Table of Contents
The anaerobic digestion of solid organic waste
Azeem Khalid a,⇑, Muhammad Arshad b, Muzammil Anjum a, Tariq Mahmood a, Lorna Dawson c
a
Department of Environmental Sciences, PMAS Arid Agriculture University, Rawalpindi-46300, Pakistan
Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad-38040, Pakistan
c
The James Hutton Institute, Craigiebuckler Aberdeen AB15 8QH, Scotland, UK
b
a r t i c l e
i n f o
Article history:
Received 17 May 2010
Accepted 30 March 2011
Available online 6 May 2011
a b s t r a c t
The accumulation of solid organic waste is thought to be reaching critical levels in almost all regions of
the world. These organic wastes require to be managed in a sustainable way to avoid depletion of natural
resources, minimize risk to human health, reduce environmental burdens and maintain an overall balance in the ecosystem. A number of methods are currently applied to the treatment and management
of solid organic waste. This review focuses on the process of anaerobic digestion which is considered
to be one of the most viable options for recycling the organic fraction of solid waste. This manuscript provides a broad overview of the digestibility and energy production (biogas) yield of a range of substrates
and the digester configurations that achieve these yields. The involvement of a diverse array of microorganisms and effects of co-substrates and environmental factors on the efficiency of the process has
been comprehensively addressed. The recent literature indicates that anaerobic digestion could be an
appealing option for converting raw solid organic wastes into useful products such as biogas and other
energy-rich compounds, which may play a critical role in meeting the world’s ever-increasing energy
requirements in the future.
Ó 2011 Elsevier Ltd. All rights reserved.
Contents
1.
2.
3.
4.
5.
6.
7.
8.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Anaerobic digestion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Anaerobic co-digestion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Anaerobic bioreactors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Biogas yield from anaerobic digestion of solid organic waste. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Role of microorganisms in anaerobic digestion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Factors affecting anaerobic digestion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.1.
Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.2.
pH. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3.
Moisture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.4.
Substrate/carbon source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.5.
Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.6.
C/N Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1. Introduction
Solid organic waste removal has become an ecological problem,
brought to light as a result of an increase in public health concerns
⇑ Corresponding author. Tel.: +92 51 9062221, 4420827; fax: +92 51 9290160.
E-mail addresses: [email protected], [email protected] (A. Khalid).
and environmental awareness. The average solid waste generation
rate in 23 developing countries is 0.77 kg/person/day (Troschinetz
and Mihelcic, 2009) and is increasing. At present, worldwide municipal solid waste generation is about two billion tons per year,
which is predicted to increase to 3 billion tons by 2025 (Charles
et al., 2009). The production of fruit and vegetable waste is also
very high and becoming a source of concern in municipal landfills
because of its high biodegradability (Bouallagui et al., 2005).
Reproduced from Waste Management, 31: 1737-1744 (2011).
Azeem Khalid: Participant of the 30th UM, 2002-2003, & the 2nd UO, 2012-2013.
381
1737
1738
1738
1739
1739
1741
1741
1741
1741
1741
1742
1742
1742
1742
1742
Recently, the organic fraction of solid waste has been recognized as a valuable resource that can be converted into useful
products via microbially mediated transformations (Yu and Huang,
2009; Lesteur et al., 2010). There are various methods available for
the treatment of organic waste but anaerobic digestion appears to
be a promising approach (Lee et al., 2009c). Anaerobic digestion involves a series of metabolic reactions such as hydrolysis, acidogensis and methanogensis (Themelis and Ulloa, 2007). Anaerobic
digestion of organic waste in landfills releases the gases methane
and carbon dioxide that escape into the atmosphere and pollute
the environment (Zhu et al., 2009). Under controlled conditions
the same process has the potential to provide useful products such
as biofuel and organic amendment (soil conditioner) and the treatment system does not require an oxygen supply (Chanakya et al.,
2007; Guermoud et al., 2009). Further, methane and hydrogen as
potential fuels are considered comparatively cleaner than fossil
fuel. In addition, this has the benefit of not depending on fossil fuel
for energy consumption (Jingura and Matengaifa, 2009). Thus,
anaerobic digestion represents an opportunity to decrease environmental pollution and at the same time, providing biogas and organic fertilizer or carrier material for biofertilizers.
The anaerobic treatment of solid organic waste is not as widespread as the aerobic process, mainly due to the longer time required to achieve biostabilization (Fernandez et al., 2010). The
process is also sensitive to high levels of free ammonia resulting
from anaerobic degradation of the nitrogen rich protein components (Fountoulakis et al., 2008). The specific activity of methanogenic bacteria has been found to decrease with increasing
concentrations of ammonia (Chen et al., 2008).
Recent advancements in bioreactor designs have increased the
use of anaerobic digestion for the treatment of solid organic waste.
To date, a number of novel bioreactor designs have been developed
where anaerobic digestion can be performed at a much higher rate
than the conventional methods. Many factors, including the type
and concentration of substrate, temperature, moisture, pH, etc.,
may affect the performance of the anaerobic digestion process in
the bioreactor (Behera et al., 2010; Jeong et al., 2010). This manuscript reviews the potential of anaerobic digestion for recycling solid organic waste.
There are some components in wastes (metals and some recalcitrant organic compounds, often toxic) that will not be broken
down and will therefore become concentrated in the residue.
Although this is an important consideration and must be considered when applying digestions, it is a huge topic and will not be reviewed here.
and a low biomass production (Wang et al., 1999; Steyer et al.,
2002; Angenent et al., 2004; Kim et al., 2006), and it is considered
a viable technology in the competent treatment of organic waste
and the simultaneous production of a renewable energy (De Baere,
2006; Jingura and Matengaifa, 2009).
The anaerobic digestion of organic waste is also an environmentally useful technology. Ward et al. (2008) described the benefits of
this process to reduce environmental pollution in two main ways:
the sealed environment of the process prevents exit of methane
into the atmosphere, while burning of the methane will release
carbon–neutral carbon dioxide (no net effect on atmospheric carbon dioxide and other greenhouse gases).
On the other hand, the anaerobic process has some disadvantages such as long retention times and low removal efficiencies
of organic compounds (Park et al., 2005). The chemical composition and structure of lignocellulosic materials hinders the rate of
biodegradation of solid organic waste. It has been documented that
hydrolysis of the complex organic matter to soluble compounds is
the rate-limiting step of anaerobic processes for wastes with a high
solid content (Chulhwan et al., 2005; Mumme et al., 2010). Consequently, various physical, chemical and enzymatic pre-treatments
are required to increase substrate solubility and accelerate the biodegradation rate of solid organic waste (Torres and Llorens, 2008;
Charles et al., 2009).
