METHOD OF PRODUCING A FERTILISER COMPOSITION AND FERTILISER COMPOSITION PRODUCED THEREBY

Abstract

A method of producing a fertiliser composition, the method comprising: (a) providing partially decomposed organic matter; (b) contacting the organic matter with: (i) an anaerobic digestate; (ii) a source of nitrate ion; (iii) a source of ammonia; and (c) contacting the mixture obtained in step (b) with a source of carbon dioxid. Also claimed is a fertiliser composition comprising partially decomposed organic matter admixed with an anaerobic digestate, a source of nitrate ion, a source of ammonia and carbon dioxide.

Claims

1. A method of producing a fertiliser composition, the method comprising: (a) providing partially decomposed organic matter; (b) contacting the organic matter with: (i) an anaerobic digestate; (ii) a source of nitrate ion; (iii) a source of ammonia; and (c) contacting the mixture obtained in step (b) with a source of carbon dioxide.

2. A method according to claim 1 wherein the partially decomposed organic mater is compost or composting matter.

3. A method according to claim 1 wherein the partially decomposed organic matter comprises cellulosic fibres.

4. A method according to claim 1, wherein the anaerobic digestate is provided as an aqueous composition.

5. A method according to claim 1, wherein the source of nitrate ions is calcium nitrate.

6. A method according to claim 1, wherein step (b) involves preparing a composition comprising an anaerobic digestate and ammonia; contacting the partially decomposed organic matter with said composition; and contacting the partially decomposed organic matter with a source of nitrate.

7. A method according to claim 1, wherein the source of carbon dioxide is biogas and step (c) involves contacting the mixture obtained in step (b) with biogas.

8. A method according to claim 1, which includes a step (d) of drying, pulverising and/or granulating the material obtained in step (c).

9. A method according to claim 8 wherein step (d) involves pelletising the material obtained in step (c).

10. A fertiliser composition comprising partially decomposed organic matter admixed with an anaerobic digestate, a source of nitrate ion, a source of ammonia and carbon dioxide.

11. A composition according to claim 10 which comprises at least 12 wt % nitrogen.

12. A composition according to claim 10 which is in the form of pellets.

Description

EXAMPLE 1

[0078] Anaerobic digestion was carried out using the feedstock mixture detailed below. This will produce approximately 25000 tonnes of digestate per annum and a biogas having an average carbon dioxide concentration of 43%

TABLE-US-00001 Tonnes Dry Volatile Biogas yield per solids solids (m.sup.3/ Methane Feedstock annum (%) (%) tonne VS) percentage Grass silage 9,000 25% 90% 600 53% Chicken litter 2,000 55% 75% 480 55% Cattle slurry 7,000 8% 80% 380 55% Water 6,438

EXAMPLE 2

[0079] Anaerobic digestion was carried out using the feedstock mixture detailed below. This will produce approximately 18000 tonnes of digestate per annum.

TABLE-US-00002 Tonnes Dry Volatile Biogas yield per matter solids (m.sup.3/ Methane Feedstock annum (%) (%) tonne VS) percentage Maize Silage 1,703 33 96 623 53 Grass Silage 1,000 35 88 570 53 Wholecrop Rye 1,700 35 91 585 53 Energy Beet 1,300 22 92 700 51 Potato 300 22 93.64 727 52 Wheat Straw 300 86 91.68 371 51 Chicken Manure 2,600 40 80 431 65 Cattle Manure 1,000 25 80 451 55 (with straw) Pig Manure 1,000 25 88 367 60 Cattle Slurry 1,000 10 85 400 55

EXAMPLE 3

[0080] A fertiliser composition was prepared as follows:

[0081] Ammonium hydroxide in an anaerobic digestate liquid, and calcium nitrate was added to the solution. This mixture was fed into a bulk mixer containing a compost material, for 10 minutes. The mixture was then passed to a reaction auger where it was contacted in a counter current manner with a gas flow containing carbon dioxide at 30 C., for 5 minutes. The resultant material was passed to mixer where it was combined with superphosphate and potassium chloride and mixed for 5 minutes. The resultant material was pelletised to a size of 2-4 mm.

[0082] The resultant mixture contained by weight 18% ammonium hydroxide, 8% carbon dioxide, 15% calcium nitrate, 46% in total of composts and anaerobic digestate, 9% cellulosic fibre, 2% superphosphate, and 2% potassium chloride.

EXAMPLE 4

[0083] The effectiveness of the fertiliser of example 3 was tested on an established grazed grass sward as an experimental crop.

[0084] Methodology

[0085] The trial was designed as a randomised block layout, with three replicates (blocks), each with five rates of product application, one untreated control, and a comparison treatment of Nitram. Niatram is a proprietary fertiliser comprising ammonium nitrate. It is a market leader and is considered a standard treatment for grasslands. Nitram was applied at 60 kgN/ha which replicated normal field fertilisation practice.

[0086] The composition of example 3 was applied at a range of equivalent nitrogen (N) rates that bracketed the 60 kg N/ha field rate.

[0087] Treatments were as below. Niatram contains 34.5% nitrogen.

