JP2008253872A - Co-fermentation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a co-fermentation method which can enhance the methane producing efficiency in a methane fermentation tank by reducing fermentation inhibiting properties such as temperature stress, oxidation stress, ammonia stress, etc. and can efficiently perform fermentation treatment of garbage or the like difficult to ferment at a high temperature according to circumstances. <P>SOLUTION: The excretion of a ruminant originating from the paunch (lumen) is mixed with food waste in a volume of 10-30% to prepare a fermentation raw material. This fermentation raw material is introduced into the fermentation tank 3 and the temperature in the fermentation tank 3 is adjusted to 60-90°C to perform methane fermentation. Alternatively, the fermentation raw material prepared by mixing 10-30 vol.% of the excretion of the ruminant originating from the paunch (lumen) with organic sludge and food waste is introduced into the methane fermentation tank 3 and the temperature in the methane fermentation tank 3 is set to 60-90°C to perform co-fermentation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a co-fermentation method, and more particularly, to a co-fermentation method that can prevent temperature stress and increase the temperature rise effect in a methane fermentation tank, and can effectively ferment garbage.

  Sewage treatment sludge (sewage sludge), human waste treatment sludge (sewage sludge), and organic waste such as garbage from methane fermentation using biomass as raw materials, the generated methane gas can be used for biogas power generation, etc. It is attracting attention for its excellence.

  Conventionally, medium-temperature fermentation (about 37 ° C) has been the mainstream methane fermentation method, but recent studies have shown that fermentation at higher temperatures (about 55 ° C) is also very good (large) VS utilization rate. (Patent Document 1).

  For example, in a sludge digestion tank at a sewage treatment plant, a place where a medium temperature fermentation (about 37 ° C.) shifts to a high temperature fermentation has come out.

  However, the problem with increasing the temperature of methane fermentation is that it may be susceptible to fermentation inhibition. For example, fermentation inhibition due to the following stress may be mentioned.

  (1) Temperature stress: The difference between the biomass temperature before charging and the temperature of the fermentation broth in the methane fermenter tends to increase, so that the temperature in the methane fermenter decreases when the biomass is charged. When temperature falls, it becomes stress and fermentation ability falls. In particular, high-temperature fermentation tends to be affected by temperature and stress is likely to occur. Sufficient acclimatization time (for example, 10 days or more) is required for temperature changes.

  (2) Oxidative stress: If dissolved oxygen is present in the input biomass when the biomass is input, the methanogen is subjected to oxidative stress. Due to the influence of such oxidative stress, the amount of biogas produced is significantly reduced.

  (3) Ammonia stress: Ammonia contained or generated in biomass raw material is a fermentation inhibitor, and the higher the vapor pressure, the greater the influence.

Furthermore, according to the study by the present inventors, biomass such as garbage discharged from hotels, inns, condominiums, restaurants, supermarkets, convenience stores, food manufacturing industries, food sales, food distribution industries, general households, etc. It was found that high temperature fermentation was difficult due to the above temperature stress. This may be due to the relatively large load fluctuations in food waste and the possibility that methanogens are not sufficiently resistant to stress. There is a problem that it takes a long time to acclimate methanogenic bacteria that can cope with temperature stress in a methane fermenter to create a high temperature methane fermentation environment.
JP 2000-343100 A

  Therefore, an object of the present invention is to reduce the fermentation inhibitory properties such as temperature stress, oxidative stress, and ammonia stress to increase the methane production efficiency in the methane fermenter. The object is to provide a co-fermentation method that can efficiently ferment waste and the like.

  Other problems of the present invention will become apparent from the following description.

    The above problems are solved by the following inventions.

(Claim 1)
A fermented raw material obtained by mixing ruminant manure derived from rumen into 10% to 30% of the volume of food waste is introduced into the methane fermenter, and the temperature in the methane fermenter is adjusted to 60. A co-fermentation method characterized in that methane fermentation is carried out by adjusting the temperature within a range of from 0C to 90C.

