Detoxification of the herbicide clopyralid by heat treatment

Abstract

To provide biochar containing a thermal decomposition product of clopyralid, which reduces the risk of clopyralid while retaining the value of livestock feces as an organic fertilizer, a method for producing the biochar, and a method for decomposing clopyralid.SOLUTION: To provide biochar containing a pyrolysate of clopyralid. It is a further aspect of the present invention to provide the biochar as described above, wherein the pyrolysate of clopyralid is a solid material obtained by heat treatment at a temperature of 140 °C or higher. In addition, the present invention provides a method for producing biochar, the method comprising heat-treating livestock excrement containing clopyralid or a biomass raw material containing the same at a temperature of 140 °C or higher under oxygen-free or oxygen-poor conditions.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a fertilizer in the agricultural field suitable for application to agricultural land, specifically to biochar containing a pyrolysate of clopyralid, a method for producing the same, and a method for decomposing clopyralid. [Background technology]

[0002] Livestock manure contains many fertilizer components and can be used to make livestock manure compost, which is also expected to have soil improving effects. Livestock manure compost increases organic matter in the soil, which serves as food for microorganisms and earthworms in the soil, stimulating their activity. As a result, soil improvement effects are achieved, such as making the soil fluffy and improving drainage and water retention. This effect allows crops to grow healthily and ensures stable harvests.

[0003] However, in recent years, cases of growth disorders occurring when using cow manure compost in vegetable and flower cultivation have been reported (Non-Patent Documents 1 and 2). Research into the causes of these disorders has suggested that clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) in the feed and cow manure compost is the cause (Non-Patent Documents 3-6). Clopyralid is a component of a herbicide used for various purposes in the United States, Australia, Canada, and other countries, including grass and grain production, as well as lawn and forest management. Although it is used overseas, it is not registered as a pesticide in Japan (Non-Patent Document 7). However, in Japan, imported grass and other feed containing clopyralid is often fed to livestock. Clopyralid is excreted intact in livestock manure and urine, and is relatively stable and slowly decomposed during the composting process (Non-Patent Documents 6 and 8). Therefore, it has been reported that residual clopyralid in compost can cause growth disorders in sensitive vegetables and flowers such as cherry tomatoes, sweet peas, and chrysanthemums (Non-Patent Documents 9 and 10).

[0004] It has been reported that clopyralid can be decomposed by an advanced oxidation process (AOP), which combines oxidizing agents such as zero-valent iron, hydrogen peroxide, and ozone with ultraviolet irradiation (Non-Patent Documents 11-15). However, it is practically difficult to apply such advanced chemical treatments to the large amounts of livestock manure that are generated on a daily basis. Furthermore, it has been reported that compost containing less than 0.01 mg / kg of clopyralid can be produced by mixing fertilizer derived from fermented animal manure with cow manure contaminated with clopyralid at a weight ratio of 25% or more and composting the mixture (Patent Document 1). However, when using such fermented animal manure-derived fertilizer, it is expected that it will be produced in-house or purchased from a distributor, and both methods pose problems such as labor and procurement costs. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6976627 [Non-patent literature]

