WO2009076947A2

WO2009076947A2 - Method for producing biogas

Info

Publication number: WO2009076947A2
Application number: PCT/DE2008/075013
Authority: WO
Inventors: Monika Reuter; Vera Duchow; Daniel Vater
Original assignee: Schmack Biogas Ag
Priority date: 2007-12-19
Filing date: 2008-12-08
Publication date: 2009-06-25
Also published as: WO2009076947A3; WO2009076948A2; WO2009076948A3

Abstract

The invention relates to a method for producing biogas in a fermentation reactor. The method comprises the steps of determining at least one first target value range associated with a first characteristic parameter of the fermentation, wherein the first target value range defines a first value range suitable for maintaining the fermentation; determining at least one second target value range associated with a second characteristic parameter of the fermentation, wherein the second target value range defines a second value range suitable for maintaining the fermentation; determining at least one measurement value of the first characteristic parameter during the fermentation process; comparing the measured value of the first characteristic parameter to at least one first target value range associated with said first parameter; comparing the measured value of the second characteristic parameter to at least one second target value range associated with said second parameter, and addition of at least one type of micro-organisms to the fermentation substrate if the measured value of the first characteristic parameter has a defined relation to the first target value range associated with said first parameters, and if the measured value of the second characteristic parameter has a defined relation to the second target value range associated with said second parameter.

Description

Process for the production of biogas

Technical area

The invention relates to a method for producing biogas from biomass using microorganisms.

State of the art

Biogas plants produce methane through a microbial decomposition process of organic substances. The biogas is produced in a multi-stage process of fermentation or digestion by the activity of anaerobic microorganisms, i. in the absence of air.

The organic material used as fermentation substrate has a high molecular structure from a chemical point of view, which is degraded in the individual process steps of a biogas plant by metabolic activity of microorganisms to low molecular weight building blocks. However, the populations of microorganisms which are active in the fermentation of the organic fermentation substrate have hitherto been insufficiently characterized.

According to the current state of knowledge, it is possible to distinguish between four consecutive, but also parallel and interlocking biochemical single processes which enable the degradation of organic fermentation substrates to the end products methane and carbon dioxide: hydrolysis, acidogenesis, acetogenesis and methanogenesis.

In hydrolysis, high molecular weight, often particulate organic compounds are formed by exoenzymes (eg cellulases, amylases, proteases, lipases) fermentative bacteria converted into soluble fission products. For example, fats are broken down into fatty acids, carbohydrates, such as polysaccharides, into oligo- and monosaccharides and proteins into oligopeptides or amino acids. The gaseous products formed besides consist predominantly of carbon dioxide.

Optional and obligate anaerobic bacteria, often identical to the hydrolyzing bacteria, metabolize in acidification the hydrolysis products (eg mono-, disaccharides, di-, oligopeptides, amino acids, glycerol, long-chain fatty acids) intracellularly to short chain fatty or carboxylic acids such as butter -, propionic and acetic acid, to short-chain alcohols such as ethanol and the gaseous products hydrogen and carbon dioxide.

In the subsequent acetogenesis, the short-chain fatty acids and carboxylic acids formed in acidogenesis and the short-chain alcohols are taken up by acetogenic bacteria and excreted again as acetic acid after β-oxidation. By-products of acetogenesis are CO ₂ and molecular hydrogen (H _2).

The products of acetogenesis such as acetic acid but also other substrates such as methanol and formate are converted by methane-forming organisms in the obligate anaerobic methanogenesis to methane and CO ₂ . The resulting here CO ₂ and also during the other process steps such as hydrolysis, CO ₂ formed in turn can be converted by microorganisms with the incurred H ₂ to methane.

If the fermentation of the fermentation substrate is disturbed, the fermenter may crash, ie, the production of methane and carbon dioxide is stopped. The reasons for such a disorder are still insufficiently researched. After a fall of the fermentation process in the fermenter usually several days or weeks are needed to bring the fermentation process back into a stable range. This often requires exposure of the substrate feed to the fermenter as well as a more or less systematic variation of different process parameters, such as pH, to get the fermentation process going again.

The time taken to stabilize the fermentation after the fermenter crashes presents a major problem in biogas production. There is therefore still a need for methods of producing biogas which do not have the disadvantages of the prior art.

Presentation of the invention

The object of the invention is to provide a method for the production of biogas, which has a comparison with the prior art increased stability of the fermentation process.

This object is achieved by the method for producing biogas according to claim 1. Further advantageous details, aspects and embodiments of the present invention will become apparent from the dependent claims, the description and the examples.

The present invention provides a method for producing biogas in a fermentation reactor. The method comprises the steps

Establishing at least one first setpoint range associated with a first characteristic parameter of the fermentation, the first setpoint range defining a first value range suitable for maintaining the fermentation,

Establishing at least one second desired value range assigned to a second characteristic parameter of the fermentation, the second setpoint range defining a second value range suitable for maintaining the fermentation, - A -

Determination of at least one measured value of the first characteristic parameter during the fermentation process,

Determination of at least one measured value of the second characteristic parameter during the fermentation process,

Comparison of the measured value of the first characteristic parameter with at least one first setpoint value range assigned to this first parameter,

Comparison of the measured value of the second characteristic parameter with at least one second setpoint value range assigned to this second parameter,

Adding at least one type of microorganism to the fermentation substrate if the measured value of the first characteristic parameter has a fixed relation to the first setpoint range associated with that first parameter and if the measured value of the second characteristic parameter is a fixed relation to the second setpoint range associated with that second parameter having.

In the context of the present invention, a "characteristic parameter of the fermentation" is understood as meaning any parameter which can provide information about the quality of a fermentation process proceeding for the production of biogas Such characteristic parameters are not only the amount of biogas produced and the methane content of the biogas produced but also, for example, the hydrogen content of the biogas produced, the pH of the fermentation substrate, the redox potential of the fermentation substrate, the carboxylic acid content of the fermentation substrate, the proportions of various carboxylic acids in the fermentation substrate, the hydrogen content of the fermentation substrate, the proportion of dry matter in the fermentation substrate, the proportion of the organic dry matter on the fermentation substrate, the viscosity of the fermentation substrate and the volume loading of the fermentation reactor. The parameters mentioned have in common that their real measured values allow statements about the fermentation process for which the measured values were determined. For the parameter "quantity of produced biogas", the relation to the quality of the fermentation process is given by the fact that the generated biogas represents the end product of the fermentation.At this point it should be pointed out that the determination of the parameter "amount of produced biogas" is not only can be done by a direct measurement of the amount of biogas produced, but in practice also on the basis of the fermenter downstream energy conversion unit, such as a combined heat and power plant, generated amount of energy [kWh].

Another example is the pH of the fermentation substrate, which should be in a range between about pH 5 and pH 8 to ensure a satisfactory fermentation process. By determining characteristic parameters and comparing the measured values with the setpoint ranges assigned to these parameters, a statement can be made as to whether the corresponding fermentation process is stable and proceeds with the desired yield.

Surprisingly, it has been found on the basis of experimental investigations that the deviation of a single characteristic parameter from its predetermined target value range does not allow a sufficiently reliable statement about the quality of the fermentation process that is taking place. Thus, for example, despite a portion of the dry substance lying outside the normal range, a stable fermentation with a high yield of biogas can take place on the fermentation substrate. Similarly, if the fermenter space is too small, there is no reliable information about the fermentation process taking place in the fermenter. Only the evaluation of at least two characteristic parameters allows a reliable statement about the fermentation process.

