Methods for producing liquid fertilizer, compost, and bedding material

Abstract

To provide a method of producing liquid fertilizer capable of preventing nitrogen components in soil and underground water from increasing and of decreasing the liquid volume from a methane bio-fermentation liquid, upon spreading it over the farmland as liquid fertilizer.SOLUTION: When a methane bio-fermentation liquid is subjected to a solid / liquid separation treatment to produce compost and bedding from the solid and the filtrate is used as liquid fertilizer, the nitrogen components migrating to the liquid fertilizer and the liquid volume of the liquid fertilizer can be decreased by adding a prescribed polymeric coagulant when the solid / liquid separation treatment is being carried out.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a method for producing liquid fertilizer, compost, and bedding. More specifically, this invention relates to a method for producing liquid fertilizer, compost, and bedding using livestock manure as a raw material. More specifically, this invention relates to a method for producing liquid fertilizer, compost, and bedding with controlled nitrogen content. [Background technology]

[0002] Methane fermentation is a technology that generates and recovers methane, a renewable energy source, from organic matter such as livestock waste and food waste, using methane-fermenting microorganisms under anaerobic conditions. In recent years, power generation projects utilizing the Feed-in Tariff (FIT) system have attracted attention. The liquid remaining after methane recovery is methane biofermentation digestate (hereinafter also referred to as "digestate"), which is produced in almost the same amount as the raw materials. It has been pointed out that the energy and cost required to treat digestate as waste are significant. On the other hand, since digestate contains fertilizer components such as nitrogen, phosphorus, and potassium, as well as organic matter, its use in agricultural land is a promising option. The Basic Plan for Food, Agriculture and Rural Areas (Ministry of Agriculture, Forestry and Fisheries) also states that it will promote the reduction of agricultural production costs through the effective utilization of by-products such as digestate generated in the biogas production process.

[0003] Methane biofermentation, which produces methane by fermenting livestock manure and converts it into electricity, is an effective technology for obtaining energy resources and is an important technology for promoting a circular economy. The digestate, which is the residue after methane generation, is generally used as liquid fertilizer on farmland.

[0004] However, nitrogen concentrations in soil are rising nationwide, making it difficult to directly apply nitrogen-rich digestate to farmland. The nitrogen in digestate is mainly ammoniacal nitrogen, which then turns into NO2 in the soil. - NO3 - These are converted to NO2 - NO3 -When nitrogen seeps into groundwater and dissolves, it can bind to human hemoglobin, posing a risk of adverse effects, especially on infants. Furthermore, the provisional limit for nitrogen content in agricultural and livestock wastewater has recently been lowered from 600 mg / L to 500 mg / L. Additionally, particularly in small farmlands, the direct application of digestate is becoming difficult due to odor and environmental concerns.

[0005] Methods for treating methane biofermentation digestate from livestock manure, such as that from dairy cows and pigs, include treating it as wastewater and discharging it into public rivers, alternating between aerobic and anaerobic treatment of the methane biofermentation digestate, and using MBR membrane treatment. However, these methods are often costly and unprofitable. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 5818465 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Currently, there is no effective method for treating methane biofermentation digestate other than spreading it on farmland as liquid fertilizer. However, if this practice continues, the nitrogen concentration in the soil and groundwater may increase, potentially threatening the aquatic environment. [Means for solving the problem]

[0008] The inventors of the present invention have conducted extensive research to solve the above problems and have found that, when methane biofermentation digestate is separated into solid and liquid components, compost or bedding material is produced from the solid components, and the filtrate is used as liquid fertilizer, the amount of nitrogen transferred into the liquid fertilizer can be reduced by adding a predetermined polymer flocculant during the solid-liquid separation process. This has led to the completion of the present invention.

[0009] The present invention, which solves the above problems, is described below.

[0010] [1] A method for producing liquid fertilizer from methane biofermentation digestate of livestock manure, characterized in that a cationic polymer flocculant is added to the methane biofermentation digestate, and then solid-liquid separation is performed to remove solid matter from the methane biofermentation digestate, thereby obtaining liquid fertilizer with concentrations of total nitrogen and ammonia nitrogen lower than the concentrations of total nitrogen and ammonia nitrogen in the methane biofermentation digestate.

[0011] The invention described in [1] above is a method for producing liquid fertilizer by separating methane biofermentation digestate into solid and liquid components and removing the solid component, wherein the nitrogen component contained in the methane biofermentation digestate is distributed more to the solid component side, thereby reducing the nitrogen content in the liquid fertilizer. By reducing the nitrogen content in the liquid fertilizer, the impact on the environment can be minimized even when it is sprayed directly onto farmland.

[0012] [2] The method for producing liquid fertilizer according to [1], wherein the total solid content of the methane biofermentation digestate is 1,000 to 100,000 ppm, the total nitrogen content is 2,000 to 9,000 ppm, and the ammoniacal nitrogen content is 1,000 to 6,000 ppm.

[0013] [3] A method for producing liquid fertilizer according to [1] or [2], wherein the total nitrogen content of the liquid fertilizer is 1,000 to 5,000 ppm and the ammoniacal nitrogen content is 1,000 to 4,000 ppm.

[0014] [4] The cationic polymer flocculant is a cationic monomer unit of the following formula (1)

[0015] [ka]

[0016] (However, in the above chemical formula (1), R1 is an alkyl group or benzyl group having 1 to 3 carbon atoms, R2 and R3 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, X is an oxygen atom or NH, Y is a hydrogen atom or a methyl group, Q is an alkylene group having 1 to 4 carbon atoms or a hydroxyalkylene group having 2 to 4 carbon atoms, Z - is a counter anion.) The method for producing a liquid fertilizer according to any one of [1] to [3], comprising a (meth)acrylate monomer represented by .

[0017] [5] The method for producing a liquid fertilizer according to any one of [1] to [4], wherein the cationic polymer flocculant contains, as a nonionic monomer unit, the following formula (2) CH2=CR1-CO-NR2R3 ··· Chemical formula (2) (However, in the above chemical formula (2), R1 is a hydrogen atom or a methyl group, and R2 and R3 are each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.) The method for producing a liquid fertilizer according to any one of [1] to [4], comprising a (meth)acrylamide-based compound represented by .

[0018] [6] The method for producing a liquid fertilizer according to any one of [1] to [5], wherein the cationic polymer flocculant is a mixture of a powder of a copolymer produced by radical polymerization and an inorganic salt, the ratio (molar ratio) of the cationic monomer unit to the nonionic monomer unit in the copolymer is 1 / 99 to 50 / 50, and the copolymer and the inorganic salt are mixed at a mass ratio of 9 / 1 to 1 / 9. The method for producing a liquid fertilizer according to any one of [1] to [5].

[0019] [7] The method for producing a liquid fertilizer according to any one of [1] to [5], wherein the cationic polymer flocculant is a salt water dispersion polymerization type polymer flocculant.

