METHOD FOR PRODUCING A FERTILISER AND FERTILISER COMPOSITION

Abstract

A method of producing a fertilizer composition, the method comprising: (a) providing a composition comprising ammonia; and (b) contacting the composition provided in step (a) with: (i) a composition comprising carbon dioxide; and (ii) a source of sulfate ion; and (iii)cellulosic fibres.

Claims

1. A method of producing a fertiliser composition, the method comprising: (a) providing a composition comprising ammonia; (b) contacting the composition provided in step (a) with: (i) a composition comprising carbon dioxide; (ii) a source of sulfate ion; and (iii) cellulosic fibres.

2. The method according to claim 1 wherein the composition provided in step (a) comprises an anaerobic digestate.

3. The method according to claim 2 wherein the composition provided in step (a) comprises an anaerobic digestate and from 30 to 40 wt% ammonia.

4. The method according to claim 1 wherein the composition comprising carbon dioxide used in step (b)(i) is a gaseous composition.

5. The method according to claim 4 wherein the composition comprising carbon dioxide comprises the exhaust gases from the combustion of a fossil fuel.

6. The method according to claim 4 wherein the composition comprising carbon dioxide comprises biogas.

7. The method according to claim 1 wherein step (b)(iii) involves adding a compost material comprising cellulosic fibres to the mixture obtained in step (a).

8. The method according to claim 1 wherein the source of sulfate ion comprises gypsum.

9. The method according to claim 1 which further involves adding a source of nitrate ions.

10. The method according to claim 1 which further involves adding a source of phosphorus.

11. The method according to claim 1 wherein step (b)(iii) is carried out before step (b)(i) and step (b)(ii).

12. A method according to claim 1 wherein step (b)(iii) is carried out after step (b)(i) and step(b)(ii).

13. A method according to claim 1 which further involves a step (c) of pelletising the material obtained after steps (b).

14. A fertiliser composition obtained by the method of claim 1.

15. A method of increasing the nutrient content of a plant growing medium, the method comprising: (a) providing a composition comprising an ammonia; (b) contacting the composition provided in step (a) with: (i) a composition comprising carbon dioxide; (ii) a source of sulfate ions; and (iii) cellulosic fibres; (c) optionally pelletising the material obtained after steps (b); and (d) admixing the mixture obtained after steps (b) and/or (c) with the plant growing medium.

Description

Example 1

[0163] A sample of 640 ml of water containing 360 g (4.56 mol) of NH.sub.4HCO.sub.3 was taken from a stock solution of ammonium bicarbonate formed by the bubbling carbon dioxide through ammonia solution. The temperature of the solution was 13° C. and the pH of solution was ca. 8 (tested with pH paper). 392.6 g (2.28 mol) of CaSO.sub.4.square-solid.2H.sub.2O was slowly added into the NH.sub.4HCO.sub.3 aqueous solution portion by portion over 1 hour and 25 min with vigorous stirring.

[0164] With addition of CaSO.sub.4.square-solid.2H.sub.2O into the solution, a lot of bubbles was produced which is CO.sub.2 gas. The pH and temperature were monitored time by time through the reaction process. After CaSO.sub.4.square-solid.2H.sub.2O addition was complete, the temperature had increased to 15.8° C. and the pH had dropped to 6-7 (tested with pH paper). The reaction mixture was stirred overnight (24 h) until no bubbles were observed. The solid collected by filtration and dried in air for a week to obtain 258.6 of white caked solid.

[0165] One part of the resultant mixture was admixed with two parts of an anaerobic digestate solid cake comprising partially decomposed organic matter including cellulosic fibres.

[0166] The material was then pelletized using a Farm feeds mini press into 5 mm diameter pellets.

[0167] These pellets were then incorporated at a rate of 5 wt% and 10 wt% into the growing media used for the production of lupins.

[0168] FIG. 1 shows the roots of two plants. The plant on the left was grown in a medium comprising 5 wt% of the fertiliser pellets. The plant on the right was grown in a medium comprising 10 wt% of the fertiliser pellets. It can be clearly seen that the plants, especially the roots, have produced a positive growth response to the increasing presence of the fertiliser pellets.

Example 2

[0169] The fertiliser of the present invention prepared according to example 1 was compared with a standard commercially available ammonium nitrate fertiliser.

[0170] Equivalent amounts of the inventive fertiliser and the comparative material were spread over adjacent plots on which oil seed rape were grown.

