Potential of plants showing Renewable Energy from it.

1. Potential of five plants growing on unproductive agricultural lands as biodiesel
resources
Cheng-Jiang Ruan a,*, Wei-He Xing a
, Jaime A. Teixeira da Silva b
a
Key Laboratory of Biotechnology & Resources Utilization, Dalian Nationalities University, Dalian 116600, China
b
Faculty of Agriculture and Graduate School of Agriculture, Kagawa University, Miki-cho, Kagawa 761-0795, Japan
a r t i c l e i n f o
Article history:
Received 10 December 2010
Accepted 23 October 2011
Available online 10 November 2011
Keywords:
Biodiesel
Energy plants
Unproductive agricultural lands
Seed oil content
Cetane number
C18 fatty acid
a b s t r a c t
Fossil fuels are being heavily depleted due to increasing anthropogenic activities worldwide, and burning
them contributes to global climate warming and air pollution. Vegetable oils are one of the main
feedstocks for biodiesel: they are non-toxic and environmentally friendly. Rising global population,
decreasing arable lands and a decline in crop yields from desertification and salinization demands that
biodiesel feedstock be grown on unproductive agricultural lands. To estimate whether five plants
growing on such land in China could be used as energy plants, we determined their seed oil content
(SOC) and relative fatty acid content, and estimated the cetane number (CN) of the biodiesel produced
from these plant oils by a fitted regression between different C18 fatty acids and CN. Results showed that
four plants can be developed as energy plants, including Datura candida (SOC ¼ 22.9%, CN ¼ 50.8),
Xanthium sibiricum (SOC ¼ 41.9%, CN ¼ 46.5), Kosteletzkya pentacarpos (SOC ¼ 18.6%, CN ¼ 45.9) and
Hibiscus trionum (SOC ¼ 17.5%, CN ¼ 46.9). The fifth plant, Rhus typhina, was not adapted as an energy
plant because of its low SOC, 9.7%. Our data provide a scientific basis for growing energy plants in
unproductive agricultural lands as biodiesel resources.
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
Fossil fuels (coal, crude oil and natural gas) are currently the
primary source of cheap energy that powers our modern industrial
civilization. However, they are being heavily depleted due to
increasing anthropogenic activities worldwide, and burning them
contributes to global climate warming and air pollution [1]. The
depletion of fossil fuels spurs the need to develop renewable fuel
sources (wind, solar and biofuels). Biodiesel is a fuel comprising
mono-alkyl esters of medium to long-chain fatty acids derived from
vegetable oils or animal fats [2e4]. As a renewable alternative to
diesel fuel, biodiesel is oxygenated, biodegradable, non-toxic, and
environmentally friendly [4]. Its utilization significantly reduces
greenhouse gas emissions and toxic air pollutants [5]. This is
because biodiesel (1) reduces the net gain in CO2 emissions by 78%
compared to petroleum fuel and the tailpipe emissions of partic-
ulate matter (soot or black carbon) by 47% which is fast becoming
recognized as a major contributor to global warming as well as
a critical air pollutant associated with reduced human health,
particularly among children and asthmatics; and (2) contains no
sulfur and generates no sulfur emissions, a major source of acidi-
fication in rain and surface water [6].
Biodiesel production and its use has increased significantly in
many countries around the world, including the United States,
Austria, France, Germany, Japan, Italy, Brazil, China, and Malaysia
and it is in a nascent status in many others. For example, Peplow [7]
found a way to create fuel from the carbohydrates that make up
about 75% of a plant’s dried weight. Crop production needs to be
increased to meet a rising global population (expected to be 9.3
billion by 2050 [8]), but the yield of conventional crops decreases as
fertile soils become salinized [9,10]. However, most vegetable oils
such as soybean, peanut, rapeseed and cotton seed oils are edible
[11,12], and if they were to be used to produce biodiesel fuel, this
would conflict with limited oil or food resources for a rising global
population. Every year, an important portion of agricultural utilized
areas is lost as a consequence of desertification and salinization
[9,13], because adding to the increasing competition for limited
fresh water is the gradual and irreversible spread of salinization
[14]. In addition, a continuous rise in sea-level in a warming world
threatens increased salinity in coastal lowlands, such as Ches-
apeake Bay [15] and a 2000 km2
area of seawater encroachment
only in two provinces of Shandong and Liaoning, China [16]. Hence,
considering that domestic food and plant oil production currently
are insufficient to feed the 6.5 billion people in the world due to
* Corresponding author. Tel.: þ86 411 87656015; fax: þ86 411 87618179.
E-mail address: ruancj@yahoo.com.cn (C.-J. Ruan).
Contents lists available at SciVerse ScienceDirect
Renewable Energy
journal homepage: www.elsevier.com/locate/renene
0960-1481/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.renene.2011.10.022
Renewable Energy 41 (2012) 191e199

2. limited agricultural lands, ultimately ways are needed to grow
biodiesel feedstock on unproductive agricultural lands such as
saline-alkaline lands, poor soil, deserted soils, and plough-
withdrawn lands that have not been forested or farmed or are
not adapted for food production because of too low yield.
The fuel properties of biodiesel, for example cetane number,
oxidative stability, cloud point, pour point, viscosity, density, and
heating value are directly related to the fatty acid profile of the
original source material [4]. These relationships can be used for
combustion modeling [17e19]. The cetane number, a widely used
diesel fuel quality parameter related to the ignition delay time (and
combustion quality) of a fuel, has been applied to alternative diesel
fuels such as biodiesel and its components [20]. The higher the
cetane number of a given compound, the shorter its ignition delay
time and vice versa [20]. Fatty acids of C18 chain length as well as
their methyl, ethyl, n-propyl and n-butyl esters were injected into
a constant-volume combustion apparatus to form the precombus-
tion phase of an ignition event, in which compound structure plays
a significant role in determining the cetane number of a given
material: more highly saturated fatty compounds have a higher
cetane number [21] while the more unsaturated C18 fatty
compounds have a relatively low cetane number [20]. Higher
cetane numbers are correlated with reduced nitrogen oxide (NOx)
exhaust emissions [22]; the environmental significance of reducing
NOx exhaust emissions is that these exhaust emissions are
precursors of ozone (O3), which is a primary component of urban
smog. NOx emissions are regulated in tailpipe emissions, while O3 is
regulated in ambient air [22]. Reducing exhaust emissions is an
important problem facing biodiesel as both these gas species are
slightly increased when using biodiesel in comparison to petro-
diesel fuel [23]. Hence, the cetane number can be used as
a parameter to evaluate the potential of plant oils as biodiesel.
