A method for improving organic fertilizer quality and reducing ammonia emissions by conditioning aerobic compost with hydrothermal carbonization liquid

Abstract

The present invention belongs to the field of agricultural and forestry resource utilization, and in particular to a method for conditioning aerobic composting with hydrothermal carbonization liquid to achieve organic fertilizer quality improvement and ammonia emission reduction. The hydrothermal carbonization liquid is prepared by hydrothermal reaction under certain temperature and pressure conditions using agricultural and forestry waste as raw materials, and its applicability is further improved by modification measures; the aerobic composting step is mainly as follows: using livestock and poultry manure, poplar wood chips and modified hydrothermal carbonization liquid as fermentation raw materials, piling them in an aerobic composting reactor for 20-35 days, turning the pile several times during this period and maintaining suitable moisture conditions to fully mature them. The hydrothermal carbonization liquid can be used as an effective compost additive to improve compost nutrients, humic acid and dissolved organic matter (DOM) content without affecting compost maturity, and significantly reduce NH3 volatilization emissions by 7.8-22.9%, achieving the multiple goals of waste resource recycling and environmental emission reduction.

Description

Technical Field

[0001] The present invention belongs to the field of agricultural and forestry resource utilization, and specifically relates to a method for improving the quality of organic fertilizer and reducing ammonia emissions by conditioning aerobic compost with hydrothermal carbonization liquid. Background Art

[0002] China currently generates approximately 3.8 billion tons of livestock and poultry waste annually, of which approximately 1.5 billion tons is livestock and poultry manure, accounting for nearly 39.5% of the total waste. Residual antibiotics, heavy metals, pathogens, and other pollutants in livestock and poultry manure pose a serious environmental pollution problem. As an organic solid waste, livestock and poultry manure is rich in organic matter (OM) and nutrients such as nitrogen, phosphorus, and potassium.

[0003] Aerobic composting of livestock and poultry manure refers to a process in which organic matter in manure, after being subjected to the action of natural microorganisms under aerobic conditions, undergoes a series of degradation and transformations, resulting in the mineralization, humification, and harmlessness of the organic matter, which is then transformed into a mature fertilizer suitable for agricultural production. Using livestock compost as fertilizer helps provide essential nutrients for plants. Composting is an effective and widely used method for converting animal manure and other agricultural waste into high-quality agricultural organic fertilizer. Adding a certain amount of additives to compost is effective in reducing nitrogen loss, and the nitrogen retention effects of different types of additives have been widely studied both domestically and internationally.

[0004] Aerobic composting produces harmful gases, which can cause a certain degree of atmospheric pollution. Among them, NH3 emitted from composting has an unpleasant, irritating odor, which degrades air quality. NH3 is also a major cause of acid rain, causing serious damage to soil, water, and surface organisms. Therefore, careful monitoring of NH3 emissions is crucial during the composting process. Furthermore, many compost products are nutrient-deficient, requiring the addition of plant nutrients or fertilizers to meet crop needs.

[0005] my country's plantation forests are expanding rapidly, making it the country with the largest area of preserved planted forests in the world. Poplars are one of the primary planting species in fast-growing, high-yield plantation projects. While this rapid expansion of fast-growing poplars meets the demand for timber, it also generates significant amounts of logging and processing residues, which are rich in bioactive substances, cellulose, and hemicellulose. Sawdust, an active composting agent with a high organic matter content, can adjust the carbon-nitrogen ratio of compost. It also contains the free space and attachment sites necessary for microbial growth.

[0006] Hydrothermal carbonization (HTC) is a novel method for converting biowaste into hydrochar. Because HTC operates under mild conditions (180-250°C), it is expected to release only small amounts of gas (primarily CO2). The HTC process typically lasts from a few minutes to a few hours, producing a solid carbon fuel called hydrochar and a liquid product called hydrochar solution (AP). Previous studies have shown that most AP obtained from hydrocharring of lignocellulosic biomass exhibits acidic properties due to the formation of large amounts of volatile fatty acids. This acidic AP significantly inhibits soil ammonia volatilization by altering soil pH. Furthermore, similar to livestock manure, AP contains abundant nutrients such as nitrogen, phosphorus, and potassium, as well as organic matter. Hydrochar solution is known for its ability to increase soil fertility, improve soil structure, and reduce soil ammonia volatilization. While its application in soils has been studied, there are no reports of its addition as an additive to composting. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for improving the quality of organic fertilizer and reducing ammonia emissions by conditioning aerobic compost with hydrothermal carbonization liquid.

