Invasive organism selenium-rich compost formula and preparation method

Abstract

The invention discloses an invasive organism selenium-rich compost formula and a preparation method. According to the invading organism selenium-rich compost formula, an invading plant mikania micrantha and invading animal ampullaria gigas meat are used as compost raw materials, and selenium elements in different forms are used as selenium sources. The compost formula can prolong the high-temperature period of the compost, accelerate the composting process, degrade more and more organic substances, increase the nutrient content of the compost and reduce the emission of greenhouse gases in the composting process; therefore, the problems of short high-temperature period duration, low organic matter degradation efficiency and greenhouse gas emission in the traditional composting process are solved. The invention not only provides a new method for resource utilization of invasive organisms, but also enables the compost to have higher nutritional value and ecological value through an exogenous selenium application mode.

Description

Technical Field

[0001] The present invention relates to the technical field of low-carbon resource utilization of invasive biological waste, and more specifically, to a formula for selenium-enriched compost of invasive biological waste, wherein the selenium-enriched compost of invasive biological waste is prepared by composting the invasive plant Mikania micrantha and the invasive animal Pomacea canaliculata snail meat with selenium in different forms as selenium sources. Background Art

[0004] Mikania micrantha is a perennial climbing plant of the Asteraceae family, native to Central and South America. It grows very fast and is known as a "vine that grows a mile a minute". Mikania micrantha entangles surrounding trees and shrubs, hindering the photosynthesis of the host plants and releasing allelopathic substances to inhibit their growth, thus causing the death of the host plants and causing serious damage to local biodiversity. In 2004, the World Conservation Union (IUCN) listed it as one of the world's 100 most serious invasive alien species.

[0005] At present, biological invasion prevention and control mainly adopts artificial prevention, chemical prevention and biological prevention methods, but these methods have disadvantages such as high cost, environmental damage and unstable effect. Developing technology for resource utilization of invasive organisms is a potential method for controlling invasive organisms, which can not only effectively control the number of invasive organisms, but also reduce the cost of prevention and control. Invasive plants can be used as animal feed. For example, the alien invasive plant Leucaena leucocephala has rich nutritional value, and its branches have a protein content of up to 31%, which is often used as an important feed. At present, there are no reports on the use of invasive organisms Pomacea canaliculata and Mikania micrantha for composting in the existing technology; at the same time, the problems of short duration of high temperature period, low efficiency of organic matter degradation and greenhouse gas emissions in the traditional composting process also need to be solved urgently. Summary of the invention

[0006] The purpose of the present invention is to overcome the above-mentioned defects and shortcomings in the prior art and provide a formula for selenium-enriched compost of invasive organisms.

[0007] Another object of the present invention is to provide a method for preparing invasive organism selenium-enriched compost based on the above-mentioned invasive organism selenium-enriched compost formula.

[0008] Another object of the present invention is to provide selenium-rich compost of invasive organisms prepared by the preparation method.

[0009] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0010] A formula for selenium-rich composting of invasive organisms comprises composting materials and selenium sources, wherein the composting materials are micrantha and Pomacea canaliculata meat; the carbon-nitrogen ratio of the composting materials is 20-30:1; the selenium source consists of sodium selenate, sodium selenite and / or nano-selenium, and the addition amount is 1.5-4.5 mg / kg of the composting materials.

[0011] In the compost material of the present invention, the meat of Pomacea canaliculata is used as the nitrogen source of compost, and its protein content is as high as 62%, and it also contains a large amount of minerals and vitamins. As the carbon source of compost, Mikania micrantha has a high organic carbon content, which can reach 440.46g / kg, while the conventional compost carbon source is mostly agricultural wastes such as rice straw, corn straw, chestnut shell and sawdust, and their organic carbon contents are only 377.9g / kg, 371.7g / kg, 272.3g / kg and 347.1g / kg respectively, which has better raw material advantages. And controlling the carbon-nitrogen ratio of the compost material is crucial for the success of composting. By selecting Pomacea canaliculata and Mikania micrantha as compost raw materials and adjusting the carbon-nitrogen ratio, the quality and efficiency of composting can be improved, and the effective utilization of invasive organisms can be achieved. In view of the problems of short duration of high temperature period, low efficiency of organic matter degradation and greenhouse gas emission in the traditional composting process, the present invention can prolong the high temperature period of composting, accelerate the composting maturity process, increase the nutrient content of composting and reduce the emission of greenhouse gases in the composting process by adding different selenium sources, so that the compost has higher nutritional value and ecological value. The invasive organism selenium-enriched composting formula can play a synergistic role in improving the quality and efficiency of compost products by invading the composting organisms and combining with the trace element selenium.

