Evaluation of alkyl esters from Camelina sativa oil as biodiesel and as blend

components in ultra low-sulfur diesel fuel q

Bryan R. Moser *, Steven F. Vaughn

United States Department of Agriculture, Agricultural Research Service, National Center for Agricultural Utilization Research, 1815 N. University St., Peoria, IL 61604, USA

article info

Article history:

Received 15 December 2008

Received in revised form 10 August 2009

Accepted 12 August 2009

Available online 8 September 2009

Keywords:

Biodiesel

Camelina sativa

Diesel

Fuel properties

Methyl esters

abstract

Methyl and ethyl esters were prepared from camelina [Camelina sativa (L.) Crantz] oil by homogenous

base-catalyzed transesterification for evaluation as biodiesel fuels. Camelina oil contained high percentages of linolenic (32.6 wt.%), linoleic (19.6 wt.%), and oleic (18.6 wt.%) acids. Consequently, camelina oil

methyl and ethyl esters (CSME and CSEE) exhibited poor oxidative stabilities and high iodine values versus methyl esters prepared from canola, palm, and soybean oils (CME, PME, and SME). Other fuel properties of CSME and CSEE were similar to CME, PME, and SME, such as low temperature operability, acid

value, cetane number, kinematic viscosity, lubricity, sulfur and phosphorous contents, as well as surface

tension. As blend components in ultra low-sulfur diesel fuel, CSME and CSEE were essentially indistinguishable from SME and soybean oil ethyl ester blends with regard to low temperature operability, kinematic viscosity, lubricity, and surface tension.

Published by Elsevier Ltd.

1. Introduction

Biodiesel, defined as an alternative fuel composed of mono-alkyl esters of long-chain fatty acids prepared from vegetable oils

or animal fats, has attracted considerable interest as a substitute

or blend component for conventional petroleum diesel fuel (petrodiesel). Biodiesel possesses significant technical advantages over

petrodiesel, such as derivation from renewable feedstocks, displacement of imported petroleum, inherent lubricity, essentially

no sulfur content, superior flash point and biodegradability, reduced toxicity, as well as a reduction in most exhaust emissions.

Important disadvantages of biodiesel include inferior oxidative

and storage stability, lower volumetric energy content, inferior

low temperature operability, and higher NOx exhaust emissions

(Mittelbach and Remschmidt, 2004; Knothe et al., 2005;

McCormick et al., 2006; Moser, 2009a). Additionally, the high cost

of commodity vegetable oils, such as soybean oil in the United

States, represents a serious threat to the economic viability of

the biodiesel industry (Paulson and Ginder, 2007; Retka-Schill,

2008a). Presently, feedstock acquisition accounts for up to 85% of

biodiesel production costs (Paulson and Ginder, 2007; Retka-Schill,

2008a).

Feedstocks for biodiesel production vary considerably with

location according to climate and availability. Generally, the most

abundant lipid in a particular region is the most common feedstock. Thus, rapeseed oil is predominantly used in Europe, palm

oil predominates in tropical countries, and soybean oil and animal

fats are primarily used in the United States (Mittelbach and Remschmidt, 2004; Knothe et al., 2005; Moser, 2009a). However, many

of these oils are prohibitively expensive and have competing

food-related uses. Consequently, the development of alternative

feedstocks for biodiesel production that meet all or most of the following criteria has attracted considerable research attention: high

oil content, low agricultural inputs, favorable fatty acid composition, compatibility with existing farm equipment and infrastructure, production in a sustainable fashion in off-season or in

agriculturally undesirable lands, definable growth seasons, and

uniform seed maturation rates. Selected recent examples of biodiesel produced from feedstock oils that meet at least a majority of

the above criteria include moringa (Rashid et al., 2008), jatropha

(Tiwari et al., 2007), field pennycress (Moser et al., 2009a), and

wild mustard (Jham et al., 2009).

Camelina [Camelina sativa (L.) Crantz], also known as false flax

or gold-of-pleasure, is a spring annual broadleaf oilseed herb of

the Brassicaceae family that grows well in temperate climates.

Camelina has several positive agronomic attributes: low agricultural inputs, cold-weather tolerance, short growing season

(85–100 days), compatibility with existing farm equipment, and

grows well in semiarid regions and in low-fertility or saline soils.

These qualities are unusual for an oilseed crop (Putnam et al.,

1993; Retka-Schill, 2008b; Sawyer, 2008). Other more common

0960-8524/$ - see front matter Published by Elsevier Ltd.

doi:10.1016/j.biortech.2009.08.054

q 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.

* Corresponding author. Tel.: +1 309 681 6511; fax: +1 309 681 6340.

E-mail address: Bryan.Moser@ars.usda.gov (B.R. Moser).

Bioresource Technology 101 (2010) 646–653

Contents lists available at ScienceDirect

Bioresource Technology

journal homepage: www.elsevier.com/locate/biortech
oilseed crops, such as canola, soybean, rapeseed, and sunflower,

have higher water, pesticide, and fertilizer requirements (Budin

et al., 1995; Sawyer, 2008). Moreover, camelina, unlike soybean,

thrives in cool, arid climates and is nicely adapted to the more

northerly regions of North America, Europe, and Asia. As such, it

may serve as a rotational crop for winter wheat, which would facilitate disrupting undesirable weed and pest cycles (Retka-Schill,

2008b). Camelina yields an average of 420–640 L/ha and the protein and fiber content in its meal byproduct is comparable to that

of soybean meal (Retka-Schill, 2008b; Sawyer, 2008). The seeds of

camelina contain 28–40 wt.% of vegetable oil (Putnam et al., 1993;

Budin et al., 1995), which is far superior to that typically found in

soybeans (18–22 wt.%). Camelina has traditionally been used for

relatively high value products such as culinary oil, cosmetics, and

animal feed (Sawyer, 2008).

Examples of camelina oil appearing in the scientific literature

include its direct use as a fuel for diesel transport engines

(Bernardo et al., 2003) and as a chemical feedstock in the enzymatic production of long-chain esters (Steinke et al., 2000a,b,

2001). Camelina oil may also serve as an industrial source of alinolenic acid (9Z,12Z,15Z-octadecatrienoic acid), as it generally

contains 30–45 wt.% of this constituent (Leonard, 1998; Ni Eidhin

et al., 2003; Krist et al., 2006; Sawyer, 2008). Moreover, camelina

oil was examined as a feedstock for biodiesel production (Frohlich

and Rice, 2005). We follow up in the current study with a more

thorough examination of the fuel properties of methyl and ethyl

esters prepared from alcoholysis of camelina oil, along with their

evaluation as blend components in ultra low-sulfur diesel fuel

(ULSD, <15 ppm S). A comparison with canola and palm oil methyl

esters (CME and PME, respectively), along with soybean oil methyl

and ethyl esters (SME and SEE, respectively), was also of interest.

