Method for reducing emission of nitrogenous pollution gas in kitchen waste composting process

Abstract

According to the method for reducing emission of the nitrogenous pollution gas in the kitchen waste composting process, straw biochar is used as an additive to inhibit generation of the nitrogenous gas and promote the nitrogenous gas to be converted into nitrate nitrogen, so that dissipation is reduced, and the content of nitrate nitrogen and humus in a compost product is increased. The method comprises the following steps: pretreating the kitchen waste to remove non-degradable substances such as bones and plastics; the method comprises the following steps: pyrolyzing agricultural wastes at 500 DEG C for 2-3 hours to prepare biochar, grinding and sieving; then adding the biochar into composting equipment, controlling the ventilation quantity to be 0.1-0.5 m / (min.m compost), and adopting a ventilation mode of blowing air for 0.5 hour and intermittent for 2.5 hours; according to the method, in-situ emission reduction of the nitrogen-containing gas is achieved by promoting the nitrification process and inhibiting denitrification and growth of nitrogen-containing gas producing bacteria, meanwhile, the compost maturity is improved, and the method has the advantages of being low in cost, easy and convenient to operate and capable of meeting the sustainable development requirement.

Description

Technical Field

[0001] This invention belongs to the field of harmless treatment technology of kitchen waste, specifically relating to a method for regulating and reducing nitrogen-containing gases during the composting process of kitchen waste. Background Technology

[0002] Food waste possesses both resource and hazard characteristics. It contains a large amount of biodegradable organic matter, including carbohydrates, proteins, and lipids. Aerobic composting is a process that utilizes microorganisms to break down large organic molecules into smaller ones. Aerobic composting mainly consists of a heating phase, a high-temperature phase, and a maturation phase. During this process, high temperatures are used to eliminate pathogens and inactivate weed seeds, while microorganisms convert large organic molecules into humus that plants can utilize. In the aerobic composting process of food waste, nitrogen is easily converted into nitrogen-containing gases such as ammonia and nitrous oxide. This not only leads to a decrease in the nitrogen content of the compost product but also causes serious environmental pollution. High concentrations of NH3 released into the atmosphere combine with acidic particulate matter to form fine particulate matter, which settles to the ground through precipitation, potentially negatively impacting plant and soil biodiversity and ecological functions. Nitrous oxide is a non-carbon greenhouse gas, but research indicates that its global warming trend is approximately 300 times that of carbon dioxide, posing a significant threat to the ecological environment. Its warming potential is large, and it has a significant impact on climate change. Therefore, controlling nitrogen-containing gases during composting is an urgent problem that needs to be solved in the process of environmental governance.

[0003] Currently, traditional solutions to this problem suffer from the following issues: Most nitrogen emission reduction methods still focus on off-site control, using methods such as absorption, neutralization, and biological oxidation at the end of the nitrogen-producing process to recover and utilize nitrogen, with few addressing in-situ control. Some treatment methods are poorly designed, leading to uncontrollable implementation costs, inability to meet large-scale composting needs, and serious resource waste. While reducing nitrogen emissions, the degree of humification in composting is also a crucial indicator. Some treatment methods fail to simultaneously reduce nitrogen emissions and achieve adequate humification, potentially causing defects in compost products when applied to soil. Therefore, the degree of humification is another indicator we need to pay attention to. Summary of the Invention

[0004] A method for regulating and reducing nitrogen-containing gases during the composting process of kitchen waste, in order to solve at least one of the aforementioned technical problems.

[0005] The technical solution of the present invention to solve the above problems includes the following steps:

[0006] 1. Specifically, the pretreated kitchen waste is mixed with biochar, placed in a composting device for fermentation and forced ventilation. The specific types of agricultural waste include rice husks, straw, cow and sheep manure, and waste branches, as shown in Table 1-1, which describes the physicochemical properties of composting raw materials.

[0007] 2. Specifically, the pyrolysis temperature of the vacuum furnace is 500-700℃, the firing time is 2-3 h, and the heating rate is 10 ℃ / min.

[0008] 3. Specifically, sort and crush the kitchen waste to a size of 1-2 cm, add an appropriate amount of sawdust to maintain the carbon-to-nitrogen mass ratio of the compost material between 25-30, the moisture content between 50%-60%, and the pH between 5-7.5.

[0009] 4. Specifically, the biochar added should be 10%-20% of the dry weight of the kitchen waste.

[0010] 5. Specifically, the ventilation volume is set to 0.1–0.5 m³. 3 / (min·m 3 (Composting), the ventilation and aeration frequency is: 0.5 hours of blowing and 2.5 hours of intermittent blowing, and the operating time is 40±2 days.

[0011] This invention utilizes the adsorption, redox, and catalytic properties of biochar to promote the growth of thermophilic bacteria during the high-temperature composting period, extending the high-temperature composting period. This facilitates the faster conversion of lignocellulose into humic matter, increases the humic acid content in the compost, and promotes the synergistic and directional conversion of carbon into humic matter, further improving the seed germination index of the compost product. The redox and catalytic properties of biochar can also promote the conversion of inorganic nitrogen (including ammonium nitrogen, nitrite nitrogen, ammonia, etc.) into nitrate nitrogen, thereby enhancing nitrification and reducing the production of nitrite oxide during denitrification, further improving the nitrogen fixation effect of aerobic composting of kitchen waste.