[0008] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is: a method for conditioning aerobic compost with hydrothermal carbonization liquid to improve the quality of organic fertilizer and reduce ammonia emissions, characterized in that the hydrothermal carbonization liquid is a liquid product of the hydrothermal carbonization reaction; the composting step is: using livestock and poultry manure, poplar wood chips and hydrothermal carbonization liquid as fermentation raw materials, and stacking them in an aerobic composting reactor for 20-35 days; a mixture of livestock and poultry manure and poplar wood chips is used as the initial pile material; and the ratio of hydrothermal carbonization liquid to initial pile material is (3-15) L:100 kg.

[0009] In a preferred embodiment, the preparation process of the hydrothermal carbonization liquid is as follows: the preparation process of the hydrothermal carbonization liquid is as follows: agricultural and forestry waste is used as raw material, placed in a hydrothermal carbonization reactor, the mass volume ratio of agricultural and forestry waste to water is adjusted to 1kg: (8-10) L, the reaction temperature is 220-240 ° C, the pressure is 7-9 MPa, and the reaction time is 1-2h; the liquid product after the reaction is collected and filtered, and the filtrate is the initial hydrothermal carbonization liquid (AP); Mg is added to the initial hydrothermal carbonization liquid 2+ and PO4 3- The solution pH is adjusted to 9.5-10.5 to obtain struvite precipitate (MgNH₄PO₄·6H₂O). The supernatant is then taken and the pH adjusted to 7 to obtain a modified hydrothermal carbonization solution (MAP). The modified hydrothermal carbonization solution has a neutral pH, and the ammonium nitrogen content of MAP is lower than that of AP. In this article, hydrothermal carbonization solution refers to either the initial hydrothermal carbonization solution or the modified hydrothermal carbonization solution.

[0010] The livestock and poultry excrement is dry livestock and poultry excrement, and the mass ratio of the livestock and poultry excrement to the poplar wood chips is 100:5-10.

[0011] The hydrothermal carbonization liquid is added to the initial pile of materials at once, or is added to the initial pile of materials in batches.

[0012] The method for preparing the initial pile is as follows: dry livestock and poultry manure is uniformly mixed with poplar wood chips to form the initial pile.

[0013] When the ratio of hydrothermal carbonization liquid to initial pile is not greater than 7L:100kg, the hydrothermal carbonization liquid is added to the initial pile at one time; when the ratio of hydrothermal carbonization liquid to initial pile is greater than 7L:100kg, the hydrothermal carbonization liquid is added to the initial pile in batches, which refers to 2-7 times. When the hydrothermal carbonization liquid is added for the first time, 40%-50% of the total amount of the hydrothermal carbonization liquid is added; except for the first time, the amount of hydrothermal carbonization liquid added each time is basically the same.

[0014] At the beginning of the aerobic composting step, the first addition of hydrothermal carbonization liquid is completed.

[0015] Preferably, the composting step is: using livestock and poultry manure, poplar wood chips and hydrothermal carbonization liquid as fermentation raw materials, and piling them in an aerobic composting reactor for 30 days.

[0016] In a preferred embodiment, the compost pile is fully turned over every 3-6 days, and an appropriate amount of water is added each time the compost is turned over to maintain the moisture content at 55%-60%.

[0017] The addition of hydrothermal carbonization liquid increased the maturity of the compost pile, the nutrient content of the pile and the humic acid content, and reduced the NH3 volatilization emission by 7.8-22.9%.