Important fuel properties elucidated of the alkyl esters, both neat

and blended with ULSD, included low temperature operability, oxidative stability, cetane number, acid value, sulfur and phosphorous

contents, lubricity, iodine value, surface tension, and kinematic

viscosity.

Although biodiesel can be used in modern unmodified diesel

engines in the neat form, it is more commonly encountered as a

blend component in petrodiesel, such as B20 (20% biodiesel by volume in petrodiesel). Currently, blends of up to B5 are allowed in

ASTM D975 (ASTM, 2008a) (Table 1), the US diesel fuel standard.

In addition, ASTM D7467 (ASTM, 2008b) (Table 1) was recently

adopted for blends from B6 to B20 in petrodiesel. Biodiesel must

be certified as acceptable according to ASTM D6751 (ASTM,

2008c) (Table 1), the B100 standard, before its use as a fuel or blend

component. Moreover, EN 14214 (Committee for Standardization,

2003) (Table 1) and EN 590 (Committee for Standardization,

2004) are the European Union standards for biodiesel and petrodiesel (up to B5), respectively.

2. Experimental section

2.1. Materials

Camelina seeds were purchased from Marx Foods (Atlantic

Highlands, NJ). ULSD, described as fungible by the manufacturer,

was donated by a major petrochemical company that wished to remain anonymous. Conductivity and corrosion inhibitor additives

were added by the manufacturer, but no drag reducing, lubricity,

low temperature, or antioxidant additives were added. The commercial adsorbent Magnesolwas purchased from The Dallas

Group of America, Inc. (Whitehouse, NJ). Refined, bleached, and

deodorized canola, palm, and soybean oils were purchased from

KIC Chemicals, Inc (New Platz, NY). Fatty acid methyl (FAME) and

ethyl ester standards were purchased from Nu-Chek Prep, Inc. (Elysian, MN). All other chemicals and reagents were obtained from

Sigma–Aldrich Corp (St. Louis, MO).

2.2. Camelina oil extraction

Camelina seeds (1000 g) were ground in a coffee grinder and oil

was extracted with hexane for 24 h in a Soxhlet apparatus. Hexane

was removed by rotary evaporation under reduced pressure

(10 mbar; 30 C). For determination of total oil content, 10.0 g triplicates of ground seed were extracted (Soxhlet) for 24 h, and after

hexane was removed by rotary evaporation (10 mbar; 30 C) the

weight of the residual oil was calculated. The percentage of oil

recovered from the samples was 30.5 wt.% (rM ± 0.4%).

2.3. Methanolysis of camelina oil

Methanolysis of camelina oil was conducted in a 500 mL threenecked round bottom flask connected to a reflux condenser and a

mechanical magnetic stirrer set at 1200 rpm. Initially, camelina

oil (180 g, 200 mL, 0.202 mol) and methanol (49 mL, 1.21 mol)

were added to the flask and heated to 60 C (internal reaction temperature monitored by digital temperature probe), followed by

addition of 1.0 wt.% NaOCH3 (25 wt.% in CH3OH). After 1.5 h of

reaction the mixture was equilibrated to room temperature and

transferred to a separatory funnel. The lower glycerol phase was

removed by gravity separation (>2 h settling time) followed by removal of methanol from the upper crude methyl ester phase by reduced pressure (10 mbar; 30 C) rotary evaporation. The crude

methyl esters were treated with 2.5 wt.% Magnesolat 65 C for

25 min with continuous stirring (500 rpm), followed by filtration

to remove the adsorbent to provide C. sativa oil methyl esters

(CSME, 160 g, 89 wt.% yield based on original mass of camelina

oil). Canola, palm, and soybean oil methyl esters were prepared

in a similar fashion in essentially quantitative (>98 wt.%) yield.

Free and total glycerol contents of CSME, CME, PME, and SME were

determined according to ASTM D6584.

2.4. Ethanolysis of camelina oil

Ethanolysis of camelina oil was accomplished largely as described in Section 2.3. Initially, camelina oil (180 g, 200 mL,

0.202 mol) and ethanol (110 mL, 1.82 mol) were added to the reaction flask and heated to 70 C (internal reaction temperature monitored by digital temperature probe), followed by addition of

Table 1

Selected specifications from biodiesel and ULSD fuel standards.

Biodiesel ULSD

ASTM D6751 EN 14214 ASTM D975 ASTM D7467

vol.% BD 100 100 0–5 6–20

CP (C) Report – Not

specifieda

Not

specifieda

PP (C) – – Not

specifieda

Not

specifieda

CFPP (C) – Variableb Not

specifieda

Not

specifieda

OSI, 110 C (h) 3 min 6 min – 6 min

t, 40 C (mm2/s) 1.9–6.0 3.5–5.0 1.9–4.1 1.9–4.1

Lub, 60 C (lm) – – 520 max 520 max

AV (mg KOH/g) 0.50 max 0.50 max – 0.30 max

IV (g I2/100 g) – 120 max – –

CN 47 min 51 min 40 min 40 min

S (ppm) 15 max 10 max 15 max 15 max

P (mass%) 0.001 max 0.001 max – –

a There are no requirements for low temperature operability in ASTM D975 or

D7467, only guidance.

b Variable by location and time of year.

B.R. Moser, S.F. Vaughn / Bioresource Technology 101 (2010) 646–653 647
1.0 wt.% KOH (1.8 g). After 1.5 of reaction the mixture was cooled

to room temperature and ethanol was removed by rotary evaporation (10 mbar; 35 C) followed by removal of glycerol by gravity

separation (>2 h settling time). The crude ethyl esters were treated

with 2.5 wt.% Magnesolas described in Section 2.3 to afford purified C. sativa oil ethyl esters (CSEE, 151 g, 84 wt.% yield). Soybean

oil ethyl esters were prepared in a similar fashion in high yield

(94 wt.%). Free and total glycerol contents of CSEE and SEE were

determined according to ASTM D6584.

2.5. Fatty acid profile by GC

Fatty acid methyl esters (FAME) of camelina, canola, palm, and

soybean oils 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 lm film thickness). Carrier gas was He at 1 mL/min. The

oven temperature was initially held at 150 C for 15 min, then increased to 210 C at 2 C/min, followed by an increase to 220 C

at 50 C/min, which was then held for 10 min. The injector and

detector temperatures were set to 240 C and 270 C, respectively.

FAME peaks were identified by comparison to the retention times

of reference standards.

2.6. Fuel properties of alkyl esters and blends with ULSD

Cloud and pour point (CP and PP, respectively) determinations

(triplicates, means reported) were made according to ASTM

D5773 and ASTM D5949, respectively, using a model PSA-70S

Phase Technology Analyzer (Richmond, B.C., 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) was measured (triplicates, means reported)

in accordance with ASTM D6371 utilizing a model FPP-5Gs ISL

Automatic CFPP Analyzer (Houston, TX).

Kinematic viscosity (t, mm2

/s) was determined (triplicates,

means reported) with Cannon–Fenske viscometers (Cannon Instrument Co., State College, PA) at 40 C in accordance with ASTM

D445.

