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High Solid Anaerobic Co-digestion of Household Organic Waste with Cow Manure

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Nuruljannah Khairuddin at Universiti Putra Malaysia
Nuruljannah Khairuddin
Latifah Abd Manaf at Universiti Putra Malaysia
Latifah Abd Manaf
Normala Halimoon at Universiti Putra Malaysia
Normala Halimoon
Wan Azlina Wan Ab Karim Ghani at Universiti Putra Malaysia
Wan Azlina Wan Ab Karim Ghani
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Abstract and Figures

Different mixture ratio of household organic waste (HOW) and cow manure (CM) were investigated for biogas production. The objective was to explore possible significant synergistic effect obtained from the combination of these different substrates in Reactor 1 – 4 (R1 – 4) batch experiment. The highest methane yield, 247mL/g VS was obtained from R3 and 243mL/g VS in R4. Co-digestion in R4 increased to 9% for CM and 78% for HOW in methane production. The results clearly demonstrate synergistic effect from nutrient balanced that improves the stability of anaerobic process.
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Procedia Environmental Sciences 30 ( 2015 ) 174 – 179
1878-0296 © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of organizing committee of Environmental Forensics Research Centre, Faculty of Environmental Studies,
Universiti Putra Malaysia.
doi: 10.1016/j.proenv.2015.10.031
Available online at www.sciencedirect.com
ScienceDirect
International Conference on Environmental Forensics 2015 (iENFORCE2015)
High solid anaerobic co-digestion of household organic waste with
cow manure
Nuruljannah Khairuddina,
*
, Latifah Abd Manafa, Normala Halimoona, Wan Azlina Wan
Abdul Karim Ghanib, Mohd Ali Hassanc,
a Department of Environmental Sciences, Faculty of Environmental Studies, Universiti Putra Malaysia, 43400 UPM Serdang, Malaysia
bDepartment of Environmental Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM Serdang, Malalysia
cDepartment of Bioprocess Technology and Bimolecular Sciences, Universiti Putra Malaysia, 43400 UPM Serdang, Malaysia
Abstract
Different mixture ratio of household organic waste (HOW) and cow manure (CM) were investigated for biogas production. The
objective was to explore possible significant synergistic effect obtained from the combination of these different substrates in
Reactor 1 – 4 (R1 – 4) batch experiment. The highest methane yield, 247 mL/g VS was obtained from R3 and 243 mL/g VS in R4.
Co-digestion in R4 increased to 9% for CM and 78% for HOW in methane production. The results clearly demonstrate
synergistic effect from nutrient balanced that improves the stability of anaerobic process.
© 2015 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of organizing committee of Environmental Forensics Research Centre, Faculty of
Environmental Studies, Universiti Putra Malaysia.
Keywords: Biomethane potential; biodegradability; anaerobic co-digestion; high solid
1. Introduction
Anaerobic digestion is one of the promising technologies in order to ensure betterment in landfill management. In
fact, anaerobic digestion produce biogas which is can be potential renewable energy source, energy recovery and
nutrient soil replacement through digestate composting. However, the process is sensitive and prone to failure [1].
The degradation of macromolecules in organic fraction of substrate resulting accumulation of volatile fatty acid
(VFA) reduced the pH value. This limiting step in anaerobic digestion is known as hydrolysis step. Anaerobic
* Corresponding author. Tel.:+6011-10720301
E-mail address: jannah.env@gmail.com
© 2015 The Authors. Published by Elsevier B.V This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of organizing committee of Environmental Forensics Research Centre, Faculty of Environmental Studies,
Universiti Putra Malaysia.
175
Nuruljannah Khairuddin et al. / Procedia Environmental Sciences 30 ( 2015 ) 174 – 179
digestion (AD) was found to be unstable when the household organic waste and cow manure were used as sole-
substrate due to low C/N ratio [2]. Co-digestion of organic fraction with other organic waste has been proposed as a
solution to these problems. Co-digestion promoting a better nutritional supply and reducing the limiting element in
anaerobic digestion such as ammonia and lipid. Another advantage is that, the residue from co-digestion may
enhance the performance of the anaerobic digestion. However, co-digestion substrates should be selected to prevent
adverse effects during the digestion process such as lowering the pH value and accumulation of toxic substance such
as ammonia [3]. On the other hand, high solid anaerobic digestion also known as dry anaerobic digestion; is
preferable due it minimal pre-treatment and added water [4]. High anaerobic co-digestion enhances the stability of
the digestion process and produced more stable biogas production [4]. However more information is required to
understand the mechanism involved in the process and to maintain to the optimal value for the maximum production.