Five plants (Table 1), which normally grow on unproductive
agricultural lands (e.g. coastal tideland, roadsides, desert and dry
regions), are potential resources as biodiesel feedstocks, including
Rhus typhina (Fig. 1A) [24,25], Kosteletzkya pentacarpos [26] (Fig. 1B
and C), Xanthium sibiricum (Fig. 1D) [27], Datura candida (Fig. 1E)
and Hibiscus trionum (Fig. 1F).
In this study, we have (i) measured seed oil content (SOC) and its
relative fatty acid content for each of the five plants, (ii) fit
a regression between the relative contents of different C18 fatty
acids and the cetane numbers of the biodiesel produced from
different plant oils by the published data, (iii) estimated the cetane
numbers of the biodiesel produced from the five plant oils in this
study by the above regression, and (iv) evaluated the potential of
the five plants as biodiesel resources, according to the seed oil
content (SOC) and the estimated cetane number.
2. Material and methods
2.1. Plant materials
Seeds were collected from the five plants growing on ecologi-
cally disturbed or unproductive agricultural lands: (i) R. typhina
grew on the roadsides of Wafangdian county, Liaoning province,
China; (ii) K. pentacarpos, X. sibiricum, D. candida and H. trionum
grew in fields located in the tideland of Dalian city, Liaoning
province, China. Only clean seeds, without any kind of infection or
animal damage, were collected.
2.2. SOC and relative contents of fatty acid
Seed samples of each plant field were mixed (2 kg), packed into
plastic containers (600e700 g/container), freeze-dried, and stored
at À20 C. Acid-washed containers were used for those samples
meant for analysis of the oil and relative fatty acid contents. Before
every analysis the contents of 1e3 containers were homogenized.
All the samples were analyzed in triplicate.
Oil content was measured according to AOAC [28]. Fatty acids
were measured by the normalization method of GC-FID (Gas
Chromatography - Flame Ionization Detector). A 0.2 g sample was
added to a 20 ml test tube with a cork. Then, 0.5 mol/l NaOH (2 ml)
was added to 2 ml methanol, and the resulting mixture was boiled
at 60 C for 25 min. After cooling, 35% BF3eCH3OH (2 ml) was added
and the mixture was boiled at 60 C for 20 min in closed containers.
After cooling, 2-ml 99.9% hexane was added. After shaking, 2 ml
saturated NaCl was added. After being shaken and centrifuged, the
supernatant was transferred into a clean test tube and 2e4 drops
anhydrous sodium sulfate was added to eliminate minimum water.
The experiment was performed with a Shimadzu GC-14B gas
chromatograph equipped with a flame ionization detector (FID),
with an acidified polyethylene glycol capillary column OV-17
(30 m  0.32 mm  1.0 mm film thickness). The initial isotherm
of 150 C (1 min) was raised to 230 C at a rate of 5 C/min, and the
final isotherm was 230 C (10 min); carrier gas was nitrogen; split
ratio was 30:1. The relative contents of the different fatty acids were
determined by using the area normalization method.
2.3. Estimation of the cetane numbers of the biodiesel produced
from the five plant oils
Relative contents of the main components of fatty acid can be
used to directly determine the cetane number [20,29]. We surveyed
70 samples of relative contents of C18:0, C18:1, C18:2 and C18:3 and
the cetane number of biodiesel from our studies and published data
Table 1
Five plants used in this study.
Species Growth habit Ecological distribution Potential as biodiesel References
R. typhina Open and irregular, flat-topped crown,
spreads by suckering
Adapts to dry, poor, soils; best in well
drained sites and roadsides in full sun.
Eastern United States and adjacent
Canada; being widely planted in China
Seed and fruit oil [24]
K. pentacarpos Perennial herb, 80e150 cm height,
flowering period of Jul.eSep., fruit in Jul.eOct.
Seaside bogs of the Caspian littoral,
along the west and south coasts
Seed oil [26]
X. sibiricum Annual herb, 30e90 cm height, flowering
period of Jul.eOct., fruit in Aug.eNov.
Wasteland, barrenland, uncultivated
land, slope, naturally distributes in Eurasia
Seed oil In this study
H. trionum Herbs annual, erect or procumbent,
25e70 cm tall, flowering period of
MayeOct., fruit in Jun.eOct.
Ruderal weed. Throughout China
[Kazakhstan, Kyrgyzstan, Mongolia,
Tajikistan, Uzbekistan; Pantropical]
Seed oil In this study
D. candida Annual herb growing into a bush up
to 2.5 m high, with white to creamy
or violet flowers. The egg-shaped seed
capsule is walnut-sized and either
covered with spines or bald
Often found as a weed on wastelands
and in garbage dumps. Originated in
North America and now grows wild in
all the world’s warm and moderate regions
Seed oil In this study
C.-J. Ruan et al. / Renewable Energy 41 (2012) 191e199192

3. Fig. 1. Five plants growing on unproductive agricultural lands: A: R. typhina [25]; B: K. pentacarpos; C: Seeds of K. pentacarpos and seed oil obtained by the method of expelling; D:
X. sibiricum [27]; E: D. candida; F: H. trionum.
Table 2
Oil content and relative contents of fatty acids in the seeds of five plants.
Item R. typhina K. pentacarpos X. sibiricum H. trionum D. candida
Oil content (%) 9.7 Æ 0.01 18.6 Æ 0.01 41.9 Æ 0.02 17.5 Æ 0.02 22.9 Æ 0.01
Lauric acid (C12:0) e 0.1% e e e
Myristic acid (C14:0) 0.1% e e 0.1% e
Pentadecanoic acid (C15:0) e 23.1% e e e
Ginkgolic acid (C15:1) e 0.2% e e e
Palmitic acid (C16:0) 8.9% e 5.7% 16.0% 13.7%
Palmitoleic acid (C16:1) e 0.2% e 0.4% e
Hexadecadienoic acid (C16:2) e 0.3% e e e
cisÀ10ÀHeptadecenoic acid (C17:1) e 2.8% e e e
Steartic acid (C18:0) 3.1% 2.8% 2.7% 3.4% 10.1%
Oleic acid (C18:1) 26.1% 21.0% 29.1% 27.8% 45.6%
Linoleic acid (C18:2) 60.1% 47.0% 62.5% 50.9% 30.0%
Nonadecenoic acid (C19:1) 0.3% e e e 0.5%
Arachidic acid (C20:0) 0.7% 0.4% e 0.7% e
Arachidonic acid (C20:1) 0.7% 1.6% e 0.5% e
cisÀ11,14ÀEicosadienoic acid (C20:2) e 0.5% e 0.2% e
Unsaturated C18 86.2% 67.9% 91.6% 78.7% 75.7%
Unsaturated acid 87.2% 73.5% 91.6% 79.7% 76.2%
e indicates the compound is not determined because of too low contents.