Lubricity (Lub, lm) determinations (duplicates, means reported) were performed at 60 C (±1 C) according to ASTM

D6079 using a high-frequency reciprocating rig (HFRR) lubricity

tester (PCS Instruments, London, England) from Lazar Scientific

(Granger, IN). Reported wear scar (lm) values were the result of

measuring the maximum lengths of the x- and y-axes of each wear

scar with a Prior Scientific (Rockland, Massachusetts, USA) Epimat

model M4000 microscope, followed by calculating the average of

these maximum values.

Oil stability index (OSI, h) was measured (triplicates, means reported) following EN 14112 with a Metrohm USA, Inc. (Riverview,

FL) model 743 Rancimat instrument. For biodiesel (B100) samples,

the flow rate of air through 3 ± 0.01 g of sample was 10 L/h with a

block temperature of 110 C and a correction factor (DT) of 1.5 C.

The glass conductivity measuring vessel contained 50 ± 0.1 mL of

deionized water. For biodiesel samples blended with ULSD, the

flow rate of air through 7.5 ± 0.1 g of sample was 10 L/h with a

block temperature of 110 C (DT = 1.5 C). The conductivity measuring vessel contained 60 ± 0.1 mL of deionized water. Longer

reaction vessels and gas inlet tubes were used for the blends to

reduce ULSD evaporation. OSI was determined as the inflection

point of a computer-generated plot of conductivity (lS/cm) of

deionized water versus time (h). Experiments were terminated

at 24 h.

Acid value (AV, mg KOH/g) titrations (triplicates, means reported) were performed as described in American Oil Chemists’

Society (AOCS) official method Cd 3d-63 using a Metrohm 836 Titrando (Westbury, NY) autotitrator equipped with a model 801 stirrer and a Metrohm 6.0229.100 Solvotrode. However, the official

method was modified for scale to use 2 g of sample and 0.02 M

KOH. The titration endpoint was automatically determined by

the instrument and visually verified using a phenolphthalein indicator. Iodine value (IV) was calculated from the fatty acid profile

according to AOCS Cd 1c-85.

Surface tension (c, mN/m) was determined (quintuplets, means

reported) at 24 ± 1 C 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 l10MC burette. 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.

Sulfur (S, ppm) and phosphorous (P, mass%) were measured by

Magellan Midstream Partners, L.P. (Kansas City, KS) according to

ASTM standards D5453 and D4951, respectively. Derived cetane

number (DCN) was determined by Southwest Research Institute

(San Antonio, TX) utilizing an Ignition Quality TesterTM (IQT) following ASTM D6890.

3. Results and discussion

3.1. Composition and physical properties of camelina oil

The oil content of camelina seeds was 30.5 wt.%, which was in

agreement with the range reported in previous studies (Budin

et al., 1995; Leonard, 1998; Sawyer, 2008). The primary fatty acid

identified in camelina oil was linolenic acid (C18:3; Table 2) at

32.6 wt.%, with other unsaturated fatty acids such as linoleic

(C18:2; 19.6 wt.%), oleic (C18:1; 18.6 wt.%), and eicosenoic

(C20:1; 12.4 wt.%) acids also detected in significant quantities.

The majority of the remaining fatty acids aside from erucic

acid (C22:1; 2.3 wt.%) were saturated species such as palmitic

(C16:0; 6.8 wt.%), stearic (C18:0; 2.7 wt.%), and arachidic (C20:0;

1.5 wt.%) acids. These results are in close agreement with prior reports on the fatty acid profile of camelina oil (Budin et al., 1995;

Frohlich and Rice, 2005; Krist et al., 2006). The relatively high polyunsaturated (88.7 wt.%) and trienoic (33.4 wt.%) acid contents of

Table 2

Fatty acid composition (wt.%) of camelina oil (CSO), with canola (CO), palm (PO), and

soybean (SBO) oils shown for comparison.

Fatty acida CSO CO PO SBO

C12:0 Trace 0.3

C14:0 0.1 1.1

C16:0 6.8 4.6 41.9 10.5

C18:0 2.7 2.1 4.6 4.1

C20:0 1.5 0.7 0.3 Trace

C22:0 0.2 0.3 Trace

C16:1 9 Trace 0.2 0.2

C18:1 9 18.6 64.3 41.2 22.5

C18:1 11 1.1 1.6

C18:2 9, 12 19.6 20.2 10.3 53.6

C18:3 9, 12, 15 32.6 7.6 0.1 7.7

C20:1 11 12.4 Trace Trace

C20:2 11, 14 1.3 Trace

C20:3 11, 14, 17 0.8

C22:1 13 2.3

C24:1 15 Trace

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

bond located at carbon 9 (methyl 9Z-octadecenoate; methyl oleate). All double

bonds are cis.

648 B.R. Moser, S.F. Vaughn / Bioresource Technology 101 (2010) 646–653
camelina oil resulted in an IV (151) that was substantially higher

than the other oils listed in Table 3.

The AV of crude camelina oil was 2.06 mg KOH/g (Table 3). Refined, bleached and deodorized (RBD) canola, palm, and soybean

oils exhibited very low AV (<0.16 mg KOH/g, Table 3). The oil stability index (OSI) of camelina oil, determined at 110 C according to

the Rancimat method (EN 14112) was lowest among the oils listed

in Table 3 with a value of 2.2 h and was consistent with its high

polyunsaturated fatty acid content. The CP and PP of camelina oil

were 10 C and 17 C, respectively. With the exception of palm

oil, these values did not vary significantly from the other oils listed

in Table 3. The kinematic viscosity (40 C) of camelina oil

(28.28 mm2

/s) was noticeably lower than the values obtained for

palm, canola, and soybean oils (41.69, 36.28, and 31.49 mm2

/s,

respectively, Table 3). The wear scar generated by camelina oil

according to ASTM D6079 (60 C) was 128 lm (shorter wear scars

indicate better lubricity), which with the exception of palm oil

(148 lm) did not vary significantly from the other oils in Table 3.

The surface tension at 24 C and 40 C of camelina oil (32.3 and

30.7 nN/m, respectively) was similar to the values obtained for canola, palm, and soybean oils (Table 3).

3.2. Preparation and quality of alkyl esters from camelina oil

Camelina oil was subjected to homogenous base-catalyzed

transesterification employing classic conditions described previously (Freedman et al., 1984; Moser, 2009a) to afford camelina

oil methyl (CSME) and ethyl (CSEE) esters. The yields of CSME

(89 wt.%) and CSEE (84 wt.%) were not quantitative. Under ideal

conditions, base-catalyzed transesterifications normally proceed

to completion (Tiwari et al., 2007). The culprit was most likely

the free fatty acid content of camelina oil, as measured by AV. Free

fatty acids react with homogenous base catalysts such as sodium

hydroxide and methoxide to form soap (sodium salt of fatty acid)

and water (or methanol in the case of sodium methoxide), thus

irreversibly quenching the catalyst and reducing product yield

(Lotero et al., 2005).