Hence, this present work was designed to evaluate the significant synergistic effects from high soli d anaerobic co-
digestion of household organic waste and cow manure. This paper also seeks to measure the performance of
designed batch experiment of present work.
2. Materials and methods
2.1. Preparation of Substrate
Samples were collected from household organic waste (HOW) mainly food wastes, manually sorted and
shredded using laboratory blender. Water was added to desire total solid content (TS = 15%) and keep frozen (4oC).
Cow manure (CM) was sampled from Universiti Putra Malaysia (UPM) agricultural park. The sample was stored in
4oC to prevent organic decomposition until required prior to experiment. Due to high TS content (15.2%) water was
added to 5% of TS content. Anaerobic inoculum used in this study was supplied by SP Multitech (SP Multitech
Renewable Energy Sdn Bhd). The inoculum were thermophilic (55oC) treated in air-tight reactor before introduced
to the feedstock. The compositions of the feed for household organic waste, cow manure and inoculum are
summarised in Table 1.
Table 1 Characteristics of feedstock and inoculums
Parameter
HOW
CM
Inoculum
pH
5.3
7.5
8.3
TS (%)
40.4
15.2
26.3
VS (%)
30.6
13.8
22.5
Moisture Content (%)
84.5
50.4
44.0
C:N
11.0
11.2
25.3
Ammonia (g/L)
4.3
26.88
14.8
2.2. Experimental Design and Operation
Batch experiments were constructed to evaluate the performance of high solid anaerobic co-digestion on
household organic waste and cow manure. The assay was operated in four different mixture ratio (HOW/CM) on
w/w basis in 1 L Schott bottles with total working volume of 800 mL in cooperated with 3 separated ports (pH
adjustment, biogas measurement and biogas collection). All bottles were sealed with Teflon hermetic caps, flushed
with a N2 atmosphere and incubated in thermophilic condition (55 ± 1oC). The experimental design and scheme is
explained as in Table 2.
176 Nuruljannah Khairuddin et al. / Procedia Environmental Sciences 30 ( 2015 ) 174 – 179
Table 2 Batch Experimental Design and Scheme of Feedstock and Inoculum
Reactor
Feedstock
Inoculum (mL)
CM (mL, 5%TS)
R1
760
40
R2
-
40
R3
380
40
R4
254
40
The biogas was measured according to standard temperature and pressure (STP) by water displacement method.
Qualitative characterisation of biogas; methane (CH4) and carbon dioxide (CO2) analyses was carried out by gas
chromatography separation (6890N Agilent Technologies, CA, USA) with thermal conductivity detector (GC-TCD),
equipped with a Hay sep N 80/100, a molecular sieve column (5A 60/100). Argon (Ar) was used as carrier gas at a
flow rate of 12mL/min. The injector, oven and detector temperatures were 105oC, 60oC and 150oC. CH4 generation
yield were normalised by correcting the gas volume to normal conditions (0oC, 101.325 kPa). The samples were
measured daily during first until third weeks of the experiment and weekly for the following weeks.
2.3. Analytical Procedures
Analytical characterisation were analysed to monitor total solids (TS), volatile solids (VS), alkalinity, total
nitrogen (TKN), chemical oxygen demand (COD) and ammonium nitrogen (ସ
ା-N) according to Standard Methods
[5]. Additionally, to estimate theoretical biogas yield high solid anaerobic co-digestion of HOW and CM, an
elemental analysis was conducted using LECO-CHNS-932 analyser.
2.4. Theoretical Methane Yield (TMY), Biodegradability (BD) and Relative Error (E)
The theoretical methane yield (TMY) was calculated by taking into account the elements of C, H, O and N of
the waste composition considering total degradation. The assessments are basically is estimated using stoichiometric
equation as expressed as in equation (1), based on Buswell formula [6, 7, 8].
