ARTICLE
Auteur(s) : Klaus Becker
University of Hohenheim, Institute for Animal Production in the
Tropics and Subtropics, Fruwirthstrasse 12, 70599 Stuttgart
Introduction
Close to 40% of the world’s population of 7 billion people
will not have access to affordable energy resources and portable
water in the distant future.
Concomitantly, the number of hungry people has risen to close to
one billion in 2008, according to the recent FAO statistics. To
this stock of global problems new challenges are added through the
increase in human population of 80-100 million annually and
the concomitant loss of large areas of former fertile crop land,
largely in the poorest countries.
Global petroleum growth has been quantified by the US-Energy
Information Administration (EIA) [1] at 1.7 million barrels
d-1 in 2006 and is expected to increase to
1.8 million barrels d-1 in 2007 and further in
the distant future ahead.
Political CO2 reduction targets in the EU have been a
main driver for enhanced biofuel production. This has led to the
conversion of huge areas of intact environments in hot regions to
produce renewable biofuels.
Jatropha curcas, native to Central America, is a very hardy
plant that grows on degraded agricultural lands or even in the
desert sand of Upper Egypt. It doesn’t have to compete with food
crops for arable land and incurs little or no carbon debt thus
offering immediate and sustained greenhouse gas advantages.
Globally, there are huge areas of wasteland available for
planting Jatropha.
The Jatropha plant
The plant is reported to be approximately 70 million years
old. In 1737 Karl von Linne first described and in
1753 classified Jatropha curcas. It is a member of the large
Euphorbiaceae family and consists of between 165-175 species.
The genus name Jatropha is derived from the Greek iatros
(doctor) and trophe (food). There are two genotypes of Jatropha
curcas, a toxic and a non-toxic, edible one. To the best of our
knowledge the non-toxic genotype is found in Mexico only. Jatropha
curcas is a shrub or a small to medium sized tree. Solitary trees
grow large and can reach heights of more than 12 m in
Paraguay. On the Cap Verde Islands trees as old as 120 years
show trunk diameters close to 100-120 cm.
It is a perennial C-3 plant, native and widely spread
throughout pan tropical countries. Because of its toxic nature it
is not grazed by animals and grows readily in poor stony soils. In
fact, huge areas of former cropland are lost every year and are
available for planting Jatropha curcas. A way to eventually
reclaim that land again for crop production through Jatropha
cultivation is not an illusion but could soon become a reality.
The plant is diploid with 2n=22 chromosomes [2].
Standard quantitative genetic methods have not been applied to
the pan tropical wild genotypes of Jatropha curcas. Only in the
last couple of years first selection and breeding activities have
been initiated.
The cultivation of Jatropha was of economic importance in Cape
Verde and Madagascar. Export quantities of the seeds to Lisbon,
Portugal is reported to have reached almost 6,000 tones in
1900 and still 4,500 tones in 1955. Trade with Jatropha
seeds between Cap Verde and Portugal ended in 1970 [3, 4].
A second centre for Jatropha was on the island of Madagascar
whose total harvest was exported to Marseille, France, from which
the famous soap Savon de Marseille was produced.
It has been reported that Jatropha curcas has an excellent
adaption capacity to a huge range of soil conditions. Equally,
Jatropha appears well adapted to conditions of low and very low
soil fertility. Mineral deficiency symptoms are rarely observed,
due to the fact that root excudates have the potential to
solubilize immobile mineral complexes.
Temperature plays a central role in the Jatropha cultivation.
The preferred range of average temperature lies between 25 °C and
over 30 °C depending on water availability. Jatropha is a typical
tropical plant and doesn’t tolerate frost and shows sensitivity to
temperatures below 15 °C by shedding its leaves and falling into a
dormancy state until temperatures recover. Water deficiency leads
to the same effect. Most often a combination of both of these
environmental factors terminates photosynthetic activity.
The drought tolerance and adaption capacity to long, severe dry
periods are well developed. On the other hand, Jatropha tolerates
humid conditions equally well, showing good growth with high, well
distributed rainfall.
Grown in the wild, Jatropha seems to be quite disease resistant.
Planted on large areas in monocultures, this natural resistance
weakens and plant protection measures are required.
The monoecious plant (i.e. unisexual reproductive units of both
sexes appear on the same plant) is pollinated by insects. Jatropha
is self-compatible [5], but cross pollination is supported by a
time gap between anthesis of male and female flowers [6].
