Use of carbon black for soil conditioning

Abstract

Carbon black can be used for soil conditioning, e.g. to promote growth of plants, to promote soil drainage, and to prevent erosion, evaporation, and silting up. The carbon back is worked into the topsoil.

Claims

1. A process of soil conditioning, including: (i) providing 2 to 500 tons/ha of hydrophobic carbon black on a topsoil of an agricultural field, and (ii) working the hydrophobic carbon black into the topsoil.

2. The process according to claim 1, wherein the hydrophobic carbon black is worked into the topsoil to a soil depth of at least 3 cm.

3. The process according to claim 2, wherein the hydrophobic carbon black is worked into the topsoil homogeneously.

4. The process according to claim 1, wherein the hydrophobic carbon black is worked into the topsoil up to a soil depth of 10 cm.

5. The process according to claim 1, wherein a carbon content of the hydrophobic carbon black is 95 to 99.5 weight-%.

6. The process according to claim 1, wherein the hydrophobic carbon black is a hydrophobic material with a contact angle of water droplets of greater than 70.

7. The process according to claim 1, wherein 5 to 20 tons/ha of the hydrophobic carbon black are provided on the topsoil of the agricultural field.

8. The process according to claim 1, wherein a particle size of the hydrophobic carbon black is 1 nm to 1 m.

9. The process according to claim 1, wherein pellets of the hydrophobic carbon black have a particle size of 0.3 to 8 mm.

10. The process according to claim 1, wherein the hydrophobic carbon black supports at least one different organic or inorganic additive.

11. The process according to claim 1, wherein a carbon content of the hydrophobic carbon black is 80 to 99.8 weight %.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The Figure shows the placement of carbon black in pot trials with maize in an Application A, an Application B, and an Application C.

DETAILED DESCRIPTION OF THE INVENTION

(2) Carbon black is well known in the state of the art and e.g. described in Ullmann, Encyclopedia of Industrial Chemistry or in Kirk-Othmer Encyclopedia of Chemical Technology. The carbon black is typically characterized in ASTM classifications.

(3) Carbon black is a commercial form of aggregates of carbon particles. Carbon black typically contains more than 95% pure carbon with minimal quantities of oxygen, hydrogen and nitrogen. In the manufacturing process, carbon black particles are formed that range from 10 nm to approximately 500 nm in size. These fuse into chain-like aggregates, which define the structure of individual carbon black grades.

(4) The carbon content of the carbon black is preferably 80 to 99.8 weight-%, more preferred 85 to 99.5 weight-%, even more preferred 90 to 99.5 weight-%, even more preferred 95 to 99.5 weight-%. Typically, the impurities of the carbon black are: S in the range of 0 to 2 weight-%, preferably 0 to 1 weight-%, more preferably 0 to 0.5 weight-%. H2 in the range of 0 to 10 weight-%, preferably 0 to 5 weight-%, more preferably 0 to 2 weight-%, more preferably 0 to 1 weight-%. O in the range of 0 to 2 weight-%, preferably 0 to 1.5 weight-%, more preferably 0 to 1 weight-%, more preferably 0 to 0.5 weight-%. N in the range of 0 to 5 weight-%, preferably 0 to 3 weight-%, more preferably 0 to 2 weight-%, more preferably 0 to 1 weight-%.

(5) Typically, the density of the carbon black is in the range of 1 to 3 g/cc, preferably 1 to 2 g/cc, preferably 1.5 to 2 g/cc (particle density). Typically, the bulk density of the carbon black is in the range of 0.01 to 0.75 g/cc, preferably 0.05 to 0.5 g/cc, more preferably 0.1 to 0.25 g/cc.

(6) Typically, the specific surface area of the carbon black measured by Hg porosimetry (DIN66133) is in the range of 5 to 1500 m2/g, preferably 10 to 1000 m2/g, preferably 10 to 500 m2/g, preferably 10 to 250 m2/g, more preferably 10 to 200 m2/g, even more preferably 20 to 150 m2/g.

