Method of reducing harmful gas emissions from organic fertilizers

Abstract

The invention relates to a method of reducing emissions of harmful gases from organic fertilizers during storage of same, the method comprising the steps of acidifying the organic fertilizer and adding a cyanamide salt composition to the organic fertilizer.

Description

[0001] Methods for reducing harmful gas emissions from farmyard manure

[0002] Description:

[0003] The present invention relates to a method for reducing the emission of harmful gases, such as ammonia, carbon dioxide, nitrous oxide, methane, and hydrogen sulfide, from farm manure during storage. Furthermore, the present invention relates to the use of a calcium cyanamide (CaClSh)-containing composition in acidified farm manure, which suppresses or reduces the emission of these gases during storage.

[0004] In the Federal Republic of Germany, farmyard manure is considered fertilizer and is subject to fertilizer regulations and standards. The application rate and application time of farmyard manure are often regulated by law. In such cases, farmyard manure may not be applied to agricultural land during restricted periods, which, depending on the soil type and crop, can last several months a year. Therefore, farms with livestock are required to maintain sufficient storage space for liquid manure, slurry, liquid manure, stable manure, biogas digestate, and similar materials to ensure the storage of farmyard manure for at least six months.

[0005] Slurry, liquid manure, slurry, stable manure, biogas digestate, and similar materials have always been of great importance to agriculture as farmyard fertilizers. However, due to the concentration of agricultural livestock farming in a limited space, particularly in stables, these farmyard fertilizers are increasingly produced and in concentrated form. The storage of these farmyard fertilizers also poses a multitude of unresolved problems. For example, during storage of farmyard fertilizers, microbial, enzymatic metabolic processes (aerobic and anaerobic decomposition and breakdown) produce environmentally harmful gases such as ammonia (NH3), carbon dioxide (CO2), nitrous oxide (N2O), methane (CH3), or hydrogen sulfide (H2S), sometimes in significant quantities. The majority of methane emitted from farmyard fertilizers comes from the excrement of cattle – and to a lesser extent, pigs.

[0006] A number of technical methods are already available to counteract the emission of harmful gases from farmyard manure. Such measures include, for example, the construction of low-emission open barns, the covering of manure tanks with chopped straw, granules, or floating liners, or, where possible, the direct incorporation of farmyard manure into the soil. Emissions can be further reduced with the help of low-protein multi-phase feeding.

[0007] A significant reduction in the emission of harmful gases during the storage of farmyard manure can be achieved by using closed storage containers and further processing or destroying the gases that accumulate in the containers. However, the equipment required for this is very complex and associated with considerable costs.

[0008] US 2002 / 0121117 A1 and US 2014 / 0311200 A1 describe the use of calcium cyanamide compositions to reduce the emission of unpleasant odors from manure.

[0009] The use of CaCN2 to reduce pollutant emissions during the storage of farm manure is described in WO 2020 / 099321 A1. The pH of the farm manure studied is in the neutral or slightly alkaline range, with the use of calcium cyanamide additionally slightly increasing the pH of the farm manure.

[0010] Furthermore, the acidification of farmyard manure has long been known to reduce gas emissions from farmyard manure (Fangueiro, D. et al. Journal of Environmental Management 2015, 149, 46-56). The control of the unpleasant odor of manure through the use of hydrogen peroxide and the lowering of the pH of the manure with mineral acids is described in US 3,966,450. EP 0 612 704 A1 describes the reduction of the emission of ammonia and carbon dioxide from manure by lowering the pH. A similar process is disclosed in WO 2012 / 031622 A1 to reduce the emission of methane, ammonia and hydrogen sulfide. In order to improve the practical suitability of acidification processes, work is ongoing to optimize them. For example, Dalby FR et al. PLoS One 2022, 17(5):e0267693 and Ma C. et al. ACS Agricultural Science & Technology 2022, 2, 437-442 the use of different acids orThe optimization of acid dosage quantities is being investigated. EP 2 179 978 A2 also describes an upstream acid treatment of manure outside the storage tank to achieve an efficient pH reduction.

[0011] However, after acidification of the manure, the pH value rises again over time (Overmeyer V. et al. Agronomy 2021 , 1 1 , 1319), so that regular pH control and repeated addition of acid to the fertilizer becomes necessary to maintain effective control over gas formation.

[0012] A combination of acidification of the farmyard manure and additional cyanamide salt treatment is not described in the prior art.

[0013] Despite the progress already made in reducing the release of harmful gases from farmyard manure, there is a strong demand for processes that can further reduce gas emissions. The present invention is therefore based on the object of providing a process for reducing gas emissions from farmyard manure during storage, which sustainably reduces the release of a variety of gases, is relatively simple to implement, and, moreover, does not negatively impact the planned use of the farmyard manure as fertilizer in agriculture. Furthermore, the present invention is intended to reduce the effort required for pH control during the storage of acidified farmyard manure.

[0014] These tasks are solved by a combination of acidifying the farmyard manure until the pH value is in the slightly acidic range and adding a cyanamide salt. This significantly and lastingly reduces the emission of harmful gases such as NH3, CO2, N2O and CH4, so that a single application is usually sufficient. In addition, a synergistic effect of both measures is observed, whereby the amount of cyanamide salt required to almost completely prevent gas emissions can be reduced. Even more importantly, however, a relatively mild acidification of the farmyard manure, e.g. to pH 4.5 to pH 6.8, is sufficient, so that the amount of acid is significantly reduced. This is also achieved by treating the farmyard manure with the method according to the invention, which reduces the need for repeated acidification over long periods of time or can eliminate it altogether.Furthermore, the formation and release of H2S can be effectively prevented with the process according to the invention. The emission of H2S is particularly problematic during acidification with sulfur-containing acids, such as H2SO4.

[0015] Thus, a method for reducing the emission of harmful gases from farm manure during its storage is the subject of the present invention, which comprises the following method steps: a) providing a farm manure, and b) acidifying the farm manure until a pH value in the range of pH 4.5 to 6.8 is set, and c) adding 0.01 wt.% to 1.0 wt.%, based on the total weight of the farm manure, of a cyanamide salt composition to the farm manure.

[0016] With the process according to the invention, in addition to the emissions of methane and carbon dioxide, the emissions of ammonia and nitrous oxide can be particularly effectively reduced. Furthermore, the formation and release of toxic hydrogen sulfide is also very effectively prevented, especially compared to pure manure acidification with sulfuric acid. This is particularly relevant for the protection of humans and animals, as accidents caused by H2S still occur, some of which are fatal in rare cases.

[0017] What is particularly surprising is that the combination of adding cyanamide salt to the manure and acidifying the manure has a strong synergistic effect on reducing gas emissions. This synergistic effect is evident both in the emitted gas volumes and in the duration of gas emission inhibition. To prevent unwanted emissions, a single application of the inventive method at the beginning of storage is generally sufficient. The amounts of cyanamide salt and acid used can also be reduced by combining the two measures compared to the respective individual measures.

[0018] According to the present invention, the term farmyard manure includes fertilizers according to Section 2 Paragraph (1), (2), (3), (4) and (5) of the Fertilizer Act (DüngG, of 9 January 2009 (Federal Law Gazette I p. 54, 136), last amended by Article 1 of the Act of 5 May 2017 (Federal Law Gazette I p. 1068)). Thus, farmyard manure according to the present invention is fertilizers which a) are used as animal excreta aa) in the keeping of animals for the production of food or bb) in the keeping of animals in agriculture or b) as plant substances in the context of plant production or in the

[0019] Agriculture, including in mixtures with each other or after aerobic or anaerobic treatment.

[0020] The term “farm manure” therefore also includes

[0021] ■ Solid manure: farmyard manure made from animal excrement, whether or not mixed with bedding, in particular straw, sawdust, peat or other plant material added as part of animal husbandry, or mixed with fodder residues, the dry matter content of which exceeds 15% by weight;

[0022] ■ Manure: Farmyard manure made from all animal excrement, including small amounts of bedding or feed residues or the addition of water, with a dry matter content not exceeding 15% by weight. Manure generally has a dry matter content of at least 1% by weight. Manure preferably contains a solids content in the range of 3 to 12% by weight.