[0018] Compared with existing technologies, the present invention has significant advantages: the liquid phase product (AP) produced during the hydrothermal carbonization process can be used as a compost conditioner to accelerate the aerobic composting of livestock and poultry manure, enhance compost quality, and improve the composting process. Composting experiments were conducted using a mixture of chicken manure and poplar sawdust. Four treatments were set up, depending on the type of hydrothermal carbonization liquid and the low (L) or high (H) amount of added AP: AP-5%, AP-10%, MAP-5%, and MAP-10%. A normal composting treatment was also used as a control. The effects of the hydrothermal carbonization liquid on the composting process were determined by changes in compost temperature, pH, electrical conductivity (EC), seed germination index (GI), total nitrogen, total phosphorus, total potassium, humic acid, and dissolved organic matter (DOM). The results showed that the duration of the high-temperature phase, pH, electrical conductivity, and seed germination index of the compost after the addition of the hydrothermal carbonization liquid met national organic fertilizer standards. The high-dose addition treatment significantly increased dissolved organic matter (DOM) in the compost by 55.4%-69.7% (P < 0.05). Furthermore, compared with the control, the addition of hydrothermal carbonization liquid increased the total humic acid content in the compost by 2.7%-4.7%. The AP-10% treatment significantly increased humic acid by 5.0% and total nitrogen by 12.3% compared with the control (P < 0.05). The MAP-10% treatment increased total phosphorus by 7.7% and total potassium by 19.8%, respectively, compared with the control. Hydrothermal carbonization liquid can be used as an effective compost additive to increase nutrient, humic acid, and DOM content in compost without affecting compost maturity. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 :(a) Changes in temperature during composting;(b) Changes in pH during composting;(c) Changes in electrical conductivity during composting;(d) Changes in seed germination index during composting;

[0020] Figure 2 :(a) Changes of total nitrogen during composting;(b) Changes of total phosphorus during composting;(c) Changes of total potassium during composting;

[0021] Figure 3 :(a) Changes of total humic acid during composting;(b) Changes of humic acid during composting;(c) Changes of fulvic acid during composting;(d) Changes of HA / FA during composting;

[0022] Figure 4:(a) Maximum fluorescence intensity (Fmax) of three fluorescent components in compost identified by EEM-PARAFAC;(b) Fluorescence parameters of compost DOMZ, BIX: biological index; FI: fluorescence index; HIX: humification index;(c) Fluorescence spectrum of DOM in compost obtained based on PARAFAC analysis;(d) Changes in HA / FA during composting process;

[0023] Figure 5 :(a) Changes in total nutrients during composting; (b) Cumulative ammonia volatilization during composting. DETAILED DESCRIPTION

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0025] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods. The materials, reagents, instruments, etc. used in the following examples are all commercially available unless otherwise specified.

[0026] Example 1 Preparation of hydrothermal carbonization liquid

[0027] The composting experiment was carried out in the greenhouse of Jiangsu Academy of Agricultural Sciences. Chicken manure, poplar wood chips and hydrothermal carbonization liquid were used as fermentation raw materials. The preparation process of hydrothermal carbonization liquid is as follows: using oak leaves as raw materials, placing them in a hydrothermal carbonization reactor, adjusting the solid-liquid ratio to 1:10 (i.e. the mass volume ratio of oak leaves to water is 1kg:10L), the reaction temperature is 220℃, the pressure is 8MPa, and the reaction time is 1h. Collect the liquid product after the reaction and filter it. The filtrate is the initial hydrothermal carbonization liquid (AP). Add Mg to AP 2+ and PO4 3- (to make Mg in solution 2+ , PO 3- 4 and NH4 + The molar mass ratio is 1:1:1), NaOH is added to adjust the solution pH to 10 to obtain struvite precipitate (MgNH4PO4·6H2O). The supernatant is taken and HCL is added to adjust the pH to 7 to obtain NH4 + The basic physicochemical properties of the initial hydrothermal carbonization liquid (AP) and the modified hydrothermal carbonization liquid (MAP) are shown in Table 1.

