沙漠研究 24-1, 231-235 (2014)
Ἃ₍◊✲ 24-1, 231 - 235 (2014)
Journal of Arid Land Studies
Journal of Arid Land Studies－ DT11 Refereed Paper －㸫DT11 Refereed Paper㸫

Halophyte Biomass- A Promising Source of Renewable Energy Natalya AKINSHINA*1), 2), Kristina TODERICH1), Azamat AZIZOV2), Laurel SAITO3) and Shoaib ISMAIL1)
Abstract: Halophytes are suggested as energy crops in arid saline lands. Anaerobic digestion of 7 halophytes collected in the
Kyzylkum desert (Uzbekistan) were studied in batch-mode tests in mesophilic (35°C) and thermophilic (55°C) conditions with stirring
and F/M=0.2. Obtained results showed that halophytic biomass should be considered as a valuable renewable source of biogas.
Though high mineral content was detected in the biomass (i.e., Na+, K+, Cl- and SO42-), total biogas yields in results of anaerobic
degradation were about 200-400 mL (at 35°C) and 300-500 mL (at 55°C) from 1 gDM (with 60% of methane-gas). Total organic
matter and organic carbon (OC) concentrations were determined to investigate plant biomass. Organic matter concentrations were
between 736-900 mgVS/gDM. The highest organic carbon content found in biomass of Suaeda paradoxa, Atriplex nitens, Karelinia
caspia and conventional grass Cynodon dactylon were 243.9, 337.6, 394 and 396 mgOC/gDM, respectively. Low OC content(about 200 mgOC/gDM) was measured in biomasses of Salicornia, Halostachys and Climacoptera. Results indicated that 40-60%
of total organic matter in halophyte biomass can be decomposed into biogas. The highest yield of approximately 300-500 m3 of
biogas from 1 tDM could be produced from Atriplex nitens, Karelinia caspia, Suaeda paradoxa and Cynodon dactylon. Afterconsidering annual biomass yield of the studied plants, their current use, and biogas generation measured in the laboratory, Karelinia
caspia (wild associations or cultivated plantations) is recommended as one of the most promising renewable sources for biogas
production in desert salt-affected areas of Central Asia.
Key Words: Biogas, Biomass, Halophyte, Karelinia caspia (Pall.) Less

1. Introduction
The importance of seeking renewable sources of energy is
growing steadily. Leading the way is the use of methane gas
obtained from fermentation processes in biogas digesters.
The idea to use dedicated plant biomass, the so called“energy crops”, for methane production (biomethanation) is
not new. Early investigations on the biomethanation potentialof different crops and plant materials were carried out in the
1930s by Buswell in the USA and later in the 1950s by
Reinhold and Noack in Germany. In 1980, Stewart described
the potential use of oats, grass and straw for energy productionin New Zealand (Hendricks and Bushnell, 2008).
Numerous plants and plant materials have been tested fortheir methane formation potential. In principle several
varieties of grass, clover, cereal and maize including wholeplants, as well as, rape or sunflower have proven feasible formethane production. Even hemp, flax, nettle, miscanthus,
potatoes, beets, kale, turnip, rhubarb and artichoke have beentested successfully (Hendricks and Bushnell, 2008).
Plant biomass utilization for renewable energy production* Corresponding Author: n.akinshina@yahoo.com

is usually related to using arable lands for energy crop
cultivation, which has given rise to the criticism that food crops
are being diverted to energy production in developed countries
even as millions in the developing world do not have adequate
food to eat.
Therefore it is important to use fertile lands for food andfodder production. Alternatively, marginal resources (salinelands and mineralized / drainage / thermal water) could be used
to cultivate plants for energy. Halophytes and salt-tolerant
plants can be grown in salt-affected, degraded and abandoned
unproductive lands.
There are a number of annual and perennial species among
halophytes that are able to uptake significant amounts of salts
in biomass and remove them from saline soils. Halophytic
biomasses could be used in different ways because most are
multipurpose plants. Some halophytes can be used for food,
fodder, or forage production in marginal environments. In
other words, cultivation and sustainable utilization of wild ordomesticated halophytic and salt-tolerant plants could play animportant role for salinity control, remediation of saline lands
and improvement of livelihoods of rural communities in the㸦Received, September 15th, 2013; Accepted, January 19th, 2014㸧