[0012] Since the influence of selenium addition on composting effect is complicated, it depends on multiple factors such as the amount of selenium added, the properties of compost raw materials, and composting process. In practical applications, it is necessary to reasonably control the amount of selenium added to give full play to its positive effect. The present invention is aimed at the problems of short duration of high temperature period, low efficiency of organic matter degradation, and greenhouse gas emission in traditional composting process, and reasonably adopts multiple trace elements of selenium for preparation to obtain a multifunctional series of formulas, which can extend the high temperature period of composting, accelerate the composting maturity process, increase the nutrient content of composting, and reduce the emission of greenhouse gases in the composting process.

[0013] Furthermore, the selenium source is composed of nano-selenium and sodium selenate, the amount of nano-selenium added is 1.13-1.36 mg / kg of compost material, and the amount of sodium selenate added is 1.58-1.95 mg / kg of compost material. The obtained formula is highly efficient and can be used to extend the high temperature period of composting, accelerate the composting maturity process, degrade organic matter more fully, and degrade more organic matter.

[0014] Preferably, the amount of nano-selenium added is 1.21 mg / kg of compost material, and the amount of sodium selenate added is 1.92 mg / kg of compost material.

[0015] Furthermore, the selenium source is composed of nano-selenium and sodium selenite, the nano-selenium addition amount is 1.37-1.51 mg / kg of compost material, and the sodium selenite addition amount is 1.08-1.25 mg / kg of compost material. The obtained formula is nutritious, which can be used to improve the degradation rate of organic matter, increase the nutrient content of compost, increase the total nitrogen, total phosphorus, total potassium and nutrient content of compost, and increase the ammonium nitrogen and nitrate nitrogen content of compost.

[0016] Preferably, the amount of nano-selenium added is 1.47 mg / kg of compost material, and the amount of sodium selenite added is 1.16 mg / kg of compost material.

[0017] Furthermore, the selenium source is composed of nano-selenium, sodium selenate and sodium selenite, the amount of nano-selenium added is 0.85-1.12 mg / kg of compost material, the amount of sodium selenate added is 1.12-1.57 mg / kg of compost material, and the amount of sodium selenite added is 0.81-1.07 mg / kg of compost material. The obtained formula is low-carbon and can be used to reduce the emission of greenhouse gases such as nitrous oxide during composting.

[0018] Preferably, the added amount of nano-selenium is 0.98 mg / kg of compost material, the added amount of sodium selenate is 1.36 mg / kg of compost material, and the added amount of sodium selenite is 0.99 mg / kg of compost material.

[0019] Furthermore, the carbon-nitrogen ratio of the compost material is 21:1, that is, the mass ratio of Mikania micrantha to Pomacea canaliculata meat is 3:1.

[0020] The present invention also provides the use of any of the above-mentioned invasive organism selenium-rich compost formulas in preparing invasive organism selenium-rich compost. The invasive plant Mikania micrantha and the invasive animal Pomacea canaliculata meat are mixed as raw materials in proportion, different forms of selenium are used as selenium sources, and the raw materials are subjected to high-temperature decomposition and decomposition by aerobic composting to prepare low-carbon emission selenium-rich invasive organism compost.

[0021] The present invention also provides a method for preparing invasive organism selenium-enriched compost based on any of the above invasive organism selenium-enriched compost formulas, comprising the following steps:

[0022] S1. drying and crushing the cleaned Mikania micrantha; washing the separated Pomacea canaliculata meat;

[0023] S2. Place the compost material described in step S1 into a compost container at a carbon-nitrogen ratio of 20 to 30:1, control the moisture content to 50% to 70%, mix well, and evenly spray 1.5 to 4.5 mg / kg of the total weight of the compost material with a selenium source solution, and then aerobically compost at 30 to 35° C. for 40 to 50 days to obtain invasive bio-selenium-rich compost.

[0024] Preferably, the drying temperature in step S1 is 60-80° C., and the drying time is 24-48 hours.