(Claim 2)
A fermentation raw material in which ruminant manure derived from rumen is mixed with organic sludge and food waste in a volume of 10% to 30% is introduced into the methane fermenter, and the inside of the methane fermenter The co-fermentation method characterized by adjusting the temperature of this to the range of 60 degreeC or more and 90 degrees C or less, and performing methane fermentation.

(Claim 3)
The co-fermentation method according to claim 1 or 2, wherein the food waste is a food processing residue or a koji residue.

(Claim 4)
The co-fermentation method according to claim 3, wherein the koji residue contains coffee koji or tea leaves.

(Claim 5)
The co-fermentation method according to any one of claims 2 to 4, wherein the organic sludge includes sludge generated from a water treatment process for aerobically treating organic wastewater.

  According to the present invention, fermentation inhibition such as temperature stress, oxidative stress, and ammonia stress can be reduced to increase methane production efficiency in the methane fermentation tank, and garbage that is difficult to be fermented at high temperature depending on conditions. It is possible to provide a co-fermentation method that can efficiently ferment the sucrose.

  Embodiments of the present invention will be described below.

  In the present invention, examples of the food waste that is one kind of biomass raw material include food waste, which includes food processing residues such as agricultural and fishery industry waste and food processing waste; Including potato residue. In the present invention, a good effect is exhibited when the cocoon residue is coffee candy or tea husk.

  In the present invention, another type of biomass material is ruminant manure derived from the rumen. A ruminant is an animal with an organ that digests food by repeating the process of chewing food in the mouth, sending it to the stomach and partially digesting it, then returning it to the mouth and chewing it again. , Ruminants such as sheep and deer, and those belonging to the subfamily of camels and llamas.

  Furthermore, in this invention, you may mix | blend organic sludge with food type waste. Organic sludge is sludge generated from a water treatment process for aerobically treating organic wastewater, such as sewage treatment sludge and human waste treatment sludge.

  The mixing ratio of food waste (which may contain organic sludge) and ruminant manure derived from rumen is ruminant manure derived from rumen. The volume ratio is 10% or more and 30% or less, preferably 10% or more and 20% or less. If the compounding ratio is less than 10%, the effect of relieving stress is small, so the amount of biogas generated is small, and if it exceeds 30%, the ignition loss VS (wt%) decreases, so the amount of biogas generated is difficult to increase. Become.

  The blending ratio of organic sludge to food waste in the biomass raw material is essentially not limited in the present invention.

  Organic waste sludge generated from food processing residue and waste residue such as food processing residue and water treatment process should be quickly mixed with existing fermentation residue, especially when methane fermentation is performed in a complete mixing system fermenter. Is important in maintaining the overall fermentation rate.

  Further, in the purge type reactor (plug flow type), it is necessary to sufficiently mix the fermentation liquid extracted before charging the reactor with the biomass.

  In the present invention, what is blended with two or more kinds of biomass raw materials is fermented, which is called co-fermentation.

  In the co-fermentation method of the present invention, the mixed fermentation raw material is introduced into a methane fermentation tank, and the temperature in the methane fermentation tank is adjusted to a range of 60 ° C. or higher and 90 ° C. or lower to perform methane fermentation.

  Therefore, in this invention, when it is called high temperature fermentation, it is performing fermentation in the range of 60 degreeC or more and 90 degrees C or less.

  As described above, high-temperature fermentation is sensitive to stresses such as temperature stress, oxidative stress, and ammonia stress, but ruminant manure derived from the rumen is converted into biomass such as food waste. It was found that when blended in a certain amount in the raw material, the effect of alleviating each of the above stresses was exhibited, resulting in an apparent increase in the amount of biogas generated and a reduction in the amount of gas generated due to fermentation inhibition.

  In medium-temperature fermentation (37 ° C) and conventional high-temperature fermentation (55 ° C), this effect (the rumen-derived ruminant manure mixing effect) is less susceptible to fermentation inhibition than stress. The effect is hard to appear. On the other hand, the present invention is effective in methane fermentation at a high temperature with a high VS utilization rate and a high biogas generation rate in a high-temperature fermentation in the range of 60 ° C. to 90 ° C.