[0020] [8] The method for producing a liquid fertilizer according to any one of [1] to [7], wherein the cationic polymer flocculant is a cationic polymer flocculant having a 0.1 mass% (polymer equivalent) salt viscosity at 25°C of 1.5 to 5.5 mPa·s.

[0021] [9] A method for producing liquid fertilizer according to any one of [1] to [8], wherein the amount of cationic polymer flocculant added is 0.05 to 5% by mass relative to the solid content of the methane biofermentation digestate.

[0022]

[10] Liquid fertilizer manufactured by the manufacturing method described in any of [1] to [9].

[0023]

[11] A method for producing compost and / or bedding from methane biofermentation digestate of livestock manure, characterized in that a cationic polymer flocculant is added to the methane biofermentation digestate, and then solid-liquid separation is performed to remove the liquid from the methane biofermentation digestate, thereby obtaining compost and / or bedding with a concentration of total nitrogen and ammonia nitrogen higher than the concentration of total nitrogen and ammonia nitrogen in the methane biofermentation digestate.

[0024] The invention described in

[11] above is a method for producing compost and / or bedding material by separating the solid and liquid components of methane biofermentation digestate and removing the liquid component, wherein the nitrogen component contained in the methane biofermentation digestate is distributed more to the compost and / or bedding material, thereby reducing the nitrogen component contained in the liquid component obtained as a byproduct. By reducing the nitrogen component contained in the liquid component obtained as a byproduct, the impact on the environment can be reduced even if it is directly applied to farmland as liquid fertilizer.

[0025]

[12] A method for producing compost and / or bedding material according to

[11] , further comprising the step of drying and fermenting the solid components after solid-liquid separation.

[0026]

[13] A method for producing compost and / or bedding material according to

[11] or

[12] , wherein the total solid content of the methane biofermentation digestate is 1,000 to 100,000 ppm, the total nitrogen content is 2,000 to 9,000 ppm, and the ammonia nitrogen content is 1,000 to 6,000 ppm.

[0027]

[14] A method for producing compost and / or bedding material according to any one of

[11] to

[13] , wherein the total nitrogen content of the liquid is 1,000 to 5,000 ppm and the ammoniacal nitrogen content is 1,000 to 4,000 ppm.

[0028]

[15] The cationic polymer flocculant is a cationic monomer unit of the following formula (1)

[0029] [ka]

[0030] (However, in the above chemical formula (1), R1 is an alkyl group having 1 to 3 carbon atoms or a benzyl group, R2 and R3 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, X is an oxygen atom or NH, Y is a hydrogen atom or a methyl group, Q is an alkylene group having 1 to 4 carbon atoms or a hydroxyalkylene group having 2 to 4 carbon atoms, Z - (This is an anti-anion.) A method for producing compost and / or bedding material according to any one of

[11] to

[14] , comprising a (meth)acrylate monomer represented by .

[0031]

[16] The cationic polymer flocculant, as a nonionic monomer unit, is given by the following formula (2) CH2=CR1-CO-NR2R3...(2) (However, in the above chemical formula (2), R1 is a hydrogen atom or a methyl group, and R2 and R3 are each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.) A method for producing compost and / or bedding material according to any one of

[11] to

[14] , comprising a (meth)acrylamide compound represented by .

[0032]

[17] The cationic polymer flocculant is a mixture of a copolymer powder produced by radical polymerization and an inorganic salt, The ratio (molar ratio) of cationic monomer units to nonionic monomer units in the copolymer is 1 / 99 to 50 / 50. A method for producing compost and / or bedding material according to any one of

[11] to

[16] , wherein the copolymer and the inorganic salt are mixed in a mass ratio of 9 / 1 to 1 / 9 to form a cationic polymer flocculant.

[0033]

[18] A method for producing compost and / or bedding material according to any one of

[11] to

[16] , wherein the cationic polymer flocculant is a brine dispersion polymerization type polymer flocculant.

[0034]

[19] A method for producing compost and / or bedding material according to any one of

[11] to

[18] , wherein the cationic polymer flocculant is a cationic polymer flocculant having a 0.1% by mass (polymer equivalent) salt viscosity of 1.5 to 5.5 mPa·s at 25°C.

[0035]

[20] A method for producing compost and / or bedding according to any one of

[11] to

[19] , wherein the amount of cationic polymer flocculant added is 0.05 to 5% by mass relative to the solid content of the methane biofermentation digestate.

[0036]

[21] Compost and / or bedding material produced by the manufacturing method described in any of

[11] to

[20] . [Effects of the Invention]

[0037] According to the present invention, when separating methane biofermentation digestate into solid and liquid components by solid-liquid separation, the nitrogen content in the liquid component can be reduced by distributing a larger proportion of the nitrogen contained in the methane biofermentation digestate to the solid component. Therefore, even when applied in large quantities to farmland as liquid fertilizer, the impact on the environment can be minimized. [Modes for carrying out the invention]

[0038] The present invention will be described in detail below.

[0039] The first aspect of the present invention is a method for producing liquid fertilizer from methane biofermentation digestate of livestock manure. After adding a cationic polymer flocculant to the methane biofermentation digestate, solid-liquid separation is performed to remove solid components from the methane biofermentation digestate, thereby obtaining liquid fertilizer. The concentration of total nitrogen and ammonia nitrogen in this liquid fertilizer is lower than the concentration of total nitrogen and ammonia nitrogen in the methane biofermentation digestate used as the raw material.

[0040] The second aspect of the present invention is a method for producing compost and / or bedding (a general term for rice straw, sawdust, etc., used as bedding for the floor of livestock barns) from methane biofermentation digestate of livestock manure. Compost and / or bedding is obtained by adding a cationic polymer flocculant to the methane biofermentation digestate, and then removing the liquid component from the methane biofermentation digestate by solid-liquid separation. A characteristic feature of this compost and / or bedding is that the concentrations of total nitrogen and ammonia nitrogen are higher than the concentrations of total nitrogen and ammonia nitrogen in the methane biofermentation digestate used as the raw material.

[0041] In other words, the present invention is characterized in that, when separating the methane biofermentation digestate of livestock manure into solid and liquid components, using the liquid component as liquid fertilizer and the solid component as compost and / or bedding material, a large amount of total nitrogen and ammoniacal nitrogen is transferred to the solid component, thereby relatively lowering the total nitrogen and ammoniacal nitrogen in the liquid component.

[0042] (1) Methane biofermentation digestate Methane biofermentation digestate is the liquid substance that remains after methane fermentation treatment of livestock manure, bedding, food waste, etc.

[0043] The total solid content of the digestate (evaporation residue) is the total solid content after drying the digestate. The total solid content of the digestate is preferably 1,000 ppm or more, more preferably 5,000 ppm or more, even more preferably 10,000 ppm or more, and particularly preferably 30,000 ppm or more. Furthermore, the total solid content of the digestate is preferably 100,000 ppm or less, and more preferably 80,000 ppm or less. If it is less than 1,000 ppm, the processing efficiency is low. If it exceeds 100,000 ppm, the reaction with the polymer flocculant becomes insufficient.

