biogas production from two-stage anaerobic digestion of jatropha curcas ...
TRANSCRIPT
This article was downloaded by: [Erciyes University]On: 21 December 2014, At: 03:50Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registeredoffice: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Energy Sources, Part A: Recovery,Utilization, and Environmental EffectsPublication details, including instructions for authors andsubscription information:http://www.tandfonline.com/loi/ueso20
Biogas Production from Two-stageAnaerobic Digestion of Jatropha curcasSeed CakeN. Sinbuathong a b , P. Sirirote c , B. Sillapacharoenkul d , J.Munakata-Marr e & S. Chulalaksananukul fa Scientific Equipment and Research Division , Kasetsart UniversityResearch and Development Institute (KURDI), Kasetsart University ,Bangkok , Thailandb KU-Biodiesel Project, Center of Excellence for Jatropha, KasetsartUniversity , Bangkok , Thailandc Department of Microbiology, Faculty of Science , KasetsartUniversity , Bangkok , Thailandd Department of Agro-Industrial Technology, Faculty of AppliedScience , King Mongkut's University of Technology North Bangkok ,Bangkok , Thailande Civil and Environmental Engineering, Colorado School of Mines ,Golden , Colorado , USAf Department of Chemical Engineering, Faculty of Engineering ,Mahidol University, Salaya Campus , Nakornpathom , ThailandPublished online: 24 Sep 2012.
To cite this article: N. Sinbuathong , P. Sirirote , B. Sillapacharoenkul , J. Munakata-Marr & S.Chulalaksananukul (2012) Biogas Production from Two-stage Anaerobic Digestion of Jatrophacurcas Seed Cake, Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 34:22,2048-2056, DOI: 10.1080/15567036.2012.664947
To link to this article: http://dx.doi.org/10.1080/15567036.2012.664947
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the“Content”) contained in the publications on our platform. However, Taylor & Francis,our agents, and our licensors make no representations or warranties whatsoever as tothe accuracy, completeness, or suitability for any purpose of the Content. Any opinionsand views expressed in this publication are the opinions and views of the authors,and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content
should not be relied upon and should be independently verified with primary sourcesof information. Taylor and Francis shall not be liable for any losses, actions, claims,proceedings, demands, costs, expenses, damages, and other liabilities whatsoever orhowsoever caused arising directly or indirectly in connection with, in relation to or arisingout of the use of the Content.
This article may be used for research, teaching, and private study purposes. Anysubstantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions
Dow
nloa
ded
by [
Erc
iyes
Uni
vers
ity]
at 0
3:50
21
Dec
embe
r 20
14
Energy Sources, Part A, 34:2048–2056, 2012
Copyright © Taylor & Francis Group, LLC
ISSN: 1556-7036 print/1556-7230 online
DOI: 10.1080/15567036.2012.664947
Biogas Production from Two-stage Anaerobic
Digestion of Jatropha curcas Seed Cake
N. SINBUATHONG,1;2 P. SIRIROTE,3
B. SILLAPACHAROENKUL,4 J. MUNAKATA-MARR,5 and
S. CHULALAKSANANUKUL6
1Scientific Equipment and Research Division, Kasetsart University Research
and Development Institute (KURDI), Kasetsart University, Bangkok, Thailand2KU-Biodiesel Project, Center of Excellence for Jatropha, Kasetsart University,
Bangkok, Thailand3Department of Microbiology, Faculty of Science, Kasetsart University,
Bangkok, Thailand4Department of Agro-Industrial Technology, Faculty of Applied Science, King
Mongkut’s University of Technology North Bangkok, Bangkok, Thailand5Civil and Environmental Engineering, Colorado School of Mines, Golden,
Colorado, USA6Department of Chemical Engineering, Faculty of Engineering, Mahidol
University, Salaya Campus, Nakornpathom, Thailand
Abstract Digestion of Jatropha curcas seed cake was investigated in two-stage (aci-dogenic and methanogenic) anaerobic bioreactors without pH adjustment. Acidogenic
reactors were fed once daily with a slurry of 1:10 Jatropha curcas seed cake:watercontaining approximately 100 g of chemical oxygen demand/l. Organic loading rates
were 2.5, 3.3, 5, 10, and 20 kg chemical oxygen demand/m3.day, which correspondedto hydraulic retention times of 40, 30, 20, 10, and 5 days, respectively, for each
reactor stage. The maximum methane yield (340 l at STP/kg of chemical oxygendemand degraded) was observed at an organic loading rate of 3.3 kg chemical oxygen
demand/m3.day (hydraulic retention times D 30 days for each stage). At this organic
loading rate and hydraulic retention time, the chemical oxygen demand degradationefficiency was 65%. The average pH in the acidogenic and methanogenic reactors was
4.9 and 7.4, respectively. This study demonstrates high methane yield and degradationextent of Jatropha curcas seed cake in a two-stage anaerobic process without chemical
addition for pH adjustment.