3. Anaerobic co-digestion
Co-digestion is a waste treatment method in which different
wastes are mixed and treated together (Agdag and Sponza,
2007). It is also termed as ‘‘co-fermentation’’. Co-digestion is preferably used for improving yields of anaerobic digestion of solid organic wastes due to its numeral benefits. For example, dilution of
toxic compounds, increased load of biodegradable organic matter,
improved balance of nutrients, synergistic effect of microorganisms and better biogas yield are the potential benefits that are
achieved in a co-digestion process. Co-digestion of an organic
waste also provides nutrients in excess (Hartmann and Ahring,
2005), which accelerates biodegradation of solid organic waste
through biostimulation. Additionally, digestion rate and stabilization are increased (Sosnowski et al., 2003; Lo et al., 2010). Jingura
and Matengaifa (2009) described the following multiple benefits of
co-digestion: the facilitation of a stable and reliable digestion performance and production of a digested product of good quality, and
an increase in biogas yield.
It has been observed that co-digestion of mixtures stabilizes the
feed to the bioreactor, thereby improving the C/N ratio and
decreasing the concentration of nitrogen (Cuetos et al., 2008).
The use of a co-substrate with a low nitrogen and lipid content
waste increases the production of biogas due to complementary
characteristics of both types of waste, thus reducing problems
associated with the accumulation of intermediate volatile compounds and high ammonia concentrations (Castillo et al., 2006).
Several studies have shown that mixtures of agricultural, municipal and industrial wastes can be digested successfully and efficiently together (Table 1). A stimulatory effect on synthesis of
methane gas has been observed when industrial sludge was codigested with municipal solid waste (Agdag and Sponza, 2007).
The co-digestion of municipal solid waste with an industrial sludge
ratio of 1:2 yielded the highest amount methane gas, compared to
municipal solid waste alone. Similarly, in a two-phase anaerobic
digestion system, Fezzani and Cheikh (2010) recorded the highest
methane productivity when a mixture of olive mill wastewater and
olive mill solid waste was co-digested. The process has also been
useful in obtaining a valuable sludge which can eventually be used
as a soil amendment after minor treatments (Gomez et al., 2006).
2. Anaerobic digestion
With the introduction of both commercial and pilot anaerobic
digestion plant designs during early 1990s, anaerobic digestion of
organic waste has received worldwide attention (Karagiannidis
and Perkoulidis, 2009). It is a process by which almost any organic
waste can be biologically transformed into another form, in the absence of oxygen. The diverse microbial populations degrade organic waste, which results in the production of biogas and other
energy-rich organic compounds as end products (Lastella et al.,
2002; Lata et al., 2002). A series of metabolic reactions such as
hydrolysis, acidogenesis, acetogenesis and methanogenesis are involved in the process of anaerobic decomposition (Park et al., 2005;
Charles et al., 2009).
Anaerobic digestion is applicable for a wide range of material
including municipal, agricultural and industrial wastes, and plant
residues (Kalra and Panwar, 1986; Gallert et al., 1998; Chen
et al., 2008). Furthermore, this process has some advantages over
aerobic process due to a low energy requirement for operation
382
Table 1
Relative biogas production rates and methane yield from the co-digestion of solid organic waste.
*
Substrate
Co-substrate
Cattle excreta
Olive mill waste
Cattle manure
Biogas production
rate (l/d)
Methane yield
(l/kg VS*)
Comments
References
1.10
179
Goberna et al. (2010)
Agricultural waste and
energy crops
2.70
620
Fruit and vegetable waste
Abattoir wastewater
2.53
611
Municipal solid waste
Fly ash
6.50
222
Municipal solid wastes
Fat, oil and grease waste
from sewage treatment
plants
13.6
350
Pig manure
Fish and bio-diesel waste
16.4
620
Potato waste
Sugar beet waste
1.63
680
Primary sludge
Fruit and vegetable waste
4.40
600
Sewage sludge
Municipal solid waste
3.00
532
Slaughter house waste
Municipal solid waste
8.60
500
The co-digestion system produced
337% higher biogas than that of
excreta alone
Significant increase in biogas
production from the co-digestion was
observed
The addition of abattoir wastewater
to the feedstock increased biogas
yield up to 51.5%
Application of fly ash significantly
enhanced biogas production rates of
the municipal solid waste
Co-digestion resulted in an increase
of 72% in biogas production and 46%
methane yield in comparison with
municipal solid waste
Highest biogas production rate was
obtained by a mixture of wastes
Co-digestion improved methane yield
up to 62% compared to the digestion
of potato waste alone
Co-digestion produced more biogas
as compared to primary sludge alone
Biogas production of the mixtures
increased with increasing
proportions of the municipal solid
waste
Biogas yield of the co-digestion
systems doubled that of the slaughter
house waste digestion system
Cavinato et al. (2010)
Bouallagui et al. (2009a)
Lo et al. (2010)
Martin-Gonzalez et al. (2010)
Alvarez et al. (2010)
Parawira et al. (2004)
Gomez et al. (2006)
Sosnowski et al. (2003)
Cuetos et al. (2008)
VS: Volatile solids.
take place separately (Ward et al., 2008). The two-stage system is
considered a promising process to treat organic wastes with high
efficiency in term of degradation yield and biogas production
(Fezzani and Cheikh, 2010). According to Demirer and Chen
(2005), a two stage system allows the selection and enrichment
of different bacteria in each phase. The complex organic materials
are degraded by acidogenic bacteria to volatile fatty acids and alcohols, which are then easily metabolized into methane and carbon
dioxide by methanogens or archaea. Further, this type of system
increases the stability of the process by controlling the acidification phase through optimization of the hydraulic retention time
to prevent overloading and the build-up of toxic material. The biomass concentration and other conditions can also be optimized
independently for each stage (Demirer and Chen, 2005). All the
above three types of bioreactors, along with a variety of methanizers such as continuously stirred tank bioreactor, tubular bioreactor,
anaerobic sequencing batch bioreactor, up flow anaerobic sludge
blanket and anaerobic filters are applied for the treatment of
different types of waste (Bouallagui et al., 2005).
Biodigesters are also classified as ‘‘wet’’ or ‘‘dry’’ solid waste
digesters. According to Ward et al. (2008), wet bioreactors have total solids of 16% or less, while dry bioreactors contain 22–40% total
solids, with the intermediate rating termed ‘semi dry’, while
according to Karagiannidis and Perkoulidis (2009), dry systems
contain 30–40% dry matter where as wet systems contain 10–
25% dry matter. Another type of bioreactor based on operating
temperatures (i.e., thermophilic or mesophilic) are also available
(Kuo and Cheng, 2007; Karagiannidis and Perkoulidis, 2009).
4. Anaerobic bioreactors
Anaerobic bioreactors have potential application for rapid
digestion of solid organic waste constituents to reduce the environmental load as compared to conventional sanitary landfills
(Agdag and Sponza, 2007). Bioreactor design has been found to
exert a strong influence on the performance of a digester (William
and David, 1999). As described earlier (Table 2), a variety of new
bioreactor designs have been developed in recent years, which
facilitate a significantly higher rate of reaction for the treatment
of waste (Bouallagui et al., 2003; Mumme et al., 2010; Xing et al.,
2010). According to Ward and his co-workers, an anaerobic bioreactor should be designed in a way that allows a continuously high
and sustainable organic load rate with a short hydraulic retention
time and has the ability to produce the maximum level of methane
(Ward et al., 2008).