[0023] ■ Liquid manure: farmyard manure made from animal excrement, which is a mixture of manure and washed-out fine components of the excrement or bedding, as well as water; liquid manure may contain small amounts of feed residues, as well as cleaning and rainwater; biogas digestate: farmyard manure made from residues resulting from the fermentation of organic materials of both plant and animal origin in biogas plants.

[0024] The process according to the invention is particularly well suited for reducing gas emissions from liquid farm manures and in particular from liquid manure, slurry and / or biogas digestate, which preferably have a dry matter content of not more than 15 wt.%.

[0025] Untreated farm manure typically has a pH in the neutral or slightly alkaline range. Due to their manufacturing process, commercially available calcium cyanamide products often contain a certain proportion of calcium oxide or calcium hydroxide. When these products are used to reduce emissions, the pH of the farm manure is shifted slightly to higher pH values. To prevent emissions, maintaining a slightly acidic pH in the range of 4.5 to 6.8 in farm manure has proven beneficial. In many cases, even a pH in the range of 5.0 to 6.5 is sufficient to achieve the desired reduction in gas emissions. A particularly preferred pH range is between 4.8 and 6.3, and in particular between 5.0 and 6.0.

[0026] In principle, all acids or acidic compounds (e.g. CO2 or acidic salts (Al2(SO4)3, KHSO4, FeCl2, etc.) and microorganisms (e.g. acid-forming bacteria) can be used for acidification. Preferred acids are selected from the group of inorganic acids (mineral acids) sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, silicic acid and organic acids, such as formic acid, acetic acid, lactic acid, oxalic acid, citric acid, fumaric acid, benzoic acid and maleic acid, with the use of sulfuric acid, hydrochloric acid, acetic acid, citric acid or lactic acid being particularly preferred.

[0027] To achieve the most effective reduction in the emission of harmful gases from farmyard manure, in addition to acidification, the fertilizer must be treated with a cyanamide salt. Whether the pH is adjusted first, the treatment with cyanamide salt first, or both simultaneously is irrelevant. However, it is advantageous if the acidification takes place after the cyanamide treatment. In principle, the addition of the cyanamide salt composition according to process step c) can take place before, during, or after the first filling of the storage facility with farmyard manure. If the addition takes place before the first filling, the cyanamide salt should be added no earlier than one day before the storage facility is filled with farmyard manure. The acid can also be added, at least in part, in the storage facility.However, since the pH adjustment is made much easier if the acid is added during or after filling the storage facility with farmyard manure, these variants are preferred.

[0028] Suitable cyanamide salts include calcium cyanamide and magnesium cyanamide, as well as the corresponding alkali metal salts, such as sodium cyanamide and potassium cyanamide. Suitable cyanamide salts also include salts of cyanamide derivatives, such as acylcyanamide salts, especially acetylcyanamide salts.

[0029] Suitable acylcyanamide salts are in particular compounds of the formula [R-(C=O)-N'CN]M +, where R represents an alkyl radical having 1 to 8 C atoms, especially 1-4 C atoms, and M represents Na, K, Ca, or Mg. Salts of cyanamide ('N=C=N') itself are preferably used. The use of calcium cyanamide ("calcium cyanamide") is very advantageous, as the salt has been used as a fertilizer active ingredient for many decades. Calcium cyanamide is used as a soil fertilizer for a variety of crops, such as corn, potatoes, and rice.

[0030] During the production of cyanamide salts, a composition is usually obtained which contains some by-products. For example, a calcium cyanamide composition often comprises other ingredients, such as calcium hydroxide or elemental carbon. Since the production-related by-products are harmless, purification is not necessary for the purposes of the present invention. Consequently, compositions comprising cyanamide salts can also be used to reduce gas emissions from farmyard manure during its storage. Such compositions can also contain other additives, such as fillers, carrier materials, granulation aids, nitrification inhibitors, dyes, pigments, etc. The cyanamide salt can, for example, be applied to a carrier material. This carrier material can be an agriculturally inert material, an adjuvant approved for agricultural purposes, or a fertilizer.According to the present invention, carbonates, such as calcium carbonate, magnesium carbonate, magnesium bicarbonate, calcium bicarbonate, and / or mineral fertilizers, are particularly preferred as carrier materials. These carrier materials can originate from large-scale industrial processes and contain a proportion of free carbon, coal, or graphite.

[0031] In the process described here, particularly preferred cyanamide salt compositions are used which comprise a) cyanamide salt, in particular calcium cyanamide, b) optionally at least one compound from the group of carbonates, in particular from the group of magnesium carbonate, magnesium bicarbonate, calcium carbonate, calcium bicarbonate, or mixtures thereof, and c) more preferably optionally free carbon, coal or graphite.

[0032] Preference is given to using compositions which contain 10 to 100% by weight of at least one cyanamide salt, in particular calcium cyanamide, based on the total weight of the composition. Particular preference is given to a composition containing at least 20% by weight, more preferably at least 25% by weight, more preferably at least 30% by weight, more preferably at least 35% by weight, more preferably at least 40% by weight, more preferably at least 45% by weight, more preferably at least 50% by weight, and up to 100% by weight, in particular up to 95% by weight, in particular up to 80% by weight, in particular up to 55% by weight, of cyanamide salt, based on the total weight of the composition.

[0033] The proportions of the other ingredients or carrier materials can vary. The proportion of carbonates, in particular selected from the group consisting of magnesium carbonate, magnesium bicarbonate, calcium carbonate, and calcium bicarbonate, or mixtures thereof, is preferably at least 1% by weight, more preferably at least 5% by weight, particularly preferably at least 10% by weight, and at the same time at most 50% by weight, in particular at most 40% by weight, in particular at most 30% by weight, and particularly preferably at most 25% by weight, wherein the weight percentages are based on the total weight of the cyanamide salt composition.

[0034] The proportion of free carbon, coal, or graphite in the composition can preferably be up to 25 wt.%. However, the proportion is in particular between 1 and 20 wt.% and particularly preferably between 5 and 15 wt.%, based on the total weight of the cyanamide salt composition.

[0035] Furthermore, the composition may comprise up to 20 wt.% water, based on the total weight of the cyanamide salt composition, depending on the manufacturing process. However, the cyanamide salt composition preferably contains less than 15 wt.%, in particular between 1 and 10 wt.% water.

[0036] Cyanamide salt compositions with a low hydroxide content, such as calcium or magnesium hydroxide, or hydroxide-free compositions are advantageous because they reduce the amount of acid required to acidify the manure. Since many oxides, such as calcium oxide and magnesium oxide, are converted to the corresponding hydroxides during slaking, it is also advantageous to keep the content of these substances in the compositions low or eliminate them entirely.

[0037] The production-related proportions of oxides or hydroxides, particularly from the group consisting of magnesium oxide, magnesium hydroxide, calcium oxide, and calcium hydroxide, or mixtures thereof, are often 1 wt.% or more and should preferably be below 25 wt.%, particularly preferably below 20 wt.%, with the wt.% figures being based on the total weight of the cyanamide salt composition. Since a corresponding purification of the cyanamide salt compositions would often be too costly, such amounts can be tolerated in the composition.

[0038] Particularly preferred is therefore the use of a composition containing a) 25 to 95 wt.% cyanamide salt, in particular calcium cyanamide, and b) 1 to 20 wt.% free carbon, coal or graphite, wherein the wt.% data are in each case based on the total weight of the cyanamide salt composition.

[0039] Further preferred is the use of cyanamide salt compositions which contain a) 25 to 95% by weight of cyanamide salt, in particular calcium cyanamide, b) up to 15% by weight of free carbon, coal or graphite, c) 1 to 40% by weight of at least one compound from the group of carbonates, in particular from the group of magnesium carbonate, magnesium bicarbonate, calcium carbonate, calcium bicarbonate or mixtures thereof, d) less than 20% by weight of oxides and hydroxides, in particular from the group of magnesium oxide, magnesium hydroxide, calcium oxide and calcium hydroxide or mixtures thereof; e) up to 15% by weight of water, in each case based on the total weight of the cyanamide salt composition.

