method AOCS

Cd 3d-63), 5th ed.; Firestone, D., Ed.; American Oil Chemists’ Society:

Champaign, IL, 1999.

(35) American Society for Testing and Materials. Standard test method

for determination of ignition delay and derived cetane number (DCN) of

diesel fuel oils by combustion in a constant volume chamber, ASTM 6890-

08. In ASTM Annual Book of Standards; American Society for Testing and

Materials: West Conshohocken, PA, 2008.

(36) American Society for Testing and Materials. Standard test method

for determination of total sulfur in light hydrocarbons, spark ignition engine

fuel, diesel engine fuel, and engine oil by ultraviolet fluorescence, ASTM

D5453-08b. In ASTM Annual Book of Standards; American Society for

Testing and Materials: West Conshohocken, PA, 2008.

Figure 1. 1H NMR spectrum of field pennycress oil methyl esters.

Table 3. Physical Properties of Crude Field Pennycress Oil

crude FPOa

oil content (wt %) 29.0

Gardner color 10

cloud point, °C -25 (1)b

pour point, °C -28 (1)

oxidative stability (110 °C), h 5.0 (0.1)

kinematic viscosity, mm2/s

25 °C 70.01 (0.04)

40 °C 40.97 (0.03)

100 °C 9.39 (0.01)

viscosity index 224

specific gravity

25 °C 0.913 (0.001)

40 °C 0.904 (0.001)

lubricity (60 °C), μm 125 (5)

acid value, mg of KOH/g 0.61 (0.03)/0.09 (0.03)c

sulfur, ppm 2

phosphorus, mass % 0.0002

a From ref 19 with the exception of Gardner color, sulfur, and

phosphorus data. b Values in parentheses are standard deviations from

the reported means (n ) 3; n ) 2 in the case of lubricity). c Values

represent AV before (0.61) and after (0.09) acid-catalyzed pretreatment.

4152 Energy & Fuels, Vol. 23, 2009 Moser et al.

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AOCS official method Td 1a-64.38 Specific gravity and viscosity

index (Table 3) were collected according to AOCS official method

Cc 10a-25 and ASTM standard D2270, respectively, as described

previously.19

3. Results and Discussion

3.1. Composition and Physical Properties of Field

Pennycress Oil. The oil content of dried field pennycress seeds

was 29.0 wt %, which was in agreement with the range reported

previously.19-21 The primary FA detected in FPO was erucic

acid (C22:1 13Z; 32.8 wt %; Table 1), which is typical among

members of the Brassicaceae family.16,19,20,39,40 Other FA of

significance included linoleic (C18:2 9Z,12Z; 22.4 wt %),

linolenic (C18:3 9Z,12Z,15Z; 11.8 wt %), oleic (C18:1 9Z; 11.1

wt %), gondoic (C20:1 11Z; 8.6 wt %), palmitic (C16:0; 3.1 wt

%), and nervonic (C24:1 15Z; 2.9 wt %) acids. The overall level

of saturated FA was low (4.6 wt % total), with palmitic acid

comprising the majority of the saturated constituents. Data

derived from the 1

H NMR spectrum of the methyl esters

synthesized here (Figure 1) according to procedure in the

literature41 showing 12.7% FA with ω-3 unsaturation, 25.0%

FA with two double bonds, and 59.0% FA with one double

bond confirmed this result. The percentage of free fatty acids

(FFA) in crude FPO was relatively low, as evidenced by an

AV of 0.61 mg of KOH/g (Table 3). The color of the crude oil

was 10 as measured by the Gardner scale (1 is lightest, 18 is

darkest).

Field pennycress oil primarily contained R- (714 ppm) and

γ-tocopherols (126 ppm), with the - (6 ppm) and δ-homologues

(5 ppm) present at significantly lower levels (Table 4). The total

tocopherol content was 851 ppm, which was higher than that

reported for common crude commodity vegetable oils such as

palm (642 ppm, combined), sunflower (546 ppm), and safflower

(413 ppm) oils, with the notable exception of soybean.42 The

combined tocopherol contents of refined, bleached, and deodorized (RBD) SBO and soybean oil methyl esters (SME) prepared

from crude SBO were 75719 and 130143 ppm, respectively.