Keywords agricultural waste, anaerobic digestion, bioenergy, biogas, Jatropha cur-
cas, methane, two-stage operation
Introduction
Every year in the world several million tons of agricultural wastes are disposed of through
methods, such as incineration, land application, and land filling. This global waste has a
high potential as a biorenewable energy resource and can be turned into high-value by-
Address correspondence to Dr. Nusara Sinbuathong, Scientific Equipment and ResearchDivision, Kasetsart University Research and Development Institute, Kasetsart University, Bangkok10900, Thailand. E-mail: [email protected]
2048
Dow
nloa
ded
by [
Erc
iyes
Uni
vers
ity]
at 0
3:50
21
Dec
embe
r 20
14
Anaerobic Digestion of Jatropha curcas Seed Cake 2049
products (Isci and Demirer, 2007). Jatropha curcas is a drought-resistant shrub belonging
to the family Euphorbiaceae, which is cultivated on a large scale in Central and South
America, Southeast Asia, India, and Africa (Schmook and Seralta, 1997). Jatropha curcas
seed cake is one of the agricultural wastes considered as a possible energy source. The
seed cake is a by-product of oil extraction from the seeds; the oil can be used as a
substitute for diesel after transesterification (Singh et al., 2008). With the known high
potential of Jatropha curcas for energy production, researchers have generally focused on
the production of biodiesel (Achtena et al., 2008). A few studies have investigated biogas
production from Jatropha curcas seed cake. Most of these studies were conducted using
batch operation and single stage semi-continuous operation. In general, they conclude
that Jatropha curcas seed cake is a good biogas source, due to the high conversion rates
and efficiencies obtained (Staubmann et al., 1997; Singh et al., 2008; Sinbuathong et al.,
2010, 2011).
The solids concentration of Jatropha curcas seed cake is crucial to ensure sufficient
gas production. However, high solids content may cause a system failure due to the acidic
pH of the seed cake slurry (Gunaseelan, 2009; Sinbuathong et al., 2010, 2011). In the
previous studies, the initial pH of the Jatropha curcas slurry needed to be adjusted to
neutral during the start-up period in order to prevent system failure (Sinbuathong et al.,
2010, 2011). For batch operation, the appropriate Jatropha curcas seed cake-to-water ratio
for methane (CH4) production was found to be in the range of 1:20 to 1:10 (Sinbuathong
et al., 2011). For a single-stage semi-continuous operation, the organic loading rates
(OLRs) were found to be optimal between 1.25 and 1.67 kg chemical oxygen demand
(COD)/m3.d (Sinbuathong et al., 2010). In the present study, higher OLRs were applied
to the two-stage system under the assumption that phase separation may be appropriate
for the digestion of the acidic slurry of Jatropha curcas seed cake, because acidogenic
bacteria favor an acidic aqueous environment in the first phase as described below.
