Livestock and poultry manure-based biochar prepared by one-step hydrothermal method and resource utilization method thereof

Abstract

The application provides a livestock and poultry manure-based biochar prepared by one-step hydrothermal method and a resource utilization method thereof, and belongs to the technical field of livestock and poultry manure resource treatment. The livestock and poultry manure-based biochar prepared by the one-step hydrothermal method is obtained by simultaneously performing low-temperature pyrolysis of livestock and poultry manure and acid activation, utilizes the porous effect generated by the pyrolysis of the biomass components of livestock and poultry manure, and combines an acid modifier to prepare porous activated carbon which is rich in pore structure, acid sites and surface oxygen-containing functional groups. The livestock and poultry manure-based biochar is used as an NH3 adsorbent to adsorb NH3 in a livestock and poultry farm, so that odor pollution in the livestock and poultry farm is purified. The livestock and poultry manure-based biochar after saturation can be used as a soil modifier. Under the degradation of microorganisms, part of the NH3 adsorbed on the biochar is converted by migration to form nitrate, and the remaining unconverted NH3 reacts with the nitrate to generate nitrogen fertilizer ammonium nitrate, so that the growth of crops can be promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of resource processing of livestock and poultry manure, and in particular to livestock and poultry manure-based biochar prepared by a one-step hydrothermal method and a resource utilization method thereof. Background Art

[0002] With the rapid and steady growth of the livestock and poultry farming industry, intensive and large-scale livestock and poultry farming practices have gradually expanded, leading to a significant increase in the amount of livestock and poultry manure discharged during the farming process. According to statistics, the total amount of livestock and poultry manure generated in my country exceeds 3.8 billion tons annually, yet the resource utilization rate is only 70%. If it is not utilized rationally, effectively, and safely, it will not only result in a massive waste of resources but also cause a series of environmental pollution problems. How to reduce the environmental pollution caused by livestock and poultry manure while turning harm into benefit, turning waste into treasure, and achieving a virtuous cycle of matter and energy in the ecosystem has become a key focus of the livestock and poultry industry today.

[0003] The comparison of current livestock and poultry manure treatment technologies is shown in Table 1:

[0004] Table 1 Comparison of current livestock and poultry manure treatment technologies

[0005]

[0006] With the continued large-scale production of livestock and poultry manure, foul-smelling gas pollution has become the most direct manifestation of environmental pollution from livestock and poultry farms. The odor from livestock and poultry farms contains a variety of complex components, with ammonia (NH3) being the most prominent. Ammonia corrodes tissues on surfaces that come into contact with air and, upon entering the body, is converted into blood ammonia. Metabolizing 17g of blood ammonia consumes 65.3g of body weight, directly leading to decreased livestock welfare and affecting normal physiological activities. NH3 is not only a toxic substance that poses significant health risks to humans and livestock, but is also a significant atmospheric pollutant. Therefore, the management of NH3 in the livestock industry is particularly important.

[0007] Currently, deodorants are often used to control odorous gases from farms. However, chemical deodorants require large amounts of chemical deodorants, and the treated materials cannot be recycled, making them both uneconomical and environmentally unsuitable. While biological deodorants offer advantages such as high efficiency and minimal secondary pollution, their high operating costs and long cultivation cycles limit their widespread application.

[0008] The activated carbon adsorption method then emerged. This method has been widely studied and used because of its advantages such as simple removal process, high purification efficiency, and renewability. Furthermore, activated carbon has a well-developed pore structure and various active groups, making it suitable for use as an adsorbent alone or as a carrier through modification to purify various pollutants such as NH3. However, commonly used methods for preparing activated carbon and its composite materials often require expensive raw materials (coal and wood), and the processing technology is relatively complex. Problems such as high cost, low yield, and high energy consumption have greatly hindered the commercial application of current activated carbon materials. Therefore, the development of a new, efficient, low-energy, and environmentally friendly activated carbon composite material preparation technology is an important issue that needs to be urgently addressed for the large-scale application of activated carbon adsorption of NH3. Summary of the Invention

[0009] In light of this, the present invention aims to provide a one-step hydrothermal method for preparing livestock manure-based biochar and its resource utilization. This method uses livestock manure as a raw material, features a simple process, and is low-cost. While utilizing livestock manure as a resource, it also produces a biochar material with excellent NH3 adsorption properties.