The principle phytosterols in FPO were sitosterol (3.88 mg/g)

and campesterol (3.00 mg/g), with brassicasterol (0.76 mg/g),

avenasterol (0.44 mg/g), cholesterol (0.27 mg/g), and stigmasterol

(0.21 mg/g) accounting for the remaining phytosterol content (Table

4). The combined phytosterol concentration was 8.55 mg/g,

which was higher than that previously found for RBD SBO

(4.29 mg/g).19 As was the case here, brassicasterol normally

comprises 5-20% of total phytosterols in oils from members

of the Brassicaceae family (9% for FPO).44,45

Although seed meals from members of the Brassicaceae

family are known to contain significant quantities of sulfurcontaining glucosinolates, crude FPO was largely free of sulfur

content (2 ppm; Table 3) as a result of the polar nature of

glucosinolates and their decomposition products.14 Crude FPO

contained a very low amount of phosphorus (0.0002 mass %;

Table 3).

As summarized in a previous report, crude FPO exhibited

kinematic viscosities at 25, 40, and 100 °C of 70.01, 40.97,

and 9.39 mm2

/s, resulting in a viscosity index of 224 (Table

3).19 The CP and PP values of FPO were -25 and -28 °C,

respectively, indicating excellent low temperature operability

versus SBO19 as a result of the low saturated FA content.46 The

oxidative stability of crude FPO, as determined by the Rancimat

method (EN 14112), was 5.0 h. The specific gravities (25 and

40 °C) and lubricity values (Table 3) were in the typical range

reported for vegetable oils.19,20

3.2. Preparation of Methyl Esters from Field Pennycress Oil. Field pennycress oil was subjected to homogeneous

base-catalyzed transesterification to afford FPME employing

classic reaction conditions described previously.5,11,47,48 The

yield of FPME (82 wt %) prepared from crude FPO was

relatively low. Under ideal conditions, base-catalyzed transesterifications normally proceed to near quantitative yield.5,47-49

The cause was the FFA content of crude FPO, as measured by

AV (0.61 mg KOH/g). Free fatty acids react with homogeneous

base catalysts such as sodium methoxide to form soap (sodium

salt of FA) and methanol (or water in the case of sodium

hydroxide), thus irreversibly quenching the catalyst and reducing

product yield.49 To improve the yield of FPME, sulfuric acid

catalyzed pretreatment of crude FPO with methanol was

conducted prior to base-catalyzed transesterification to reduce

the AV of FPO to 0.09 mg of KOH/g (Table 3) following

reaction conditions described previously.11,12,48,50,51 Subsequent

transesterification of acid-pretreated FPO afforded FPME in

excellent (94 wt %) yield. The product prepared from crude

FPO also easily met the specifications for free and total glycerol

in both the ASTM D6751 and EN 14214 biodiesel standards

with values of 0.005 and 0.041 mass %, respectively (Table 2).

(37) American Society for Testing and Materials. Standard test method

for determination of additive elements in lubricating oils by inductively

coupled plasma atomic emission spectroscopy, ASTM D4951-06. In ASTM

Annual Book of Standards; American Society for Testing and Materials:

West Conshohocken, PA, 2006.

(38) American Oil Chemists’ Society. Official Methods and Recommended Practices of the American Oil Chemists’ Society (Method AOCS

Td 1a-64), 5th ed.; Firestone, D., Ed.; American Oil Chemists’ Society:

Champaign, IL, 1999.

(39) Matthaus, B.; Vosmann, K.; Pham, L. Q.; Aitzetmuller, K. J. Am.

Oil Chem. Soc. 2003, 80, 1013–1020. (40) Dorado, M. P.; Ballesteros, E.; Lopez, F. J.; Mittelbach, M. Energy

Fuels 2004, 18, 77–83. (41) Knothe, G.; Kenar, J. A. Eur. J. Lipid Sci. Technol. 2004, 106,

88–96.

(42) Frankel, E. N. Lipid Oxidation; The Oily Press: Bridgewater, 2004;

p 225.

