during this phase (10
8 ) are capable of degrading cellulose
and solubilizing lignin and tolerate higher temperatures than
fungi. They are therefore important agents of lignocellulose
degradation during the thermophilic phase. Concentration
of mesophilic fungi decreases (10
3 ) and that of the thermophiles increases (10
7 ). Thermophilic fungi presenting
ligninocellulolytic capacity have been isolated from various
composts (Tuomela et al. 2000). During the cooling phase,
mesophilic bacteria reappear (10
11 ), the concentration of
thermophiles decreases but remains high (10
7 ).
Regarding the thermophilic microorganisms in the cattle
and poultry compost manure, 34 thermophilic bacteria
grouped into five genera were isolated based on phylogenetic analysis of 16S rRNA: Ureibacillus, Bacillus,
Geobacillus, Brevibacillus, and Paenibacillus (Wang et al.
2007). Thermophilic actinobacteria belonging to the genera
Nocardia, Streptomyces, Thermoactinomyces, and Micromonospora were also isolated (Tuomela et al. 2000)
Works by Ryckeboer and collaborators (2003) illustrate
the variations in the concentrations of different populations
in compost. These authors report the almost complete
disappearance of fungi and streptomycetes when the temperature reaches 76
C and their reappearance during the
cooling phase.
16.5.3.4 The Different Composting Methods
Composting processes are numerous and vary according to
the type of waste to be treated and their volume. However,
for all type of treatments, i.e., implemented by an individual
(home composting) or at an industrial level, the processes
that occur within compost remain the same. A major concern
for the success of composting is to maintain aerobic
conditions throughout the compost, heterogeneous environment in which gradients of temperature and humidity establish, with the formation of numerous anaerobic microniches,
particularly during the two phases of intensive degradation
when the consumption of oxygen by microorganisms is
particularly high. The challenge is that the oxygen content
in the pores of the compost should not be less than 5 % of the
total volume of the treated organic material, in order to
prevent the occurrence of complete anaerobic conditions.
Two types of processes capable of ensuring good
oxygenation of the compost can be implemented:
(i) Windrow composting: compost is thus arranged in rows
to facilitate engine handling during the necessary regular shuffling. Another technique is to blow air at the base
of compost heaps using perforated pipes embedded in
the swath. It is also possible to combine shuffling and
ventilation.
(ii) Composting in sealed rooms with ventilation by mechanical turning. A first device is to contain the compost in
lockers (walls with usually a roof) or between walls that
form long and narrow corridors. Compost can also be
treated in silos or in bioreactors (Sharma et al. 1997).
In both types of processes, there is a biostimulation of the
activity of aerobic microorganisms by oxygen supplying.
Microorganisms can be added during the processing
(biostimulation).
16.5.4 Anaerobic Treatments and
Methanization
16.5.4.1 Definition
Unlike composting, biological processes involved are
expressed under anaerobic conditions and result in the
formation of biogas, especially methane (cf. Sect. 14.2.6).
The objectives of this biotechnology are to reduce the
amount of organic biomass waste and to retrieve and use
the biogas produced during the treatment. A remediation
technique is coupled with a technique for production of
renewable energy. Compared to aerobic degradation of
waste, the anaerobic degradation has three advantages:
(i) In terms of energy, it is self-sufficient and even can
produce extra energy, because the biogas can be
converted into heat, electricity, or fuel for vehicles
(cars, buses) (e.g., the city of Lille (France)).
(ii) Because the degradation is done in sealed reactors,
odors are greatly reduced.
(iii) The surface used is limited.
The main disadvantage of this treatment is its cost which
is higher than that of composting.
16.5.4.2 Principle of Methane Fermentation
and Microorganisms Involved
in the Process
Mechanisms
and
microorganisms
involved
in
methanization, which is a natural anaerobic process, have
been described previously (cf. Sect. 14.2.6).
Anaerobic digestion involves four main steps (Figs. 14.14
and 16.18):
(i) Hydrolysis of macromolecules
(ii) Formation of volatile fatty acids
(iii) Formation of acetic acid and production of hydrogen
and CO 2
(iv) Production of biogas
The degraded organic matter is largely identical to that
treated by composting, essentially consisting of urban sewage, food waste, the organic fraction of domestic waste, and
livestock effluents. Waste is treated in a digester (whose
volume can vary from a few hundred to several thousand
m
3 ), which can operate in continuous, semicontinuous, or
discontinuous mode.