[0044] The total nitrogen content of the digestate used as raw material is preferably 2,000 to 9,000 ppm, more preferably 2,500 to 8,000 ppm, and even more preferably 3,000 to 7,000 ppm. If it exceeds 9,000 ppm, the total nitrogen content of the resulting liquid fertilizer will be too high, making it difficult to apply directly to farmland.

[0045] The ammoniacal nitrogen content of the digestate is preferably 1,000 to 6,000 ppm, more preferably 1,200 to 5,000 ppm, and even more preferably 1,400 to 3,500 ppm. If it exceeds 6,000 ppm, the total nitrogen content of the resulting liquid fertilizer becomes too high, making it difficult to apply directly to farmland.

[0046] (2) Cationic polymer flocculants The polymer flocculant used in the present invention is a cationic polymer flocculant. The cationic polymer flocculant is defined as a cationic monomer unit of the following formula (1)

[0047] [ka]

[0048] (However, in the above chemical formula (1), R1 is an alkyl group having 1 to 3 carbon atoms or a benzyl group, R2 and R3 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, X is an oxygen atom or NH, Y is a hydrogen atom or a methyl group, Q is an alkylene group having 1 to 4 carbon atoms or a hydroxyalkylene group having 2 to 4 carbon atoms, Z - (This is an anti-anion.) It is preferable that the cationic polymer flocculant is composed of a copolymer containing monomer units derived from a (meth)acrylate monomer represented by .

[0049] Specific examples of the (meth)acrylate monomer represented by the above chemical formula (1) include dialkylaminoalkyl (meth)acrylates such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, and dimethylamino-2-hydroxypropyl (meth)acrylate, as well as hydrochloride and sulfate salts of dialkylaminoalkyl (meth)acrylamides such as dimethylaminopropyl (meth)acrylamide. Quaternary salts such as alkyl halide adducts such as methyl chloride, benzyl halide adducts such as benzyl chloride, and dialkyl sulfate adducts such as dimethyl sulfate are also examples. These (meth)acrylate monomers may be used alone or in combination of two or more types. Among these preferred (meth)acrylate monomers, the methyl quaternary salt (DAC) of dimethylaminoethyl acrylate is most preferred because it exhibits particularly excellent performance as a polymer flocculant, as well as superior quality and storage stability of the acrylate monomer.

[0050] The copolymer constituting the cationic polymer flocculant used in the present invention preferably contains 1 to 50 mol% of cationic monomer units, more preferably 5 to 35 mol%, and particularly preferably 10 to 30 mol%. If the mole fraction of cationic monomers is outside the above range, it may not match the cation requirement of the digestate, making the dehydration process difficult.

[0051] The copolymer constituting the cationic polymer flocculant used in the present invention is a copolymer of the above-mentioned cationic monomer and a nonionic monomer. The nonionic monomer is not particularly limited, but examples include (meth)acrylamide compounds represented by the following chemical formula (2), alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and hydroxyethyl (meth)acrylate, styrene, acrylonitrile, and vinyl acetate. Among these nonionic monomers, the (meth)acrylamide compounds represented by the following chemical formula (2) are preferred because they exhibit excellent copolymerization with cationic monomers, are easily converted to the high molecular weight necessary for polymer flocculants, and have excellent performance as polymer flocculants.

[0052] CH2=CR1-CO-NR2R3...(2)

[0053] However, in the above chemical formula (2), R1 is a hydrogen atom or a methyl group, and R2 and R3 each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

[0054] Among these (meth)acrylamide compounds, acrylamide (AM) is the most preferred because it is water-soluble and has particularly excellent performance as a polymer flocculant. These nonionic monomers may be used individually or in combination of two or more.

[0055] The copolymer constituting the cationic polymer flocculant used in the present invention preferably contains 50 to 99 mol% nonionic monomer units, more preferably 65 to 95 mol%, and particularly preferably 70 to 90 mol%. If the mole fraction of nonionic monomers is outside the above range, it is difficult to exert an effect on methane biofermentation digestates with a wide range of properties.

[0056] The copolymer constituting the cationic polymer flocculant used in the present invention must contain the aforementioned cationic monomer units and nonionic monomer units, but may contain other monomer units as long as the effects of the present invention are not impaired. Examples of other monomer units include monomer units derived from the following anionic monomers and crosslinkable monomers.

[0057] Examples of anionic monomers include (meth)acrylic acid represented by the following chemical formula (3) and its salts, as well as vinyl sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, maleic acid, and their salts. Among these anionic monomers, (meth)acrylic acid represented by the following chemical formula (3) and its salts are preferred because they exhibit excellent copolymerization with cationic monomers, are easily converted to the high molecular weight necessary for polymer flocculants, and have excellent performance as polymer flocculants. As for salts, ammonium salts and alkali metal salts such as sodium salts and potassium salts are preferred.

[0058] CH2=CR1-CO-OM ... (3)

[0059] However, in the above chemical formula (3), R1 represents a hydrogen atom or a methyl group, and M represents a hydrogen atom, an ammonium group, or an alkali metal atom.

[0060] Among these (meth)acrylic acids and their salts, acrylic acid (AA) and its ammonium salts are most preferred due to their particularly excellent performance as polymer flocculants. These anionic monomers may be used individually or in combination of two or more.

[0061] The copolymer constituting the cationic polymer flocculant used in the present invention preferably contains 0 to 50 mol% anionic monomer units, more preferably 1 to 40 mol%, and particularly preferably 1 to 30 mol%.

[0062] Examples of crosslinkable monomers include (meth)acrylate-based crosslinkable monomers (hereinafter sometimes simply referred to as "crosslinkable monomer" or "crosslinking agent") that have two or more (meth)acryloyl groups represented by the following chemical formula (4) in one molecule.

[0063] CH2=CR1-CO-...(4)

[0064] However, in the above chemical formula (4), R1 is a hydrogen atom or a methyl group, and -CO- represents a carbonyl group.

[0065] The number of (meth)acryloyl groups in one molecule of the crosslinkable monomer is two or more. Preferably, it is 2 to 5 groups, and more preferably 2 to 3 groups. Even if the number of (meth)acryloyl groups in one molecule exceeds 5, the effect of improving performance as a polymer flocculant commensurate with the number of (meth)acryloyl groups may not be obtained.

[0066] Examples of such crosslinkable monomers include alkylene bis(meth)acrylamides, mono and polyalkylene glycol di(meth)acrylates, and polymethylolalkane poly(meth)acrylates, such as methylenebisacrylamide (MBA), ethylene or polyethylene di(meth)acrylate, polypropylene di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. These may be used individually or in combination of two or more.