Several types of bioreactors are currently in use but the three
major groups of bioreactors commonly in use include batch reactors, a one stage continuously fed system and a two stage or multi-stage continuously fed system. Batch reactors are the simplest,
filled with the feedstock and left for a period that can be considered to be the hydraulic retention time, after which they are emptied. Anaerobic batch reactors are useful because they can perform
quick digestion with simple and inexpensive equipment, and also
are helpful in assessing the rate of digestion easily (Parawira
et al., 2004; Weiland, 2006). On the other hand, batch reactors have
some limitations such as high fluctuations in gas production as
well as gas quality, biogas losses during emptying the bioreactors
and restricted bioreactor heights (Linke et al., 2006). The second
type of bioreactors is known as ‘one-stage continuously fed systems’, where all the biochemical reactions take place in one bioreactor. The third type of bioreactors are ‘two-stage’ or ‘multi-stage
continuously fed systems’, in which various biochemical processes
such as hydrolysis, acidification, acetogenesis and methanogenesis
5. Biogas yield from anaerobic digestion of solid organic waste
The process of biogas generation from solid organic waste is often carried out by several different anaerobic bacteria (Jingura and
383
Table 2
Different types of bioreactors used for anaerobic digestion.
Bioreactor type
Type of substrate
Anaerobic sequencing batch
bioreactor
Fruit and vegetable
waste and abattoir
wastewater
Continuously stirred tank
reactors
Municipal solid waste
15
Full-scale anaerobic
digester
Integrative biological
reactor
Industrial food waste
17
Laboratory-scale semi
continuous reactors
Municipal solid waste
and press water from
municipal composting
plant
Primary treated
sewage effluent with or
without refractory
organic pollutants
Municipal solid waste
15
Self mixing anaerobic
digesters
Poultry litter
16
Submerged anaerobic
membrane bioreactor
Sewage sludge, food
waste and livestock
wastewater
Olive mill wastewater
and olive mill solid
waste
New starch based
flocculant-anaerobic
fluidized bed bioreactor
Rotating drum mesh filter
bioreactor
Two-phase anaerobic semicontinuous digester
Two stage anaerobic
hydrogen and methane
production reactor
Up flow anaerobic solidstate bioreactor
Kitchen waste
Organic waste
Mixture of maize silage
and straw
Organic loading
rate (kg/m3/d)
2.6
8.0
20
43
Comments
References
A decrease in biogas production was
observed due to high amount of free
ammonia at high organic loading rate
(OLR)
The reactor showed superior process
performance as the OLR progressively
increased up to 15 kg/m3/d
Methane yield of 360 l/kg feed waste with
40 days retention time was observed
Integrative biological reactor showed the
best performance and biogas production
rate was higher than the single reactor
The reactor performance for biogas
production was higher up to 20 OLR but
further increase in OLR did not affect the
biogas production
The efficiency and microbial activity at
high OLR was higher than conventional
anaerobic fluidized bed bioreactor
Bouallagui et al. (2009b)
The reactor proved to be stable and
helpful in mixing the waste at high OLR,
which is usually not possible in
mechanically stirred digesters
Self mixing at high OLR and high
biomethanization of the poultry litter was
observed
The reactor showed unstable performance
during the initial stage, but performed
superior after acclimation formation
The best performance in terms of methane
productivity, soluble COD and phenol
removal efficiencies and effluent quality
was observed
Compared to a single-stage methanogenic
reactor, 11% higher energy was achieved
1.8
14
3.0
17
The UASS reactor showed the highest
methanogenic performance for the
digestion of solid biomass
Matengaifa, 2009). Several reports indicate that anaerobic digestion of the organic fraction of solid waste yields promising
amounts of biogas (Table 3). Biogas is generally composed of 48–
65% methane, 36–41% carbon dioxide, up to 17% nitrogen, <1% oxygen, 32–169 ppm hydrogen sulphide and traces of other gases
(Ward et al., 2008). Unlike fossil fuel, biogas does not contribute
much to the greenhouse effect, ozone depletion or acid rain (Nath
and Das, 2004). This is one of the main reasons that anaerobic
digestion may play a very crucial role in meeting energy challenges
of the future generation.
The biogas yield is affected by many factors including type and
composition of substrate, microbial composition, temperature,
moisture and bioreactor design, etc. Hernandez-Berriel et al.
(2008) studied the methane production from biodegradation of
municipal solid waste. They found that the process reached the onset of the methanogenic phase at day 63 and the methane production rate was greater at a moisture level of 70%. However, a
decrease in biogas production was observed in the case of fruit
and vegetable waste due to rapid acidification of these wastes,
resulting in a lowering of the pH in the bioreactor. Moreover, production of larger volatile fatty acids from such waste under anaerobic conditions inhibits the activity of methanogenic bacteria. The
addition of co-substrates such as abattoir waste water and activated sludge to fruit and vegetable waste can enhance biogas production up to 52% (Bouallagui et al., 2009a). Behera et al. (2010)
examined methane production from food waste leachate (FWL)
Angelidaki et al. (2006)
Ike et al. (2010)
Guo et al. (2011)
Nayono et al. (2010)
Xing et al. (2010)
Walker et al. (2009)
Rao et al. (2011)
Jeong et al. (2010)
Fezzani and Cheikh (2010)
Luo et al. (2011)
Mumme et al. (2010)
in simulated landfill bioreactors (lysimeters) for a period of 90 days
with four different inoculum–substrate ratios (ISRs). The maximum methane yield was achieved in the lysimeter at ISR of 1:1.
Based on the results obtained from this study, the authors
Table 3
Biogas yield recorded from anaerobic digestion of the solid organic waste.
*
384
Substrate
Methane yield
(l/kg VS*)
References
Municipal solid waste
Fruit and vegetable wastes
Municipal solid waste
Fruit and vegetable waste,
and abattoir wastewater
Swine manure
Municipal solid waste
Food waste leachate
Rice straw
Maize silage and straw
Jatropha oil seed cake
Palm oil mill waste
Household waste
Lignin-rich organic waste
Swine manure and winery
wastewater
Food waste
360
420
530
850
337
200
294
350
312
422
610
350
200
348
Vogt et al. (2002)
Bouallagui et al. (2005)
Forster-Carneiro et al. (2007)
Forster-Carneiro et al.
