Title of Invention

"A METHOD FOR PRODUCING A BIOGAS"

Abstract The present invention relates to a method for producing a biogas, comprising the step of generating a biogas mainly composed of hydrogen by performing hydrogen fermentation while adding a hop or hop component to a liquid to be processed containing glucide so as to inactivate a contaminant microorganism inhibiting hydrogen generation without affecting a growth or activity of a hydrogen-fermenting microorganism, wherein the hydrogen fermentation is performed under a condition with a pH 6.0 to 7.5 and a temperature of 20°C to 70°C, wherein the hop or hop component are selected from the group consisting of chemically modified hop such as hop strobiles, hop pellets, hop extracts, isomerized hop pellets, tetrahydroisofumulones; hop α-acid; and hop ß-acid.
Full Text DESCRIPTION
Process for Producing Biogas
Technical Field
[0001] The present invention relates to a production method of biogas which is useful as an energy
gas.
Background Art
[0002] Anaerobic fermentation using microorganisms has been known as a method of converting
biomasses such as organic wastes and organic waste water into energy. The anaerobic fermentation is a
fermentation scheme in which an acid generating step from an organic matter and a methane generating
step of generating methane from an organic acid generated by the acid generating fermentation usually
proceed as multiple parallel fermentation, whereby a fermentation gas mainly composed of methane can
be obtained as an energy gas.
[0003] However, the energy obtained by boiler combustion of methane is heat, so that it is not suitable
for applications requiring no heat utilization, but is limited to those directly utilizing the heat of
combustion, those converting the heat into steam, and the like. Methane fuel batteries convert the
resulting energy into electric power, whereby their usage is broader than the heat utilization. However,
a so-called reforming reaction for generating hydrogen from methane requires a reformer and heating of
a material methane gas. Usually, the heat of combustion of methane is utilized as a heat source
therefor, and its thermal energy is collected by a technique such as warm water manufacture from the
viewpoint of effective energy utilization. As a result, the methane fuel battery utilization also needs to
use thermal energy.
[0004] In the acid generating step in anaerobic fermentation, on the other hand, a fermentation gas
mainly composed of hydrogen has been known to occur. Hydrogen is quite useful, since it is not
problematic in terms of thermal energy like methane. For example, hydrogen is advantageous in that
no reforming reaction is necessary when used in a fuel battery, so that a large part of generated
hydrogen can be fed to the fuel battery and converted into electric power. Hence, a technique for
generating a fermentation gas mainly composed of hydrogen and a fermentation gas mainly composed
of methane separately from each other at the time of anaerobic fermentation has been proposed (see, for
example, Patent Documents 1,2, and 3).
[Patent Document 1 ] Japanese Patent Application Laid-Open No. SHO 61 -8200
[Patent Document 2] Japanese Patent Application Laid-Open No. 2001 -149983
[Patent Document 3] Japanese Patent Application Laid-Open No. 2003-135089
Disclosure of the Invention
Problem to be Solved by the Invention
[0005] However, even the above-mentioned conventional methods are not easy to perform hydrogen
fermentation smoothly at a practical level. Namely, it has been reported that there are cases where
biomasses to become materials contain contaminant bacteria such as lactic acid bacteria other than
hydrogen-generating bacteria, and these contaminant bacteria inhibit the hydrogen fermentation (Noike
et al., Inhibition of hydrogen fermentation of organic wastes by lactic acid bacteria, International
Journal of Hydrogen Energy, Vol. 27, pp. 1367-1371,2002).
[0006] As a method overcoming this problem, the above-mentioned Patent Document 3 discloses a
method of inactivating hydrogen fermentation inhibiting bacteria in a material by subjecting a biomass
to be hydrogen-fermented to a heating/warming process beforehand. However, thermal energy is
necessary for such a heating/warming process, whereby it does not become a fundamental solution.
Patent Documents 1 and 2 do not mention the above-mentioned problem at all. Namely, the first object
of the fermenting process for collecting an energy gas from a biomass employed as a material is to
process wastes or waste water of the biomass. Therefore, the process must decompose the biomass so
as to reduce its volume greatly and lower the load due to the waste water. In this operation, because of
characteristics of waste processing and waste water processing, an excess of energy input for the
operation and process greatly lowers the processing efficiency and remarkably deteriorates the industrial
usefulness.
[0007] In view of such circumstances, it is an object of the present invention to provide a production
method of a biogas, which can sufficiently smoothly perform hydrogen fermentation or hydrogen
fermentation and methane fermentation when using a hydrogen-fermenting microorganism to carry out
the hydrogen fermentation from an organic matter such as a biomass as a material or when carrying out
the methane fermentation after the hydrogen fermentation, without subjecting the material to a
treatment of the material involving consumption of thermal energy such as heating/warming.
Means for Solving the Problem
[0008] The inventors conducted diligent studies in order to achieve the above-mentioned object and,
as a result, have initially found that whether the hydrogen generation by a hydrogen-fermenting
microorganism and growth of the hydrogen-fermenting microorganism or the growth of a
microorganism group such as lactic acid bacteria which adversely affects the hydrogen fermentation and
fermentation by the microorganism group become dominant depend on the concentration of a
predetermined substrate contained in a liquid to be processed. Further studies based on this finding
have revealed that the above-mentioned problem is overcome when the concentration of the substrate in
the liquid to be processed is kept within an appropriate range in practice according to a correlation
between the concentration of the substrate and the rate of consumption of the substrate by the hydrogenfermenting
microorganism, whereby the present invention is achieved.
[0009] Namely, the present invention provides a production method of a biogas, the method
comprising a first step of determining, according to a correlation between a concentration of a
predetermined substrate in a liquid to be processed containing an organic matter and a rate of
consumption of the substrate by a hydrogen-fermenting microorganism, a maximum tolerable
concentration of the substrate consumable by the hydrogen-fermenting microorganism; and a second
step of generating a biogas mainly composed of hydrogen by causing the hydrogen-fermenting
microorganism to hydrogen-ferment the liquid to be processed while keeping the substrate in the liquid
to be processed at a concentration not higher than the maximum tolerable concentration.
[0010] In the case where the maximum tolerable concentration of a substrate consumable by a
hydrogen-fermenting microorganism is determined beforehand according to the correlation between the
concentration of the substrate in a liquid to be processed containing an organic matter and the rate of
consumption of the substrate by the hydrogen-fermenting microorganism, and the concentration of the