(7) The carbon black is preferably a hydrophobic material with a preferred contact angle of water droplets of greater than 70, preferably greater than 80, more preferably greater than 90.

(8) Plasma carbon black as known in the art can be used as carbon black in this invention.

(9) In one embodiment, carbon black can be used directly, as produced via the plasma process, with a primary particle size of preferably 1 nm to 1 m, more preferred 5 to 500 nm more preferred 10 to 300 nm.

(10) In another embodiment, carbon black can be used as pellets with a particle size of preferably in the range of 0.3 to 8 mm, preferably 0.5 to 5 mm, more preferable 1 to 4 mm. Pelleting of carbon black is well known in the state of the art, typically, water can be used as binder.

(11) The soil conditioner can be used in a quantity ranging from 0.5 to 500 tons per ha, preferably 2 to 200 tons per ha, more preferably 5 to 20 tons per ha.

(12) Preferably, the carbon black is worked into the soil of up to 50 cm soil depth, even more preferably up to 30 cm soil depth, even more preferably up to 20 cm soil depth, even more preferably up to 10 cm soil depth, even more preferably up to 5 cm soil depth, even more preferably up to 3 cm soil depth. Preferably, the carbon black is worked in the topsoil of at least 3 cm soil depth, more preferably at least 5 cm soil depth, even more preferable at least 10 cm soil depth.

(13) Preferably, the carbon black is worked in the topsoil homogeneously.

(14) The techniques to work carbon black into the topsoil are known in the art, e.g. with soil tillage equipment.

(15) In addition, the invention relates to a mixture of soil and carbon black comprising 0.25 to 25 weight-% carbon black (w/w) (soil composition comprising 0.25 to 25 weight-% carbon black), preferably 0.5 to 20 weight-%, even more preferably 1 to 15 weight-%, even more preferably 1 to 10 weight-%, even more preferably 1 to 7.5% weight-%. even more preferably 1 to 5% weight-%, even more preferably 1 to 2.5% weight-%.

(16) Optionally, further components are added to the mixture of soil and carbon black, preferably one or more different organic or inorganic additives, e.g. agrochemical active substance from the group of fungicides, bactericides, herbicides and/or plant growth regulators.

(17) Optionally, the soil conditioning substrate can be mixed with other commonly used soil conditioning substrates like fertilizer, liming material, commonly known soil improver, growing medium, inhibitor and/or plant biostimulant as regulated by the Regulations (EU) 2019/1009 and applied as a mixture. Optionally, the particle size of the soil conditioning substrate can be adapted to the co-conditioning substrate, e.g. via classifying.

(18) Optionally, the carbon black can support different organic or inorganic additives, e.g. agrochemical active substance from the group of fungicides, bactericides, herbicides and/or plant growth regulators.

(19) Advantages:

(20) A soil conditioner for the topsoil has now been found. Thus, the carbon black can directly be used as a soil conditioner without any pelleting step.

(21) Surprisingly and in contrast to WO 2012/15313, the present soil conditioner reduces the dust formation of the soil and hence diminish vulnerability by wind erosion, which is a great problem of dry soil without vegetation worldwide.

(22) By mixing the soil with carbon black, both the soil is easier to till, and the soil clumps are easily decomposed to smaller aggregates. Thus, this soil is easier to work with in the agricultural sector, e.g. by harrow, ploughing or other means like rake. Reduction in power needed for soil cultivation after soil is amended with Carbon Black results in saving of fossil fuel and hence CO2 emissions.

(23) In addition, the carbon black can remain in the soil without being converted into carbon dioxide.