In addition, it was found that, in addition to the deviation of the actual measured variables of the characteristic parameters from the predefined setpoint ranges, a deviation of the first or second derivative of the measured values according to the time from corresponding setpoint ranges also provides information about allows the fermentation process. Thus, for example, a rapid change in the carboxylic acid concentration can have a very negative effect on the stability of the fermentation process, even though the actually determined measured value is still within the predefined setpoint range for this measured value.

It has also been surprisingly found that the addition of at least one type of microorganism to the fermentation substrate results in stabilization and even improvement of the fermentation process. The addition according to the invention of the microorganisms in response to the deviation of characteristic parameters from predetermined desired value ranges makes possible an effective and rapid intervention in fermentation processes in which there is the danger of a fall of the fermenter. By adding the microorganisms, the fermentation process is stabilized quickly, whereby a fall of the fermenter can be avoided in most cases.

In the context of the present invention, the term "type of microorganisms" is understood to mean the corresponding basic category of biological taxonomy.Species of microorganisms are identified and distinguished on the basis of their DNA sequences, not just microorganisms having a specific DNA According to general agreement, this degree of genetic variance is 3%, so a microorganism of any kind actually and also in the context of the present invention includes all microorganisms with the known DNA sequence of the latter And with a by DNA exchanges of nucleotides by up to 3%.

According to a preferred embodiment, the characteristic parameters of the fermentation are selected from the group consisting of amount of biogas produced, methane content of the generated biogas, hydrogen content of the biogas produced, pH of the fermentation substrate, redox potential of the fermentation substrate, carboxylic acid content of the fermentation substrate, proportions of various carboxylic acids in Fermentation substrate, hydrogen content of the fermentation substrate, proportion of dry substance am Fermentation substrate, proportion of the organic dry substance in the fermentation substrate, viscosity of the fermentation substrate and volume loading of the fermentation reactor.

Fermentation for the purposes of the present invention includes both anaerobic and aerobic material conversions by the action of microorganisms that lead to the production of biogas. This explanation of the term "fermentation" is under the keyword "fermentation in Römpp Chemistry Lexicon in the 9th, extended edition, published by Georg Thieme Verlag on page 1306, indicated, to which reference is hereby incorporated by reference.

The carboxylic acids of the fermentation substrate are, for example, volatile fatty acids such as acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid or formic acid, which are formed during biogas production.

The mentioned characteristic parameters provide information as to whether the fermentation process is in a stable state of equilibrium or whether the fermenter is in danger of collapse. For all characteristic parameters, setpoint ranges can be determined on the basis of experimental data which provide information as to whether the fermentation of the fermentation substrate is in a state suitable for producing biogas. In the case of a deviation of the values of at least two characteristic parameters measured during the fermentation process from the setpoint value assigned to the respective parameter, the fermentation process does not proceed in an ideal state. In case of a strong deviation of the measured values from the respective setpoint range, the fermenter may possibly crash. The setpoint ranges for the individual characteristic parameters are therefore usually determined experimentally for a particular set of external conditions under which fermentation takes place.

For example, an increase in the carboxylic acid concentration in the fermentation substrate is often associated with a decline in biogas production. A deviation of, for example, 200 mg / l from the setpoint range determined experimentally for a stable fermentation gives an indication of an increasing instability of the Fermentation process. Furthermore, a deviation of the pH by, for example, 0.5 from a range suitable for biogas production, which is usually between about pH 5 and pH 8, is associated with a change in the amount and composition of the biogas produced.

In addition, the proportion of methane in the biogas produced may vary depending on the fermentation substrate. For example, the methane content in stable fermentations of cellulose-containing substrates about 40 to 75 vol.% And in the stable fermentation of greasy substrates about 50 to 75 vol.%. A deviation from these ranges, combined with a deviation of another characteristic parameter, for example the pH of the fermentation substrate, may thus also indicate that the fermentation process is taking place outside a range suitable for producing biogas.

Another well-suited indicator is the proportion of hydrogen in the biogas produced. With stable fermentations, the proportion of hydrogen in the biogas produced is about 50 ppm to several 1000 ppm. The proportion of dry matter in the fermenter content may be about 0 to 20% by volume.

According to a preferred embodiment, the types of microorganisms added are selected from the group consisting of hydrolytically active fermentative microorganisms, acidogenic fermentative microorganisms, acetogenic fermentative microorganisms and methanogenic fermentative microorganisms. This makes it possible to add at least one microorganism having a specific metabolic activity, which is needed for at least one of the already mentioned four stages of fermentation during the production of biogas.

In order to ensure targeted influencing of the fermentation process, preferably at least two types of microorganisms are added, more preferably at least three types of microorganisms are added, and more preferably at least four types of microorganisms are added to the fermentation substrate. For example, if at least two types of two different fermentative microorganisms are added to the fermentation substrate, for example, a fermentative microorganism having cellulose-hydrolyzing activity and at least one other fermentative microorganism having eg protein hydrolyzing activity in a fermentation reactor for simultaneous hydrolysis of two different fermentation substrates, such as cellulose and protein-containing fermentation substrates are used. Alternatively, it is conceivable to use a fermentative microorganism having, for example, hydrolyzing activity and at least one further fermentative, for example methanogenic, microorganism.

The fermentation process can be particularly specifically influenced if the added types of microorganisms are selected from at least two members of the group consisting of hydrolytically active fermentative microorganisms, acidogenic fermentative microorganisms, acetogenic fermentative microorganisms and methanogenic fermentative microorganisms.

Preferred are embodiments according to which the added types of microorganisms are selected from at least three members of the group consisting of hydrolytically active fermentative microorganisms, acidogenic fermentative microorganisms, acetogenic fermentative microorganisms and methanogenic fermentative microorganisms.

According to a particularly preferred embodiment of the present invention, at least one kind of a hydrolytically active fermentative microorganism, at least one kind of an acidogenic fermentative microorganism, at least one kind of an acetogenic fermentative microorganism and at least one kind of a methanogenic fermentative microorganism are added. This makes it possible, for example, to add at least one type of fermentative microorganism to the fermentation substrate during the fermentation for each stage of the complex biogas production process, by virtue of its specific hydrolytic, can particularly well support acidogenic, acetogenic or methanogenic metabolic activity.

The addition of a hydrolytically active fermentative microorganism to the fermentation substrate can influence the hydrolysis of the biopolymer constituents present in the fermentation substrate into monomers or into oligomers and other soluble degradation products. In the hydrolysis step, fats are also added to fatty acids, carbohydrates, e.g. Polysaccharides to oligo- and monosaccharides and proteins to oligopeptides or hydrolyzed to amino acids. Particular preference is therefore given to at least one hydrolytically active fermentative microorganism of a genus selected from the group consisting of Anaerophaga, Lachnospira, Paenibacillus, Pseudomonas, Leptothrix, Burkholderia, Ralstonia, Bradyrhizobium, Arcobacter, Fibrobacter, Streptococcus, Planomicrobium, Turicibacter, Ruminococcus, Deinococcus, Peptostreptococcus, Vagococcus, Proteus, Clostridium, Bacillus, Bacteroides, Cytophaga and Sporocytophaga added.