substrate in the liquid is kept at a level not higher than the maximum tolerable concentration when
performing hydrogen fermentation in practice as such, the organic matter, which is a material, is
predominantly consumed by the hydrogen-fermenting microorganism, whereby the growth of
microorganisms (contaminant microorganisms) such as lactic bacteria adversely affecting the growth or
activity of the hydrogen-fermenting microorganism and their resulting fermentation are sufficiently
suppressed. Therefore, the present invention can sufficiently prevent the contaminant microorganisms
from inhibiting the hydrogen fermentation without a treatment of the material involving consumption of
thermal energy such as heating/warming, whereby the hydrogen fermentation can be performed
sufficiently smoothly.
[0011] Preferably, in the present invention, the substrate to become an index of the hydrogen
fermentation is a glucide. Using a glucide as an index, determining its maximum tolerable
concentration, and keeping the glucide concentration at a level not higher than the maximum tolerable
concentration when performing the hydrogen fermentation in practice as such can more reliably prevent
contaminant microorganisms from inhibiting the hydrogen fermentation, whereby the hydrogen
fermentation can be carried out more smoothly.
[0012] Preferably, the production method of a biogas in accordance with the present invention further
comprises a third step of generating a fermentation gas mainly composed of methane by causing a
methane-fermenting microorganism to methane-ferment the fermented liquid after the hydrogen
fermentation in the second step. When the fermented liquid after the hydrogen fermentation in the
second step is subjected to methane fermentation, contaminant products are sufficiently restrained from
inhibiting the methane fermentation. Therefore, a fermentation gas mainly composed of hydrogen and
a fermentation gas mainly composed of methane can be generated separately and sufficiently smoothly.
Also, providing the third step is quite useful in terms of reducing the volume of organic wastes,
lowering the environmental load due to organic waste water, etc.
[0013] The present invention provides a production method of a biogas, the method comprising the
step of generating a biogas mainly composed of hydrogen by performing hydrogen fermentation while
adding a hop or hop component to a liquid to be processed containing an organic matter so as to
inactivate a contaminant microorganism inhibiting hydrogen generation without affecting a growth or
activity of a hydrogen-fermenting microorganism.
[0014] Hops and hop components have been known to exhibit antibacterial actions against wide
ranges of microorganisms. For example, Simpson, WJ. et al. reported antibacterial activities against
lactic acid bacteria, Lactobacillus brevis (Simpson, W.J. et al., Factors affecting antibacterial activity of
hops and their derivatives, J. Appl. Bacteriol., vol. 72, pp. 327-334, 1992), whereas Plollach G. et al.
reported that hop beta acid restrained microorganisms from generating lactic acid, nitrous acid, acetic
acid, and butyric acid (Plollach G. et al., Einsatz von Hophenprodukten als Bacteriostaticum in der
Zuckerindustrie, Zuckerindustrie, vol. 121, pp. 919-926, 1996; Hein, W. et al., Neue Erkenntnisse beim
Einsatz von Hopfenprodukten in der Zuckerindustrie, Zuckerindustrie, vol. 122, pp. 940-949, 1997;
Plollach, G. et al., Neue Erkenntnisse zur Losungmikrobieller Probleme in Zuckerfabriken,
Zuckerindustrie, vol. 124, pp. 622-637, 1999). On the other hand, cases with resistivity were also
reported, whereby effective functions have not always been established conventionally. For example,
Simpson, W.J. et al. reported that genera Pediococcus and Lactobacillus exhibited hop resistivities
(Simpson, W.J. et al., Cambridge Prize Lecture, Studies on the Sensitivity of Lactic Acid Bacteria to
Hop Bitter Acids, J. Inst. Brew., vol. 99, pp. 405-411, 1993); Sami, M. reported that Lactobacillus
brevis strain exhibited a hop resistivity (Sami, M., Lactic Acid Bacteria Deteriorating Beer, Journal of
the Brewing Society of Japan, vol. 94, pp. 2-9, 1999); and so forth. The inventors studied this point
and, as a result, have verified that appropriately setting conditions such as method of utilization and
amount of use of a hop or hop component effectively suppresses the activity of microorganisms which
adversely affect the activity of hydrogen-fermenting microorganisms and does not inhibit the growth
and activity of the hydrogen-fermenting microorganisms, whereby the possibility of effectively utilizing
the hop or hop component in hydrogen fermentation has been clarified. The above-mentioned
production method of a biogas sufficiently prevents contaminant microorganisms from inhibiting
hydrogen fermentation without performing a treatment of the material involving consumption of
thermal energy such as heating/warming, thereby making it possible to carry out hydrogen fermentation
sufficiently smoothly.
Effect of the Invention
[0015] As mentioned above, according to the present invention, when using a hydrogen-fermenting
microorganism to carry out the hydrogen fermentation from an organic matter as a material, the
hydrogen fermentation can be performed sufficiently smoothly without a treatment of the material
involving consumption of thermal energy such as heating/warming.
Brief Description of the Drawings
[0016] Fig. 1 is a block diagram showing an example of biogas generating apparatus favorably used in
the present invention.
Fig. 2 is a graph showing the correlation between the number of days of fermentation and the hydrogen
and carbon dioxide concentrations in the fermentation gas, which was obtained by Example 1.
Fig. 3 is a graph showing the correlation between the number of days of fermentation and the hydrogen
and carbon dioxide concentrations in the fermentation gas, which was obtained by Example 3.
Fig. 4 is a graph showing the correlation between the number of days of fermentation and the hydrogen
and carbon dioxide concentrations in the fermentation gas, which was obtained by Example 4.
Fig. 5 is a graph showing the correlation between the number of fermentation sessions and the hydrogen
and carbon dioxide concentrations in the fermentation gas, which was obtained by Example 6.
Fig. 6 is a graph showing the correlation between the number of days of fermentation and the hydrogen
and carbon dioxide concentrations in the fermentation gas, which was obtained by Example 8.
Fig. 7 is a graph showing the correlation between the species of material supply liquids and the
hydrogen and carbon dioxide concentrations in the fermentation gas, which was obtained by Example 9.
Fig. 8 is a graph showing the correlation between the number of days of fermentation and the methane
and carbon dioxide concentrations in the fermentation gas, which was obtained by Example 10.
Explanations of letters or numerals
[0017] 1.. .a hydrogen fermentation tank, 2.. .a methane fermentation tank, LI to L5.. .lines
Best Modes for Carrying Out the Invention
[0018] In the following, preferred embodiments of the present invention will be explained in detail.
[0019] Fig. 1 is a block diagram showing an example of biogas production apparatus preferably used
in the present invention. The apparatus shown in Fig. 1 comprises a hydrogen fermentation tank 1 and
a methane fermentation tank 2, thereby carrying out hydrogen/methane two-stage fermentation by a
continuous operation.
[0020] The hydrogen fermentation tank 1 is provided with a line LI, whereas a liquid to be processed
containing an organic matter is fed to the hydrogen fermentation tank 1 by way of the line LI. The
