NL2017075B1 - Reducing health risk to humans or livestock due to exposure of hydrogen cyanide (HCN) released from manure - Google Patents

Abstract

The invention relates to a method for reducing a health risk to humans or livestock due to exposure of hydrogen cyanide (HCN) released from manure, comprising contacting the manure with an alkaline substance, which alkaline substance is used in an effective amount whereby – when mixed – the pH of a mixture of the manure and alkaline substance is at least 10.0. The invention further relates to a livestock facility wherein a method according to the invention can be employed.

Description

Patent center

The Netherlands

(21) Application number: 2017075 © Application submitted: 30/06/2016

Θ 2017075

BI PATENT (51) Int. CL:

A01C 3/02 (2017.01) A01C 3/00 (2017.01) C05F 3/00 (2017.01)

(Tl) Application registered: (73) Patent holder (s): 09/01/2018 Cornells Marinus van 't Land in Enschede. (43) Application published: 15/01/2018 (72) Inventor (s): Cornells Marinus van 't Land in Enschede. Patent granted: 19/01/2018 (74) Agent: (45) Patent issued: ir. C.M. Jansen et al. In The Hague. 05/02/2018

Reducing health risk to humans or livestock due to exposure of hydrogen cyanide (HCN) released from manure © The invention relates to a method for reducing a health risk to humans or livestock due to exposure of hydrogen cyanide (HCN) released from manure, including contacting the manure with an alkaline substance, which alkaline substance is used in an effective amount. - when mixed - the pH of a mixture of the manure and alkaline substance is at least 10.0. The invention further relates to a livestock facility according to the invention can be employed.

NL BI 2017075

This patent has been granted regardless of the attached result of the research into the state of the art and written opinion. The patent corresponds to the documents originally submitted.

P111843NL00

Title: Reducing health risk to humans or livestock due to exposure of hydrogen cyanide (HCN) released from manure

The invention relates to a method for reducing a health risk to humans or livestock due to exposure of hydrogen cyanide (HCN) released from manure. The invention further relates to a livestock facility and to the use of an alkaline substance to reduce the risk of lethal accidents to humans or livestock.

In many livestock operations livestock, such as dairy cattle or pigs, are a hero for a substantial amount or their lifetime in stables. The floors of the stables typically container opening, such as a grid, through which urine and faeces produced by the livestock can pass. The urine and faeces are typically collected and stored in manure vaults underneath the floors. The manure vaults are emptied at intervals, e.g., about once a month. For legal or practical reasons, the manure collected from the vaults is not always immediately put to further use, e.g., to manure arable land or to be further processed (e.g., to produce dry manure). In many countries there are restrictions with respect to spreading manure on land. E.g., in The Netherlands during a period of about five months per year (between about 1 September and about 1 February) it is not allowed to spread out manure. Therefore, manure tasks from manure vaults is often stored in a manure container, such a silo, until further use.

In manure, various chemical substances are produced as a result of chemical reactions and microbiological activity. These chemical substances include volatile substances that can be a health hazard. In The Netherlands, about once a year a person suffers from a lethal accident due to exposure to such substances. Statistics on the number of livestock killed by exposure to such a gas are lacking, but are roughly estimated to be about

100 per year, in The Netherlands. Obviously, on a global scale the number of casualties are a manifold of these numbers.

In the art, it is generally considered that hydrogen sulphide (H2S) is responsible for the accidents. This gas is often found in air or stables with livestock is a hero during manure mixing, at concentration as high as 300-400 ppm.

However, another gas that can be formed in the manure is hydrogen cyanide (HCN). The inventor has realized that this gas is a major contributor to the health risk. Exposure to a concentration of about 100 ppm HCN in air can cause sudden unconsciousness to healthy adult humans, which is an immediate health risk. First of all, when becoming unconscious the human will generally collapse, and thus may fall off a ladder or into the manure. Secondly, a short exposure to a level of 100 ppm may cause the exposed person (or livestock) to stop breathing. Thirdly, a hydrogen cyanide concentration in the range or 100-300 ppm in air will typically kill a human within 10—60 minutes.