(43) Moser, B. R. Eur. J. Lipid Sci. Technol. 2008, 110, 1167–1174. (44) Kochhar, S. P. Prog. Lipid Res. 1983, 22, 161–188. (45) Phillips, K. M.; Ruggio, D. M.; Toivo, J. I.; Swank, M. A.;

Simpkins, A. H. J. Food Compos. Anal. 2002, 15, 123–142. (46) Moser, B. R. Energy Fuels 2008, 22, 4301–4306. (47) Moser, B. R.; Haas, M. J.; Winkler, J. K.; Jackson, M. A.; Erhan,

S. Z.; List, G. R. Eur. J. Lipid Sci. Technol. 2007, 109, 17–24. (48) Freedman, B.; Pryde, E. H.; Mounts, T. L. J. Am. Oil Chem. Soc.

1984, 61, 1638–1643. (49) Tiwari, A. K.; Kumar, A.; Raheman, H. Biomass Bioenerg. 2007,

31, 569–575. (50) Lotero, E.; Liu, Y.; Lopez, D. E.; Suwannakarn, K.; Bruce, D. A.;

Goodwin, J. G., Jr. Ind. Eng. Chem. Res. 2005, 44, 5353–5363.

Table 4. Tocopherol (ppm) and Phytosterol Contents (mg/g) of

Field Pennycress Oil and the Corresponding Methyl Esters

FPOa FPME

Tocopherols

R-tocopherol 714 (7)b 527 (3)

-tocopherol 6 (0) 6 (1)

δ-tocopherol 126 (3) 105 (3)

γ-tocopherol 5 (0) 5 (0)

∑tococ 851 (6) 644 (2)

Phytosterols

cholesterol 0.27 (0.01) 0.24 (0.01)

brassicasterol 0.76 (0.01) 0.68 (0.03)

campesterol 3.00 (0.07) 2.76 (0.06)

stigmasterol 0.21 (0.01) 0.19 (0.01)

sitosterol 3.88 (0.07) 3.57 (0.09)

avenasterol 0.44 (0.02) 0.42 (0.01)

∑phytod 8.55 (0.17) 7.87 (0.17)

a Data for field pennycress oil is from ref 19. b Values in parentheses

are standard deviations from the reported means. c ∑toco ) sum of

tocopherols. d ∑phyto ) sum of phytosterols.

EValuation of Biodiesel from Field Pennycress Oil Energy & Fuels, Vol. 23, 2009 4153

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The 1

H NMR and FT-IR spectra of FPME were qualitatively

similar to spectra of FAME reported elsewhere.11,41,47 For

example, FPME contained a methyl ester moiety that was

prominently indicated in the 1

H NMR spectrum (Figure 1) by

a strong singlet at around 3.67 ppm and in the FT-IR spectrum

by a strong carbonyl signal at 1742 cm-1

. Furthermore, the

carbonyl and methyl ester carbons of the ester moiety are

indicated in the 13C NMR spectrum by characteristic signals at

174.30 and 51.40 ppm, respectively.

Methanolysis of crude FPO to afford FPME resulted in

reductions in tocopherol and phytosterol contents of 24 and 8%,

respectively (Table 4). The amount of total tocopherols was

reduced from 851 to 644 ppm, and the combined phytosterol

content was reduced from 8.55 to 7.87 mg/g (Table 4). These

results are not surprising, as tocopherols and phytosterols are

nonpolar and should remain soluble in hydrophobic materials

such as biodiesel as opposed to partitioning into polar glycerolic

or aqueous phases during purification. Retention of tocopherol

content is beneficial, as these minor constituents serve as

inhibitors of oxidation.43

3.3. Properties of Field Pennycress Oil Methyl Esters. The

properties of FPME are summarized in Table 2 along with

relevant fuel specifications from the biodiesel standards ASTM

D6751 and EN 14214. For the sake of consistency, all properties

listed in Table 2 and discussed below are from FPME prepared

from crude as opposed to acid-pretreated FPO.