liquid to be processed is not limited in particular as long as it contains an organic matter which can be
hydrogen-fermented by a hydrogen-fermenting microorganism. The hydrogen fermentation tank 1 is
useful for processing biomasses such as organic wastes and organic waste water in order to acquire
energy gasses from reusable organic resources among others, and is preferably employed for processing
beer brewery waste water, bakery wastes, etc. in particular.
[0021] A hydrogen-fermenting microorganism is contained in the hydrogen fermentation tank 1. The
hydrogen-fermenting microorganism performs hydrogen fermentation from the organic matter in the
liquid to be processed. Examples of the hydrogen-fermenting microorganism include anaerobic
microorganisms such as Clostridia, Methylotrophs, Methanogens, Rumen Bacteria, and Archae bacteria;
facultative anaerobic microorganisms such as Escherichia coli and Enterobacter; aerobic
microorganisms such as Alcaligenes and Bacillus; photosynthetic bacteria; and Cyanobacteria. The
hydrogen-fermenting microorganism may be either an isolated microorganism or a mixed
microorganism group (microflora) suitable for hydrogen production. For example, the hydrogen
fermentation by an anaerobic microorganism group can be performed by supplying an organic material
such as a biomass to a fermentation tank containing a hydrogen-fermenting microorganism under a
condition with a pH of about 6.0 to 7.5 and a temperature of about 20° to 70°C. When hydrogen
fermentation is effected by such a hydrogen-fermenting microorganism, a fermentation gas (biogas)
mainly composed of hydrogen (H2) and carbon dioxide (CO2) occurs, while organic acids such as acetic
acid, butyric acid, and lactic acid are generated. For example, glucose is decomposed by an action of a
hydrogen-fermenting microorganism into acetic acid (CHsCOOH), hydrogen, and carbon dioxide
according to the following expression (1):
C6Hi2O6 + 2H2O -> 2CH3COOH + 2CO2 + 4H2 (1)
[0022] When causing the hydrogen-fermenting microorganism to perform hydrogen fermentation in
the present invention, according to a correlation between the concentration of a predetermined substrate
in the liquid to be processed and the rate of consumption of the substrate by the hydrogen-fermenting
microorganism, a maximum tolerable concentration of the substrate consumable by the hydrogenfermenting
microorganism is initially determined. Here, the substrate to become an index is not
restricted in particular as long as it correlates with the hydrogen generation by the hydrogen-fermenting
microorganism and the growth of the hydrogen-fermenting microorganism. A preferred substrate is a
glucide.
[0023] The "maximum tolerable concentration of the substrate" refers to the maximum value of
concentration of the substrate allowing the substrate to be consumed predominantly by the hydrogenfermenting
microorganism for the hydrogen fermentation. Namely, when the concentration of the
substrate in the liquid to be processed in the hydrogen fermentation tank 1 is kept at a level not higher
than the maximum tolerable concentration, the substrate is predominantly consumed by the hydrogenfermenting
microorganism, whereby the hydrogen fermentation can be performed sufficiently smoothly.
When the concentration of the substrate exceeds the maximum tolerable concentration, lactic acid
bacteria and the like existing in the organic matter such as a biomass remarkably inhibit hydrogen
fermentation activities, thereby suppressing the hydrogen generation or the growth of hydrogenfermenting
microorganism.
[0024] The maximum tolerable concentration of the substrate can be determined by the following
procedure, for example. First, a plurality of liquids to be processed containing respective
concentrations of a substrate different from each other are prepared, hydrogen fermentation is
performed by using them, and amounts of hydrogen generation at that time are determined. The
concentration of the substrate can be adjusted by changing the dilution ratio of the liquid to be
processed, or adding the substrate to the liquid to be processed. When the substrate to become an index
is a glucide, for example, the glucide concentration in the liquid to be processed can be enhanced if a
polymer polysaccharide such as cellulose, hemicellulose, or starch; an oligosaccharide such as
maltotriose, cellobiose, or cellotriose; a monosaccharide such as pentose or hexose; or the like is added
thereto.
[0025] Next, measured amounts of hydrogen generation are plotted against concentrations of the
substrate, whereby a correlation curve of the substrate concentration vs. hydrogen generation amount is
obtained. In this correlation curve, the hydrogen generation amount usually tends to increase as the
substrate concentration increases, and decrease after attaining a maximum value at a certain
concentration. Since the hydrogen generation amount depends on the rate of consumption of the
substrate by the hydrogen-fermenting microorganism, the concentration yielding the maximum value of
hydrogen generation amount in the correlation curve becomes the maximum tolerable concentration of
the substrate.
[0026] Adding a hop or hop component to the liquid to be processed here can effectively suppress
activities of a microorganism group such as lactic acid bacteria which adversely affect the hydrogen
fermentation. Antibacterial actions due to the hop or hop component do not affect activities of the
hydrogen-fermenting microorganism. Therefore, the addition of the hop or hop component to the
liquid to be processed can enhance the maximum tolerable concentration of the substrate, thereby
further improving the efficiency at the time of performing the hydrogen fermentation in practice.
While the liquid to be processed after the hydrogen fermentation (fermented liquid) is subjected to
methane fermentation which will be explained later, the methane fermentation can be performed more
smoothly if this fermented liquid contains a hop or hop component.
[0027] Preferably employed as the hop or hop component are chemically modified hops such as hop
strobiles, hop pellets, hop extracts, isomerized hop pellets, and tetrahydroisohumulones; hop a-acid; hop
p-acid; and the like.
[0028] According to thus determined maximum tolerable concentration, the hydrogen fermentation is
performed in practice. Namely, the substrate concentration in the supplied liquid to be processed,
respective rates at which the liquid to be processed flows in and out, etc. are adjusted such that the
concentration of the substrate in the hydrogen fermentation tank 1 is not higher than the maximum
tolerable concentration, and a hop or hop component is further added thereto if necessary, whereby the
hydrogen fermentation is performed by the hydrogen-fermenting microorganism. When the organic
matter as a material has the same quality, and fermentation conditions such as temperature and pH
within the hydrogen fermentation tank are unchanged, the amount of growing microorganism existing
in the hydrogen fermentation tank is substantially held constant. In continuous operations, the liquid to
be processed is continuously fed to the hydrogen fermentation tank while being continuously discharged
therefrom, whereby it is desirable that the liquid to be processed be continuously supplied while taking
account of the flow-in and flow-out of the liquid to be processed, the consumption of the organic matter
(or substrate) by microorganisms, etc. Using microorganism immobilization can make the
microorganism keeping amount substantially constant without being influenced by fluctuations in the
material concentration (i.e., substrate concentration) of the liquid to be processed within the hydrogen