6, Osyo street, Yunus-Abad District, Tashkent, 100000, Uzbekistan
1) International Center for Biosaline Agriculture, Dubai, UAE2) Department of Applied Ecology, The National University of Uzbekistan named after Mirzo.Ulugbek, Uzbekistan
3) Department of Natural Resources and Environmental Science and Graduate Program of Hydrologic Sciences, University of Nevada Reno, USA

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Central Asian region (Gintzburger, 2003; Akinshina, 2012).
In addition, halophytes may be useful as sources of biogas.
This paper presents original work regarding biogas
potential of some halophytes in Central Asia, including anassessment and identification of the most promising species asenergy crops.

2. Materials and Methods
Biomasses of widespread wild halophytes were sampled
for the study on desert salt-affected sand-loamy soils in the
Karakata saline depression, 80-100 m above sea level, Central
Kyzylkum, Uzbekistan in 2012-2013. The predominant soil
salinity was sulfate-chloride. Ground water mineralization
was 2.0-8.2 g/L. Sodium and magnesium were the dominantcations. The ground water table fluctuated from 0.8-2.5 m.
Thermal water from artesian wells (EC about 4 mS/cm) was
the single water source in the area.
Halostachysbelangeriana,
Salicornia
europaea,
Climacoptera lanata, Climacoptera brachiata, Suaeda
paradoxa, Atriplex nitens and Karelinia caspia were
investigated. Conventional grass, Cynodon dactylon, wastaken for comparison with halophytes. Plant biomass was
air-dried and well-milled before the study.
Chemical compositions of the plant biomass wereidentified. Total mineral compounds (ash) and organic
fractions (VS, volatile solids) in biomasses were measured by
the gravimetric method after burning of dried biomass in melt
pots was complete (at 605°C, 1 hour) (Vorobyova and
Makarenko, 2005). Concentrations of main mineral ions
(Na+, K+, Mg2+, Cl-, SO42-) were determined in water extractsof the biomass (0.2gDM in 100 mL deionized water, shaken 1hour and filtered). Sodium, potassium and chloride ions were
measured using a pH/ion meter (“Expert-001.3” (Russia)) in
accordance with standard electrometric methods ofmeasurement for ion-selective electrodes (Elit-031 (K+);
Elit-261 (Cl-), Elis-112Na (Na+)). Sulfate-ion concentrations
were measured in the same water extracts using UV/VIS
Spectrophotometer V-530 (“Jasco”). Organic carbon (OC)was also measured by a spectrophotometric method withpreliminary wet process of biomass by 0,4 M chrome mixture(K2Cr2O7+H2SO4) (Vorobyova and Makarenko, 2005).
Anaerobic degradation of plant biomass for biogas
production was studied in lab-scale batch-mode experiments.
Anaerobic sludge was taken from Salar Waste Water Treatment
Station in Tashkent City and Institute of Microbiology of
Academy of Science of Uzbekistan. Reactors (1 L glass
vessels) were operated in mesophilic (35°C) and thermophilic(55°C) conditions with stirring with an F/M ratio of 0.2.
OriginPro7.5 was used for statistical analysis of the data.

Table 1. Mineral matter (Ash), Volatile solids (VS) and Organiccarbon (OC) in plant biomass.
Name

mg/g DM
Ash

Halostachysbelangeriana
447.91+447.91± 70.41(Hal)
Salicornia
485.52+485.52± 10.11
europaea (Sal)Climacoptera
428.02+13.94
428.02±13.94
lanata (Cli l.)
Climacoptera
372.51+30.42
372.51±30.42
brachiata (Cli b.)
Suaeda paradoxa
264.04+41.24
264.04±41.24(Sua)
Atriplex nitens
172.31+19.83
172.31±19.83(Atr)
Karelinia caspia
137.61+5.51
137.61±5.51(Kar)
Cynodon dactylon
101.22+0.32
101.22±0.32
(Cyn)