[0040] If the cyanamide salt composition is to be used as granules, a granulation aid, e.g. from the group of nitrates, in particular selected from the group consisting of calcium nitrate, sodium nitrate, potassium nitrate, magnesium nitrate, or mixtures thereof, can be present in a preferred amount of between 0.1 wt.% and 10 wt.%, based on the total weight of the cyanamide salt composition. The nitrate content is particularly preferably below 10 wt.%, better below 5 wt.% or below 2 wt.%, and in particular in a range from 0.3 to 1 wt.%.

[0041] Consequently, cyanamide salt compositions are further preferred which contain a) 25 to 95 wt.% cyanamide salt, in particular calcium cyanamide, b) up to 15 wt.% free carbon, coal or graphite, c) 1 to 30 wt.% at least one compound from the group of carbonates, in particular from the group of magnesium carbonate, magnesium bicarbonate, calcium carbonate, calcium bicarbonate or mixtures thereof, d) less than 20 wt.% oxides and hydroxides, in particular from the group of magnesium oxide, magnesium hydroxide, calcium oxide and calcium hydroxide or mixtures thereof; e) up to 15 wt.% water, f) up to 10 wt.% nitrates, in each case based on the total weight of the cyanamide salt composition.

[0042] Particularly preferred cyanamide salt compositions contain: a) 50 to 80 wt.% cyanamide salt, in particular calcium cyanamide, b) up to 15 wt.% free carbon, coal or graphite, c) 1 to 25 wt.% of at least one compound from the group of carbonates, in particular from the group magnesium carbonate, magnesium bicarbonate, calcium carbonate, calcium bicarbonate or mixtures thereof, d) less than 15 wt.% oxides and hydroxides, in particular from the group magnesium oxide, magnesium hydroxide, calcium oxide and calcium hydroxide or mixtures thereof; e) up to 15 wt.% water, f) up to 5 wt.% nitrates, in each case based on the total weight of the cyanamide salt composition.

[0043] An alternative, particularly preferred embodiment of the cyanamide salt composition contains: a) 35 to 55 wt.% cyanamide salt, in particular calcium cyanamide, b) 5 to 15 wt.% free carbon, coal, or graphite, c) 5 to 30 wt.% of at least one compound from the group of carbonates, in particular from the group of magnesium carbonate, magnesium bicarbonate, calcium carbonate, calcium bicarbonate, or mixtures thereof, d) 1 to 20 wt.% oxides and hydroxides, in particular from the group of magnesium oxide, magnesium hydroxide, calcium oxide, and calcium hydroxide, or mixtures thereof; e) 1 to 15 wt.% water, f) 0.1 to 5 wt.% nitrates, each based on the total weight of the cyanamide salt composition. The cyanamide salt compositions can be used in the form of a solid, in particular in the form of a powder, a granulate, or in the form of a suspension, in particular a suspension of these solids.The acid can be mixed with the cyanamide salt composition or applied separately.

[0044] According to the present invention, 0.01 wt.% to 1.0 wt.%, preferably 0.05 wt.% to 0.8 wt.%, in particular 0.07 wt.% to 0.7 wt.%, based on the total weight of the farm manure, of a cyanamide salt composition is added to the farm manure. It is particularly advantageous if the cyanamide salt composition is added in an amount such that the cyanamide salt is present in an amount of 0.01 to 1.0 wt.%, preferably in a proportion of 0.03 wt.% to 0.8 wt.%, particularly preferably of 0.05 wt.% to 0.6 wt.% and in particular of 0.06 wt.% to 0.4 wt.%, based on the total weight of the farm manure.

[0045] To carry out the described process, it is advantageous if the farmyard manure is stored in a closed storage facility. A closed storage facility refers to devices that allow anaerobic storage or at least partially anaerobic storage. Such storage facilities can be storage tanks, storage basins, or pits that can be mechanically closed. This can be achieved, for example, by a tent roof or a concrete ceiling. However, oxygen exclusion can also be achieved by an aqueous phase or an aqueous supernatant on the surface of the farmyard manure. The disclosed process can also be useful in open storage facilities or storage containers that have no cover or cannot be closed. To accelerate or improve the effect of the process, sufficient mixing of the cyanamide salt composition with the farmyard manure should be ensured.

[0046] It should be emphasized at this point that the method according to the invention can be carried out in an unlimited number of deposits. The size of the deposit is not critical. Thus, the volume X can be any reasonable size. In particular, X means a volume measured in [m 3 ], which is between 0.001 m 3 < X < 20,000 m 3 , preferably between 0.1 m 3 < X < 10,000 m 3 and more preferably between 1 m 3 < X < 10,000 m 3 and particularly preferably between 10 m 3 < X < 10,000 m 3 lies.

[0047] Furthermore, the described process is characterized by the fact that the addition of the cyanamide salt composition and the acidification of the farmyard manure in the storage areas can be carried out easily at a manure temperature in the range of 0 °C to 60 °C. The process is therefore applicable in both winter and midsummer conditions. In particular, farmyard manure that originates directly from a fermentation process or is in a post-fermentation tank or storage vessel after a biogas process can be treated with the described process.

[0048] It is advantageous if, during or after acidification or the addition of the cyanamide salt composition to the farmyard manure in the deposit, the manure is circulated using a propeller mixer or a stirring pump. The deposit can be partially or completely filled. Preferably, the deposit should be filled with farmyard manure to a content of at least 5 vol.%. In a preferred process variant, at least 5 vol.% of the farmyard manure, based on the volume of the deposit, is initially introduced, and the cyanamide salt composition is added and stirred in. Acidification can take place before, after, and / or simultaneously with the addition of the cyanamide salt. Subsequently, another addition of farmyard manure can take place. After this addition is complete, the farmyard manure is circulated again in the deposit.

[0049] Particularly in the case of multiple or continuous inflow of farmyard manure into the storage facility, multiple treatments with the method according to the invention can also be advantageous. However, a single treatment with the method according to the invention is generally sufficient, provided that sufficient acidification occurs and a sufficient amount of cyanamide salt is made available with the treatment. Since gas emissions from the farmyard manure generally only develop after a few days, the treatment of the farmyard manure with the method according to the invention can also be carried out with a corresponding time delay before the storage facility is filled. This is particularly possible when the storage facility is being completely refilled. However, treating the farmyard manure close to the storage facility is preferred, especially if farmyard manure residues that have been stored for a long time are already present in the storage facility.

[0050] Propeller mixers driven by a tractor or an electric motor are suitable for circulating the manure in the storage facility. Propeller mixers permanently installed in the storage wall or built-in mixers with submersible motors, as well as tractor-mounted swivel, articulated, and tower propeller mixers, which are immersed in storage tanks containing manure, have proven particularly suitable. Furthermore, agitator nozzles attached to feed pumps are suitable for circulating the manure in the storage facility, particularly long-shaft agitator pumps with agitator nozzles driven by an electric motor or tractor, or centrifugal pumps with a ripper.

[0051] According to a preferred embodiment of the method, the addition of the cyanamide salt composition and / or the acidification of the farmyard manure can be carried out once or in portions. Particularly preferably, the addition of the composition or the acidification can be carried out i) once after or during the filling of the deposit with a first portion of farmyard manure, or ii) in portions after each partial filling of the deposit, or iii) once after or during the complete filling of the deposit with farmyard manure.

[0052] The process according to the invention can also be designed in such a way that the addition of the cyanamide salt composition or the acidification takes place in portions before, during and after a continuous or portion-wise filling of the deposit with farmyard manure.

[0053] Livestock farming often continuously produces farmyard manure, which is collected in the storage facility. Here, too, it is possible to apply the method according to the invention during or after the continuous filling with farmyard manure. The exposure time of the cyanamide salt composition in the acidified farmyard manure is preferably at least 24 hours, particularly preferably more than 30 days, especially > 50 days. However, the storage time can also be significantly longer, for example, up to one year or, if desired, even longer.

[0054] The treatment of the farm manure using the method according to the invention can also begin some time after the storage facility has been filled with the farm manure. Fresh farm manure is often characterized by the fact that the majority of gas emissions only occur after storage of 30 to 60 days. Therefore, the treatment of the farm manure should preferably take place beforehand. With the method according to the invention, a single treatment of the farm manure is generally sufficient to almost completely prevent gas emissions during storage for at least 6 months, and generally even for at least 9 months or over a year. Longer storage of the farm manure is not usually required in practice. Even with repeated treatment of the farm manure, gas emissions are permanently reduced.