The AVs of CSME and CSEE were 0.31 and 0.41 mg KOH/g,

respectively (Table 4). Although these values were higher than

those obtained from methanolysis of RBD canola, palm, and soybean oils (Table 4), they were below the maximum prescribed limits in ASTM D6751 and EN 14214 (<0.50 g KOH/g; Table 1). The AV

of SEE was 0.37 mg KOH/g (Table 4), which was comparable to

CSME and CSEE. Additionally, the free and total glycerol contents

of alkyl esters from camelina, canola, palm, and soybean oils were

below the maximum allowable limits specified in ASTM D6751 and

EN 14214.

3.3. Physical properties of camelina oil alkyl esters

The low temperature operability of CSME and CSEE was measured through CP, PP, and CFPP determination. As seen in Table

4, CSME provided CP, PP, and CFPP values of 3, 4, and 3 C,

respectively, which were indistinguishable from CSEE. Methyl esters prepared from canola oil yielded superior low temperature

properties, as indicated by lower CP, PP, and CFPP. The values obtained for SME and SEE were similar to CSME and CSEE. As expected, PME exhibited noticeably diminished low temperature

operability in comparison to CSME and CSEE (Moser et al., 2008;

Moser, 2008a). Strategies to improve the low temperature operability of CSME and CSEE may include the use of additives, blending

with biodiesel produced from other feedstocks, crystallization fractionation, transesterification with long- or branched-chain alcohols, and/or blending with petrodiesel (Knothe et al., 2005;

Moser, 2008a, 2009a; Moser et al., 2008).

The OSI values of CSME and CSEE were 2.5 and 2.9 h (Table 4),

respectively. Methyl esters from canola (6.4 h), palm (10.3 h) and

Table 3

Fatty acid trends and physical properties of camelina, canola, palm, and soybean oils.

CSO CO PO SBO

R saturatesa 11.3 7.7 48.2 14.6

R unsaturatesb 88.7 92.3 51.8 85.4

R polyunsaturatesc 54.3 27.8 10.4 61.3

R C20+d 16.5 Trace Trace

R trienese 33.4 7.6 0.1 7.7

CP (C) 10 (1)f 9 (1) 11 (1) 7 (1)

PP (C) 17 (1) 21 (1) 8 (1) 9 (1)

OSI, 110 C (h) 2.2 (0.2) 10.3 (0.2) 24.7 (0.2) 8.3 (0.1)

t, 40 C (mm2/s) 28.28

(0.05)

36.28

(0.05)

41.69

(0.02)

31.49

(0.02)

Lub, 60 C (lm) 128 (2) 137 (3) 148 (4) 124 (1)

AV (mg KOH/g) 2.06 (0.04) 0.04 (0.03) 0.15 (0.03) 0.03 (0.02)

IV (g I2/100 g) 151 110 54 134

c, 24 C (mN/m) 32.3 (0.1) 34.2 (0.1) 33.8 (0.1) 34.2 (0.1)

c, 40 C (mN/m) 30.7 (0.1) 32.2 (0.1) 32.0 (0.1) 32.2 (0.1)

a R saturates (wt.%) = C12:0 + C14:0 + C16:0 + C18:0 + C20:0 + C22:0. b R unsaturates (wt.%) = C16:1 + C18:1 + C18:2 + C18:3 + C20:1 + C20:2 + C20:3 +

C22:1 + C24:1. c R polyunsaturates (wt.%) = C18:2 + C18:3 + C20:2 + C20:3. d R C20+ (wt.%) = C20:0 + C22:0 + C20:1 + C20:2 + C20:3 + C22:1 + C24:1. e R trienes (wt.%) = C18:3 + C20:3. f Values in parentheses are standard deviations from the reported means.

Table 4

Fuel properties of camelina, canola, palm, and soybean oil alkyl esters, along with ultra low-sulfur diesel fuela

.

CSME CSEE CME PME SME SEE ULSD

CP (C) 3 (1)b 2 (1) 0 (1) 17 (1) 0 (1) 0 (1) 18 (1)

PP (C) 4 (1) 4 (1) 9 (1) 15 (1) 3 (1) 4 (1) 23 (1)

CFPP (C) 3 (1) 3 (1) 7 (1) 12 (1) 4 (1) 5 (1) 17 (1)

OSI, 110 C (h) 2.5 (0.1) 2.9 (0.1) 6.4 (0.1) 10.3 (0.1) 5.0 (0.1) 6.0 (0.1) >24

t, 40 C (mm2/s) 4.15 (0.01) 4.48 (0.01) 4.42 (0.23) 4.58 (0.01) 4.12 (0.01) 4.41 (0.02) 2.30 (0.01)

Lub, 60 C (lm) 122 (3) 145 (5) 169 (1) 172 (1) 135 (1) 137 (3) 571 (5)

AV (mg KOH/g) 0.31 (0.01) 0.41 (0.02) 0.01 (0.01) 0.01 (0.01) 0.01 (0.01) 0.37 (0.01) 0

IV (g I2/100 g) 151 144 110 54 134 127 Ndc

S (ppm) 3 3 2 2 1 1 8

P (mass%) 0 0 0 0 0 0 nd

CN 52.8 nd nd nd nd nd 41.4

c, 24 C (mN/m) 31.0 (0.1) 30.8 (0.1) 30.9 (0.1) 30.5 (0.1) 31.0 (0.1) 30.4 (0.1) 27.3 (0.1)

c, 40 C (mN/m) 29.5 (0.1) 29.3 (0.1) 29.4 (0.1) 29.0 (0.1) 29.5 (0.1) 29.1 (0.1) 25.9 (0.1)

a CSME: camelina oil methyl esters; CSEE: camelina oil ethyl esters; CME: canola oil methyl esters; PME: palm oil methyl esters; SME: soybean oil methyl esters; SEE:

soybean oil ethyl esters, ULSD: ultra low-sulfur diesel fuel.

b Values in parentheses are standard deviations from the reported means.

c nd = not determined.

B.R. Moser, S.F. Vaughn / Bioresource Technology 101 (2010) 646–653 649
soybean (5.0 h) oils were more stable to oxidation than CSME and

CSEE as a result of the high trienoic fatty acid content of camelina

oil (33.4 wt.%; Table 3). The rate of autoxidation is dependant on

the number and location of methylene-interrupted double bonds

contained within fatty acid alkyl esters that comprise biodiesel.