The anaerobic biodegradation is carried out by three groups of bacteria: (1) hydrolytic
and fermentative bacteria, which hydrolyze the long chain molecules and ferment the
resulting monosaccharides to organic acids; (2) acetogenic bacteria, which convert these
acids to acetate, hydrogen (H2), and carbon dioxide (CO2); and (3) methanogenic bacteria,
which convert the end products of acetogenic reactions to methane (CH4) and carbon
dioxide (CO2). Several studies have proposed the physical separation of these phases
in order to increase the degradation of organic matter, improve biogas production, and
attain better control of operating conditions (Derimelk and Yenigun, 2002; Kasapgil and
Ince, 2000; O’Keefe and Chynoweth, 2000; Yu et al., 2002). The metabolic pathways
of the two-stage anaerobic digestion process are the same as those of conventional
digestion; however, they are physically separated in (1) an acidogenic stage (hydrolytic
and acetogenic stage) and (2) a methanogenic stage. The two-stage anaerobic treatment
process has several advantages over conventional processes. First, it permits the selection
and enrichment of different bacteria in each digester; in the first phase, acidogenic bacteria
degrade complex pollutants into volatile fatty acids (VFAs), which are subsequently
converted to CH4 and CO2 by acetogenic and methanogenic bacteria in the second phase.
Second, it increases the stability of the process by controlling the acidification phase in
order to prevent overloading and the build-up of toxic material. Third, the first stage
may act as a metabolic buffer, preventing pH shock to the methanogenic population;
in addition, low pH and a high OLR are all factors that favor the establishment of the
acidogenic phase.
This research experimentation was carried out in a semi-continuous, laboratory-
scale, two-reactor system operated at five different OLRs. The research objectives were
Dow
nloa
ded
by [
Erc
iyes
Uni
vers
ity]
at 0
3:50
21
Dec
embe
r 20
14
2050 N. Sinbuathong et al.
to observe the CH4 yield and the organic degradation efficiency from two-stage anaerobic
reactors and identify a method of operation that did not require addition of any chemicals
for pH adjustment.
Materials and Methods
Seed Cake Characterization
The most important parameters affecting CH4 production are the composition of feed-
stock. The analyses of the seed cake include moisture content, total solids (TS), total
volatile solids (TVS), organic carbon, organic matter, nitrogen, and phosphorous. The
moisture content of the samples was determined by oven-drying to a constant weight
at 105ıC. Total solid content was calculated as 100% � % moisture content. TVS was
obtained by igniting the TS in a muffle furnace at 550ıC. Organic carbon in the sample
was measured using the Walkley-Black method (Buurman et al., 1996; Walkley, 1947).
Organic carbon was oxidized with a mixture of potassium dichromate and sulfuric acid;
the excess potassium dichromate was titrated with ferrous sulfate. The organic matter
content of soil was indirectly estimated through multiplication of the organic carbon
content by 1.72 (Soil Science Society of America and American Society of Agronomy,
1996). Nitrogen was determined by the Kjeldahl method by digesting samples to convert
organic-N to NHC
4-N and determining NHC
4-N in the digest (Walkley, 1947). Total
phosphorous was determined by digesting samples with sulfuric acid and analyzed by an
ascorbic acid method (Rayment and Higginson, 1992).
Inoculum, Feed Solution, and Test Bioreactors
Fresh cow dung was collected and brought back to the laboratory in bags. For experi-
ments, sufficient water was added to cow dung at a ratio of 1:1 by weight to produce a
slurry. Then biomass (as mixed liquor volatile suspended solids; MLVSS) was measured
in order to start each test bioreactor with the same cell mass. Jatropha curcas seed cake
was collected from Prathumthani Province, Thailand. The seed cake was stored in a
plastic bag at room temperature and was blended prior to use.
Five sets of reactors were constructed with plastic bottles. Each set consisted of two
reactors, an acidogenic and a methanogenic reactor with a working volume of five liters
each (Figure 1). The acidogenic reactor was equipped with two outlet ports, one port for
gas venting and the other port for digested slurry, both of which fed to the methanogenic
reactor. The methanogenic reactor was connected to a gas collection system, which was
based on water displacement by the exiting gases. Sulfuric acid of 0.05 molar was used
to measure the displacement by gas in the gas collection system.
Jatropha curcas seed cake was prepared as a slurry with tap water at a ratio of
1:10 by weight. The initial COD and TVS content of this slurry were 100 and 110 g/l,
respectively. The initial pH of the seed cake slurry was 5.5 and the pH was not adjusted
during the entire period of the experiment. The conditions were 13.8 g/l MLVSS, initial
pH 5.5, and temperature 30 ˙ 1ıC.