TMY (௠௅஼ுర
௚௏ௌ ) = ቀೌ
మା್
ఴି೎
రିయ೏
ఴି೐
రቁൈଶଶସ଴଴
ሺଵଶ௔ା௕ାଵ଺௖ାଵସௗାଷଶ௘ሻ (1)
Where a, is the number of atoms of carbon; b is the number of atoms of hydrogen; c is the number of atoms of
oxygen; d is the number of atoms of nitrogen; e is the number of atoms of sulphur.
Once the digestion had finished the biodegradability of the substrates where analysed in order to evaluate the level
of anaerobic biodegradability. Experimental biodegradability (BDexp) was measured using initial and final volatile
solids (VSi and VSf) as presented in equation (2) [9, 10].
BDexp (%) =ሺ௏ௌ೔ି௏ௌ೑
௏ௌ೔) × 100 (2)
Relative error (RE) were calculated (equation 4) [10] to evaluate the stability of the CH4 production based on EMY
and TMY measurement with the adjustment of the experimental TMYBD (equation 3) [10].
TMYBD (௠௅஼ுర
௚௏ௌ ) = BDexp × TMY (3)
RE (%) = ாெ௒ି்ெ௒ಳವ
ாெ௒ (4)
177
Nuruljannah Khairuddin et al. / Procedia Environmental Sciences 30 ( 2015 ) 174 – 179
2.5. Synergistic Effects
Theoretical methane yield may predict the methane production from experimental process. Concurrently the
presence of different types of residues in anaerobic co-digestion, enhance the process to produce higher methane
yield compare to sole digestion methane production [11]. This is due to the significant of synergistic interactions on
co-digestion. The heterogeneity in substrate composition provides essential nutrients to stimulate anaerobic
degradation. The synergistic effect during the co-digestion was investigated according to equation 5 [10, 12].
α = ஼௢ିௗ௜௚௘௦௧௜௢௡௠௘௧௛௔௡௘௬௜௘௟ௗ
௦௢௟௘ିௗ௜௚௘௦௧௜௢௡௠௘௧௛௔௡௘௬௜௘௟ௗ (5)
The co-digestion experiment is the value from experimental methane yield for each co-digestion while sole
digestion is the experimental methane yield from sole-digestion (HOW). The interactions can be interprets as
follow:
α > 1; the mixture has synergistic effect in the final products, α = 1; the substrate work independently from the
mixture,
α < 1; the mixture has the competitive effect in the final products.
3. Results
3.1. Stability of High Solid Anaerobic Co-digestion
The main properties of individual reactors (R1, R2, R3 and R4) that describe psycho-chemical characteristics are
summarised as in Table 3. The degradation of VS in organic substrate promotes significant contribution on methane
yield in anaerobic digestion. In addition, higher organic elimination (TSinitial – TSfinal) indicates the treatment
efficiency of the treatment process. The current study agreed that more than 70% of organic elimination meets
almost 70 – 80% of treatment effectiveness. From elemental analyses, anaerobic digestion influence to several
improvements in digested composition which is essential for field application [13]. The information on psycho-
chemical properties of feedstock of each functioning reactor is substantial to determine methane yields and
describing the performance of anaerobic digestion. The measurement of essential elements such as macromolecules
(N, P and K) is important as added value of the digestate. Almost 5 – 30% of nitrogen content increase from each
reactor. However, there are no significant of AD on phosphorus (P) availability in digestate (0.01 1.00%). The
mineralisation stage during AD accumulates with suspended solid lead to precipitation of P [14]. Moreover, the
highest increment of potassium (K) content in digestate was observed in R2 (33%) followed by R3 (4.34%), R1
(2.36%) and R4 (2.1%).