(2007)
Ahn et al. (2009)
Walker et al. (2009)
Behera et al. (2010)
Lei et al. (2010)
Mumme et al. (2010)
Chandra et al. (2011)
Fang et al. (2011)
Ferrer et al. (2011)
Jayasinghe et al. (2011)
Riano et al. (2011)
396
Zhang et al. (2011)
VS: Volatile solids.
concluded that the bioreactors with efficient leachate collection
and gas recovery facilities could be effective to treat non-hazardous liquid organic wastes for energy recovery. Likewise, Lee and
his co-workers (2009b) suggested that anaerobic digestion of
FWL in bioreactor landfills or anaerobic digesters (with a preferred
control of alkalinity and salinity) could be a sustainable solution to
convert biomass to biogas and achieve high biodegradability
potential.
rates, and biogas production (Kim et al., 2006; Trzcinski and
Stuckey, 2010). Moreover, lower temperatures may also result in
an exhaustion of cell energy, a leakage of intracellular substances
or complete lysis (Kashyap et al., 2003). In contrast, high temperatures lower biogas yield due to the production of volatile gases
such as ammonia which suppresses methanogenic activities
(Fezzani and Cheikh, 2010).
Generally, anaerobic digestion is carried out at mesophilic temperatures (El-Mashad et al., 2003). The operation in the mesophilic
range is more stable and requires a smaller energy expense
(Fernandez et al., 2008; Ward et al., 2008). Castillo et al. (2006)
found that the best operational temperature was 35 °C with an
18 day digestion period while a little fluctuation in temperature
from 35 °C to 30 °C caused a reduction in the rate of biogas production (Chae et al., 2008). Overall, a temperature range between 35–
37 °C is considered suitable for the production of methane and a
change from mesophilic to thermophilic temperatures can cause
a sharp decrease in biogas production until the necessary populations have increased in number. Briski et al. (2007) reported that
for biodegradation, the temperature must be below 65 °C because
above 65 °C denaturation of enzymes occurs. However, thermophilic conditions have certain advantages, such as a faster degradation rate of organic waste, higher biomass and gas production, less
effluent viscosity and higher pathogen destruction (Zhu et al.,
2009). Ward et al. (2008) has shown optimal growth temperatures
for some methanogenic bacteria: 37–45 °C for mesophilic Methanobacterium, 37–40 °C for Methanobrevibacter, 35–40 °C for Methanolobus, Methanococcus, Methanoculleus, Methanospirillum and
Methanolobus, 30–40 °C for Methanoplanus and Methanocorpusculum and 50–55 °C for thermophilic Methanohalobium and
Methanosarcina.
6. Role of microorganisms in anaerobic digestion
The anaerobic digestion process can be catalyzed by a variety of
microorganisms that convert complex macromolecules into low
molecular weight compounds. An inoculum source is crucial for
the optimization of the waste/inoculum ratio (Lopes et al., 2004;
Forster-Carneiro et al., 2007). Sludge is commonly used as inoculum for the treatment of waste (Forster-Carneiro et al., 2007; Dong
et al., 2009); although naturally selected strains or artificially
mixed strains of microorganisms are also employed. In addition,
cell aggregates in the form of flocs, biofilms, granules, and mats,
with dimensions that typically range from 0.1 to 100 mm may also
be used in the treatment system (Jeong et al., 2010).
A wide variety of microbial communities have been reported to
be involved in the anaerobic decomposition process. Fricke et al.
(2007) reported that organic material is most likely decomposed
by heterotrophic microorganisms. Lee et al. (2009a) reported that
Clostridium species are most common among the degraders under
anaerobic condition. However, it is very unusual for a biological
treatment to rely solely on a single microbial strain and generally
a microbial consortium is responsible for the anaerobic digestion
process (Fantozzi and Buratti, 2009). According to Ike et al.
(2010), a group of microorganisms such as actinomyces, Thermomonospora, Ralstonia and Shewanella are involved in the degradation of food waste into volatile fatty acids, but Methanosarcina
and Methanobrevibacter/Methanobacterium mainly contribute in
methane production. Similarly, Charles et al. (2009) reported the
presence of Methanosarcina thermophila, Methanoculleus thermophilus, and Methanobacterium formicicum during anaerobic digestion. Using denaturing gradient gel electrophoresis and DNA
sequencing techniques, Trzcinski et al. (2010) found hydrogenotrophic species (mainly, Methanobrevibacter sp., M. formicicum
and Methanosarcina sp.) active in methane synthesis. An increase
in methane content was also observed with the increase in the
number of hydrogenotrophic species (Trzcinski et al., 2010). However, high concentration of organic acid like acetic acid
(>5000 mg L 1) and butyric acid (>3000 mg L 1) in the biodigester
has been found to inhibit the growth of microorganisms and consequently the production of energy rich compounds (Kim et al.,
2008).
7.2. pH
A range of pH values suitable for anaerobic digestion has been
reported by various researchers, but the optimal pH for methanogenesis has been found to be around 7.0 (Huber et al., 1982; Yang
and Okos, 1987). Agdag and Sponza (2007) reported a very narrow
range of suitable pH (7.0–7.2) in the industrial sludge added bioreactors during the last 50 days of the anaerobic incubation. Similarly, Ward et al. (2008) found that a pH range of 6.8–7.2 was
ideal for anaerobic digestion. Lee et al. (2009b) reported that methanogenisis in an anaerobic digester occurs efficiently at pH 6.5–
8.2, while hydrolysis and acidogenesis occurs at pH 5.5 and 6.5,
respectively (Kim et al., 2003). From the batch experiments, it
was shown that the appropriate pH range for thermophilic acidogens was 6–7 (Park et al., 2008). Dong et al. (2009) suggested that
the hydrogen production will be at a maximum if the initial pH of a
biosystem is maintained at 9. However, similar results can also be
achieved at pH 5–6 (Kapdan and Kargi, 2006). Liu et al. (2008)
showed that the most favorable range of pH to attain maximal biogas yield in anaerobic digestion is 6.5–7.5.
7. Factors affecting anaerobic digestion
The anaerobic digestion of organic material is a complex process, involving a number of different degradation steps. The microorganisms that participate in the process may be specific for each
degradation step and thus could have different environmental
requirements.
7.3. Moisture
High moisture contents usually facilitate the anaerobic digestion; however, it is difficult to maintain the same availability of
water throughout the digestion cycle (Hernandez-Berriel et al.,
2008). Initially water added at a high rate is dropped to a certain
lower level as the process of anaerobic digestion proceeds. High
water contents are likely to affect the process performance by dissolving readily degradable organic matter. It has been reported
that the highest methane production rates occur at 60–80% of
humidity (Bouallagui et al., 2003). Hernandez-Berriel et al. (2008)
studied methanogenesis processes during anaerobic digestion at
different moisture levels i.e., 70% and 80%. They found that the
7.1. Temperature
Many researchers have reported significant effects of temperature on the microbial community, process kinetics and stability
and methane yield (Dela-Rubia et al., 2002; Bouallagui et al.,
2009b; Riau et al., 2010). Lower temperatures during the process
are known to decrease microbial growth, substrate utilization
385
onset of the methanogenic phase took place around day 70 in both
cases, at 70% and 80% moisture. However, bioreactors under the
70% moisture regime produced a stronger leachate and consequently a higher methane production rate. At the end of the experiment, 83 ml methane per gram dry matter were produced at the
70% moisture level, while 71 ml methane per gram dry matter
were produced with the 80% moisture. Nonetheless, bioreactors
from both moisture regimes showed similar ratios (0.68) of biochemical oxygen demand (BOD) to chemical oxygen demand
(COD).
rate, and anaerobic ammonia production from organic nitrogen,
which reduce the limitations of fruit and vegetable waste digestion. The C/N ratio of 20–30 may provide sufficient nitrogen for
the process (Weiland, 2006), and Bouallagui et al. (2009a) suggested that a C/N ratio between 22 and 25 seemed to be best for
anaerobic digestion of fruit and vegetable waste, whereas,
Guermoud et al. (2009) and Lee et al. (2009b) reported that the
optimal C/N ratio for anaerobic degradation of organic waste was
20–35.