[0171] The crop yield per hectare was measured for various concentrations of fertiliser.

[0172] The results are shown in FIG. 2. The x-axis indicates the amounts of fertiliser applied in units of kgN/Ha.

[0105] For example, in some embodiments the source of nitrate may comprise a waste stream from the ODDA/nitrophosphate process. Such a waste stream will also comprise phosphate residues thus providing a source of phosphorous in the fertiliser composition obtained by the method of the invention.

[0106] In some embodiments the source of nitrate may comprise waste from the scrubbing of combustion exhausts with nitric acid.

[0107] In some embodiments the source of nitrate ion is nitric acid.

[0108] In some embodiments the source of nitrate ion is calcium nitrate provided by the reaction of wood ash and nitric acid.

[0109] Preferably the source of nitrate is added after steps (b)(i), (b)(ii) and (b)(iii).

[0110] In some embodiments the method of the present invention further involves adding a source of phosphorus.

[0111] The source of phosphorus may be added at any stage. Suitable sources of phosphorous include the incinerated bones of animals.

[0112] The source of phosphorus may be added before, after or during step (a); and/or before, during or after step (b)(i); and/or before, during or after step (b)(ii); and/or before, during or after step (b)(iii).

[0113] Phosphorus may be present in an anaerobic digestate provided in step (a) and/or step (b)(ii).

[0114] A waste stream from the ODDA/nitrophosphate process may be used to provide a source of nitrate and a source of phosphorus.

[0115] Further or alternative sources of phosphorus may be also added.

[0116] The material obtained following steps (a) and (b) of the method of the present invention can be used directly as a fertiliser composition and is highly nutritious. It contains many of the minerals that plants need for growth. It also provides a useful means of storing carbon dioxide.

[0117] This product obtained after steps (a) and (b) can be used directly as a fertiliser or can be further processed to provide an easier to handle form.

[0118] In some embodiments the method of the present invention involves a further step (c) of further processing the material obtained in steps (b). The further processing step (c) may involve drying, pulverising and/or granulating the material. Such processing methods will be known to the person skilled in the art.

[0119] Preferably step (c) involves pelletising the material obtained after steps (a) and (b). It has been advantageously found that this material is easily pelletised, especially in embodiments in which step (b)(iii) is carried out after steps (b)(i) and (b)(ii). The pellets do not clump together and spread as readily as leading commercially available fertiliser compositions of the prior art.

[0120] Step (b)(i) of the method of the present invention is exothermic and the method may further involve capturing the heat obtained in step (b)(i). This heat can be reused elsewhere in the process, for example to assist a drying step or it can be used in external processes.

[0121] Advantageously the present invention does not require high temperatures and pressure to be used. Suitably a temperature of less than 80° C. and a pressure of less than 20 bar is maintained throughout the process. At a temperature of around 80° C. a pressure of less than 2 bar, for example about 1 bar may be maintained throughout the process.

[0122] Thus the method of the first aspect of the present invention may in some embodiments be carried out at ambient pressure.

[0123] According to a second aspect of the invention there is provided a fertiliser composition obtained by the method of the first aspect.

[0124] Preferred features of the second aspect are as defined in relation to the first aspect.

[0125] Further preferred features of the first and second aspects of the present invention will now be described.

[0126] The fertiliser composition provided by the present invention suitably comprises at least 3 wt % of nitrogen, suitably at least 5 wt%, preferably at least 10 wt%. Suitably the fertiliser composition provided by the present invention comprises up to 32 wt% nitrogen, preferably up to 30 wt%, for example up to 20 wt%.

[0127] In some embodiments the composition comprises from 3 to 5 wt% nitrogen.

[0128] In some embodiments the composition comprises from 5 to 10 wt% nitrogen.

[0129] In some embodiments the composition comprises from 10 to 15 wt% nitrogen.

[0130] Suitably the composition comprises 2 to 10 wt% sulfur.

[0131] The composition of the present invention preferably comprises one or more further plant nutrients, for example potassium or phosphate.

[0132] In some embodiments the composition comprises 2 to 15 wt% potassium.

[0133] In some embodiments the composition comprises 2 to 15 wt% phosphate.

[0134] The present invention offers significant advantages in that it uses multiple waste products to generate a useful fertiliser composition. For example the present invention can make use of an anaerobic digestate which is generally considered unsuitable for direct use as a fertiliser, as it is in the form of a sludge and thus difficult to apply. By admixing with cellulosic fibres along with other components, an easier to handle solid fertiliser composition having an improved nutrient composition is provided. Furthermore the invention can make use of the biogas produced during anaerobic digestion. Thus the present invention can be put into effect at a location where anaerobic digestion is taking place.