[0006] [Non-Patent Document 1] National Agriculture and Food Research Organization (NARO) 2009a. Simple method for determining herbicide residues in feed and compost and manual for damage mitigation measures [homepage on the Internet]. National Agriculture and Food Research Organization, Livestock and Grassland Science Institute, Tsukuba City; [cited 28 January 2020]. Available from URL: http: / / www.naro.affrc.go.jp / publicity_report / publication / pamphlet / techpamph / 011167.html [Non-patent document 2] Ministry of Agriculture, Forestry and Fisheries. 2018b. Survey results on clopyralid contained in imported feed and compost in fiscal year 2017 [homepage on the Internet]. Ministry of Agriculture, Forestry and Fisheries, Tokyo; [cited 28 January 2020]. Available from URL: http: / / www.maff.go.jp / j / seisan / kankyo / clopyralid / attach / pdf / clopyralid-33.pdf [Non-patent document 3] Uegaki R, Ebato M, Sutoh M, Cai Y. 2009. Use of liquid chromatography-tandem mass spectrometry for quantitative analysis of clopyralid in compost and forage. Grassland Science 55, 135-139. [Non-patent document 4] Saito R, Ikenaga O, Ishihara S, Shibata H, Iwafune T, Sato T, Yamashita Y. 2010. Determination of herbicide clopyralid residues in crops grown in clopyralid contaminated soils. Journal of Pesticide Science 35, 479-482. [Non-patent document 5] Sato, Tsuyoshi, Yoshida, Kiyoshi, Shigemori, Isao. 2010. Crop growth disorders caused by the herbicide clopyralid remaining in compost. Japanese Journal of Soil Science and Plant Nutrition 81, 158-161. [Non-patent document 6] Ebato M, Uegaki R, Sutoh M. 2015. Dynamics of clopyralidherbicide during composting in small composting experiment units. Journal of Pesticide Science 40, 184-190. [Non-Patent Document 7] Ministry of Agriculture, Forestry and Fisheries. 2018a. Response to the occurrence of growth disorders of horticultural crops, etc., suspected to be caused by clopyralid in compost derived from cow excrement, etc. [homepage on the Internet]. Ministry of Agriculture, Forestry and Fisheries, Tokyo; [cited 28 January 2020]. Available from URL: http: / / www.maff.go.jp / j / seisan / kankyo / clopyralid / attach / pdf / clopyralid-31.pdf [Non-patent document 8] Michel FC, Doohan D. 2003. Clopyralid and other pesticides in compost. The Ohio State University Extension Factsheet [homepage on the Internet]. The Ohio State University, USA; [cited 28 January 2020]. Available from URL: http: / / ohioline.osu.edu / aex-fact / pdf / 0714.pdf [Non-Patent Document 9] Namiki Sayuri, Seike Nobuyasu. 2017. Effects of clopyralid in soil on the early growth of tomatoes, snow peas, and sweet peas: Data collection [homepage on the Internet]. National Agriculture and Food Research Organization, Agro-Environmental Change Research Center, Tsukuba City; [cited 28 January 2020]. http: / / www.naro.affrc.go.jp / publicity_report / publication / pamphlet / tech-pamph / 078226.html [Non-Patent Document 10] Abe et al., 2021. Change of clopyralid concentration in recycled beef cattle compost, Animal Science Journal 92, e13568 [Non-Patent Document 11] Ferreira et al., 2020; Semitsoglou-Tsiapou et al., 2016; Rajah et al., 2019; Yang et al., 2021 [Non-Patent Document 12] Ferreira et al., 2020. Clopyralid degradation by AOPs enhanced with zero valent iron, Journal of Hazardous Materials, 392, 12282 [Non-Patent Document 13] Semitsoglou-Tsiapou et al., 2016. Low pressure UV / H2O2 treatment for the degradation of the pesticides metaldehyde, clopyralid and mecoprop - Kinetics and reaction product formation, Water Research 91, 285-294 [Non-Patent Document 14] Rajah et al., 2019. Clopyralid degradation using solar-photocatalytic / ozone process with olive stone activated carbon, Journal of Environmental Chemical Engineering 7, 102900 [Non-Patent Document 15] Yang et al., 2021. Sulfate radical-based oxidation of the aminopyralid and picloram herbicides: The role of amino group on pyridine ring, Journal of Hazardous Materials 405, 124181 Summary of the Invention [Problem to be solved by the invention]

[0007] Considering the current situation where plant growth is impaired when biomass materials such as compost containing residual clopyralid herbicide are spread on agricultural land, technology is needed to reduce the risks of clopyralid while preserving the value of livestock manure as organic fertilizer. [Means for solving the problem]

[0008] As a result of extensive research, the present inventors have found that clopyralid can be decomposed by subjecting biomass raw materials such as compost containing clopyralid to heat treatment at a relatively low temperature range, and have thus completed the present invention.

[0009] Therefore, the present invention includes the following aspects. <Biochar> [1] Biochar containing pyrolysate of clopyralid. [2] [1] Biochar according to [1], wherein the thermal decomposition product of clopyralid is a solid substance obtained by heat treatment at a temperature of 140°C or higher. [3] [1] Biochar according to the present invention, wherein the excrement is feces and urine. <Biochar manufacturing method> [4] A method for producing biochar, comprising heat treating livestock manure containing clopyralid or a biomass raw material containing said manure at a temperature of 140°C or higher under oxygen-free or oxygen-poor conditions. [5] The manufacturing method according to [4], wherein the heat treatment temperature is 140°C or higher and 220°C or lower. [5-2] The manufacturing method according to [4], wherein the biomass raw material is compost. <How clopyralid is broken down> [6] A method for decomposing clopyralid, comprising heat treating livestock excrement containing clopyralid or a biomass raw material containing the same at a temperature of 140°C or higher under anoxic or oxygen-poor conditions. [7] The decomposition method according to [6], wherein the temperature of the heat treatment is 140°C or higher and 220°C or lower. [7-2] The decomposition method according to [6], wherein the biomass raw material is compost. [Effects of the Invention]