Due to the addition of at least one type of hydrolytically active, fermentative microorganism, the first step of biogas production is to control the hydrolysis particularly well. Depending on the biopolymeric constituents present in the fermentation substrate, a hydrolytically active fermentative microorganism can be added which can hydrolyse the biopolymeric constituents present or even predominant in the fermentation substrate.

Thus, the fermentation substrate to be fermented, for example, consist to a large extent of plants, crops and energy plants targeted for biogas production, so-called renewable raw materials, previously unusable plant components, silage, biowaste and other cellulosic, hemicellulose, starch and carbohydrate-containing substrates , In this case, at least one kind of cellulose, starch or sucrose hydrolyzing fermentative microorganism can be added which can hydrolyze the cellulose, hemicellulose, starch or carbohydrates present in these substrates. Furthermore, the substrates may be fresh, dried or preserved, for example, used as ensilage. Here, silage, and especially maize silage, whole plant silage, or grass silage are preferred as a substrate, since silage is a particularly high-quality energy source and can be achieved by the use of silage high biogas yield.

In the fermentation of animal residues, such as slaughterhouse slaughter or other animal components, one type of protein or lipid hydrolyzing fermentative microorganism may preferably be added to the fermentation substrate which may hydrolyze the protein and lipid components of the fermentation substrate. For the fermentation of a substrate having various components of different origin, such as animal and vegetable residues containing, for example, carbohydrates and lipids and e.g. Food residues, manure or sewage sludge, is the use of more than one type of hydrolytically active microorganism, e.g. a sucrose, a starch and a lipid-hydrolyzing microorganism conceivable. Thus, also fermentation substrates containing various components of different origin can be fermented more efficiently by the addition of at least one kind of a specific hydrolytically active fermentative microorganism.

In addition, the fermentation substrate may also contain solid components which may be at least partially liquified by the addition of one kind of hydrolytically active fermentative microorganism. Due to the liquefaction of the fermentation substrate due to the addition of a hydrolytically active, fermentative microorganism, thickening of the fermenter material can be prevented and specifically counteracted, and further liquid introduction into the fermentation substrate in the form of water or manure during the fermentation can be avoided. Thus, there is another advantage in conserving the resource freshwater. It is also advantageous to obtain the stirring and pumpability of the material thus obtained, since the dry matter content does not increase any further.

The addition of a hydrolytically active, fermentative microorganism to the fermentation substrate is preferably carried out with a deviation of the characteristic Excessive dry matter content may be detrimental to the formation of methane If, for example, this is determined by the deviation of the two parameters from their target value ranges, the addition may be preferred of a hydrolytically active, fermentative microorganism destabilizing the

Be counteracted fermentation process.

By adding an acidogenic, fermentative microorganism to the fermentation substrate, the monomers formed in the hydrolysis of the biopolymers, oligomers or other soluble degradation products in short-chain fatty and carboxylic acids, such as. As butter, propionic and acetic acid and in short-chain alcohols, such as. As ethanol, improved implemented. Particular preference is therefore given to at least one acidogenic fermentative microorganism of a genus selected from the group consisting of Flavobacterium, Delftia, Selenomonas, Butyrivibrio, Schwarztia, Aminomonas, Paenibacillus, Anaeorophaga, Halothermothrix, Bacillus, Eubacterium, Clostridium, Acetanaerobacterium, Sedimentibacter, Corynebacterium, Bifidobacterium, Microbacterium , Williamsia and Cryptobacterium added.

In order to be able to better control the acidogenesis, at least one type of acidogenic, fermentative microorganism of the mentioned genera may also be added to the fermentation substrate during the fermentation. A fermentative microorganism having an acidogenic metabolic activity, the products of hydrolysis such as fatty acids, oligo- and / or Monosaccaride, oligopeptides and / or amino acids to short-chain fatty and carboxylic acids, as well as short-chain alcohols implement, so that the addition of a Such acidogenic, fermentative microorganism to the fermentation substrate can lead to improved Acidogenese.

The addition of an acidogenic, fermentative microorganism to the fermentation substrate is preferably carried out at a deviation of the characteristic parameter "amount of biogas produced" as in the case of too small a number of acidogenic microorganisms too few precursors for metabolism by acetogenic and methanogenic microorganisms are formed. This can lead to a reduction in biogas production. As further characteristic parameters for the addition of an acidogenic microorganism to the fermentation substrate, the content of carboxylic acids and the proportions of various carboxylic acids in the fermentation substrate are preferably used. If deviations from at least two of the mentioned parameters from the associated desired value ranges are ascertained, destabilization of the fermentation process can be counteracted by the addition of an acidogenic, fermentative microorganism.

Furthermore, by adding an acetogenic fermentative microorganism to the fermentation substrate, the conversion of the short-chain fatty and carboxylic acids and short-chain alcohols formed during the acidogenesis to acetic acid or acetates and to CO _{2 can be} improved. Particular preference is therefore given to at least one acetogenic fermentative microorganism of a genus selected from the group consisting of Acetobacterium, Synthrobobacter, Synthrophococcus, Pelobacter, Acetivibrio, Sporobacter, Lactobacillus, Desulfomonas, Methylobacterium, Caulobacter, Acetanaerobacterium, Synthrophobotulus, Desulfonosporus, Desulfotomaculum, Gelria,

Thermoterrabacterium, Syntrophomonas, Syntrophothermus, Moorella, Aminomonas and Anaerobaculum.

A further improvement in the fermentation of the fermentation substrate can thus be achieved if at least one type of acetogenic microorganism is added during the fermentation. Acetogenic microorganisms help to promote acetogenesis during the production of biogas, as they contribute to an improved conversion of the products of acidogenesis, the short-chain fatty and carboxylic acids, and the short-chain alcohols to acetic acid, CO ₂ and H ₂ .

The addition of an acetogenic microorganism to the fermentation substrate is preferably carried out with a deviation of the characteristic parameters "carboxylic acid content of the fermentation substrate" and "proportions of various carboxylic acids in the fermentation substrate" of the corresponding predetermined target value ranges. For example, too high a carboxylic acid content can adversely affect the formation of methane. In addition, a deviation of the characteristic parameter "amount of generated biogas" is preferably taken into account, since in the case of too small a number of acetogenic microorganisms, too few precursors are formed for metabolization by methanogenic microorganisms If at least two of the stated parameters are determined by the associated setpoint ranges, destabilization of the fermentation process can be counteracted by the addition of an acetogenic microorganism.

Finally, the fourth step of biogas production, methanogenesis, can be influenced by adding a methanogenic microorganism. If this is an acetoclastic methanogen, it is able to form methane and CO ₂ from the acetate formed in acetogenesis or from acetic acid. Other methanogenic microorganisms can produce methane by reacting carbon dioxide and hydrogen. Particular preference is therefore given to adding at least one methanogenic fermentative microorganism of a genus selected from the group consisting of methanocorpusculum, methanoculleus, methanogenium, methanomethylovoran, methanobacterium, methanobacter bacterium, methanococcus, methanomicrobium, methanosaeta, methanospirillum, methanothermobacter and methanothermococcus.