Jatropha can be propagated as cuttings or with seeds. Plants
propagated vegetatively do not usually form tap roots [7]. This
might be a disadvantage for plants established on unfertile
wasteland, as a strong tap root system facilitates effective water
and mineral acquisition and use. To support a better rooting system
of the cuttings they should be cut flat and not diagonal, otherwise
roots only develop around the tip of the cut and not all the way
around the stem. The cuttings should be lignified, 30 cm long
and should have a diameter of 3 cm.
The multifunctional uses of the plant
Jatropha is a multipurpose plant. Although oil production to
replace fossil fuel is very often the main reason for planting this
crop, the plant has other important roles, such as 1) land
reclamation and additional agro ecological advantages; 2) erosion
control and as shelter/support for other plants; 3) provision of
protein rich seed meal after detoxification as feed for all farm
animals including fish and shrimps; 4) provision of chemicals
(phorbol ester) with potential in medicine, pharmaceutical and
biopesticide applications (e.g. the toxic substance phorbol ester
present in the oil in high concentration kills the vector snail of
schistosomiasis – the second most serious human disease after
malaria in the tropics – at an extremely low concentration and
without harming fish in the same water body; 5) carbon dioxide
emission impact (GHG reduction); 6) contribution to human welfare
and the economy in particular.
The re-greening of degraded land through the cultivation of
Jatropha is environmentally of vital importance. Approximately
500 million ha of land are already degraded in Africa alone.
Annually we are loosing almost 10 million ha worldwide. The
production of non-edible oils on these soils contributes to the
agricultural and household supply in lesser developed countries.
Surplus production can be sold on national or international markets
for a fair price. Positive feeding results with detoxified Jatropha
meal have been achieved with cold and warm water fish and salt
water shrimps [8-14].
The concomitent production of renewable protein resources from
energy plants with a high physiological quality is of utmost
importance for small farmers in the tropics. Protein deficiency,
especially in infants and small children is a serious problem. It
is mainly due to the low production of animal protein because of
the lack of high protein feed to achieve an acceptable performance.
Detoxified Jatropha meal always showed a better performance in all
feeding experiments with fish than soy meal. The protein content of
Jatropha meal is about 60%, 15% higher than in soy meal.
The plant’s toxicity is concurrently a comparative advantage in
critical environments because animals do not eat it. We have
developed efficient extraction methods to remove the phorbol esters
from the oil. The use of these esters is still in the early stages
for many potential applications. Well established is already the
extremely high potency to fight the vector snail of
schistosomiasis.
Other applications are being discussed for organic agriculture,
pest management and the veterinary sector.
The undamped request for fossil fuels leads to a substantial
increase of CO2 emissions. The production of energy
plants on farmland, former pastures or even cleared rainforest must
be refrained because it will take many years before the negative
CO2 balance is compensated, much less that it leads to a
real economic effect.
On the other hand, Jatropha grows on degraded soils
(eroded/waste land) and does not accelerate carbon dioxide emission
through change of land use for bioenergy production. Through its
suitability for wasteland recultivation Jatropha curcas provides
two mechanisms for GHG abatement: substitution of fossil fuel and
CO2 sequestration through increasing carbon stocks above
and below ground. Here the Clean Development Mechanism (CDM)
applies. Those emission reductions in the lesser developed
countries may be more cost effective than in an industrialized
country. This opens up a good opportunity for developing countries
to generate income next to achieving energy autharcy.
Important co-products
Figure 1 shows
the morphological fractions, and their multiple uses. In figure 2, the Jatropha
fruit is divided up as follows: Calculated on a basis of
1000 kg fruits, 350 kg of fruit husk and 650 kg of
seeds are accrued. The proportion of the husk can be assumed at an
average of 35% which results in about 230 kg of seed husk and
420 kg of kernels. The kernels are rich in oil and can contain
anywhere from almost 50% to more that 60% oil.
The most important co-product is the kernel meal with about
180 kg per ton of dry fruits, or 270 kg of high value
protein concentrate (kernel meal) from 1 ton of Jatropha
seeds.
The husk (dried fruit encapsulate) of Jatropha also has a high
energy content of around 16 MJ kg [15] and could be used
as a soil amendment or for generating energy through burning. The
seed shell is extremely lignin rich (45-51%) and thus higher in its
energy content (~ 19.5 MJ) than the fruit husk. Because
of the intensive lignification of both these materials, their use
for biogas fermentation is not a good option.
Potential yield of Jatropha curcas plantations
It has to be stated clearly at this point that the plant has no
history of selection and breeding as we know it from other
agricultural plants. Maize, for instance, has been bred for almost
100 years now, potatoes for about 80 and canola for the
last 55 years. The yield of wild plants can be increased
considerably through selection and breeding. These activities are
still in infancy. Some institutions have initiated work on this.