[0055] By means of the process according to the invention, at least 30%, more preferably at least 40%, more preferably at least 50%, more preferably at least 60%, even more preferably at least 70% and particularly preferably at least 80% of the ammonia, carbon dioxide, nitrous oxide, methane and hydrogen sulphide emissions from farm manure can be avoided in comparison to untreated farm manure.

[0056] Thus, the use of a composition comprising cyanamide salt for reducing the emission of ammonia, carbon dioxide, nitrous oxide, methane and hydrogen sulphide from acidified farmyard manure during its storage is also the subject of the present invention.

[0057] Furthermore, the addition of the cyanamide salt composition and the acidification can be carried out even after extended storage of the manure, since significant gas evolution in the manure only begins after some time. It has been shown that even adding the cyanamide salt composition after several weeks of storage of the manure enables a reduction in gas emissions. Thus, the method according to the invention is also suitable for stopping or inhibiting the microbial, enzymatic conversion of organic substrates in manure during storage.

[0058] The total amount of cyanamide salt to be applied can be varied within relatively wide limits. It has been shown that a quantity of 0.5 to 10 kg per 1 m 3 based on the total amount of farmyard manure, in particular from 0.6 to 10 kg per 1 m 3 or from 1.0 to 10 kg per 1 m 3 , especially from 0.7 to 8 kg per 1 m 3or from 1.0 to 8 kg per 1 m 3 , particularly preferably from 0.8 to 6 kg per 1 m 3 or from 1.0 to 6 kg per 1 m 3 and most preferably from 1.0 to 5 kg or from 1.0 to 4 kg per 1 m 3 can be used and, in combination with acidification of the farmyard manure to pH 4.5 to 6.8, is sufficient to significantly reduce the emission of harmful gases. The specified quantities are particularly suitable for eliminating gas emissions from relatively liquid farmyard manure, such as liquid manure, slurry, or biogas digestate.

[0059] The amount of cyanamide salt required to effectively reduce gas emissions from farm manure depends primarily on the composition and solids content of the manure. A high solids content generally favors the addition of larger amounts of cyanamide salt. Conversely, a low solids content favors the use of smaller amounts of cyanamide salt.

[0060] Of particular importance is that manure treated in this way also does not experience any significant changes in its nitrogen content. The additional amount of nitrogen applied can be further reduced with the process described here, even compared to the process described in WO 2020 / 099321 A1.

[0061] Thus, the total amount of farmyard manure to be applied per hectare can remain essentially constant. This allows farmyard manure and commonly used nitrogen fertilizers, which have a different effect profile than farmyard manure, to be applied in unchanged amounts throughout the year without fear of overfertilization. Thus, the application of a cyanamide salt-containing composition incorporated into farmyard manure according to the present invention also clearly distinguishes itself from conventional fertilization with calcium cyanamide-containing fertilizers in terms of the total nitrogen applied.

[0062] Short description of the characters:

[0063] Figures 1 to 4 show the temporal progression of total gas emissions, CH4 emissions, CO2 emissions, and FhS emissions of untreated cattle manure and cattle manure after acidification and CaCN2 treatment. Figures 5 to 8 show the temporal progression of total gas emissions, CH4 emissions, CO2 emissions, and FhS emissions of acidified cattle manure and cattle manure after acidification and CaCN2 treatment. Figures 9 to 12 show the temporal progression of total gas emissions, CH4 emissions, CO2 emissions, and FhS emissions of cattle manure treated with calcium cyanamide and cattle manure after acidification and CaCN2 treatment. Figures 13 to 18 show the time course of total gas emissions, CFU emissions, CO2 emissions, FhS emissions, NH3 emissions and IShO emissions of untreated cattle slurry compared to cattle slurry after acidification and CaCN2 treatment.Figures 19 to 24 show the temporal progression of total gas emissions, CFU emissions, CO2 emissions, FhS emissions, NH3 emissions, and IShO emissions from acidified cattle manure compared to cattle manure after acidification and CaCN2 treatment. Figures 25 to 30 show the temporal progression of total gas emissions, CFU emissions, CO2 emissions, FhS emissions, NH3 emissions, and IShO emissions from cattle manure treated with calcium cyanamide compared to cattle manure after acidification and CaCN2 treatment.

[0064] Examples of implementation:

[0065] To determine gas emissions during the storage of farmyard manure, two series of experiments were conducted with cattle manure. Experimental variants with different acids, with and without CaCN2 treatment, were investigated. 1 . Materials and Methods

[0066] 1.1 Cattle manure:

[0067] Fresh cattle manure (farm manure) was obtained from a dairy farm in Bavaria. The cattle manure was neither diluted with rinsing or cleaning water, nor contaminated with bedding. The cattle manure was taken from the antechamber of the drainage channel toward the manure pit.

[0068] The analysis of the untreated cattle manure for the two test series yielded the following values:

[0069] Table 1 : Characteristics of the cattle manure used.

[0070] 1 .2 Acidification of cattle manure:

[0071] To acidify the cattle manure, 80 or 95% sulfuric acid (H2SO4), 32% hydrochloric acid (HCl), 100% acetic acid (HOAc), 50% citric acid (CA), or 90% lactic acid (LA; racemate of D- and L-lactic acid) were used. The cattle manure was mixed with the respective acid while stirring and adjusted to the desired pH value (pH 6.0 or pH 5.5). The pH values ​​were measured using a SevenGo Duo pH / Cond meter SG23 from Mettler Toledo.

[0072] 1 .3 Composition of the CaCN2 formulations (F1 & F2):

[0073] To reduce pollutant emissions during the storage of farmyard manure, two formulations containing calcium cyanamide (CaCISh) were used. The CaCN2 formulations (F1 & F2) used in the examples were composed as follows: Table 2: Composition of CaCN2 formulations F1 and F2.

[0074] The CaCN2-containing composition F1 has a total nitrogen content of 18.5% and a cyanamide nitrogen content of 16.1%. The CaCN2-containing composition F2 has a total nitrogen content of 18.3% and a cyanamide nitrogen content of 15.3%.

[0075] 1 .4 General test procedure:

[0076] In a 6-litre wide-necked container made of polyethylene (PE) with a tightly closing lid, a defined quantity of cattle slurry (farm manure) as per 1.1 is either untreated or treated with one of the listed acids to a pH value of 6.0 or

[0077] 5.5. Subsequently, in some examples, a defined amount of the composition F1 or F2, and thus of CaCN2, is added and stirred in. More detailed information on the application rates of the farmyard manure and the additives in the various examples and comparative examples is shown in Table 3. After all substances have been added and stirred in, the 6-liter wide-neck container is tightly closed. To collect the emitted gases during anaerobic storage, a gas-tight opening is incorporated into the lid of the wide-neck container, to which a gas storage bag (nominal volume 5.6 liters) is connected, preventing atmospheric oxygen from penetrating the wide-neck container. The respective mixture is stored for a defined period at a temperature of 23 ± 1 °C.The filled gas storage bag is changed at regular intervals, the collected gas volume is determined volumetrically, and the gas composition is analyzed using a biogas measuring device (Optima 7 from MRU Messgeräte für Rauchgase und Umweltschutz GmbH) and a photoacoustic infrared spectrometer (Innova 1512 from Luma Sense Technologies). Table 3: Test series on gas release during anaerobic storage of cattle manure.

[0078] 2. Determination of gas emissions

[0079] 2.1 Test series 1

[0080] 2.1.1 Comparative Example V1 (Control): As a reference for the gas quantities emitted during anaerobic storage of treated farmyard manure, 3.05 kg of untreated cattle manure without additives was analyzed (control experiment V1 according to Table 3). The gas storage bags were changed and analyzed after 14, 67, 78, 85, 95, 108, 115, 136, 156, 179, 218, 248, 267, 295, 357, and 400 days. The total gas volume emitted

[0081] (Vtotal) and the specific volumes of methane (CH), carbon dioxide (CO2), and hydrogen sulfide (H2S) are listed cumulatively in Table 4. For better comparability, the gas quantities determined are standardized to 1.00 kg of cattle manure. The temporal progression of the respective gas evolutions is shown in Figures 1 to 4.