Two-Stage Operation
Each bioreactor was filled with a liter of mixture of the culture that contained 13.8 g
MLVSS/l. Initially, the Jatropha curcas seed cake slurry was added to the acidogenic
Dow
nloa
ded
by [
Erc
iyes
Uni
vers
ity]
at 0
3:50
21
Dec
embe
r 20
14
Anaerobic Digestion of Jatropha curcas Seed Cake 2051
Figure 1. Two-stage experiment set up; reactors I and II were acidogenic and methanogenic
reactors, respectively. (color figure available online)
reactor at a rate of 2 liters/day for 2 days. This acidogenic reactor was operated for 2
days in a batch mode before feeding with the Jatropha curcas seed cake slurry semi-
continuously in an upflow mode by feeding once per day at a feed rate of 1,000, 500,
250, 167, and 125 ml/day in each set of reactors, giving rise to OLRs of 20, 10, 5,
3.3, and 2.5 kg COD/m3.day and the corresponding increasing hydraulic retention times
(HRTs) of 5, 10, 20, 30, and 40 days in both acidogenic and methanogenic reactors. The
ambient temperature of all reactors was 30 ˙ 1ıC and the reactors functioned without
pH control. When the system reached steady state, the total gas production was recorded
(at room temperature) daily and the CH4 content was determined by a Shimadzu GC-
14B gas chromatograph equipped with a thermal conductivity detector. The CH4 volumes
were then adjusted to standard temperature and pressure (STP). The operating period was
approximately 100 days. The digested slurry from the methanogenic reactor was analyzed
for COD, TVS, and pH according to the procedure of the Standard Methods (APHA,
AWWA, and WEF, 2005). All experiments were conducted in duplicate and the results
were calculated using the mean of the experimental values. Organic waste degradation
(in terms of COD and TVS degradation) and CH4 production from the system at various
OLRs were used as indicators of reactor performance. The CH4 yield was calculated and
reported in terms of CH4 produced/kg COD (and kg TVS) degraded and CH4 produced/kg
seed cake added to the reactor.
Results and Discussion
The most important factors impacting biogas production are the composition and quantity
of substrate. Both parameters were influenced by the substrate used and the OLR applied.
In this study, analysis of the seed cake showed that it had 8.8% moisture, 91.2% TS, of
which 82% was TVS. The cake was fairly high in organic matter (68.9%) and, therefore,
Dow
nloa
ded
by [
Erc
iyes
Uni
vers
ity]
at 0
3:50
21
Dec
embe
r 20
14
2052 N. Sinbuathong et al.
Table 1
Performance data of two-stage anaerobic digestion of Jatropha curcas seed cake at
various organic loading rates
Organic loading rate,
kg COD/m3.day
Parameters 2.5 3.3 5 10 20
HRT (days) for each acidogenic and
methanogenic reactor
40 30 20 10 5
Reactor volume (ml) for each
acidogenic and methanogenic
reactor
5,000 5,000 5,000 5,000 5,000
Daily feed (ml slurry/day) 125 167 250 500 1,000
Initial COD (g/l) 100 100 100 100 100
COD at steady state (g/l) 34.2 35.4 51.5 86 85.5
COD degradation efficiency (%) 66 65 48.5 14 14
Initial TVS (g/l) 110 110 110 110 110
TVS at steady state (g/l) 27.6 27.9 38.4 52.0 56.0
TVS degradation efficiency (%) 75 75 65 53 49
Initial pH of the slurry 5.5 5.5 5.5 5.5 5.5
Average pH of acidogenic reactor at
steady state
4.9 4.9 4.8 4.7 4.7
Average pH of methanogenic
reactor at steady state
7.4 7.4 7.0 4.8 4.8
Average CH4 (%) 63 62 61 11 9
CH4 production (ml at STP/day) 2,740 3,680 3,660 175 140
CH4 production rate (ml at
STP/liter.day)
550 736 732 35 28
CH4 yield (liter at STP/kg COD
degraded)
333 340 302 25.4 9.6
CH4 yield (liter at STP/kg TVS
degraded)
265 267 203 6 2.5
CH4 yield (liter at STP/ kg seed
cake added)
240 242 161 4 2
had good potential for biogas generation. The C and N contents were 39.9 and 3.3%,
respectively; thus, the C/N ratio was 12. The results of the digester performance in
terms of organic waste reduction and biogas production at various OLRs are shown in
Table 1.