The CN determined as DCN of FPME was 59.8 (Table 2),

which well exceeded the minimum limits of 47 and 51

prescribed in ASTM D6751 and EN 14214, respectively. The

relatively high DCN of FPME can be explained by the presence

of methyl esters of erucic and gondoic acids. In the course of

this work, the DCN of neat methyl erucate and methyl 11(Z)-

eicosenoate (methyl gondoate) were determined for the first time

and were found to be 74.2 and 73.2, respectively, complementing data on other fatty acid alkyl esters.52 The DCN of FPME

is then well-explained taking into consideration the amounts

and DCN of the other major FAME, with the DCN of methyl

oleate being in the range 56-59, that of methyl linoleate being

38.2, and that of methyl linolenate being even lower at 22.7.53

The kinematic viscosity of FPME was 5.24 mm2/s at 40 °C

(Table 2), which was within the range specified in ASTM D6751

but was higher than the maximum specification in EN 14214

(Table 2). The high kinematic viscosity of FPME was largely

a result of the presence of longer-chain (C20+) FAME. For

example, the kinematic viscosity of methyl erucate has been

reported as 7.33 mm2

/s and that of methyl gondoate as 5.77

mm2

/s.54 As these two species, together with smaller amounts

of other FAME in the C20-C24 range, comprised approximately 48% of the FA profile (Table 1) of FPO, the relatively

high kinematic viscosity is well-explained. The kinematic

viscosities of the methyl esters of other major components of

FPME are 4.38 mm2

/s for methyl palmitate, 4.51 mm2/s for

methyl oleate, 3.65 mm2

/s for methyl linoleate, and 3.14 mm2/s

for methyl linolenate.54 Kinematic viscosity data of FPME at

temperatures below 40 °C (20, 0, and -10 °C) are also given

in Table 2. Blending FPME with less viscous biodiesel fuels

represents a potential strategy to satisfy the EN 14214 kinematic

viscosity specification.

The low temperature properties of FPME were determined

by CP, PP, and CFPP. As seen in Table 2, FPME provided CP,

PP, and CFPP values of -10, -18, and -17 °C, respectively.

The relatively low level of saturated FAME contained in FPME

(4.6 wt %; Table 1) was in part attributed to the low temperature

operability of FPME.46 In addition, unsaturated FAME have

markedly lower melting points (mp) than the corresponding

saturated analogues. For instance, the melting points of methyl

esters of stearic (C18:0), oleic, linoleic, and linolenic acids are

39, -20, -35, and -57 °C, respectively.55 Furthermore, the

melting points of methyl gondoate and erucate are -45 and

-34 °C.55,56

The oxidative stability of FPME was 4.4 h, as measured by

the Rancimat method (IP; EN 14112). Addition of antioxidants

or blending with more oxidatively stable feedstocks would be

necessary to satisfy the oxidative stability requirement (IP >

6 h) in EN 14214. FPME was acceptable according to the less

stringent specification (IP > 3 h) in ASTM D6751. It should be

noted that the IP of FPME was in excess of IP reported for

individual unsaturated FAME,57 suggesting that native tocopherols (Table 4) were in part responsible for the oxidative

stability of FAME.43

Both ASTM D6751 and EN 14214 restrict AV to a maximum

value of 0.50 mg of KOH/g. The AV of FPME was easily within

the specified limit with a value of 0.04 mg of KOH/g. FPME

prepared from acid-pretreated FPO displayed an AV of 0.02

mg of KOH/g.

The wear scar generated by FPME by the high-frequency

reciprocating rig (HFRR) lubricity method ASTM D6079 (60

°C) was 125 μm (Table 2). Lubricity (ASTM D6079) is not

specified in ASTM D6751 or EN 14214, but it is included in

the petrodiesel standards ASTM D975 and EN 590 with

maximum wear scars of 520 and 460 μm, respectively. Fuels

with poor lubricity can cause failure of diesel engine parts that

rely on lubrication from fuels, such as fuel pumps and

injectors.2,3,58 As expected, the lubricity of FPME was considerably below the maximum limits set forth in the aforementioned

petrodiesel standards, which was in agreement with several

previous studies indicating that biodiesel possessed inherent

lubricity.58-60

Sulfur content is limited in ASTM D6751 and EN 14214 to

maximum values of 15 and 10 ppm, respectively. The sulfur

content of FPME was 7 ppm (Table 2), which was below the

specified maximum limits but higher than that for FPO (2 ppm).