[0010] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0011] The present invention provides a one-step hydrothermal method for preparing livestock and poultry manure-based biochar, comprising the following steps:

[0012] mixing nitric acid and livestock and poultry manure to obtain a mixed slurry;

[0013] The mixed slurry is subjected to a hydrothermal reaction in an oxygen-free environment to obtain livestock and poultry manure-based biochar;

[0014] The temperature of the hydrothermal reaction is 190-200°C.

[0015] Preferably, the mass concentration of the nitric acid is 65-69%;

[0016] The volume ratio of the livestock and poultry manure to nitric acid is 15-20 g:4-5 mL.

[0017] Preferably, the hydrothermal reaction time is 5 to 6 hours.

[0018] Preferably, the livestock and poultry manure is one or more of cow manure, chicken manure, pig manure and sheep manure.

[0019] The present invention provides livestock and poultry manure-based biochar prepared by the above method.

[0020] Preferably, the specific surface area of ​​the livestock and poultry manure-based biochar is 329.41 to 386.55 m 2 / g, pore volume of 0.15~0.18cm 3 / g, pore size is 0.06~0.08mm.

[0021] The present invention provides the use of the livestock and poultry manure-based biochar as an NH3 adsorbent.

[0022] The present invention provides a method for resource utilization of livestock and poultry manure-based biochar, comprising the following steps:

[0023] The above livestock and poultry manure-based biochar is placed in the farm to adsorb NH3;

[0024] Livestock and poultry manure-based biochar adsorbed with NH3 is used as a soil modifier.

[0025] Preferably, the time for adsorbing NH3 is 2 to 8 days.

[0026] Preferably, when the livestock and poultry manure-based biochar adsorbed with NH3 is used as a soil modifier, the mass ratio of the livestock and poultry manure-based biochar adsorbed with NH3 to soil is 1:15 to 20.

[0027] The present invention provides a one-step hydrothermal method for preparing livestock and poultry manure-based biochar, comprising the following steps: mixing nitric acid and livestock and poultry manure to obtain a mixed slurry; subjecting the mixed slurry to a hydrothermal reaction in an oxygen-free environment to obtain livestock and poultry manure-based biochar; and the temperature of the hydrothermal reaction is 190-200°C. The present invention uses livestock and poultry manure as raw material, which is low-cost and can reduce the degree of environmental pollution caused by livestock and poultry manure while turning harm into benefit and turning waste into treasure. The present invention adopts a "one-step hydrothermal method" of "low-temperature pyrolysis of livestock and poultry manure + acid activation" to produce livestock and poultry manure-based biochar. The method utilizes the porous effect generated by the synergistic pyrolysis of the biomass component of livestock and poultry manure, combined with an acid modifier, to produce porous activated carbon with a rich pore structure, acidic sites, and surface oxygen-containing functional groups. This method eliminates the drying pretreatment step in the traditional carbon production process, reduces the carbonization temperature from 700°C to 190-200°C, and does not require high-temperature operation. Biochar can be produced using only conventional equipment. Table 2 compares the present application with traditional activated carbon production technology:

[0028] Table 2 Comparison of one-step hydrothermal method for preparing livestock and poultry manure-based biochar and traditional activated carbon preparation technology

[0029]

[0030] Compared with biochar produced from different biomasses and commercial activated carbon, the livestock and poultry manure-based biochar prepared by the present invention has a richer pore structure, acidic sites and oxygen-containing functional groups, which is more conducive to sufficient reaction with gas and can achieve super adsorption of trace gas-phase molecules NH3.