[0028] Table 1. Basic physical and chemical properties of hydrothermal carbonization liquid

[0029]

[0030] Note: Concentration unit is mg·L -1 ; ND means not detected.

[0031] Example 2 Composting Experiment

[0032] The livestock and poultry manure is air-dried livestock and poultry manure. The mass ratio of livestock and poultry manure to poplar wood chips is 100:5, and the two are evenly mixed to form the initial pile. The dry weight of the initial pile is 9 kg, and the initial C / N ratio is about 20. According to the composting process parameters, the experiment set up five treatments with different additive ratios: control group (Control), AP-5% (adding 5% of the initial pile dry weight of AP), AP-10% (adding 10% of the initial pile dry weight of AP), MAP-5% (adding 5% of the initial pile dry weight of MAP), MAP-10% (adding 10% of the initial pile dry weight of MAP); among them, the carbon liquid applied in the AP-10% and MAP-10% treatments is 50% of the total amount added for the first time, and the remaining 50% is divided into 4 parts and applied each time the water is replenished, that is, the remaining 50% is applied on the 7th, 11th, 17th, and 25th days respectively. The volume of initial hydrothermal carbonization liquid or modified hydrothermal carbonization liquid added to each treatment is shown in Table 2:

[0033] Table 2. Compost additive content

[0034]

[0035] The moisture content of the composting materials for each treatment was adjusted to about 60%. The composting reactors consisted of five insulation boxes with an inner diameter of 52.5*40*29 (cm) and an outer diameter of 64*48*36 (cm). The composting time was 30 days.

[0036] Sample collection

[0037] The compost pile was turned over thoroughly on days 4, 7, 11, 17, 25, and 30. Water was added each time to maintain a moisture content of 55% to 60%. Compost samples were collected on days 1, 4, 7, 11, 17, 25, and 30, with three replicates collected from each reactor. A five-point sampling method was used: approximately 150 kg of samples were collected from the center and four corners. The samples were then mixed thoroughly and quartered, with approximately 250 g of sample taken back to the laboratory for testing. The remaining samples were returned to the compost pile. The samples were divided into two portions: one was air-dried and crushed for physical and chemical property testing, and the other was frozen and stored at -20°C. Compost samples from days 4, 11, and 30 were used as representative samples of the high-temperature, cooling, and mature stages of the compost.

[0038] Temperature measurement

[0039] After composting begins, insert temperature recorders into the top, middle, and bottom of the pile to measure temperatures. Survey five points on each layer. Read the temperatures at each survey point at 8:00 AM, 1:00 PM, and 6:00 PM daily, taking the average. Simultaneously measure the ambient temperature. Export this data to calculate the accumulated temperature and determine whether the system is capable of collecting ammonia volatilization data.

[0040] Effective accumulated temperature formula: T=Σ(T i -T0)×Δt

[0041] Ti is the compost temperature at time i, T0 is the starting temperature (biological zero) at which microorganisms in the compost begin to multiply, and Δt is the duration of Ti. When the temperature of the compost material drops below 20°C, the composting process will significantly slow down or even stop.

[0042] pH and EC value determination

[0043] The fresh compost sample was mixed with deionized water at a ratio of 1:10 (mass:volume), shaken for 30 min, allowed to stand for 10 min, centrifuged for 30 min, and heated at 3200 r / min. -1 After filtration, the filtrate was measured using a multi-parameter analyzer.

[0044] Determination of germination index (GI)

[0045] Weigh 10 g of fresh sample, add 100 mL of distilled water, shake for 1 hour, let stand at room temperature for one day and night, filter, and pipette 5 mL of the filtrate into a 9 cm Petri dish lined with filter paper. Sow 10 plump rapeseed seeds and incubate in a 28°C constant temperature incubator for 48 hours. Use distilled water as a control. The calculation formula is as follows:

[0046]

[0047] Determination of organic matter, total nitrogen and moisture content

[0048] The organic matter content was determined by the potassium dichromate volumetric method, the total nitrogen was determined by the concentrated sulfuric acid H2SO4-H2O2 digestion method, and the moisture content was determined by the drying method.