The fourth step of biogas production, methanogenesis can be better controlled by the addition of one kind of methanogenic fermentative microorganism. The addition of a acetoclastischen, methane-forming micro-organism is for example conceivable which can convert the acetic acid formed during the acetogenesis into methane and CO _2. It is also possible to add other fermentative fermentative microorganisms during the fermentation to the fermentation substrate, which convert the CO ₂ and H ₂ formed during the acetogenesis to methane and CO ₂ . The addition of methanogenic, fermentative microorganisms enables improved conversion of, for example, acetic acid and can lead to an increased methanogenesis rate and thus to an increased yield of methane-containing biogas. Thus, a deterioration of the methane content in the resulting biogas can be counteracted by the accumulation of acetogenic intermediates.

The addition of a methanogenic, fermentative microorganism to the fermentation substrate is preferably carried out with a deviation of the characteristic parameters "amount of biogas produced" and "methane content of the biogas produced" from the corresponding predetermined setpoint range. In addition, the characteristic parameter "hydrogen content of the fermentation substrate" can also be taken into account If a deviation of the two mentioned parameters from their nominal value ranges is determined, then by the addition of a methanogenic microorganism it is possible to destabilize the

Be counteracted fermentation process. In the case of a deviation of the parameter "hydrogen content of the fermentation substrate" is preferably carried out the addition of hydrogenotrophic methanogenic microorganisms.

Preferably, the individual types of microorganisms in the form of cultures of microorganisms are added to the fermentation substrate, the cultures of microorganisms each consisting predominantly of one type of microorganism. In order to influence the individual steps of the fermentation process, it is advantageous to selectively add to the fermentation substrate a suitable amount of one or more types of microorganisms. Of course, it is possible to use mixed cultures of microorganisms, which may be natural or artificially produced mixed cultures.

The addition of the cultures of microorganisms can be carried out in the form of a culture suspension, in the form of dry, freeze-dried or moist cell pellets or in the form of spore suspensions, spore preparations or dry, freeze-dried or moist spore pellets.

The determination of the proportions of different types of microorganisms in such mixed cultures is not a problem for the expert. Thus, for example, using fluorescence-labeled oligosensors specifically the proportion of individual species of microorganisms can be identified in a mixture. As already mentioned, the individual types of microorganisms are preferred in the form of cultures of microorganisms added to the fermentation substrate, the cultures of microorganisms consisting predominantly of one type of microorganism. If, in addition, the total number of microorganisms is determined, then the percentage of a certain type of microorganism in the culture can be stated as a percentage. The predominant species of microorganism present in a mixed culture is the type of microorganism with the highest percentage of mixed culture.

Basically, the targeted influencing of the fermentation process is the better possible, the greater the proportion of the desired type of microorganisms in the mixed substrate added to the fermentation substrate. Therefore, preference is given

Embodiments according to which the culture of microorganisms added to the fermentation substrate at least predominantly present type of microorganisms

25% of the total number of microorganisms present in the culture, more preferably the type of microorganisms predominantly present in the culture of microorganisms makes up at least 50% of the total number of microorganisms

Culture existing microorganisms.

Moreover, embodiments are preferred according to which the type of microorganisms predominantly present in the culture of microorganisms constitutes at least 66%, more preferably at least 75%, and most preferably at least 90% of the total number of microorganisms present in the culture.

Further preferred embodiments are those in which in the culture of microorganisms of the predominantly present type of microorganisms makes up at least 95% of the total number of microorganisms present in the culture, and more preferably at least one pure culture of microorganisms is added to the fermentation substrate.

Thus, at least one type of microorganism can be added to the fermentation substrate, which, due to its specific metabolic processes, can support at least one stage in the complex biogas production process. In this way, the production of biogas can be better controlled than was previously possible. The addition of microorganisms in response to the deviation characteristic parameter of predetermined setpoint ranges allows the stabilization of the fermentation process and often prevents a fall of the fermenter.

By the term "pure culture of a microorganism" is meant the progeny of a single cell isolated by a multi-step process from a mixture of different microorganisms The multi-step mechanism of isolation begins with the separation of a single cell from a cell population and requires that as well the colony remaining in the cell through growth and cell division is separated from other single cells or colonies by carefully separating a colony, re-suspending it in liquid, and repeating it repeatedly to selectively recover pure cultures of microorganisms.

However, the isolation of a pure culture can also be carried out in liquid nutrient media, provided that the desired organism outnumbered in the starting material. By serial dilution of the suspension in the nutrient solution, it can finally be achieved that only one cell remains in the last dilution stage. This cell then represents the basis for a pure culture. This explanation of the term "pure culture" and possible methods for generating a pure culture under the keyword "pure culture" in the work "General Microbiology" by Hans G. Schlegel in the 7th revised edition of 1992, published by Georg Thieme Verlag on page 205, to which reference is hereby incorporated by reference.

The pure culture obtained in this way is also characterized biochemically by specific metabolic processes and activities, as well as by special growth conditions. Due to the specific metabolic processes and activities, the addition of a pure culture of a fermentative microorganism can especially contribute to an improved control of the complex biogas production process.

According to another preferred embodiment of the present invention, the microorganisms are formed as part of at least one immobilized culture of microorganisms added. Since the amount of microorganisms isolated from their natural occurrence is insufficient for the addition of the microorganisms, it is usually propagated in the form of a culture. In practice, it has been found that the addition of the microorganisms to the fermentation substrate of a fermenter is most easily carried out in the form of an immobilized culture of microorganisms.

In accordance with a further preferred embodiment of the present invention, the determination of at least one third desired value range assigned to a third characteristic parameter of the fermentation additionally takes place, the third desired value range defining a third value range suitable for maintaining the fermentation. Accordingly, a determination is made of at least one measured value of the third characteristic parameter during the fermentation process and a comparison of the measured value of the third characteristic parameter with at least one third setpoint range assigned to this third parameter. The addition of at least one type of microorganism to the fermentation substrate is carried out in the event that the measured value of the first characteristic parameter has a fixed relation to the first setpoint range associated with this first parameter, the measured value of the second characteristic parameter a fixed relation to that of the second Parameter has associated second setpoint range and the measured value of the third characteristic parameter has a fixed relation to the said third parameter associated third setpoint range.

In accordance with a further preferred embodiment of the present invention, the setting of at least one fourth desired value range assigned to a fourth characteristic parameter of the fermentation additionally takes place, wherein the fourth desired value range defines a fourth value range suitable for maintaining the fermentation. Accordingly, a determination of at least one measured value of the fourth characteristic parameter takes place during the fermentation process and a comparison of the measured value of the fourth characteristic parameter with at least one fourth setpoint range associated with this fourth parameter. The addition of at least one type of microorganisms to the fermentation substrate takes place in the event that the measured value of the first characteristic parameter has a fixed relation to the first setpoint range associated with this first parameter, the measured value of the second characteristic parameter is a fixed relation to the second parameter associated therewith second setpoint range, the measured value of the third characteristic parameter has a fixed relation to the third setpoint range associated with this third parameter, and the measured value of the fourth characteristic parameter has a fixed relation to the fourth setpoint range associated with this fourth parameter.