Depending on the temperature, three modes of production
are defined, called psychrophilic (15–25
C), mesophilic
(25–45
C), and thermophilic (55–65
C). Microorganisms
can be free or attached (biofilm formation). The process
results in the formation of biogas, and the degradation yields
16 Applied Microbial Ecology and Bioremediation
679
8 ) are capable of degrading cellulose
and solubilizing lignin and tolerate higher temperatures than
fungi. They are therefore important agents of lignocellulose
degradation during the thermophilic phase. Concentration
of mesophilic fungi decreases (10
3 ) and that of the thermophiles increases (10
7 ). Thermophilic fungi presenting
ligninocellulolytic capacity have been isolated from various
composts (Tuomela et al. 2000). During the cooling phase,
mesophilic bacteria reappear (10
11 ), the concentration of
thermophiles decreases but remains high (10
7 ).
Regarding the thermophilic microorganisms in the cattle
and poultry compost manure, 34 thermophilic bacteria
grouped into five genera were isolated based on phylogenetic analysis of 16S rRNA: Ureibacillus, Bacillus,
Geobacillus, Brevibacillus, and Paenibacillus (Wang et al.
2007). Thermophilic actinobacteria belonging to the genera
Nocardia, Streptomyces, Thermoactinomyces, and Micromonospora were also isolated (Tuomela et al. 2000)
Works by Ryckeboer and collaborators (2003) illustrate
the variations in the concentrations of different populations
in compost. These authors report the almost complete
disappearance of fungi and streptomycetes when the temperature reaches 76
C and their reappearance during the
cooling phase.
16.5.3.4 The Different Composting Methods
Composting processes are numerous and vary according to
the type of waste to be treated and their volume. However,
for all type of treatments, i.e., implemented by an individual
(home composting) or at an industrial level, the processes
that occur within compost remain the same. A major concern
for the success of composting is to maintain aerobic
conditions throughout the compost, heterogeneous environment in which gradients of temperature and humidity establish, with the formation of numerous anaerobic microniches,
particularly during the two phases of intensive degradation
when the consumption of oxygen by microorganisms is
particularly high. The challenge is that the oxygen content
in the pores of the compost should not be less than 5 % of the
total volume of the treated organic material, in order to
prevent the occurrence of complete anaerobic conditions.
Two types of processes capable of ensuring good
oxygenation of the compost can be implemented:
(i) Windrow composting: compost is thus arranged in rows
to facilitate engine handling during the necessary regular shuffling. Another technique is to blow air at the base
of compost heaps using perforated pipes embedded in
the swath. It is also possible to combine shuffling and
ventilation.
(ii) Composting in sealed rooms with ventilation by mechanical turning. A first device is to contain the compost in
lockers (walls with usually a roof) or between walls that
form long and narrow corridors. Compost can also be
treated in silos or in bioreactors (Sharma et al. 1997).
In both types of processes, there is a biostimulation of the
activity of aerobic microorganisms by oxygen supplying.
Microorganisms can be added during the processing
(biostimulation).
16.5.4 Anaerobic Treatments and
Methanization
16.5.4.1 Definition
Unlike composting, biological processes involved are
expressed under anaerobic conditions and result in the
formation of biogas, especially methane (cf. Sect. 14.2.6).
The objectives of this biotechnology are to reduce the
amount of organic biomass waste and to retrieve and use
the biogas produced during the treatment. A remediation
technique is coupled with a technique for production of
renewable energy. Compared to aerobic degradation of
waste, the anaerobic degradation has three advantages:
(i) In terms of energy, it is self-sufficient and even can
produce extra energy, because the biogas can be
converted into heat, electricity, or fuel for vehicles
(cars, buses) (e.g., the city of Lille (France)).
(ii) Because the degradation is done in sealed reactors,
odors are greatly reduced.
(iii) The surface used is limited.
The main disadvantage of this treatment is its cost which
is higher than that of composting.
16.5.4.2 Principle of Methane Fermentation
and Microorganisms Involved
in the Process
Mechanisms
and
microorganisms
involved
in
methanization, which is a natural anaerobic process, have
been described previously (cf. Sect. 14.2.6).
Anaerobic digestion involves four main steps (Figs. 14.14
and 16.18):
(i) Hydrolysis of macromolecules
(ii) Formation of volatile fatty acids
(iii) Formation of acetic acid and production of hydrogen
and CO 2
(iv) Production of biogas
The degraded organic matter is largely identical to that
treated by composting, essentially consisting of urban sewage, food waste, the organic fraction of domestic waste, and
livestock effluents. Waste is treated in a digester (whose
volume can vary from a few hundred to several thousand
m
3 ), which can operate in continuous, semicontinuous, or
discontinuous mode.
Depending on the temperature, three modes of production
are defined, called psychrophilic (15–25
C), mesophilic
(25–45
C), and thermophilic (55–65
C). Microorganisms
can be free or attached (biofilm formation). The process
results in the formation of biogas, and the degradation yields
16 Applied Microbial Ecology and Bioremediation
679