EXAMPLE

(24) 1. Characteristics:

(25) In the experiments, different applications of carbon black were tested:

(26) TABLE-US-00001 TABLE 1a Characteristic of the carbon black Carbon black (Cancarb Thermax N990 ultra pur) Carbon content >95 wt. % Particle size 280 nm BET 10.3 m2/g Density 1.7-1.9 g/cc

(27) TABLE-US-00002 TABLE 1b Characteristics of Biochar Biochar 2 Biochar 3 Biochar 4 Biochar 1 Made from Root Made from Made from Made from of vine Green cutting Wheat straw Spruce wood (Hochschule (Hochschule (Hochschule (Prodana Geisenheim Geisenheim Geisenheim Biochar GmbH) University) University) University) Carbon 86 wt.-% ** ** ** content Particle 1-2 mm ** ** 1-2 mm size BET 58.9 m2/g ** ** 113 m2/g Lang- 82.1 m2/g ** ** 156 m2/g muir surface Density <1* 1.13 0.01 0.95 0.13 <1* (g/cm3) Bulk 0.227 ** ** 0.187 Density (g/cm3) *floating on the surface even if the solution contained a wetting agent **no data available yet

(28) TABLE-US-00003 TABLE 1c Characteristic of the granular pyrolytic carbon granular pyrolytic carbon Carbon content 98 wt.-% Particle size 1.5-2.0 mm BET <0.10 m2/g Density 1.98 g/cc

(29) The granular pyrolytic carbon was produced by decomposition of natural gas and deposition on calcined petroleum coke carrier material (the carrier having a particle size of 0.5-2.5 mm, a sulfur content of 1.1 wt.-% and a real density in xylene of 2.09 g/cm3) in a fluidized bed at temperatures from 1100-1300 C. and at pressures from 1-2 bar(abs).

(30) BET: measured as described in DIN ISO 9277

(31) Density: The specific weight (density) was determined by the Archimedes principle in pure water (see Wikipedia). Part of the experiments were done in water amended with a wetting agent to lower the surface tension of the water so that also hydrophobic particles may sink into the water if the specific weight is 1 g/cc.

(32) Bulk Density: ASTM C559 Standard test method for bulk density by physical measurement of manufactured carbon and graphite articles

(33) 2. Wind Erosion

(34) Experimental set-up: Installation of a wind tunnel with a gradient of different wind speeds from 0 km/h to 7 km/h (measured with Lechler Pocketwind IV Hand Aerometer, which was placed on inverted Petri dishes, on which the materials (carbon black, Biochar 1, Biochar 4) were also applied).

(35) 2.1 Wind Speed

(36) The inverted petri dishes, on which 1.5 g of material was placed, was placed in the wind tunnel and the wind speed was increased.

(37) TABLE-US-00004 TABLE 2 Wind speed from which the first particles were blown away from the petri dishes Wind speed Carbon black 3.6 km/h Biochar 1 1.6 km/h Biochar 4 1.4 km/h
2.2 Loss of Material

(38) An inverted petri dishes, on which 1.5 g of material was placed, was placed in the wind tunnel at a wind speed of 6.4 km/h. After 5 min of wind exposure, the material remained on the petri dishes was weighed.

(39) TABLE-US-00005 TABLE 3 Material remained on the petri dishes after 5 min wind exposure material remained on material remained on the petri dishes [g] the petri dishes [%] Carbon black 1.38 g 93% Biochar 1 0.58 g 39% Biochar 4 0.54 g 36%

(40) Covering the topsoil with carbon black reduces the erosion effects by wind.

(41) 3. Dust Formation

(42) The dust formation of carbon black (CB), Pyrolysis Carbon (PC), air dried soil Limburgerhof, and mixtures of CB and PC with air dry soil Limburgerhof was quantified under standardized condition by the device DustView II from Palas GmbH, Karlsruhe, Germany according to the guidelines of the manufacturer (https://www.palas.de/product/dustview2).