[0025] Preferably, the compost container in step S2 is a compost barrel, and the outer periphery of the compost barrel is wrapped with an insulation belt for insulation. A digital thermometer with a probe is inserted into the center of the pile to monitor the temperature in the barrel, and a stainless steel screen is placed at the bottom of the compost tank to support the compost material. At the same time, a drain valve is provided at the bottom of the barrel. The gas is sent to the lower layer of the material filter plate through a ventilation pipe via a ventilation pump. An exhaust port is provided at the top, and a three-way valve is connected in sequence with a rubber hose for the collection of methane and nitrous oxide.

[0026] Preferably, the moisture content of the material in the composting container in step S2 is adjusted to 60%.

[0027] The present invention also provides selenium-rich compost of invasive organisms prepared by any of the above-mentioned preparation methods.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention utilizes the selenium-rich composting formula of invasive organisms, takes the invasive plant Mikania micrantha and the invasive animal Pomacea canaliculata meat as composting raw materials, and uses selenium in different forms as selenium sources. The composting formula can extend the high temperature period of composting, accelerate the composting maturity process, degrade more and more organic matter, increase the nutrient content of composting, and reduce the emission of greenhouse gases during the composting process, thereby overcoming the problems of short high temperature period duration, low organic matter degradation efficiency, and greenhouse gas emission in the traditional composting process. The present invention not only provides a new method for the resource utilization of invasive organisms, but also makes the compost have higher nutritional value and ecological value by applying selenium from an external source. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The effect of high-efficiency formula on the temperature of selenium-enriched composting of invasive organisms.

[0031] Figure 2 The effect of high-efficiency formula on pH of selenium-enriched compost of invasive organisms.

[0032] Figure 3 The effect of high-efficiency formula on the electrical conductivity of selenium-enriched compost of invasive organisms.

[0033] Figure 4 The effect of high-efficiency formula on the germination index of selenium-enriched compost for invasive organisms.

[0034] Figure 5 The effect of high-efficiency formula on the ash content of selenium-enriched compost of invasive organisms.

[0035] Figure 6 Effects of nutrient-based formulations on invasive organisms in selenium-enriched compost organic matter.

[0036] Figure 7 Effects of nutritional formula on nutrient content of selenium-enriched compost for invasive organisms.

[0037] Figure 8 Effect of nutrient formula on ammonium nitrogen content in selenium-enriched compost of invasive organisms.

[0038] Fig. 9 Effect of nutrient formula on nitrate-nitrogen content in selenium-enriched compost of invasive organisms.

[0039] Fig.10 Effects of low-carbon formulations on nitrous oxide emission fluxes from selenium-enriched composts of invasive organisms.

[0040] Fig.11 Effects of low-carbon formulations on the cumulative nitrous oxide emissions from selenium-enriched composts of invasive organisms.

[0041] Fig.12 Effect of low-carbon formulations on the global warming potential of selenium-enriched composts containing invasive organisms.

[0042] Fig.13 The effect of low-carbon formula on the functional genes of greenhouse gas emissions from selenium-enriched composting of invasive organisms. DETAILED DESCRIPTION

[0043] The present invention is further described below in conjunction with the accompanying drawings and specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0044] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0045] Example 1 Effect of high-efficiency formula on temperature of selenium-enriched compost of invasive organisms

[0046] (1) The invasive plant Mikania micrantha was collected, dried in a constant temperature forced air drying oven at 60°C for 48 h, crushed into 2-3 cm by a grinder, and stored in a dry place for later use; the invasive animal Pomacea canaliculata was collected, frozen to death in a -20°C refrigerator, and the snail meat was separated with tweezers and placed in a -20°C refrigerator for later use.

[0047] (2) The materials in step (1) are mixed evenly according to a carbon-nitrogen ratio of 21:1, that is, Mikania micrantha:Pomacea canaliculata meat=3:1 (mass ratio), and the moisture content of the materials is adjusted to 60%.

[0048] (3) Experimental setting: control (CK) and Se treatment. In the Se treatment, a selenium mixed solution was uniformly sprayed, and the selenium mixed solution contained 1.21 mg / kg of nano-selenium and 1.92 mg / kg of sodium selenate (based on the total weight of the materials). In the control (CK), no selenium solution was sprayed. Both the control and Se treatments used an air pump to continuously supply oxygen, and the temperature of the temperature control sheet was controlled at 30°C. Composting began, and the composting days were 50 days.

[0049] (4) During the composting period, the center temperature of the pile was recorded every day using a probe thermometer (MBS-spwdj, Yancheng Yunlian Intelligent Technology Co., Ltd., Zhejiang, China).