Table 3 Average Value Psycho-chemical characteristics of Initial and Final Substrate
Parameter
Initial Substrate
Final Substrate
R1
R2
R3
R4
R1
R2
R3
R4
pH
7.8
5.5
6.8
7.1
7.2
4.5
6.5
6.9
TS (mg/kg)
20
20
20
20
8.1
13
7.5
8
VS (mg/kg)
50.4
73.5
48.3
44.1
10.1
24
11.0
12.7
Moisture Content (%)
64.3
70
70.1
75.2
43
44
47.2
53.0
COD (mg/L)
6879
10587
7380
6541
5000
2500
3500
3500
C:N
11.2
24.5
14.3
18.2
5.4
8.1
9.6
13.0
Total C (%)
35.4
59.2
47.3
46.4
-
-
-
-
Total N (%)
Total H (%)
Total O (%)
14
6.3
33.7
5.4
9.4
17.7
8.9
7.8
20.1
6.3
8.3
25.7
18
-
-
5
-
-
10.2
-
-
7.4
-
-
Total S (%)
-
-
0.7
0.5
-
-
-
-
Total P (%)
0.18
0.52
0.27
0.41
0.18
0.52
0.3
0.4
Total K (%)
1.27
0.9
2.3
1.4
1.30
0.61
2.2
1.7
178 Nuruljannah Khairuddin et al. / Procedia Environmental Sciences 30 ( 2015 ) 174 – 179
3.2. Experimental and Theoretical Methane Yield
The experimental results were obtained after a period of 40 days when the batch assays ended with a methane
production less than 1%. Fig. 1 shows the daily production during experiments for the sole substrates (HOW and
CM) and each of the co-digestion mixtures. Methane production in R4 is the highest (247 mL CH4/g VS) followed
by R3 (243.75 mL/g VS). All these mixtures obtained higher values than the sole substrate in R 1 (CM) and R2
(HOW) with 223 mL/g VS, 54 mL/g VS respectively. Co-digestion in R4 increased 9% for CM and 78% for HOW
in methane production. The CH4 content is varied between 50 – 75 % for R1, R3 and R4. From Fig.1 R1 produce high
methane production within 10 days operation. However, R2 was completely halt and the process fault at day- 14
with CH4 content <10%. Anaerobic co-digestion may enhance the stability of the anaerobic process because of a
better carbon to nitrogen (C/N) balance [15]. The variation in the CH4 production in the reactors was likely due to
changing composition of the substrate [16].
Fig. 1 Daily Methane Production of High Solid Anaerobic Co-digestion of HOW and CM
The potential of theoretical methodology to precisely estimate methane yield of anaerobic co-digestion was
evaluated by comparing the EMY with TMY. Table 4 represent the experimental production (EMY),
Biodegradability (BDexp) and the theoretical estimation was corrected using the experimental biodegradability
(TMYBD). Relative error (RE) is measured from equation 4 by comparing EMY and TMYBD. The methane yield
from experimental process gets agreement more than 90% to the theoretical methane yield estimation for R3 and R4.
Adopting the biodegradability of the experimental, preventing the methane production from co-digestion exceed the
production from sole-digestion. The results showed different behaviour for R1 and R2 (sole-digestion) indicates that
the synergistic effects is significant on anaerobic co-digestion. Overall, it is ascertainable that theoretical estimation
methods based on stoichiometric composition with biodegradability values are potentials to evaluate specific
methane yield with lower error (R3 and R4).
Table 4 Methane Yield from Experimental and Theoretical Measurement and biodegradability
Reactor
Experimental Measurement
Theoretical Measurement
RE (%)
EMY (mL/g VS)
BDexp (%)
TMY (mL/g VS)
TMYBD (mL/g
VS)
R1
223
59.5
232.3
137.5
38.3
R2
54
67.3
505.2
340.3
-530.2
R3
247
77.2
345.2
266.5
7.9
R4
243
71.2
317.7
226.2
6.9
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
0510 15 20 25 30 35 40 45 50
Daily methane yeild (mL/day)
Time (days)
Reactor 1
Reactor 2
Reactor 3
Reactor 4
179
Nuruljannah Khairuddin et al. / Procedia Environmental Sciences 30 ( 2015 ) 174 – 179
3.3. Synergistic Effects on High Solid Anaerobic Co-digestion
Anaerobic co-digestion in several combination of waste influences the biogas yield, process stability and the
degradation. Anaerobic co-digestion can induced synergistic or antagonistic effect along the degradation process.
The synergism can be explained as the increase in methane yield for co-digestion samples over sole-digestion.