[0031] The present invention provides a method for resource utilization of livestock and poultry manure-based biochar, comprising the following steps: placing the livestock and poultry manure-based biochar in a farm to adsorb NH3; and using the livestock and poultry manure-based biochar adsorbed with NH3 as a soil modifier. The present invention first uses the livestock and poultry manure-based biochar as an NH3 adsorbent to adsorb NH3 in the farm, thereby purifying the odor pollution in the farm. The saturated livestock and poultry manure-based biochar can be used as a soil modifier. On the one hand, the livestock and poultry manure-based biochar can improve the physical and chemical properties of the soil. On the other hand, microorganisms in the soil adhere to the surface of the biochar. Under the degradation action of the microorganisms, a portion of the NH3 adsorbed on the biochar is migrated and converted to form nitrate ions, which react with the remaining unconverted NH3 to form ammonium nitrate, a nitrogen fertilizer, which can promote crop growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The preparation process of livestock and poultry manure-based biochar;

[0033] Figure 2 This is a flow chart for resource utilization of livestock and poultry manure-based biochar;

[0034] Figure 3 This is the SEM image of livestock and poultry manure-based biochar;

[0035] Figure 4 It is a biochar activity testing device;

[0036] Figure 5 A comparison chart of the adsorption performance of biochars from different biomasses and commercial activated carbon;

[0037] Figure 6 The effects of waste biochar on soil properties and forage growth were investigated. DETAILED DESCRIPTION

[0038] The present invention provides a one-step hydrothermal method for preparing livestock and poultry manure-based biochar, comprising the following steps:

[0039] mixing nitric acid and livestock and poultry manure to obtain a mixed slurry;

[0040] The mixed slurry is subjected to a hydrothermal reaction in an oxygen-free environment to obtain livestock and poultry manure-based biochar;

[0041] The temperature of the hydrothermal reaction is 190-200°C.

[0042] The present invention mixes nitric acid and livestock and poultry manure to produce a mixed slurry. The present invention does not require drying or pre-treating the livestock and poultry manure; the manure can be directly mixed with nitric acid. In the present invention, the livestock and poultry manure is preferably one or more of cattle manure, chicken manure, pig manure, and sheep manure.

[0043] In the present invention, the concentration of the nitric acid is preferably 1 mol / L; the volume ratio of the mass of the livestock and poultry manure to the nitric acid is preferably 15 g:100 mL.

[0044] In the present invention, the mixing method is preferably stirring mixing. The present invention has no special requirements for the stirring method, and a stirring method well known to those skilled in the art can be used.

[0045] The present invention preferably performs the hydrothermal reaction in a hydrothermal reactor. In the present invention, the hydrothermal reaction is performed in an oxygen-free environment, and the present invention preferably uses a vacuum pump to provide the oxygen-free environment.

[0046] In the present invention, the temperature of the hydrothermal reaction is 190-200° C., preferably 195° C.; the time of the hydrothermal reaction is preferably 5-6 h, more preferably 5.5 h.

[0047] After the hydrothermal reaction, the present invention preferably performs post-treatment on the obtained hydrothermal reaction solution, and the post-treatment preferably includes the following steps:

[0048] The hydrothermal reaction liquid is subjected to solid-liquid separation, and the obtained solid is washed and dried to obtain livestock and poultry manure-based biochar solid.

[0049] The present invention has no particular requirements for the solid-liquid separation method; any solid-liquid separation method known to those skilled in the art may be used, such as filtration. In the present invention, the washing is preferably performed with deionized water until the pH of the eluate reaches 7 to 8. In the present invention, the drying is preferably performed by oven drying, preferably at 80°C for 8 hours.

[0050] This invention utilizes a one-step hydrothermal method to produce livestock manure-based biochar, combining low-temperature pyrolysis of livestock manure with acid activation. This method leverages the synergistic porous effect of pyrolysis between the biomass components of livestock manure, combined with an acid modifier, to produce porous biochar with a rich pore structure, acidic sites, and surface oxygen-containing functional groups. This method effectively addresses the challenges of existing activated carbon preparation processes, including complex processes, expensive carbon sources, and the need for frequent regeneration. It achieves the complete utilization of livestock manure, while being environmentally friendly and pollution-free.