8. Conclusions
7.4. Substrate/carbon source
The preceding review clearly indicates that anaerobic digestion
is one of the most effective biological processes to treat a wide
variety of solid organic waste products and sludge. The prime
advantages of this technology include (i) organic wastes with a
low nutrient content can be degraded by co-digesting with different substrates in the anaerobic bioreactors, and (ii) the process
simultaneously leads to low cost production of biogas, which could
be vital for meeting future energy-needs. However, different factors such as substrate and co-substrate composition and quality,
environmental factors (temperature, pH, organic loading rate),
and microbial dynamics contribute to the efficiency of the anaerobic digestion process, and must be optimized to achieve maximum
benefit from this technology in terms of both energy production
and organic waste management. The use of advanced molecular
techniques can further help in enhancing the efficiency of this system by identifying the microbial community structure and function, and their ecological relationships in the bioreactor. This
technology has tremendous application in the future for sustainability of both environment and agriculture, with the production
of energy as an extra benefit.
The rate of anaerobic digestion is strongly affected by the type,
availability and complexity of the substrate (Ghaniyari-Benis et al.,
2009; Zhao et al., 2010). Different types of carbon source support
different groups of microbes. Before starting a digestion process,
the substrate must be characterized for carbohydrate, lipid, protein
and fiber contents (Lesteur et al., 2010). In addition, the substrate
should also be characterized for the quantity of methane that can
potentially be produced under anaerobic conditions. Carbohydrates are considered the most important organic component of
municipal solid waste for biogas production (Dong et al., 2009).
However, starch could act as an effective low cost substrate for biogas production compared to sucrose and glucose (Su et al., 2009). It
was reported that the initial concentration and total solid content
of the substrate in the bioreactor can significantly affect the performance of the process and the amount of methane produced during
the process (Fernandez et al., 2008).
7.5. Nitrogen
Nitrogen is essential for protein synthesis and primarily required
as a nutrient by the microorganisms in anaerobic digestion
(Kayhanian and Rich, 1995). Nitrogenous compounds in the organic
waste are usually proteins which are converted to ammonium by
anaerobic digestion (Sawayama et al., 2004). In the form of ammonium, nitrogen contributes to the stabilization of the pH value in
the bioreactor where the process is taking place. Microorganisms
assimilate ammonium for the production of new cell mass. A nutrient ratio of the elements C:N:P:S at 600:15:5:3 is considered sufficient for methanization (Fricke et al., 2007). Ammonia in high
concentration may lead to the inhibition of the biological process
and it inhibits methanogenesis at concentrations exceeding approximately 100 mM (Fricke et al., 2007). Sterling et al. (2001) found that
the amount of ammonia in the digester may also affect the production of hydrogen and removal of volatile solids. Total biogas production was unaffected by small increases in ammonia nitrogen while
higher increases reduced the biogas production by 50% of the original rate. In the fluidized-bed anaerobic digester, the methane formation decreased at ammonium concentrations of greater than
6000 mg NH4–N/l. It was reported that methanogenic activity is decreased by 10% at ammonium concentrations of 1670–3720 mg
NH4–N/l, while by 50% at 4090–5550 mg NH4–N/l, and completely
zero at 5880–6000 mg NH4–N/l (Sawayama et al., 2004).
References
Agdag, O.N., Sponza, D.T., 2007. Co-digestion of mixed industrial sludge with
municipal solid wastes in anaerobic simulated landfilling bioreactors. J. Hazard.
Mat. 140, 75–85.
Ahn, H.K., Smith, M.C., Kondrad, S.L., White, J.W., 2009. Evaluation of biogas
production potential by dry anaerobic digestion of switchgrass–animal manure
mixtures. Appl. Biochem. Biotechnol. 160, 965–975.
Alvarez, J.A., Otero, L., Lema, J.M., 2010. A methodology for optimizing feed
composition for anaerobic co-digestion of agro-industrial wastes.
Bioresour.Technol. 101, 1153–1158.
Angelidaki, I., Chen, X., Cui, J., Kaparaju, P., Ellegaard, L., 2006. Thermophilic
anaerobic digestion of source-sorted organic fraction of household municipal
solid waste: start-up procedure for continuously stirred tank reactor. Water
Res. 40, 2621–2628.
Angenent, L.T., Karim, K., Al-Dahhan, M.H., Wrenn, B.A., Domiguez-Espinosa, R.,
2004. Production of bioenergy and biochemicals from industrial and
agricultural wastewater. Trends Biotechnol. 22, 477–485.
Behera, S.K., Park, J.M., Kim, K.H., Park, H., 2010. Methane production from food
waste leachate in laboratory-scale simulated landfill. Waste Manage. 30, 1502–
1508.
Bouallagui, H., Cheikh, R.B., Marouani, L., Hamdi, M., 2003. Mesophilic biogas
production from fruit and vegetable waste in tubular digester. Bioresour.
Technol. 86, 85–89.
Bouallagui, H., Touhami, Y., Cheikh, R.B., Hamdi, M., 2005. Bioreactor performance in
anaerobic digestion of fruit and vegetable wastes. Process Biochem. 40, 989–
995.
Bouallagui, H., Lahdheb, H., Romdan, E., Rachdi, B., Hamdi, M., 2009a. Improvement
of fruit and vegetable waste anaerobic digestion performance and stability with
co-substrates addition. J. Environ. Manage. 90, 1844–1849.
Bouallagui, H., Rachdi, B., Gannoun, H., Hamdi, M., 2009b. Mesophilic and
thermophilic anaerobic co-digestion of abattoir wastewater and fruit and
vegetable wastein anaerobic sequencing batch reactors. Biodegradation 20,
401–409.
Briski, F., Vukovic, M., Papa, K., Gomzi, Z., Domanovac, T., 2007. Modelling of
compositing of food waste in a column reactor. Chem. Pap. 61, 24–29.
Castillo, E.F.M., Cristancho, D.E., Arellano, V.A., 2006. Study of the operational
conditions for anaerobic digestion of urban solid wastes. Waste Manage. 26,
546–556.
Cavinato, C., Fatone, F., Bolzonella, D., Pavan, P., 2010. Thermophilic anaerobic codigestion of cattle manure with agro-wastes and energy crops: comparison of
pilot and full scale experiences. Bioresour. Technol. 101, 545–550.