fermentation tank (fermented liquid) or fluctuations in the rate at which the liquid to be processed flows
in or out.
[0029] The material balance within the hydrogen fermentation tank 1 in a continuous operation can be
represented by the following expression (2):
V(dS/dt) = FS0 -FS- V(- dS/dt)c (2)
[0030] In expression (2), V is the volume of the liquid to be processed in the hydrogen fermentation
tank, S0 is the substrate concentration in the liquid to be processed flowing in, and dS/dt is the amount
of fluctuation in substrate concentration per unit time. Subscript C indicates that (-dS/dt)c is the
amount of fluctuation due to the consumption by microorganisms. F is the rate at which the liquid to
be processed is supplied and the rate at which the fermented liquid flows when a fixed volume operation
is assumed. Namely, the left side of expression (2) is the amount of fluctuation in substrate
consumption per unit time per fermentation tank, the first term on the right side is the amount of the
substrate flowing in, the second term on the right side is the amount of the substrate flowing out, and the
third term on the right side is the amount of consumption of the substrate by microorganisms.
[0031] In a fermentation operation of generating an energy gas from a biomass, it is important to
maximize the energy gas generation rate per fermentation tank. In this regard, from the viewpoint of
fermentation rate, it is desirable that the microorganism keeping amount in the fermentation tank be
made as large as possible, and that the fermentation tank volume be utilized as much as possible.
When the fermentation operation is regulated at a predetermined temperature and a predetermined pH,
the rate at which the substrate is consumed by microorganisms depends on the microorganism keeping
amount in the fermentation tank assuming that there are no disturbing elements such as mingling of
toxic matters and lack of essential nutrients, whereby the third term on the right side, i.e., V(-dS/dt)c, is
kept at a value as large as possible in practice. Examples of techniques for holding the microorganism
keeping amount in the fermentation tank as much as possible include a process of immobilizing
microorganisms in a microorganism carrier; and a process of forming flocculating microorganism
masses, and filling the fermentation tank with them or floating them therein. Though there is a
technique in which microorganisms are grown and kept at a high concentration in a floating state
without immobilizing them, the microorganism concentration is susceptible to the flow-in of the
material liquid and the rate at which the fermented liquid flows out, whereby it is desirable to employ a
microorganism immobilizing technique.
[0032] In a fermenting operation of producing an energy gas from a biomass or the like, it is important
in terms of apparatus efficiency that that the biomass, which is a fermentation material, to be processed
stably for a long period, so as to produce a fermentation gas stably. Further, from the viewpoint of
waste water processing and the like, the load concentration in the effluent must be kept from fluctuating.
Therefore, it is not desirable for variable terms on the left side of expression (2) to fluctuate unstably, so
that zero-fluctuation operations are important.
[0033] Here, keeping the biomass material concentration such that the biomass material is not used for
the growth and fermentation of the microorganism group such as lactic acid bacteria is synonymous
with keeping the substrate concentration S in the effluent at a level not higher than the maximum
tolerable concentration.
[0034] When the fluctuation on the left side is set to zero according to the view mentioned above,
expression (2) can be rewritten as expression (3 a) or (3b):
(S-S.)/(-dS/dt\=V/F (3a)
F = rx(-ds/dt)e/(s-s.) (3b)
[0035] Assuming that V and (-dS/dt)c are constant since they should be as large as possible and held
constant as mentioned above, it will be sufficient if the material liquid supply and the fermented liquid
flow-out rate F are calculated from the right side of expression (3b) with respect to the substrate
concentration So in the flow-in material liquid in order to keep the substrate concentration S in the
effluent at a predetermined level and operate the substrate consumption variable term per fermentation
tank (left side of expression (2)) so as to prevent it from fluctuating.
[0036] Performing the hydrogen fermentation by the hydrogen-fermenting microorganism as such
generates a fermentation gas (biogas) mainly composed of hydrogen and carbon dioxide, and produces
an organic acid such as acetic acid, butyric acid, or lactic acid. Thus generated biogas is taken out of
the hydrogen fermentation tank 1 by way of a line L2. Though the biogas can be used in a fuel battery
or the like while still in a mixed gas of hydrogen and carbon dioxide, a film separator equipped with a
palladium film which passes hydrogen there through and blocks carbon dioxide may be used so as to
isolate and collect hydrogen with a high purity from the mixed gas. Highly pure hydrogen can also be
obtained by causing the mixed gas to pass through an alkali solution and making the alkali solution
absorb carbon dioxide. On the other hand, the processed liquid (fermented liquid) containing the
organic acid after the hydrogen fermentation is transferred to the methane fermentation tank 2 by way of
a line L3, so as to be subjected to methane fermentation.
[0037] The methane fermentation tank 2 contains a methane-fermenting microorganism. A methanefermenting
microorganism group is usually an ecosystem in which a plurality of species of methanegenerating
bacteria exist. When various methane-generating bacteria such as Methanobacterium,
Methanobrevibacter, Methanosarcina, Methanothrix, Methanogenium, and Methanoculles are allowed
to live in this ecosystem, methane generation can be performed efficiently. As a consequence, the
liquid to be processed (fermented liquid) transferred to the methane fermentation tank 2 after the
hydrogen fermentation is decomposed into methane and carbon dioxide. Providing a methane
fermentation step after a hydrogen fermentation step as such is quite useful from the viewpoints of
reducing the volume of organic wastes, lowering the environmental load due to organic waste water, etc.
in addition to the fact that methane can be obtained as an energy gas.
[0038] The liquid to be processed (fermented liquid) subjected to the methane fermentation preferably
contains a hop or hop component. The fermented liquid containing a hop or hop component is
preferable since it can effectively suppress activities of microorganisms which may inhibit the methane
fermentation caused by the methane-fermenting microorganism. When a hop or hop component is
added to the liquid to be processed at the time of hydrogen fermentation, the hop or hop component is
brought into the methane fermentation tank 2 together with the liquid to be processed. However, a hop
or hop component may newly be added to the liquid to be processed when the latter is transferred to the
methane fermentation tank 2.
[0039] The biogas generated by the methane fermentation is a mixed gas of methane and carbon
dioxide, and is taken out of the methane fermentation tank 2 by way of a line L4. Though the biogas
can be utilized as an energy gas while still in the mixed gas of methane and carbon dioxide, a film
separator which passes methane there through but not carbon dioxide or an alkali solution absorbing
carbon dioxide or the like can yield methane with a high purity. On the other hand, the fermentation