[0010] It has already been shown that applying carbonized materials to agricultural land contributes to increased crop yields, and applying carbonized heat-treated livestock manure to agricultural land is expected to not only decompose any clopyralid present, but also have the same or even greater effect as compost. In other words, the biochar of the present invention can be used as an agricultural material. [Brief explanation of the drawings]

[0011] [Figure 1] As for the thermal decomposition behavior of clopyralid, Figure 1(a) is a graph showing the results of thermogravimetry (TG), Figure 1(b) is a graph showing the results of derivative thermogravimetry (DTG), and Figure 1(c) is a graph showing the results of differential thermal analysis (DTA). [Figure 2] Figure 2A is a photograph (CK) showing snow peas grown with cow manure that does not contain clopyralid, Figure 2B is a photograph (T300) showing the growth status of snow peas 31 days after they were grown with cow manure containing clopyralid that had been heat-treated at 300°C, Figure 2C is a photograph (T150) showing the growth status of snow peas grown in the same manner but heat-treated at 150°C, Figure 2D is a photograph (T100) showing the growth status of snow peas grown in the same manner but heat-treated at 100°C, and Figure 2E is a photograph (T0) showing the growth status of snow peas grown in the same manner but without heat treatment. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Biochar> In one aspect, the present invention relates to biochar containing a solid material obtained by thermal treatment of clopyralid, preferably at a temperature of 140°C or higher, and more preferably at a temperature of 140°C or higher but not higher than 220°C.

[0013] In the present invention, clopyralid refers to a compound of the formula: [ka] It is an ingredient in herbicides that are used for various purposes overseas, such as in the production of grasses and grains, in countries such as the United States, Australia, and Canada, but is not registered as a pesticide in Japan. However, in recent years, cases have been reported in Japan where growth disorders have occurred when cow manure compost is used in vegetable and flower cultivation, and research into the cause of these disorders has revealed that clopyralid in the feed and cow manure compost is the cause.

[0014] In the present invention, the term "thermal decomposition product of clopyralid" refers to a decomposition product of clopyralid by heat treatment, specifically, a solid substance obtained by heat treatment at a temperature of 140°C or higher, more preferably at a temperature of 140°C or higher and 220°C or lower, under oxygen-free or oxygen-poor conditions. The "heat treatment" in the present invention is considered to be applicable over the widest temperature range, for example, 50-1000°C, and particularly 200-350°C. As described above, the heat treatment in the present invention is low-temperature carbonization, preferably at a temperature of 140°C or higher, more preferably at a temperature of 140°C or higher and 220°C or lower.

[0015] In the present invention, "anoxic or oxygen-deficient conditions" refers to an environment or atmosphere in which the target substance (livestock manure containing clopyralid or a biomass material containing it) does not completely combust during heat treatment. Specifically, heat treatment under anoxic conditions refers to heat treatment in which the target substance is placed in an inert gas atmosphere such as nitrogen gas, while heat treatment under oxygen-deficient conditions refers to heat treatment in which the target substance is placed in an oxic atmosphere but does not completely combust, resulting in decomposition products after heat treatment.

[0016] In the present invention, "biochar" refers to a carbonized material obtained by heat-treating biomass raw materials under oxygen-free or oxygen-deficient conditions, and its application to agricultural land is expected to improve crop productivity and have environmental conservation effects. Biochar is a lightweight, black residue consisting of carbon and ash that remains after pyrolysis of biomass, and is also called biochar. An important feature of the biochar of the present invention is that it eliminates harmful clopyralid while retaining its value as an organic fertilizer from livestock manure. In the present invention, "biochar" can be obtained by heat treatment at a temperature of 140±10°C or higher, preferably 140°C-220°C.

[0017] <Biochar manufacturing method> In another aspect, the present invention relates to a method for producing biochar, which comprises heat-treating livestock manure containing clopyralid or a biomass material containing the same, such as compost, at a temperature of 140°C or higher under anoxic or oxygen-deficient conditions. The temperature is not particularly important as long as it is 140±10°C or higher, and the upper limit can be any temperature. Preferably, the method for producing biochar is characterized by heat-treating at a temperature of 140°C to 220°C.