7.6. C/N Ratio
The C/N ratio in the organic material plays a crucial role in
anaerobic digestion. The unbalanced nutrients are regarded as an
important factor limiting anaerobic digestion of organic wastes.
For the improvement of nutrition and C/N ratios, co-digestion of organic mixtures is employed (Cuetos et al., 2008). Co-digestion of
fish waste, abattoir wastewater and waste activated sludge with
fruit and vegetable waste facilitates balancing of the C/N ratio.
Their greatest advantage lies in the buffering of the organic loading
386
Chae, K.J., Jang, A., Yim, S.K., Kim, I.S., 2008. The effects of digestion temperature and
temperature shock on the biogas yields from the mesophilic anaerobic
digestion of swine manure. Bioresour. Technol. 99, 1–6.
Chanakya, H.N., Ramachandra, T.V., Vijayachamundeeswari, M., 2007. Resource
recovery potential from secondary components of segregated municipal solid
wastes. Environ. Monit. Assess. 135, 119–127.
Chandra, R., Vijay, V.K., Subbarao, P.M.V., Khura, T.K., 2011. Production of methane
from anaerobic digestion of jatropha and pongamia oil cakes. Appl. Energy. doi:
10.1016/j.apenergy.2010.10.049.
Charles, W., Walker, L., Cord-Ruwisch, R., 2009. Effect of pre-aeration and inoculum
on the start-up of batch thermophilic anaerobic digestion of municipal solid
waste. Bioresour. Technol. 100, 2329–2335.
Chen, Y., Cheng, J.J., Creamer, K.S., 2008. Inhibition of anaerobic digestion process: a
review. Bioresour. Technol. 99, 4044–4064.
Chulhwan, P., Chunyeon, L., Sangyong, K., Yu, C., Howard, C.H., 2005. Upgrading of
anaerobic digestion by incorporating two different hydrolysis processes. J.
Biosci. Bioeng. 100, 164–167.
Cuetos, M.J., Gomez, X., Otero, M., Moran, A., 2008. Anaerobic digestion of solid
slaughterhouse waste (SHW) at laboratory scale: influence of co-digestion with
the organic fraction of municipal solid waste (OFMSW). Biochem. Eng. J. 40, 99–
106.
De Baere, L., 2006. Will anaerobic digestion of solid waste survive in the future.
Water Sci. Technol. 53, 187–194.
Dela-Rubia, M.A., Perez, M., Romero, L.I., Sales, D., 2002. Anaerobic mesophilic and
thermophilic municipal sludge digestion. Chem. Biochem. Eng. Qual. 16, 119–
124.
Demirer, G.N., Chen, S., 2005. Two-phase anaerobic digestion of unscreened dairy
manure. Process Biochem. 40, 3542–3549.
Dong, L., Zhenhong, Y., Yongming, S., Xiaoying, K., Yu, Z., 2009. Hydrogen production
characteristics of organic fraction of municipal solid wastes by anaerobic mixed
culture fermentation. Int. J. Hydr. Energy 34, 812–820.
El-Mashad, H.M., Wilko, K.P., Loon, V., Zeeman, G., 2003. A model of solar energy
utilisation in the anaerobic digestion of cattle manure. Biosyst. Eng. 84, 231–
238.
Fang, C., O-Thong, S., Boe, K., Angelidaki, I., 2011. Comparison of UASB and EGSB
reactors performance, for treatment of raw and deoiled palm oil mill effluent
(POME). J. Hazard. Mat. doi: 10.1016/j.jhazmat.2011.02.025.
Fantozzi, F., Buratti, C., 2009. Biogas production from different substrates in an
experimental Continuously Stirred Tank Reactor anaerobic digester. Bioresour.
Technol. 100, 5783–5789.
Fernandez, J., Perez, M., Romero, L.I., 2008. Effect of substrate concentration on dry
mesophilic anaerobic digestion of organic fraction of municipal solid waste
(OFMSW). Bioresour. Technol. 99, 6075–6080.
Fernandez, J., Perez, M., Romero, L.I., 2010. Kinetics of mesophilic anaerobic
digestion of the organic fraction of municipal solid waste: influence of initial
total solid concentration. Bioresour. Technol. 101, 6322–6328.
Ferrer, I., Garfí, M., Uggetti, E., Ferrer-Marti, L., Calderon, A., Velo, E., 2011. Biogas
production in low-cost household digesters at the Peruvian Andes. Biomass
Bioenergy. doi: 10.1016/j.biombioe.2010.12.036.
Fezzani, B., Cheikh, R.B., 2010. Two-phase anaerobic co-digestion of olive mill
wastes in semi-continuous digesters at mesophilic temperature. Bioresour.
Technol. 101, 1628–1634.
Forster-Carneiro, T., Pérez, M., Romero, L.I., Sales, D., 2007. Dry-thermophilic
anaerobic digestion of organic fraction of the municipal solid waste: focusing on
the inoculum sources. Bioresour. Technol. 98, 3195–3203.
Fountoulakis, M.S., Drakopoulou, S., Terzakis, S., Georgaki, E., Manios, T., 2008.
Potential for methane production from typical Mediterranean agro-industrial
by-products. Biomass Bioenergy 32, 155–161.
Fricke, K., Santen, H., Wallmann, R., Huttner, A., Dichtl, N., 2007. Operating problems
in anaerobic digestion plants resulting from nitrogen in MSW. Waste Manage.
27, 30–43.
Gallert, C., Bauer, S., Winter, J., 1998. Effect of ammonia on the anaerobic
degradation of protein by a mesophilic and thermophilic biowaste
population. Appl. Microbiol. Biotechnol. 50, 495–501.
Ghaniyari-Benis, S., Borja, R., Ali Monemian, S., Goodarzi, V., 2009. Anaerobic
treatment of synthetic medium-strength wastewater using a multistage biofilm
reactor. Bioresour. Technol. 100, 1740–1745.
Goberna, M., Schoen, M.A., Sperl, D., Wett, W., Insam, H., 2010. Mesophilic and
thermophilic co-fermentation of cattle excreta and olive mill wastes in pilot
anaerobic digesters. Biomass Bioenergy 34, 340–346.
Gomez, X.M., Cuetos, J., Cara, J., Moran, A., Garcia, A.I., 2006. Anaerobic co-digestion
of primary sludge and the fruit and vegetable fraction of the municipal solid
wastes: conditions for mixing and evaluation of the organic loading rate.
Renew. Energy 31, 2017–2024.
Guermoud, N., Ouagjnia, F., Avdelmalek, F., Taleb, F., Addou, A., 2009. Municipal
solid waste in Mostagnem city (Western Algeria). Waste Manage. 29, 896–
902.
Guo, L., Shi, Y., Zhang, P., Wu, L., Gai, G.S., Wang, H., Xiao, D.L., 2011. Investigations,
analysis and study on biogas utilization in cold region of North China. Adv. Mat.
Res. 183–185, 673–677.
Hartmann, H., Ahring, B.K., 2005. Anaerobic digestion of the organic fraction of
municipal solid waste: influence of co-digestion with manure. Water Res. 39,
1543–1552.