VS

OC

552.09+40.44
552.09±40.44

178.75+27.22
178.75±27.22

514.48+10.13
514.48±10.13

168.31+18.04
168.31±18.04

572.03+13.87
572.03±13.87

207.98+19.50
207.98±19.50

624.84+30.37
624.84±30.37

213.04+24.73
213.04±24.73

735.95+51.25
735.95±51.25

243.96+44.15
243.96±44.15

827.73+827.73± 19.80

337.58+45.43
337.58±45.43

862.41+5.48
862.41±5.48394.02+17.20
394.02±17.20

898.91+0.34
898.91±0.34

395.64+79.20
395.64±79.20

3. Results and Discussion
3.1. Study of chemical composition of halophytes
Chemical composition of substrate for anaerobic digestionis essential for successful operation with anaerobic reactors.
Any plant biomass contains organic matter which can beconverted into biogas (CH4 + CO2) by anaerobic bacterial
communities. Meanwhile it is known that several organicand inorganic compounds can be toxic or inhibit microbialactivity (de Lemos Chernicharo, 2007). Many halophytes areable to accumulate significant amounts of salts in their biomass.
Therefore total organic matter and mineral content of thebiomass were investigated. Some results are presented in the
Figures and Tables below.
Investigated plants contained between 10 to 49% mineralsalts in dry matter (Table 1). Large amounts of mineralcompounds were measured in biomass of Salicornia europaea(48.6%), and the least salt accumulation among studied
halophytes was demonstrated by Karilinia caspia (about 14%
DM).
The plants in this study can be ranged in ascending order ofmineral content: Cyn<Kar<Atr<Sua<Cli b.<Cli l.<Hal<Sal.
Such high salt accumulation by plant biomass like Salicornia,
Halostachys or Climacoptera is typical for euhalophytes,
because selective uptake of sodium (and chloride) ions is oneof the important mechanisms of adaptation to living in a saline
environment.
Organic biomass is food for anaerobic bacteria, and it isdecomposed by anaerobic digestion to simple inorganic
substances as CO2 and CH4 (and H2, H2O, H2S) which areconsidered as biogas. The highest organic fractions were

233

120

mg/gDM

100
80
60
40
20
0

Sal

Hal

Cli l. Cli b.

Sua

Kar

Atr

Cyn

a)
-

- Cl
2- SO4

180
160
140

mg/gDM

120
100
80
60
40
20
0

--

Sal

Hal

Cli l.

Cli b.

Sua

Atr

Kar

Cyn

b)

Fig. 1. Content of mineral compounds in plant biomass. a) Soluble
Na+, K+ and Mg2+; b) Chlorides and sulfates. See Table 1 forplant abbreviations.

observed in biomass of Suaeda paradoxa, Atriplex nitens,
Karelinia caspia and Cynodon dactilon and ranged from about
736-900 mgVS/gDM. Organic carbon concentrations were
243.9, 337.6, 394 and 396 mgOC/gDM in these species,
respectively. Low organic carbon content (about 200
mgOC/gDM) was measured in biomasses of Salicornia,
Halostachys and Climacoptera.
Measurement of certain cations and anions in plantbiomass has shown that halophytes accumulated a fair amountof Na+, Cl- and SO42- ions (Fig. 1). It would be interesting toanalyze cation/anion content of different halophytes during
several years and by season. The results thus far show that
halophytes have much higher ion composition in comparison
with ordinary grass Cynodon dactylon which contained about 5
mg Na+/gDM. Salicornia,, Halostachys and Climacoptera
accumulated enormous amounts of Na-ions; in June 2012 it
was about 134, 135 and 116 mg/gDM, respectively. In April
2013, Salicornia accumulated 110-130 mg Na+ mg/gDM (intop part of plant) and Climacoptera accumulated 80-150
mg/gDM.
Potassium and magnesium ions play important roles inplant physiology. K+-ion contents in summer biomasses ofinvestigated plants varied from 6 to 13 mg/gDM and Mg2+
-varied from 1.3 to 5.4 mg/gDM.
Salicornia, Halostachys and Climacoptera accumulated
approximately 90-170 mg-Cl-/gDM, and large amounts ofsulfate-ions were measured in biomass of Climacoptera,
Salicornia, Halostachys and Karelinia (59.24, 37.25, 31.4 and37.2 mg/gDM, respectively). Presence of sulfate causes achange in the metabolic pathways in an anaerobic digester(AD) because of a competition for substrate establishedbetween the sulfate-reducing bacteria and fermentative,acetogenic and methanogenic microorganisms. Hence, twofinal products are formed: methane (by methanogenesis) andsulfide (by sulfate reduction). The production of sulfides may
cause serious problems during anaerobic digestion, reduce
activity of methanogens and capacity of the anaerobic reactor
for conversion of biomass into CH4.
Our previous
investigations (Akinshina, 2012) have demonstrated that it ispossible to avoid or mitigate negative effects ofsulfates/sulfides on anaerobic digestion by Fe2+ or Fe3+ (10ppm).
It should be noted that content of mineral salts in plantbiomass corresponds to the soil salinity level in the root zone
under the plants. For instance, Climacoptera lanata from thefarm trial plot in Central Kyzylkum with moderate salinity
contained fewer amounts of Na+, Cl- and SO42- in comparison
with the same plant species grown in a solonchak area. In
solonchak lands, Climacoptera lanata had Na+ content of
133-146 mg/gDM, Cl- content of 100-129 mg/gDM, and SO42content of 40-60 mg/gDM. In contrast, the same plant had
Na+ content of 84 mg/gDM, Cl- content of 55 mg/gDM, andSO42- content of 11 mg/gDM in the cultivated area of the farm
plot. The same tendency was observed for wild Karelinia
caspia grown in areas with different levels of soil salinity (Fig.
2).
- EC 0.2-1.18 mS/cm- EC 2.5-6.1 mS/cm

