This also means that with mixed spinning culturing equipment and the same added
substrate concentration, reduced solid retention time is associated with increased
organic matter load.
Chynoweth reported that while increased organic matter load lowered methane
yields, it also increased concentrations of acetic acid and short-chain fatty acids
such as propionic and butyric acid. This means that along with hydrolysis of algal
body biomass, the methane production process can also easily become a
rate-limiting step in the methane fermentation of algae biomass.
With methane fermentation of algae, high concentrations of salt are present in
the biomass. Reduced methane fermentation due to these salts can also be a
problem with non-algae biomass. The major factor causing the reduced fermentation is the low salt tolerance of the methane-producing bacteria that decompose
acetic acid. Accordingly, it is also important to increase the organic matter load by
raising methane-producing bacteria activity through desalinization.
Anaerobic decomposition is typically performed at two temperature ranges,
medium (35 °C) and high (55 °C). The types of microorganisms that function at
each temperature range vary greatly, but both can be used for processing of algae
biomass.
Otsuka et al. obtained a methane yield of 180 ml/g-VS through anaerobic
decomposition of Ulva at medium temperature. Comparison of methane yields in
VS terms for anaerobic decomposition of a Scenedesmus spp. and Chlorella
spp. mixture under medium- and high-temperature conductions in terms showed
high-temperature fermentation to result in increased organic acid decomposition
and improved methane yields compared to medium-temperature fermentation (Otsuka et al. 2004).
Hansson used a mixture of sea lattus (Ulva), sea lattus (Cladophora), and
Chaetomorpha collected from the coastal Baltic Sea to compare characteristics
from methane fermentation at medium and high temperatures. Medium-temperature
fermentation resulted in methane yields of 250–350 ml/g-added VS-1 and VS
decomposition rates of 50–55%, indicating superior performance relative to
high-temperature fermentation (Hansson 1983; Prabandono and Amin 2015).
9.3.6 Equipment for Methane Fermentation of Algae
The design of biogas plants, which are key to the methane fermentation process, is
determined to some extent by physical characteristics such as the viscosity and
settling of organic waste and flora. Traditionally, methane fermentation has
involved the use of continuously supplied water and a spinner to mix the
methane-producing bacteria in the form of a continuous stirred tank reactor (CSTR)
or a completely mixed tank reactor using internal circulation of gas or culturing
solution (Fig. 9.5b).
This approach is often used today with surplus sewage sludge and livestock
excreta processing, as it is structurally simple to remain and mainly and allows for
simultaneous processing of solids. Obviously, it can also be used as a tank for
9.3 Methane Production from Algae
311
substrate concentration, reduced solid retention time is associated with increased
organic matter load.
Chynoweth reported that while increased organic matter load lowered methane
yields, it also increased concentrations of acetic acid and short-chain fatty acids
such as propionic and butyric acid. This means that along with hydrolysis of algal
body biomass, the methane production process can also easily become a
rate-limiting step in the methane fermentation of algae biomass.
With methane fermentation of algae, high concentrations of salt are present in
the biomass. Reduced methane fermentation due to these salts can also be a
problem with non-algae biomass. The major factor causing the reduced fermentation is the low salt tolerance of the methane-producing bacteria that decompose
acetic acid. Accordingly, it is also important to increase the organic matter load by
raising methane-producing bacteria activity through desalinization.
Anaerobic decomposition is typically performed at two temperature ranges,
medium (35 °C) and high (55 °C). The types of microorganisms that function at
each temperature range vary greatly, but both can be used for processing of algae
biomass.
Otsuka et al. obtained a methane yield of 180 ml/g-VS through anaerobic
decomposition of Ulva at medium temperature. Comparison of methane yields in
VS terms for anaerobic decomposition of a Scenedesmus spp. and Chlorella
spp. mixture under medium- and high-temperature conductions in terms showed
high-temperature fermentation to result in increased organic acid decomposition
and improved methane yields compared to medium-temperature fermentation (Otsuka et al. 2004).
Hansson used a mixture of sea lattus (Ulva), sea lattus (Cladophora), and
Chaetomorpha collected from the coastal Baltic Sea to compare characteristics
from methane fermentation at medium and high temperatures. Medium-temperature
fermentation resulted in methane yields of 250–350 ml/g-added VS-1 and VS
decomposition rates of 50–55%, indicating superior performance relative to
high-temperature fermentation (Hansson 1983; Prabandono and Amin 2015).
9.3.6 Equipment for Methane Fermentation of Algae
The design of biogas plants, which are key to the methane fermentation process, is
determined to some extent by physical characteristics such as the viscosity and
settling of organic waste and flora. Traditionally, methane fermentation has
involved the use of continuously supplied water and a spinner to mix the
methane-producing bacteria in the form of a continuous stirred tank reactor (CSTR)
or a completely mixed tank reactor using internal circulation of gas or culturing
solution (Fig. 9.5b).
This approach is often used today with surplus sewage sludge and livestock
excreta processing, as it is structurally simple to remain and mainly and allows for
simultaneous processing of solids. Obviously, it can also be used as a tank for
9.3 Methane Production from Algae
311