HCN levels in the air in over twenty dairy-cattle stables have been monitored during manure mixing and peak concentrations in the range 10-400 ppm, with an arithmetic mean or 155 ppm, have been measured. Further, HCN levels during manure mixing were measured continuously for fifteen minutes in the dairy-cattle stables, which levels, as time-weighted averages, were found to be in the range 3-144 ppm.

Herewith, the inventor comes to the conclusion that HCN released from manure is a serious health risk to humans and livestock in livestock facilities and has led most likely to be a least number of fatal accidents in these facilities over the last decades.

It is an object of the present invention to provide a way to reduce health risks, in particular to reduce the risk of lethal accidents, to humans or livestock due to exposure or hydrogen cyanide (HCN) released from manure.

It has now been found that this object is with by treating the manure with a specific substance.

Done, the invention relates to a method for reducing a health risk to humans or livestock due to exposure of hydrogen cyanide (HCN) released from manure, including contacting manure with an alkaline substance, which alkaline substance is used in an effective amount amount - when mixed - the pH of a mixture of the manure and alkaline substance is at least 10.0.

The method for reducing a health risk to humans or livestock due to exposure of hydrogen cyanide (HCN) released from manure, in particular comprises contacting the manure with an alkaline substance, where the alkaline substance is added in an effective amount to increase the pH of a mixture of manure and alkaline substance at a value of at least 10.0, preferably at least 10.2, more preferably at least 10.4.

The invention further relates to a livestock facility, including a roofed space, such as a stable, for holding livestock, which space has a floor containing opening, through which manure can pass, and essentially underneath which floor is a manure vault is present, which vault is provided with an aqueous solution or an alkaline substance having a pH or at least

10.5 or with manure treated with alkaline substance, the treated manure having a pH of at least 10.0.

The invention further relates to a livestock facility, including a roofed space, such as a stable, for holding livestock, which space has a floor containing opening, through which manure can pass and essentially underneath which floor is a manure vault is present (suitable to hold an aqueous solution or an alkaline substance), which vault is provided with an outlet for manure, which outlet is connected to a channel, such as a pipe or tube for transporting the manure from the vault to a manure storage container, such as a silo , which container is provided with a dosage system for providing an alkaline substance to the container.

The floor of the roofed space can, e.g., be a slotted floor or a grid floor.

The invention further relates to the use of an alkaline substance to reduce the risk of lethal accidents to humans or livestock in a livestock facility due to exposure of hydrogen cyanide (HCN) released from manure.

The invention further relates to the use of an alkaline substance to reduce the (average) hydrogen cyanide (HCN) concentration in the air inside a space, such as a stable, where live stock is hero or inside a storage container holding manure.

Without being bound by theory it is thought that the method is effective due to the ionization of HCN at strongly alkaline pH. The ionized form (CN ^- ) is essentially non-volatile and remains in the manure. At pH 10.0 more than 75% of the cyanide (the sum of HCN and CN ') is in the ionized form, whereas in untreated manure essentially all of the cyanide is present in its volatile form: HCN. Thus, the treatment according to the invention is effective in reducing HCN release from manure containing a substantial amount of cyanide. Incidentally, evaporation of hydrogen sulphide (H2S) from the manure is considered to be essentially avoided at a pH of 10.0 or more, because at such a high pH essentially all sulphide is ionized.

The effect of the high pH is fast, and it is considered that the method is also effective in cases of a significant microbiological activity in the treated manure remains, since formed HCN will readily dissolve in a fluid having a pH of 10.0 or more.

The high pH resulting from a treatment in accordance with the invention has a further advantage, in cases where acidic scrubbing fluid is added to the manure (e.g., shortly before spreading the manure on land). Scrubbers are used in particular to remove odorous components, such as ammonia, and dust particles from air in stables of pigs are held. The scrubbing fluid is usually an aqueous sulphuric acid solution (pH, e.g., about

2). The used scrubbing fluid is a source of nutrients (nitrogen) and thus contributes to the quality of manure. However, this addition of the acidic fluid to non-treated manure is risky, because it can be liberated gaseous HCN quickly due to the sudden decrease of pH or the manure to an acidic pH.

Since the pH of the manure treated in accordance with the invention is relatively high, the addition of a controlled amount or scrubbing liquid is less risky, as long as care is tasks not to reduce the pH too much.