In accordance with a further preferred embodiment of the present invention, the setting of at least one fifth desired value range assigned to a fifth characteristic parameter of the fermentation additionally takes place, the fifth desired value range defining a fifth value range suitable for maintaining the fermentation. Accordingly, a determination of at least one measured value of the fifth characteristic parameter takes place during the fermentation process and a comparison of the measured value of the fifth characteristic parameter with at least one fifth setpoint range assigned to this fifth parameter. The addition of at least one type of microorganism to the fermentation substrate is carried out in the event that the measured value of the first characteristic parameter has a fixed relation to the first setpoint range associated with this first parameter, the measured value of the second characteristic parameter a fixed relation to that of the second The measured value of the third characteristic parameter has a fixed relation to the third setpoint range assigned to this third parameter, the measured value of the fourth characteristic parameter has a fixed relation to the fourth setpoint range associated with this fourth parameter, and the measured value of fifth characteristic parameter has a fixed relation to the fifth setpoint range associated with this fifth parameter. Preferably, at least one specified setpoint range represents a value range of the measured variable of the characteristic parameter, and the fixed relation of the measured value of this characteristic parameter to the setpoint range associated with this parameter is that the measured value lies outside the specified setpoint range. In this case, a setpoint range of the actual measured values of the corresponding parameter is thus established and it is checked whether the actually measured value lies within or outside the setpoint range.

Also preferably, additionally or alternatively, at least one specified setpoint range represents a value range of the first derivative of the measured variable according to the time of the characteristic parameter and the fixed relation of the measured values of this characteristic parameter to the setpoint range associated with this parameter is that the first derivative of the measured values after the time is outside the specified setpoint range. In this case, the speed of the change in the measured value is thus adjusted. A setpoint range of the first derivative of the measured values, ie a setpoint range which reflects the extent of the permitted rate of change, is checked in this case to determine whether the change of the actually measured values lies within or outside the setpoint range of the permitted rate of change.

Also preferably, additionally or alternatively, at least one specified setpoint range represents a range of values of the second derivative of the characteristic parameter measure, and the fixed relation of the measured values of this characteristic parameter to the setpoint range associated with that parameter is that the second derivative of the measured values is outside the setpoint range Setpoint range is. In this case, the increase or decrease in the speed of the change in the measured value is thus taken into account. A setpoint range of the second derivative of the measured values, ie a setpoint range which reflects the extent of the permitted "acceleration" of the change in the measured values, is checked in this case as to whether there is an accelerating change in the actually measured values within or outside the setpoint range of the allowed values, the increase or decrease in the speed of the change.

Of course, any combinations of characteristic parameters and types of setpoint ranges may be used. For example, it is possible to measure whether the amount of biogas produced is within a predetermined setpoint range, and at the same time to check whether the carboxylic acid concentration in the fermentation substrate changes rapidly in a short time. As any other example, an increase in the rate of change of the redox potential of the fermentation substrate may be considered and, at the same time, it may be checked whether the hydrogen content of the fermentation substrate is within the specified range

Setpoint range is.

According to a further preferred embodiment, at least one type of microorganism is added to the fermentation substrate if at least one characteristic parameter deviates from the setpoint range associated with that parameter, the measured value of the parameter being greater than a predetermined upper threshold or the measured value of the characteristic parameter being smaller is considered a set lower threshold.

For example, a setpoint range of -450 mV to -530 mV can be set for the redox potential. For example, a deviation of 1% from the upper limit of the setpoint range is suitable as the upper threshold value. The upper threshold is thus -445.5 mV (-450 mV + 4.5 mV). The lower threshold is also a deviation of 1% from the lower limit of the setpoint range. The lower threshold is therefore -535.3 mV (-530 mV-5.3 mV). The microorganisms are added in this case at a redox potential of -445.4 mV or higher or at a redox potential of -535.4 mV or less.

Particularly preferably, the lower threshold value is at least 50%, preferably at least 75% of the lower limit value of the desired value range. Likewise preferred are embodiments according to which the upper threshold value amounts to a maximum of 150%, preferably to a maximum of 125% of the upper limit value of the desired value range. According to a further preferred embodiment, the upper threshold value is at most 1 10%, preferably at most 101% of the upper limit value of the target value range and the lower threshold value at least 90%, preferably at least 99% of the lower limit value of the target value range.

According to a further embodiment, additional biomass is added to the fermentation reactor in a timely manner to the addition of the microorganisms. In this context, "timely" refers to the period of time that elapses between the addition of new substrate following the addition of the microorganisms.This time span should be kept as short as possible, which is why the term "timely" also includes a parallel addition of the microorganisms and the new substrate includes.

However, the said period may also extend to several hours to one or more days. In this case, the space load in the fermentation reactor can be continuously increased or kept approximately constant by continuous addition of new substrate, wherein the fermentation at all room loads, preferably at a space load of ≥ 0.5 kg of organic dry matter per m ³ and day [kg oTS / m ³ d], more preferably at a volume load of ≥4.0 kg oTS / m ³ d and particularly preferably at a volume load of ≥8.0 kg oTS / m ³ d can be performed, which compared to the current state of the art Increasing the room load to more than double means.

According to a further embodiment, the production of biogas from biomass takes place with constant mixing of the fermentation substrate. Due to the constant mixing of the fermentation substrate, the cultures of the hydrolytically active, acidogenic, acetogenic or methanogenic, fermentative bacteria can be better distributed in the fermentation substrate. In addition, the biogas formed can be better removed from the fermentation process. Another possibility of constant mixing may consist in the continuous gassing of the fermentation substrate during the fermentation. For example, it is conceivable to recycle the recovered biogas to the fermentation process. For example, the methane-forming microorganisms CO ₂ from the biogas as educt for Methanogenesis are fed again, which can be implemented by these with additionally freshly supplied H ₂ to methane.

The constant mixing of the fermentation substrate also leads to a uniform heat distribution in the fermentation reactor. Measurements of

Temperature in the fermentation reactor, which were carried out at periodic intervals, but also continuously, showed that the fermentation substrate in a

Temperature range of 20 ⁰ C to 80 ⁰ C, preferably at about 40 ° C to 50 ⁰ C is efficiently fermented. These temperature ranges are therefore preferred in the context of the present invention. In addition to the hydrolysis takes place in particular the last

Stage of the fermentation process, namely the formation of methane by methanogenic microorganisms, particularly efficient at elevated temperatures.

In a further preferred embodiment, the fermentation is carried out in a pH range of pH 4 to pH 9, wherein a pH range of pH 5 to pH 8.5 is preferred. The preferred setpoint ranges for the pH thus extend from a neutral to a slightly alkaline medium. These pH ranges are very well suited for the efficient formation of methane by methanogenic microorganisms, which prefer a neutral to weakly alkaline range for methanogenesis.

According to a further preferred embodiment of the present invention, a range of less than -120 mV, preferably less than -180 mV, particularly preferably less than -490 mV, in particular a range between -450 mV and -530 mV, is used as setpoint range for the redox potential. Experimental studies have shown that silage is preferably fermented in a redox potential range of -120 mV to -350 mV, more preferably -380 mV to -580 mV. In order to achieve an increased biogas yield by methanogenic microorganisms, the redox potential should be set to less than -300 mV, preferably less than -580 mV. Methanogenic microorganisms that convert CO ₂ and H ₂ or acetic acid to methane and CO ₂ often prefer a redox potential of less than -300 mV, preferably less than -500 mV to form methane. Experimental investigations have shown that the mentioned redox potential areas are particularly important for maintaining biogas production are suitable because a particularly efficient fermentation of the fermentation substrate takes place for the production of biogas.