(43) 30 g of material is dropped from 750 mm height and dust formation quantified as extinction of a laser beam in the dust room (0=no dust formation, 100=maximal light extinction due to dust). The dust number is the integral of the light extinction over a time span of 30 sec. For each sample three measurements were conducted, and the results statistically evaluated by the Analysis of variance.

(44) TABLE-US-00006 TABLE 4 Dust Formation Calculated via Dust number of the mix- tures from the com- Mean measured Standard ponents assuming dust number deviation additive interactions Soil Limburgerhof 71.7 5.9 Pyrolytic carbon (PC) 2.4 0.5 Carbon black (CB) 3.7 1.1 Soil with 2.44% 58.7 8.5 70.0 (w/w) PC Soil with 1.23% 34.8 1.9 70.8 (w/w) CB Soil with 2.44% 27.1 3.1 70.0 (w/w) CB Soil with 4.76% 21.9 1.6 68.4 (w/w) CB

(45) The measured dust number of air-dry soil Limburgerhof is much higher than of PC or CC alone, with PC being lower than CC. Mixtures of the soil with PC and CB reduce dust formation significantly. However, if the low intrinsic dust formation of PC in the mixture with soil is taken into account, the low dust number of soil with 2.44% PC of 70.0 is statistically not different from the untreated soil (71.75.9).

(46) But, with an increasing amount of CC added to soil (1.23, 2.44, 4.67% by weight) dust formation decreases significantly, which cannot be explained by a dilution effect as in the case of PC.

(47) Thus CC, but not PC, has an intrinsic strong effect in reducing dust formation of dry soil as additive.

(48) 4. Soil Clumps and Soil Cultivation, Workability of the Soil

(49) Soil Oberding (silt loam, pH(CaCl2)) 7.5) without soil additives and treated with 8 t/ha barbon black (applied around one year prior to the assessment of surface structure) were compared for the presence of soil clumps (soil aggregates) two weeks after the soils were uniformly raked. Four soil sites (0.35 m.sup.2 each) were randomly chosen from each treatment and photographed. On the print-out with a ruler the clumps >40 mm in length and 10 mm to 40 mm in length were counted and calculated as numbers per m.sup.2. By Analysis of Variance the significance in differences were calculated among the soil treatments.

(50) TABLE-US-00007 TABLE 5 Presence of soil clumps after raking Number of soil Number of soil clumps >40 clumps >10 mm per m2; mm to <40 mm mean, SD per m2; mean, SD Soil without carbon black 18.4, 11.4 57.7, 2 9.1 Soil with 8 t/ha carbon black 6.8, 3.7 19.8 2.5 Soil with 8 t/ha pyrolytic 19.9 6.3 49.8 11.2 carbon

(51) Soil clumps >40 mm in length are 60% less if the soil is treated with carbon black (P=0.10), while soil clumps 10 mm und <40 mm are 66% less (P=0.04).

(52) Moreover, the physical power needed for soil cultivation was less in the soil amended with Carbon black compared to the untreated soil. An effect on soil clumps and workability of soil could not be seen after the addition of granular pyrolytic carbon.

(53) Summing up, significant soil effects by addition of carbon black could be surprisingly detected on soil physics, which was not the case for pyrolysis carbon.

(54) 5. Ability of Water Absorption

(55) At the beginning, the samples were dried down. The air humidity was gradually increased from 0%-90% in 10% steps, whereas the criterion for next stage was the mass fluctuation <0.05% in 45 min.

(56) TABLE-US-00008 TABLE 6 Water absorption Water ab- Start value End value sorption rel. air rel. air Temp- Sample [wt.-%] humidity Duration humidity erature Carbon black 0.031% 0% 147 h 70% 25 C. Biochar 1 7.25% 0% 147 h 70% 25 C. Biochar 4 12.5% 0% 147 h 70% 25 C. Pyrolytic 0.0023% 0% 147 h 70% 25 C. carbon

(57) Table 6 shows the low water absorption of carbon black and pyrolytic carbon compared to biochar due to the low surface area and the hydrophobic surface.

