Compositions, and methods and uses relating thereto

Abstract

A fertiliser composition comprising a cellulosic material having a lignin content of at least 8 wt% and urea or a source thereof, preferably in a weight ratio of 100:1 to 1:10. The cellulosic material

Description

The present invention relates to fertiliser compositions, in particular fertiliser compositions comprising urea. Urea is commonly included in fertiliser compositions as a source of nitrogen. However the presence of urease enzymes in soil can quickly cause degradation of the urea present in these compositions. This causes a number of problems. As well as the reduced availability of nutrients to plants, the degradation of urea by urease produces ammonia and carbon dioxide which may be released into the atmosphere. The release of such gases is highly undesirable. Aqueous ammonia may also run off the land into nearby rivers and streams. Globally, around 43% of atmospheric ammonia is attributed to the volatilisation from soils due to over application of chemical fertilisers in agriculture. The emissions of nitrogen based gases from agricultural chemical fertiliser can also include nitrous oxides. Ammonia can negatively impact the environment, increasing soil pH, cause damage to human health, cause increases in eutrophication and biodiversity loss. Nitrous oxides have a high global warming potential, of 300. This means that nitrous oxides warm the earth 300 times more than carbon dioxide. Due to high volatilisation of fertiliser compositions containing urea and the associated release of ammonia, governments are introducing legalisation to mandate the inclusion of a urease inhibitor in fertiliser compositions comprising urea. However introducing a urease inhibitor into soil can lead to other deleterious effects as the urease present in soil provides a number of useful functions. The loss of nitrogen containing compounds through leaching can also cause significant problems. The presence of nitrogen salts in waterways can cause eutrophication and a reduction in biodiversity. The reduction in nutrient levels in the soil due to leaching can cause crop deficiencies leading to farmers applying move fertiliser and exacerbating the problem. It is an aim of the present invention to provide a fertiliser composition comprising urea which is not readily lost due to volatilisation and / or run off. According to a first aspect of the invention there is provided a fertiliser composition comprising: (a) a cellulosic material having a lignin content of least 8 wt%; and (b) urea or a source thereof. According to a second aspect of the present invention there is provided a method of preparing a fertiliser composition, the method comprising admixing (a) a cellulosic material having a lignin content of at least 8 wt% with (b) urea or a source thereof. According to a third aspect of the present invention there is provided a fertiliser composition prepared by the method of the second aspect. Preferred features of the first, second and third aspects of the invention will now be described. Component (a) is a cellulosic material having a lignin content of at least 8 wt%. Any suitable cellulosic material having a lignin content of at least 8 wt% may be used. Component (a) suitably comprises a waste material. In some embodiments the cellulosic material may comprise an anaerobic digestate, an aerobic digestate or a mixture thereof. In such embodiments the digestate material is a material obtained by anaerobic digestion of organic matter. Suitably the digestate material is obtained by the anaerobic digestion of a waste product. In preferred embodiments component (a) does not comprise an anaerobic digestate or an aerobic digestate. Suitably the fertiliser composition of the first aspect does not comprise an anaerobic digestate, an aerobic digestate or a mixture thereof. Preferably the cellulosic material having a lignin content at least 8 wt% is a waste product from agriculture. Preferably component (a) is selected from wood, straws, husks, maize and mixtures thereof. In some embodiments the cellulosic material having a lignin content of at least 8 wt% is a straw material. Suitably component (a) may comprise wheat straw, barley straw, oat straw, rye straw, rice straw or mixtures thereof. A preferred straw is wheat straw. In some embodiments the cellulosic material may comprise husk. Suitable husks include wheat husk, barley husk, corn husk, sunflower husk, nut husk, rice husk, cocoa husk and mixtures thereof. A preferred husk is cocoa husk. In some embodiments component (a) may comprise whole crop maize. Component (a) may comprise a cellulosic material having a lignin content of at least 9 wt%, preferably at least 10 wt%. In some embodiments component (a) may comprise a cellulosic material having a lignin content of at least 11 wt% or at least 12 wt%. In some embodiments component (a) may comprise a cellulosic material having a lignin content of up to 15 wt% or up to 20 wt%. In some embodiments component (a) may be dried before use. Preferably the cellulosic material comprises straw, husk or a mixture thereof. This is suitably dry. The cellulosic material may be chopped, milled, diced or macerated prior to use. Preferably the cellulosic material used in the present invention has a moisture content of less than 20 wt%, preferably 5 to 18 wt%. Preferably component (a) comprises