[0082] Table 4: Cumulative gas emissions per 1.00 kg of cattle slurry in litres or millilitres.

[0083] 2.1.2 Combination of acidification and CaCN2 treatment of cattle manure (B1 and B2): According to Example B1 (Table 3), 3.02 kg of cattle manure was adjusted to a pH of 6.0 with 24.5 g of 80% H2SO4. Subsequently, 6.33 g of CaCN2 formulation F1 were added and stirred in. According to Example B2 (Table 3), 3.00 kg of cattle manure was adjusted to a pH of 5.5 with 31.2 g of 80% H2SO4. Subsequently, 6.31 g of CaCN2 formulation F1 were added and stirred in. The exchange and analysis of the gas storage bags were carried out for both examples after 14, 67, 85, 108, 136, 156, 179, 218, 248, 267, 295, 357, and 400 days. The total gas volumes emitted (V ges) and the specific volumes of methane (CH4), carbon dioxide (CO2), and hydrogen sulfide (H2S) are listed cumulatively in Table 5. For better comparability, the gas quantities determined are standardized to 1.00 kg of cattle manure. The temporal progression of the respective gas evolutions is shown in Figures 1 to 4.

[0084] Table 5: Cumulative gas emissions based on 1.00 kg of cattle manure in litres or millilitres. Discussion of the results:

[0085] Total emissions: After 400 days of anaerobic storage, 15.5 L of total gas were released per 1.00 kg of cattle manure in the reference experiment (V1). By acidifying with 80% H2SO4 to pH 6.0 and subsequently adding CaCN2 (Example 1), emissions can be reduced by 82.1% to 2.77 L. An even more effective reduction was achieved by acidifying with 80% H2SO4 to pH 5.5 and subsequently adding CaCN2 (Example 2). Compared to the reference experiment (V1), total emissions were reduced by 89.1% to 1.69 L.

[0086] CH4 emissions: After 400 days of anaerobic storage, 5.24 L of CH4 were released per 1 kg of cattle manure in the reference experiment (V1). By acidifying to pH 6.0 and subsequently adding CaCN2 (Example 1), emissions could be reduced by 93.9% to 0.32 L. An even more effective reduction was achieved by acidifying to pH 5.5 and subsequently adding CaCN2 (Example 2). Compared to the reference experiment (V1), CH4 emissions could be reduced by 97.1% to 0.15 L.

[0087] CO2 emissions: After 400 days of anaerobic storage, 3.51 L of CO2 were released per 1 kg of cattle manure in the reference experiment (V1). By acidifying to pH 6.0 and subsequently adding CaCN2 (Example 1), emissions could be reduced by 94.9% to 0.18 L. An even more effective reduction was achieved by acidifying to pH 5.5 and subsequently adding CaCN2 (Example 2). Compared to the reference experiment (V1), CO2 emissions could be reduced by 98.0% to 0.07 L.

[0088] H2S emissions: After 400 days of anaerobic storage, 3.61 mL of H2S were released per 1.00 kg of cattle manure in the reference experiment (V1). Acidification to pH 6.0 and subsequent addition of CaCN2 (Example 1) increased emissions by 35.7% to 4.90 mL. However, an effective reduction was achieved by acidification to pH 5.5 and subsequent addition of CaCN2. Compared to the reference experiment, H2S emissions were reduced by 71.2% to 1.04 mL. The combination of manure acidification with H2SO4 and subsequent CaCN2 treatment thus represents a very effective measure for reducing pollutant gas emissions, especially methane and carbon dioxide, during the storage of farmyard manure, such as cattle manure. Compared to the control experiment (V1) with untreated cattle manure, almost no pollutant gas emissions were detected over a period of 400 days.A lower pH value of 5.5 at the beginning of storage results in a 39.0% reduction in total emissions compared to the total emissions at pH 6.0. The reduction in harmful CH4, CO2, and H2S emissions by 53.1%, 61.1%, and 78.8%, respectively, is even higher.

[0089] An increased potential can only be observed with regard to the formation and release of H2S, which is due to acidification with H2SO4. This results in additional sulfate (SO4 2- ) for desulfurization (microbial degradation of SO4 2-by sulfate-reducing bacteria / archaea). The influence of pH and increased sulfate concentration can be further illustrated by comparing the two variants of the combination of manure acidification and subsequent CaCN2 treatment. Despite a slightly increased sulfate input in Example 2, the combination of low pH and CaCN2 treatment can also significantly reduce H2S emissions. This is also demonstrated by comparative examples V2 and V3.

[0090] 2.1.3 Acidification of cattle manure with H2SO4 (comparative examples V2 and V3):

[0091] 3.01 kg of cattle manure was adjusted to a pH of 6.0 with 24.4 g of 80% H2SO4 (Comparative Example V2). In Comparative Example 3, 3.00 kg of cattle manure was adjusted to a pH of 5.5 with 31.2 g of 80% H2SO4. The gas storage bags were changed and analyzed in both comparative examples after 14, 67, 85, 95, 108, 136, 156, 179, 218, 248, 267, 295, 323, 357, and 400 days. The total gas volumes emitted (V ges ) and the specific volumes of methane (CH4), carbon dioxide (CO2) and hydrogen sulfide (H2S) are listed cumulatively in Table 6. For better comparability, the gas quantities determined are standardized to 1.00 kg of cattle manure. The temporal course of the respective gas developments is shown in Figures 5 to 8. Table 6: Cumulative gas emissions V2 and V3 (based on 1.00 kg of cattle manure).

[0092] Discussion of the results: Total emissions: After 400 days of anaerobic storage, 10.3 L of total gas were released in comparison example 2 based on 1.00 kg of cattle manure. By adding CaCN2 (example 1), emissions were reduced to 2.77 L, or 73.1%, compared to V2. An even more effective reduction was achieved compared to comparison experiment 3. Compared to V3, total emissions were reduced from 10.8 L to 1.69 L, or 84.4%, by the combination of acidification and subsequent CaCN2 treatment (example 2). If no CaCN2 treatment was used, total emissions increased by 272% (acidified cattle manure in V2 compared to example 1) and by 539% (V3 compared to B2). In comparison to the reference test (V1) with a cumulative total gas volume of 15.5 L based on 1.00 kg of cattle slurry, the emissions from the pure slurry acidification were only reduced by 33.5% (V2) and 14.5% (V3).30.3% (V3) reduced.

[0093] CH4 emissions: After 400 days of anaerobic storage, 3.17 L of CH4 were released in comparison test V2 based on 1.00 kg of cattle manure. By adding CaCN2 (Example 1), emissions were reduced to 0.32 L, or 89.9%. Comparing Example 2 with V3, the combination of acidification and subsequent CaCN2 treatment (B1) shows a reduction in CH4 emissions from 4.39 L to 0.15 L, or 96.6%. Omitting CaCN2 treatment, as investigated in V2 and V3, resulted in an increase in CH4 emissions of 891% (compared to Example 1) and 2827% (compared to Example 2). Compared to the reference experiment (V1) with a cumulative CF volume of 5.24 L based on 1.00 kg of cattle slurry, CF emissions were reduced by only 39.5% (V2) and 16.2% (V3) through pure slurry acidification.

[0094] CO2 emissions: After 400 days of anaerobic storage, 1.99 L of CO2 were released per 1.00 kg of cattle manure in comparative example V2. In contrast, the addition of CaCN2 (example 1) reduced emissions to 0.18 L, or 91.0%. A comparison of example 2 with V3 shows that the combination of acidification and subsequent CaCN2 treatment reduced CO2 emissions from 2.05 L to 0.07 L, or 96.6%. Consequently, omitting CaCN2 treatment resulted in an increase in CO2 emissions of 1006% (compared to B1) and 2829% (compared to B2). Compared to the reference experiment (V1) with a cumulative CO2 volume of 3.51 L based on 1.00 kg of cattle manure, CO2 emissions were reduced by only 43.3% (V2) and 41.6% (V3) through pure manure acidification.