[0067] The copolymer constituting the cationic polymer flocculant used in the present invention preferably contains 0.0001 to 0.01 mol% of crosslinkable monomer units, more preferably 0.0002 to 0.008 mol%, and particularly preferably 0.0005 to 0.007 mol%. When the content of crosslinkable monomer units is 0.0001 to 0.01 mol%, the interaction between the crosslinked water-soluble polymers is weak, resulting in low viscosity and excellent handling. Furthermore, due to the low viscosity, the reaction with methane biofermentation digestate proceeds rapidly, and strong flocs can be formed. If the content of crosslinkable monomer units exceeds 0.01 mol%, the crosslinking reaction may proceed too far. This is especially true in aqueous solution polymerization, where the amount of insoluble material increases, reducing the amount of active ingredients that effectively act as polymer flocculants, and thus the flocculation effect may not be fully exhibited.

[0068] The copolymer constituting the polymer flocculant used in the present invention is produced by radical polymerization of a monomer mixture containing a cationic monomer, a nonionic monomer, and other monomers as needed. In the present invention, emulsion polymerization is not preferred because it may be difficult to pre-dissolve the resulting polymer at high concentrations.

[0069] The concentration of the monomer mixture is preferably 5 to 50% by mass, and particularly preferably 10 to 30% by mass. The pH of the aqueous solution of the monomer mixture is preferably adjusted to 2 to 5.

[0070] The radical polymerization initiator used in polymerization reactions is not particularly limited. In aqueous polymerization, persulfates such as potassium persulfate and ammonium persulfate, organic peroxides such as t-butyl hydroperoxide, azo-based initiators such as azobisisobutyronitrile, redox initiators, and photopolymerization initiators can be used as appropriate. These radical polymerization initiators may be used alone or in combination of two or more. The amount of photopolymerization initiator added is not particularly limited. It can be adjusted as appropriate depending on the type of photopolymerization initiator, monomer composition, and residual monomer content. In the case of water-soluble azo initiators, it is generally preferable to add 100 to 3000 ppm by mass, relative to the total mass of each monomer in the monomer mixture.

[0071] The polymerization initiation temperature is usually preferably 0 to 35°C. The polymerization time is usually preferably 1 to 16 hours. Furthermore, the polymerization reaction is preferably carried out in an inert atmosphere free of oxygen. These polymerization conditions are well known.

[0072] Chain transfer agents may be used to adjust the molecular weight. The type of chain transfer agent is not particularly limited. Examples of chain transfer agents usable in the present invention include alcohols such as methanol, isopropyl alcohol, ethylene glycol, and propylene glycol; amines such as methylamine and dimethylamine; thiols such as methanethiol and ethanethiol; thiol compounds such as methallyl sulfonic acid, mercaptoethanol, and mercaptopropionic acid; reducing inorganic salts such as sodium sulfite, sodium bisulfite, and sodium hypophosphite; and organic sulfonic acid compounds such as methallyl sulfonic acid. Among these, sodium bisulfite is preferred because it has high solubility in aqueous solutions of monomer mixtures, is highly effective even with small amounts added, and allows for easy adjustment of the molecular weight of the crosslinked water-soluble polymer. These chain transfer agents may be used alone or in combination of two or more.

[0073] The amount of chain transfer agent added is not particularly limited. In the case of sodium bisulfite, it is usually preferable to add 1 to 500 ppm by mass, more preferably 10 to 300 ppm, and most preferably 15 to 200 ppm, relative to the total mass of each monomer in the monomer mixture. If the amount of sodium bisulfite added is less than 1 ppm, the generation of insoluble matter may not be suppressed. In that case, the amount of active ingredient that acts effectively as a polymer flocculant decreases. It may also cause problems such as clogging of the pump that delivers the solution of the polymer flocculant dissolved in water. If the amount of sodium bisulfite added exceeds 500 ppm, the molecular weight of the polymer may become too low. In that case, the flocculation force on the methane biofermentation digestate decreases, and flocculated flocs do not grow. In addition, the filtration rate decreases, fine solid matter in the methane biofermentation digestate leaks into the filtrate, making it difficult to adjust the total nitrogen content and ammoniacal nitrogen.

[0074] The light irradiation conditions, such as the wavelength, intensity, and duration of the light used for photopolymerization, are not particularly limited. They can be appropriately adjusted according to the type and amount of photopolymerization initiator used, as well as the physical properties and performance of the polymer. When using the aforementioned water-soluble azo initiator as the photopolymerization initiator, light with a wavelength of around 365 nm is preferred, and the irradiation intensity should be 0.1 to 10.0 mW / cm using a 365 nm UV irradiometer. 2 This is preferable. The irradiation time is usually preferably 0.1 to 3 hours.

[0075] After the polymerization reaction is complete, post-treatment such as heat treatment, drying, or pulverization may be performed as needed. Known methods can be used for these post-treatments.

[0076] The cationic polymer flocculant used in the present invention may contain other components besides the copolymer described above. Furthermore, pH adjusters such as sulfamic acid, malic acid, adipic acid, and citric acid may be mixed in as needed. Inorganic salts such as ammonium sulfate, sodium sulfate, magnesium sulfate, aluminum sulfate, ammonium hydrogen phosphate, sodium hydrogen phosphate, and potassium hydrogen phosphate may also be mixed in.

[0077] The 0.1% by mass (polymer equivalent) salt viscosity (UL viscosity) of the cationic polymer flocculant used in the present invention at 25°C is preferably 1.5 to 5.5 mPa·s, more preferably 2.0 to 5.0 mPa·s, and even more preferably 1.5 to 4.5 mPa·s. If it is less than 1.5 mPa·s, the flocculation is poor due to the small molecular weight. If it exceeds 5.5 mPa·s, the flocculation is similarly poor because the molecular weight is too large.

[0078] The cationic polymer flocculant used in the present invention may be a mixture of copolymer powder, which is obtained by powdering the copolymer described above, and an inorganic salt. The mixing ratio of copolymer powder to inorganic salt is preferably 9 / 1 to 1 / 9 by mass, more preferably 8 / 2 to 2 / 8, and even more preferably 7 / 3 to 3 / 7. Examples of inorganic salts are those described above. In the present invention, it is undesirable to use copolymer powder without mixing it with an inorganic salt. If it is not mixed with an inorganic salt, the amount of water required to pre-dissolve the polymer flocculant will increase, which may result in a large amount of liquid fertilizer being obtained. Furthermore, if the polymer flocculant is used without pre-dissolving it, flocs may not form, or it may take a long time for them to form, which is undesirable.

[0079] The cationic polymer flocculant used in the present invention is preferably a brine-dispersible polymerization type polymer flocculant. A brine-dispersible polymerization type polymer flocculant is a polymer flocculant that has been radically polymerized in the presence of a dispersant. By using such a brine-dispersible polymerization type polymer flocculant, it can be easily dissolved in water at high concentrations without the presence of inorganic salts. Therefore, the amount of water used when pre-dissolving the polymer flocculant can be reduced, and the amount of liquid fertilizer obtained can be reduced.