[0049] The calculation formula for moisture content is:

[0050]

[0051] Where M is the mass of fresh sample and Ms is the mass of sample after drying.

[0052] Determination of total humus, humic acid (HA) and fulvic acid (FA) content

[0053] Total humus

[0054] Take 2.50 g of air-dried compost sample passed through a 60-mesh sieve and transfer it to a 250 ml conical flask. Then add 50 ml of sodium hydroxide-disodium hydrogen phosphate extract (0.1 M NaOH + 0.1 M Na2P2O7 (V:V = 1:1)) and sieve it at 25 ° C at 180 r min. -1 The extraction was carried out by shaking for 16 h. After the shaking was completed, the extract was transferred to a centrifuge tube and centrifuged at 6000 r·min. -1The mixture was centrifuged for 10 minutes and the supernatant was collected. The residue was extracted three times according to the above steps. The supernatants obtained each time were combined. A portion of the combined supernatant was filtered and diluted to determine the TOC, which is the total humic acid content.

[0055] Determination of Humic Acid and Fulvic Acid

[0056] Take about 20.00 ml of the combined supernatant in the above steps and put it into a small beaker. Slowly add 6 mol·L -1 HCl solution, stirring the liquid with a glass rod until flocculent precipitation appears. Then place the small beaker in a 70℃ constant temperature water bath and keep it warm for 30 minutes to allow the humic acid to precipitate completely. Then let it stand overnight. The next day, filter or centrifuge the sample in the beaker and then use a 0.01mol·L -1 The precipitate is washed with HCl solution until the filtrate is colorless. The resulting clear solution is the fulvic acid solution, and the precipitate is humic acid. The fulvic acid solution is diluted and the content is measured using a TOC instrument. The humic acid content can be determined by subtracting the total humic acid content from the fulvic acid content. All measurements for each sample were performed in triplicate, and the results are expressed as the average of the triplicate measurements.

[0057] DOM extraction and characterization

[0058] A 5g compost sample was dissolved in 50ml of deionized water (1:10, w / v) and shaken for 24 hours. The extract was centrifuged at 6000rpm for 15 minutes and then filtered through a 0.45μm membrane. The filtrate was analyzed for different types of dissolved organic matter (DOM) using 3D-EEM with emission (EM) wavelengths between 200 and 900nm and excitation (EX) wavelengths between 200 and 900nm. Based on the EEM method, a numerical method was used to calculate the volume percentage of DOM. Five regions were defined: aromatic protein I (EX: 220-250 nm; Em: 280-330 nm); aromatic protein II (EX: 220-250 nm; Em: 330-380 nm); fulvic acid-like (EX: 220-250 nm; Em: 380-550 nm); soluble microbial byproduct-like (EX: 250-450 nm; Em: 280-380 nm); and humic acid-like (EX: 250-450 nm; Em: 380-550 nm). Three parameters were determined from the fluorescence spectrum: fluorescence index (FI), biomass index (BIX), and humification index (HIX).

[0059] Statistical analysis

[0060] Data were processed using Microsoft Excel (2019), and statistical analysis was performed using SPSS 16.0. Significant differences (P < 0.05) were calculated using one-way analysis of variance (ANOVA) with the Duncan's multiple range test. Images were created using Origin (2019b). 3D-EEM images were created using the R programming language.

[0061] Changes in maturity parameters during composting

[0062] Temperature changes of the pile during composting process Figure 1 As shown in (a), the temperature trends across all treatments were essentially the same, progressing through three main phases: a warming phase (day one), a high-temperature phase (days 2-6), a cooling phase (days 7-19), and a mature phase (days 20-30). Throughout the composting cycle, the control, AP-5%, AP-10%, MAP-5%, and MAP-10% treatments maintained temperatures above 50°C for 7, 5, 5, 7, and 7 days, respectively. All treatments experienced a rapid temperature increase on the first day of composting, followed by a high-temperature phase on the second day. The maximum temperature across all treatments reached 62.8-64.9°C, after which it gradually decreased, stabilizing around day 18 at a range of 21.3-29.8°C. After the first four turnings (days 1, 4, 8, and 12), the compost temperatures in all treatments increased rapidly. Furthermore, the effective accumulated temperature in all treatments exceeded 10,000°C, and the treatments with hydrothermal carbonization reduced the effective accumulated temperature by 5.0%-17.2% compared to the control.