  In a mixture of general garbage biomass and livestock manure biomass, when the proportion of livestock manure biomass increases, the amount of organic matter (VS value) effective for methane fermentation decreases and the amount of gas generated decreases. However, if the livestock manure is ruminant manure having a lumen, the effect of each fermentation inhibition factor is mitigated, so that it has an effect of apparently promoting fermentation.

  This is because rumen-derived ruminant manure creates an environment that is durable against various stresses and is easy to maintain the bacterial metabolism. The effect of rumen-derived ruminant manure mixing is demonstrated in methane fermentation at high temperatures with high VS utilization and high biogas generation. This is because, as described above, fermentation at high temperature is particularly sensitive to stress.

  Sewage sludge and food waste must be strictly controlled in terms of temperature, load, oxygen, etc., but rumen-derived ruminant manure is mixed with 10% or more and 30% or less to ensure good fermentation. Done. Rumen-derived ruminant manure contains methanogens derived from the rumen, which eliminates the need for strict management.

  There has been an example of mixing manure and garbage in the past, and it has been done as a matter of course, but the manure was mixed with 90% of the garbage and 10% of the garbage, and the amount of garbage input was small. .

  The biomass raw material is mainly garbage, and it is not a mixture of ruminant ruminant manure derived from a small amount (predetermined amount) and high-temperature fermentation (60 to 90 ° C.).

  In the present invention, the pressure in the methane fermentation tank is preferably in the range of 0.2 MPa to 5 MPa. This fermentation pressure is preferably a natural fermentation pressure generated by fermentation without forcibly pressurizing.

  Here, “without forcibly pressurizing” means that a technique for artificially increasing the pressure in the fermenter using a pressurizing device such as a compressor is not adopted.

  In addition, “natural fermentation pressure generated by fermentation” means that the pressure in the methane fermentation tank becomes high due to the formation of gaseous components such as methane by biological reactions such as methane fermentation in a closed fermentation tank. Means.

  In such a pressure range, the VS utilization efficiency is improved, and the biogas purification effect and the biogas collection efficiency are increased. The upper limit of the pressure is determined by the relationship between the pressure structure cost of the methane fermenter and the use efficiency of volatile organic matter, the biogas purification effect and the biogas collection efficiency, and if it exceeds 5 MPa, the effect of the pressure structure cost increases.

  A preferable aspect in the present invention is to increase the pressure in the fermenter to a range of 0.2 MPa to 5 MPa by natural fermentation pressure generated by fermentation.

  The methane fermenter preferably has a configuration that does not hinder the activity of the anaerobic methanogen, and is constituted by, for example, a tank that completely blocks air. A tank needs to be comprised with the pressure | voltage resistant container which can endure the pressure of the range of 0.2 MPa-5 MPa, and the material and thickness of a tank outer wall will not be specifically limited if it is a pressure | voltage resistant container.

  The methane fermentation tank can be provided with a pressure sensor for detecting whether or not the pressure is in the range of 0.2 MPa to 5 MPa, and a pressure release valve that can release the pressure when the pressure rises to 5 MPa or more. Can be provided.

  Although the method of making the inside of a methane fermentation tank high temperature is not specifically limited, As a preferable aspect, heating means, such as warm water or an electric heater, can be installed in the fermentation tank inside or the exterior. In the present invention, it is also preferable to provide a temperature measurement sensor in order to efficiently perform high-temperature fermentation.

  In the present invention, it is also preferable that such biomass is heated using heat exchange or the like before being introduced into the fermenter. This is because the temperature stress factor can be reduced.

  FIG. 1 illustrates a preferred system example for carrying out the methane fermentation method of the present invention. In FIG. 1, two or more kinds of biomass are mixed and stored, and are quantitatively conveyed to a transport pipe 20 by a screw pump 2 and sent to a methane fermentation tank 3. In the process leading to the methane fermenter 3, the heat exchanger 4 heats it. The methane fermentation tank 3 includes a heating heater 30 and one or more stirrers 31, and includes a pressure sensor (not shown), a temperature sensor, a pressure adjustment valve (for example, releases pressure when pressurized to 5 MPa or more), and the like. Is provided.