[0080] Saltwater dispersion polymerization type polymer flocculants can be produced by known methods. For example, the method disclosed in Japanese Patent Publication No. 62-15251 can be used. That is, a polymer flocculant with a particle size of 100 μm or less can be obtained by stirring in a saltwater solution in the presence of a dispersant made of a polymer soluble in the saltwater solution.

[0081] The inorganic salts constituting the aqueous salt solution are preferably polyvalent anionic salts, and more preferably sulfates or phosphates. Examples of sulfates or phosphates include ammonium sulfate, sodium sulfate, magnesium sulfate, aluminum sulfate, ammonium hydrogen phosphate, sodium hydrogen phosphate, and potassium hydrogen phosphate. The salt concentration in the aqueous salt solution is preferably 15% by mass or higher.

[0082] As a dispersant, either nonionic or ionic polymers can be used. As a dispersant consisting of a nonionic polymer, a complete amidated styrene / maleic anhydride copolymer or a butene / maleic anhydride copolymer can be used. In the present invention, it is preferable to use an ionic polymer. When polymerizing a cationic polymer, it is even more preferable to use a cationic polymer as a dispersant. As the cationic polymer, it is preferable to use a homopolymer of the cationic monomers mentioned above or a copolymer with a nonionic monomer.

[0083] The molecular weight of the dispersant, which is composed of polymers, is preferably 50,000 to 3,000,000, and more preferably 50,000 to 1,500,000, for ionic polymers. For nonionic polymers, it is preferably 10,000 to 1,000,000, and more preferably 10,000 to 500,000. The amount of dispersant added is preferably 1 / 100 to 1 / 10, and more preferably 2 / 100 to 8 / 100, relative to the total amount of monomers.

[0084] (3) Solid-liquid separation operation The solid-liquid separation operation is performed by adding a cationic polymer flocculant to the methane biofermentation digestate described above.

[0085] Cationic polymer flocculants must be dissolved in water beforehand. The dissolution concentration of the cationic polymer flocculant is preferably 0.1 to 10% by mass, more preferably 0.3 to 7.5% by mass, and even more preferably 0.5 to 5% by mass. If the concentration is less than 0.1% by mass, the floc diameter will not be large, or it will take a long time for it to grow. Also, the amount of liquid obtained will increase depending on the amount of water used during the pre-dissolution. On the other hand, it is difficult to pre-dissolve cationic polymer flocculants at concentrations exceeding 10% by mass, and at high concentrations, it may take a long time for them to be added to the methane bio-fermentation digestate and thoroughly mixed.

[0086] The amount of cationic polymer flocculant added is preferably 0.1 to 3.0% by mass relative to the solid content of the digestate, more preferably 0.1 to 2.0% by mass, and even more preferably 0.5 to 1.5% by mass. If the amount is less than 0.1% by mass, floc formation will be insufficient. If the amount exceeds 3.0% by mass, the amount added will be excessive, and even if flocculated flocs are formed, they may not have sufficient dehydration strength.

[0087] As a specific example of the solid-liquid separation method for methane biofermentation digestate of the present invention, a mixture of a powdered polymer flocculant and an inorganic salt, or a brine-dispersible polymer flocculant, is added to the methane biofermentation digestate, and the mixture is stirred and / or mixed by a known method to allow the suspended matter in the digestate to react with the polymer flocculant and form flocculated flocs. The formed flocs of methane biofermentation digestate are mechanically dehydrated by a known means to separate the filtrate from the dehydrated cake.

[0088] While there are no particular limitations on the dewatering equipment, examples include screw press type dewaterers, belt press type dewaterers, filter press type dewaterers, screw decanters, multi-disc dewaterers, and rotary press filters. Considering the need to ensure sufficient reaction time between the methane biodigestate and the polymer flocculant, and the need for a relatively compact design, screw presses and multi-disc dewaterers are optimal.

[0089] The resulting filtrate can be directly applied to farmland as liquid fertilizer.

[0090] The total nitrogen concentration in the filtrate (liquid fertilizer) is preferably 1,000 to 5,000 ppm, and more preferably 1,500 to 3,500 ppm. Furthermore, the total nitrogen concentration in the filtrate (liquid fertilizer) must be lower than the total nitrogen concentration in the digestate used as raw material, preferably 10% or more lower, more preferably 20% or more lower, and even more preferably 30% or more lower.

[0091] The concentration of ammoniacal nitrogen in the filtrate (liquid fertilizer) is preferably 1,000 to 4,000 ppm, and more preferably 1,500 to 3,000 ppm. Furthermore, the concentration of ammoniacal nitrogen in the filtrate (liquid fertilizer) must be lower than the concentration of ammoniacal nitrogen in the digestate used as raw material, preferably 10% or more lower, more preferably 20% or more lower, and even more preferably 30% or more lower.

[0092] (4) Composting and bedding of solid matter The solid portion (dewatered cake) after solid-liquid separation can be converted into compost or bedding material by aerobic fermentation. Aerobic fermentation can be carried out by conventional piling methods, where the dewatered cake is piled up and turned over after the cake temperature rises to 60-70°C, or by agitation methods using rotary tillers, etc. The main method of piling involves storing the cake in a compost shed or aeration-type compost shed and turning it over as needed using loaders, etc. The agitation method involves mixing the cake using agitation equipment such as a rotary tiller instead of turning it over with loaders, etc. In addition, sealed composter systems, compost crane systems, and windrow systems can be used to suppress odor and pests, and are selected as appropriate depending on the situation. It is also possible to use the Quick Composter BC series, a rapid composting system from EYS (Turkey).

[0093] To ensure efficient fermentation, the moisture content of the dehydrated cake may be adjusted during pretreatment. Methods for adjusting the moisture content include evaporation by open-air storage, evaporation by greenhouse drying, moisture reduction by mixing with low-moisture materials such as straw, or the use of a dryer with a heat source such as steam. The appropriate method should be selected depending on the installation location and conditions.

[0094] The total nitrogen concentration in the compost or bedding material is preferably 1,000 to 5,000 ppm, and more preferably 1,500 to 3,500 ppm. Furthermore, the total nitrogen concentration in the compost or bedding material must be higher than the total nitrogen concentration in the digestate used as raw material, preferably 10% or more higher, more preferably 20% or more higher, and even more preferably 30% or more higher.

[0095] The concentration of ammoniacal nitrogen in the compost or bedding material is preferably 1,000 to 4,000 ppm, and more preferably 1,500 to 3,000 ppm. Furthermore, the concentration of ammoniacal nitrogen in the compost or bedding material must be higher than the concentration of ammoniacal nitrogen in the digestate used as raw material, preferably 10% or more higher, more preferably 20% or more higher, and even more preferably 30% or more higher. [Examples]

[0096] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring various physical properties are as follows. Items not listed below were measured in accordance with "JIS K0102 Industrial Wastewater Testing Methods". The temperature condition for measuring various physical properties is 25°C unless otherwise specified.