Polyunsaturated materials, especially trienoic constituents, are

particularly vulnerable to autoxidation, as evidenced by the relative rates of oxidation of the unsaturates: 1 for ethyl oleate, 41

for ethyl linoleate, and 98 for ethyl linolenate (Holman and Elmer,

1947). In addition, the OSI values of methyl esters of oleic, linoleic,

and linolenic acids were reported as 2.5, 1.0, and 0.2 h, respectively

(Moser, 2009b). The combined trienoic fatty acid contents of canola, palm, and soybean oils were 7.6, 0.1, and 7.7 wt.%, respectively

(Table 3). Palm oil methyl esters were especially resistant to oxidation as a result of their high saturated (48.2 wt.%) and low polyunsaturated (10.4 wt.%) fatty ester composition. Both CSME and CSEE

were unsatisfactory according to oxidative stability specifications

(Table 1) contained within ASTM D6751 (OSI >3 h) and EN 14214

(OSI > 6 h). Accordingly, addition of antioxidant additives (Moser,

2008b) or blending with more oxidatively stable feedstocks (Moser, 2008a) would be necessary to yield satisfactory oxidative stability from esters of camelina oil.

The relatively high polyunsaturated fatty acid content of CSME

and CSEE resulted in IVs of 151 and 144, respectively (Table 4).

Although ASTM D6751 does not contain an IV specification, EN

14214 limits IV to a maximum value of 120 (Table 1). Consequently, CSME and CSEE, along with SME (IV 134) and SEE (IV

127) were unsatisfactory according to EN 14214. In order for camelina oil to be acceptable as a feedstock with regard to IV in locations where the EN 14214 standard is applied, blending with

feedstocks that contain a greater percentage of saturated fatty

acids would be necessary (Moser, 2008a).

The kinematic viscosities (40 C) of CSME and CSEE were 4.15

and 4.48 mm2

/s (Table 4), which were satisfactory according to

ASTM D6751 (1.9–6.0 mm2

/s; Table 1) and EN 14214 (3.5–

5.0 mm2

/s; Table 1). Among the methyl esters, an inverse relationship was elucidated between kinematic viscosity and polyunsaturated FAME content: PME (most viscous; lowest polyunsaturated

ester content) > CME > CSME > SME (least viscous; highest polyunsaturated content). This was expected, as it is known that increasing levels of unsaturation result in lower kinematic viscosities. For

example, the reported kinematic viscosities (40 C) of methyl esters of stearic, oleic, linoleic, and linolenic acids were 5.85, 4.51,

3.65, and 3.14 mm2

/s, respectively (Knothe and Steidley, 2005a).

As anticipated, the kinematic viscosities of the ethyl esters (CSEE

and SEE) were higher than the corresponding methyl esters (CSME

and SME).

The DCN of CSME was above the minimum limits of 47 and 51

specified in ASTM D6751 and EN 14214, respectively, with a value

of 52.8 (Table 4). For comparison, a previous study reported the

DCN of SME as 54.0 (Knothe et al., 2006). Results generated by

ASTM D6890 (DCN) generally correlate with CN determination by

ATSM D613. The ASTM D6890 method is approved as an alternative to the more traditional CN method (ASTM D613) specified in

ASTM D6751.

The sulfur contents of CSME and CSEEE were 3 ppm (Table 4),

which were satisfactory according to the specified maximum

allowable limits in ASTM D6751 and EN 14214 of 15 and

10 ppm, respectively. SME was essentially free of sulfur (1 ppm),

along with CME (2 ppm) and PME (2 ppm). In addition, phosphorous content is limited in ASTM D6751 and EN 14214 to a maximum value of 0.001 mass%. None of the methyl esters contained

phosphorous (Table 4).

The lubricities (60 C) of CSME and CSEE were essentially indistinguishable from esters prepared from other oils (Table 4).

Although lubricity is not specified in ASTM D6751 or EN 14214,

it is nonetheless an important fuel property. Fuels with poor

lubricity can cause failure of diesel engine parts that rely on lubrication from fuels, such as fuel pumps and injectors (Knothe et al.,

2005; Knothe and Steidley, 2005b). As such, lubricity specifications

are included in petrodiesel standards in the United States (ASTM

D975; <520 lm by ASTM D6079; Table 1) and Europe (EN 590;

<460 lm). As expected, all alkyl esters were considerably below

these maximum allowable limits, which was in agreement with

previous studies that indicated biodiesel possessed inherently

good lubricity (Knothe and Steidley, 2005b; Moser et al., 2008;

Jham et al., 2009; Moser et al., 2009a). The wear scar generated

by CSME (122 lm; Table 4) was significantly shorter than the corresponding scars for CME (169 lm), PME (172 lm), SME (135 lm),

and SEE (137 lm), which was not surprising since increasing levels

of unsaturation result in superior lubricity (shorter wear scars). For

example, the reported wear scars produced by methyl esters of

stearic, oleic, linoleic, and linolenic acids were 322, 290, 236, and

183 lm, respectively (Knothe and Steidley, 2005b). As previously

stated, CSME and CSEE contained high percentages of in trienoic

methyl esters (C18:3 and C20:3).

Although surface tension is not specified in either ASTM D6751

or EN 14214, it is nevertheless an important fuel property that affects atomization in combustion chambers in compression–ignition (diesel) engines (Ejim et al., 2007). The surface tensions at

24 C and 40 C of CSME (31.0 and 29.5 mN/m) and CSEE (30.8

and 29.3 mN/m) were similar to SME and slightly higher than

CME and PME (Table 4). Both CSME/EE and SME/EE contained higher polyunsaturated fatty ester content (see Table 3) than CME and

PME. Increasing levels of unsaturation were reported to increase

surface tension (Doll et al., 2007). Additionally, longer chain

lengths among otherwise similar molecules are reported to increase surface tension (Allen et al., 1999), which further explained

why CSME and CSEE had higher surface tensions than CME and

PME. Although CSME/EE had slightly higher surface tensions than

CME, SME/EE, and PME, it is expected that the differences are not

significant enough to negatively influence fuel atomization.

3.4. Evaluation of camelina oil alkyl esters as blend components in

ULSD

Because biodiesel is completely miscible with ULSD, it can be

used as a blend component in any proportion in ULSD. However,

ASTM D975 and D7467 allow up to 5 and 20 vol.% biodiesel (Table

1), respectively. The European petrodiesel standard, EN 590, allows

for up to 5 vol.% biodiesel as well. Biodiesel and ULSD are not

chemically similar: biodiesel is composed of long-chain fatty acid

alkyl esters whereas ULSD is a complex mixture of aliphatic and

aromatic hydrocarbons (12 or more carbons) that distill from crude

petroleum oil in a similar temperature range (250–350 C). Fuel

properties determined in the current study that were affected by

blending included lubricity, oxidative stability, low temperature

operability, kinematic viscosity, and surface tension. Other properties influenced by blending include exhaust emissions, flash point,

sulfur content, and cetane number. As seen in Table 4, neat ULSD

exhibited a DCN of 41.4, which was satisfactory according to ASTM

D975 but significantly below the value obtained for CSME. The sulfur content of ULSD was acceptable with regard to ASTM D975

with a value of 8 ppm. Blending CSME with ULSD resulted in a

small reduction in sulfur content, as evidenced by values of 8, 8,

7, and 7 ppm for the B2, B5, B10, and B20 blends. The results for

DCN and sulfur content of ULSD were in agreement with a previous

study (Moser et al., 2009b). Flash point and exhaust emissions

were not measured because biodiesel is reported to be superior

to petrodiesel with regard to these properties (Mittelbach and

Remschmidt, 2004; Knothe et al., 2005). Furthermore, most regulated exhaust emissions (except for NOx) of petrodiesel are

650 B.R. Moser, S.F. Vaughn / Bioresource Technology 101 (2010) 646–653
reduced upon blending with biodiesel (McCormick et al., 2006;

Moser et al., 2009b).