liquid residue after the methane fermentation is discharged from the methane fermentation tank 2 by
way of a line L5. The fermentation liquid residue is one having sufficiently reduced its volume or
detoxified.
[0040] The present invention is not restricted to the above-mentioned embodiment. For example,
though the above-mentioned embodiment includes a step of determining the maximum tolerable
concentration of the substrate consumable by the hydrogen-fermenting microorganism according to the
correlation with the rate at which the substrate is consumed by the hydrogen-fermenting microorganism,
this step is not always necessary when a hop or hop component is added to the liquid to be processed.
Namely, by adding a hop or hop component into the liquid to be processed containing an organic matter
and deactivating contaminant microorganisms inhibiting hydrogen generation without affecting the
growth or activity of the hydrogen-fermenting microorganism, the present invention can effectively
generate a biogas mainly composed of hydrogen.
[0041] Though the above-mentioned embodiment relates to hydrogen/methane two-stage fermentation
by a continuous operation, the fermenting/cultivating operation of the hydrogen-fermenting
microorganism may be not only a continuous operation but also a batch operation, a semibatch
operation, and the like. The semibatch operation is an operation in which a specific limiting substrate
is supplied to a reactor whereas the aimed product is not taken out until a harvest. This operation is
also known as feeding. The batch operation and semibatch operation are favorable in terms of keeping
the material concentration within an appropriate range, since the substrate concentration in the
fermentation material liquid is easily calculated from the added liquid amount, the substrate
concentration in the added liquid, the culture liquid amount in the fermentation tank, and the substrate
concentration in the liquid. In the continuous operation, the fermentation material liquid is
continuously supplied, while the solution is continuously discharged from within the fermentation tank,
whereby the fermentation material liquid is required to be supplied continuously while taking account
of the flow-in, flow-out, and material consumption by microorganisms. In general, the purpose of
fermentation for collecting an energy gas from a biomass as a material is waste processing of biomasses
such as organic resource wastes and organic waste water or waste water processing, whereby the
continuous operation is rational in terms of apparatus operating efficiency.
Examples
[0042] In the following, the present invention will be explained more specifically with reference to
Examples, which do not restrict the present invention at all.
[0043] [Hydrogen Fermentation Inhibiting Action by Lactic Acid Bacteria]
Example 1
Sludge collected from an anaerobic sludge bed was acclimated in beer brewery waste water (with a pH
of 4, COD of about 15000, glucide concentration (calculated as glucose) of 4000 to 5000 mg/L, a lactic
acid concentration of about 4000 mg/L, and an acetic acid concentration of about 100 mg/L) at 50°C,
and methane-fermenting microorganisms were eliminated therefrom, so as to accumulate an acidgenerating
fermenting microorganism group capable of performing hydrogen fermentation. Using thus
accumulated microorganism group as an inoculum, continuous fermentation fed with beer brewery
waste water as a fermentation material liquid was performed for about 1 month. The continuous
fermentation was carried out under a condition of pH 6.0 to 6.5 at 50°C. Fig. 2 shows the correlation
between the number of days of fermentation and the hydrogen and carbon dioxide concentrations in the
fermentation gas. The organic acid generated at the time of hydrogen fermentation was mainly
composed of about 1000 mg/L of acetic acid, about 2000 mg/L of butyric acid, and about 200 mg/L of
lactic acid. The fermented liquid was collected from a continuous fermentation tank, and was
cultivated at 50°C in a culture medium in which the beer brewery waste water was solidified with agar,
whereby several species of microorganism colonies were detected as dominant species in the culture
liquid. Eight species of microorganisms predominant in the colonies were cultivated in an agar culture
medium for anaerobic fermentation, and base sequences of genes in grown colonies were analyzed,
whereby five out of the eight species were microorganisms of genus Clostridium. The same eight
species of microorganisms were cultivated in an agar culture medium for detecting lactic acid bacteria
(modified GAM culture medium available from Nissui Pharmaceutical Co., Ltd.), but no lactic acid
bacteria were grown.
[0044] Comparative Example 1
After 20 g of glucose (made by Wako Pure Chemical Industries), 3 g of yeast extract (made by DIFCO),
g of peptone (made by DIFCO), 3 g of malt extract (made by DIFCO), and 5 g of NaHCO3 (made by
Wako Pure Chemical Industries) were dissolved in 1 L of tap water, the resulting solution was subjected
to steam sterilization at 121 °C for 15 minutes, whereby a fermentation material liquid was prepared.
The fermentation material liquid was inoculated with a culture liquid which had been obtained by
continuously fermenting the beer brewery waste water for 1 month under the condition of pH 6.0 to 6.5
at 50°C as a fermentation material liquid in Example 1, and batch fermentation was repeated for 24
hours each at 50°C. About 60% of hydrogen and about 40% of carbon dioxide were obtained in the
first batch fermentation, about 50% of hydrogen and about 50% of carbon dioxide were obtained in the
second batch fermentation, and about 35% of hydrogen and about 65% of carbon dioxide were obtained
in the third batch fermentation, whereby the hydrogen production rapidly decreased. The amounts of
generation of acetic acid, butyric acid, and lactic acid were analyzed before the fermentation and at the
respective times when the first, second, and third batch fermentation sessions of the fermentation liquid
material ended, whereby lactic acid was found to increase in the third batch fermentation as shown in
Table 1. The microorganism group in the third batch cultivation was anaerobically cultivated at 50°C
in an agar culture medium comprising glucose, yeast extract, peptone, malt extract, and NaHCOa (the
fermentation liquid material having 15 g of agar added thereto), whereby several species of
microorganism colonies were detected as dominant species. Nine species of microorganisms
predominant in the colonies were cultivated in an agar culture medium for detecting lactic acid bacteria,
and base sequences of genes of grown colonies were analyzed, whereby it was found that, of the nine
species, two species were Lactococcus lactis, two species were Enterococcus faecalis, and one species
was a species related to Enterococcus avium or the like. This indicated that the increase in the lactic
acid bacteria group and the suppression of hydrogen generation occurred in conjunction with each other.
(Table Removed) [0046] Comparing Example 1 and Comparative Example 1 with each other showed that
predominantly growing microorganism groups varied when properties of materials differed from each
other even if the same inoculum was used. These two kinds of material liquids greatly differed from
ASeach
other in terms of glucide concentration. Namely, it was suggested that predominantly growing
microorganism species influenced the glucide concentration of fermented liquids.
[0047] [Hydrogen Fermentation Using Beer Brewery Waste Water]
Example 3
While changing the dilution ratio of a material liquid prepared by adding an easily assimilatable glucide