[0097] [UL viscosity measurement] 300 ml of pure water was weighed into a 500 ml beaker, and while stirring with a stirrer, a polymer equivalent to 0.1% solids was gradually added and dissolved. Then, 17.6 g of NaCl was added and stirred for 5 minutes to dissolve. The solution was filtered through a 250 μm mesh, the liquid temperature was adjusted to 25°C, and the viscosity was measured using an LVTB type viscometer.

[0098] [Flock diameter] The floc diameter was observed visually.

[0099] [Filtration speed] The aggregated methane biofermentation digestate was poured into a stainless steel sieve with an inner diameter of 75 mm, a depth of 100 mm, and a mesh size of 80, and filtered by gravity. A funnel was set up so that the filtrate would enter a 200 mL graduated cylinder, and the volume of the filtrate was measured at 5 seconds, 10 seconds, 20 seconds, and 30 seconds after the addition of the aggregated methane biofermentation digestate to evaluate the gravity filtration efficiency. Of these, the volume of the filtrate after 10 seconds was defined as the filtration rate after 10 seconds (mL).

[0100] [Hand-squeezed] After measuring the filtration rate, the cake was sampled and its consistency was evaluated. Bad: The frock cake leaks out between the fingers during the first hand-piping attempt. Fairly good: The froth cake leaks through the fingers during the second hand-piping attempt. Good: On the third attempt at squeezing by hand, the floc cake did not leak between my fingers, and I was able to squeeze out the filtrate.

[0101] [Measurement of nitrogen content] Total nitrogen and ammoniacal nitrogen were measured by absorbance using the MACHERY-NAGEL PF12PLUS portable water quality analyzer.

[0102] [TS (Total Evaporation Residue), VTS (Variable Tension of Total Evaporates), SS (Suspended Solids), VSS (Variable Tension of Suspended Solids), Fiber (200), Crude Ash, Total Nitrogen, Total Phosphorus, Total Potassium, Total Lime, Total Magnesium] Fiber content was analyzed from the total sample (TS) according to the wastewater testing method. Crude ash, total phosphorus, total potassium, total lime, and total magnesium were analyzed according to the organic matter analysis method for compost, etc. Total nitrogen was analyzed according to the dry combustion method.

[0103] [Total nitrogen recovery rate, ammonia nitrogen recovery rate] The raw digestate water was subjected to solid-liquid separation, and the total nitrogen content was measured in the filtrate. The total nitrogen recovery rate was calculated by subtracting the ratio (%) of the total nitrogen content in the filtrate to the total nitrogen content in the raw digestate water from 100. Ammoniacal nitrogen was measured in the same manner.

[0104] [Manufacturing of brine-dispersible polymer flocculants] <Manufacturing Example 1> In a five-necked separable flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube, 202.6 g of deionized water, 34.6 g of dimethylaminoethyl acrylate methyl chloride homopolymer (20% by mass aqueous solution, molecular weight 1.2 million) (6.0% of monomer) as a dispersant, 125.0 g of ammonium sulfate, 176.4 g of 50% by mass aqueous solution of acrylamide (hereinafter sometimes referred to as "AM"), and 34.0 g of 80% by mass aqueous solution of dimethylaminoethyl acrylate methyl chloride (hereinafter sometimes referred to as "DAC") were charged and completely dissolved. In addition, 0.2 g of isopropyl alcohol was added as a chain transfer agent. The liquid temperature was maintained at 33-35°C, and after purging with nitrogen for 30 minutes, 1.0 g of 1% by mass aqueous solution of 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydride (0.01% of monomer) was added as an initiator to start polymerization. Eight hours after the start of polymerization, 1.0 g of the initiator aqueous solution was added, and polymerization was carried out for another eight hours. The polymer particle size of the resulting dispersion was 10 μm or less, the viscosity was 220 mPa·s, and the UL viscosity was 3.5 mPa·s.

[0105] <Manufacturing example 2, reference manufacturing example 1> The manufacturing process was the same as in Manufacturing Example 1, except that the monomer composition was changed to be as shown in Table 1.

[0106] <Reference production example 2> Into a stainless steel reaction vessel, an aqueous solution of 78% by mass of methyl acrylate dimethylaminoethyl chloride and an aqueous solution of 50% by mass of acrylamide were added, and further distilled water was added to make the total mass 1.0 kg and mixed uniformly. Each monomer had the blending ratio shown in Table 1, and the total concentration of all monomers was 40% by mass. This solution was adjusted to pH = 4, and while nitrogen gas was blown into the solution for 60 minutes, the liquid temperature was adjusted to 5°C. Then, 2,2'-azobis(2-methylpropionamidine) dihydrochloride (hereinafter sometimes referred to as "V-50") and NaHSO3 were added so as to be 1500 ppm and 20 ppm, respectively, in terms of solid content based on the total mass of the monomers. Next, this solution was irradiated with light from above the reaction vessel to carry out polymerization, and a water-containing gel-like polymer was obtained. A 13W black light was used for the light irradiation. The irradiation intensity was 0.4 mW / cm 2 and the irradiation time was 60 minutes. The obtained water-containing gel-like polymer was taken out of the container and shredded. This was dried at a temperature of 80°C for 5 hours and then pulverized to obtain a powdery polymer. Various physical properties of this polymer were measured. The results are shown in Table 1.

[0107] <Reference Production Example 3> It was produced in the same manner as Reference Production Example 2 except that the monomer composition was changed as described in Table 1.

[0108] <Production Example 3> It was produced in the same manner as Reference Production Example 2 except that the monomer composition was changed as described in Table 1. Then, 100 g of ammonium sulfate was mixed with 100 g of the obtained powdery polymer.

[0109] <Reference Production Example 4> DAC, AM, isopropyl alcohol (2.0% by mass relative to monomers) as a chain transfer agent, and distilled water were added to a 1000 ml four-neck separable flask, and the pH was adjusted to 4 with concentrated sulfuric acid. Each monomer was used in the proportions shown in Table 1, and the total concentration of all monomers was 45% by mass. Then, 20 g of aqueous solution containing 0.04 g of V-50 was added, and distilled water was added to make a monomer aqueous solution with a total volume of 400 g. Furthermore, this monomer aqueous solution was added to 155 g of paraffin oil in which 10.0 g of a nonionic surfactant with an HLB of 8.0 was dissolved, and the mixture was emulsified by high-speed stirring for about 1 minute using a homogenizer. Then, a nitrogen gas inlet tube, reflux condenser, and thermometer were attached to the flask, and the stirrer was changed to a normal chemical reaction stirrer, and nitrogen gas was passed through the emulsion for 30 minutes while stirring to degas it. After that, the temperature was raised to 50°C and polymerization was carried out under a nitrogen gas atmosphere. After polymerization was complete, 17.2 g of a nonionic surfactant with an HLB of 13.0 was added to obtain an emulsion-type polymer compound. The results are shown in Table 1.