Biodiesel was considerably less stable to oxidation than ULSD,

as evidenced by an OSI value of greater than 24 h for ULSD (Table

5). Consequently, blends of CSME, CSEE, SME, and SEE exhibited

progressively lower OSI values as the percentage of biodiesel was

increased from 0 to 20 vol.% (Table 5). Comparison at the B20 level

revealed that the CSME/EE blends were less stable to oxidation

than the SME/EE blends, which was consistent with the results obtained for neat methyl and ethyl esters discussed in Section 3.3.

The petrodiesel–biodiesel blend standard, ASTM D7467 (Table 1),

which covers B6 to B20 blends, specifies a minimum OSI value of

6.0 h. As seen in Table 5, the B20 blend of CSEE failed to meet this

requirement (5.8 h). Accordingly, employment of antioxidant additives would be required in the case of B20 CSEE-petrodiesel blends.

The petrodiesel standard, ASTM D975 (Table 1) does not contain an

oxidative stability specification. As indicated in Table 5, all B2 and

B5 blends of CSME/EE and SME/EE, with the exception of B5 CSEE,

exhibited OSI values greater than 24 h.

Biodiesel is generally inferior to ULSD with regard to low temperature operability (Moser et al., 2008, 2009b). Illustrative of this

is a comparison of neat ULSD (CP 18 C; PP 23 C; CFPP 18 C;

Table 5) to the neat biodiesel fuels listed in Table 4. Consequently,

blends of CSME, CSEE, SME, and SEE in ULSD displayed progressively higher CP, PP, and CFPP values as the percentage of biodiesel

was increased from 0 to 20 vol.% (Table 5). Taking into consideration standard deviation, the behavior at each blend level among

CSME, CSEE, SME, and SEE blends did not vary significantly. For

example, the CFPP of B5 blends with CSME, CSEE, SME, and SEE

were 15, 16, 17, and 16 C, respectively. Neither ASTM

D975 nor D7467 specify limits on low temperature operability. Instead, only guidance is provided.

Petrodiesel is less viscous than biodiesel, as evidenced by the

kinematic viscosity (40 C) of ULSD (2.30 mm2

/s; Table 5) versus

the biodiesel fuels (Table 4). As a result, blends of CSME, CSEE,

SME, and SEE in ULSD afforded progressively higher kinematic viscosities as the percentage of biodiesel was increased from 0 to

20 vol.% (Table 5). This result was in agreement with previous reports that examined the kinematic viscosities of SME and PME

blends in ULSD (Moser et al., 2008) and SME blends in low-sulfur

diesel fuel (<500 ppm S) (Doll et al., 2008). The behavior at each

blend level among the CSME, CSEE, SME, and SEE blends did not

vary significantly with regard to viscosity. For example, the kinematic viscosities of the B5 blends of CSME, CSEE, SME, and SEE

were 2.38, 2.38, 2.37, and 2.38 mm2

/s, respectively. All of the

blends exhibited kinematic viscosities that were satisfactory

according to the petrodiesel (ASTM D975) and petrodiesel–biodiesel blend (ASTM D7467) standards, which both specify a range

from 1.9–4.1 mm2

/s (Table 1).

As previously stated, petrodiesel (untreated with lubricityenhancing additives) was inferior to biodiesel with regard to

lubricity. In fact, the wear scar generated by ULSD (571 lm; Table

5) was significantly longer than biodiesel (<173 lm; Table 4) and

in excess of the maximum allowable wear scar lengths specified

in ASTM D6751 and D7467 (Table 1; <520 lm) and EN 590

(<460 lm). Accordingly, blends of CSME, CSEE, SME, and SEE in

ULSD exhibited progressively better lubricities (shorter wear scars)

as the percentage of biodiesel was increased from 0 to 20 vol.% (Table 5). In fact, even at the B2 blend level, CSME/EE and SME/EE

blends were satisfactory according to the aforementioned petrodiesel standard (ASTM D975), providing wear scars below

275 lm in all cases. Blends equal to or greater than the B5 blend

level afforded wear scars below 200 lm (Table 5). These results

were in agreement with a previous report that examined the

lubricity behavior of SME and PME blends in ULSD from 0.1 to

20 vol.% (Moser et al., 2008). Taking into consideration standard

deviation, the lubricity behavior at each blend level among the

CSME, CSEE, SME, and SEE blends did not vary significantly. For

example, the wear scars generated by the B10 blends of CSME,

CSEE, SME, and SEE were 142, 169, 154, and 159 lm, respectively.

The surface tension of ULSD at 24 and 40 C (27.3 and 25.9 mN/

m; Table 5) was superior (lower value) to biodiesel (>29 mN/m; Table 4). Accordingly, blends of CSME, CSEE, SME, and SEE in ULSD

exhibited progressively higher surface tensions as the percentage

of biodiesel was increased from 0 to 20 vol.% (Table 5), which

was in agreement with a previous study (Doll et al., 2008). However, as the percentage of CSME, for example, in ULSD was increased from B2 (27.4 mN/m at 24 C) to B20 (27.8 mN/m at

Table 5

Oxidative stability (OSI, h), low temperature operability (CP, PP, CFPP, C), kinematic viscosity (mm2

/s, 40 C), lubricity (Lub, 60 C), and surface tension (c, mN/m, 24 C and 40 C)

of camelina and soybean oil methyl and ethyl esters blended with ultra low-sulfur diesel fuel.

Vol.% OSI(h) CP(C) PP(C) CFPP(C) t(mm2/s) Lub(lm) c, 24 C(mN/m) c, 40 C(mN/m)

0 >24 18 (1)a 23 (1) 17 (1) 2.30 (0.01) 571 (5) 27.3 (0.1) 25.9 (0.1)

Camelina oil methyl esters

2 >24 16 (1) 23 (1) 17 (1) 2.33 (0.01) 248 (8) 27.4 (0.1) 26.1 (0.1)

5 >24 14 (1) 23 (1) 15 (1) 2.38 (0.01) 147 (5) 27.5 (0.1) 26.0 (0.1)

10 16.6 (0.1) 13 (1) 22 (1) 15 (1) 2.42 (0.01) 142 (7) 27.6 (0.1) 26.2 (0.1)

20 8.9 (0.1) 11 (1) 20 (1) 14 (1) 2.58 (0.01) 136 (6) 27.8 (0.1) 26.5 (0.1)

Camelina oil ethyl esters

2 >24 15 (1) 23 (1) 17 (1) 2.33 (0.01) 260 (6) 27.4 (0.1) 26.0 (0.1)