[0050] Temperature dynamics during composting Figure 1 As shown in the figure, the composting process of Se treatment experienced four stages: heating, high temperature, cooling, and maturity. The temperature trend was first rising, then falling, and finally approaching room temperature. On the third day of composting, the temperature of the control and Se treatments rose rapidly and entered the high temperature period (>50℃) on the fourth day. The highest temperature of the Se treatment (56.0℃) was higher than that of the control (55.5℃) ( Figure 1 a). In terms of the duration of the high temperature period, the high temperature period of the Se treatment (10 days) was longer than that of the control (8 days) ( Figure 1 b). After the high temperature period, the temperature of the pile began to drop, and on the 43rd day, the temperature of the pile in the Se treatment was close to room temperature. The temperature rise in the early stage of composting is because a large amount of organic matter in the material is rapidly degraded and releases heat. Se treatment prolongs the high temperature period of composting because the addition of selenium promotes the growth of microorganisms, thereby accelerating the maturity of the compost. In addition, high temperature can kill insect eggs and weed seeds, which is conducive to the composting reaching the harmless technical standards.

[0051] Example 2 Effect of high-efficiency formula on pH and conductivity of selenium-enriched compost of invasive organisms

[0052] (1) The invasive plant Mikania micrantha was collected, dried in a constant temperature forced air drying oven at 60°C for 48 h, crushed into 2-3 cm by a grinder, and stored in a dry place for later use; the invasive animal Pomacea canaliculata was collected, frozen to death in a -20°C refrigerator, and the snail meat was separated with tweezers and placed in a -20°C refrigerator for later use.

[0053] (2) The materials in step (1) are mixed evenly according to a carbon-nitrogen ratio of 21:1, that is, Mikania micrantha:Pomacea canaliculata meat=3:1 (mass ratio), and the moisture content of the materials is adjusted to 60%.

[0054] (3) Experimental setting: control (CK) and Se treatment. In the Se treatment, a selenium mixed solution was uniformly sprayed, and the selenium mixed solution contained 1.21 mg / kg of nano-selenium and 1.92 mg / kg of sodium selenate (based on the total weight of the materials). In the control (CK), no selenium solution was sprayed. Both the control and Se treatments used an air pump to continuously supply oxygen, and the temperature of the temperature control sheet was controlled at 30°C. Composting began, and the composting days were 50 days.

[0055] (4) After composting begins, compost samples are collected on days 0, 3, 7, 14, 21, 28, 35, 42, and 50 and stored in a 4°C refrigerator for testing. Compost samples are collected using the quartering method and are evenly distributed. Samples are taken from 5 cm below the compost surface. The compost must be turned upside down and mixed thoroughly before collection.

[0056] (5) Take out samples from different composting periods from a 4°C refrigerator and place them in centrifuge tubes. Add ultrapure water at a solid-liquid ratio of 1:10. Place the centrifuge tubes in a constant temperature shaker and shake at 180 r / min for 2 h for extraction. After shaking, centrifuge at 10,000 r / min for 10 min. The supernatant obtained by filtration is the compost extract.

[0057] (6) The pH and conductivity of the extract were measured using a pH meter (PHSJ-4F, Shanghai Yidian Scientific Instrument Co., Ltd., Shanghai, China) and a conductivity meter (SW302, Zhejiang Shangyu Huafeng Hardware Co., Ltd., Zhejiang, China), respectively.

[0058] Dynamic changes of pH during composting Figure 2 As shown, in the early stage of composting, the pH value of the Se treatment increased rapidly with the increase of temperature. On the 14th day of composting, the pH of the Se treatment was significantly higher than that of the control (P < 0.05), and the pH of the control rose more slowly than that of the Se treatment. The pH of the control and Se treatment began to decrease on the 35th day. At the end of composting, the pH of the Se treatment was between 7.98 and 8.18, meeting the maturity requirements of composting. The increase in pH during composting is due to the rapid decomposition of organic matter and the accumulation of ammonia. The pH of the Se treatment was significantly higher than that of the control, indicating that the organic matter in the compost treated with Se was more fully decomposed than that in the control.