As used, the term "pH" is used for the apparent pH, i.e., the pH measured with a standard H + electrode, at 25 ° C. The pH is measured by inserting a calibrated pH electrode in the medium, such as manure or an aqueous solution, or which the pH is to be measured.

The term "or" as used according to means "and / or" unless specified otherwise.

The term "a" or "an" used used means "at least one" unless 15 specified otherwise.

The term "essential (ly)" or "substantial (ly) is generally used to indicate that it has the general character or function or that which is specified. When referring to a quantifiable feature, this term is generally used to indicate that it is more than 75%, in particular more than 90%, more in particular more than 95%, even more in particular more than 98% or the maximum of that feature. The term 'essentially free' is generally used to indicate that a substance is not present (below the detection limit achievable with analytical methods as available on the effective filing date) or present in such a low amount that it does not significantly affect the property whether the product that is essentially free or said substance or that it is present in such a low amount (trace) that it does not need to be labeled on the packaged product that is essentially free of the substance. In practice, in quantitative terms, a product is usually considered essentially free of a substance, if the content of the substance is 0 - 0.1 wt.%, In particular 0 0.01 wt.%, More in particular 0 - 0.005 wt.%, based on total weight of the product in which it is present.

The term "about" in relation to a value generally includes a range around that value as will be understood by the skilled person. In particular, the range is from at least 10% below to at least 10% above the value, more specifically from 5% below to 5% above the value.

When referring to a “noun” (e.g., a compound, an additive etc.) in singular, the plural is meant to be included, unless specified otherwise.

For the purpose of clarity and a concise description features are described as part of the same or separate expired, however, it will be appreciated that the scope of the invention may include having combinations of all or some of the features described.

The inventor realized that HCN released from manure is a major contributor to health risks in livestock operations and that by increasing the pH of the manure to a value of at least about 10.0 the cyanide in the manure is at least substantially in its non-volatile ionized form. Herewith, it is possible to significantly reduce peak concentrations or HCN in the air above the treated manure. Preferably, the pH is maintained at a value or at least 10.2. More preferably, the pH of a mixture of the manure and the alkaline substance is at least 10.4, by which it is possible to have about 6% or less of the total cyanide in a volatile form, which is more than 15 times less than at a typical pH or manure. The upper limit is not particularly critical and may in principle be up to about 13, in particular 12 or less. However, it is reasoned that above a pH or about 11.5 a further increase or pH provides hardly a further reduction in the ratio [HCN] / [CN ·], as essentially all cyanide is ionized at and above that pH. A further elevated pH above 11.5 may, e.g., desired if an acidic waste stream, e.g., from an air scrubber, is later added to the manure.

The skilled person will be able to select suitable amounts of alkaline substance needed to adapt and maintain the pH in a desired range on the basis of the information disclosed, common general knowledge, and optionally routine monitoring of the pH during addition of the alkaline substance .

As alkaline substance, in particular relatively strong bases are used that are soluble in water at a concentration sufficient to provide an aqueous solution having a pH or at least about 0.5 pH unit, preferably at least about 1.0 pH unit, more preferably about 1.7 pH units above the desired pH for the treated manure. Such substance is then usually applied as an aqueous solution. A relatively high pH relative to the target pH allows working with a relatively small volume of the alkaline aqueous solution.

E.g., an aqueous solution or a strong base having a pH of 11.7 may be sufficient to maintain an approximately 20-fold amount or manure at a pH above 10.0.

Usually, one or more alkaline substances are selected from the group consisting of calcium hydroxide (Ca (OH) 2), sodium hydroxide (NaOH), soda (Na2CO3), magnesium hydroxide (Mg (OH) 2, potassium hydroxide (KOH) and potassium carbonate (K 2 CO 3).

Particularly preferred is calcium hydroxide or a mixture of alkaline substances including a substantial amount of calcium hydroxide.

Soda and potassium carbonate are less strong bases than sodium hydroxide and calcium hydroxide. This means that a higher concentration is needed to obtain an aqueous alkaline solution with a specific pH, e.g., 11. However, the carbonate has some buffering capacity, which can help maintain the pH of the treated buffer at elevated levels.