Whereas antagonism is understood as affect that caused decreases in methane yield in the co-digestion. The
synergistic and antagonistic effect from this study where calculate according to equation 5. From the result, the
optimum ratio for higher methane yield was 1:1 in R3 (α = 4.6) followed by R4 (α = 4.5). Hence, it is agreed that
anaerobic co-digestion promote enhancement in treating organic waste fraction.
4. Conclusion
The experimental results indicate that all the co-digestion reactors (R3 and R4) have higher methane production
from the sole digestion (R1 and R2). These finding support the synergism effect on high solid anaerobic co-digestion.
Acknowledgements
This study was financially supported by the Ministry of Science and Technology (MOSTI) of Malaysia and
Universiti Putra Malaysia for providing laboratory facilities under project no. 06-01-04-SF1514.
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Full-text available
  • Jan 2023
The increase in population and industrialization leads to an increase in the solid waste year by year. The limited availability, increasing cost and adverse effect of climate change on fossil fuel leads to encouraging the research in the field of finding alternatives for energy sources. The organic fraction of municipal solid waste (OFMSW) can be utilized as a bio-energy source, which reduces the environmental impact and the requirement of landfill areas to dispose of municipal solid waste. Anaerobic digestion is the widely used sustainable approach to treat OFMSW. In recent years, the generation of methane from municipal solid waste has received increasing attention in research. This paper reviews literature published in recent years considering various characteristics of input feedstock parameters like pH, total solids, volatile solids, and water content which affect the digestion quality of the OFMSW and increase the production of methane. A regression model is developed to identify the relationship between methane production and various feedstock parameters. When the chemical compositions of feedstock were used as independent variables, the percentage variation accounted for by the model is low (r2 = 0.63) and also the important observation from the analysis is that the pH of the feedstock influences majorly methane production.
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A comprehensive review on food waste anaerobic co-digestion: Research progress and tendencies
Article
  • Mar 2023
  • SCI TOTAL ENVIRON
Food waste (FW) anaerobic digestion systems are prone to imbalance during long-term operation, and the imbalance mechanism is complex. Anaerobic co-digestion (AcoD) of FW and other substrates can overcome the performance limitations of single digestion, allowing for the mutual use of multiple wastes and resource recovery. Research on the AcoD of FW has been widely conducted and successfully applied to a practical engineering scale. Therefore, this review describes the research progress of AcoD of FW with other substrates. By analyzing the problems and challenges faced by AcoD of FW, the synergistic effects and influencing factors of different biomass wastes are discussed, and improvement strategies to improve the performance of AcoD of FW are summarized from different reaction stages of anaerobic digestion. By combing the research progress of AcoD of FW, it provides a reference for the optimization and improvement of the performance of the co-digestion system.
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Ni(II) and Co(II) effects on the anaerobic digestion of livestock manure and bi-logistic function model- prediction of biogas production
Article
Full-text available
  • Mar 2021
This study evaluated the effects of Ni(II) and Co(II) on the anaerobic digestion of livestock manure, and bi-logistic function model-prediction of biogas production. The characteristics of the cow dung (CD) and poultry manure (PM) were estimated by standard methods. Batch system anaerobic digesters were operated for 50 days under mesophilic conditions, both with and without Co(II) and Ni(II) supplementation at concentration ranges of 0.02-0.1 mM. The CD and PM possess characteristics suitable for biogas production. Co(II) was found to exhibit a stimulatory effect at all the concentrations tested, the highest biogas yield being at 0.5mM (19.91%). Ni(II) was stimulatory at 0.02 and 0.05mM, with 5.60 and 13.51% increase in gas production respectively, whereas 0.1mM inhibited biogas yield. The result indicates that Co(II) is more effective in improving biogas yield than Ni(II). The Kinetic study also revealed that the bi-logistic function equation suitably fitted the experimental data, with a correlation coefficient > 0.999, indicative of a proper description of AD and biogas production process. The stimulatory effect of Ni(II) and Co(II) and some other trace elements is an advantage that could be exploited in the improvement of anaerobic digestion and biogas production from agro-wastes.