250

200

150

mg/gDM

+

- Na
+
-K
2+
- Mg

140

100

50

0

Ash (%)

Na

K

Cl

SO4

Karelinia caspia

Fig. 2. Mineral content of plant biomass from tested areas withdifferent soil salinity.

234

500

0

- at 35 C
0- at 55 C

600
550

450

450

Biogas yield (mL/gDM)

Biogas yield (mL/gDM)

500

400
350
300
250
200
150

350

300

250

Linear regression
y=0.498x-63.694
R=0.966

200

100
50
0

400

150

Sal

Hal

Cli

Sua

Kar

500

Atr

600

650

700

750

800

a)

Halophytes

900

950

Mesophilic conditions (35°C)

600

Biogas yield (mL/gDM)

550
500
450
400
350

Linear regression
y=15.93+0.525x
R=0.953300

3.2. Biogas production under anaerobic digestion of
halophyte biomass
Anaerobic digestion of halophyte biomasses in batch-test
mode experiments was investigated. Some findings arepresented in the Figures below.
Experimental results indicated that approximately 190-366
mL biogas (with 60% CH4) can be produced from anaerobic
digestion of 1 gDM of halophytic biomass under mesophilic
conditions (Fig. 3). It should be noted that anaerobic
digestion of the plant biomass at thermophilic conditions was
faster and about 30% more productive in comparison with thesame process at mesophilic conditions.
Anaerobic
decomposition of the biomass (at F/M = 0.2) at 55°C took
about 12-14 days, and at 35°C, it took 21-26 days; and mean
cumulative biogas yield of AD of halophytes at 55°C varied
from 289 mL/gDM (Halostachys) to 481 mL/gDM (Atriplex).
Suaeda paradoxa, Atriplex nitens and Karelinia caspia
were recognized as the most productive halophytes among
investigated plants in terms of biogas yield. With anaerobic
decomposition of the above mentioned plant biomasses, 190
mL, 366 mL, and 358 mL biogas was produced from 1 gDM
at 35°C, respectively, from these species, and 300 mL, 481 mL,
and 445 mL biogas was produced from 1 g of dry matter at
55°C, respectively.
Correlation between organic matter content (measured asVS) and cumulative biogas production at AD was very strong(Fig. 4). Thus, the experimental data on biogas production
indicate that organic fractions in halophyte biomass had quite

850

Volatile solids in plant biomass (mg/gDM)

Fig. 3. Biogas yield at anaerobic digestion of halophytes biomass.

Thus, taking into consideration that some chemical
substances in plant biomasses can reduce biogas production
and damage microbial communities of AD-reactors, it isnecessary to identify detailed chemical composition of plant
substrates before digestion, which is especially important for
halophytes.

550

250
500

550

600

650

700

750

800

850

900

Volatile solids in plant biomass (mg/gDM)b)

Thermophilic conditions (55°C)

Fig. 4. Correlation between organic matter content in plantbiomasses and biogas yield from them at anaerobic digestion.

high biodegradability under anaerobic digestion; this was about
40-60% at mesophilic temperature and 50-75% at thermophilic
conditions.