Organic Waste Reduction
In this study, COD and TVS were used to quantify the organic strength of the waste.
Initial COD and TVS as well as the average COD and TVS of each reactor at steady
state period are as reported in Table 1. Organic waste degradation efficiency at various
OLRs is calculated and shown in Figure 2. The general trend showed a decrease of COD
Dow
nloa
ded
by [
Erc
iyes
Uni
vers
ity]
at 0
3:50
21
Dec
embe
r 20
14
Anaerobic Digestion of Jatropha curcas Seed Cake 2053
Figure 2. COD and TVS degradation efficiency at various OLRs.
and TVS degradation efficiency with increased loading (Figure 2). An increase in OLR
from 3.3 to 20 kg COD/m3.day resulted in a decrease in COD and TVS degradation
efficiency (Figure 2 and Table 1). Increasing OLR, corresponding with decreasing HRT,
resulted in reduction of the reactor performance (Figure 2 and Table 1). However, the
reactor performance at OLR of 2.5 kg COD/m3.day is quite comparable with that at the
OLR of 3.3 kg COD/m3.day.
Reactor pH
The average pH of the slurry in both the acidogenic and methanogenic reactors of various
OLRs at steady state is shown in Figure 3. In the reactors that received OLRs of 2.5, 3.3,
and 5 kg COD/m3.day, phase separation was achieved, as evidenced by the average pH
in the acidogenic and methanogenic reactor of 4.9 and 7.3, respectively (Figure 3). These
pH values indicate the good performance of the acidogenic and methanogenic reactors.
On the other hand, in the reactors that received the OLRs of 10 and 20 kg COD/m3.day,
the environment in both reactors remained acidic. The average pH in the acidogenic and
methanogenic reactor was 4.7 and 4.8, respectively (Figure 3 and Table 1). At these higher
loading rates, the lower treatment efficiency and CH4 production were probably caused
Figure 3. pH in acidogenic and methanogenic reactors that received various OLRs during the
steady state.
Dow
nloa
ded
by [
Erc
iyes
Uni
vers
ity]
at 0
3:50
21
Dec
embe
r 20
14
2054 N. Sinbuathong et al.
by accumulation of VFAs (because of acidic pH). This suggests that phase separation
of acidogenesis and methanogenesis was not achieved in the two reactors at these high
OLRs.
Biogas Production
Differences in the CH4 production at each OLR were observed. When the OLRs were
in the range of 2.5–5 kg COD/m3.day, the CH4 content was acceptably high (61–63%
CH4) (Table 1) but at OLRs 10 and 20 kg COD/m3.day, the reactors fed with the slurry
of Jatropha curcas seed cake produced biogas with much lower CH4 content (11 and 9%
CH4) (Table 1).
The CH4 production rate is shown in Table 1. In this study, with increasing OLRs
from 3.3 to 20 kg COD/m3.day, the CH4 production rate decreased, reaching a maximum
at OLR of 3.3 kg COD/m3.day (736 ml at STP/liter.day) with an average CH4 content
of 62% CH4 (Table 1). This is probably due to the system containing too concentrated
organic substrate at OLR of 10 and 20 kg COD/m3.day, so it cannot convert VFAs to CH4
as rapidly as they form, causing the pH to drop and resulting in lower CH4 production.
At 2.5 kg COD/m3.day, the CH4 production rate was lower (550 ml at STP/liter.day).
When the system contained less organic substrate (OLR 2.5 kg COD/m3.day) than the
optimum concentration (OLR 3.3 kg COD/m3.day), the CH4 production rate was likely
lower because readily transformed carbon sources were depleted at the lowest OLR.