(58) 6. Formation of Biomass:

(59) Application (see the FIG.) and Testing Methods

(60) Pot Trial with Maize:

(61) Soil Limburgerhof (loamy sand, pH 6.8) was used to fill into so called Mitscherlich pots filled with 6.4 kg dry soil each pot. As a basal fertilization each pot received 99 mg Mg as MgSO47 H2O, and 0.436 g P and 1.1 g K as K2HPO4, and 1 g N as NHNO3.

(62) The carbon samples were either uniformly mixed with the soil (Application A), uniformly mixed with 1 kg of soil which was placed on top of the other unamended 5.4 kg of soil (Application B), or the carbon samples were placed on top of the soil after the maize plants had emerged nine days after seeding (Application C), see the Figure.

(63) With 314 cm.sup.2 soil surface per pot 2, 4, 8, 16 t C/ha equals 6.3, 12.5, 25, 50 g C/pot, respectively.

(64) Six seeds of Zea mays (L.) cv. Amadeo were seeded per pot (5 Jun. 2019). After emergence plants were first thinned to uniformly three plants per pot and later to one plant per pot, which then was cultivated until maturity. As a second dress the pots were fertilized with 1 g N as NH4NO3 and finally as a third dress each pot received 6.7 g of the complex fertilizer Nitro-phoska perfect (15+5+20S+2+8+ trace elements) on June 28.

(65) Each carbon black treatment had 4 replicates, the untreated control had all in all 8 replicates. The pots were placed fully randomized on a conveyor table in the vegetation hall Limburgerhof which has been described by Jung (1967).

(66) From Monday to Friday the pots were watered two times a day after weighing to 70% of the maximum water holding capacity of the soil. (The differences in weight of the pots due to the addition of the carbon samples were taken into account by extra weight.) On Saturday and Sunday pots were watered horticulturally according to need without weighing.

(67) The harvest took place on October 2nd by dividing the shoot into the cob and the rest of the plant so that both total dry matter (Tab. 7) and cob dry matter (Tab. 8) could be determined after drying the plant biomass in a forced oven at 80 C. until constant weight.

(68) Application A: uniform mixing with the whole soil of the used plant pot (0-15 cm, 6.4 kg soil)

(69) Application B: uniform mixing with the top soil (0-3 cm, 1 kg soil)

(70) Application C: mulch on top of the soil, 9 days after emergence of plants.

(71) The Figure: Application A, B, C and placement of carbon black in pot trials with maize.

(72) Comparison of Test Results

(73) TABLE-US-00009 TABLE 7 Total shoot dry matter per maize plant and pot in gram as mean of n replicates, standard deviation and as percentage of untreated control = 100%. For the distribution of carbon black (application) see FIG. 1. indicate no variant. Carbon Carbon Carbon Carbon App- black black black black lication Control (2 t/ha) (4 t/ha) (8 t/ha) (16 t/ha) A 105.2 5.9 113.2 4.1 117.6 5.3 115.7 13.2 116.4 4.7 (n = 8) (n = 4) (n = 4) (n = 4) (n = 4) (100%) (108%) (112%) (110%) (110%) 115.7 7.2 (n = 16) (110%) B 105.2 5.9 108.0 13.8 110.5 5.5 102.0 6.6 (n = 8) (n = 4) (n = 4) (n = 4) (100%) (103%) (105) (97x%) 106.8 9.3 (n= 12) (101%) C 105.2 5.9 104.3 13.0 (n = 8) (n = 4) (100%) (99%)