4. Conclusion
Biogas potential of halophyte biomasses (m3/ha/year) wereassessed taking into consideration information about theirbiomass yield in Central Asia and biogas production measured
in the study (Table 2). Analysis of the data showed some
unexpected findings. For instance, field data for Salicornia
europaea indicates it has very high biogas potential, but it had
the lowest biogas yield from a unit of biomass in laboratory
conditions. On the other hand, it was revealed that Karelinia
caspia has a very high biogas yield from a unit of dry biomassin laboratory experiments, but at the same time it might have avery small potential biogas production in current conditions
because of low yield of biomass.
Available information concerning utilization of halophytes
in Central Asia is presented in Table 3. Most of theinvestigated halophytes have nutritional value as forage and are235

Table 2. Biogas potential of some halophytes in Central Asia.
Biogas yield in
lab-tests(m3/t DM)

Biomass
production(tDM/ha/year)

Estimatedbiogasproduction**(m3/ha/year)

35°C

55°C

Salicornia europaea

190

330

(15-20)*(2850-3800)

Halostachysbelangeriana

215

289

1-2

215-430

Climacoptera sp.

250

315

1-1.5 (20)250 – (5000)

Suaeda paradoxa

308

443

4 (13)

1232-(4004)

Karelinia caspia

358

445

0.1-1.2

35.8-429.6

Atriplex nitens

366

481

6 (21)

2196-(7686)*Actual data from plants under cultivation/irrigation is given inparentheses.
**Calculated for mesophilic conditions (35°C).
Table 3. Current usage of some halophytes (Gintzburger, 2003).
Current use
Salicornia europaea

Forage value. Limited consumption due to high saltcontent. It is used for soda-based glassmaking andsoapmaking.

Halostachysbelangeriana

Poor value as forage. Fuelwood. S ource of potassium.
Alkaloid “halostachyn” is present.

Valuable food for sheep, goats and camels; well consumed
Climacoptera brachiata; in autumn-winter. Rehabilitation of sandy and saline
Climacoptera lanata waterlogged areas. Antioxidants (flavonoids) andglycosids are present.

Suaeda paradoxa

Forage value. Edible for sheep, goats and camels. Land
biomelioration. It is processed as a source for sodium
carbonate for use in glass-making.
Alkaloids are present.

Karelinia caspia

Poor forage, consumed a little by sheep, goats and camel inwinter. Honey plant.

Atriplex nitens

Forage value. Edible for sheep, goats and camels.

consumed by sheep, goats and camels. In addition, they canbe used as sources of valuable medicinal or some chemicalcompounds. Thus, using biomass of such halophytes forenergy may be unreasonable since they could be useful in otherways and criticisms about diverting useful plant production forbiogas use would apply.
Of the studied halophytes, only Karelinia caspia is not
currently used for food or forage because biomass of thishalophyte has very poor forage value and is recognized as
useless by local people. For this reason, it has never beencultivated before. However wild plantations of Karelinia
caspia are widespread in Central Asia, it grows to moderateheights (1.5 m), and this unpretentious perennial plant has very
high salinity resistance. Moreover, Karelinia is noted as goodhoney plant; 20-22 kg/ha of honey could be produced (Sabirov,

1972).
Thus, it is concluded that biomass of Karelinia caspia(Pall.) Less is one of the most promising sources for biogas
production in Central Asia. Wild associations of the
halophyte can be used as renewable source of alternative
energy, and it can be planted in abandoned saline arid lands for
improving and increasing their productivity. The only
drawback for this halophyte in terms of biogas production is
the high sodium and sulfate content in biomass which can
reduce the capacity of anaerobic digesters. However, this canbe remedied with the addition of Fe2+ or Fe3+ and further
research could improve the efficiency of biogas production
from this halophyte.
Acknowledgements
Work was supported by USAID-National Science Fund
(NSF) in the framework of joint project with International
Center for Biosaline Agriculture (ICBA) and University of
Nevada - Partnerships for Enhanced Engagement in Research(PEER) “Utilization of low quality water for halophytic forage
and renewable energy production”, AID-OAA-A-11-00012.

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