composed of maltose and starch to beer brewery waste water, hydrogen fermentation by a continuous
operation was performed with the same culture liquid as that of Example 1 as an inoculum.
[0048] First, when the hydrogen fermentation was carried out with a glucide concentration of about
10000 mg/L in the material liquid and a dilution ratio of 1.0/d in the continuous fermentation (days 1 to
7), the glucide concentration in a hydrogen fermentation tank became stable in the vicinity of 800 mg/L,
and the hydrogen fermentation underwent steadily. Thereafter, when the glucide concentration of the
material liquid was set to about 22000 mg/L whereas the dilution ratio was 0.4/d (days 8 to 13), the
hydrogen fermentation still underwent steadily although the glucide concentration in the hydrogen
fermentation tank slightly rose to about 1000 mg/L. When the dilution ratio was set to 1.2/d in the
material liquid having about the same glucide concentration (days 14 to 17), the glucide concentration
in the hydrogen fermentation tank became about 3800 mg/L, and the amount of hydrogen generation
decreased drastically. Namely, when the glucide in the hydrogen fermentation tank was left without
being consumed completely, the amount of hydrogen generation decreased, and the lactic acid
concentration increased. Fig. 3 shows the correlation between the number of days of fermentation and
the hydrogen and carbon dioxide concentrations in the fermentation gas in the above-mentioned
hydrogen fermentation. Table 2 shows the glucide concentration of the material liquid, dilution ratio,
glucide concentration in the hydrogen fermentation tank, and concentrations of organic acids (acetic
acid, butyric acid, and lactic acid) in each period. In Table 2, the glucide concentration and organic
acid concentration in the hydrogen fermentation tank in each period are their central values. This result
showed that the hydrogen fermentation was kept smoothly within the range where the glucide
concentration in the hydrogen fermentation tank did not exceed 4000 mg/L.
[0050] [Hydrogen Fermentation Using Bread Bakery Waste]
Example 4
Using liquids in which bread bakery wastes were suspended in water at various concentrations as a
material, continuous hydrogen fermentation was performed under the condition of pH 6.0 to 6.5 at 50°C
with the same culture liquid as that of Comparative Example 1 as an inoculum.
[0051] First, when the hydrogen fermentation was carried out with a glucide concentration of about
11000 mg/L in the material liquid and a dilution ratio of 0.7/d in the continuous fermentation (days 1 to
6), the glucide concentration in the fermentation tank was 3000 to 4000 mg/L, whereby the hydrogen
fermentation was performed steadily. Next, when a material liquid with a higher bread bakery waste
concentration (glucide concentration of about 35000 mg/L in the material liquid) was supplied (days 7
to 12), the hydrogen generation occurred vigorously until 8 days after the higher concentration material
liquid supply; on day 9 and thereafter, the amount of hydrogen generation decreased, and the lactic acid
concentration rose. In the fermentation period where the hydrogen fermentation was performed
smoothly without decreasing the amount of hydrogen generation (days 1 to 6), the glucide concentration
in the fermented liquid was 3000 to 4000 mg/L. Fig. 4 shows the correlation between the number of
days of fermentation and the hydrogen and carbon dioxide concentrations in the fermentation gas in the
above-mentioned hydrogen fermentation. Table 3 shows the glucide concentration of the material
liquid, dilution ratio, glucide concentration in the hydrogen fermentation tank, and concentrations of
organic acids (acetic acid, butyric acid, and lactic acid) in each period. This elucidated that the
hydrogen fermentation could be maintained smoothly when the material concentration in the supplied
material liquid was held appropriately in the hydrogen fermentation tank.
(Table Removed) [0053] Thus, hydrogen fermentation can be maintained smoothly when a substrate concentration, a
glucide concentration in particular, in a fermentation tank is used as an index, and a material liquid is
supplied such that this index is adjusted so as to fall within a favorable range. Specifically, when the
glucide concentration in the fermented liquid in the fermentation tank is kept at 4000 mg/L or lower in
the case of hydrogen-fermenting microorganisms based on beer brewery waste water and bread bakery
wastes, lactic acid bacteria groups remarkably inhibiting the hydrogen-fermenting microorganisms can
be restrained from predominantly increasing, whereby the hydrogen fermentation can be maintained
smoothly.
[0054] Examples
While controlling the material liquid supply rate in conformity to changes in the glucide concentration
in the fermentation material liquid and keeping the glucide concentration at 3000 mg/L in the hydrogen
fermentation tank, hydrogen fermentation was performed under a condition of pH 6.0 to 6.5 at 50°C.
Specifically, continuous fermentation was initially performed for about 1 month with the same culture
liquid as that of Comparative Example 1 as an inoculum in a material liquid (whose total glucide
concentration was 10710 mg/L to 18390 mg/L) prepared by adding maltose and starch to beer brewery
waste water in order to enhance the microorganism concentration in the fermentation tank. Thereafter,
using material liquids prepared by adding maltose and starch to the beer brewery waste water or
material liquids in which bread bakery wastes were suspended in water at various concentrations,
continuous hydrogen fermentation in which the liquid supply rate was controlled so as to keep a
glucide concentration in the fermentation tank was performed. In the fermentation of about 1
month carried out before performing the continuous fermentation with controlled liquid supply rate, a
value of about 7500 mg/L/day was obtained as the glucide consumption capacity (-dS/dt)c of this
fermentation system. This value was used for determining a control value for material liquid supply
rate in expression (3b). Since the glucide concentration in the fermentation tank was required to be
about 4000 mg/L or less in order to keep hydrogen fermentation as evidenced by Examples 3 and 4, the
control glucide concentration S in the fermentation tank was set to 3000 mg/L. Using these values and
the supplied material liquid glucide concentration, a control index value for the rate at which the
material liquid was supplied to the fermentation tank was calculated by expression (3b). Table 4 shows
control index values for material liquid glucide concentrations. In the hydrogen fermentation with the
controlled material liquid supply rate, continuous fermentation was performed 4 days for a material
liquid, and then was continuously switched to material liquids with different concentrations. Table 4
shows the values at 3 and 4 days after switching the material liquids. The actual dilution ratios in Table
4 are values calculated from actual material liquid supply amounts. The glucide concentration in the
fermentation tank was near an initial target of 3000 mg/L, and the amount of hydrogen generation was
substantially proportional to the amount of glucide consumption. This showed that the hydrogen
fermentation was maintained smoothly.
Example 6
After 20 g of glucose (made by Wako Pure Chemical Industries), 3 g of yeast extract (made by DIFCO),
5 g of peptone (made by DIFCO), 3 g of malt extract (made by DIFCO), and 1 g of hop pellets (Hop
Pellets Type 90 manufactured by Botanix) were dissolved in 1 L of tap water, thus obtained solution