[0063] After the composting is completed, the pH of the pile is Figure 1 As shown in (b), compared with the control, the pH of the two treatments with added hydrothermal carbonization liquid (AP) was slightly lower than the control, and the pH of the two treatments with added modified hydrothermal carbonization liquid (MAP) was slightly higher than the control, but there was no statistical difference in the results.

[0064] The EC changes of the pile during composting are as follows: Figure 1 As shown in (c), the EC variation of the control, MAP-5%, and MAP-10% treatments was relatively small, ranging from 900 to 1200 ms·cm -1 The EC values of the control, AP-5%, AP-10%, MAP-5%, and MAP-10% treatments varied widely and were significantly higher than those of the other treatments. The initial EC values of the control, AP-5%, AP-10%, MAP-5%, and MAP-10% treatments were 2.79-3.49 ms·cm -1 , and at the end were 2.00-2.47ms·cm -1 At the end of each composting treatment, the electrical conductivity decreased by 17.5%-28.3% compared with the initial conductivity, among which the EC of AP-10% and MAP-10% treatments was significantly reduced by 16.3% compared with the control (P<0.05).

[0065] according to Figure 1 As shown in (d), the seed germination index of each treatment showed a significant upward trend with increasing composting time. Compared to the control, the addition of hydrothermal carbonization solution reduced the seed germination index somewhat, but ultimately remained above 50%. In contrast, the AP-5% and MAP-5% treatments achieved higher seed germination indices than the AP-10% and MAP-10% treatments.

[0066] Changes in nutrient content of compost during composting

[0067] like Figure 2 As shown in (a), the trends in total nitrogen content across all treatments were similar: peaking during the high-temperature period, then gradually declining during the cooling period, and then slightly increasing during the mature stage, ultimately exhibiting an overall downward trend. Total nitrogen content in all treatments was not significantly different from that in the control during both the high-temperature and cooling periods. However, the AP-10% treatment during the mature stage significantly increased total nitrogen content by 12.2% compared to the control (P < 0.05).

[0068] according to Figure 2 As shown in (b), total P content in composts under different treatments gradually increased. During the high temperature period, treatments with MAP significantly increased total P content by 24.1%-27.8% compared to the control (P < 0.05). At the end of composting, total P content increased by 9.0% and 7.7% in the MAP-5% and MAP-10% treatments, respectively, compared to the control. Across the three composting stages, total P content in composts with AP addition was consistently higher than that in composts with MAP addition.

[0069] Depend on Figure 2 As shown in Figure (c), the total K content in the MAP-10% treatment was consistently higher than that in the control during the three main stages of composting. At the end of composting, the total K content in the MAP-10% treatment increased by 19.8% compared to the control. During the thermophilic and mature stages of composting, the total K content in the treatment with high addition of hydrothermal carbonization liquid was higher than that in the treatment with low addition.

[0070] Changes in the total nutrient content of compost Figure 5 As shown in (a), there was no significant difference in total nutrients among the treatments.

[0071] The cumulative amount of ammonia volatilization during composting is as follows: Figure 5 As shown in (b), compared with the control, the cumulative amount of ammonia volatilization of AP-5%, AP-10%, and MAP-5% decreased, with the decrease rate ranging from 7.77% to 22.87%.

[0072] Changes in humic acid content during composting

[0073] like Figure 3As shown in (a), compared to the control, humic acid content decreased in the AP-5% and MAP-10% composts during both the high-temperature and cooling stages. MAP-5% and AP-10% increased humic acid content at all three composting stages. After composting, humic acid content in the control, AP-5%, AP-10%, MAP-5%, and MAP-10% treatments decreased from 19.7-26.8% at the start to 18.1-25.3%, respectively. Humic acid content in the MAP-5% and AP-10% treatments increased by 5.6% and 17.8%, respectively, compared to the control.