[0095] FhS emissions: After 400 days of anaerobic storage, 243.4 mL of H2S were released per 1.00 kg of cattle manure in comparative example. By combining acidification and the addition of CaCN2 (Example 1), emissions were reduced to 4.90 mL, or 88.7%. A comparison of comparative example V3 with example 2 shows that the combination of acidification to pH 5.5 and subsequent CaCN2 treatment reduced H2S emissions from 41.3 mL to 1.04 mL, or 97.5%, which was even more effective than at pH 6.0. Omitting CaCN2 treatment resulted in an increase in H2S emissions of 786% (compared to B1) and 3871% (compared to B2). Compared to the reference experiment (V1) with a cumulative H2S volume of 3.61 mL based on 1.00 kg of cattle manure, the H2S emissions were drastically increased by 1102% (V2) and 1044% (V3) due to the pure manure acidification.

[0096] Simply acidifying cattle manure can reduce the emissions of certain harmful gases, such as methane and CO2. However, the use of sulfuric acid increases the emissions of toxic H2S due to the sulfate addition. The combined application of acidification and CaCN2 addition over a period of 400 days can significantly reduce the emissions of harmful gases from the manure, including hydrogen sulfide, compared to acidification alone.

[0097] The single application of H2SO4 resulted in more than eleven times the amount of H2S emitted during anaerobic manure storage compared to the control experiment (V1). Consequently, while the single acidification of manure with H2SO4 inhibits general gas emissions, it appears to specifically promote desulfurization and thus H2S emissions. Additional treatment of cattle manure with CaCN2 very effectively compensates for this effect and leads to significantly reduced H2S emissions.

[0098] 2.1.4 Treatment of cattle manure with CaCN2 (comparative examples V4 and V5):

[0099] In comparative experiment V4, 3.05 kg of cattle manure was mixed with 6.34 g of CaCN2 formulation F1 and stirred in. In comparative experiment V5, 3.04 kg of cattle manure was mixed with 8.86 g of CaCN2 formulation F1 and stirred in. The gas storage bags were changed and analyzed in the comparative examples after 14, 67, 85, 108, 136, 156, 179, 200, 218, 234, 248, 267, 295, 323, 357, and 400 days. The total gas volumes emitted (V ges ) and the specific volumes of methane (CH4), carbon dioxide (CO2), and hydrogen sulfide (H2S) are listed cumulatively in Table 7. For better comparability, the gas quantities determined are standardized to 1.00 kg of cattle manure. The temporal progression of the respective gas developments is shown in Figures 9 to 12. Table 7: Cumulative gas emissions in V4 and V5 (based on 1.00 kg of cattle manure)

[0100] Discussion of the results: Total emissions: After 400 days of anaerobic storage, 14.6 L of total gas were released in comparative example V4 based on 1.00 kg of cattle manure. According to examples 1 and 2, compared to V4, a reduction in emissions to 2.77 L, or by 80.7%, and to 1.69 L, or by 88.4%, was achieved through the additional CaCN2 treatment. A comparison of examples 1 and 2 with V5 shows a reduction in total emissions through the combination of acidification and subsequent CaCN2 treatment from 10.6 L to 2.77 L, or by 73.9%, and to 1.69 L, or by 84.1%. If prior manure acidification with H2SO4 is omitted, total emissions increase by 427-764% (comparison of B1 and B2 with V4) or by 283-527% (comparison of B1 and B2 with V5).Compared to the reference test (V1) with a cumulative total gas volume of 15.5 L based on 1.00 kg of cattle manure, the emissions were reduced by 5.81% (V4) and 31.6% (V5) by the pure CaCN2 treatment.

[0101] CH4 emissions: After 400 days of anaerobic storage, 4.76 L of CH4 were released per 1.00 kg of cattle manure in comparative experiment V4. Additional acidification reduced emissions to 0.32 L, or 93.3% (Example 1), and to 0.15 L, or 96.8% (Example 2). A similar reduction is achieved when comparing examples 1 and 2 with comparative example V5. The CH4 emission through the combination of acidification and subsequent CaCN2 treatment decreases from 3.38 L to 0.32 L, or 90.5% (Example 1), and to 0.15 L, or 95.6% (Example 2). By omitting prior manure acidification with H2SO4 as performed in Examples 1 and 2, CH4 emissions increased by 1388-3073% and 956-2153%, respectively. Compared to the reference experiment (V1) with a cumulative CH4 volume of 5.24 L per 1 kg of cattle manure, CH4 emissions were reduced by 9.16% (V4) and 9.16% (V5) respectively, when treated with CaCN2 alone.35.5% (V5) reduced.

[0102] CO2 emissions: After 400 days of anaerobic storage, 2.46 L of CO2 were released per 1.00 kg of cattle manure in comparative experiment V4. Additional acidification reduced CO2 emissions to 0.18 L, or 92.7% (Example 1), and to 0.07 L, or 97.2% (Example 2). A slightly smaller reduction results from a comparison of Examples 1 and 2 with V5. CO2 emissions in B1 and B2 decreased from 1.71 L to 0.18 L, or 89.5%, and to 0.07 L, or 95.9%, compared to V5. The omission of prior manure acidification with H2SO4 caused an increase in CO2 emissions compared to B1 and B2 by 1267-3414% (V4) and 850-2343% (V5). Compared to the reference experiment (V1) with a cumulative CO2 volume of 3.51 L per 1 kg of cattle manure, CO2 emissions were reduced by 29.9% (V4) and 51.3% (V5) through the pure CaCN2 treatment.H2S emissions: After 400 days of anaerobic storage, 0.01 mL of H2S per 1.00 kg of cattle manure was released in comparison experiments V4 and V5. In examples 1 and 2, the additional acidification increased emissions to 4.90 mL and 1.04 mL, respectively. Omitting the manure acidification with H2SO4 resulted in a reduction of H2S emissions by 99.0-99.8% (V4 / V5 compared to B1 and B2). Compared to the reference experiment (V1) with a cumulative FhS volume of 3.61 mL per 1.00 kg of cattle manure, H2S emissions were reduced by 99.7% (V4 and V5) through the pure CaCN2 treatment.

[0103] Comparative trials V4 and V5 also show that treating acidified farmyard manure with calcium cyanamide can further reduce pollutant emissions compared to treating it with CaCN2 alone. However, the desulfurization effect is not achieved with the addition of CaCN2 alone. Overall, however, the advantages of the synergistic effects of the combined process clearly outweigh the disadvantages, especially since increased FhS development only begins relatively late, after more than 300 days, with anaerobic storage of cattle manure.

[0104] 2.2 Test series 2

[0105] 2.2.1 Comparison example V6 (control):

[0106] As a reference for the gas quantities emitted during anaerobic storage of treated farmyard manure, 3.00 kg of untreated cattle manure without additives was examined (control experiment V6 according to Table 3). The gas storage bags were changed and analyzed after 7, 33, 69, 85, 96, 104, 112, 117, 124, 133, 139, 147, 156, and 167 days. The total gas volume emitted (V ges ) and the specific volumes of methane (CH4), carbon dioxide (CO2), hydrogen sulfide (H2S), ammonia (NH3), and nitrous oxide (N2O) are listed cumulatively in Table 8. For better comparability, the gas quantities determined are standardized to 1.00 kg of cattle manure. The temporal course of the respective gas developments is shown in Figures 13 to 18. Table 8: Cumulative gas emissions based on 1.00 kg of cattle manure in liters or milliliters.

