Carbon-based iron-loaded fertilizer as well as preparation method and application thereof
By combining unmodified biomass carbon with iron compounds, carbon-based iron-carrying fertilizer was prepared, which solved the problem of uncertain impact of existing biomass carbon on rice fields, and achieved significant inhibition of methane and nitrous oxide emissions Effect.
Patent Information
- Application Number
- CN202411317237.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-20
- Publication Date
- 2025-02-14
AI Technical Summary
The impact of existing biomass charcoal on greenhouse gas emissions in rice fields is uncertain, and it is difficult to effectively reduce the emissions of methane and nitrous oxide in soil.
By combining unmodified biomass carbon with iron compounds, carbon-based iron-carrying fertilizer is prepared, and the microbial structure and function in the soil are regulated through chemical adsorption and redox reactions, and the emission of methane and nitrous oxide is reduced.
It significantly inhibits the potential for methane production in rice fields, reduces the emission flux of nitrous oxide in the soil, and improves the efficiency of emission reduction for greenhouse gases.
Smart Images
Figure CN119431082A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of soil conditioners, and in particular relates to a carbon-based iron-loaded fertilizer with the function of reducing the emission of greenhouse gases nitrous oxide and methane and an application thereof. Background Art
[0002] Methane (CH4) and nitrous oxide (N2O) are two key greenhouse gases that affect global climate change. On a 100-year time scale, their warming potentials are 28 and 273 times that of carbon dioxide (CO2), respectively. As one of the most abundant active trace gases in the troposphere, CH4 can absorb and reradiate long-wave radiation emitted by the Earth's surface, thus significantly affecting the Earth's radiation balance, causing atmospheric temperatures to rise and changing the net radiation flux at the top of the atmosphere. N2O not only plays an important role in global climate change, but can also directly participate in the chemical reactions of stratospheric ozone, further damaging the ozone layer.
[0003] In this context, exploring and innovating rice field emission reduction measures is of great significance to mitigate global warming. Soil CH4 and N2O emissions are directly or indirectly affected by various human and environmental conditions, such as soil physical and chemical properties, climate factors and agricultural management measures. The biochar generated by high-temperature thermal decomposition of organic waste such as crop straw under micro-aerobic or anaerobic conditions through carbonization technology has attracted widespread attention. Biochar converts the active carbon in raw materials such as straw into inert carbon, which is difficult to be released in the form of CO2. In addition, due to its own alkalinity and pH buffering capacity, the use of biochar can increase the pH of the soil and alleviate soil acidification. Applying biochar to the soil is a potential management measure that can fix carbon in the long term and is beneficial to agricultural production. The impact of biochar application on greenhouse gas emissions from rice fields is inconsistent.
[0004] CH4 emissions from paddy fields are the result of the combined effects of methanogenesis and methane oxidation. Biochar can promote CH4 production in paddy fields on the one hand, and promote CH4 oxidation in paddy soil on the other hand, which has a "double-edged sword" effect on CH4 emissions from paddy fields. N2O emissions from paddy fields are the result of the combined effects of nitrification and denitrification processes. Biochar can promote the nitrification process in paddy soil in an aerobic environment on the one hand, and promote the denitrification process (generating N2O) or complete denitrification process (generating N2O) in an anaerobic environment on the other hand. 2) , the impact on N2O emissions from paddy soil is uncertain. Therefore, if the reduction efficiency of biochar on CH4 and N2O in paddy soil is to be improved, it is necessary to comprehensively consider the production pathways of CH4 and N2O and modify biochar.
[0005] Iron (Fe) is the fourth most abundant element in the earth's crust. 2+ and Fe 3+The redox transition between the two plays an important role in the biogeochemical cycle of N. Due to the periodic dry-wet alternation of paddy soil, the iron in paddy soil is affected by various oxidation states and participates in the N cycle through redox reactions. The results of indoor cultivation experiments show that the combination of biochar and iron hydroxide (Fe(OH)3) can increase NO3 - -N removal and reduced N2O production; in addition, Fe can promote the conversion of N2O into N2 through the denitrification process and participate in the nitrogen cycle.