TABLE-US-00003 TABLE 1 Treatments Field rates (kgN/ha) 0 15.00 30.00 60.00 90.00 120.00 Product rate 0 107.14 214.29 428.57 53 857.14 (kgN/ha) at 14% N Product rate 0 0.46 0.91 1.82 53 3.64 (kg/plot) Treatment 1 2 3 4 5 6 number Nitram 60.00 51 (kgN/ha) Nitram 176.47 52 product (kg/ha) Nitram 0.75 product rate (kg/plot) Treatment 7 number

TABLE-US-00004 TABLE 2 Treatment layout Hedge/tree line Plot No's Block 1 101 102 103 104 105 106 107 5 7 3 2 6 4 1 Block 2 201 202 203 204 205 206 207 1 7 6 4 5 3 2 Block 3 301 302 303 304 305 306 307 Farm side 6 3 2 1 7 4 5 gate

[0088] The trial was set out on a relatively flat, well established sheep grazed field. Blocks were aligned at right angles to the most likely field production gradient, into the field from an adjacent hedge and woodland area. Each plot measured 8.5 m5 m; a total area of 42.5 m.sup.2.

[0089] Two, one metre gaps were set out between the three blocks to allow access to the plots.

[0090] Treatments were first applied on the 28th May, referred to as day zero in the graphs and tables below.

[0091] Relative Chlorophyll Levels

[0092] Assessments were made of relative chlorophyll levels (roughly equivalent to greenness) with a Field Scout CM 1000 remote chlorophyll sensor.

[0093] Yield

[0094] Yield assessments were conducted by periodic sampling using a petrol driven 35 cm cut width cylinder lawnmower to traverse across the longer, 8.5 m width of each plot, providing a unit sampling area of 2.98 m.sup.2, conducted as either single or multiple passes as conditions varied across the season. Cuttings were collected and fresh weights measured shortly after their harvest. Dry weights were measured approximately 24 hrs later after drying to constant weight at 65 C. Plots were kept in a mown condition by cutting the entire trial site down to a uniform level for further sampling when sufficient re-growth had taken place. Frequency of cut for yield estimation was determined by weather and extent of grass growth. Six measurements were completed throughout the growing season, spanning a 98 day post application period.

[0095] Aerial Photography

[0096] A remotely operated quad-copter or drone was used to capture aerial photographs of the trial site from an altitude of approximately 120 feet. Images were processed by GIMP or ImageJ software to correct for distortion from the wide angle lens of the drone camera. Further image processing was then undertaken to measure average pixel values across at least 75% of each plot by digitally outlining an area of interest with the computer cursor. RGB and L*a*b* colour spaces were examined using ImageJ software. The green channel of RGB data was analysed for mean pixel intensity.

[0097] Root, Soil Carbon and Nitrogen

[0098] Soil cores were taken on the 1st October, 127 days after treatment application. Four replicate samples were taken from each plot, one for carbon and nitrogen analysis and three for root mass measurement. Samples were extracted with a hand held soil corer, to a depth of 10 cm, which removed a core with a volume of approximately 57 ml.

[0099] As the trial site was a previously a grazed permanent pasture, there was a considerable layer of both living, and dead and decaying plant tissue at the surface which made the true soil level indistinct. However the soil surface was estimated carefully and all remaining above ground tissue was cut away prior to further sample processing. Root mass estimation was made following thorough soaking of the trimmed cores and washing through a 1 mm aperture sieve to filter and collect roots, followed by drying in air at 55 C. No distinction was made between living and dead tissue.

[0100] Carbon and nitrogen contents were estimated by drying the samples, mixing each thoroughly, and grinding to a fine powder. Concentrations were measured using an Elementar vario EL cube CNS automated elemental analyser.

[0101] Statistical Analysis

[0102] Results were analysed through analysis of variance (ANOVA) and by statistical analysis of correlation coefficients of application rate response curves.

[0103] Results

[0104] Chlorophyll Index

[0105] The series of measurements indicated a statistically significant positive response to the product of example 3, throughout the season. This is illustrated by way of example in FIG. 1 which shows the chlorophyll index obtained after using the product of example 3 and that obtained after using Nitram, on day 54 of the trial.

[0106] Yield

[0107] Yield was measured on six occasions throughout the main growth period. In all cases a positive trend was apparent. Weather conditions and sample intervals sometimes gave rise to non-statistically significant effects but the cumulative yield, over the 98 day observation period, gave a highly significant result of increasing yield with increasing application rate of the product of example 3. FIG. 2 shows the cumulative grass dry weight yield to day 98 of the trial.

[0108] Aerial Photography

[0109] Aerial observations supported data obtained from both relative chlorophyll levels and yield estimates. A trend of increasing green colour intensity was associated, at a statistically significant level, with increasing application rates of the product of example 3.

[0110] Root Mass, Soil Carbon and Nitrogen Content

[0111] Root mass measurements suggest that there was a positive response to the application of the product of example 3.

[0112] Overall the results of the trial showed that the product of example 3 performed at least as well and in some cases better than a fertiliser composition of the current leading commercial product, Nitram.

[0113] The fertiliser composition of the present invention offers the added advantages of being prepared from waste materials and thus offers significant environmental benefits.

EXAMPLE 5

[0114] The spreading of the fertiliser pellets example 3 was tested independently using a Kuhn Axis 30.1 spreader on grass. The height of application was set at 60 cm from the bottom of the frame and a spreadwith of 24 m was used. Spreading was tested on grass at a rate of 200 Kg/Ha with a forward speed of 10 Km/h. The coefficient of variation (CV) measures the accuracy of the spread pattern. For fertilisers a CV of 15% (as recommended in EN13739-2) should be attainable in field conditions. For the tested pellets of the present invention a CV of 7.29 was achieved. FIG. 3 shows the amount of pellets obtained in pots placed at successive 1 m intervals from the centre of application to a distance of 12 m in each direction. This illustrates that the spreading pattern achieved was consistent and met required standards.