5 17.8 (1.1) 14 (1) 23 (1) 16 (1) 2.38 (0.01) 182 (3) 27.4 (0.1) 26.1 (0.1)

10 9.1 (0.3) 13 (1) 22 (1) 15 (1) 2.48 (0.01) 169 (8) 27.5 (0.1) 26.2 (0.1)

20 5.8 (0.3) 11 (1) 20 (1) 14 (1) 2.69 (0.02) 154 (5) 27.8 (0.1) 26.4 (0.1)

Soybean oil methyl esters

2 >24 18 (1) 22 (1) 17 (1) 2.31 (0.01) 271 (7) 27.4 (0.1) 26.0 (0.1)

5 >24 16 (1) 22 (1) 17 (1) 2.37 (0.01) 198 (4) 27.4 (0.1) 26.0 (0.1)

10 >24 14 (1) 21 (1) 17 (1) 2.41 (0.01) 154 (3) 27.6 (0.1) 26.1 (0.1)

20 17.1 (0.2) 12 (1) 17 (1) 16 (1) 2.54 (0.01) 143 (4) 27.8 (0.1) 26.4 (0.1)

Soybean oil ethyl esters

2 >24 15 (1) 22 (1) 16 (1) 2.31 (0.01) 262 (6) 26.0 (0.1) 25.9 (0.1)

5 >24 15 (1) 22 (1) 16 (1) 2.38 (0.01) 191 (5) 27.4 (0.1) 26.1 (0.1)

10 19.5 (0.4) 14 (1) 22 (1) 13 (1) 2.47 (0.01) 159 (4) 27.5 (0.1) 26.2 (0.1)

20 13.1 (0.2) 13 (1) 17 (1) 11 (1) 2.61 (0.01) 149 (5) 27.7 (0.1) 26.4 (0.1)

a Values in parentheses are standard deviations from the reported means.

B.R. Moser, S.F. Vaughn / Bioresource Technology 101 (2010) 646–653 651
24 C), a minimal increase in surface tension was noticed. Taking

into consideration standard deviation, the surface tension behavior

at each blend level among CSME, CSEE, SME, and SEE blends did not

vary significantly. For example, the surface tensions (24 C) of the

B10 blends with CSME, CSEE, SME, and SEE were 27.6, 27.5, 27.6,

and 27.5 mN/m, respectively. The minimal increase in surface tension among the blends in comparison to neat ULSD was not considered substantial enough to negatively impact fuel atomization.

4. Conclusions

Camelina oil, which was obtained in 30.5 wt.% from dried seeds,

contained a high percentage of polyunsaturated fatty acids

(54.3 wt.%), as indicated by its linolenic (32.6 wt.%) and linoleic

(19.6 wt.%) acid contents. Other fatty acids identified in camelina

oil included oleic (18.6 wt.%), gondoic (12.4 wt.%), palmitic

(6.8 wt.%), stearic (2.7 wt.%), and erucic (2.3 wt.%) acids, with lesser

amounts of other constituents also detected.

Methyl and ethyl esters were prepared in moderately high

yields (89 and 84 wt.%, respectively) from camelina oil by homogenous base-catalyzed transesterification. The AV of crude camelina

oil (2.06 mg KOH/g) was attributed to non-quantitative alkyl ester

yields.

The oxidative stability of biodiesel prepared from camelina oil

was unsatisfactory according to ASTM D6751 and EN 14214 as a

result of its high polyunsaturated fatty acid content. The high IVs

of CSME and CSEE were also in excess of the limit contained in

EN 14214. The low temperature operability of CSME and CSEE

was similar to biodiesel prepared from canola and soybean oils,

and superior to PME. The kinematic viscosity, AV, DCN, lubricity,

sulfur and phosphorous contents, as well as the surface tensions

of CSME and CSEE were satisfactory according to ASTM D6751

and EN 14214, where applicable.

Evaluation of CSME and CSEE as blend components in ULSD revealed that blends at the B20 level were not satisfactory with regard to the oxidative stability specification contained within

ASTM D7467. Otherwise, camelina-ULSD blends were indistinguishable from soybean-ULSD blends with regard to low temperature performance, kinematic viscosity, lubricity, and surface

tension. Camelina oil alkyl esters, like soybean oil alkyl esters,

may be used as lubricity-enhancing additives in petrodiesel.

In summary, CSME and CSEE are acceptable as biodiesel fuels

provided that antioxidant additives are employed. Overall, the

properties of camelina oil alkyl esters, both neat and blended with

petrodiesel, were similar to other commonly encountered biodiesel

fuels, such as soybean, canola, and palm oil methyl esters.

Acknowledgements

The authors acknowledge Benetria N. Banks, Ray K. Holloway,

Erin L. Walter, and Jennifer R. Koch for excellent technical

assistance.

References

Allen, C.A.W., Watts, K.C., Ackman, R.G., 1999. Predicting the surface tension of

biodiesel fuels from their fatty acid composition. J. Am. Oil Chem. Soc. 76, 317–

323.

ASTM, 2008a. Standard specification for diesel fuel oils. In: Annual Book of ASTM

Standards, ASTM International, West Conshohocken, Method D975-08a.

ASTM, 2008b. Standard specification for diesel fuel oil, biodiesel blend (B6 to B20).

In: Annual Book of ASTM Standards, ASTM International, West Conshohocken,

Method D7467-08a.

ASTM, 2008c. Standard specification for biodiesel fuel (B100) blend stock for

distillate fuels. In: Annual Book of ASTM Standards, ASTM International, West

Conshohocken, Method D6751-08a.

Bernardo, A., Howard-Hildige, R., O’Connell, A., Nichol, R., Ryan, J., Rice, B., Roche, E.,

Leahy, J.J., 2003. Camelina oil as a fuel for diesel transport engines. Ind. Crops

Prod. 17, 191–197.

Budin, J.T., Breene, W.M., Putnam, D.H., 1995. Some compositional properties of

Camelina (Camelina sativa L. Crantz) seeds and oils. J. Am. Oil Chem. Soc. 72,

309–315.

Committee for Standardization, 2003. Automotive Fuels – Fatty Acid Methyl Esters

(FAME) for Diesel Engines – Requirements and Test Methods. European

Committee for Standardization, Brussels, Method EN 14214:2003.

Committee for Standardization, 2004. Automotive Fuels – Diesel – Requirements

and Test Methods. European Committee for Standardization, Brussels, Method

EN 590:2004.

Doll, K.M., Moser, B.R., Erhan, S.Z., 2007. Surface tension studies of alkyl esters and

epoxidized alkyl esters relevant to oleochemically based fuel additives. Energy

Fuels 21, 3044–3048.

Doll, K.M., Sharma, B.K., Suarez, P.A.Z., Erhan, S.Z., 2008. Comparing biofuels

obtained from pyrolysis, of soybean oil or soapstock, with traditional soybean

biodiesel: density, kinematic viscosity, and surface tensions. Energy Fuels 22,

2061–2066.