[0135] For example the present invention may use the anaerobic digestate from animal waste wherein the animal waste is not separated from organic matter admixed therewith prior to digestion. For example sawdust or silage which is mixed with animal waste may be added to an anaerobic digester. The animal manure may be digested under anaerobic conditions but the cellulose or other organic matter present in the sawdust or silage may not be fully digested. However the resultant mixture comprising an anaerobic digestate and partially decomposed organic matter could be used in the present invention.

[0136] The partially decomposed organic matter is suitably provided in solid form. However it may be wet and it may be already admixed with a digestate composition. The present invention could thus find particular use on a farm where animal waste is processed by anaerobic digestion. Thus the present invention may provide a method of preparing a fertiliser composition comprising selecting a mixture of animal waste and a solid organic material; adding enzymes to effect anaerobic digestion of animal waste and collecting the biogas produced therefrom; admixing the digestate and solid organic material with a source of sulfate and ammonia; and contacting the biogas with the resultant mixture.

[0137] A further advantage of some fertiliser compositions of the present invention is that they may be used on soil which has been certified as organic.

[0138] The present inventors have tested products of the present invention and have found them to be as effective as a leading major fertiliser composition.

[0139] In some preferred embodiments the composition is obtained by admixing partially decomposed organic matter comprising cellulosic fibres with aqueous ammonia, gypsum, carbon dioxide and a liquid anaerobic digestate.

[0140] Suitably the fertiliser is provided by admixing these components in the following ratios by weight: [0141] 30 to 60, preferably 40 to 50 parts partially decomposed organic matter comprising cellulosic fibres; [0142] 5 to 20, preferably 10 to 15 parts liquid anaerobic digestate; [0143] 2 to 15, preferably 5 to 10 parts carbon dioxide; [0144] 10 to 25, preferably 12 to 20 parts gypsum; and [0145] 10 to 30 parts, preferably 15 to 25 parts aqueous ammonia.

[0146] An aqueous ammonia used herein typically comprises 5 to 25, suitably 15 to 20 wt% ammonia.

[0147] The present invention may further provide the use of a mixture of partially decomposed organic matter comprising cellulosic fibres, an anaerobic digestate, a source of sulfate ion, ammonia and carbon dioxide as a fertiliser, preferably as a fertiliser for organically certified soil.

[0148] The invention may suitably provide the use of a mixture of partially decomposed organic matter comprising cellulosic fibres, aqueous ammonia, gypsum, carbon dioxide and a liquid anaerobic digestate as an organic fertiliser.

[0149] According to a third aspect of the present invention there is provided a method of increasing the nutrient content of a plant growing medium, the method comprising: [0150] (a) providing a composition comprising an ammonia; [0151] (b) contacting the composition provided in step (a) with: (i) a composition comprising carbon dioxide; (ii) a source of sulfate ions; and (iii) cellulosic fibres; [0152] (c) optionally pelletising the material obtained after steps (b); and [0153] (d) admixing the mixture obtained after steps (b) and/or (c) with the plant growing medium.

[0154] Steps (a), (b) and (c) of the method of the third aspect are preferred as defined in relation to the first aspect and preferred features of the first aspect apply to the third aspect.

[0155] The invention may be used to increase the nutrient content of any suitably plant growing medium.

[0156] Suitable plant growing media will be known to the person skilled in the art and include for example soil, compost, clay, coco, and peat.

[0157] Preferably the plant growing medium is soil.

[0158] Preferably in step (d) the mixture obtained after steps (b) and/or (c) is admixed with the plant growing medium in an amount of from 1 to 50 wt%, preferably 5 to 20 wt%.

[0159] As previously described herein the present invention offers significant advantages. In particular the combination of components used in the invention provides a solid fertiliser composition which is easy to handle and easy to pelletise.

[0160] Furthermore the inclusion of cellulosic fibres provides a solid matrix on which plant nutrients can be retained. This helps maintain the nutrients in the region of plant roots when applied to soil and reduces leaking and evaporation.

[0161] Thus the fertiliser compositions of the invention provide improved availability of nutrients to the roots of a plant. Using the present invention nutrients can be delivered in an efficient and beneficial way.

[0162] The invention will now be further described with reference to the following non-limiting examples.