[0107] 2.2.2 Combination of acidification and CaCN2 treatment of cattle manure (B3-B8): According to Example B3 (Table 3), 3.00 kg of cattle manure was adjusted to a pH of 5.5 with 16.3 g of 95% H2SO4. Subsequently, 6.55 g of CaCN2 formulation F2 were added and stirred in. According to Example B4 (Table 3), 3.00 kg of cattle manure was adjusted to a pH of 5.5 with 16.4 g of 95% H2SO4. Subsequently, 3.93 g of CaCN2 formulation F2 were added and stirred in. Furthermore, 3.00 kg of cattle manure were adjusted to a pH of 5.5 with 35.8 g of 32% hydrochloric acid (HCl, Example B5), 22.6 g of 100% acetic acid (HOAc, Example B6), 41.5 g of 50% citric acid (CA, Example B7), or 40.4 g of 90% lactic acid (LA, Example B8). Subsequently, 6.55 g of CaCN2 formulation F2 were added and stirred in. The gas storage bags were changed and analyzed for all examples after 7, 33, 69, 85, 96, 104, 112, 117, 124, 133, 139, 147, 156, and 167 days.The total gas volumes emitted (V. ges ) and the specific volumes of methane (CH4), carbon dioxide (CO2), hydrogen sulfide (H2S), ammonia (NH3), and nitrous oxide (N2O) are listed cumulatively in Tables 9-11. For better comparability, the gas quantities determined are standardized to 1.00 kg of cattle manure. The temporal progression of the respective gas evolutions is shown in Figures 13 to 18. Table 9:

[0108] Cumulative gas emissions based on 1.00 kg of cattle manure in liters or milliliters.

[0109] Table 10:

[0110] Cumulative gas emissions based on 1.00 kg of cattle manure in liters or milliliters.

[0111] Table 11: Cumulative gas emissions based on 1.00 kg of cattle slurry in litres or millilitres.

[0112]

[0113] Discussion of the results:

[0114] Total emissions, CH4, CO2 and H2S emissions:

[0115] After 167 days of anaerobic storage in reference experiment V6, 22.8 L of total gas, 11.3 L of CH4, 7.56 L of CO2, and 8.88 mL of H2S were released per 1.00 kg of cattle manure. Acidification with various acids to pH 5.5 and subsequent addition of CaCN2 (Examples 3-8) significantly reduced emissions. Accordingly, total emissions were reduced by 87.1-93.7%, CH4 emissions by 99.5-100%, CO2 emissions by 89.9-98.3%, and H2S emissions by 71.2-99.9%. The acid used for acidification plays only a minor role in the emission reduction effect. However, when using sulfuric acid (Examples 3 and 4), H2S emissions increase due to the additional sulfate addition. The influence of the dosage of CaCN2 (Formulation F2) is evident in Examples 3 and 4. The H2S emissions of 8.88 mL (Reference Experiment V6) are reduced to 2.56 mL (71.2%) in Example 4 and 0.49 mL (94.4%) in Example 3.

[0116] NHs emissions:

[0117] After 167 days of anaerobic storage, 0.49 mL of NH3 was released per 1.00 kg of cattle manure in the reference experiment (V6). By acidifying with various acids to pH 5.5 and subsequently adding CaCN2 (Examples 3-8), emissions can be reduced by 88.4-96.8%.

[0118] N2O emissions: After 167 days of anaerobic storage, 2.21 mL of N2O were released per 1 kg of cattle manure in the reference experiment (V6). Acidification with various acids to pH 5.5 and subsequent addition of CaCN2 (Examples 3-8) reduced emissions by 89.7-99.0%.

[0119] The series of experiments shows that the combination of manure acidification followed by CaCN2 treatment is a highly effective measure for reducing harmful gas emissions during the storage of farmyard manure, such as cattle manure. The type of acid used for acidification is less important for reducing (harmful gas) emissions than the adjusted pH value. Furthermore, the dosage of CaCN2 can be reduced in combination with an acid without compromising the gas emission reduction compared to treatment with CaCN2 alone.

[0120] 2.2.3 Acidification of cattle manure with H2SO4 (Comparison Example V7):

[0121] 3.00 kg of cattle manure was adjusted to a pH of 5.5 with 17.6 g of 95% H2SO4 (Comparative Example V7). The gas storage bags were changed and analyzed after 7, 33, 69, 85, 96, 104, 112, 117, 124, 133, 139, 147, 156, and 167 days. The total gas volumes emitted (V ges ) and the specific volumes of methane (CH4), carbon dioxide (CO2), hydrogen sulfide (H2S), ammonia (NH3), and nitrous oxide (N2O) are listed cumulatively in Table 12. For better comparability, the gas quantities determined are standardized to 1.00 kg of cattle manure. The temporal progression of the respective gas evolutions is shown in Figures 19 to 24.

[0122] Table 12. Cumulative gas emissions V7 (based on 1.00 kg of cattle manure) in litres or millilitres.

[0123]

[0124] Discussion of the results:

[0125] Total emissions, CH4, CO2 and H2S emissions:

[0126] After 167 days of anaerobic storage, 7.19 L of total gas, 2.09 L of CH4, 1.92 L of CO2, and 51.3 mL of H2S were released in comparative example V7 based on 1.00 kg of cattle manure. By adding CaCN2 (Examples 3-8), a reduction in emissions can be achieved compared to V7. Total emissions could be reduced by 59.0-79.8%, CH4 emissions by 97.6-100%, CO2 emissions by 60.4-93.2%, and H2S emissions by 95.0-100%. If no CaCN2 treatment is carried out, this led to a significant increase in total emissions, including CH4, CO2, and H2S emissions (acidified cattle manure in V7 compared to Examples 3-8). Compared to the reference test (V6) with cumulative volumes of total gas (22.8 L), CH4 (11.3 L), CO2 (7.56 L) and H2S (8.88 mL) based on 1.00 kg cattle slurry, the emissions from the pure slurry acidification with sulfuric acid were reduced by 68.5 % (Vges ), 81.4% (CH4) and 74.6% (CO2) and H2S emissions increase drastically by 477.4%.

[0127] NHs emissions:

[0128] After 167 days of anaerobic storage, 0.10 mL of NH3 was released per 1.00 kg of cattle manure in Comparative Example V7. By adding CaCN2 (Examples 3-8), emissions can be reduced to 0.02-0.06 mL, or 40.0-80.0%. N2O emissions:

[0129] After 167 days of anaerobic storage, 0.54 mL of N2O was released per 1.00 kg of cattle manure in Comparative Example V7. By combining acidification and the addition of CaCN2 (Examples 3-8), emissions were reduced to 0.02-0.23 mL, or 57.4-96.3%.

[0130] The findings from the second series of experiments confirm or expand on the results from the first series. For example, emissions of harmful gases from farmyard manure can be significantly reduced through the combined application of acidification and CaCN2 addition compared to acidification alone. Especially when using sulfuric acid, a low CaCN2 dosage can compensate for the sometimes significant H2S emissions.

[0131] 2.2.4 Treatment of cattle manure with CaCN2 (comparative examples V8 and V9):

[0132] In comparative experiment V8, 3.00 kg of cattle manure was mixed with 6.55 g of CaCN2 formulation F2. In comparative experiment V9, 3.00 kg of cattle manure was mixed with 3.94 g of CaCN2 formulation F2. The gas storage bag changes and analyses were carried out in both comparative examples after 7, 33, 69, 85, 96, 104, 112, 117, 124, 133, 139, 147, 156, and 167 days. The total gas volumes emitted (V ges) and the specific volumes of methane (CH4), carbon dioxide (CO2), hydrogen sulfide (H2S), ammonia (NH3), and nitrous oxide (N2O) are listed cumulatively in Table 13. For better comparability, the gas quantities determined are standardized to 1.00 kg of cattle manure. The temporal progression of the respective gas evolutions is shown in Figures 25 to 30.

[0133] Table 13: Cumulative gas emissions in V8 and V9 (based on 1.00 kg of cattle slurry) in litres and millilitres.

[0134]

[0135] Discussion of the results:

[0136] Total emissions, CH4, CO2, and H2S emissions: After 167 days of anaerobic storage, comparative example V8 released 5.88 L of total gas, 1.09 L of CH4, 1.24 L of CO2, and 0.03 mL of H2S based on 1.00 kg of cattle manure. Compared to V8, examples 3 and 5-8 achieved significant reductions in total emissions (49.8-75.3%), CH4 emissions (95.4-100%), and CO2 emissions (38.7-89.5%). A similar picture emerges when comparing V9 and Example 4. On the one hand, total emissions were reduced from 9.87 L to 2.25 L (77.2%), CH4 emissions from 3.14 L to 0.02 L (99.4%), and CO2 emissions from 2.66 L to 0.28 L (95.1%). If the prior manure acidification is omitted, there is an increase in total emissions, CH4, CO2 (comparison of B3-8 with V8 and V9), and H2S emissions (comparison of B5-8 with V8 and V9).However, due to the lack of sulfate input by sulfuric acid, H2S emissions are reduced when the acid is omitted (comparison B3 and B4 with V8 and V9).