C.-J. Ruan et al. / Renewable Energy 41 (2012) 191e199 193

4. A
B
C
D
E
Fig. 2. Gas chromatogram of fatty acid methyl esters in the seeds of the five plants: R. typhina (A), K. pentacarpos (B), X. sibiricum (C), H. trionum (D) and D. candida (E). In (A): 14,
myristic acid; 16, nonadecenoic acid; 17, palmitic acid; 19, linoleic acid; 20 and 21, oleic acid; 22, steartic acid; 25, arachidonic acid; 26, arachidic acid; (B): 14, lauric acid; 16,
ginkgolic acid; 17, pentadecanoic acid; 19, hexadecadienoic acid; 20, palmitoleic acid; 22, cis-10-heptadecenoic acid; 23, linoleic acid; 24 and 25, oleic acid; 26, steartic acid; 27, cis-
11,14-eicosadienoic acid; 28, arachidonic acid; 29, arachidic acid; (C): 6, palmitic acid; 7, linoleic acid; 8 and 9, oleic acid; 10, steartic acid; (D): 17, myristic acid; 19, palmitoleic acid;
20, palmitic acid; 22 and 23, linoleic acid; 24 and 25, oleic acid; 26, steartic acid; 28, arachidonic acid; 30, arachidic acid; and (E): 9, myristic acid; 10, palmitoleic acid; 11, palmitic
acid; 12, linoleic acid; 13 and 14, oleic acid; 15, steartic acid. The un-annotated numbers in (A)e(E) were peaks that relative contents were too low or from impurity.
C.-J. Ruan et al. / Renewable Energy 41 (2012) 191e199194

5. [30e54]. Accordingly, the properties of the various individual fatty
esters that comprise biodiesel determine the overall fuel properties
of the biodiesel fuel [55]. Azam et al. [56] used the saponification
number and the iodine value of fatty acid methyl esters to estimate
the cetane number of seeds oils of some plants, while we fitted
a regression equation between the cetane number and relative
content of the four main components (C18:0, C18:1, C18:2 and
C18:3) by regression analysis using SPSS/PC-10, in which the cetane
numbers were treated as a dependent variable while the four main
components were treated as independent variables. By fitting
different regression equations in this study, the cetane numbers of
the biodiesel produced from the five plant oils were estimated by
using single variable regression (the C18:0, C18:1 and C18:2
content, respectively), enter multiple regression of two variables
(the C18:0 and C18:1 content) and stepwise regression of three
variables (the C18:0, C18:1 and C18:2 content).
2.4. Evaluation of potential of the five plants as biodiesel resources
According to the criterion of biodiesel, the cetane number is
51.0 for EN14214 for bio-auto fuels in the EU and 47.0 for
ASTMD6751 for biodiesel in the USA [57]. Commonly, if the oil
content of a plant is over 15% in seeds or other oil-bearing organs, it
could be considered as a potential energy plant. As such, the oil
content in the seeds of soybean is about 18% making it one of the
main energy plants used widely around the world [58]. In this
study, we evaluated the potential of each plant as a biodiesel
resource by its SOC and cetane number.
3. Results and discussion
3.1. SOC and relative contents of fatty acid
The SOC of the five plants ranged from 9.7% to 41.9% (Table 2).
For the woody species, R. typhina, with a SOC of 9.7% was the lowest
among the five plants. The perennial herb, K. pentacarpos, had an
SOC of 18.6% while among the three annual herbs, the highest SOC
of 41.9% was observed in X. sibiricum, followed by D. candida
(SOC ¼ 22.9%) and H. trionum (SOC ¼ 17.5%).
Fatty acid is the major component of grease. Fig. 2 shows
a typical gas chromatogram of the fatty acid methyl esters in the
seed oils of the five plants. Eight fatty acids in the seeds of R. typhina
were identified and quantified (Table 2, Fig. 2A), and three of those
(palmitic, oleic and linoleic acids) were the major fatty acids.
Unsaturated fatty acids (87.2%) predominated over the saturated
ones (12.8%), and unsaturated C18 accounted for 86.2%. In
K. pentacarpos, 12 fatty acids were identified and quantified
Table 3
Relative contents of C18 fatty acids and the cetane number (CN) in different plant
oils.