[0074] like Figure 3 Figure (b) shows that the humic acid content in the compost was lowest during the high temperature period, increased slightly during the cooling period, and reached its highest level during the final mature stage, showing an overall upward trend. After the composting was completed, the humic acid content in each treatment increased. The humic acid content in the control treatment and the treatment with hydrothermal carbonization solution ranged from 10.6% to 17.7%. Compared with the control, the humic acid content in the AP-10% treatment increased significantly by 5.0% (P < 0.05). Figure 3 As shown in (c), in contrast to humic acid, the content of fulvic acid showed a downward trend during the composting process. There was no significant difference in the fulvic acid content among the five treatments during the high temperature period, cooling period, and mature period of the composting. Figure 3 As shown in (d), the HA / FA ratios of each treatment gradually increased from 0.23-0.82 in the high temperature period to 1.70-2.87 in the mature period. Among them, the HA / FA ratios of the AP-10% treatment were higher than those of the control in all three composting periods.

[0075] Changes in dissolved organic matter in materials after composting

[0076] like Figure 4 As shown in Figure (c), quantitative PARAFAC analysis was performed on compost samples from different treatments. The results showed that component 1 (C1) is a humic acid-like substance, with excitation (EX) and emission (EM) wavelengths of approximately 325 nm and 450 nm, respectively. Component 2 (C2) also belongs to the UV-type humic substance category, with an EX / EM wavelength of approximately 325 / 400 nm. Component 3 (C3) is a high-molecular-weight organic compound, with an EX / EM peak at approximately 400 / 500 nm. Quantitative PARAFAC analysis was performed on compost samples from different treatments.

[0077] The relative concentrations of the three components are Figure 4As shown in (c), after the addition of hydrothermal carbonization liquid, the DOM content of all treatments increased compared with the control. Among them, the C1, C2 and C3 components of the AP-10% and MAP-10% treatments increased significantly by 44.6%-59.8%, 46.7%-63.9% and 19.8%-34.5%, respectively (P<0.05). This shows that hydrothermal carbonization liquid can accelerate the decomposition of organic matter and promote the formation of humus-like substances. In addition, compost with a high amount of hydrothermal carbonization liquid added has a better decomposition effect than compost with a low amount of hydrothermal carbonization liquid added. In order to further evaluate the effect of hydrothermal carbonization liquid on compost, the fluorescence parameters FI, HIX and BIX were calculated, as shown in the following figure: Figure 4 Compared with the control, the FI and BIX values of DOM treated with hydrothermal carbonization solution showed no significant difference, but HIX increased significantly (P<0.05).

[0078] The present invention uses chicken manure and poplar wood chips as raw materials to study the effects of different types and addition amounts of hydrothermal carbonization liquid on the degree of composting, nutrients, humic acid content and DOM in the compost. The study shows that the addition of acidic AP can reduce the pH of the compost pile in the early stage and increase the electrical conductivity of the compost pile. At the same time, the high addition of AP can also increase the total nitrogen and total humic acid content of the compost product and improve the HA / HA of the compost. The addition of MAP is more conducive to the improvement of the total phosphorus, total potassium and total nutrients of the compost product. In addition, both APs increased the DOM content of the compost and improved the humification index of the DOM. The results show that AP, as a compost conditioner, can improve the quality of compost without affecting the maturity of the compost, providing a new perspective for the harmless reuse of AP.

[0079] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form, and any technical solution obtained by equivalent replacement or equivalent transformation falls within the scope of protection of the present invention.