[0059] The dynamic changes of conductivity during composting are as follows Figure 3As shown in the figure, the conductivity of the Se-treated compost increased rapidly at the beginning and reached the maximum value on the 14th day. The conductivity of the Se-treated compost (4877.5μS / cm) was higher than that of the control (4582.5μS / cm). From the 14th day, the conductivity of the control and Se-treated compost began to decrease and stabilized at the end. Finally, the conductivity of the Se-treated compost was higher than that of the control, reaching 3611.3μS / cm, which met the compost maturity standard. In the early stage of composting, the rapid degradation of composting materials released a large amount of mineral salts, and the rapid increase in the temperature of the compost and ventilation reduced the water content of the compost, increased the concentration of soluble nutrients, and thus increased the conductivity. The conductivity of the Se-treated compost was higher than that of the control, indicating that it released more mineral salts and the organic matter was more fully degraded.

[0060] Example 3 Effect of high-efficiency formula on germination index and ash content of selenium-enriched compost of invasive organisms

[0061] (1) The invasive plant Mikania micrantha was collected, dried in a constant temperature forced air drying oven at 60°C for 48 h, crushed into 2-3 cm by a grinder, and stored in a dry place for later use; the invasive animal Pomacea canaliculata was collected, frozen to death in a -20°C refrigerator, and the snail meat was separated with tweezers and placed in a -20°C refrigerator for later use.

[0062] (2) The materials in step (1) are mixed evenly according to a carbon-nitrogen ratio of 21:1, that is, Mikania micrantha:Pomacea canaliculata meat=3:1 (mass ratio), and the moisture content of the materials is adjusted to 60%.

[0063] (3) Experimental setting: control (CK) and Se treatment. In the Se treatment, a selenium mixed solution was uniformly sprayed, and the selenium mixed solution contained 1.21 mg / kg of nano-selenium and 1.92 mg / kg of sodium selenate (based on the total weight of the materials). In the control (CK), no selenium solution was sprayed. Both the control and Se treatments used an air pump to continuously supply oxygen, and the temperature of the temperature control sheet was controlled at 30°C. Composting began, and the composting days were 50 days.

[0064] (4) After composting begins, compost samples are collected on days 0, 3, 7, 14, 21, 28, 35, 42, and 50 and stored in a refrigerator at 4°C. Compost samples are collected using the quartering method and are evenly distributed. Samples are taken from 5 cm below the compost surface. The compost must be turned upside down and mixed thoroughly before collection.

[0065] (5) Determination of germination index (GI): Place the 50th day sample in a centrifuge tube, add ultrapure water at a solid-liquid ratio of 1:10, place the centrifuge tube in a constant temperature shaker, shake at 180r / min for 2h for extraction, centrifuge at 10000r / min for 10 minutes after shaking, and filter the supernatant to obtain the compost extract. First, place a filter paper of appropriate size in a culture dish, put 20 lettuce (Lactuca sativavar.ramosa Hort.) seeds with full grains and uniform size in the culture dish, add 7mL of compost extract to each culture dish, and set a blank control of 7mL of pure water. Place the culture dish in a constant temperature incubator at 25℃ and culture it in the dark for 48h. After the seed germination is completed, measure the number of seeds germinated and the length of the seed root. Calculate the seed germination index (GI) using formula (1).

[0066]

[0067] (7) Determination of ash content (VS): Using the differential weight method, the fresh compost sample was placed in a 105°C oven and dried to constant weight (M1, g). After constant weight was reached, the crucible containing the sample was placed in a muffle furnace and dried at 600°C for 2 h. After cooling to room temperature, the crucible was taken out and weighed (M2, g). The VS was calculated according to formula (2):

[0068]

[0069] The changes of germination index of compost are as follows Figure 4 As shown in the figure, at the end of composting, the germination index (GI) of the control and Se treatments were 89.0% and 94.4%, respectively, and the Se treatment was 6% higher than the control (P < 0.05). The germination index is an indicator for evaluating the maturity and toxicity of compost. At the end of composting, the GI of the Se treatment was higher than 80%, which met the compost maturity standard. Compared with the control, the GI of the Se treatment was higher, indicating that the addition of selenium improved the maturity of the compost and the nutritional quality of the compost.

[0070] The changes of ash content in compost are as follows: Figure 5 As shown, during the composting process, the ash content in the Se treatment decreased more than that in the control, with a decrease of 34%, indicating that more organic matter was degraded during the composting process.