The methane fermentation tank 3 is adjusted to a temperature range of 60 ° C. or higher and 90 ° C. or lower, and methane fermentation is performed in a range of a natural fermentation pressure of 0.2 MPa to 5 MPa generated by fermentation. The produced biogas has a high methane gas concentration but a low CO ₂ or H ₂ S concentration.

The digested liquid is discharged from the discharge pipe 32, heat-exchanged with the biomass in the heat exchanger 4, and warms the biomass. Since the digestive fluid has a high fermentation temperature of 60 ° C. or higher, the temperature (heat content) can be used. After heat exchange, the CO ₂ is sent to the degassing device 5 where the CO ₂ is degassed. Thereafter, the ammonia stripping device 6 is reached and ammonia is recovered. The ammonia stripping apparatus 6 has a filler 60, sprays digestive juice from the upper side to the lower side of the filler 60, sends air from below, and performs ammonia stripping.

  In the present invention, from the methane fermentation tank 3 to the ammonia stripping device 6, no transfer means such as a pump is required to transfer the digested liquid. This is because the inside of the methane fermentation tank 3 is pressurized within the range of the natural fermentation pressure of 0.2 MPa to 5 MPa. Therefore, there is a significant reduction in equipment costs and power costs.

  Methanogens coexist with many types of microorganisms, and other organisms provide a substrate for the growth of methanogens.

  The biomass introduced into the methane fermenter is a mixture of rumen-derived ruminant manure and garbage, and organic sludge. These biomasses include protein, starch, fat, and fiber (cellulose). However, these substrates are reduced in molecular weight by hydrolyzing bacteria, acid-fermenting bacteria, etc., and become substrates of methanogenic bacteria to cause a methane fermentation reaction.

In the present invention, methane fermentation sludge is sludge containing rumen-derived methanogens, and such sludge is biologically-derived sludge in a methane fermentation tank. Such sludge contains methanogens in the range of 10 ⁶ to 10 ⁹ cells / cm ³ .

  Hereinafter, the effect of the present invention is illustrated by examples.

Example 1
A 10-liter fully mixed methane fermentation reactor is mixed with slurries of sludge generated in a homogenizer and sludge (concentrated sludge) generated in a wastewater treatment facility at a volume ratio of 1: 1, and further, rumen-derived milking cow manure 10%, 15%, 20% and 25% were mixed in a volume ratio, the fermentation temperature was set to 60 ° C., and a methane fermentation test was conducted in batch mode for up to 30 days.

  The generated gas was received in a gas holder after completion of fermentation, and the total amount was divided by the number of days of fermentation to determine the amount of gas generated per day.

Comparative Example 1
In Example 1, the mixing rate of milking cow manure was set to 0% and 5%, and a fermentation test was performed in the same manner to determine the amount of gas generated per day.

Comparative Example 2
As in Example 1, 10 L of fully mixed methane fermentation reactor was mixed with slurries of sludge generated in a homogenizer and sludge (concentrated sludge) generated at a wastewater treatment facility at a volume ratio of 1: 1, and further milked. A methane fermentation test was conducted in batch mode for a maximum of 30 days with 0%, 5%, 10%, 15% and 20% of cow manure mixed in a volume ratio and the fermentation temperature set at 55 ° C.

  The generated gas was received in a gas holder after completion of fermentation, and the total amount was divided by the number of days of fermentation to determine the amount of gas generated per day.

Comparative Example 3
In Comparative Example 2, the fermentation test was similarly performed at a fermentation temperature of 37 ° C., and the amount of gas generated per day was determined.

(Evaluation results)
FIG. 2 shows the amount of gas generated in Experimental Example 1 and Comparative Examples 1 to 3 above, and the VS of each biomass (mixing ratio of milking cows 0%, 5%, 10%, 15%, 20%, 25%). A graph summarizing the amounts is shown.

  In the milking cow manure mixing ratio of Example 1, 10%, 15%, 20%, and 25%, the amount of gas generation is drastically compared with the milking cow manure mixing ratio of Comparative Example 1 being 0% and 5% even at the same fermentation temperature. It turns out that there are many.