Claims

1. A method for improving the quality of organic fertilizer and reducing ammonia emissions by conditioning aerobic compost with hydrothermal carbonization liquid, characterized in that: The hydrothermal carbonization liquid is a liquid product of the hydrothermal carbonization reaction; the composting step comprises: using livestock and poultry manure, poplar wood chips and the hydrothermal carbonization liquid as fermentation raw materials, and piling them in an aerobic composting reactor for 20-35 days; a mixture of livestock and poultry manure and poplar wood chips is used as the initial pile material; The hydrothermal carbonization liquid is an initial hydrothermal carbonization liquid or a modified hydrothermal carbonization liquid. The preparation process of the hydrothermal carbonization liquid is as follows: using oak leaves as raw materials, placing them in a hydrothermal carbonization reactor, adjusting the mass volume ratio of agricultural and forestry waste to water to 1 kg: (8-10) L, the reaction temperature to 220-240° C., the pressure to 7-9 MPa, and the reaction time to 1-2 hours; collecting the liquid product after the reaction, filtering it, and the filtrate is the initial hydrothermal carbonization liquid; Add Mg to the initial hydrothermal carbonization solution 2+ and PO4 3- , adjust the solution pH to 9.5-10.5 to obtain struvite precipitate MgNH4PO4·6H2O, take the supernatant, adjust the pH to 7, and obtain a modified hydrothermal carbonization liquid; The pH of the modified hydrothermal carbonization liquid is neutral, and the ammonium nitrogen content of the modified hydrothermal carbonization liquid is lower than that of the initial hydrothermal carbonization liquid; The amount of the initial hydrothermal carbonization liquid or modified hydrothermal carbonization liquid added is 10% of the initial pile dry weight; The livestock and poultry excrement is dry livestock and poultry excrement, and the mass ratio of the livestock and poultry excrement to the poplar wood chips is 100:5-10.

2. The method for improving the quality of organic fertilizer and reducing ammonia emissions by conditioning aerobic compost with hydrothermal carbonization liquid according to claim 1, characterized in that: The hydrothermal carbonization liquid is added to the initial pile of materials at once, or is added to the initial pile of materials in batches.

3. The method for improving the quality of organic fertilizer and reducing ammonia emissions by conditioning aerobic compost with hydrothermal carbonization liquid according to claim 1, characterized in that: When the ratio of hydrothermal carbonization liquid to initial pile is not greater than 7L:100kg, the hydrothermal carbonization liquid is added to the initial pile at one time; when the ratio of hydrothermal carbonization liquid to initial pile is greater than 7L:100kg, the hydrothermal carbonization liquid is added to the initial pile in batches during turning, and the addition of the hydrothermal carbonization liquid in batches refers to 2-7 times. When the hydrothermal carbonization liquid is added for the first time, 40%-50% of the total amount of the hydrothermal carbonization liquid is added. Except for the first time, the amount of hydrothermal carbonization liquid added each time is the same.

4. The method for improving the quality of organic fertilizer and reducing ammonia emissions by conditioning aerobic compost with hydrothermal carbonization liquid according to any one of claims 1 to 3, characterized in that: The addition of hydrothermal carbonization liquid increased the maturity of the compost pile, the nutrient content of the pile and the humic acid content, and reduced the NH3 volatilization emission by 7.8-22.9%.

5. The method for improving the quality of organic fertilizer and reducing ammonia emissions by conditioning aerobic compost with hydrothermal carbonization liquid according to claim 2, characterized in that: The method for preparing the initial pile is as follows: dry livestock and poultry manure is uniformly mixed with poplar wood chips to form the initial pile.

6. The method of claim 1, wherein the method comprises: At the beginning of the aerobic composting step, the first addition of hydrothermal carbonization liquid is completed.

7. The method of claim 1, wherein the method comprises: The composting steps are: using livestock and poultry manure, poplar wood chips and hydrothermal carbonization liquid as fermentation raw materials, and piling them in an aerobic composting reactor for 30 days.

8. The method of claim 1, wherein the hydrothermal carbonization liquid is used to condition aerobic compost to improve the quality of organic fertilizer and reduce ammonia emissions. Turn the compost pile thoroughly every 3-6 days, and add appropriate amount of water each time to keep the moisture content at 55% to 60%.

Images