[0110] <Reference production example 5> Except for changing the monomer composition to be shown in Table 1, the manufacturing process was the same as in Reference Manufacturing Example 4.

[0111] [Table 1]

[0112] [Solid-liquid separation test of methane biofermentation digestate 1] <Examples 1-3, Reference Examples 1-5, Comparative Example 1> A solid-liquid separation test was conducted on methane biofermentation digestate 1 of dairy cow manure. The properties of methane biofermentation digestate 1 are shown in Table 2. Digestive solution 1 in a 300ml plastic beaker 200 After weighing the sample in ml and adding 0.7% by mass of a pre-dissolved polymer flocculant (not dissolved in Reference Example 2 and Comparative Example 1) relative to the solid content of the digestate, the mixture was mixed for 1 minute using a spatula to induce flocculation. The floc diameter, filtration rate in 10 seconds, sludge wringability, total nitrogen content in the filtrate, and ammoniacal nitrogen content in the filtrate were measured after flocculation, and the results are shown in Table 3.

[0113] [Table 2]

[0114] [Table 3]

[0115] Reference Example 1, which used a brine-dispersible polymer flocculant, differed from the polymer flocculant obtained in Production Example 1 in its monomer composition and the low dissolution concentration of the polymer flocculant. As a result, the flocs did not grow large, and the filtration rate and manual squeezing properties were poor. Furthermore, the ammoniacal nitrogen content transferred to the filtrate was not sufficiently reduced. Reference Example 2, which used a brine-dispersible polymer flocculant, did not pre-dissolve the polymer flocculant, resulting in small flocs and poor filtration speed and ease of manual squeezing. Furthermore, the ammoniacal nitrogen content transferred to the filtrate was not sufficiently reduced. Reference examples 3 and 4, which used powdered polymer flocculants, could not achieve a high enough concentration of pre-dissolved polymer flocculant, resulting in small flocs and poor filtration speed and ease of manual squeezing. Reference Example 5, which used an emulsion-type polymer flocculant, failed to achieve a high enough concentration of pre-dissolved polymer flocculant, resulting in small flocs and poor filtration speed and ease of manual squeezing. Comparative Example 1, which used an emulsion-type polymer flocculant, did not form flocs because the polymer flocculant was not dissolved beforehand, making manual squeezing impossible. Furthermore, the total nitrogen content and ammoniacal nitrogen content did not change from those of the methane bio-fermentation digestate 1 used as the raw material. In contrast, in Examples 1 and 2, which used a brine-dispersible polymer flocculant, the polymer flocculant was pre-dissolved at an appropriate concentration, resulting in larger flocs and a sufficiently low content of ammoniacal nitrogen transferred to the filtrate. Furthermore, in Example 3, which used a powdered polymer flocculant with an inorganic salt added, the polymer flocculant could be pre-dissolved at an appropriate concentration, resulting in larger flocs and a sufficiently low content of ammoniacal nitrogen transferred to the filtrate. Furthermore, while the total nitrogen and ammoniacal nitrogen content in the liquid fertilizers obtained in Reference Examples 1-5 is significantly lower than that in the methane bio-fermentation digestate 1 used as the raw material, continuous production may be difficult due to poor manual squeezing properties.

[0116] [Solid-liquid separation test of methane biofermentation digestate 2] <Example 4> A solid-liquid separation test of methane biofermentation digestate 2 from dairy cow manure was conducted using a mini screw press (processing flow rate 30 L / H) manufactured by MT Aquapolymer Co., Ltd. The properties of methane biofermentation digestate 2 (raw digestate water) are shown in Table 4. The brine-dispersible polymer flocculant from Production Example 2 was prepared as a 2.5% by mass aqueous solution. This polymer flocculant aqueous solution was added to the digestate to induce flocculation, and solid-liquid separation was performed using a mini screw press. The addition rate of the polymer flocculant was 0.9% by mass relative to the solid content of the digestate. The physical properties of the filtrate after solid-liquid separation are shown in Table 4.

[0117] <Comparative Example 2> Solid-liquid separation was performed in the same manner as in Example 4, except that a polymer flocculant was not added.

[0118] In Comparative Example 2, solid-liquid separation was performed without chemical injection, resulting in high levels of total nitrogen in the filtrate (4,975 mg / L) and ammoniacal nitrogen (2,765 mg / L). This reduction was only about 10% compared to the total nitrogen and ammoniacal nitrogen levels in the raw digestate water. On the other hand, in Example 4, since flocculation was performed using a dispersed polymer flocculant, the total nitrogen content in the filtrate was reduced to 2,962 mg / L and the ammoniacal nitrogen to 1,995 mg / L.

[0119] [Table 4]

[0120] [Composting test for solid materials] <Example 5> Composting tests were conducted on the solid material of the digestate dehydrated using a mini screw press. 3.0 kg of the solid material (cake) separated in Example 4 was weighed. Next, it was placed in a laboratory-type composting test machine, Kaguya-hime, manufactured by Fujihei Kogyo Co., Ltd., and 1.0 mass% of rice bran was added per cake. Composting was started by aerobic fermentation with air flowing at a wind speed of 1.5 ml / min. After 3 days, the maximum temperature of 60°C was reached, so the cake was turned over, and then turned three more times to complete the composting reaction. The analysis results of the obtained compost are shown in Table 5.

[0121] <Comparative Example 3> Compost was obtained in the same manner as in Example 5, except that the solid material (cake) separated by solid-liquid separation in Comparative Example 2 was used.

[0122] In Comparative Example 3, solid-liquid separation was performed without the use of chemicals, resulting in low concentrations of various components in the compost. On the other hand, in Example 5, since flocculation was performed using a dispersed polymer flocculant, the content of various components in the compost was increased. In addition, the C / N ratio was smaller than in the case without chemical injection. In other words, solid-liquid separation allowed a large amount of nitrogen contained in the digestate to be transferred to the solid material side.

[0123] [Table 5] [Industrial applicability]

[0124] According to the present invention, methane biofermentation digestate made from livestock manure can be effectively utilized. Specifically, when the methane biofermentation digestate is separated into compost and liquid fertilizer, the amount of nitrogen transferred to the liquid fertilizer can be reduced. Therefore, the resulting liquid fertilizer can be directly applied to farmland and other areas for treatment.

Claims

1. A method for producing liquid fertilizer with reduced nitrogen content by adding a cationic polymer flocculant to methane biofermentation digestate of livestock manure, then separating the solids and removing the solids from the methane biofermentation digestate to distribute more nitrogen to the solids, A method for producing liquid fertilizer, characterized in that the concentrations of total nitrogen and ammoniacal nitrogen in the liquid fertilizer are lower than the concentrations of total nitrogen and ammoniacal nitrogen in the methane biofermentation digestate, and the concentration of ammoniacal nitrogen in the liquid fertilizer is 30% or more lower than the concentration of ammoniacal nitrogen in the methane biofermentation digestate.