[0137] NH3 emissions: After 167 days of anaerobic storage, 0.09 mL of NH3 was released per 1.00 kg of cattle manure in comparative example V8. By adding CaCN2 (examples 3 and 5-8), emissions were reduced to 0.02-0.06 mL, or 33.3-77.8%. Comparing V9 with B4, a reduction in NH3 emissions from 0.16 mL to 0.03 mL, or 81.3%, was achieved.

[0138] N2O emissions:

[0139] After 167 days of anaerobic storage, 0.40 mL of N2O was released per 1.00 kg of cattle manure in comparative example V8. The combination of acidification and the addition of CaCN2 (examples 3 and 5-8) achieved a reduction in emissions to 0.02-0.23 mL, or 42.5-95.0%. The comparison of V9 with B4 reveals a reduction in NH3 emissions from 0.77 mL to 0.06 mL, or 92.2%.

[0140] The results of the second series of experiments show that, in addition to the formation and release of the harmful gases CH4, CO2, and H2S, NH3 and N2O emissions can also be further reduced by treating acidified farmyard manure with calcium cyanamide compared to treatment with CaCN2 alone. The lower concentration CaCN2 treatment (V9 / B4) shows similarly good results to the higher-dose variant (V8 / B3). The combination of manure acidification and CaCN2 treatment shows a very good effect in terms of gas release, even with a reduced CaCN2 dosage (B4), and even surpasses the higher concentration CaCN2 treatment alone (V8).

[0141] 2.2.5. Long-term measurements within test series 2

[0142] Test series 2 was continued for a longer period until its termination after 335 days. The total gas volumes emitted (Vtotal) and the specific volumes of methane (CH4), carbon dioxide (CO2), hydrogen sulfide (H2S), ammonia (NH3), and nitrous oxide (N2O) on two additional measurement days, after 268 and 335 days of storage, respectively, are listed cumulatively in Table 14.

[0143] Table 14: Cumulative gas emissions of test series 2 (V6-V9 and B3-B8; based on 1.00 kg cattle manure) after 268 and 335 days of storage, respectively.

[0144]

[0145] Long-term measurements show that gas emissions from manure can be significantly reduced over the long term through treatment with calcium cyanamide in combination with manure acidification. The long-term measurements also impressively demonstrate the synergistic effect of the two measures.

[0146] Summary of results

[0147] As the examples show, the combination of acidification of farmyard manure and subsequent CaCN2 treatment is a very effective measure for reducing pollutant gas emissions during the storage of farmyard manure.

[0148] Treating farm manure with CaCN2 alone is already an effective measure for reducing harmful gas emissions. Gas emissions can also be reduced by acidifying the farm manure. While acidifying farm manure is a process that must be repeated several times to effectively reduce harmful gas emissions, in combination with CaCN2 treatment, a single acidification at the beginning of storage is generally sufficient for long-term emissions reduction. Furthermore, a strong synergistic effect in reducing gas emissions, particularly in reducing harmful ammonia, carbon dioxide, nitrous oxide, methane, and hydrogen sulfide releases, can be observed when acidifying farm manure is combined with CaCN2 treatment. For example, methane emissions are reduced after more than 5 months (156 and 164 hours, respectively).167 days) by acidification alone by 66.8-81.4% (V2, V3 and V7) and by CaCN2 treatment alone by 72.1-99.4% (V4, V5, V8 and V9). If both measures are combined, a reduction of 99.5-100% (B1-B8) results, which is higher than would be expected from the individual measures. Acidification alone also leads to a reduction in CCh emissions by 53.1-74.6% (V2, V3 and V7). CaCN2 treatment alone leads to a reduction of 64.8-91.7% (V4, V5, V8 and V9). If both measures are combined, a reduction of 89.9-99.1% (B1-B8) results, which is better than would be expected from the individual measures. A similar picture emerges for NH3 and N2O emissions. While acidification alone reduces NH3 and N2O emissions by only 79.7% and 75.7% (V7), respectively, the combined process results in reductions of 88.4-96.8% and 89.7-99.0% (B1-B8), respectively.The sole use of CaCN2, however, only reduces ammonia and nitrous oxide emissions by 67.4-82.0% and 65.1-82.0%, respectively (V8 and V9).

[0149] With longer storage times, the synergistic effect becomes even more pronounced compared to the individual applications. For example, a combination of manure acidification and CaCN2 treatment after 400 days of storage (B1 and B2) still results in a reduction in CH4 emissions by 93.9–97.1% and in CO2 emissions by 94.9–98.0%. In contrast, when only one of the two measures was applied, CH4 and CO2 emissions were reduced by only 16.2–39.5% and 41.6–43.3%, respectively, for manure acidification alone (V2 and V3) and by 9.2–35.5% and 29.9–51.3%, respectively, for CaCN2 treatment alone (V4 and V5). In general, after initially adjusting the pH of the examined cattle manure to 6.0 or 5.5 and subsequent CaCN2 treatment, only negligible emissions were detected during anaerobic storage over a period of 400 days.

[0150] Furthermore, the process according to the invention demonstrates excellent long-term efficacy even at higher pH values ​​(6.0 vs. 5.5) and at a lower CaCN2 dosage (0.13% vs. 0.22%). This allows both the required acid quantity and the dosage of cyanamide salt to be reduced while maintaining an effective reduction in (polluting gas) emissions during the storage of farmyard manure.

[0151] The type of acid used for acidification is largely irrelevant to the synergistic effect of the process described here. However, in addition to ecological (especially higher H2S and IShO emissions from sulfuric and nitric acid) and economic (price, availability, and logistics) factors, safety aspects (hazards to humans and animals, and material resistance / corrosion) also influence the selection.

Claims

Claims A method for reducing the emission of harmful gases from farm manure during storage, the method comprising the following steps: a) providing farm manure, and b) acidifying the farm manure until a pH value in the range of pH 4.5 to 6.8 is set, and c) adding 0.01 wt.% to 1.0 wt.%, based on the total weight of the farm manure, of a cyanamide salt composition to the farm manure. Method according to claim 1, characterized in that in a first step the farm manure is provided and simultaneously therewith and / or thereafter the acidification and the addition of the cyanamide salt composition take place, wherein the acidification can take place before, after or simultaneously with the addition of the cyanamide salt composition. Method according to one of the preceding claims, characterized in that with the acidification in step b) a pH value in the range of 5.0 to 6.3 is set.Process according to one of the preceding claims, characterized in that the acidification is carried out with an acid selected from the group consisting of sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, silicic acid, formic acid, acetic acid, lactic acid, oxalic acid, citric acid, fumaric acid, benzoic acid, maleic acid, and mixtures thereof. Process according to one of the preceding claims, characterized in that the cyanamide salt composition contains a) 25 to 95 wt.% cyanamide salt, in particular calcium cyanamide. b) up to 15% by weight of free carbon, coal or graphite, c) 1 to 40% by weight of at least one compound from the group of carbonates, in particular from the group consisting of magnesium carbonate, magnesium bicarbonate, calcium carbonate, calcium bicarbonate or mixtures thereof, d) less than 20% by weight of oxides and hydroxides, in particular from the group consisting of magnesium oxide, magnesium hydroxide, calcium oxide and calcium hydroxide or mixtures thereof; e) up to 15% by weight of water, the weight percentages being based in each case on the total weight of the cyanamide salt composition.

6. A process according to any one of the preceding claims, characterized in that a total amount of cyanamide salt in the range of 0.5 to 10 kg per 1 m 3 based on the total amount of farmyard manure added.

7. Method according to one of the preceding claims, characterized in that the farm manure is liquid manure, slurry or biogas fermentation residues.

8. Use of a combination of an acid and a cyanamide salt composition or of an acidic compound and a cyanamide salt composition for reducing the emission of ammonia, carbon dioxide, nitrous oxide, methane and / or hydrogen sulphide from farmyard manure.

9. Use of a cyanamide salt composition to reduce the emission of hydrogen sulphide from farmyard manure acidified with sulphuric acid.

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