Species Relative contents of C18
fatty acids (%)
CN References
C18:0 C18:1 C18:2 C18:3
Aegle marmelos correa Roxb 8.8 30.5 36.0 8.1 48.3a
[30]
Aleurites fordii Hemsl e 6.5 9.0 e 36.3a
[30]
Aleurites moluccana Wild 6.7 10.5 48.5 28.5 34.2a
[30]
Aleurites montana Wils e 18.2 10.7 e 20.6a
[31]
Anamirta cocculus Wight Hrn 47.5 46.4 e e 64.3a
[31]
Annona reticulate Linn 7.5 48.4 21.7 e 53.5a
[30]
Aphanamixis polystachya Park 12.8 21.5 29.0 13.6 48.5a
[30]
Argemone mexicana 3.8 18.5 61.4 e 44.5a
[31]
Azadirachta indica 14.4 61.9 7.5 e 57.8a
[32]
Balanites roxburghii Planch 7.8 32.4 31.3 7.2 50.5a
[33]
Basella rubra Linn 6.5 50.3 21.6 0.4 54.0a
[34]
Biteer almond 1.3 62.9 30.4 e 48.0b
[35]
Broussonetia papyrifera Vent 6.1 14.8 71.0 1.0 41.3a
[34]
Calophyllum apetalum Wild 14.0 48.0 30.0 e 51.6a
[32]
Calophyllum inophyllum Linn 18.5 42.7 13.7 2.1 57.3a
[32]
Camellia oleifera 1.7 77.3 9.2 0.3 49.2b
[36]
Canabis sativa Linn e 15.0 65.0 15.0 36.4a
[37]
Canarium commane Linn 9.7 38.3 21.8 1.2 55.6a
[31]
Celastrus paniculatus Linn 6.7 46.1 15.4 3.0 51.9a
[38]
Corylus avellana 2.6 88.0 2.9 e 54.5a
[37]
Croton tiglium Linn 0.5 56.0 29.0 e 49.9a
[31]
Ervatamia coronaria Stapf 7.2 50.5 15.8 0.6 56.3a
[37]
Euonymus hamiltonianuis Wall 1.5 39.1 25.8 5.3 45.5a
[37]
Euphorbia helioscopia Linn 1.1 15.8 22.1 42.7 34.3a
[37]
Garcinia combogia Desr 38.3 57.9 0.8 0.4 61.5a
[32]
Garcinia echinocarpa Thw 43.7 52.6 e e 63.1a
[31]
Garcinia indica Choisy 56.4 39.4 1.7 e 65.2a
[31]
Garcinia morella Desr 46.4 49.5 0.9 e 63.5a
[32]
Gossypium spp. 1.8 17.7 56.1 0.4 45.0b
[39]
Idesia polycarpa Maxim. var.
vestita Diels
1.6 7.2 68.6 0.9 54.0b
[40]
Illicium verum Hook 7.93 63.24 24.4 e 50.7a
[41]
Jatropa curcas Linn 9.7 40.8 32.1 e 52.3a
[32]
Jatropha curcas L. 1.8 47.3 32.7 e 44.8b
[42]
Joannesia princes Vell e 45.8 46.4 e 45.2a
[31]
Kosteletzkya virginica 1.6 18.0 46.4 4.2 56.0b
[43]
Madhuca butyracea Mac 14.0 46.3 17.9 e 56.6a
[44]
Mallotus phillippinensis Arg 2.2 6.9 13.6 e 36.3a
[32]
Mappia foetida Milers 17.7 38.4 e 36.8 50.7a
[31]
Melia azadirach Linn 1.2 20.8 67.7 e 41.4a
[31]
Melia azedarach 3.7 21.7 67.4 0.3 47.0b
[45]
Mesua ferrea Linn 12.4 60.0 15.0 e 55.1a
[32]
Meyna laxiflora Robyns 9.0 32.5 39.7 e 50.4a
[46]
Michelia champaca Linn 2.5 22.3 42.5 e 50.3a
[37]
Minusops hexendra Roxb 14.0 63.0 3.0 e 59.3a
[31]
Momordica dioica Rox 16.9 9.2 8.8 e 36.0a
[37]
Moringa concanensis Nimmo 2.4 83.8 0.8 e 56.3a
[47]
Moringa oleifera Lam 2.7 79.4 0.7 0.2 56.7a
[47]
Myristica malabarica Lam 2.4 44.1 1.0 e 61.8a
[31]
Perilla frutescens Britton e 9.8 47.5 36.2 30.1a
[37]
Pongamia pinnata Pierre 6.8 49.4 19.0 e 55.8a
[32]
Princepia utilis Royle 4.5 32.6 43.6 e 48.9a
[31]
Pterygota alata Rbr 8.5 44.0 32.4 e 51.1a
[37]
Putranjica roxburghii 15.0 56.0 18.0 e 55.0a
[31]
Rhus succedanea Linn e 46.8 27.8 e 52.2a
[48]
Santalum album Linn 1.0 8.6 0.8 e 42.9a
[37]
Sapindus trifoliatus Linn 8.5 55.1 8.2 e 59.8a
[49]
Sapium sebiferum 2.7 15.5 30.8 39.7 43.9b
[50]
Sapium sebiferum e 15.1 31.6 44.2 45.0b
[51]
Sapium sebiferum Roxb 5.9 27.4 e e 30.7a
[31]
Saturega hortensis Linn 4.0 12.0 18.0 62.0 25.5a
[37]
Suaeda salsa 1.6 14.1 73.2 1.0 56.0b
[52]
Swietenia mahagoni Jacq 18.4 56.0 e 16.1 52.3a
[31]
Tectona grandis Linn 10.2 29.5 46.4 0.4 48.3a
[31]
Terminalia bellirica Roxb e 24.0 31.0 e 56.2a
[37]
Terminalia chebula Retz e 2.4 37.3 39.8 49.6a
[37]
Thevetia peruviana Merrill 10.5 60.9 5.2 7.4 57.5a
[53]
Vallaris solanacea Kuntze 14.4 35.3 40.4 e 50.3a
[37]
Verincid fordii 2.6 16.4 22.1 0.3 34.0b
[36]
Vernonia cinerea Less e 8.0 32.0 22.0 57.5a
[37]
Ximenia americana Linn 1.2 60.8 6.7 e 61.4a
[37]
Table 3 (continued)
Species Relative contents of C18
fatty acids (%)
CN References
C18:0 C18:1 C18:2 C18:3
Zanthoxylum bungeanum 1.1 35.9 24.9 15.9 46.0b
[54]
Ziziphus mauritiana Lam 5.5 64.4 12.4 e 55.4a
[37]
R. typhina 3.1 26.1 60.1 e 45.6c
This study
K. pentacarpos 2.8 21.0 46.9 e 45.9c
This study
X. sibiricum 2.7 29.0 62.5 e 46.5c
This study
H. trionum 3.4 27.8 50.9 e 46.9c
This study
D. candida 10.1 45.6 30.0 e 50.8c
This study
À Indicates the relative content is not determined.
a
CN estimated from reference [48].
b
CNs of biodiesel fuels from the matching reference cited in Table 3.
c
CN was the mean of CNs in Fig. 4, estimated by the regression equations 1, 2, 3
and 5 in Table 5, respectively.