[0006] Carbon-based iron-loaded fertilizers are made by introducing specific metal elements such as iron into unmodified biochar. This may further optimize the ability to regulate key steps in soil CH4 and N2O emissions by changing the structure and function of microorganisms in the soil or directly participating in the chemical process of electron transfer, providing an innovative and potential strategy for reducing greenhouse gas emissions from paddy soils. In recent years, carbon-based iron-loaded fertilizers, as a composite material of iron and biochar, are often used in anaerobic digestion systems. They are usually pretreated with raw materials such as FeCl3. This process activates the biochar and improves the surface properties of the soil (Wu Mingshan, et al.). Currently, most research on carbon-based iron-loaded fertilizers focuses on water bodies. Biochar loaded with metals can better remove NO3. - -N, but there is still a lack of research information on the effects of carbon-based iron-loaded fertilizers on paddy soil, especially in terms of greenhouse gas emission reduction. In this context, the present invention intends to apply carbon-based iron-loaded fertilizers to reduce CH4 and N2O emissions in paddy soil, provide new ideas for mitigating climate change, and promote the green and sustainable development of my country's agriculture. Summary of the invention
[0007] The purpose of the present invention is to provide a carbon-based iron-loaded fertilizer with the function of reducing soil methane and nitrous oxide emissions in view of the uncertainty of the impact of existing biochar on greenhouse gas emissions from rice fields.
[0008] The purpose of the present invention can be achieved through the following technical solutions:
[0009] A method for preparing a carbon-based iron-loaded fertilizer with the function of reducing greenhouse gas methane and nitrous oxide emissions, comprising the following steps: taking unmodified biochar powder and soaking it in a hydrochloric acid solution, rinsing it with water until the solution is neutral, and drying it at 70°C-80°C; soaking the dried biochar in a solution containing FeCl3 for 2 to 3 hours, adjusting the pH to slightly alkaline (pH between 7.0-7.5) with NaOH, and the treated biochar needs to be washed and filtered with water to remove unreacted iron salts and other possible impurities; finally, drying the biochar again at 70°C-80°C, and passing it through a 2mm sieve to obtain a carbon-based iron-loaded fertilizer with uniform particle size.
[0010] As a preferred embodiment of the present invention, the unmodified biochar powder is wheat straw biochar.
[0011] As a preferred embodiment of the present invention, the concentration of the hydrochloric acid solution is (0.5-1.5) mol·L -1 , preferably 1 mol·L -1 .
[0012] As a preferred embodiment of the present invention, the mass volume ratio of the unmodified biochar powder to the hydrochloric acid solution is 100 g·L -1 , the soaking time is 1-2h.
[0013] As a preferred embodiment of the present invention, the concentration of the FeCl3 solution is 200 g·L -1 .
[0014] As a preferred embodiment of the present invention, the mass volume ratio of the unmodified biochar to the FeCl3 solution is (90-100) g·L -1 , preferably 100 g·L -1 The soaking time of biochar in FeCl3 solution is 2-3h.
[0015] The carbon-based iron-loaded fertilizer is prepared according to the preparation method of the invention.
[0016] The invention discloses an application of the carbon-based iron-loaded fertilizer in reducing soil methane and nitrous oxide emissions.
[0017] As a preferred embodiment of the present invention, the carbon-based iron-loaded fertilizer is used to reduce the emission of methane and nitrous oxide from paddy field soil.
[0018] Beneficial Effects
[0019] The invention provides a carbon-based iron-loaded fertilizer for slowing down the emission of methane and nitrous oxide from paddy fields.
[0020] The carbon-based iron-loaded fertilizer has the following advantages:
[0021] 1) The carbon-based iron-loaded fertilizer provided by the present invention is prepared from ordinary biochar after chemical adsorption, has the general functions of biochar, and the preparation method is simple and easy to implement, and reduces the additional costs and gas emissions caused by the calcination process in the production of traditional modified biochar. At present, the preparation process of the modified biochar can be completed in the laboratory through the steps of mixing, drying, etc.
[0022] 2) The carbon-based iron-loaded fertilizer provided by the present invention can significantly inhibit the methane production potential of paddy soil;
[0023] 3) The carbon-based iron-loaded fertilizer provided by the present invention significantly reduces the soil nitrification rate and reduces the soil N2O emission flux compared with ordinary biochar. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 Scanning electron microscope (SEM) images and energy spectrum (EDX) analysis of unmodified biochar and carbon-based iron-loaded fertilizer. The left and middle figures are SEM images of unmodified biochar and iron-modified biochar at different magnifications, and the right figure is the EDS elemental composition spectrum of unmodified biochar and iron-modified biochar.
[0025] Figure 2 Figure 3. The inhibitory effect of carbon-based iron-loaded fertilizer on the methane production potential of paddy soil.
[0026] Figure 3 Dynamic changes of N2O emissions from paddy soil after addition of different carbon-based fertilizers.