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Anaerobic digestion of food waste for bio-energy production in China and Southeast Asia: A review
Article
  • Nov 2020
  • RENEW SUST ENERG REV
Rapid economic growth in Asia and especially in China, will lead to a huge increase of food waste (FW) production that is expected to increase by 278–416 million tonnes. Among various waste management practices, anaerobic digestion (AD) is a useful method to transform food waste, producing renewable energy/biofuel and bio-fertilizers. This review aims to investigate some of the key factors in proposing FW for anaerobic digestion, with particular reference to China and South East Asian countries. Food waste shows variable chemical composition and a high content of biodegradable material (carbohydrates, protein and lipid). This composition led to consistent biogas production that was reported, as average for Chinese FW, of 480 ± 88 LCH4 kg⁻¹ VS (n = 42). Since these data are higher than those reported for energy crops (246 ± 36 LCH4 kg⁻¹ VS), this makes FW a good candidate to substitute for energy crops, avoiding food-energy conflicts. FW co-digestion with different substrates improved total bio-methane production (on average), from 268 ± 199 mL g⁻¹ VS to 406 ± 137 mL g⁻¹ VS. Food waste pretreatment, also, seems to be very useful in increasing total biogas production. Physical and thermal treatments were the best, increasing biogas production by 40% and 30%, respectively. Techno-economic evaluation seems to indicate the feasibility of substituting EC with FW for producing biogas and reducing total biomass costs. To achieve this, separate collection sources need to be put into place, assuring high FW quality to promote a Circular Economy approach in FW management.
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Biogas production from co-digestion of different proportions of food waste and fresh bovine manure
Article
Full-text available
  • Jul 2022
The present study aimed to evaluate the process of anaerobic co-digestion of different proportions of food waste and fresh bovine manure. The experiments were carried out in the laboratory (using 250-mL reactors) and in a pilot-scale biodigester (8 m3). The laboratory experiment was conducted with batch feed systems testing three food waste (FW) and bovine manure (BM) ratios: 0:1, 1:2, and 3:1 (equivalent to 0, 33, and 75 % of food waste in the digester substrate, respectively). The pilot-scale biodigester had a continuous feed system and received a 1:2 FW:BM mixture ratio. The highest accumulated biogas production in the laboratory was 273 mL g-1 of volatile solids (VS) in the treatment with the 1:2 FW:BM ratio. Concentrations of volatile fatty acids (VFA) greater than 8 g L-1 inhibited methane production, except in the treatment without food waste. In the pilot-scale biodigester, concentrations of VFA were below the inhibitory threshold, and the biogas and methane yields were 271 L kgVS-1 and 220 L kgVS-1, respectively. Therefore, food waste can be successfully co-digested with fresh bovine manure in continuous feed digesters, with an initial organic load rate of at least 2.74 kgVS m-3 day-1. Future studies should aim to test progressive increases in food waste load to identify the threshold for inhibition.
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Review on Cow Manure as Renewable Energy
Chapter
Full-text available
  • Feb 2020
The world now is looking for alternative resources of energy instead of using fossil fuels that contribute to the greenhouse gases and that are in depletion. This energy must be renewable and environment eco-friendly. The huge amounts of organic waste produced every year imposes to seek for a new approach and new methods to manage these tremendous quantities of organic waste dumped illegally into natural resources. Cow manure is considered one of the most abundant organic waste threating our world, especially that it produces greenhouse gases, malodours and destroy water and agricultural resources. From the other side, cow manure presents many properties that can be useful as renewable energy and soil organic natural amendment. Regarding the amount of cow manure produced, there is a significant possibility and opportunity for all researchers to work on this organic waste. One of the best biochemical methods used to manage cow manure is an-aerobic digestion. It is considered an attractive approach especially in terms of renewable energy (producing biogas and bio-fertilizers). This review article presents an overview of cow manure used as substrate and co-substrate in the anaerobic digestion process from different perspectives.