less than 10 wt% pyrolyzed material, preferably less than 5 wt%, suitably less than 1 wt%, for example less than 0.1 wt% or less than 0.01 wt%. Preferably component (a) does not comprise a pyrolyzed material. Component (b) comprises urea or a source thereof. Component (b) may comprise neat urea or a composition comprising urea and one or more further components. For example, in some embodiments component (b) may comprise a solution of urea. In some embodiments component (b) may comprise a waste material comprising urea. Preferably component (b) comprises neat urea in solid form. Preferably component (b) is provided in particulate form. Component (a) and / or component (b) may comprise a mixture of materials. Preferably the weight ratio of cellulosic material having a lignin content of at least 8 wt% to urea is from 100:1 to 1:10; preferably from 50:1 to 1:5; more preferably from 20:1 to 1:3; suitably from 10:1 to 1:2; preferably from 5:1 to 1:1.5; more preferably from 3:1 to 1:1. In embodiments in which component (a) comprises a mixture of cellulosic materials, the above ratio refers to the total amount cellulosic material having a lignin content of at least 8 wt%. The amount of urea referred to is the amount active urea compound. The above amounts do not include any diluent, carriers, byproducts or impurities which may be present. In some embodiments the fertiliser composition of the first aspect may comprise one or more further components. In some embodiments the method of the second aspect of present invention may involve the admixing of one or more further components with components (a) and (b). Preferably the one or more further components provides a further source of one or more nutrients. In some embodiments the one or more further components comprises a waste material. In some preferred embodiments the fertiliser composition of the first aspect may further comprise (c) an alkaline earth metal compound. In some preferred embodiments the method of the second aspect comprises the admixture of component (a), component (b) and (c) an alkaline earth metal compound. Preferably component (c) comprises a salt of magnesium and / or calcium. Preferred salts are carbonates. Most preferably component (c) comprises a calcium magnesium carbonate salt, preferably MgCa(CO3)2 or dolomite. Preferably component (c) is present in the fertiliser composition in an amount of up to 5 wt%; preferably up to 3 wt%; more preferably up to 1 wt% based on the total weight of components (a), (b) and (c). Suitably component (c) is present in an amount of from 0.001 to 1 wt%, preferably from 0.01 to 1 wt% based on the total weight of components (a), (b) and (c). In preferred embodiments components (a), (b) and (c) together provide at least 30 wt% of the fertiliser composition of the first aspect, preferably at least 50 wt%. In preferred embodiments components (a), (b) and (c) together provide at least 30 wt% of the fertiliser composition provided by the method of the second aspect, preferably at least 50 wt%. In some embodiments components (a), (b) and (c) together provide from 50 wt% to 100 wt%, for example from 70 to 100 wt% of the fertiliser composition of the first aspect. In some embodiments components (a), (b) and (c) together provide from 50 wt% to 100 wt%, for example from 70 to 100 wt% of the fertiliser composition provided by the second aspect. In some embodiments components (a), (b) and (c) together provide from 50 wt% to 90 wt% of the fertiliser composition of the first aspect. In some embodiments components (a), (b) and (c) together provide from 50 wt% to 90 wt% of the fertiliser composition provided by the second aspect. In some embodiments the composition may comprise up to 15 wt% of a source of sulfur, preferably a source of sulfate. A preferred sulfate is calcium magnesium sulfate. In some embodiments the composition may comprise a source of potassium. The material obtained by admixture of a cellulosic material comprising at least 8 wt% lignin, urea and optionally an alkaline earth metal compound can be used directly as a fertiliser composition and is highly nutritious. It contains many of the minerals that plants need for growth. This product can be used directly as a fertiliser or can be further processed to provide an easier to handle form. In some embodiments the method of the second aspect of the present invention involves the steps of: (i) admixing components (a), (b) and optionally (c); and (ii) further processing the material obtained in step (i). Step (i) involves admixing components (a), (b) and optionally (c). Components (a), (b) and (c) may be mixed in any order. In some embodiments components (a) and (b) may be mixed followed by the addition of component (c). In some embodiments component (a) may be mixed with component (c) prior to the addition of component (b). In some embodiments component (b) may be mixed with component (c) prior to the addition of component (a). In preferred embodiments components (a), (b) and (c) are concurrently added to a reaction vessel. Any suitable reaction vessel may be used. Such vessels will be known to the person skilled in the art, and include, for example, hoppers or ribbon blenders. Suitably components (a), (b) and, when present, (c) are admixed within the reaction vessel during step (i). They may be rotated, or otherwise agitated and air may be blown through the vessel. Step (i) of the method of the second aspect may involve chopping, dicing or pulverising components (a) and / or (b) and / or (c) as they are mixed. In some embodiments the mixture of components (a), (b) and, when present, (c) may be heated or cooled during step (i). Preferably the mixture of components (a), (b) and optionally (c) is not heated in step (i). Preferably the mixture of components (a), (b) and optionally (c) is not cooled in step (i). In preferred embodiments the method of the second aspect of the present invention does not involve a heating step. Preferably the method of the second aspect of the present invention does not involve a cooling step. Preferably the method of the second aspect of the present invention does not involve a pyrolysis step. Preferably the method of the second aspect of the present invention does not involve a fermentation step. Preferably the method of the second aspect of the present invention does not involve a composting step. The method of the second aspect of the present invention may be carried out as a batch process or as a continuous process. Preferably the method of the second aspect involves a continuous process. The method of the second aspect of the present invention may include a step (ii) of further processing the material obtained in step (i). The further processing step (ii) may involve drying, pulverising and / or granulating the material. Such processing methods will be known to the person skilled in the art. In some embodiments step (ii) involves dying the material obtained in step (i). Preferably step (ii) involves pelletising the material obtained after step (i). In such embodiments the reaction mixture may be directed from a mixing vessel, such as a hopper or ribbon blender into a pelletising machine. Heat may be released during pelletisation. It has been advantageously found that the material obtained after step (i) is easily pelletised. The pellets do not clump together and spread as readily as leading commercially available fertiliser compositions of the prior art. The fertiliser composition provided by the present invention suitably comprises at least 3 wt % nitrogen, suitably at least 5 wt%, preferably at least 8 wt% for example at least 10 wt%. Suitably the fertiliser composition provided by the present invention comprises up to 40 wt% nitrogen, preferably up to 30 wt%, for example up to 25 wt% or up to 20 wt%. In some preferred embodiments the composition comprises from 12 to 18 wt% nitrogen. The composition of the present invention preferably comprises one or more further plant nutrients, for example potassium and / or phosphate. Preferably the fertiliser composition provided by the present invention comprises less than 10 wt% pyrolyzed material, preferably less than 5 wt%, suitably less than 1 wt%, for example less than 0.1 wt% or less than 0.01 wt%. Preferably the fertiliser composition does not comprise a pyrolyzed material. The present invention offers significant advantages in that it can use one or more waste products to generate a useful fertiliser composition. For example the present invention can make use of straw and / or husks from the processing of agricultural products. By admixing with other components, an easier to handle solid fertiliser composition having an improved nutrient composition is provided. Preferably the method of the second aspect of the present invention does not involve the addition of carbon dioxide. Preferably the method of the second aspect of the present invention does not involve the addition of sulfate salts. Preferably the method of the second aspect of the present invention does not involve the addition of nitrate salts. Whilst small amounts of sulfates, nitrates and carbon dioxide may be present in components (a), (b) and / or (c), in preferred embodiments additional sources of these are not added. Preferably the method of the second aspect of the present invention does not involve the addition of a base. Preferably the method of the second aspect of the present invention does not involve the addition of an acid. A particular advantage of the present invention is that urea is not readily degraded in the fertiliser composition provided by the present invention. Preferably less than 50 wt% of urea presents in the fertiliser composition degradation, volatilisation and / or run off within 7 days of application to soil. is lost due to Preferably less than 30 wt% of urea presents in the fertiliser composition degradation, volatilisation and / or run off within 7 days of application to soil. is lost due to Preferably less than 50 wt% of urea presents in the fertiliser composition degradation, volatilisation and / or run off within 14 days of application to soil. is lost due to Preferably less than 30 wt% of urea presents in the fertiliser composition degradation, volatilisation and / or run off within 14 days of application to soil. is lost due to The present inventors have tested products of the present invention and have found them to be as effective as a leading major fertiliser composition, whilst releasing much lower levels of ammonia into the environment. According to a fourth aspect of the present invention there is provided a method of increasing the nutrient content of a plant growing medium, the method comprising the steps of: (i) admixing (a) a cellulosic material having a lignin content of at least 8 wt% with (b) urea of a source thereof and optionally (c) an alkaline earth metal salt; and (ii) optionally adding one or more additional components and / or further processing the material obtained in step (i); and (iii) admixing the mixture obtained after step (i) or (ii) with the plant growing medium. Steps (i) and (ii) of the method of the fourth aspect are preferably as defined in relation to the second aspect and preferred features of the first, second and third aspects apply to the fourth aspect. According to a fifth aspect of the present invention there is provided the use of a composition comprising (a) a cellulosic material having a lignin content of comprising at least 8 wt%; (b) urea or a source thereof; and optionally (c) an alkaline earth metal salt; as a fertiliser having reduced volatilisation. The composition used in the fifth aspect is preferably as define in relation to the first and / or third aspects. The present invention may be used to increase the nutrient content of any suitably plant growing medium. Suitable plant growing media will be known to the person skilled in the art and include for example soil, compost, clay, coco, and peat. Preferably the plant growing medium is soil. Preferably in step (iii) the mixture obtained after steps (i) and optionally (ii) is admixed with the plant growing medium in an amount of from 1 to 50 wt%, preferably 5 to 20 wt%, based on the mass of the plant growing medium. 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, easy to pelletise and does not readily release ammonia. The present inventors have also found that the fertiliser compositions of the present invention are effective even when applied at reduced levels of nitrogen. Advantageously, in addition to nitrogen, the compositions of the present invention deliver other nutrients to the soil that are not present in traditional chemical fertilisers, and improve the soil condition. The invention will now be further described with reference to the following non-limiting examples. Example 1 A fertiliser composition of the present invention (composition 1) was prepared as follows: 28.8 tonnes of wheat straw were combined with 11.6 tonnes of urea and 0.36 tonnes of dolomite over a 24-hour period in a ribbon blender. The wheat straw had a lignin content of 15 wt%. The mixture obtained was pelletised using a standard pellet mill to provide 6 mm pellets. Pelletisation was carried out under both low compression and high compression conditions. Hardness was measured at each end and the middle of the pellets and was found to be satisfactory to ensure that the pellets can be spread effectively using farm machinery. The hardness values are shown in tables 1 and 2: Table 1 - low compression pellets First end Hardness (Kg) Middle Hardness (Kg) Second end Hardness (Kg) Mean 14.3 Mean 8.8 Mean 11.5 Min 8 Min 4 Min 7 Max 24 Max 13 Max 15 Table 2 - high compression pellets First end Hardness (Kg) Middle Hardness (Kg) Second end Hardness (Kg) Mean 13.9 Mean 19.0 Mean 19.6 Min 10 Min 11 Min 11 Max 24 Max 24 Max 25 The pellets prepared under low compression condition had an average nitrogen content of 16.2 wt% and an average moisture level of 6.9 wt%. The pellets prepared under high compression condition had an average nitrogen content of 18.3 wt% and an average moisture level of 5.9 wt%. Example 2 A further fertiliser composition of the present invention (composition 2) was prepared following an analogous procedure to that set out in example 1 but using cocoa husks instead of wheat straw. The cocoa husks had a lignin content of 18 wt%. The fertiliser pellets obtained had a nitrogen content of 15 wt%. Three containers were filled with 50ml of sand and 50ml of soil which was well mixed. Pellets of composition 2 were added to the first container (A), ground up pellets of composition 2 were added to the second container (B) and urea ammonium nitrate fertiliser was added to the third container (C). The amount of fertiliser added in each case was selected to ensure the same amount of nitrogen was provided. 10ml of water was added immediately prior to closing the containers. The lids of the containers were connected to Draeger simultaneous testing adapters selected to measure ammonia emissions in ppm by weight. The containers were allowed to stand for 7 weeks with readings taken each day. The results are shown in figure 1. Example 3 A field trial was conducted to assess the effectiveness of pellets of composition 2 as a fertiliser compared with urea ammonium nitrate (UAN) ora high urea concentration fertiliser (urea). Wheat was drilled on 11 October and left germinate over the winter. Two applications of fertiliser were made on 8 March and 26 March. The crop was harvested on 5 August. The fertiliser compositions were applied in each case to provide an equivalent concentration of nitrogen. The results are shown in table 3: Table 3 Composition N content of composition (% wt) Total dose of N (kg / ha) 1st dose of N (kg / ha) 2nd dose of N (kg / ha) Yield (T / ha) None 0 0 0 0 9.20 2 15 50 25 25 10.37 2 15 100 50 50 11.32 2 15 150 75 75 11.69 2 15 200 100 100 11.78 2 15 250 125 125 11.43 UAN 34.5 50 25 25 9.59 UAN 34.5 100 50 50 10.17 UAN 34.5 150 75 75 10.66 UAN 34.5 200 100 100 11.46 UAN 34.5 250 125 125 11.41 Urea 46 50 25 25 9.82 Urea 46 100 50 50 10.44 Urea 46 150 75 75 11.12 Urea 46 200 100 100 11.67 Urea 46 250 125 125 11.53