[0027] Figure 4 Changes in cumulative N2O emissions from paddy soil after adding different carbon-based fertilizers. DETAILED DESCRIPTION
[0028] Example 1 Preparation of carbon-based iron-loaded fertilizer and related structural characterization
[0029] 1. Preparation of carbon-based iron-loaded fertilizer
[0030] 100g unmodified biochar (passed through a 100-mesh sieve) was soaked in 1L of 1 mol·L -1 The biochar was then immersed in a 200 g·L hydrochloric acid solution and rinsed with ultrapure water several times after one hour until the solution was neutral, and then dried in an oven at 75 °C. -1 The approximate mass volume ratio of the dried biochar to the FeCl3 solution is 100 g·L -1 . Ferric chloride is a commonly used iron source that can effectively react with the surface of carbon materials to form an iron oxide or hydroxide coating. This coating can significantly improve the surface properties of biochar, such as increasing the specific surface area and providing more active sites, which is beneficial for subsequent applications such as adsorption or catalysis. The pH is adjusted to slightly alkaline (pH between 7.0-7.5) with NaOH, and the treated biochar needs to be washed and filtered with ultrapure water 3 to 5 times to remove unreacted iron salts and other possible impurities. Finally, the biochar is dried again at 75°C and passed through a 2mm sieve to obtain a carbon-based iron-loaded fertilizer with uniform particle size.
[0031] 2. Physical properties and microstructure characterization of unmodified biochar and carbon-based iron-loaded fertilizer
[0032] like Figure 1As shown in Table 1, the pH of unmodified biochar is significantly higher than that of iron-modified biochar. Further observation of the two by scanning electron microscopy (SEM) and energy spectrum analysis (EDS) revealed that the surface structure of unmodified biochar is relatively smooth, while the surface of carbon-based iron-loaded fertilizer is relatively rough, with many sharp protrusions and microcrystalline structures. Through energy spectrum analysis, the iron content in carbon-based iron-loaded fertilizer is significantly increased compared with that of unmodified biochar ( Figure 1 ). In general, the porous structure and unique specific surface area of biochar are key factors in its adsorption capacity. The results of specific surface area and pore structure analysis showed that the porous structure of unmodified biochar was not well developed, with a small specific surface area, micropore area and external surface area. Compared with unmodified biochar, carbon-based iron-loaded fertilizer has a higher specific surface area, which indicates that it may have better adsorption capacity. The pore size distribution of unmodified biochar and iron-modified biochar was also analyzed in this study. The pore size of unmodified biochar is mainly concentrated in 50-70nm (macroporous range), while the pore size of carbon-based iron-loaded fertilizer is mainly concentrated in 10-30nm (mesoporous range).
[0033]
[0034]
[0035] Example 2 Indoor anaerobic culture test
[0036] The indoor anaerobic culture experiment was conducted in the College of Resources and Environmental Sciences of Nanjing Agricultural University. The test soil was paddy soil, which was collected from the Rugao Agricultural Science Institute in Jiangsu Province (32°51′N, 120°49′E). Soil samples were collected from the tillage layer soil (0-20cm) before fertilization. Five soil samples were collected from this sampling point and mixed thoroughly. The soil samples were air-dried at 25°C and passed through a 2mm sieve to remove visible roots and organic residues.
[0037] The experiment set up three treatments, namely, no biochar treatment (Control), unmodified biochar treatment (Biochar) and carbon-based iron fertilizer treatment (Fe-modified biochar). The amount of biochar added in the two treatments was 2% of dry soil weight. Each treatment included 3 replicates. Add 5g of fresh paddy field soil and 10mL of sterilized and oxygen-free ultrapure water to a 30mL serum bottle so that there is a water layer of about 10mm on the soil surface. Seal the bottle with butyl rubber and crimping. In order to keep the bottle in an anaerobic environment, rinse it repeatedly with N2 for 3 to 5 minutes, and shake the bottle continuously, then place it in a dark incubator at 25°C for 5 days. Shake the serum bottle before collecting gas to fully mix the gas in the bottle, then let it stand until the gas and liquid are separated and the gas is collected. About 2 mL of gas in the bottle was collected with a syringe at 1 h, 60 h and 120 h of culture. In order to reduce the instability of the pressure in the bottle and the anaerobic environment when collecting gas, 3 batches of sampling bottles were set up for each treatment for sampling in 3 time periods.
[0038] The results are attached Figure 2 As shown in Figure 2, there were significant differences in the soil methane production potential (MPPs) among the three treatments (Control, Biochar, and Fe-modified biochar) (p<0.05). The MPPs in the Biochar treatment was the highest, reaching 3380.25 μg g -1 ·d -1 Compared with the Control treatment, the soil MPPs increased significantly by 59% (p<0.05) after adding unmodified biochar, and decreased significantly by 79% (p<0.05) after adding carbon-based iron-loaded fertilizer. The MPPs in the Biochar treatment were 7.48 times higher than those in the Fe-modified biochar treatment.