Ejim, C.E., Fleck, B.A., Amirfazli, A., 2007. Analytical study for atomization of

biodiesels and their blends in a typical injector: surface tension and viscosity

effects. Fuel 86, 1534–1544.

Freedman, B., Pryde, E.H., Mounts, T.L., 1984. Variables affecting the yields of fatty

esters from transesterified vegetable oils. J. Am. Oil Chem. Soc. 61, 1638–1643.

Frohlich, A., Rice, B., 2005. Evaluation of Camelina sativa oil as a feedstock for

biodiesel production. Ind. Crops Prod. 21, 25–31.

Holman, R.A., Elmer, O.C., 1947. The rates of oxidation of unsaturated fatty acids and

esters. J. Am. Oil Chem. Soc. 24, 127–129.

Jham, G.N., Moser, B.R., Shah, S.N., Holser, R.A., Dhingra, O.D., Vaughn, S.F., Berhow,

M.A., Winkler-Moser, J.K., Isbell, T.A., Holloway, R.K., Walter, E.L., Natalino, R.,

Anderson, J.C., Stelly, D.M., 2009. Wild Brazilian mustard (Brassica juncea L.)

seed oil methyl esters as biodiesel fuel. J. Am. Oil Chem. Soc. 86, 917–926.

Knothe, G., Steidley, K.R., 2005a. Kinematic viscosity of biodiesel fuel components

and related compounds. Influence of compound structure and comparison to

petrodiesel fuel components. Fuel 84, 1059–1065.

Knothe, G., Steidley, K.R., 2005b. Lubricity of components of biodiesel and

petrodiesel. The origin of biodiesel lubricity. Energy Fuels 19, 1192–1200.

Knothe, G., Van Gerpen, J., Krahl, J., 2005. The Biodiesel Handbook. AOCS Press,

Urbana.

Knothe, G., Sharp, C.A., Ryan III, T.W., 2006. Exhaust emissions of biodiesel,

petrodiesel, neat methyl esters, and alkanes in a new technology engine. Energy

Fuels 20, 403–408.

Krist, S., Stuebiger, G., Bail, S., Unterweger, H., 2006. Analysis of volatile compounds

and triacylglycerol composition of fatty seed oil gained from flax and false flax.

Eur. J. Lipid Sci. Technol. 108, 48–60.

Leonard, E.C., 1998. Camelina oil: a-linolenic source. Inform 9, 830–838.

Lotero, E., Liu, Y., Lopez, D.E., Suwannakarn, K., Bruce, D.A., Goodwin Jr., J.G., 2005.

Synthesis of biodiesel via acid catalysis. Ind. Eng. Chem. Res. 44, 5353–

5363.

McCormick, R.L., Williams, A., Ireland, J., Brimhall, M., Hayes, R.R., 2006. Effects of

Biodiesel Blends on Vehicle Emissions. Fiscal Year 2006 Annual Operating Plan

Milestone 10.4, NREL Milestone Report 540-40554. <http://www.nrel.gov/docs/

fy07osti/40554.pdf>. (accessed 8.10.09).

Mittelbach, M., Remschmidt, C., 2004. Biodiesel – A Comprehensive Handbook.

Martin Mittelbach, Graz.

Moser, B.R., 2008a. Influence of blending canola, palm, soybean, and sunflower oil

methyl esters on fuel properties of biodiesel. Energy Fuels 22, 4301–4306.

Moser, B.R., 2008b. Efficacy of myricetin as an antioxidant additive in methyl esters

of soybean oil. Eur. J. Lipid Sci. Technol. 110, 1167–1174.

Moser, B.R., 2009a. Biodiesel production, properties, and feedstocks. In vitro Cell.

Dev. Biol.-Plant 45, 229–266.

Moser, B.R., 2009b. Comparative oxidative stability of fatty acid alkyl esters by

accelerated methods. J. Am. Oil Chem. Soc. 86, 699–706.

Moser, B.R., Cermak, S.C., Isbell, T.A., 2008. Evaluation of castor and lesquerella oil

derivatives as additives in biodiesel and ultra low sulfur diesel fuels. Energy

Fuels 22, 1349–1352.

Moser, B.R., Knothe, G., Vaughn, S.F., Isbell, T.A., 2009a. Production and evaluation of

biodiesel from field pennycress (Thlaspi arvense L.) oil. Energy Fuels 23, 4149–

4155.

Moser, B.R., Williams, A., Haas, M.J., McCormick, R.L., 2009b. Exhaust emissions

and fuel properties of partially hydrogenated soybean oil methyl esters

blended with ultra low sulfur diesel fuel. Fuel Process. Technol. 90, 1122–

1128.

Ni Eidhin, D., Burke, J., O’Beirne, D., 2003. Oxidative stability of x3-rich camelina oil

and camelina oil-based spread compared with plant and fish oils and sunflower

spread. J. Food Sci. 68, 345–353.

Paulson, N.D., Ginder, R.G., 2007. Working Paper 07-WP 448, Center for Agricultural

and Rural Development, Iowa State University, May.

Putnam, D.H., Budin, J.T., Field, L.A., Breene, W.M., 1993. Camelina: a promising low

input oilseed. In: Janick, J., Simon, J. (Eds.), New Crops. John Wiley and Sons,

New York, pp. 314–322.

Rashid, U., Anwar, F., Moser, B.R., Knothe, G., 2008. Moringa oleifera oil: a possible

source of biodiesel. Bioresour. Technol. 99, 8175–8179.

Retka-Schill, S., 2008a. Walking a tightrope. Biodiesel Mag. 5 (3), 64–70.

Retka-Schill, S., 2008b. Oilseed comes of age. Biodiesel Mag. 5 (11), 44–49.

Sawyer, K., 2008. Is there room for camelina? Biodiesel Mag. 5 (7), 83–87.

Steinke, G., Kirchhoff, R., Mukherjee, K.D., 2000a. Lipase-catalyzed alcoholysis of

crambe and camelina oil for the preparation of long-chain esters. J. Am. Oil

Chem. Soc. 77, 361–366.

652 B.R. Moser, S.F. Vaughn / Bioresource Technology 101 (2010) 646–653
Steinke, G., Schonwiese, S., Mukherjee, K.D., 2000b. Alkali-catalyzed alcoholysis of

crambe oil and camelina oil for the preparation of long-chain esters. J. Am. Oil

Chem. Soc. 77, 367–371.

Steinke, G., Weitkamp, P., Klein, E., Mukherjee, K.D., 2001. High-yield preparation of

wax esters via lipase-catalyzed esterification using fatty acids and alcohols from

crambe and camelina oils. J. Agric. Food Chem. 49, 647–651.

Tiwari, A.K., Kumar, A., Raheman, H., 2007. Biodiesel production from jatropha oil

(Jatropha curcas) with high free fatty acids: an optimized process. Biomass

Bioenerg. 31, 569–575.

B.R. Moser, S.F. Vaughn / Bioresource Technology 101 (2010) 646–653 653