C.-J. Ruan et al. / Renewable Energy 41 (2012) 191e199 195

6. (Table 2, Fig. 2B); unsaturated fatty acids (73.5%) predominated
over the saturated ones (26.5%), and unsaturated C18 amounted to
67.9%. Four fatty acids were identified and quantified in X. sibiricum
(Table 2, Fig. 2C); all unsaturated fatty acids were unsaturated C18
(91.6%). In H. trionum, nine fatty acids were identified and quanti-
fied (Table 2, Fig. 2D); unsaturated fatty acids (79.7%) predominated
over the saturated ones (20.3%), and unsaturated C18 accounted for
78.7%. Five fatty acids in the seeds of D. candida were identified and
quantified (Table 2, Fig. 2E); unsaturated fatty acids (76.2%) pre-
dominated over the saturated ones (23.8%), and unsaturated C18
totaled 75.7%.
3.2. Estimation of the cetane numbers of the biodiesel produced
from the five plant oils
According to the cetane numbers and the relative contents of
C18 fatty acids in the 70 published studies (Table 3), the cetane
number is positively and significantly correlated with the C18:0 and
C18:1 contents, and there is a significant negative correlation with
the C18:2 and C18:3 contents (Table 4). Negative significant
correlations were observed between C18:0 or C18:1 and C18:2 or
C18:3 (Table 4). Regressions between the cetane numbers and
relative contents of the four main components of C18 (C18:0, C18:1,
C18:2 and C18:3) in fatty acid (Table 5, Fig. 3) were estimated. Based
on the 1st, 2nd, 3rd and 5th regression equations in Table 5, we
estimated the cetane numbers of the biodiesel produced from the
five plant oils (Fig. 4). The mean cetane numbers of the biodiesel
produced from the five plant (R. typhina, K. pentacarpos,
X. sibiricum, H. trionum and D. candida) oils were 45.6 Æ 0.9,
45.9 Æ 1.0, 46.5 Æ 0.8, 46.9 Æ 0.6 and 50.8 Æ 0.7 (Table 3),
respectively.
3.3. Potential of the five plants as biodiesel resources
According to the SOCs and cetane numbers, our results showed
that four plants can be developed as energy plants growing on
unproductive agricultural lands, including D. candida, X. sibiricum,
K. pentacarpos and H. trionum. The remaining one plant, R. typhina,
is not adapted as an energy plant because of its lower SOC value,
9.7%. This could be evidenced by the following analyses.
First, except for R. typhina (SOC ¼ 9.7%), the remaining four
plants could be used as potential biodiesel resources by using the
oil content as common criteria for evaluation (SOC 15%). Seed oil
content is a key index for plant that is developed as biodiesel
resources, which directly influence the oil yield that determine its
developed potential. SOCs of K. pentacarpos (18.6%) and H. trionum
(17.5%) were higher than 15%, and equivalent to soybean widely
used as an energy plant throughout the world and whose oil
content is about 18% [58]. The SOCs of X. sibiricum (41.9%) and
D. candida (22.9%) were considerably higher than that of soybean
(SOC ¥ 18%, [58]).
Second, biodiesel fuel is a kind of mixture of higher fatty acids,
which is formed from the decomposition of glyceryl ester; its main
component is unsaturated C18 oleic acid [29]. Contents of unsatu-
rated C18 oleic acid in the seeds of the five plants used in this study
were over 67.9%, the maximum being in X. sibiricum (91.6%), the
minimum in K. pentacarpos (67.9%). According to the criterion of
biodiesel, the estimated cetane number of D. candida (50.8) was
higher than the cetane number 47.0 of ASTMD6751 in the USA.
However, compared to the criterion for biodiesel for EN14214 used
in the EU (cetane number 51.0), the cetane numbers of the five
plants in this study still need to be improved.
There are now about 0.1 billion ha of unproductive agricultural
lands (e.g. 3 Â 106
ha coastal tidal flats) in China, 60% of which is not
being exploited and reasonably utilized [43]. Vegetation is not only
the receiver of solar energy, but also provides the energy source of
the ecosystem to use its function. Vegetation recovery is thought to
be the most significant aspect in the utilization of unproductive
agricultural lands, especially when the plants used have high
energy, medicinal and nutritive values. Plant breeders have long
been interested in improving plants adapted to abiotic stress in
unproductive agricultural lands, and several tolerant plants with
potential interest for agriculture and environmental management
have already been identified; there has been some relative success
in over- or under expressing single or several genes by targeting
genes, proteins or enzymatic reactions that are important compo-
nents of stress tolerance or sensitivity [59e62]. However, the
alternative approach of introducing tolerance to abiotic stress into
conventional crops has, so far, not produced lines capable of
growing on high salinity water or high drought lands [63e66]. The
selection and breeding of wild tolerant plants as new plant
resources still appears to be the most feasible way to proceed in
developing agriculture for unproductive agricultural lands
[14,67,68]. Hence, four plants (D. candida, X. sibiricum,
K. pentacarpos and H. trionum) in this study, which could be
developed as energy plants growing on unproductive agricultural
Table 5
Linear regression between the cetane numbers (expressed as Y) and relative contents of four main components C18:0 (X1), C18:1 (X2), C18:2 (X3) and C18:3 (X4) in fatty acid,
using data from Table 3.
Variable ANOVA Coefficients Regression equation
(X1)a
F1, 60 ¼ 20.049, P 0.001 constant ¼ 47.109, B ¼ 0.354, Beta ¼ 0.500, t ¼ 4.478, P 0.001 Y1
¼ 47.109 þ 0.354X1, n ¼ 61 (R ¼ 0.550)
(X2)a
F1, 70 ¼ 37.746, P 0.001 constant ¼ 39.717, B ¼ 0.264, Beta ¼ 0.592, t ¼ 6.144, P 0.001 Y2
¼ 39.717 þ 0.264X2, n ¼ 71 (R ¼ 0.592)
(X3)a
F1, 65 ¼ 6.382, P ¼ 0.014 constant ¼ 53.117, B ¼ À0.137, Beta ¼ À0.299, t ¼ À2.526, P ¼ 0.014 Y3
¼ 53.117 e 0.137X3, n ¼ 66 (R ¼ À0.299)
(X4)a
F1, 31 ¼ 15.669, P 0.001 constant ¼ 52.003, B ¼ À0.298, Beta ¼ À0.579 t ¼ À3.958, P 0.001 Y4
¼ 52.003 e 0.298X4, n ¼ 32 (R ¼ À0.579)
(X1, X2)a
F2, 59 ¼ 34.561, P 0.001 constant ¼ 38.562, BX1 ¼ 0.288, BX2 ¼ 0.228, BetaX1 ¼ 0.408,
BetaX2 ¼ 0.545, tX1 ¼ 4.555, tX2 ¼ 6.085, P X2 0.001, PX2 0.001
Y5
¼ 38.562 þ 0.288X1 þ 0.228X2, n ¼ 61
(R ¼ 0.735)
(X2, X4)b
F2, 23 ¼ 16.842, P 0.001 constant ¼ 46.641, BX2 ¼ 0.145, BX4 ¼ À0.316, BetaX2 ¼ 0.334,
Beta X4 ¼ À0.573, tX2 ¼ 2.303, tX4 ¼ À3.951, PX2 ¼ 0.031, PX4 ¼ 0.001
Y6
¼ 46.641 þ 0.145X2 À 0.316X4, n ¼ 25
(R ¼ 0.771)
1, 2, 3, 4, 5,
and 6
serial number of regression equation.
