9934
Energy & Fuels 2009, 23, 4149–4155
4149
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
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Publication Date (Web): July 2, 2009 | doi: 10.1021/ef900337g
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
† 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) 6816511. 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.
10.1021/ef900337g
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,
(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.
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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4150
Energy & Fuels, Vol. 23, 2009
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
(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.
Moser et al.
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, β 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.
(24) Evangelista, R. L. Ind. Crops Prod. 2009, 29, 189–196.
EValuation of Biodiesel from Field Pennycress Oil
Energy & Fuels, Vol. 23, 2009 4151
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Table 1. Fatty Acid Composition (wt %) of Field Pennycress
Oil (FPO)
fatty acida
FPO
C14:0
C16:0
C16:1 9c
C18:0
C18:1 9c
C18:1 11c
C18:2 9c, 12c
C18:3 9c, 12c, 15c
C20:0
C20:1 11c
C20:2 11c, 14c
C22:0
C22:1 13c
C22:2 13c, 16c
C22:3 13c, 16c, 19c
C24:1 15c
unknown (sum)
∑saturatedb
∑monounsaturatedc
∑polyunsaturatedd
∑C20+e
0.1
3.1
0.2
0.5
11.1
1.5
22.4
11.8
0.3
8.6
1.6
0.6
32.8
0.7
0.3
2.9
1.5
4.6
55.6
38.3
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.
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. 1H 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
(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.
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
free glycerol, mass %
total glycerol, mass %
cloud point, °C
pour point, °C
cold filter plugging point, °C
oxidative stability (110 °C), h
kinematic viscosity, mm2/s
-10 °C
0 °C
20 °C
40 °C
lubricity (HFRR, 60 °C), µm
sulfur, ppm
phosphorus, mass %
surface tension, mN/m
24 °C
40 °C
cetane number
0.020 max
0.240 max
report
3 min
0.50 max 0.04 (0.03)/
0.02 (0.02)a,b
0.020 max 0.005
0.250 max 0.041
-10 (1)
-18 (1)
c
-17 (1)
6 min
4.4 (0.1)
1.9-6.0
d
15 max
0.001 max
3.5-5.0
d
10 max
0.001 max
35.52
16.70
8.65
5.24 (0.01)
125 (3)
7
0.0000
47 min
51 min
31.0 (0.1)
29.6 (0.1)
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.
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 β-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
(27) Dutta, P. C.; Normén, 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.
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Moser et al.
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 %)
Gardner color
cloud point, °C
pour point, °C
oxidative stability (110 °C), h
kinematic viscosity, mm2/s
25 °C
40 °C
100 °C
viscosity index
specific gravity
25 °C
40 °C
lubricity (60 °C), µm
acid value, mg of KOH/g
sulfur, ppm
phosphorus, mass %
29.0
10
-25 (1)b
-28 (1)
5.0 (0.1)
70.01 (0.04)
40.97 (0.03)
9.39 (0.01)
224
0.913 (0.001)
0.904 (0.001)
125 (5)
0.61 (0.03)/0.09 (0.03)c
2
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.
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.
(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.
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 Ingenieurbüro 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
(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 689008. 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.
EValuation of Biodiesel from Field Pennycress Oil
Energy & Fuels, Vol. 23, 2009 4153
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 1H 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 β- (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
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FPOa
FPME
R-tocopherol
β-tocopherol
δ-tocopherol
γ-tocopherol
∑tococ
Tocopherols
714 (7)b
6 (0)
126 (3)
5 (0)
851 (6)
527 (3)
6 (1)
105 (3)
5 (0)
644 (2)
cholesterol
brassicasterol
campesterol
stigmasterol
sitosterol
avenasterol
∑phytod
Phytosterols
0.27 (0.01)
0.76 (0.01)
3.00 (0.07)
0.21 (0.01)
3.88 (0.07)
0.44 (0.02)
8.55 (0.17)
0.24 (0.01)
0.68 (0.03)
2.76 (0.06)
0.19 (0.01)
3.57 (0.09)
0.42 (0.01)
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.
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
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4154
Energy & Fuels, Vol. 23, 2009
The 1H 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 1H 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.
(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.
Moser et al.
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
(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.
EValuation of Biodiesel from Field Pennycress Oil
for SME, indicating that adequate fuel atomization should not
be an issue with FPME.62
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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
(62) Doll, K. M.; Moser, B. R.; Erhan, S. Z. Energy Fuels 2007, 21,
3044–3048.
Energy & Fuels, Vol. 23, 2009 4155
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
Supplied by the United States Department of Agriculture, National Center for Agricultural
Utilizaton Research, Peoria, Illinois