[0018] In this embodiment of the present invention, "clopyralid," "pyrolysate of clopyralid," "anoxic or oxygen-deficient conditions," and "biochar" are as defined above. According to the biochar production method of the present invention, useful biochar in which clopyralid contained in biomass raw materials, such as compost, has been effectively decomposed can be produced stably in a short time and at low cost. That is, the production method of the present invention can provide useful biochar as an agricultural material in a short time and at low cost without requiring large-scale capital investment. This advantage contributes to carbon negativity, a state in which the amount of greenhouse gases such as CO2 emitted into the atmosphere by industrial activity is less than the amount absorbed by forests, etc. This could be a countermeasure against global warming.

[0019] In the present invention, the starting material "livestock-derived excrement containing clopyralid or a biomass material containing the same" means livestock-derived excrement containing clopyralid or a biomass material containing the excrement. The livestock referred to in "excrement from livestock" includes chickens, pigs, cows, horses, sheep, goats, etc. The excrement in "excrement derived from livestock" refers to feces and urine excreted by livestock. Excrement generated during general livestock breeding contains leftover feed and, in the case of cattle, bedding such as sawdust and rice straw. Even if excrement contains substances other than feces and urine, it is still considered excrement in the present invention.

[0020] In the present invention, the term "biomass raw material" refers to compost and other renewable organic resources derived from living organisms, excluding fossil resources.

[0021] <How clopyralid is broken down> In another aspect, the present invention relates to a method for decomposing clopyralid, which comprises heat-treating livestock manure containing clopyralid or a biomass raw material (compost) containing the same at a temperature of 140°C or higher under anoxic or hypoxic conditions. In this aspect of the present invention, "clopyralid," "thermal decomposition product of clopyralid," "anoxic or hypoxic conditions," and "biochar" are as defined above. [Example]

[0022] The present invention will be described in detail below with reference to reference examples and examples, but it should be noted that these do not limit the scope of the present invention and are merely illustrative.

[0023] The materials and methods used in the examples are as follows. material and method

[0024] Example 1 Thermal decomposition behavior of clopyralid The thermal decomposition behavior of clopyralid was determined using a simultaneous thermogravimetry / differential thermal analysis (STM) instrument, which can simultaneously perform differential thermal analysis (DTA) and thermogravimetry (TG). Specifically, 10 mg of clopyralid was placed in the device, and the atmosphere was thoroughly replaced with nitrogen. The device was heated to approximately 600°C at a rate of 10°C / min, and the presence or absence of weight loss and endothermic or exothermic reactions was confirmed.

[0025] The results are shown in Figure 1. Figure 1(a) shows the results of thermogravimetry (TG), Figure 1(b) shows the results of derivative thermogravimetry (DTG), and Figure 1(c) shows the results of differential thermal analysis (DTA). Thermogravimetry results indicated that clopyralid exhibited significant weight loss in the temperature range from approximately 140 to 220 °C, confirming its decomposition via some kind of reaction. Differential thermal analysis (DTA) revealed two downward-convex peaks with minimum values ​​near 150 and 180 °C. Considering that the downward-convex DTA peaks indicate endothermic reactions, this suggests that clopyralid melting and thermal decomposition occurred at 150 °C and thermal decomposition occurred near 180 °C. To efficiently decompose clopyralid, it is important to determine the temperature at which the thermal decomposition rate of clopyralid is maximized. To achieve this goal, we performed differential thermogravimetric analysis. A minimum peak was observed at 180°C, confirming that 180°C is the maximum thermal decomposition rate of clopyralid. Thermogravimetric analysis revealed continued weight changes even above 220°C, but this is due to further decomposition of the clopyralid pyrolysate. Based on these findings, thermal treatment at temperatures above 140°C under anoxic or oxygen-deficient conditions is feasible for clopyralid decomposition. Furthermore, given that decomposition of clopyralid is complete by approximately 220°C, a thermal treatment temperature between 140°C and 220°C is desirable.