(74) TABLE-US-00010 TABLE 8 Maize-cob dry matter per plant and pot in gram as mean of n replicates, standard deviation and as percentage of untreated control = 100%. For the distribution of carbon black (application) see FIG. 1. indicate no variant. Carbon Carbon Carbon Carbon App- black black black black lication Control (2 t/ha) (4 t/ha) (8 t/ha) (16 t/ha) A 67.2 5.0 74.6 2.5 79.4 3.6 77.8 9.6 76.9 3.8 (n = 8) (n = 4) (n = 4) (n = 4) (n = 4) (100%) (111%) (118%) (116%) (111%) 77.2 5.3 (n = 16) (115%) B 67.2 5.0 70.6 7.2 75.0 4.2 67.0 6.2 (n = 8) (n = 4) (n = 4) (n = 4) (100%) (105%) (112) (100%) 70.9 6.4 (n = 12) (106%) C 67.2 5.0 66.9 8.8 (n = 8) (n = 4) (100%) (98%)

(75) Surprisingly, the applications A shows much better results than application B and C.

(76) Biodegradability:

(77) The biodegradability was tested by measuring the soil respiration after addition of carbon black at an application rate of 313 mg per 50 g soil (soil Limburgerhof; loamy sand, pH 6.8) what is equivalent to some 2 t C/ha. Soil without additions or with the addition of 50 mg ground wheat straw to 50 g soil (0.32 t/ha) were controls. The soil respiration was measured with WTW Ox-iTop (Weilheim, Germany) placed in incubators at 20 C. according to the method outlined by Robertz et al. (1999) and Malkomes and Lemnitzer (2009).

(78) In Tab. 8 it can be seen that the straw caused a strong soil respiration while carbon black did not cause any CO2 evolution higher than the unamended soil.

(79) TABLE-US-00011 TABLE 9 Soil respiration (CO2 emission) of soil Limburgerhof cumulated over time at 20 C. without or with addition of straw or carbon black; MW = mean value, n = 4, SD = standard deviation. Soil without Straw ground Carbon black Incubation C addition (0.32 t C/ha) (2 t/ha) time Soil respiration [mg CO2-C/50 g dry soil, cumulated] [weeks] MW SD MW SD MW SD 1 0.7 0.2 19.1 0.7 0.8 0.2 2 1.5 0.3 26.3 0.8 1.7 0.3 3 2.4 0.3 29.5 0.8 2.6 0.3 4 3.1 0.4 31.7 0.8 3.3 0.4 5 3.7 0.4 33.4 0.8 4.0 0.4 6 4.3 0.4 34.7 0.8 4.5 0.5 7 4.9 0.5 35.0 0.3 5.2 0.5 8 5.5 0.5 35.4 0.2 5.8 0.6 9 6.0 0.5 35.7 0.2 6.3 0.6 10 6.4 0.6 36.4 0.2 6.8 0.6 11 7.0 0.6 36.9 0.2 7.3 0.7 12 7.4 0.6 37.2 0.3 7.7 0.7 13 7.8 0.6 37.5 0.4 8.1 0.7 14 8.4 0.6 37.5 0.7 8.7 0.7 15 8.9 0.6 38.6 0.9 9.2 0.7 16 9.4 0.6 39.6 1.0 9.6 0.8 17 9.9 0.6 40.5 1.1 10.1 0.7

REFERENCES

(80) Jung, J. (1967): Eine neue Vegetationshalle zur Durchfhrung von Gefversuchen. Z. Acker-u. Pflanzenb. 126, 293-297. Malkomes, H.-P., Lemnitzer, B. (2009): Vergleich der mittels URAS und OxiTop Control gemessenen Substrat-induzierten Kurzzeitatmung im Boden beim mikrobiologisch-kotoxikolog-ischen Monitoring von Pflanzenschutzmitteln. I. Einfluss eines Herbiziden Referenzmittels und eines Neutralsalzes, Nachrichtenblatt Deutscher Pflanzenschutzdienst, 60, 104-112. Robertz, M., Muckenheim, Th., Eckl, S., Webb, L. (1999): Kostengnstige Labormethode zur Bestimmung der mikrobiellen Bodenatmung nach DIN 19737, Wasser & Boden, 51/5, 48-53.