Methane Yield
Based on the CH4 production and organic waste degraded, CH4 yield obtained at various
OLRs was calculated. The digester performance at various OLRs is summarized in
Table 1. The CH4 production yield reached a maximum value of 340 liters at STP/kg of
COD degraded (267 liters at STP/kg of TVS degraded or 242 liters at STP/kg seed cake
added) at the OLR of 3.3 kg COD/m3.day and significantly dropped at OLRs of 10 and 20
kg COD/m3.day. In this study, the two-stage anaerobic digestion of Jatropha curcas seed
cake without external pH control at 10 and 20 kg COD/m3.day was not feasible because
of the low CH4 yield (25.4 and 9.6 liters at STP/kg of COD degraded, respectively, or
6 and 2.5 liters at STP/kg of TVS degraded, respectively). The reactor performance of
Jatropha curcas seed cake digestion could be improved by lowering OLRs (or increasing
HRTs).
A previous study reported that the CH4 yield from de-oiled cake of Jatropha curcas
by biochemical methane potential assay was 230 liters/kg TVS added (Gunaseelan, 2009).
Singh et al. (2008) studied the biogas generation from Jatropha curcas seed cake digestion
in a single-stage operation; 333 liters of gas were produced per kg seed cake added,
which contained 66% CH4, resulting in a CH4 yield of 220 liters/kg Jatropha curcas
seed cake added. From this current study, the CH4 yield from the two-stage operation
of Jatropha curcas seed cake digestion at optimum OLR of 3.3 kg COD/m3.day is 242
liters at STP/kg seed cake added (Table 1), higher than the CH4 yield obtained from
a single-stage from their study. In the current study, the COD degradation efficiencies
were 65%, while the average pH of the digested slurry was 7.4 under the conditions
used. Sinbuathong et al. (2010) reported that for the single-stage anaerobic digestion of
Jatropha curcas seed cake with chemical pH control, an optimal CH4 yield of 340 liters
at STP/kg COD degraded was obtained at an OLR of 1.25 kg COD/m3.day. Compared
with the current study, the optimal OLR of Jatropha curcas seed cake applied in the
Dow
nloa
ded
by [
Erc
iyes
Uni
vers
ity]
at 0
3:50
21
Dec
embe
r 20
14
Anaerobic Digestion of Jatropha curcas Seed Cake 2055
two-stage anaerobic reactor system was 2.6 times (3.3/1.25) higher than that applied to a
single-stage anaerobic reactor, and the two-stage reactor functioned without external pH
adjustment.
The advantages of the single-stage anaerobic system are that it has only one reactor
and is easier to operate. The two-stage set-up used is suitable for anaerobic digestion of
Jatropha curcas seed cake, enabling better conditions for the methanogenic phase and
allowing a high organic loading rate of Jatropha curcas seed cake. However, specific care
must be taken in transferring the slurry from the acidogenic reactor to the methanogenic
reactor because the high solids content can cause blockage of pipes. The two-stage
digestion of high solids content is technically more complex and requires a higher
capital investment. For the reasons described above, when comparing the two-stage semi-
continuous digestion system with the single-stage batch digestion for Jatropha curcas
seed cake, the advantage of single-stage batch digestion is its technical simplicity and
portability. In single-stage batch digestion, the plant solids do not need to flow through
pipes, because the reactor is loaded once and only discharged at the end of the anaerobic
process. The tank is opened, old slurry is removed, and the new charge is added. The tank
is then resealed and ready for operation. However, both batch digestion and single-stage
semi-continuous digestion of Jatropha curcas seed cake need pH adjustment. As for the
two-stage digestion system, if the system is managed properly with the recommended
OLRs, the digester can function without external pH adjustment, and it can generate high
CH4 production and high extent of organic waste degradation.
Conclusion
Two-stage anaerobic digestion improves the digestion of Jatropha curcas seed cake by
having separate reactors for the acidogenic and methanogenic stages, thus providing
flexibility to optimize each of these reactions. The system can be operated with an
acidic slurry of the Jatropha curcas seed cake at a high organic loading rate without
external pH control at OLR less than 5 kg COD/m3.day, which provides a stable system
and high methane yield. The system reached maximum efficiency at the OLR of 3.3
kg COD/m3.day. The methane production rate, the methane content of the biogas, and
the methane yield were satisfactorily high. The COD degradation efficiencies were
approximately 65%, while the digested slurry pH was just over 7.
Acknowledgments
This research is part of the KU-Biodiesel Project and was supported by Kasetsart Uni-
versity Research and Development Institute (KURDI), Kasetsart University, Bangkok,
Thailand and Toray Science Foundation (TSF), Japan.