Claims

1. A fertiliser composition comprising:(a) a cellulosic material having a lignin content of least 8 wt%; and(b) urea or a source thereof.

2. A method of preparing a fertiliser composition, the method comprising admixing (a) a cellulosic material having a lignin content of at least 8 wt% with (b) urea or a source thereof.

3. A composition or method according to claim 1 or claim 2 wherein component (a) comprises a straw selected from wheat straw, barley straw, oat straw, rye straw, rice straw or mixtures thereof.

4. A composition or method according to any preceding claim wherein component (a) comprises a husk selected from wheat husk, barley husk, corn husk, sunflower husk, nut husk, rice husk and mixtures thereof.

5. A composition or method according to any preceding claim wherein component (a) comprises a cellulosic material having a lignin content of at least 10 wt.

6. A composition or method according to any preceding claim wherein the weight ratio of cellulosic material having a lignin content of at least 8 wt% to urea is from 100:1 to 1:10.

7. A composition according to any of claims 1 or 2 to 7 which further comprises (c) an alkaline earth metal compound.

8. A method according to any of claims 2 to 6 wherein components (a) and (b) are admixed with (c) an alkaline earth metal compound.

9. A method according to any of claims 2 to 6 or 8 which involves the steps of:(i) admixing components (a), (b) and optionally (c); and(ii) further processing the material obtained in step (i).

10. A method according to claim 9 wherein (ii) involves pelletising the material obtained after step (i).

11. A fertiliser composition prepared according to the method of any of claims 2 to 6 or 8 to 10.

12. A method of increasing the nutrient content of a plant growing medium, the method comprising the steps of:5 (i) admixing (a) a cellulosic material having a lignin content of at least 8 wt% with (b)urea of a source thereof and optionally (c) an alkaline earth metal salt; and(ii) optionally adding one or more additional components and / or further processing the material obtained in step (i); and(iii) admixing the mixture obtained after step (i) or (ii) with the plant growing medium.1013. The use of a composition comprising (a) a cellulosic material having a lignin content of comprising at least 8 wt%; (b) urea or a source thereof; and optionally (c) an alkaline earth metal salt; as a fertiliser having reduced volatilisation.A

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