In principle, it is possible to add alkaline substance in dry form to (part of) the manure. However, the alkaline substance is advantageously first dissolved in water (e.g., tap water, surface water or ground water) and then the treatment of the manure takes place.

Usually, the manure produced by the livestock is kept for at least a number of weeks, typically up to about a month in a manure vault (essentially underneath the floor of the space, the livestock is accommodated). Therefore, the manure is usually treated with the alkaline substance while being in the manure vault. Advantageously, an aqueous solution of the alkaline substance has been introduced into an essentially empty vault. In this embodiment, usually 2-20% of the volume of the vault, preferably 4-10% of the volume of the vault is filled with an aqueous solution of the alkaline substance. This solution preferably has a pH value of at least 11, more preferably or 11.5-13.0, in particular or 11.6-12.5. The higher the pH, the less volume is needed to maintain a specific amount of treated manure at a desired pH. Usually, (essentially) all the aqueous solution or the alkaline substance is added prior to (fresh) manure starting to enter the vault. Thus, the fresh manure is allowed to drop through the opening in the floor (e.g., a slotted floor) on which the livestock are hero, into the vault and into the alkaline substance. In this way, the manure is contacted effectively in a simple manner with the alkaline substance, without needing equipment to mix the contents of the vault.

It is generally not necessary to agitate the manure and the alkaline substance in order to be effective, in particular not if the alkaline substance is applied as an aqueous solution. Manure and aqueous solution of the alkaline substance do not need to form a single homogeneous phase in order to be effective. Satisfactory results can, for instance, be achieved in a manure vault or other container for manure in which a manure phase is at least substantially surrounded by an alkaline aqueous solution phase. HCN gas formed in the manure phase diffuses then into the alkaline aqueous solution phase and is quickly dissociated (and stably dissolved) into the alkaline aqueous phase, without needing an active agitation. The lack of a need for (intensive) mixing or manure and alkaline aqueous solution is advantageous not only because it simplifies the method, but also because mixing may promote increased release rates of gases that have been built up in the manure beforehand.

If needed, the manure treated with alkaline substance can be agitated in a manner known in the art. Agitation may, e.g., be desired (occasionally) to avoid crust formation (in the case of dairy-cattle manure) or shortly before the manure is removed from the vault or other container where it is stored.

In addition or alternatively, manure stored in a separate closed manure storage container (such as a manure silo) is treated with the alkaline substance. This can be done in a manner analogous to the treatment in the manure vault.

After storage, the treated manure can be collected directly from the vault or from the closed storage container and put to further use, optionally after reducing the pH to about neutral, or - preferably slightly alkaline value (about pH 8), by adding an acid and homogenizing the mixture. If the pH is reduced, care should be taken that humans are not exposed to toxic levels or HCN or other hazardous gases that may be released due to the pH reduction. Eg, by wearing proper protective gear, by carrying out the pH reduction in an open area where gas can easily spread such concentrations cannot build up to hazardous levels etc .. Further uses include spreading the manure over arable land or further processing to three manure , or transportation to a biogas production facility. It is also possible to add an acidic solution to a closed container holding the treated manure, shortly (e.g., less than an hour) before the treated manure is transferred into a closed tank for transporting the manure, e.g., a slurry tank.

The invention further relates to a livestock facility of livestock is a hero in a roofed space, such as a stable. The livestock facility is provided with means to reduce a health risk due to HCN exposure. Typically the livestock facility has a manure vault, and / or a separate essentially closed storage container, holding manure treated by a method according to the invention, ie, having a pH of at least 10.0, preferably or at least 10.2, more preferably of at least 10.4. As will be understood by the skilled person, an essentially or substantially closed space, such as a silo or other container, does not need to be air-tight. The storage containers generally contain a vent.

At least prior to use, the manure vault or a separate (essentially closed) storage container, preferably contains an aqueous solution of the alkaline substance having a pH higher than 10.0, preferably at least 10.5, more preferably at least 11.0, in particular about 11.5 .