a
Enter multiple regression.
b
Stepwise regression.
Table 4
Pearson correlations between the cetane numbers (expressed as Y) and relative
contents of four main components C18:0 (X1), C18:1 (X2), C18:2 (X3) and C18:3 (X4)
in fatty acid, using the data in Table 3.
X1 X2 X3 X4
X2 0.169
X3 À0.350a
À0.548a
X4 À0.065 À0.456a
À0.044
Y 0.500a
0.592a
À0.299b
À0.579a
a
Correlation is significant at the 0.01 level (2-tailed).
b
Correlation is significant at the 0.05 level (2-tailed).
C.-J. Ruan et al. / Renewable Energy 41 (2012) 191e199196

7. lands, will help to develop saline - and drought-tolerant vegetable
plants for fuel, food and fiber in the face of our ever-increasing
drought and salinized world [9,14] and to solve the heavily
depleted fossil-fuel energy crisis.
In addition, when we assess the suitability of one plant used to
biodiesel by the seed oil content and the cetane number, it is
necessary to consider other essential properties besides CN, such as
cold flow, viscosity and oxidative stability, which is directly related
with the relative components of fatty acids. Cold flow properties
are useful as biodiesel quality during the cold climate, which are
dependent on the feedstock (specific type of oil, fat or grease) from
which they are made and are a strong function of the level of
saturated fat [69]. Presently, the methods for improving cold flow of
biodiesel is to mix biodiesel and diesel fuel, and the improved cloud
Fig. 4. The cetane number of the biodiesel produced from the five plants (A: R. typhina; B: K. pentacarpos; C: X. sibiricum; D: H. trionum; E: D. candida) estimated by the regression
equation 1, 2, 3 and 5 in Table 5.
Fig. 3. Regression relationships between the cetane numbers and relative contents of four main components C18:0 (A), C18:1 (B), C18:2 (C) and C18:3 (D) in fatty acid.
C.-J. Ruan et al. / Renewable Energy 41 (2012) 191e199 197

8. points for the biodiesel blends correlated with the saturated frac-
tion, lower the fraction of saturates, better the cold flow [70]. One of
the most important fuel properties of biodiesel and conventional
diesel fuel derived from petroleum is viscosity. Biodiesel viscosity
at various temperatures could be predicted by saturated fatty acid
methyl esters of various chain lengths [71]. It increases with chain
length of either the fatty acid or alcohol moiety in a fatty ester or in
an aliphatic hydrocarbon [72]. Oxidation stability is an important
biodiesel fuel quality parameter. The rate of oxidation of fatty acid
methyl esters depends on the nature of fatty acids, temperature,
oxidation reaction catalysts and inhibitors contained in fats, light,
radiation intensity, etc. Oxidation stability of fatty acid methyl
esters could be increased by adding additional natural and
synthetic antioxidants [73]. Fatty acid methyl esters of vegetable
origin are more stable for oxidation comparing with methyl esters
of animal origin. Mixtures of methyl esters of animal and vegetable
origin with antioxidants were more stable compared with pure
products. The highest oxidation stability showed mixtures con-
taining 80e90% of fatty acid methyl esters of animal fat and 10e20%
of fatty acid methyl esters of vegetable oil with synthetic antioxi-
dants added [73].
4. Conclusions
According to the SOCs and the estimated cetane numbers of the
biodiesel produced from the five plant oils in this study, four plants
can be developed as potential energy plants, including D. candida
(SOC ¼ 22.9%, cetane number ¼ 50.8), X. sibiricum (SOC ¼ 41.9%,
cetane number ¼ 46.5), K. pentacarpos (SOC ¼ 18.6%, cetane
number ¼ 45.9) and H. trionum (SOC ¼ 17.5%, cetane
number ¼ 46.9). The remaining one plant, R. typhina, was not
adapted as an energy plant because of its low SOC, 9.7%. These
provide a scientific basis for growing energy plants in unproductive
agricultural lands as biodiesel resources. For example, D. candida,
an annual herb growing into a bush up to 2.5 m high in the world’s
warm and moderate regions, could be planted on unproductive
agricultural lands, such as wasteland, barrenland, salt land, desert
and dry regions. This possibly large-scale plantation will provide
a great deal of feedstock sources for potential biodiesel production.
Acknowledgments
This work was funded by the Fundamental Research Funds for
the Central Universities (DC10020102) and the Research Project of
Higher Education of Education Commission of Liaoning Province of
China (2009A150).
References
[1] Jia H-S, Xu Y- N. World biodiesel utilization and development strategies in
China. Journal of Plant Ecology 2006;30:221e30 (in Chinese with English
abstract).
[2] Zhang Y, Dube MA, McLean DD. Biodiesel production from waste cooking oil:
2. Economic assessment and sensitivity analysis. Bioresource Technology
2003;90:229e40.
[3] Narasimharao K, Lee A, Wilson K. Comparison of transesterification methods
for production of biodiesel from vegetable oils and fats. Journal of Biobased
Materials and Bioenergy 2007;1:19e30.
[4] Tat ME, Wang PS, Van Gerpen JH, Clemente TE. Exhaust emissions from an
engine fueled with biodiesel from high-oleic soybeans. Journal of the Amer-
ican Oil Chemists’ Society 2007;84:865e9.
[5] Beer T, Grant T, Campbell PK. The greenhouse and air quality emissions of
biodiesel blends in Australia. Report Number KS54C/1/F2.27. August 2007.