[0039] Example 3 Indoor aerobic culture test
[0040] The soil samples used in the aerobic culture experiment were consistent with those in Implementation 2. Weigh 60 g of air-dried soil sample (based on dry soil) into a 250 mL conical flask, adjust the soil moisture to 55% of the maximum water holding capacity (WHC) with ultrapure water, and place the bottle in an incubator at 25 °C in the dark for activation for 7 days. A total of three treatments were set up, namely (1) control (Control); (2) treatment with ordinary biochar (Biochar); (3) treatment with modified biochar (Fe-modified biochar). The amount of biochar added in the two treatments was 2 wt% of dry soil weight. Urea was added to each treatment as a nitrogen source, and it was evenly dripped into the soil in the form of an aqueous solution. The application amount was 200 mg N kg-1 Dry soil weight. Before the formal cultivation experiment began, ultrapure water was used to replenish soil moisture to 80% WHC. Each bottle was covered with a plastic wrap with 6 small holes to reduce water evaporation during the cultivation process and maintain aerobic conditions. Water was replenished every two days to reduce water loss in the triangular bottle. All conical bottles were designed with a completely randomized block and cultured in a dark environment at 25°C for 27 days. After the formal cultivation, gas was collected twice a day in the first 5 days, and then every 2-3 days from the 6th to the 27th day. Ventilate for 5 minutes before each gas collection, then seal the conical bottle with a rubber stopper, use a syringe to collect the gas in the bottle to calculate the initial concentration of N2O, and then collect gas again after sealing for two hours. The N2O emission calculated by the N2O concentration before and after two hours of sealing represents the average daily N2O emission on the sampling day. The total N2O emission during the cultivation period was calculated by sequentially accumulating the emission flux of every two adjacent sampling days.
[0041] The research results are as attached Figure 3 and 4 The N2O emission rates of the three treatments increased rapidly within 5 days after urea application, until a peak appeared, then decreased and stabilized. The three treatments all had emission peaks within the first five days, with the following values: Biochar (85.32 μg kg -1 ·h -1 )>Control(53.07μg·kg -1 ·h -1 )>Fe-modified biochar(38.03μg·kg -1 ·h -1 ). In the late stage of cultivation, soil N2O emissions were low and tended to be stable, and there was no significant difference in N2O emissions among the three treatments. The cumulative N2O emissions under the ordinary biochar treatment reached 3.55 mg N·kg in the first 4 days. -1 , accounting for 74.7% of the total emission during the 27-day cultivation period. Compared with the control treatment and iron-modified biochar, biochar addition significantly increased N2O emissions from paddy soil (P<0.01), while iron-modified biochar addition had a lower emission peak than the control treatment, and the cumulative N2O emission only slightly increased by 8.7%, while compared with ordinary biochar, it reduced N2O emissions by 44.7%.
Claims
1. A method for preparing a carbon-based iron-loaded fertilizer having the function of reducing greenhouse gas methane and nitrous oxide emissions, characterized in that: The method comprises the following steps: soaking unmodified biochar powder in a hydrochloric acid solution, rinsing with water until the solution is neutral, and drying at 70°C-80°C; soaking the dried biochar in a solution containing FeCl3 for 2 to 3 hours, adjusting the pH to 7.0-7.5 with NaOH, and washing and filtering the treated biochar with water to remove unreacted iron salts and other possible impurities; finally, drying the biochar again at 70°C-80°C, and passing through a 2mm sieve to obtain a carbon-based iron-loaded fertilizer with uniform particle size.
2. The preparation method according to claim 1, characterized in that: The unmodified biochar powder is wheat straw biochar.
3. The preparation method according to claim 1, characterized in that: The concentration of the hydrochloric acid solution is (0.5-1.5) mol·L -1 , preferably 1 mol·L -1 .
4. The preparation method according to claim 1, characterized in that: The optimal mass volume ratio of the unmodified biochar powder to the hydrochloric acid solution is 100 g·L -1 , the soaking time is 1-2h.
5. The preparation method according to claim 1, characterized in that: The concentration of FeCl3 solution is (100-300) g·L -1 , preferably 200g·L -1 .
6. The preparation method according to claim 1, characterized in that: The mass volume ratio of the unmodified biochar to the FeCl3 solution is (90-100) g·L -1 The soaking time of biochar in FeCl3 solution is 2-3h.
7. The preparation method according to claim 6, characterized in that: The mass volume ratio of the unmodified biochar to the FeCl3 solution is 100 g·L -1 .
8. A carbon-based iron-loaded fertilizer prepared by the preparation method according to any one of claims 1 to 7.
9. Use of the carbon-based iron-loaded fertilizer according to claim 8 in reducing soil methane and nitrous oxide emissions.
10. The use according to claim 9, characterized in that The carbon-based iron-loaded fertilizer is used to reduce the emission of methane and nitrous oxide from paddy field soil.