In an embodiment, the livestock facility comprises a dosage system for providing an alkaline substance, in particular an aqueous solution or the alkaline substance, the manure vault or the separate closed storage container. Preferably, the dosage system comprises a vessel with a stirrer for dissolving an alkaline substance in water, to provide an aqueous alkaline solution or the alkaline substance, which vessel is positioned at an elevated level, relative to at least the floor of the manure vault and an outlet at or near the bottom of the vessel which outlet is connected to a channel for transporting to the vault respectively container. Alternatively or in addition, the dosing system has a pump for pumping the aqueous solution to the vault or to a separate storage container via a line from the dosing system to the vault or separate storage container.

In a specific version, the livestock facility has a dosing system for providing an aqueous solution of the alkaline substance to the vault respectively container, which dosing system comprises a vessel, including a stirrer for dissolving an alkaline substance in water, the vessel having a dished bottom, in particular a torispherical head (eg, according to DIN 28011, in German called “Klöpperboden” after its inventor Georg Kloppsch) in which bottom an outlet for the alkaline substance dissolved in water is present, which outlet is positioned to introduce the dissolved alkaline substance into a channel, positioned between the outlet and the vault respectively container, which channel is arranged to let the aqueous solution of the alkaline substance pass from the outlet of the vessel into the vault respectively container.

In an embodiment, the livestock facility is provided with a pH monitoring system. In addition to a pH meter such a system may include a signaling unit that provides a warning signal if the pH of the treated manure is no longer within a desired range. In principle it is possible to provide a pH meter in the vault or other container in which the manure is kept. However, in a practical approach, the pH is monitored by taking a sample of the manure and measuring the pH.

In an advantageous embodiment, the livestock facility comprises an air treatment system, for removing ammonia (and optionally other gaseous substances and optionally dust particles) from the air from the space, the livestock is a hero. It is reasoned that the ammonia release from the treated manure may be higher at least in some, than from untreated manure. In particular in such a case, the air treatment system is advantageous. Ammonia can be removed from air by passing the air through an acidic aqueous solution, such as a sulphuric acid solution (pH, e.g., about 1 to about 2). This allows recovery of ammonia, which is a useful nitrogen source. The scrubber solution may be used to reduce the pH of the manure, e.g., shortly before spreading out the manure (see above). A filter system may in particular be present to remove dust. An adsorbent may also be used, e.g., to remove ammonia.

The invention will now be illustrated by the following examples.

Example 1

An aqueous solution of 0.02 wt. % calcium hydroxide is prepared. The pH is about 11.7. 5% of the volume or an empty manure vault or a livestock stable is filled with the aqueous solution. Thereafter, livestock are heroes in the stable and produced faeces and urine collected in the vault. The contents of the vault are periodically agitated using a conventional agitation system for cattle manure. The pH is maintained above 10.0 until the vault is essentially full with treated manure. HCN concentrations are maintained below hazardous levels.

Example 2

Example 1 is repeated with sodium carbonate (soda). An aqueous solution of 0.23 wt. % soda is prepared. The pH of the solution is about 11. The pH is maintained above 10.4 until the vault is essentially full with treated manure. HCN concentrations are maintained below hazardous levels.

Example 3

Example 1 is repeated with an aqueous solution or 0.02 wt. % sodium hydroxide. The pH is about 11.7. The pH is maintained above 10.0 until the vault is essentially full with treated manure. HCN concentrations are maintained below hazardous levels.

Example 4

Example 1 is repeated with magnesium hydroxide. A saturated solution is made, which has a pH of about 10.6. When the vault is essentially full, the pH has dropped below 10.0.

Claims (21)