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Theoretical methane production generated by the co-digestion of organic fraction municipal solid waste and biological sludge
Article
Full-text available
  • Oct 2014
The co-digestion of two problematic and available wastes, namely Organic Fraction Municipal Solid Waste (OFMSW) and biological sludge, was carried out in this work. Biochemical Methane Potential (BMP) tests are a useful tool for determining the best substrate and co-digestion configurations, however there are some methodologies destined to save costs and time from this process by using the theoretical final methane potential of a substrate from its organic composition. Besides there are some models capable not only of reproducing the methane curve behavior, but also of predicting final methane productions from the first days of experimentation. Methodologies based in the elemental composition for the determination of theoretical production fit better with the experimental results and behavior, nevertheless the Gompertz model was capable of predicting the final productivity within the 7th day of experiment, selecting at the same time the co-digestion of 80% OFMSW and 20% Biological sludge as the optimum.
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ChemInform Abstract: Bio-Energy Recovery from High-Solid Organic Substrates by Dry Anaerobic Bio-Conversion Processes: A Review
Article
Full-text available
  • Jul 2014
Dry anaerobic bio-conversion (D-AnBioC) of high-solid organic substrates (OS) is considered as a sustainable option for waste management practices in different parts of the world. The basic technology is well implemented, but the improvements are still under way in terms of optimization and pre- and post-treatments of the feed and end-products, respectively. The purpose of this review is mainly to: (1) provide existing knowledge and research advances in D-AnBioC systems to treat high-solid OS; (2) identify major issues involved in bioreactor designing; (3) present factors influencing the bio-conversion efficiency; (4) discuss the microbiology of system operation; (5) provide examples of existing commercial-scale plants; (6) discuss energy and economics requirements. From the detailed literature review, it is clear that the characteristics of OS are the major factors governing the overall process and economics. It shows that not all OS are profitably recycled using D-AnBioC systems. Compared to single-stage continuous systems, batch systems under a multi-stage configuration appears to be economically feasible, however, it must be noted that the available data sets are still inconclusive. Also, limited information is available on green house gas mitigation and restoration of nutrients from the digested residue during post-treatment schemes. A summary at the end presents important research gaps of D-AnBioC system to direct future research.
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Anaerobic co-digestion of solid slaughterhouse wastes with agro-residues: Synergistic and antagonistic interactions determined in batch digestion assays
Article
  • Feb 2014
  • CHEM ENG J
Anaerobic co-digestion of solid slaughterhouse wastes with agro-residues: Synergistic and antagonistic interactions determined in batch digestion assays, Chemical Engineering Journal (2014), doi: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Statistical prediction of biomethane potentials based on the composition of lignocellulosic biomass
Article
  • Feb 2014
Mixture models are introduced as a new and stronger methodology for statistical prediction of biomethane potentials (BPM) from lignocellulosic biomass compared to the linear regression models previously used. A large dataset from literature combined with our own data were analysed using canonical linear and quadratic mixture models. The full model to predict BMP (R2 > 0.96), including the four biomass components cellulose (xC), hemicellulose (xH), lignin (xL) and residuals (xR = 1 − xC − xH − xL) had highly significant regression coefficients. It was possible to reduce the model without substantially affecting the quality of the prediction, as the regression coefficients for xC, xH and xR were not significantly different based on the dataset. The model was extended with an effect of different methods of analysing the biomass constituents content (DA) which had a significant impact. In conclusion, the best prediction of BMP is pBMP = 347xC+H+R − 438xL + 63DA.
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Anaerobic Digestion of Food Industry Wastes: Effect of Codigestion on Methane Yield
Article
  • Jul 2005
Anaerobic treatability of two different wastes that represent the main refuse streams generated by a frozen food factory (fresh vegetable waste and precooked food waste) was assessed. Moreover, the sludge coming from agro-industrial wastewater treatment was codigested with the previously mentioned wastes. Batch tests were performed at different solids content both on the single wastes and on appropriate mixtures of them (also in order to simulate the seasonality of factory production). Both fresh vegetable and precooked food wastes strongly inhibited methanogenesis from unacclimated inoculum at 10 % solids content (undiluted waste) and 5 % solids content (eight- to nine-fold diluted waste), respectively. This was due to their high contents of potassium and lipids, respectively. The aerobic sludge from the wastewater treatment plant did not exert inhibitory effect up to 10 % solids content (undiluted waste). Codigestion of the fresh vegetable waste and sludge (60 and 40 % on wet basis) was more effective both in terms of rate and yield of methane production with respect to the single wastes (due to dilution and synergic effects). On the other hand, methanogenesis remained strongly inhibited from mixtures containing pre-cooked food waste (at 25 and 45 %, on wet basis). Methanogenesis inhibition could be overcome by a long acclimation period. The results showed that fill-and-draw digestion in a 0.5 L lab-scale reactor of the fresh vegetable waste and sludge mixture after start up with acclimated inoculum allowed higher methane yields (37 % at high organic load and 57 % at low organic load). Better results were obtained in a 1.7 L micropilot fill-and-draw reactor (yield of 67 %) fed at higher frequency.