While the hydrolysis of the fermentation substrate, as well as the acidogenesis and the acetogenesis by predominantly facultative anaerobic microorganisms that tolerate a low oxygen partial pressure, the formation of methane by CO ₂ and H ₂ or by acetic acid, usually by obligate anaerobic methane forming microorganisms. These predominantly obligate anaerobic microorganisms form methane and CO ₂ with particularly electronegative redox potentials of, for example, about -480 to -550 mV. Disruptions in the biogas synthesis process, which are associated with an increase in the redox potential in a electropositive range, can lead to a disruption of biogas synthesis, since methanogenic microorganisms are often no longer able to form methane at electropositive redox potentials, whereas the hydrolysis of the fermentation substrate, the acidogenesis , as well as the acetogenesis can take place even further. Therefore, it is advantageous to use methanogenic microorganisms, for example of the genus Methanosarcina, since these methane can form at a more electropositive redox potential than other methanogenic microorganisms. Thus, biogas production disturbances can be prevented or reduced by the use of methanogenic microorganisms which prefer a more electropositive redox potential.

In a further embodiment, fermentation substrate is added continuously and the characteristic parameters of the fermentation are continuously measured. The continuous operation of a fermentation reactor should result in a stable microbial biocenosis to a continuous production of biogas, wherein the exposure of the substrate addition to the fermentation due to a process disturbance should be reduced. In addition, the term "continuous" may include other continuous processes, such as the continuous addition of substrates and / or microorganisms.

According to another embodiment, the fermentation conditions are adapted to the growth conditions of the fermentative microorganism added. The growth conditions include the individual Growth parameters of the added culture of microorganisms, such as temperature, pH, pressure, concentrations of nutrients, trace elements and toxic products, the salt concentration of the fermentation substrate or the redox potential of the fermentation substrate. Adaptation of the fermentation conditions to individual growth parameters of the added culture of microorganisms may result in better control of fermentation processes in biogas production.

According to a further embodiment, an additional experimental fermentation of a fermentation substrate for the production of biogas is carried out, wherein the characteristic parameters of the fermentation are measured several times and from the measured values the setpoint ranges suitable for maintaining the production of biogas are determined. By the experimental

Determining the setpoint ranges, these can be tuned, for example, to certain types of substrate. This can affect the

Fermentation be made even more targeted.

According to a further preferred embodiment of the present invention, at least one type of microorganism is added in an amount to the fermentation substrate such that after addition the proportion of the added type of microorganisms is between 10 ^-8 % and 50% of the total number of microorganisms present in the fermentation substrate. In particular, depending on the size of the fermenter and thus depending on the amount of fermentation substrate, it may be necessary to add very large amounts of microorganisms in order to obtain the desired effect, since the activity of the different types of microorganisms also differs markedly this results in a different absolute amount of microorganisms, which must be added to the fermentation substrate to achieve a noticeable effect.

More preferably, the at least one species of microorganism is added in an amount to the fermentation substrate such that after addition the proportion of the added species of microorganisms is between 10 ^-6 % and 25% of the total number of microorganisms present in the fermentation substrate Preferably, the at least one species of microorganism is added in an amount to the fermentation substrate such that after addition the proportion of the added species of microorganisms is between 10 ^-4 % and 10% of the total number of microorganisms present in the fermentation substrate adding one kind of microorganisms in an amount to the fermentation substrate so that, after addition, the proportion of the kind of microorganisms added is between 10 ^-3 % and 1% of the total number of microorganisms present in the fermentation substrate.

Brief description of the drawings

To illustrate the invention and to illustrate its advantages, embodiments are given below. The exemplary embodiments will be explained in more detail in connection with FIGS. 1 and 2. It goes without saying that the statements made in connection with the exemplary embodiments are not intended to limit the invention. Show it:

Fig. 1 Results of the fermentation of maize silage: Plotted are the amount of biogas produced and the volume load of the fermenter against time;

Fig. 2 Measurement results of the fermentation of corn silage according to Figure 1: Plotted are the amount of acetic acid, the amount of propionic acid, the acetic acid equivalent and the pH value over time;

Ways to carry out the invention

In order to demonstrate the advantages of the process according to the invention, the fermentation substrate became a pure culture of the hydrolytically active fermentative bacterium

Clostridium sartagoformum added. Bacteria of the species Clostridium sartagoformum were successfully isolated from the fermentation substrate of a post-fermenter. The deposit of the organism was carried out in a pure culture at the German Collection of Microorganisms and Cell Cultures GmbH according to the Budapest Treaty (Clostridium sartagoformum SBG1 with the accession number DSM 19861).

The microorganisms were isolated using a selection medium containing carboxymethylcellulose as the sole carbon source. Carboxymethylcellulose is very similar to the cellulose contained in fermentation substrates of biogas plants and also has an improved solubility in an aqueous medium by linking the hydroxyl groups with carboxymethyl groups (-CH ₂ -COOH-). The medium used for the selection of Clostridium sartagoformum was further gassed with N ₂ and CO ₂ , so that the selection could be carried out under anaerobic conditions. Contained residual oxygen was subsequently reduced by means of 0.5 g / l Na ₂ S.

The selection medium was then inoculated with the supernatant of material from a post-fermenter. After one week of cultivation at 40 ^° C., single rods were observed as a result of microscopic analyzes. Further selection of the liquid cultures was made by smearing on anaerobic carboxymethylcellulose plates. The cell material of the grown colonies was used to amplify the microbial DNA by the Colony PCR method according to a standard program. After the sequence analysis of the colonies, the phylogenetic comparison of the sequence data generated therefrom by means of BLAST program (basic local alignment search tool) of the database www.ncbi.nlm.nih.gov that the resulting sequence can be assigned to the organism Clostridium sartagoformum as the nearest relative ,

Experiments with a pure culture of the hydrolytically active fermentative microorganism Clostridium sartagoformum SBG1 showed that the addition of Clostridium sartagoformum SBG1 to the highly viscous, viscous carboxymethylcellulose-containing selection medium leads to a successive liquefaction of the medium. Figures 1 and 2 show measurement results of various characteristic parameters during a fermentation process in a test fermenter with a volume of 150 I. Fermented corn silage at a temperature of about 40 ⁰ C.

In Figure 1, the curve provided with the reference numeral 1 shows the time course of the entire generated biogas in standard liters (gas volume at 273.15 K and 1013 mbar) per day (Nl / d) and the curve provided with the reference numeral 5, the time course of Volume load of the fermenter in kilograms of organic dry matter per cubic meter per day (kg oTS / m ³ d).

Figure 2 shows the time course of the pH (curve denoted by 25), the acetic acid equivalents (curve denoted by 30), the acetic acid concentration (curve denoted by 35) and the propionic acid concentration (curve denoted by 40). The acid concentrations are given in milligrams per liter of fermentation substrate (mg / l).

On the 7th day of the fermentation process, a disturbance of the gas production process occurred. As a result of the disturbance, the characteristic parameters of the fermentation "amount of biogas produced", "pH of the fermentation substrate", "volume loading of the fermentation reactor", "carboxylic acid content of the fermentation substrate" and "proportions of different carboxylic acids in the fermentation substrate" determined by the setpoint ranges associated with these parameters, a deviation of the measured values of the parameters "amount of biogas produced", "pH", "viscosity of the fermentation substrate" and "carboxylic acid content of the fermentation substrate" of the predetermined target value ranges.