References
Achtena, W. M. J., Verchotb, L., Frankenc, Y. J., Mathijsd, E., Singhe, V. P., Aertsa, R., and Muysa,
B. 2008. Jatropha bio-diesel production and use. Biomass & Bioenergy 32:1063–1084.
APHA, AWWA, and WEF. 2005. Standard Methods for the Examination of Water and Wastewater,
21st ed. Washington, DC: American Public Health Administration.
Buurman, P., Lagen, B. V., and Velthorst, E. J. 1996. Manual for Soil and Water Analysis. Leiden,
the Netherlands: Backhuys Publishers, p. 14.
Derimelk, B., and Yenigun, O. 2002. Two-phase anaerobic digestion processes. J. Chem. Technol.
& Biotechnol. 10:743–755.
Dow
nloa
ded
by [
Erc
iyes
Uni
vers
ity]
at 0
3:50
21
Dec
embe
r 20
14
2056 N. Sinbuathong et al.
Gunaseelan, V. N. 2009. Biomass estimates, characteristics, biochemical methane potential, kinetics
and energy flow from Jatropha curcus on dry lands. Biomass & Bioenergy 33:589–596.
Isci, A., and Demirer, G. N. 2007. Biogas production potential from cotton wastes. Renew. Energy
32:750–757.
Kasapgil, B., and Ince, O. 2000. Changes to bacterial community make-up in a two-phase anaerobic
digestion system. J. Chem. Technol. & Biotechnol. 75:500–508.
O’Keefe, D., and Chynoweth, D. 2000. Influence of phase separation, leachate and aeration on
treatment of municipal solid waste in simulated landfill cells. Biores. Technol. 72:55–66.
Rayment, G. E., and Higginson, F. R. 1992. Australian Laboratory Handbook of Soil and Water
Chemical Methods. Melbourne/Sydney, Australia: Inkata Press, p. 71.
Schmook, B., and Seralta, P. L. 1997. J. curcas: Distribution and uses in the Yucatan Peninsula of
Mexico. In: Biofuels and Industrial Products from Jatropha Curcas, Gubitz, G. M., Mittelbach,
M., and Trabi, M. (Eds.). Graz, Austria: DBV, pp. 53–57.
Sinbuathong, N., Munakata-Marr, J., Sillapacharoenkul, B., and Chulalaksananukul, S. 2011. Effect
of the solid content on biogas production from Jatropha curcas seed cake. Int. J. Global Warm.
3:403–416.
Sinbuathong, N., Sillapacharoenkul, B., Khun-Anake, R., and Watts, D. 2010. Optimum organic
loading rate for semi-continuous operation of an anaerobic process for biogas production from
Jatropha curcas seed cake. Int. J. Global Warm. 2:179–188.
Singh, R. N., Vyas, D. K., Srivastava, N. S. L., and Narra, M. 2008. SPRERI experience on holistic
approach to utilize all parts of Jatropha curcas fruit for energy. Renew. Energy 33:1868–1873.
Soil Science Society of America, Inc. and American Society of Agronomy, Inc. 1996. Soil Testing
and Plant Analysis No. 3. Methods of Soil Analysis: Chemical Methods, Part 3. In: Sparks,
D. L. (Ed.) and Bartels, J. M. (Managing Ed.). Soil Science Society of America, Inc. and
American Society of Agronomy, Inc. Madison, Wisconsin, p. 1001.
Staubmann, R., Foidl, G., Foidl, N., Gubitz, G. M., Lafferty, R. M., Arbizu, V. M. V., and Steiner, W.
1997. Biogas production from Jatropha curcas press-cake. Appl. Biochem. Biotech. 63:457–
467.
Walkley, A. 1947. A critical examination of rapid method for determination organic carbon in
soils—Effect of variations in digestions conditions and of inorganic soil constituents. Soil Sci.
63:251–264.
Yu, H., Samani, Z., Hanson, A., and Smith, G. 2002. Energy recovery from grass using two-phase
anaerobic digestion. Waste Manage. 22:1–5.
Dow
nloa
ded
by [
Erc
iyes
Uni
vers
ity]
at 0
3:50
21
Dec
embe
r 20
14