was subjected to steam sterilization at 121°C for 15 minutes, whereby a fermentation material liquid
was prepared. Subsequently, the fermentation material liquid was inoculated with the same culture
liquid as that of Comparative Example 1 as an inoculum, batch fermentation at 50°C was repeated eight
times for 24 hours each. As a result, the fermentation gas composition was composed of about 53% of
hydrogen and about 40% of carbon dioxide in all the batch fermentation sessions, whereby hydrogen
production was maintained. When compositions of organic acids generated at that time were analyzed,
no great changes were seen in eight batch fermentation sessions (Table 5). Though the glucide
concentration in the fermented liquid was high, contaminant microorganism groups did not increase in
the hydrogen fermentation, whereby the hydrogen fermentation was not obstructed. This elucidated
that, unlike Comparative Example 1, the addition of the hop component inhibited activities of
microorganism groups having adverse affects of suppressing the growth or hydrogen generation of
hydrogen-fermenting microorganisms, but did not obstruct activities of the hydrogen-fermenting
microorganisms.
[0058] Example
The fermented liquid of Example 6 was collected, and its bitterness (defined by European Brewery
Convention, Analytica-EBC 4th ed., p. El37,1987) was measured. The bitterness was about 13. This
elucidated that the hop component inhibited activities of microorganism groups suppressing the growth
or hydrogen generation of hydrogen-fermenting microorganisms at a bitterness near 13, but did not
obstruct the activities of the hydrogen-fermenting microorganisms.
[0059] Example 8
A hop component was added to the culture system of Example 4 having drastically reduced the amount
of hydrogen generation, so as to restore its hydrogen generation.
[0060] Specifically, a material liquid having reduced the glucide concentration of the supply liquid
was initially supplied to the culture system of Example 4 from day 13, and an operation was performed
for 3 days (days 13 to 15). However, this operation did not restore the hydrogen fermentation, whereby
the amount of hydrogen gas generation did not recover. Therefore, on day 16, hop pellets (Hop Pellets
Type 90 manufactured by Botanix) were added to the fermentation tank and the supply liquid by 1 g per
1 L of the fermented liquid. The hydrogen production exhibited a tendency to recover on day 17 and
thereafter, and was restored to the level at the time of starting the higher concentration material liquid
supply on day 20 (Fig. 6). On day 19 and thereafter, the generated organic acid composition was
/
restored to the level at the time of starting the higher concentration material liquid supply (Table 6).
This elucidated that a hop as pellets at a concentration of 1 g per 1 L of fermented liquid inhibited
activities of unfavorable microorganism groups suppressing the growth or hydrogen generation of
hydrogen-fermenting microorganisms, but did not obstruct activities of the hydrogen-fermenting
microorganisms.
[0062] Example 9
For various hop components, effects of smoothly maintaining hydrogen fermentation were investigated.
[0063] After 35 g of glucose (special grade reagent made by Wako Pure Chemical Industries), 3 g of
yeast extract (made by DIFCO), 5 g of peptone (made by DIFCO), 3 g of malt extract (made by
DIFCO), and at least one species of hop components shown in Table 7 were dissolved in 1 L of tap
water, the resulting solution was subjected to steam sterilization at 121°C for 15 minutes, whereby
fermentation material liquids A to F were prepared. On the other hand, fermentation material liquid G
was made in the same manner except that no hop component was added.
[0065] Next, each of the fermentation material liquids A to G was inoculated with the same culture
liquid as that of Example 1 as an inoculum, and batch fermentation was repeated four times for 24 hours
each. Though the hydrogen production decreased while lactic acid increased in the sample to which no
hop component was added, about 400 ml of hydrogen and about 350 ml of carbon dioxide were attained
in all the batch fermentation sessions in the samples to which hop components were added without
lowering the hydrogen production (Fig. 7). Lactic acid did not increase in any of the samples to which
hop components were added (Table 8). This elucidated that, except for the beta acid exhibiting no
bitterness, an amount of addition of hop components by a bitterness of 10 or greater inhibited activities
of microorganism groups having adverse affects of suppressing the growth or hydrogen generation of
hydrogen-fermenting microorganisms, but did not obstruct activities of the hydrogen-fermenting
microorganisms. At an amount of addition of 10 jiL per 1 L of fermented liquid, the beta acid was
found to inhibit activities of microorganism groups having adverse affects of suppressing the growth or
hydrogen generation of hydrogen-fermenting microorganisms, but did not obstruct activities of the
hydrogen-fermenting microorganisms
[0067] Example 10
It was also found that subjecting a fermented liquid after hydrogen fermentation of a biomass material
having a hop or hop component added thereto or contained therein to methane fermentation caused by a
methane-fermenting microorganism smoothly maintained the methane fermentation. This will be
shown.
[0068] The hydrogen fermentation effluent in which the hydrogen fermentation material containing
hop pellets was supplied to the fermentation system of Example 1 in which the hydrogen fermentation
was contaminated with microorganisms inhibiting the hydrogen fermentation and thus lowered the
hydrogen production, so as to restore the hydrogen fermentation, was subjected to methane fermentation
by methane-fermenting microorganisms, and it was tested whether the methane fermentation was
maintained smoothly or not.
[0069] First, the fermentation effluent in which hydrogen fermentation progressed normally without
no hop component added thereto in Example 4 was subjected to methane fermentation under a
condition of pH 7.0 to 7.5 at 37°C. Namely, using the effluents on days 5 and 6 of hydrogen
fermentation in Example 4 as a hydrogen fermentation effluent (methane fermentation material liquid),
the methane fermentation was performed. When supplying the material liquid to the methane
fermentation, the dilution ratio was 0.43/d. Fig. 8 shows thus obtained results (days 5' and 6' in Fig.
8).
[0070] Thereafter, the hydrogen fermentation effluent after performing the hydrogen fermentation
using the fermentation material liquid A of Example 8 (having hop pellets added thereto) was subjected
to methane fermentation. Namely, using the effluents on days 16 to 21 of hydrogen fermentation in
Example 8 as a hydrogen fermentation effluent (i.e., methane fermentation material liquid), the methane
fermentation was performed. When supplying the material liquid to the methane fermentation, the
dilution ratio was 0.40/d. Fig. 8 shows thus obtained results (days 16' and 21' in Fig. 8).
[0071] As shown in Fig. 8, the methane fermentation caused by the methane-fermenting
microorganism exhibited no abnormality in the amount of methane generation even when using the
effluents obtained after performing the hydrogen fermentation by the hydrogen fermentation materials
containing hop pellets. This has elucidated that methane fermentation caused by methane-fermenting
microorganisms is smoothly maintained also when fermented liquid obtained after performing hydrogen
fermentation with a biomass material having a hop or hop component added thereto or contained therein
is subjected to the methane fermentation.