In the figure 1, the strong decrease in the total yield of biogas 1 and the sudden drop in the space load 5 can be seen. FIG. 2 shows the strongly increasing concentrations of the fatty acids 30, 35, 40, wherein the increase of the acetic acid equivalents 30 was used as a characteristic parameter of the fermentation. In response to the deviation of the characteristic parameters from the predetermined set point ranges, a pure culture of Clostridium sartagoformum was added to the fermentation substrate. The time of addition is indicated in FIGS. 1 and 2 by the triangle 20. For this purpose, the cell mass from 11 of a preculture of Clostridium sartagoformum, which had been incubated for 5 days at a temperature of about 40 ⁰ C, are used. The cell count of this preculture had a cell density of about 2.0 × 10 ⁸ cells / ml with a proportion of living cells of more than 90%.

The addition of the pure culture of Clostridium sartagoformum SBG1 to the fermentation substrate causes an increase in the amount of biogas 1 produced with a simultaneous sharp decline in the acetic acid equivalents 30 and the acetic acid concentration 35. At the same time, the volume load 5 of the fermentation reactor could be increased.

During the following 13 days of testing (Day 7 to Day 20), the fermentation process stabilizes with a satisfactory yield of biogas. Figures 1 and 2 thus show the positive effect of adding a pure culture of Clostridium sartagoformum SBG1 in response to a disruption of a biogas production process caused by the deviation of the characteristic parameters of the fermentation "amount of biogas produced" and "carboxylic acid content of the fermentation substrate" from these Parameters assigned predetermined setpoint ranges could be determined. The addition of a pure culture of Clostridium sartagoformum SBG1 stabilized the fermentation process and prevented the fermenter from crashing.

Claims

claims

1. A process for the production of biogas from biomass in one

Fermentation reactor with the steps

a) definition of at least one first setpoint range associated with a first characteristic parameter of the fermentation, the first setpoint range defining a first value range suitable for maintaining the fermentation,

b) definition of at least one second desired value range assigned to a second characteristic parameter of the fermentation, the second setpoint range defining a second value range suitable for maintaining the fermentation,

c) determining at least one measured value of the first characteristic parameter during the fermentation process,

d) determining at least one measured value of the second characteristic parameter during the fermentation process,

e) comparison of the measured value of the first characteristic parameter with at least one first setpoint value range assigned to this first parameter,

f) comparison of the measured value of the second characteristic parameter with at least one second setpoint value range assigned to this second parameter,

g) addition of at least one type of microorganism to the fermentation substrate if the measured value of the first characteristic parameter has a fixed relation to the first setpoint range associated with that first parameter, and if the measured value of the second characteristic parameter has a fixed relation to the second setpoint range associated with this second parameter.

2. The method according to claim 1, characterized in that the first and second characteristic parameters of the fermentation is selected from the

Group consisting of

Amount of biogas produced,

Methane content of the generated biogas,

Hydrogen content of the generated biogas, - pH of the fermentation substrate,

Redox potential of the fermentation substrate,

Carboxylic acid content of the fermentation substrate,

Proportions of various carboxylic acids in the fermentation substrate,

Hydrogen content of the fermentation substrate, - proportion of the dry matter in the fermentation substrate,

Proportion of organic dry matter in the fermentation substrate,

Viscosity of the fermentation substrate.

Room load of the fermentation reactor.

3. The method according to at least one of claims 1 and 2, characterized in that the added in step g) types of microorganisms are selected from the group consisting of hydrolytically active fermentative microorganisms, acidogenic fermentative microorganisms, acetogenic fermentative microorganisms and methanogenic fermentative microorganisms.

4. The method according to at least one of claims 1 to 3, characterized in that at least two types of microorganisms are added.

5. The method according to at least one of claims 1 to 4, characterized in that at least three types of microorganisms are added.

6. The method according to at least one of claims 1 to 5, characterized in that at least four types of microorganisms are added.

7. The method according to at least one of claims 4 to 6, characterized in that the added types of microorganisms are selected from at least two members of the group consisting of hydrolytically active fermentative microorganisms, acidogenic fermentative microorganisms, acetogenic fermentative microorganisms and methanogenic fermentative microorganisms.

8. The method according to at least one of claims 5 and 6, characterized in that the added types of microorganisms are selected from at least three members of the group consisting of hydrolytically active fermentative microorganisms, acidogenic fermentative

Microorganisms, acetogenic fermentative microorganisms and methanogenic fermentative microorganisms.

9. The method according to claim 6, characterized in that at least one kind of a hydrolytically active fermentative microorganism, at least one kind of an acidogenic fermentative microorganism, at least one kind of an acetogenic fermentative microorganism and at least one kind of a methanogenic fermentative microorganism are added.

10. The method according to at least one of claims 1 to 9, characterized in that the individual types of microorganisms are added in the form of cultures of microorganisms, wherein the cultures of microorganisms each consist predominantly of a kind of microorganisms.

11. The method according to claim 10, characterized in that in the culture of microorganisms predominantly present type of microorganisms constitutes at least 25% of the total number of microorganisms present in the culture.

12. The method according to claim 1 1, characterized in that in the culture of microorganisms predominantly present type of microorganisms accounts for at least 50% of the total number of microorganisms present in the culture.

13. The method according to claim 12, characterized in that in the culture of microorganisms predominantly present type of microorganisms constitutes at least 66% of the total number of microorganisms present in the culture.

14. The method according to claim 13, characterized in that in the culture of microorganisms, the predominantly present type of microorganisms makes up at least 75% of the total number of microorganisms present in the culture.

15. The method according to claim 14, characterized in that in the culture of microorganisms, the predominantly present type of microorganisms accounts for at least 90% of the total number of microorganisms present in the culture.

16. The method according to claim 15, characterized in that in the culture of microorganisms predominantly present type of microorganisms makes up at least 95% of the total number of microorganisms present in the culture.

17. The method according to at least one of claims 1 to 16, characterized in that at least one pure culture of microorganisms is added.

18. The method according to at least one of claims 1 to 17, characterized in that at least one hydrolytically active fermentative microorganism of a genus selected from the group consisting of Anaerophaga, Lachnospira, Paenibacillus, Pseudomonas, Leptothrix, Burkholderia, Ralstonia, Bradyrhizobium, Arcobacter, Fibrobacter, Streptococcus, Planomicrobium, Turicibacter, Ruminococcus, Deinococcus, Peptostreptococcus, Vagococcus, Proteus, Clostridium, Bacillus, Bacteroides, Cytophaga and Sporocytophaga.

19. The method according to at least one of claims 1 to 18, characterized in that at least one acidogenic fermentative microorganism of a genus selected from the group consisting of Flavobacterium, Delftia, Selenomonas, Butyrivibrio, Schwarztia, Aminomonas, Paenibacillus, Anaeorophaga, Halothermothrix, Bacillus, Eubacterium , Clostridium,

Acetanaerobacterium, Sedimentibacter, Corynebacterium, Bifidobacterium, Microbacterium, Williamsia and Cryptobacterium.