2. The method for producing liquid fertilizer according to claim 1, wherein the total solid content of the methane biofermentation digestate is 1,000 to 100,000 ppm, the total nitrogen content is 2,000 to 9,000 ppm, and the ammoniacal nitrogen content is 1,000 to 6,000 ppm.

3. A method for producing liquid fertilizer according to claim 1 or 2, wherein the total nitrogen content of the liquid fertilizer is 1,000 to 5,000 ppm, and the ammoniacal nitrogen content is 1,000 to 4,000 ppm.

4. The cationic polymer flocculant, as a cationic monomer unit, is given by the following formula (1) 【Chemistry 1】 (However, in the above chemical formula (1), R １ R is an alkyl group having 1 to 3 carbon atoms or a benzyl group. ２ and R ３ Each is independently a hydrogen atom or a C1-C3 alkyl group, X is an oxygen atom or NH, Y is a hydrogen atom or a methyl group, Q is a C1-C4 alkylene group or a C2-C4 hydroxyalkylene group, Z － (This is an anti-anion.) A method for producing liquid fertilizer according to any one of claims 1 to 3, comprising a (meth)acrylate monomer represented by .

5. The cationic polymer flocculant, as a nonionic monomer unit, is given by the following formula (2) CH ２ =CR １ -CO-NR ２ R ３ ... Chemical reaction (2) (However, in the above chemical formula (2), R １ is a hydrogen atom or a methyl group, and R ２ and R ３ are each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.) A method for producing liquid fertilizer according to any one of claims 1 to 4, comprising a (meth)acrylamide compound represented by .

6. A method for producing liquid fertilizer from methane biofermentation digestate of livestock manure, characterized in that a cationic polymer flocculant is added to the methane biofermentation digestate, and then solid-liquid separation is performed to remove solid matter from the methane biofermentation digestate, thereby obtaining liquid fertilizer with concentrations of total nitrogen and ammonia nitrogen lower than the concentrations of total nitrogen and ammonia nitrogen in the methane biofermentation digestate, The cationic polymer flocculant is a mixture of a copolymer powder produced by radical polymerization and an inorganic salt, The ratio (molar ratio) of cationic monomer units to nonionic monomer units in the copolymer is 1 / 99 to 50 / 50. A method for producing a liquid fertilizer that is a cationic polymer flocculant, comprising a mixture of the copolymer and the inorganic salt in a mass ratio of 9 / 1 to 1 / 9.

7. The method for producing liquid fertilizer according to any one of claims 1 to 5, wherein the cationic polymer flocculant is a brine dispersion polymerization type polymer flocculant.

8. The method for producing liquid fertilizer according to any one of claims 1 to 7, wherein the cationic polymer flocculant is a cationic polymer flocculant having a 0.1% by mass (polymer equivalent) salt viscosity of 1.5 to 5.5 mPa·s at 25°C.

9. The method for producing liquid fertilizer according to any one of claims 1 to 8, wherein the amount of cationic polymer flocculant added is 0.05 to 5% by mass relative to the solid content of the methane biofermentation digestate.

10. A method for producing compost and / or bedding material with increased nitrogen content by adding a cationic polymer flocculant to methane biofermentation digestate of livestock manure, then separating the solid and liquid components to remove the liquid component from the methane biofermentation digestate, thereby distributing more nitrogen to the solid component, A method for producing compost and / or bedding, characterized in that the concentrations of total nitrogen and ammoniacal nitrogen in the compost and / or bedding are higher than the concentrations of total nitrogen and ammoniacal nitrogen in the methane biofermentation digestate, and the concentration of ammoniacal nitrogen in the compost and / or bedding is 30% or more higher than the concentration of ammoniacal nitrogen in the methane biofermentation digestate.

11. A method for producing compost and / or bedding material according to claim 10, further comprising the step of drying and fermenting the solid component after solid-liquid separation.

12. A method for producing compost and / or bedding material according to claim 10 or 11, wherein the total solid content of the methane biofermentation digestate is 1,000 to 100,000 ppm, the total nitrogen content is 2,000 to 9,000 ppm, and the ammonia nitrogen content is 1,000 to 6,000 ppm.

13. A method for producing compost and / or bedding material according to any one of claims 10 to 12, wherein the total nitrogen content of the liquid is 1,000 to 5,000 ppm and the ammoniacal nitrogen content is 1,000 to 4,000 ppm.

14. The cationic polymer flocculant, as a cationic monomer unit, is given by the following formula (1) 【Chemistry 2】 (However, in the above chemical formula (1), R １ R is an alkyl group having 1 to 3 carbon atoms or a benzyl group. ２ and R ３ Each is independently a hydrogen atom or a C1-C3 alkyl group, X is an oxygen atom or NH, Y is a hydrogen atom or a methyl group, Q is a C1-C4 alkylene group or a C2-C4 hydroxyalkylene group, Z － (This is an anti-anion.) A method for producing compost and / or bedding material according to any one of claims 10 to 13, comprising a (meth)acrylate monomer represented by .

15. The cationic polymer flocculant, as a nonionic monomer unit, is given by the following formula (2) CH ２ =CR １ -CO-NR ２ R ３ ... Reaction (2) (However, in the above chemical formula (2), R １ R is a hydrogen atom or a methyl group, ２ and R ３ Each of these is independently either a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. A method for producing compost and / or bedding material according to any one of claims 10 to 14, comprising a (meth)acrylamide compound represented by .

16. A method for producing compost and / or bedding from methane biofermentation digestate of livestock manure, characterized in that a cationic polymer flocculant is added to the methane biofermentation digestate, and then solid-liquid separation is performed to remove the liquid from the methane biofermentation digestate, thereby obtaining compost and / or bedding with a total nitrogen content and ammonia nitrogen content higher than the total nitrogen content and ammonia nitrogen content in the methane biofermentation digestate, The cationic polymer flocculant is a mixture of a copolymer powder produced by radical polymerization and an inorganic salt, The ratio (molar ratio) of cationic monomer units to nonionic monomer units in the copolymer is 1 / 99 to 50 / 50. A method for producing compost and / or bedding material, wherein the copolymer and the inorganic salt are mixed in a mass ratio of 9 / 1 to 1 / 9 to form a cationic polymer flocculant.

17. A method for producing compost and / or bedding material according to any one of claims 10 to 15, wherein the cationic polymer flocculant is a brine-dispersible polymerization type polymer flocculant.

18. A method for producing compost and / or bedding material according to any one of claims 10 to 17, wherein the cationic polymer flocculant is a cationic polymer flocculant having a 0.1% by mass (polymer equivalent) salt viscosity of 1.5 to 5.5 mPa·s at 25°C.

19. A method for producing compost and / or bedding material according to any one of claims 10 to 18, wherein the amount of cationic polymer flocculant added is 0.05 to 5% by mass relative to the solid content of the methane biofermentation digestate.

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