Hernandez-Berriel, M.C., Benavides, L.M., Perez, D.J.G., Delgado, O.B., 2008. The
effect of moisture regimes on the anaerobic degradation of municipal solid
waste from Metepec (Mexico). Waste Manage. 28, 14–20.
Huber, H., Thomm, M., Konig, H., Thies, G., Stetter, K.O., 1982. Methanococeus
thermolithotrophicus, a novel thermophilic lithotrophic methanogen. Arch.
Microbiol. 132, 47–50.
Ike, M., Inoue, D., Miyano, T., Liu, T.T., Sei, K., Soda, S., Kadoshin, S., 2010. Microbial
population dynamics during startup of a full-scale anaerobic digester treating
industrial food waste in Kyoto eco-energy project. Bioresour. Technol. 101,
3952–3957.
Jayasinghe, P.A., Hettiaratchi, J.P.A., Mehrotra, A.K., Kumar, S., 2011. Effect of
enzyme additions on methane production and lignin degradation of landfilled
sample of municipal solid waste. Bioresour. Technol. 102, 4633–4637.
Jeong, E., Kim, H., Nam, J., Shin, H., 2010. Enhancement of bioenergy production and
effluent quality by integrating optimized acidification with submerged
anaerobic membrane bioreactor. Bioresour. Technol. 101, 1873–2976.
Jingura, R.M., Matengaifa, R., 2009. Optimization of biogas production by anaerobic
digestion for sustainable energy development in Zimbabwe. Renew. Sust.
Energy Rev. 13, 1116–1120.
Kalra, M.S., Panwar, J.S., 1986. Anaerobic digestion of rice crop residues. Agric.
Waste 17, 263–269.
Kapdan, I.K., Kargi, F., 2006. Bio-hydrogen production from waste materials. Enzyme
Microbial Technol. 38, 569–582.
Karagiannidis, A., Perkoulidis, G., 2009. A multi-criteria ranking of different
technologies for the anaerobic digestion for energy recovery of the organic
fraction of municipal solid wastes. Bioresour. Technol. 100, 2355–2360.
Kashyap, D.R., Dadhich, K.S., Sharma, S.K., 2003. Biomethanation under
psychrophilic conditions: a review. Bioresour. Technol. 87, 147–153.
Kayhanian, M., Rich, D., 1995. Pilot-scale high solids thermophilic anaerobic
Digestion of municipal solid waste with an emphasis on nutrient
requirements. Biomass Bioenergy 8, 433–444.
Kim, J., Park, C., Kim, T.H., Lee, M., Kim, S., Kim, S.W., Lee, J., 2003. Effects of various
pretreatments for enhanced anaerobic digestion with waste activated sludge. J.
Biosci. Bioeng. 95, 271–275.
Kim, J.K., Oh, B.R., Chun, Y.N., Kim, S.W., 2006. Effects of temperature and hydraulic
retention time on anaerobic digestion of food waste. J. Biosci. Bioeng. 102, 328–
332.
Kim, J.K., Nhat, L., Chun, Y.N., Kim, S.W., 2008. Hydrogen production condition from
food waste by dark fermentation with Clostridium beijerinckii KCTC 1785.
Biotechnol. Bioprocess Eng. 13, 499–504.
Kuo, W., Cheng, K., 2007. Use of respirometer in evaluation of process and toxicity of
thermophilic anaerobic digestion for treating kitchen waste. Bioresour. Technol.
98, 1805–1811.
Lastella, G., Testa, C., Cornacchia, G., Notornicola, M., Voltasio, F., Sharma, V.K., 2002.
Anaerbic digestion of semi-solid organic waste: biogas production and its
purification. Energy Conserv. Manage. 43, 63–75.
Lata, K., Rajeshwari, K.V., Pant, D.C., Kishore, V.V.N., 2002. Volatile fatty acid
production during anaerobic mesophilic digestion of tea and vegetable market
wastes. W. J. Microbiol. Biotechnol. 18, 589–592.
Lee, J., Song, J., Hwang, S., 2009a. Effects of acid pre-treatment on bio hydrogen
production and microbial communities during dark fermentation. Bioresour.
Technol. 100, 1491–1493.
Lee, D.H., Behera, S.K., Kim, J., Park, H.S., 2009b. Methane production potential of
leachate generated from Korean food waste recycling facilities: a lab scale
study. Waste Manage. 29, 876–882.
Lee, M., Hidaka, T., Hagiwara, W., Tsuno, H., 2009c. Comparative performance and
microbial diversity of hyperthermophiclic and thermophilic co-digestion of
kitchen garbage and excess sludge. Bioresour. Technol. 100, 578–585.
Lei, Z., Chen, J., Zhang, Z., Sugiura, N., 2010. Methane production from rice straw
with acclimated anaerobic sludge: effect of phosphate supplementation.
Bioresour. Technol. 101, 4343–4348.
Lesteur, M., Bellon-Maurel, V., Gonzalez, C., Latrille, E., Roger, J.M., Junqua, G., Steyer,
J.P., 2010. Alternative methods for determining anaerobic biodegradability: a
review. Process Biochem. 45, 431–440.
Linke, B., Heiermann, M., Mumme, J., 2006. Results of monitoring the pilot plants
Pirow and Clausnitz. In: Rohstoffe, F.N. (Ed.), Solid-State Digestion–State of the
Art and Further R&D Requirements, vol. 24. Gülzower Fachgespräche, pp. 112–
130.
Liu, C., Yuan, X., Zeng, G., Li, W., Li, J., 2008. Prediction of methane yield at optimum
pH for anaerobic digestion of organic fraction of municipal solid waste.
Bioresour. Technol. 99, 882–888.
Lo, H.M., Kurniawan, T.A., Sillanpaa, M.E.T., Pai, T.Y., Chiang, C.F., Chao, K.P., Liu,
M.H., Chuang, S.H., Banks, C.J., Wang, S.C., Lin, K.C., Lin, C.Y., Liu, W.F., Cheng,
P.H., Chen, C.K., Chiu, H.Y., Wu, H.Y., 2010. Modeling biogas production from
organic fraction of MSW co-digested with MSWI ashes in anaerobic bioreactors.
Bioresour. Technol. 101, 6329–6335.
Lopes, W.S., Leite, V.D., Prasad, S., 2004. Influence of inoculum on performance of
anaerobic reactors for treating municipal solid waste. Bioresour. Technol. 94,
261–266.
Luo, G., Xie, L., Zhou, Q., Angelidaki, I., 2011. Enhancement of bioenergy
production from organic wastes by two-stage anaerobic hydrogen and
methane production process. Bioresour. Technol. doi: 10.1016/j.biortech.
2011.02.012.
Martin-Gonzalez, L., Colturato, L.F., Font, X., Vicent, T., 2010. Anaerobic co-digestion
of the organic fraction of municipal solid waste with FOG waste from a sewage
treatment plant: recovering a wasted methane potential and enhancing the
biogas yield. Waste Manage. 30, 1854–1859.