[6] National Biodiesel Board. Biodiesel as a greenhouse gas reduction option.
http://www.biodiesel.org/resources/reportsdatabase/reports/gen/20040321_
gen-332.pdf.
[7] Peplow M. Plant carbs harnessed to power cars. Nature; 2005/06/02.
doi:10.1038/news 050531e9.
[8] United Nations Population Information Network, www.un.org/popin/data.
html.
[9] Munns R. Genes and salt tolerance: bringing them together. New Phytologist
2005;167:645e63.
[10] Collard BCY, Mackill DJ. Marker-assisted selection: an approach for precision
plant breeding in the twenty-first century. Philosophical Transactions of the
Royal Society B: Biological Sciences 2008;363:557e72.
[11] Knothe G, Steidley KR. Kinematic viscosity of biodiesel components (fatty acid
alkyl esters) and related compounds at low temperatures. Fuel 2007;86:
2560e7.
[12] Rashid U, Anwar F, Moser BR, Ashraf S. Production of sunflower oil methyl
esters by optimized alkali-catalyzed methanolysis. Biomass and Bioenergy
2008;32:1202e5.
[13] Lieth H. Development of crops and other useful plants from halophyes. In:
Lieth H, editor. Halophyte uses in different climates I. Ecological and
ecophysiological studies, vol. 13. Leiden: Backhuys Publishers; 1999. p. 2e17.
[14] Rozema J, Flowers T. Crops for a salinized world. Science 2008;322:1478e80.
[15] Sea level rise alters bay’s salinity. http://www.physorg.com/news146400560.
html.
[16] Revenge on humans from seawater intrusion, especially in two provinces of
Shandong and Liaoning, China (in Chinese). http://www.cseac.com/Article_
Show.asp?ArticleID¼10563.
[17] Yuan W, Hansen AC, Zhang Q. Predicting the physical properties of biodiesel
for combustion modeling. Transactions of the ASABE 2003;46:1487e93.
[18] Yuan W, Hansen AC, Tat ME, Van Gerpen JH, Tan Z. Spray, ignition, and
combustion modeling of biodiesel fuels for investigating NOx emissions.
Transactions of the ASABE 2005;48:933e9.
[19] Yuan W, Hansen AC, Zhang Q. Vapor pressure and normal boiling point
predictions for pure methyl esters and biodiesel fuels. Fuel 2005;84:943e50.
[20] Knothe G, Matheaus AC, Ryan III TW. Cetane numbers of branched and
straight-chain fatty esters determined in an ignition quality tester. Fuel 2003;
82:971e5.
[21] Knothe G, Bagby MO, Ryan III TW. Precombustion of fatty acids and esters of
biodiesel. A possible explanation for differing cetane numbers. Journal of the
American Oil Chemists’ Society 1998;75:1007e13.
[22] Ladommatos N, Parsi M, Knowles A. The effect of fuel cetane improver on
diesel pollutant emissions. Fuel 1996;75:8e14.
[23] Knothe G, Dunn RO. Biofuels derived from vegetable oils and fats. In:
Gunstone FD, Hamilton RJ, editors. Oleochemical manufacture and applica-
tions. UK: Sheffield Academic Press; 2001. p. 106e63.
[24] Rhus typhina. University of Arkansas horticulture 3103 summary sheet.
http://www.uark.edu/campus-resources/cotinus/plants4_html/rhustyph.
html.
[25] Rhus typhina L. http://www.pfaf.org/user/Plant.aspx?LatinName¼Rhus%
20typhina.
[26] Pino J, Roa E. Population biology of Kosteletzkya pentacarpos (Malvaceae) in
the Llobregat delta (Catalonia, NE of Spain). Plant Ecology 2007;188:1e16.
[27] Xanthium sibiricum. http://www.rewolf.cn/canger-citoumang-zhantoumang.
html.
[28] AOAC International. Handbook for AOAC members. 6th ed. Gaithersburg, MD,
USA: AOAC International; 1989. 20877e22417.
[29] Zhao C, Fu Y-J, Zu Y-G, Zhang N-J, Wang L-L. Some strategies for studying the
production of biodiesel from oil plants. Chinese Bulletin of Botany 2006;23:
312e9 (in Chinese with English abstract).
[30] Anonymous. The wealth of India: raw materials, vol. I (revised). New Delhi:
Publication Information Directorate, Council of Scientific Industrial
Research; 1985.
[31] Hilditch TP, Williams PN. The chemical constituents of natural fats. 4th ed.
London: Chapman and Hall; 1964.
[32] Bringi NV. Non - traditional oilseeds and oils of India. New Delhi: Oxford IBH
Publishing Co. Pvt. Ltd; 1987.
[33] Ghanim A. Hingota: a tree of immense untapped potential. Indian Farming
1991;41:9e11.
[34] Anonymous. The wealth of India: raw materials, vol. II (revised). New Delhi:
Publication Information Directorate, Council of Scientific Industrial
Research; 1988.
[35] Wei LP. Researches on translating technique of biodiesel from Biteer almond
oil. Master Dissertation, Northwest A F University, 2008 (in Chinese with
English abstract).
[36] Li CZ, Jiang LJ, Cheng SQ. Study on preparation of bio-diesel with four woody
plant oils. Biomass Chemical Engineering 2006;40(Z1):51e5 (in Chinese with
English abstract).
[37] Tyagi PD, Kakkar KK. Non-conventional vegetable oils. New Delhi: Batra book
Service; 1991.
[38] Liu L, Yu M, Zhao XY, Dong X, Tufuti AMT, Bian Y. Analysis on physical and
chemical characters from cotton growing in Xinjiang, China. China Cotton
2007;34:24e5 (in Chinese with English abstract).
[39] Sengupta A, Sengupta SC, Mazumdar UK. Chemical investigation on Celastrus
peniculatus seed oil. Fett Wissenschaft Technologie 1987;89:119e23.
[40] Wang QY, Du KF, Li XY, Lan XQ, Song H. Research on production biodiesel
from Idesia polycarpa Maxim. var. vestita Diels. Cereals and Processing 2009;2:
51e5 (in Chinese with English abstract).
[41] Anonymous. The wealth of India: raw materials, vol. V. New Delhi: Publication
Information Directorate, Council of Scientific Industrial Research; 1959.