[0051] The present invention provides livestock and poultry manure-based biochar prepared by the above method. In the present invention, the particle size of the livestock and poultry manure-based biochar is preferably 0.245 to 0.3 mm. In the present invention, the specific surface area of ​​the livestock and poultry manure-based biochar is preferably 386.55 m 2 / g, and the pore volume is preferably 0.18 cm 3 / g, and the pore size is preferably 0.08.

[0052] The present invention provides the use of the above-mentioned livestock manure-based biochar as an NH3 adsorbent. Compared to biochar produced from different biomasses and commercial activated carbon, the livestock manure-based biochar provided by the present invention possesses a richer pore structure, acidic sites, and oxygen-containing functional groups, which facilitates more efficient reaction with gases and offers superior performance in purifying NH3 from livestock farms.

[0053] In the present invention, the preparation process of the livestock and poultry manure-based biochar is as follows: Figure 1 shown.

[0054] The present invention provides a method for resource utilization of livestock and poultry manure-based biochar, comprising the following steps:

[0055] The above livestock and poultry manure-based biochar is placed in the farm to adsorb NH3;

[0056] Livestock and poultry manure-based biochar adsorbed with NH3 is used as a soil modifier.

[0057] In the present invention, the above-mentioned livestock and poultry manure-based biochar is placed in a farm to adsorb NH3. In the present invention, the farm is preferably a livestock and poultry farm, and the livestock and poultry manure-based biochar is preferably placed on the ceiling of the livestock and poultry breeding house. The livestock and poultry manure-based biochar is preferably used in a farm at a rate of 20 to 50 g / m2, more preferably 30 to 40 g / m2.

[0058] In the present invention, the time for adsorbing NH3 is preferably 2 to 8 days, preferably 2.63 days.

[0059] The present invention uses NH3-adsorbed livestock and poultry manure-based biochar as a soil modifier. The present invention has no particular requirements for the type of soil. When the NH3-adsorbed livestock and poultry manure-based biochar is used as a soil modifier, the mass ratio of the NH3-adsorbed livestock and poultry manure-based biochar to soil is preferably 1:15-20, more preferably 1:16-18.

[0060] In the present application, after the adsorption of NH3 from the livestock farm to the adsorption of the saturated soil conditioner, the degradation and removal of NH3 by the biochar can be divided into three stages, A, B and C, which are mainly adsorption, adsorption / degradation and biodegradation, respectively. In stage A, the physical adsorption of biochar removes NH3; in stage B, adsorption and chemical degradation occur simultaneously. Due to the saturation of the adsorption site of biochar, the adsorption capacity gradually decreases, and the chemical degradation gradually increases. According to the calculation of nitrogen balance, the data results show that the degradation of the acidic sites and oxygen-containing functional groups on the surface of biochar is significantly improved in this stage, and biochar also has a certain adsorption capacity; stage C is the biodegradation stage, and the adsorption-saturated biochar in the soil has microorganisms attached to the surface of biochar, which degrades the pollutants adsorbed by biochar. Similarly, in the nitrogen balance calculation, 70% of the ammonia nitrogen is biodegraded, and the remaining ammonia is combined with the biodegradation products to form NH4NO3 and other products. The main reactions are as follows:

[0061]

[0062]

[0063] After completing the adsorption and adsorption / degradation stages, the biodegradation stage is entered, and the NH3 in the soil system is finally degraded into NO3 - , and the microorganisms in the soil can only degrade about 70% of the ammonia nitrogen on the biochar, and the remaining ammonia nitrogen is combined with the biodegradation product NO3 - to form mainly NH4NO3 products, which are harmless to the soil and can be used as nitrogen fertilizer for plant growth.

[0064] In the present application, the resource utilization process diagram of the livestock and poultry manure-based biochar is shown in Figure 2 .