CONCLUSIONS 1. Method for reducing a health risk to humans or livestock due to exposure to blue acid (HCN) released from manure, which method involves bringing manure into contact with an alkaline substance, where an effective amount of An alkaline substance is used so that the pH of a mixture of the manure and the alkaline substance - when mixed - is at least 10.0. Method according to Claim 1, wherein the pH of the manure, after mixing with the alkaline substance, is 10.2 or higher, in particular in the range 10.4 - 11.5. 10 Method according to Claim 1 or 2, wherein treatment of the manure with the alkaline substance takes place in a manure cellar of a cattle farm. Method according to Claim 3, wherein the alkaline substance is added to the manure cellar before the manure is added. 15 Method according to Claim 3 or 4, wherein the manure is brought into contact with an aqueous solution of the alkaline substance in the manure cellar without significant active mixing. Method according to any of the preceding claims, wherein treatment of the manure with the alkaline substance in a closed vessel, 20 in which manure is stored, such as a silo, takes place. A method according to any of the preceding claims, wherein at least one alkaline substance, that is from the group consisting of calcium hydroxide (Ca (OH) 2), sodium hydroxide (NaOH), soda (Na 2 CO 3). magnesium hydroxide (Mg (OH) 2), potassium hydroxide (KOH) and potassium Carbonate (K 2 CO 3), is selected, is used. The method of Claim 7, wherein calcium hydroxide is in any case one of the selected alkaline substances. A method according to any of the preceding claims, wherein the manure is treated with an alkaline aqueous solution of the alkaline substance, said solution preferably having a pH of at least 11.0, even more preferably a pH of at least 11.5. Method according to any of the preceding claims, wherein the manure is cattle manure. A method according to any of Claims 1-10, wherein the manure is pig manure. 12. Livestock farming with a covered space, such as a shed, in which livestock can be kept, which space has a floor with openings, for example a grid through which manure can pass, and with at least mainly a manure cellar provided with an aqueous solution of a alkaline substance with a pH of at least 10.5, or manure treated with an alkaline substance, the treated manure having a pH of at least 10.0. Livestock farming, optionally according to Claim 12, with a covered space, such as a shed, in which livestock can be kept, which space has a floor with openings, for example a grid through which manure can pass, and with at least substantially underneath a manure cellar, which manure cellar can contain an alkaline substance, and which manure cellar is provided with a manure discharge, to which discharge a channel, such as a pipe or tube, for transferring the manure from the manure cellar to a manure storage tank, such as a silo, is connected, manure storage vessel of a dosing system for supplying an alkaline substance thereto. Livestock farming as claimed in Claim 12 or 13, wherein a dosing system for supplying alkaline substance to the manure cellar or manure vessel is present, which dosing system comprises a vessel provided with a stirrer for dissolving alkaline matter in water, and which vessel is higher then at least the floor of the manure cellar or the underside of a manure tank is arranged and has a drain in or near the bottom of said tank, which drain is connected to a channel for transfer to the manure cellar or a manure tank. Livestock farming according to Claim 12, 13 or 14, wherein a dosing system for supplying the manure cellar or a manure vessel with alkaline substance is present, which dosing system comprises a vessel provided with a stirrer for dissolving alkaline material in water wherein the vessel has a curvaceous bottom, in particular a bottom with two radii of curvature (e.g. according to DIN 28011), in which bottom there is a drain for the alkaline substance dissolved in water, which discharge is placed such that the dissolved alkaline substance is a channel which is situated between the drain and the manure cellar, respectively, a manure vessel, and which channel is arranged such that the dissolved alkaline substance from the drain of the aforementioned vessel can enter the manure cellar, respectively a manure vessel. turn into. A livestock farm according to any of Claims 12-14, wherein the livestock farm comprises an air treatment system for removing ammonia (and possibly other gaseous substances and possibly dust particles) from the air in the room in which the livestock is kept. Livestock farming according to Claim 16, wherein the air treatment system comprises one or more units selected from the group of gas washers, adsorbents and filters. 18. Use of an alkaline substance to reduce the risk of fatal accidents in a livestock farm as a result of exposure to hydrocyanic acid (HCN) released from manure and involving people or livestock. 19. Use of an alkaline substance to reduce the (average) concentration of hydrocyanic acid (HCN) in the air, which is present in a room in which livestock is kept, or which is present in a storage tank containing manure. Use according to Claim 18 or 19, wherein at least one alkaline substance from the group consisting of calcium hydroxide (Ca (OH) 2), sodium hydroxide (NaOH), soda (Na 2 CO 3), magnesium hydroxide (Mg (OH) 2) , potassium hydroxide (KOH) and potassium carbonate (K 2 CO 3) exists. The use according to Claim 20, wherein calcium hydroxide is used. Title: Reducing health risk to humans or livestock due to exposure of hydrogen cyanide (HCN) released from manure