A few data on yields are found in non-refereed literature. The
reported harvest yields span from 0.1 to 10 tones of
seed/ha.
A few yield determining parameters are discussed in table 1 including especially, the planting density,
which varies in this example between 625-2500 plants per ha.
Plant density between 830 (3 × 4 m) and 1111 (3 ×
3 m) are mostly chosen. It can be derived, that with the
lowest planting density, between 6.4-25.6 kg of seed per plant
have to be harvested if oil yields ranging between 1 and
4 tones per ha are expected. If pressing is done physically
(screw pres) the press residue still contains between 6-9% of rest
oil. If solvent extraction is used it lies below 1%, which means
that the latter procedures achieves an oil yield that is about 20%
higher.
Production and harvest details of the most important oil crops
are given in table 2.
Table 1 Potential yield of Jatropha curcas L.
plantations (mechanical oil pressing, 35% oil seed content, 7% rest
oil in press cake).
|
Tons oil/ha
|
Needed output with various planting densities (kg seeds/plant)
to achieve the targeted oil yield
|
|
4 m × 4 m (625 plants/ha)
|
2 m × 4 m (1,250 plants/ha)
|
2 m × 2 m (2,500 plants/ha)
|
|
4.0
|
25.6
|
12.8
|
6.4
|
|
2.0
|
12.8
|
6.4
|
3.2
|
|
1.5
|
9.6
|
4.8
|
2.4
|
|
1.0
|
6.4
|
3.2
|
1.6
|
Table 2 Production and harvest details of the most
important oil producing plants.
|
Oil plant
|
Worldwide* oil production (Mill. tones)
|
Average harvest (tones ha-1 y-1)
|
|
Fruits
|
Oil
|
Oil content (%)
|
|
Oil palm
|
33.2
|
17.82
|
3.57
|
20.0
|
|
Soy bean
|
32.4
|
2.281
|
0.38
|
16.7
|
|
Canola
|
15.7
|
1.541
|
0.58
|
37.6
|
|
Sunflower
|
9.2
|
1.171
|
0.44
|
37.6
|
|
Groundnut
|
4.9
|
1.421
|
0.22
|
15.5
|
|
Cotton
|
4.8
|
1.101
|
0.12
|
16.7
|
|
Jatropha curcas
|
< 0.1
|
< 0.1 - ?
|
?
|
~ 35.03 < 25-42
|
Oil quality
Jatropha oil very much mirrors rape seed fatty acid composition
(table 3) and in important physical
parameters (table 4). Hence it is well
suited for conversion into biodiesel. Within the scope of a
research project with DaimlerChrysler and the CSMCRI, Bhavnagar,
India, parameters were developed for a high value biodiesel from
Jatropha oil. First street tests with common rail injection (CDI)
diesel cars and lately small transporters (track cars) started as
early as 2004. To date, approximately 100.000 L of neat
Jatropha biodiesel (Jatropha methyl ester, JME) have been tested
under various climatical conditions. These tests have shown that
there is only a minimally better efficiency of 1.7% in consumption
in favour of fossil diesel (table 5),
whereas the particulate matter dropped by 80% in JME.
JME meets EN specification 14214. Further information on
biological properties can be found in [16].
Table 3 Fatty acid composition of toxic and non-toxic
Jatropha curcas oil.
|
Systematic name
|
Toxic (%)
|
|
Myristic
|
0.1
|
|
Palmitic
|
15.3
|
|
Heptadecanoic
|
0.1
|
|
Stearic
|
6.6
|
|
Arachidic
|
0.2
|
|
Behenic
|
tr
|
|
Lignoceric
|
tr
|
|
Total saturated
|
22.3
|
|
Palmitoleic
|
0.9
|
|
Oleic
|
41.0
|
|
Eicosenoic
|
0.1
|
|
Total monosaturated
|
42.0
|
|
Linoleic
|
35.3
|
|
Ά-linoleic (ALA)
|
0.3
|
|
Total PUFA
|
35.7
|
Table 4 Typical physical and chemical properties of
Jatropha curcas seed oil.
|
Calorific value
|
37.8 MJ/kg
|
|
Appearance
|
Light yellow liquid
|
|
Specific gravity at 30°/30°
|
0.92
|
|
Acid value
|
1.24
|
|
Saponification value
|
197
|
|
Iodine value
|
102
|
|
Unsaponifiable matter
|
0.4%
|
Table 5 Jatropha curcas – oil and biodiesel quality.