Anthropogenic introduction of sulfur to FPME by the use of a

sulfur-containing drying agent (MgSO4) during purification (see

section 2.4) was attributed to the small increase in sulfur content

observed here. Phosphorus content is also limited in ASTM

D6751 and EN 14214 to a maximum value of 0.001 mass %.

FPME contained no phosphorus.

Although surface tension is not specified in either ASTM

D6751 or EN 14214, it is nevertheless an important property

that affects fuel atomization in combustion chambers in diesel

engines.61 The surface tensions (at 24 and 40 °C) of FPME were

nearly identical (Table 2) to the values reported in the literature

(51) Naik, M.; Meher, L. C.; Naik, S. N.; Das, L. M. Biomass Bioenerg.

2008, 32, 354–357. (52) Knothe, G.; Matheaus, A. C.; Ryan, T. W., III. Fuel 2003, 82, 971–

975.

(53) Knothe, G.; Bagby, M. O.; Ryan, T. W., III. SAE Tech. Pap. Ser.

1997, 971681. (54) Knothe, G.; Steidley, K. R. Fuel 2005, 84, 1059–1065.

(55) Anonymous. Dictionary Section. In The Lipid Handbook, 3rd ed.;

Gunstone, F. D., Harwood, J. L., Dijkstra, A. J., Eds.; CRC Press: Boca

Raton, 2007; pp 444-445.

(56) Chang, S. P.; Rothfus, J. A. J. Am. Oil Chem. Soc. 1996, 73, 403–

410.

(57) Moser, B. R. J. Am. Oil Chem. Soc. 2009, 86, 699-706.

(58) Knothe, G.; Steidley, K. R. Energy Fuels 2005, 19, 1192–1200. (59) Moser, B. R.; Cermak, S. C.; Isbell, T. A. Energy Fuels 2008, 22,

1349–1352. (60) Suarez, P. A. Z.; Moser, B. R.; Sharma, B. K.; Erhan, S. Z. Fuel

2009, 88, 1143–1147. (61) Ejim, C. E.; Fleck, B. A.; Amirfazli, A. Fuel 2007, 86, 1534–1544.

4154 Energy & Fuels, Vol. 23, 2009 Moser et al.

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for SME, indicating that adequate fuel atomization should not

be an issue with FPME.62

4. Conclusions

Biodiesel was prepared in high yield from field pennycress

oil by alkali-catalyzed transesterification with methanol both

before and after acid pretreatment. Fuel properties such as low

temperature operability, cetane number, kinematic viscosity,

oxidative stability, lubricity, surface tension, and others were

determined. Excellent low temperature properties were observed,

as indicated by low CP, PP, and CFPP values. The methyl esters

provided a high derived cetane number as a result of the high

contents of methyl esters of erucic and gondoic acids (32.8 and

8.6 wt %). Also reported for the first time are the derived cetane

numbers of methyl esters of erucic and gondoic acids, which

were 74.2 and 73.2, respectively. As a result of the high content

of methyl esters of erucic, gondoic, and other acids with 20 or

more carbons, FPME exhibited a kinematic viscosity in excess

of the EN 14214 limit but within the ASTM D6751 specification. Blending with less viscous feedstocks would ameliorate

the high viscosity of FPME. The oxidative stability of FPME

was acceptable according to the limit contained in ASTM

D6751, but not EN 14214. Consequently, the addition of

antioxidant additives or blending with more stable feedstocks

would be necessary to provide acceptable oxidative stability

values according to the more stringent EN 14214 limit. The

lubricity, surface tension, AV, and sulfur as well as phosphorus

contents of FPME were satisfactory and within accepted limits,

where applicable. Thus, FPME represents an acceptable substitute for petrodiesel, as FPME compares favorably to most

biodiesel fuel specifications.

Acknowledgment. The authors acknowledge Dr. Jill K. WinklerMoser for collection of phytosterol data as well as Benetria N.

Banks and Kevin R. Steidley for excellent technical assistance. Dr.

Karl Vermillion is acknowledged for acquisition of NMR spectra.

EF900337G

(62) Doll, K. M.; Moser, B. R.; Erhan, S. Z. Energy Fuels 2007, 21,

3044–3048.

EValuation of Biodiesel from Field Pennycress Oil Energy & Fuels, Vol. 23, 2009 4155

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