[0026] Test Example 1 Residue test for clopyralid Cow manure containing clopyralid was prepared as a raw material using cow manure and clopyralid (Fujifilm Wako Pure Chemical Industries). After drying and pulverizing the cow manure at 105°C for 24 hours, clopyralid was added to the cow manure so that the clopyralid content was 19.375 mg per kg of dry cow manure. This content is equivalent to 100 times the estimated clopyralid content in dairy cow manure in Japan. The clopyralid-containing cow manure was prepared by adding a previously prepared methanol solution containing clopyralid (0.1 mg / L) dropwise to the dried cow manure and mixing it to the above content. To investigate the effect of heat treatment temperature on the decomposition of clopyralid, the raw material was heat-treated under oxygen-deficient conditions at three temperatures (100, 150, and 300°C) using the results of Example 1 as a reference. Specifically, the obtained clopyralid-containing cow dung was placed in a crucible with a lid and heat-treated using an electric furnace (FO810, Yamato Scientific, Tokyo, Japan). The temperature was increased at a rate of 10°C / min to the predetermined heating temperature, and then heated for 3 hours after reaching the predetermined temperature. After heating, the crucible was allowed to cool to room temperature in the electric furnace, and the heat-treated sample was collected. Hereinafter, the samples obtained at each temperature are designated T100, T150, and T300. For comparison, non-heat-treated clopyralid-containing cow dung and dried dairy cow dung without clopyralid were also prepared and designated T0 and CK, respectively.

[0027] Residual clopyralid levels in T0, T100, T150, and T300 were assessed according to the "Simple Method for Determining Residual Herbicide (Clopyralid) in Feed and Compost and Damage Mitigation Measures Manual (3rd Edition)" (https: / / www.naro.go.jp / publicity_report / publication / laboratory / niaes / manual / 155027.html). Specifically, 100 mL of heat-treated sample was uniformly mixed with 500 mL of potting soil (Zeoblend potting soil, Takii), and filled into a Noubawell pot (Fujiwara Seisakusho) without drainage holes. Two pea seeds (Azumino 30-day Kinusou PMR, Sakata Seed) were sown in two locations per pot, covered with approximately 1 cm of soil, and slowly irrigated with approximately 100 mL of water. The plants were grown in a greenhouse at a room temperature of 24°C. During the cultivation period, the pots were rearranged every seven days using a randomized block design and watered appropriately. The plants were grown until the fifth leaf fully expanded in all test plots.

[0028] The results are shown in Figure 2. No growth damage due to clopyralid was observed in T300, whereas significant growth damage was observed in all pots in T0 and T100. Growth damage was also observed in T150, with the exception of a few pots. This indicates that it is possible to obtain a carbonized product without the risk of clopyralid by heat-treating livestock manure containing clopyralid at temperatures above 300°C.

[0029] Furthermore, the present invention includes the following aspects. <Biochar>

[0101] Biochar containing pyrolysate of clopyralid.

[0102] Biochar according to

[0101] , wherein the thermal decomposition product of clopyralid is a solid substance obtained by heat treatment at a temperature of 140°C or higher.

[0103] Biochar according to

[0101] or

[0102] , wherein the excrement is feces and urine. <Biochar manufacturing method>

[0104] A method for producing biochar, comprising heat treating livestock manure containing clopyralid or a biomass raw material containing said manure at a temperature of 140°C or higher under oxygen-free or oxygen-poor conditions.

[0105] A manufacturing method according to

[0104] , wherein the temperature of the heat treatment is 140°C or higher and 220°C or lower. [105-2] A manufacturing method according to

[0104] or

[0105] , wherein the biomass raw material is compost. <How clopyralid is broken down>

[0106] A method for decomposing clopyralid, comprising heat treating livestock excrement containing clopyralid or a biomass raw material containing the same at a temperature of 140°C or higher under anoxic or oxygen-poor conditions.

[0107] The decomposition method according to

[0106] , wherein the temperature of the heat treatment is 140°C or higher and 220°C or lower. [107-2] A decomposition method according to

[0106] or

[0107] , wherein the biomass raw material is compost.

Claims

1. Biochar containing pyrolysate of clopyralid.

2. The biochar according to claim 1, wherein the thermal decomposition product of clopyralid is a solid substance obtained by heat treatment at a temperature of 140°C or higher.

3. The biochar of claim 1 , wherein the waste material is manure.

4. A method for producing biochar, comprising heat treating livestock manure containing clopyralid or a biomass raw material containing the same at a temperature of 140°C or higher under anoxic or oxygen-poor conditions.

5. The method according to claim 4, wherein the temperature of the heat treatment is 140°C or higher and 220°C or lower.

6. A method for decomposing clopyralid, comprising heat treating livestock excrement containing clopyralid or a biomass raw material containing the same at a temperature of 140°C or higher under anoxic or oxygen-poor conditions.

7. The decomposition method according to claim 6, wherein the temperature of the heat treatment is 140°C or higher and 220°C or lower.

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