[0071] Example 4 Effect of nutrient formulation on organic matter and nutrient content of selenium-enriched compost of invasive organisms

[0072] (1) The invasive plant Mikania micrantha was collected, dried in a constant temperature forced air drying oven at 60°C for 48 h, crushed into 2-3 cm by a grinder, and stored in a dry place for later use; the invasive animal Pomacea canaliculata was collected, frozen to death in a -20°C refrigerator, and the snail meat was separated with tweezers and placed in a -20°C refrigerator for later use.

[0073] (2) The materials in step (1) are mixed evenly according to a carbon-nitrogen ratio of 21:1, that is, Mikania micrantha:Pomacea canaliculata meat=3:1 (mass ratio), and the moisture content of the materials is adjusted to 60%.

[0074] (3) Experimental setting: control (CK) and Se treatment. In the Se treatment, a selenium mixed solution was uniformly sprayed, and the selenium mixed solution contained 1.47 mg / kg of nano-selenium and 1.16 mg / kg of sodium selenite (based on the total weight of the materials). In the control (CK), no selenium solution was sprayed. Both the control and Se treatments used an air pump to continuously supply oxygen, and the temperature of the temperature control sheet was controlled at 30°C. Composting began, and the composting days were 50 days.

[0075] (4) After composting begins, compost samples are collected on days 0, 3, 7, 14, 21, 28, 35, 42, and 50 and stored in a refrigerator at 4°C. Compost samples are collected using the quartering method and are evenly distributed. Samples are taken from 5 cm below the compost surface. The compost must be turned upside down and mixed thoroughly before collection.

[0076] (5) The organic matter content of compost was determined by the potassium dichromate-concentrated sulfuric acid external heating method; the total nitrogen content was determined by the semi-micro Kjeldahl method; the total phosphorus content was determined by the potassium hydroxide fusion-molybdenum antimony counter colorimetric method; and the total potassium content was determined by the potassium hydroxide fusion-flame photometry method.

[0077] Changes in organic matter content during composting Figure 6 As shown in the figure, the Se treatment showed a downward trend during the composting process. In the first three days of composting, the organic matter content in the Se treatment was higher, and the degradation rate of organic matter was significantly accelerated from the 7th day, while the degradation rate of organic matter slowed down in the later stage of composting. At the end of composting, the organic matter content in the Se treatment was significantly lower than that in the control (P < 0.05), reaching 8.7%. This shows that the addition of selenium makes the compost material degrade more fully.

[0078] Changes in nutrient content during composting Figure 7 As shown in the results, compared with the control, the total nitrogen and total phosphorus contents of the Se treatment were significantly increased (P < 0.05); the total potassium content of the Se treatment increased by 12% compared with the control. At the end of the experiment, the total nutrient contents of the control and Se treatment were 8.7% and 10.1%, respectively. This shows that the Se-treated compost meets the nutrient standards of organic fertilizers, and the addition of selenium increases the total nitrogen, total phosphorus, total potassium and nutrient contents of the compost.

[0079] Example 5 Effect of nutrient formula on ammonium nitrogen and nitrate nitrogen content in selenium-enriched compost of invasive organisms

[0080] (1) The invasive plant Mikania micrantha was collected, dried in a constant temperature forced air drying oven at 60°C for 48 h, crushed into 2-3 cm by a grinder, and stored in a dry place for later use; the invasive animal Pomacea canaliculata was collected, frozen to death in a -20°C refrigerator, and the snail meat was separated with tweezers and placed in a -20°C refrigerator for later use.

[0081] (2) The materials in step (1) are mixed evenly according to a carbon-nitrogen ratio of 21:1, that is, Mikania micrantha:Pomacea canaliculata meat=3:1 (mass ratio), and the moisture content of the materials is adjusted to 60%.

[0082] (3) Experimental setting: control (CK) and Se treatment. In the Se treatment, a selenium mixed solution was uniformly sprayed, and the selenium mixed solution contained 1.47 mg / kg nano-selenium and 1.16 mg / kg sodium selenite (based on the total weight of the materials). In the control (CK), no selenium solution was sprayed. Both the control and Se treatments used an air pump to continuously supply oxygen, and the temperature of the temperature control sheet was controlled at 30°C. Composting began, and the composting days were 50 days.

[0083] (4) After composting begins, compost samples are collected on days 0, 3, 7, 14, 21, 28, 35, 42, and 50 and stored in a refrigerator at 4°C. Compost samples are collected using the quartering method and are evenly distributed. Samples are taken from 5 cm below the compost surface. The compost must be turned upside down and mixed thoroughly before collection.