  The mixing rate of milking cow manure in Example 1 is 20% and the gas generation amount of 25% does not change because the amount of VS that can be used for methane fermentation has decreased because the ratio of milking cow manure increased. It seems that has reached the peak.

  In Comparative Example 2 (methane fermentation temperature 55 ° C.) and Comparative Example 3 (methane fermentation temperature 37 ° C.), it can be seen that the effect of mixing milking cow manure is weak.

  In medium temperature fermentation (37 ° C) and conventional general high temperature fermentation (55 ° C), this effect (the rumen-derived cow manure mixing effect) is less susceptible to fermentation inhibition than stress, The effect is difficult to appear. On the other hand, the present invention is effective in methane fermentation at a high temperature with a high VS utilization rate and a high biogas generation rate in a high temperature fermentation in the range of 60 ° C. to 90 ° C. It was supported.

Example 2
A 10-liter fully mixed methane fermentation reactor is mixed with slurries of sludge produced by a homogenizer and sludge (concentrated sludge) generated in a wastewater treatment facility at a volume ratio of 1: 1, and milk cow manure is further mixed at a volume ratio of 10 The fermentation temperature was set to 60 ° C. while supplying 500 ml of the mixed biomass once a day, and a methane fermentation test was conducted.

When methane fermentation is sufficiently carried out, 500 ml of sludge soaked in hydrogen peroxide and subjected to oxidation treatment (provided with O ₂ ) is added, and the original oxidation treatment is not started from the next day. The operation was continued after returning to biomass, and the influence of oxidative stress was investigated by measuring the amount of gas generated and the oxidation-reduction potential (ORP).

Comparative Example 4
Methane fermentation was performed in the same manner as in Example 2 except that the mixing ratio of milking cow manure was 5%.

Comparative Example 5
Methane fermentation was carried out in the same manner except that the mixing ratio of milking cow manure in Example 2 was 0%.

(Evaluation results)
FIG. 3 shows the results of Example 2 and Comparative Examples 4 and 5.

  Throughout Example 2 and Comparative Examples 4 and 5, the redox potential was approximately 560 mV. Oxidative stress caused by oxidation-treated sludge is thought to be due to instantaneous oxygen contamination and generation of reactive oxygen species that do not affect the oxidation-reduction potential.

  In Comparative Examples 4 and 5, oxidation treatment sludge was added to cause oxidative stress, and the amount of gas generated was significantly reduced. Finally, methane fermentation was stopped and no gas was generated. It can be seen that the amount of gas generated recovered after 6 days although the amount of gas generated decreased temporarily, and fermentation inhibition due to oxidative stress was alleviated.

The figure which shows the example of a preferable system which implements the methane fermentation method of this invention The graph which shows the relationship between the milking cow manure mixing rate and gas generation amount in fermentation temperature 37 degreeC, 55 degreeC, and 60 degreeC Graph showing the effect of oxidative stress due to oxidation sludge

Explanation of symbols

1: Storage tank 2: Screw pump 20: Transport pipe 3: Methane fermentation tank 30: Heating heater 31: Stirrer 32: Discharge pipe 4: Heat exchanger 5: Deaerator 6: Ammonia stripping apparatus 60: Filler

Claims (5)

  A fermented raw material obtained by mixing ruminant manure derived from rumen into 10% to 30% of the volume of food waste is introduced into the methane fermentation tank, and the temperature in the methane fermentation tank is adjusted to 60. A co-fermentation method characterized in that methane fermentation is carried out by adjusting the temperature within a range of from 0C to 90C.   A fermentation raw material in which ruminant manure derived from rumen is mixed with organic sludge and food waste in a volume of 10% to 30% is introduced into the methane fermenter, and the inside of the methane fermenter The co-fermentation method is characterized in that methane fermentation is carried out by adjusting the temperature of the mixture to a range of 60 ° C. to 90 ° C.   The co-fermentation method according to claim 1 or 2, wherein the food waste is a food processing residue or a koji residue.   The co-fermentation method according to claim 3, wherein the koji residue contains coffee koji or tea leaves.   The co-fermentation method according to any one of claims 2 to 4, wherein the organic sludge includes sludge generated from a water treatment process for aerobically treating organic wastewater.

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