Mumme, J., Linke, B., Tölle, R., 2010. Novel upflow anaerobic solid-state (UASS)
reactor. Bioresour. Technol. 101, 592–599.
387
Table of Contents
Nath, K., Das, D., 2004. Improvement of fermentative hydrogen production: various
approaches. Appl. Microbiol. Biotechnol. 65, 520–529.
Nayono, S.E., Gallert, C., Winter, J., 2010. Co-digestion of press water and food waste
in a biowaste digester for improvement of biogas production. Bioresour.
Technol. 101, 6987–6993.
Parawira, W., Murto, M., Zvauya, R., Mattiasson, B., 2004. Anaerobic batchdigestion
of solid potato waste alone and in combination with sugar beet leaves. Renew.
Energy 29, 1811–1823.
Park, C., Lee, C., Kim, S., Chen, Y., Chase, H.A., 2005. Upgrading of anaerobic digestion by
incorporating two different hydrolysis processes. J. Biosci. Bioeng. 100, 164–167.
Park, Y., Tsuno, H., Hidaka, T., Cheon, J., 2008. Evaluation of operational parameters
in thermophilic acid fermentation of kitchen waste. J. Mater. Cycl. Waste
Manage. 10, 46–52.
Rao, A.G., Prakash, S.S., Joseph, J., Reddy, A.R., Sarma, P.N., 2011. Multi stage high
rate biomethanation of poultry litter with self mixed anaerobic digester.
Bioresour. Technol. 102, 729–735.
Riano, B., Molinuevo, B., Garcia-Gonzalez, M.C., 2011. Potential for methane
production from anaerobic co-digestion of swine manure with winery
wastewater. Bioresour. Technol. 102, 41–4136.
Riau, V., De la Rubia, M.A., Pérez, M., 2010. Temperature-phased anaerobic digestion
(TPAD) to obtain class A biosolids: a semi-continuous study. Bioresour. Technol.
101, 2706–2712.
Sawayama, S., Tada, C., Tsukahara, K., Yagishita, T., 2004. Effect of ammonium
addition on methanogenic community in a fluidized bed anaerobic digestion. J.
Biosci. Bioen. 97, 65–70.
Sosnowski, P., Wieczorek, A., Ledakowicz, S., 2003. Anaerobic co-digestion of
sewage sludge and organic fraction of municipal solid wastes. Adv. Environ. Res.
7, 609–616.
Sterling, M.C.Jr., Lacey, R.E., Engler, C.R., Ricke, S.C., 2001. Effects of ammonia
nitrogen on H2 and CH4 production during anaerobic digestion of dairy cattle
manure. Bioresour. Technol. 77, 9–18.
Steyer, J.P., Bouvier, J.C., Conte, T., Gras, P., Sousbie, P., 2002. Evaluation of a four year
experience with a fully instrumented anaerobic digestion process. Water Sci.
Technol. 45, 495–502.
Su, H., Cheng, J., Zhou, J., Song, W., Cen, K., 2009. Improving hydrogen production
from cassava starch by combination of dark and photo fermentation. Int. J. Hydr.
Energy 34, 1780–1786.
Themelis, N.J., Ulloa, P.A., 2007. Methane generation in landfills. Renew. Energy 32,
1243–1257.
Torres, M.L., de Llorens, M.C.E., 2008. Effect of alkaline pretreatment on anaerobic
digestion of solid wastes. Waste Manage. 28, 2229–2234.
Troschinetz, A.M., Mihelcic, J.R., 2009. Sustainable recycling of municipal solid
waste in developing countries. Waste Manage. 29, 915–923.
Trzcinski, A.P., Stuckey, D.C., 2010. Treatment of municipal solid waste leachate
using a submerged anaerobic membrane bioreactor at mesophilic and
psychrophilic temperatures: analysis of recalcitrants in the permeate using
GC-MS. Water Res. 44, 671–680.
Trzcinski, A.P., Ray, M.J., Stuckey, D.C., 2010. Performance of a three-stage
membrane bioprocess treating the organic fraction of municipal solid waste
and evolution of its archaeal and bacterial ecology. Bioresour. Technol. 101,
1652–1661.
Vogt, G.M., Liu, H.W., Kennedy, K.J., Vogt, H.S., Holbein, B.E., 2002. Super blue box
recycling (SUBBOR) enhanced two-stage anaerobic digestion process for
recycling municipal solid waste: laboratory pilot studies. Bioresour. Technol.
85, 291–299.
Walker, M., Banks, C.J., Heaven, S., 2009. Two-stage anaerobic digestion of
biodegradable municipal solid waste using a rotating drum mesh filter
bioreactor and anaerobic filter. Bioresour. Technol. 100, 4121–4126.
Wang, Q., Kuninobu, M., Kakimoto, K., Ogawa, H.I., Kato, Y., 1999. Upgrading of
anaerobic digestion of waste activated sludge by ultrasonic pretreatment.
Bioresour. Technol. 68, 309–313.
Ward, A.J., Hobbs, P.J., Holliman, P.J., Jones, D.L., 2008. Optimization of the anaerobic
digestion of agricultural resources. Bioresour. Technol. 99, 7928–7940.
Weiland, P., 2006. State of the art of solid-state digestion–recent developments. In:
Rohstoffe, F.N. (Ed.), Solid-State Digestion–State of the Art and Further R&D
Requirements, vol. 24. Gulzower Fachgespräche, pp. 22–38.
William, P.B., David, C.S., 1999. The use of the anaerobic baffled reactor (ABR) for
wastewater treatment: a review. Water Res. 33, 1559–1578.
Xing, W., Ngo, H.H., Guo, W., Wu, Z., Nguyen, T.T., Cullum, P., Listowski, A., Yang,
N., 2010. Enhancement of the performance of anaerobic fluidized bed
bioreactors (AFBBRs) by a new starch based flocculant. Separat. Purif.
Technol. 72, 140–146.
Yang, S.T., Okos, M.R., 1987. Kinetic study and mathematical modeling of
methanogenesis of acetate using pure cultures of methanogens. Biotechnol.
Bioeng. 30, 661–667.
Yu, H., Huang, G.H., 2009. Effects of sodium as a pH control amendment on the
composting of food waste. Bioresour. Technol. 100, 2005–2011.
Zhao, Y., Wang, A., Ren, N., 2010. Effect of carbon sources on sulfidogenic bacterial
communities during the starting-up of acidogenic sulfate-reducing bioreactors.
Bioresour. Technol. 101, 2952–2959.
Zhang, L., Lee, Y.W., Jahng, D., 2011. Anaerobic co-digestion of food waste and
piggery wastewater: focusing on the role of trace elements. Bioresour. Technol.
doi: 10.1016/j.biortech.2011.01.082.
Zhu, B., Gikas, P., Zhang, R., Lord, J., Jenkins, B., Li, X., 2009. Characteristics and biogas
production potential of municipal solid wastes pretreated with a rotary drum
reactor. Bioresour. Technol. 100, 1122–1129.
388