[0065] The one-step hydrothermal method for preparing the livestock and poultry manure-based biochar and the resource utilization method thereof provided by the present application will be described in detail below, but they should not be understood as limiting the scope of protection of the present application.

[0066] Example 1

[0067] The preparation method of the livestock and poultry manure-based biochar is as follows:

[0068] 15g of livestock and poultry manure was added to a hydrothermal reactor containing 4mL of a 65% HNO3 solution. The reactor temperature was raised to 190°C, with an operating autogenous pressure of approximately 1.5MPa during the reaction, and maintained at this temperature for 6 hours. After the reaction, the reaction system was allowed to cool naturally to room temperature. The solid product was removed, filtered, washed with deionized water, dried at 80°C for 8 hours, and pulverized through an 80-mesh sieve (pore size 0.18mm) to obtain acid-modified livestock and poultry manure hydrothermally activated carbon, i.e., livestock and poultry manure-based biochar.

[0069] Structural characterization

[0070] (1) The SEM image of the obtained livestock and poultry manure-based biochar is as follows Figure 3 As shown in the figure, the livestock manure-based biochar has uniform pores, which is conducive to adsorption. Further magnification reveals the formation of numerous smooth carbon microspheres on the biochar surface. These microspheres are typically made from carbohydrates, primarily monosaccharides, disaccharides, polysaccharides, and their derivatives. Their surfaces contain numerous oxygen-containing functional groups, such as carboxyl and hydroxyl groups. These microspheres can bind to a variety of molecules, ions, and other functional groups, promoting adsorption.

[0071] (2) N2 adsorption-desorption experiment

[0072] The obtained livestock and poultry manure-based biochar was subjected to N2 adsorption-desorption experiments, and its specific surface area was calculated to be 386.55 m 2 / g, pore volume 0.18cm 3 / g, and a pore diameter of 0.08. The high specific surface area of ​​biochar facilitates contact with the reactant gases; the large pore volume and small pore diameter increase contact time with the reactant gases. In summary, the biochar prepared in this invention possesses a rich pore structure and oxygen-containing functional groups, which facilitates sufficient reaction with the reactant gases.

[0073] Performance Testing

[0074] use Figure 4 The device shown evaluates the activity of different biochars. Figure 3 The device mainly consists of a dynamic gas preparation system, an adsorption-oxidation reaction system and a detection system. The three gases N2 (99.99%), NH3 (1%) and O2 (99.6%) are precisely controlled by a mass flow meter and then enter the gas mixing tank for uniform mixing to simulate the odor of a farm (O2 concentration: 1000ppm, NH3 concentration: 500ppm). During the reaction, the inlet and outlet concentrations of NH3 are detected by gas chromatography, and the oxygen content in the mixed gas is calibrated by a flue gas analyzer. The reaction temperature is 25°C, the amount of adsorbent used is 3g, and the total flow rate of the mixed gas entering the quartz tube reactor is 100mL min -1 , corresponding to a mass space velocity (WHSV) of 20000 mL·h -1 gsorbent-1 .

[0075] At room temperature 25℃ and atmospheric pressure 0.1013MPa, the performance of biochar prepared from different biomass materials was compared. The adsorption performance comparison between different biomass biochars and commercial activated carbon is shown in the figure below. Figure 5 shown. Figure 5 As shown in a, at room temperature and pressure, compared with activated carbon made from other biomass materials, the livestock and poultry manure-based biochar produced by the "one-step hydrothermal method" of the present invention has the highest NH3 removal rate at room temperature, which can reach 87%, which is comparable to the activity of commercially available coal-based activated carbon. Figure 5 Figure b shows that when the NH3 removal rate is maintained at 100%, the livestock and poultry manure-based biochar can last for about 4.5 hours, slightly better than commercial activated carbon; while other biomass activated carbons last less than 3 hours. The theoretical numerical conversion of gas chromatography data was used to obtain the NH3 adsorption capacity of different biomass activated carbons, such as Figure 5 As shown in Figure c, it can be seen that the adsorption capacity of NH3 from livestock and poultry manure-based biochar prepared by the "one-step hydrothermal method" is as high as 23.51 mg / g, which is nearly twice the adsorption capacity of biochar prepared from tobacco stems (13.22 mg / g) and rice husks (13.12 mg / g).