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Solid-state anaerobic digestion for methane production from organic waste
Article
  • Dec 2012
  • RENEW SUST ENERG REV
Solid-state anaerobic digestion (SS-AD) generally occurs at solid concentrations higher than 15%. In contrast, liquid anaerobic digestion (AD) handles feedstocks with solid concentrations between 0.5% and 15%. Animal manure, sewage sludge, and food waste are generally treated by liquid AD, while organic fractions of municipal solid waste (OFMSW) and lignocellulosic biomass such as crop residues and energy crops can be processed through SS-AD. Some advantages of SS-AD include smaller reactor capacity requirements, less energy used for heating, and no processing energy needed for stirring. Due to its lower water content, the digestate of SS-AD is much easier to handle than the effluent of liquid AD. However, SS-AD systems also have disadvantages such as larger amounts of required inocula and much longer retention time.The principles and applications of the SS-AD process are reviewed in this paper. The variation in biogas production yields of different feedstocks is discussed as well as the need for pretreatment of lignocellulosic biomass to enhance biogas production. The effects of major operational parameters, including C/N ratio, solids content, temperature, and inoculation on the performance of SS-AD are summarized. While an increase in operating temperature can improve both the biogas yield and the production efficiency, other practices such as using AD digestate or leachate as an inoculant or decreasing the solid content, may increase the biogas yield but have negative impact on production efficiency. Different reactor configurations used in current commercial scale SS-AD systems and the impact of economics on system selection are also discussed.
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Biochemical methane potential (BMP) of food waste and primary sludge: Influence of inoculum pre-incubation and inoculum source
Article
  • Jan 2012
Biochemical methane potential tests were conducted to evaluate the effect of using a blank versus a pre-incubated inoculum in digestion of primary sludge at different waste to inoculum ratios (S/X). In addition, this study explored the influence of using two different anaerobic inoculum sources on the digestion of food waste: digested sludge from a municipal wastewater treatment plant and from a digester treating the organic fraction of municipal solid wastes. The results revealed that although there was no significant difference in methane yield (on average 114mLCH(4)/g TCOD(sub)) or biodegradability (on average 28.3%) of primary sludge using pre-incubated or non-incubated inocula, the maximum methane production rates using non-incubated inoculum were higher than those using pre-incubated inoculum at all S/X ratios. Moreover, interestingly the inoculum from an anaerobic digester treating municipal wastewater sludge was superior over the inoculum from anaerobic digester treating food waste in digesting food waste.
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Co-digestion of different waste mixtures from agro-industrial activities: Kinetic evaluation and synergetic effects
Article
  • Dec 2011
Several wastes from agro-industrial activities were mixed in different ratios to evaluate the co-digestion process. Methane yield YCH4, specific methanogenic activity (SMA) and a kinetic parameter (k0) were determined. A second feeding was also performed to examine the recovery of bacterial activity after exhaustion. Mixture ratios of 1:1:1:1 and 1:3:4:0.5 (w/w) showed the best performance, with YCH4 of 664; 582 NmL CH4/gVSsubstrate, as well as SMA of 0.12; 0.13 gCODNmLCH4/gVSinoculum/d, respectively, during the digestion of the first feed. It was possible to relate synergetic effects with enhancement in YCH4 by up to 43%, compared with values calculated from YCH4 of the individual substrates. All batches started up the biogas production after an exhaustion period, when a second feed was added. However, long lag phases (up to 21 days) were observed due to stressed conditions caused by the substrate limitation prior to the second feed.
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