WE CLAIM:-
1. A method for producing a biogas, comprising the step of:
generating a biogas mainly composed of hydrogen by performing hydrogen fermentation while adding a hop or hop component to a liquid to be processed containing glucide so as to inactivate a contaminant microorganism inhibiting hydrogen generation without affecting a growth or activity of a hydrogen-fermenting microorganism,
wherein the hydrogen fermentation is performed under a condition with a pH 6.0 to 7.5 and a temperature of 20°C to 70°C,
wherein the hop or hop component are selected from the group consisting of chemically modified hop such as hop strobiles, hop pellets, hop extracts, isomerized hop pellets, tetrahydroisofumulones; hop α-acid; and hop ß-acid.

Documents:

5202-DELNP-2006-Abstract-(01-11-2011).pdf

5202-delnp-2006-abstract.pdf

5202-delnp-2006-assignments.pdf

5202-DELNP-2006-Claims-(01-11-2011).pdf

5202-delnp-2006-claims.pdf

5202-DELNP-2006-Correspondence Others-(01-11-2011).pdf

5202-DELNP-2006-Correspondence Others-(17-08-2011).pdf

5202-DELNP-2006-Correspondence Others-(25-10-2011).pdf

5202-DELNP-2006-Correspondence-Others-(21-01-2011).pdf

5202-delnp-2006-correspondence-others-1.pdf

5202-delnp-2006-correspondence-others.pdf

5202-delnp-2006-description (complete).pdf

5202-DELNP-2006-Drawigns-(17-08-2011).pdf

5202-DELNP-2006-Drawings-(01-11-2011).pdf

5202-delnp-2006-drawings.pdf

5202-DELNP-2006-Form-1-(01-11-2011).pdf

5202-delnp-2006-form-1.pdf

5202-delnp-2006-form-18.pdf

5202-DELNP-2006-Form-2-(01-11-2011).pdf

5202-delnp-2006-form-2.pdf

5202-DELNP-2006-Form-3-(01-11-2011).pdf

5202-DELNP-2006-Form-3-(25-10-2011).pdf

5202-delnp-2006-form-3.pdf

5202-delnp-2006-form-5.pdf

5202-DELNP-2006-GPA-(01-11-2011).pdf

5202-DELNP-2006-GPA-(21-01-2011).pdf

5202-delnp-2006-pct-210.pdf

5202-delnp-2006-pct-237.pdf

5202-delnp-2006-pct-304.pdf

5202-delnp-2006-pct-308.pdf

5202-delnp-2006-pct-338.pdf

5202-delnp-2006-pct-373.pdf


Patent Number 251269
Indian Patent Application Number 5202/DELNP/2006
PG Journal Number 10/2012
Publication Date 09-Mar-2012
Grant Date 05-Mar-2012
Date of Filing 11-Sep-2006
Name of Patentee SAPPORO BREWERIES LIMITED
Applicant Address 20-1,EBISU 4-CHOME, SHIBUYA-KU, TOKYO 150-8522, JAPAN.
Inventors:
# Inventor's Name Inventor's Address
1 MITANI YUTAKA C/O SAPPORO BREWERIES LIMITED,FRONTIER LABORATORIES OF VALUE CREATION, 10, OKATOHME, YAIZU-SHI, SHIZUOKA 425-0013, JAPAN.
2 NISHIO NAOMICHI 3-1, KAGAMIYAMA 1-CHOME, HIGASHIHIROSHIMA-SHI, HIROSHIMA 739-8530, JAPAN
PCT International Classification Number C02F 11/04
PCT International Application Number PCT/JP2005/002226
PCT International Filing date 2005-02-15
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 P2004-038882 2004-02-16 Japan