20. The method according to at least one of claims 1 to 19, characterized in that at least one acetogenic fermentative microorganism of a genus selected from the group consisting of Acetobacterium, Synthrobobacter, Synthrophococcus, Pelobacter, Acetivibrio, Sporobacter, Lactobacillus, Desulfomonas, Methylobacterium, Caulobacter,

Acetanaerobacterium, Synthrophobotulus, Desulfonosporus, Desulfotomaculum, Gelria, Thermoterrabacterium, Syntrophomonas,

Syntrophothermus, Moorella, Aminomonas and Anaerobaculum is added.

21. The method according to at least one of claims 1 to 20, characterized in that at least one methanogenic fermentative microorganism of a genus selected from the group consisting of

Methanocorpusculum, Methanoculleus, Methanogenium,

Methanomethylovorans, Methanobacterium, Methanobacter bacteria, Methanococcus, Methanomicrobium, Methanosaeta,

Methanospirillum, Methanothermobacter and Methanothermococcus is added.

22. The method according to at least one of claims 1 to 21, characterized in that after step b) the step bi) definition of at least one third setpoint value range assigned to a third characteristic parameter of the fermentation, the third setpoint range defining a third value range suitable for maintaining the fermentation,

is performed, after step d) the step

d ^ determination of at least one measured value of the third characteristic

Parameters during the fermentation process,

is performed, after step f) the step

f-i) comparison of the measured value of the third characteristic parameter with at least one third setpoint range assigned to this third parameter,

is performed and in step

g) the addition of at least one type of microorganisms to the fermentation substrate takes place, if the measured value of the first characteristic parameter has a fixed relation to the first setpoint range associated with that first parameter, the measured value of the second characteristic parameter has a fixed relation to that second parameter assigned second setpoint range and the measured value of the third characteristic parameter has a fixed relation to the third this third parameter associated

Reference value range has.

23. The method according to claim 22, characterized in that after step bi) the step

b ₂ ) establishing at least one fourth setpoint range associated with a fourth characteristic parameter of the fermentation, wherein the fourth set point range defines a fourth range of values suitable for maintaining the fermentation,

is performed, after step di) the step

d ₂ ) determining at least one measured value of the fourth characteristic parameter during the fermentation process,

is performed, after step f-i) the step

f ₂ ) comparison of the measured value of the fourth characteristic parameter with at least one fourth setpoint value range assigned to this fourth parameter,

is performed and in step

g) the addition of at least one type of microorganisms to the fermentation substrate takes place, if the measured value of the first characteristic parameter has a fixed relation to the first setpoint range associated with that first parameter, the measured value of the second characteristic parameter has a fixed relation to that second parameter The measured value of the third characteristic parameter has a fixed relation to the third setpoint range associated with this third parameter, and the measured value of the fourth characteristic parameter has a fixed relation to the fourth setpoint range associated with this fourth parameter.

24. The method according to claim 23, characterized in that after step b ₂ ) the step

bs) definition of at least one, a fifth characteristic parameter of the fermentation associated fifth setpoint range, wherein the fifth setpoint range defines a fifth range of values suitable for maintaining the fermentation,

is performed, after step d ₂ ) the step

d ₃ ) determining at least one measured value of the fifth characteristic parameter during the fermentation process,

is performed, after step f ₂ ) the step

f ₃ ) comparison of the measured value of the fifth characteristic parameter with at least one fifth setpoint range assigned to this fifth parameter,

is performed and in step

g) the addition of at least one type of microorganisms to the fermentation substrate takes place, if the measured value of the first characteristic parameter has a fixed relation to the first setpoint range associated with that first parameter, the measured value of the second characteristic parameter has a fixed relation to that second parameter The measured value of the third characteristic parameter has a fixed relation to the third setpoint range associated with this third parameter, the measured value of the fourth characteristic parameter has a fixed relation to the fourth setpoint range associated with this fourth parameter, and the measured value of the fifth characteristic parameter has a fixed relation to the fifth setpoint range assigned to this fifth parameter.

25. The method according to claim 1, characterized in that at least one defined desired value range represents a value range of the measured variable of the characteristic parameter and the defined relation of the measured value of this characteristic parameter to the setpoint range associated with this parameter is that the measured value is Value is outside the specified setpoint range.

26. The method according to at least one of claims 1 to 25, characterized in that at least one specified value range a

Range of values of the first derivative of the measured value according to the time of the characteristic parameter and the fixed relation of the measured values of this characteristic parameter to the setpoint range associated with this parameter is that the first derivative of the measured values lies outside the specified setpoint range.

27. The method according to claim 1, wherein at least one specified setpoint range represents a value range of the second derivative of the measured variable according to the time of the characteristic parameter and the fixed relation of the measured values of this characteristic parameter to the setpoint range associated with this parameter This is because the second derivative of the measured values is outside the specified setpoint range.

28. The method according to at least one of claims 1 to 27, characterized in that in time for the addition of the microorganisms additional biomass is added to the fermentation reactor.

29. The method according to at least one of claims 1 to 28, characterized in that the space load in the fermentation reactor is continuously increased by the continuous addition of biomass.

30. The method according to at least one of claims 1 to 29, characterized in that the production of biogas from biomass at a space load of ≥ 0.5 kg oTS / m ³ d, preferably ≥ 4.0 kg oTS / m ³ d, especially preferably ≥ 8.0 kg oTS / m ³ d.

31. The method according to at least one of claims 1 to 30, characterized in that the production of biogas from biomass occurs under constant mixing of the fermentation substrate.

32. The method according to at least one of claims 1 to 31, characterized in that the production of biogas from biomass at a temperature of 20 ⁰ C to 80 ⁰ C, preferably at a temperature of 40 ° C to 50 ⁰ C is performed.

33. The method according to at least one of claims 1 to 32, characterized in that as a setpoint range for the pH, a range of 4 to 9, preferably a range of 5 to 8.5 is used.

34. Method according to claim 1, characterized in that the setpoint range for the redox potential is a range of less than -120 mV, preferably less than -180 mV, particularly preferably less than -490 mV, in particular a range between -450 mV and 530 mV is used.

35. The method according to at least one of claims 1 to 34, characterized in that fermentation substrate is added continuously and the

Parameters of the fermentation are measured continuously.

36. The method according to at least one of claims 1 to 35, characterized in that in addition an experimental fermentation of a fermentation substrate for the production of biogas is carried out, wherein the characteristic parameters of the fermentation are measured several times and from the measured values for maintaining the production of Biogas suitable setpoint ranges are determined.

37. Method according to at least one of claims 1 to 36, characterized in that the at least one type of microorganism is added to the fermentation substrate in an amount such that, after addition, the proportion of the added type of microorganisms is between 10 ^-8 % and 50% of the microorganisms Total number of present in the fermentation substrate microorganisms.

38. Method according to claim 1, characterized in that the at least one type of microorganism is added to the fermentation substrate in an amount such that, after addition, the proportion of the added type of microorganisms is between 10 ^-6 % and 25% of the microorganisms

Total number of present in the fermentation substrate microorganisms.

39. The method according to at least one of claims 1 to 38, characterized in that the at least one type of microorganisms is added in an amount to the fermentation substrate that, after addition, the proportion of the added type of microorganisms between 10 ^"4 % and 10% of Total number of present in the fermentation substrate microorganisms.

40. The method according to at least one of claims 1 to 39, characterized in that the at least one type of microorganisms in a

Amount is added to the fermentation substrate that after addition, the proportion of the added type of microorganisms is between 10 ^"3 % and 1% of the total number of present in the fermentation substrate microorganisms.