[0076] These results demonstrate that the livestock and poultry manure-based biochar produced using the present invention's "one-step hydrothermal method" can significantly reduce costs, addressing issues such as high energy consumption and complex process flows. Furthermore, compared to other biomass materials, biochar produced from livestock and poultry manure has advantages in purifying NH3 from farms, and its adsorption performance is slightly superior to that of commercial activated carbon.

[0077] Test Example 2

[0078] The greenhouse downstairs of the School of Environmental Science and Engineering at Kunming University of Science and Technology was selected to conduct an experiment on the effect of the application of waste biochar after saturated adsorption of NH3 on the physical and chemical properties of pasture soil and crop yield. Soil properties: pH value is 5.9, organic matter content is 33.6g / kg, bulk density is 1.3g / cm 3 , cation exchange capacity CEC 23.4mol / kg, water holding capacity 26.8%. Experimental content: The experimental area is 10m 2 The amount of manure-based biochar applied per square meter was 40-60g. Two groups were randomly arranged and planted with sweet elephant grass. Four treatments were set up in each group. FTN1 was fresh livestock and poultry manure-based biochar and no fertilizer was applied; FTN2 was fresh livestock and poultry manure-based biochar and fertilizer (nitrogen, phosphorus, and potassium compound fertilizer 600kg / hm2). 2 ); TN1 is waste biochar and no fertilizer; TN2 is waste biochar and fertilizer (nitrogen, phosphorus and potassium compound fertilizer 600kg / hm 2Field management was carried out according to normal agronomic management methods. Soil samples were collected once before and after planting, from the 0-20 cm soil layer on the surface. An appropriate amount of soil sample was taken diagonally using the quartering method. The soil sample was air-dried indoors and passed through a 0.425 mm sieve for determination of relevant physical and chemical properties. The results were as follows: Figure 6 shown.

[0079] The results showed that the application of waste biochar increased soil organic matter, water holding capacity, and ion exchange capacity to varying degrees. It also effectively inhibited soil acidification caused by fertilizer use, increased soil porosity and the viscosity of existing soil particles, enhanced soil aggregation, improved soil structure, and increased fertilizer utilization, promoting forage growth. In summary, NH3-saturated livestock and poultry manure-based biochar is harmless and beneficial to soil as a soil amendment.

[0080] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for resource utilization of livestock and poultry manure-based biochar, comprising the following steps: Place livestock and poultry manure-based biochar in farms to adsorb NH3; Using livestock and poultry manure-based biochar with adsorbed NH3 as a soil modifier; The method for preparing livestock and poultry manure-based biochar comprises the following steps: mixing nitric acid and livestock and poultry manure to obtain a mixed slurry; The mixed slurry is subjected to a hydrothermal reaction in an oxygen-free environment to obtain livestock and poultry manure-based biochar; The temperature of the hydrothermal reaction is 190-200° C., and the time of the hydrothermal reaction is 5-6 hours; The mass concentration of the nitric acid is 65-69%; The mass ratio of the livestock and poultry manure to the volume of nitric acid is 15-20 g: 4-5 mL; The specific surface area of ​​the livestock and poultry manure-based biochar is 329.41 to 386.55 m 2 / g, pore volume of 0.15~0.18cm 3 / g; The adsorption time of NH3 is 2 to 8 days; When the livestock and poultry manure-based biochar adsorbed with NH3 is used as a soil modifier, the mass ratio of the livestock and poultry manure-based biochar adsorbed with NH3 to soil is 1:15-20.

2. The method according to claim 1, characterized in that The livestock and poultry manure is one or more of cow manure, chicken manure, pig manure and sheep manure.

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