[42] Mao SC, Li ZY, Li C. Application of biodiesel produced from Jatropha curcas L.
seed oil. China Oils and Plants 2007;30(6):40e2 (in Chinese with English
abstract).
C.-J. Ruan et al. / Renewable Energy 41 (2012) 191e199198

9. [43] Ruan CJ, Li H, Guo YQ, Qin P, Gallagher JL, Seliskar DM, et al. Kosteletzkya
virginica, an agroecoengineering halophytic species for alternative agricultural
production in China’s east coast: ecological adaptation and benefits, seed
yield, oil content, fatty acid and biodiesel properties. Ecological Engineering
2008;32:320e8.
[44] Singh A, Singh IS. Chemical evaluation of mahua (Madhuca indica
[M. longifolia]) seeds. Food Chemistry 1991;40:221e8.
[45] Li XH. Research on extraction of Melia azedarach seed oil and the process of
biodiesel production. Master Dissertation, Northwest A F University; 2008.
[46] Anonymous. The wealth of India: raw materials, vol. VI. New Delhi: Publica-
tion Information Directorate, Council of Scientific Industrial Research;
1962.
[47] Banerji R, Verma SC, Pushpendra P. Oil potential of Moringa. Natural Product
of Radiance 2003;2:68e9.
[48] Anonymous. The wealth of India: raw materials, vol. IX. New Delhi: Publication
Information Directorate, Council of Scientific Industrial Research; 1972.
[49] Anonymous. The wealth of India: raw materials, vol. VII. New Delhi: Publi-
cation Information Directorate, Council of Scientific Industrial Research;
1966.
[50] Cheng WW. Research of biodiesel production from Chinese Tallow kernel oil.
Ph.D Dissertation. Nanchang University; 2006.
[51] Yan ZB, Qu YT, Wang XG, Yang L, Lei AQ, Sun YP, et al. Preliminary report on
research of Sapium sebiferum Roxb. seed producing biodiesel. HuBei Forest
and Scientific Technology 2007;6:32e4 (in Chinese with English abstract).
[52] Yang QL, Zhu F, Zhang CS, Yu SL, Qin S. Optimization of technological process
for synthesizing biodiesel from Suaeda salsa. Modern Chemical Industry 2008;
28(S2):43e6 (in Chinese with English abstract).
[53] Saxena VK, Jain SK. Thevetia peruviana kernel oil: a potential bacterial agent.
Fitoterapia 1990;61:348e9.
[54] Yang FX. Research on biodiesel productions from Chinese prickly ashseed
(Zanthoxylum bungeanum Maxin) oil and shuidonggua (Idesia polycarpa
Maxim. var. vestita Diels) oil. Master Dissertation. Northwest A F University;
2006 (in Chinese with English abstract).
[55] Knothe G. Dependence of biodiesel fuel properties on the structure of fatty
acid alkyl esters. Fuel Processing Technology 2005;86:1059e70.
[56] Azam MM, Waris A, Nahar NM. Prospects and potential of fatty acid methyl
esters of some non-traditional seed oils for use as biodiesel in India. Biomass
and Bioenergy 2005;29:293e302.
[57] Biofuel specifications. http://www.biofueltesting.com/specifications.asp.
[58] Yang G-Y, Wang Y, Ma X- P. Research on fat content and composition of fatty
acid of wild soybean (G. soja) in China. Soybean Science 2000;19:258e62 (in
Chinese with English abstract).
[59] Sung DY, Kaplan F, Lee KJ, Guy CL. Acquired tolerance to temperature
extremes. Trends in Plant Science 2003;8:179e87.
[60] Baniwal SK, Bharti K, Chan KY, Fauth M, Ganguli A, Kotak S, et al. Heat stress
response in plants: a complex game with chaperones and more than twenty
heat stress transcription factors. Journal of Bioscience 2004;29:471e87.
[61] Mittler R, Vanderauwera S, Gollery M, Van Breusegem F. Reactive oxygen gene
network of plants. Trends in Plant Science 2004;9:490e8.
[62] Bohnert HJ, Gong QQ, Li PH, Ma SS. Unraveling abiotic stress tolerance mecha-
nisms e getting genomics going. Current Opinion in Plant Biology 2006;9:180e8.
[63] Yeo A. Molecular biology of salt tolerance in the context of whole-plant
physiology. Journal of Experimental Botany 1998;49:915e29.
[64] Flowers T. Improving crop salt tolerance. Journal of Experimental Botany
2004;55:307e19.
[65] Colmer T, Munns R, Flowers T. Improving salt tolerance of wheat and barley:
future prospects. Australian Journal of Experimental Agriculture 2005;45:
1425e43.
[66] Flowers T, Flowers S. Why does salinity pose such a difficult problem for plant
breeders? Agricultural Water Management 2005;78:15e24.
[67] Glenn E, Brown J, Blumwald E. Salt tolerance and crop potential of halophytes.
Critical Reviews in Plant Sciences 1999;18:227e55.
[68] Tsuyuzaki S. Vegetation development patterns on skislopes in lowland Hok-
kaido, northern Japan. Biological Conservation 2002;108:239e46.
[69] Chiu CW, Schumacher LG, Suppes GJ. Impact of cold flow improvers on
soybean biodiesel blend. Biomass Bioenergy 2004;27:485e91.
[70] Krishna CR, Butcher T. Improving cold flow properties of biodiesel. http://
www.aertc.org/conference/AEC_Sessions%5CCopy%20of%20Session%202%
5CTrack%20B-%20Renewables%5C1.%20Climate%20Change%20Biofuels%20III%
5C1.%20Dr.%20CR%20Krishna%5CCR%20Krishna%20presentation.pdf.
[71] Krisnangkura K, YimsuwanT Pairintra R. An empirical approach in predicting
biodiesel viscosity at various temperatures. Fuel 2006;85:107e13.
[72] Knothe G, Steidley KR. Kinematic viscosity of biodiesel fuel components and
related compounds. Influence of compound structure and comparison to
petrodiesel fuel components. Fuel 2005;84:1059e65.
[73] Sendzikiene E, Makareviciene V, Janulis P. Oxidation stability of biodiesel fuel
produced from fatty wastes. Polish Journal of Environmental Studies 2005;14:
335e9.
C.-J. Ruan et al. / Renewable Energy 41 (2012) 191e199 199