|
|
|
Actual measurements
|
|
Units
|
EU3 Limits
|
Fossil Diesel
|
Bio Diesel
|
Changes against limits %
|
|
Fossil
|
Bio Diesel
|
|
CO
|
g/km
|
0,64
|
0.08
|
0.11
|
– 88
|
– 83
|
|
HC
|
g/km
|
0.56
|
0.04
|
0.02
|
– 92.9
|
– 96.4
|
|
NOx
|
g/km
|
0.5
|
0.37
|
0.39
|
– 26
|
– 22
|
|
Particulates
|
g/km
|
0.05
|
0.03
|
0.01
|
– 40
|
– 80
|
|
Fuel consumption
|
L/100 km
|
6.47
|
6.58
|
|
1.70%
|
Competition between food and fuel production
In the year 2007 cereal trade amounted to close to
250 million tones globally. The main imports of cereal went to
Asia with 108 million tones, followed by Africa with
49 million tones. Based on average yields of 5 tones of
cereal (Asia) and 0.5 tones for Africa, an area of
21 million and 98 million respectively would be necessary
to produce those imports. There is no doubt that those areas are
available without problems if the production is profitable for the
small scale farmers. But there is a need for micro fertilization of
food crops all over the lesser developed countries. Examples from
the Sahelian countries are very promising concerning mineral
fertilization. Here it could be shown, that 4 kg of pure
phosphate per hectar of millet increased grain harvest by
100 and straw yield by 400% [17]. Still it must be emphazised
that energy plants are not produced on potentially arable farm
lands in countries with food deficits. Jatropha offers a solution
because it thrives on degraded soils, even in the desert of Upper
Egypt as long as the inputs, water and nutrients are made
available.
Social-economic impact of Jatropha cultivation
Many of the 500-600 millions of small scale farmers in lesser
developed countries cultivate 20-30% of their land with an
extremely high production risk, because this portion of their land
is heavily degraded. Bad harvests are the norm on such areas.
Therefore, it is suggested to cultivate a perennial on such soils,
like Jatropha. The very positive influence of this kind of
vegetation will help reclaim this land in a relative short period
of time and make it again suitable for staple crop production.
A positive influence is also to be expected with respect to
labour engagement in the rural areas. We estimate that a year-round
labour force of 30 for 100 ha is required if most of the
work on the plantation is done by hand labour. A bioenergy
plant would also save hard currency for developing countries by
reducing the import bill of fossil fuels.
Another negative effect results from climate change, especially
the distribution and amount of precipitation. Subsistence oriented
small scale farmers cultivate their land solely by hand labour,
whereas semi-intensive farms resort to a certain mechanisation.
This gives them a comparative advantage because they are able to
prepare their fields to plant the seeds in the desired acrage with
a higher power of impact if the rainfall comes very late. Farmers
that solely rely on hand labour are unable to cultivate all their
fields in the short period of remaining time. This could be
improved by offering an affordable type of bio-fuel.
Conclusion
In contrast to other fossil fuel alternatives, like biofuels from
food crops such as maize, soy bean, sugar cane and palm, bioenergy
from Jatropha curcas grown on wasteland incurs no carbon debt and
thus, offers immediate and sustained greenhouse gas advantages.
Converting crop or grasslands to expand biofuel production will
probably worsen the CO2-emission and thus global
warming. It would also threaten food security.
Jatropha curcas, a native perennial to tropical regions, is
adapted to harsh environmental conditions. It’s multifunctional
properties and a potential array of uses give the plant advantages
over other oil producing crops. Because of the toxic compound
“phorbol ester” [18] the oil from the toxic genotype is not edible
and hence does not compete with human consumption, as long as it is
planted on degraded lands.
Due to the wild nature of the plant, productivity varies
considerably. This huge variation is of importance from a breeder’s
point of view for future selection and breeding programs. Such
programs coupled with the development of agronomical practices, are
essential prerequisites for economic exploitation of Jatropha
curcas.
References
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crop for the generation of biodiesel and value-added coproducts.
Eur J Lipid Sci Technol 2009 ; in press.
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spatial soil variability on yield and nutrient uptake of pearl
millet (Pennisetum glaucum L.) in Southwest Niger. Stuttgart,
Germany : Verlag Ulrich Grauer, 1995.
18 Goel G, Makkar HPS, Francis G, Becker K.
Phorbol esters: Structure, biological activity, and toxicity in
animals. Int J Toxicol 2007 ; 26 : 279-88.
|
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