[0012] The beneficial effects of this invention are:

[0013] This invention utilizes collaborative innovation in waste-to-waste technology to transform useless agricultural straw waste into biochar, establishing a complete resource-based industrial chain from waste to additives to compost products. Furthermore, by controlling the process in situ, the biochar is implanted with aerobic nitrifying microorganisms within the compost pile itself, promoting the preservation of nitrogen in the compost as nitrate nitrogen while inhibiting denitrification and reducing the accumulation of ammonium nitrogen. This effectively eliminates the possibility of nitrogen gas generation, overcoming the drawbacks of high cost and complex operation associated with traditional methods. Ultimately, this significantly reduces nitrogen gas emissions during the composting process of kitchen waste, avoiding harm to human health and the environment while increasing the nitrogen content of the compost products. Attached Figure Description

[0014] Figure 1 The diagram shows the experimental setup used in the embodiment.

[0015] Figure 2 The graph shows the changes in ammonium nitrogen and nitrate nitrogen during different composting processes. (a) NH 4+ -N content, (b) NO 3 --N content;

[0016] Figure 3 Diagram illustrating the mechanism by which biochar reduces nitrogen emissions. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described in detail and completely below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0018] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0019] This invention discloses a method for reducing nitrogen-containing pollutant emissions during kitchen waste composting, mainly including the following steps:

[0020] Kitchen waste and sawdust were used as raw materials. The kitchen waste and sawdust were mixed at a wet weight ratio of 9:1. The specific physicochemical properties of the composting raw materials are shown in Table 1.

[0021] Table 1 Physicochemical Properties of Compost Raw Materials raw material Total carbon b (%) Total nitrogen b (%) pH value a Moisture content a (%) Ash content a (%) Food waste 48.06 1.47 5.12 60.0 0.93 Biochar 44.06 1.21 8.14 4.9 10.23 sawdust 45.46 0.14 7.30 9.6 5.21 Note: a, based on wet basis; b, based on dry basis.

[0022] Four treatment groups were set up: the control group with no biochar added (0% BC), and the experimental groups with 10%, 15%, and 20% biochar added (based on the dry weight of kitchen waste), respectively.

[0023] The total wet weight of each group of materials is 15 kg, and the moisture content is adjusted to 50%–65%.

[0024] The ventilation rate is 0.2 L / (kg·min), the aeration interval is 3.5 h, and the composting cycle is 42 days.

[0025] The heap was turned over once every 3 days in the first week, and once a week thereafter.

[0026] Regularly sample and measure indicators such as pH, GI, NH4⁺-N, NO3⁻-N, C / N ratio, and nitrogen-containing gas emissions.

[0027] The composting device is a self-made sealed foam box with a built-in aeration system and a blower for ventilation.

[0028] Basic physicochemical properties determination: temperature, pH, seed germination index (GI), and carbon-nitrogen ratio (C / N), etc.

[0029] Nitrogen components and gas collection: NH4⁺-N and NO3⁻-N were determined by ultraviolet spectrophotometry; NH3 was determined by boric acid absorption-sulfuric acid titration; N2O was analyzed by gas chromatography.

[0030] Microbial community and nitrogen function gene determination: Samples were collected at different time points, DNA was extracted and metagenomic sequencing was performed to analyze microbial composition and nitrogen metabolism-related functional genes.

[0031] Data statistics and significance analysis were performed using Excel and SPSS, and graphing was conducted using software such as Origin, Gephi, and GraphPadPrism. High-throughput data analysis was completed on the Meiji Cloud platform.

[0032] The specific embodiments described above have provided a detailed explanation of the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for reducing nitrogen-containing pollutant emissions during the composting process of kitchen waste, characterized in that, This includes biochar preparation, pretreatment of kitchen waste, biochar addition, and composting operation; by enhancing aerobic nitrification, strengthening humification, and inhibiting the production of nitrous oxide, in-situ control of nitrogen-containing gases is achieved, thereby increasing the nitrate nitrogen content of compost products.

2. The method according to claim 1, characterized in that, The agricultural waste includes rice husks, straw, cow and sheep manure, or discarded tree branches.

3. The method according to claim 1, characterized in that, The biochar preparation conditions are as follows: pyrolysis temperature 500–700℃, time 2–3 h, heating rate 10 ℃ / min, and grinding and sieving after pyrolysis.

4. The method according to claim 1, characterized in that, The pretreatment includes sorting non-degradable materials, filtering leachate and oil-water mixtures, crushing to 1–2 cm, and adding sawdust to adjust the carbon-to-nitrogen ratio to 25–30, moisture content to 50%–60%, and pH to 5–7.

5.

5. The method according to claim 1, characterized in that, The amount of biochar added is 10%–20% of the dry weight of the kitchen waste, and it should be mixed thoroughly after addition.

6. The method according to claim 1, characterized in that, The ventilation rate for composting operation is 0.1–0.5 m³ / (min·m³ compost), using a blower method of 0.5 h followed by intermittent 2.5 h, and the operation lasts for 40±2 days.

7. The method according to claim 1, characterized in that, Biochar regulates the microbial environment, promoting the conversion of organic nitrogen and ammonium nitrogen into nitrate nitrogen, and reducing the accumulation of ammonium nitrogen and the volatilization of ammonia.

8. The method according to claim 1, characterized in that, Biochar is used to regulate the temperature of the compost pile, prolong the high-temperature period, and promote the conversion of organic matter into humus.

9. The method according to claim 1, characterized in that, Biochar is used to regulate denitrifying microorganisms, inhibiting the generation of nitrous oxide and promoting its reduction to nitrogen gas.

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