[0084] (5) The ammonium nitrogen content of compost is determined by the phenol-hypochlorite (or salicylic acid-hypochlorite) colorimetric method; the nitrate nitrogen content is determined by the ultraviolet spectrophotometric method.

[0085] Effects of ammonium nitrogen on biocomposting Figure 8 As shown in the figure, in the initial stage of composting, the ammonium nitrogen content of Se treatment increased rapidly and reached a peak on the third day. The ammonium nitrogen content of Se treatment increased by 4.9% compared with the control. As the composting progressed, the ammonium nitrogen content of Se treatment continued to decrease. At the end of composting, the ammonium nitrogen content was 0.16 mg / g, which was lower than 0.4 mg / g and met the standard of compost maturity. The decrease in ammonium nitrogen was due to the emission of ammonia and the progress of nitrification. Compared with the control of 0.12 mg / g, the addition of selenium increased the ammonium nitrogen content of the compost.

[0086] Effects of nitrate nitrogen on composting by invasive organisms Fig. 9 As shown in the figure, in contrast to ammonium nitrogen, the nitrate nitrogen content in the Se treatment was low in the early stage of composting, but increased significantly in the later stage. At the end of composting, the nitrate nitrogen content in the Se treatment increased by 24% compared with the control.

[0087] Example 6 Effect of low-carbon formula on greenhouse gas emissions from selenium-enriched composting of invasive organisms

[0088] (1) The invasive plant Mikania micrantha was collected, dried in a constant temperature forced air drying oven at 60°C for 48 h, crushed into 2-3 cm by a grinder, and stored in a dry place for later use; the invasive animal Pomacea canaliculata was collected, frozen to death in a -20°C refrigerator, and the snail meat was separated with tweezers and placed in a -20°C refrigerator for later use.

[0089] (2) The materials in step (1) are mixed evenly according to a carbon-nitrogen ratio of 21:1, that is, Mikania micrantha:Pomacea canaliculata meat=3:1 (mass ratio), the moisture content of the materials is adjusted to 60%, and the selenium mixed solution is evenly sprayed.

[0090] (3) Experimental setting: control (CK) and Se treatment. In the Se treatment, a selenium mixed solution was uniformly sprayed, and the selenium mixed solution contained 0.98 mg / kg of nano-selenium, 1.36 mg / kg of sodium selenate, and 0.99 mg / kg of sodium selenite (based on the total weight of the materials). In the control (CK), no selenium solution was sprayed. Both the control and Se treatments used an air pump to continuously supply oxygen, and the temperature of the temperature control sheet was controlled at 30°C. Composting began, and the composting days were 50 days.

[0091] (4) The collection of greenhouse gases (methane and nitrous oxide) during the composting process must be completed between 9:00 and 11:00 every day. The oxygen pump must be turned off before collecting gas samples. After stopping ventilation for 30 minutes, the gas is collected and stored in a closed composting device using a 50 ml syringe. When collecting gas, gas samples are collected with a syringe at 0, 10, 20, and 30 minutes, 20 ml each time, and the concentrations of methane and nitrous oxide in the gas samples are determined using a gas chromatograph with a hydrogen ion flame detector. The calculation formula for composting greenhouse gas emission rate and cumulative emissions is (3):

[0092] V=(Δc / Δt)×(M / Vs)×(P / P0)×(273 / T)×V (3)

[0093] Where V is the greenhouse gas emission rate of each treatment (mg / d). Δc / Δt is the change in gas concentration per unit time (day) (ppm); M is the molecular mass of the relevant gas (16 and 44 g for methane and nitrous oxide, respectively); Vs is the volume occupied by 1 mole of gas at standard temperature and pressure (22.4 L); P is the atmospheric pressure (bar); P0 is the standard pressure (1.01×105 Pa); V is the headspace volume (L); T is the temperature in the compost bin (K), in Kelvin;

[0094] The cumulative greenhouse gas emissions (mg) are calculated using the trapezoidal integration rule, and the formula is as follows:

[0095]

[0096] Where F is the cumulative emission of methane or nitrous oxide (mg); ta and tb are the intervals between two measurement times (days); Fta and Ftb are the emission fluxes on the same day of the two measurement times (mg), respectively.

[0097] On a 100-year scale, the global warming potential (GWP) of methane is 25 times that of carbon dioxide, and nitrous oxide is 298 times that of carbon dioxide. The GWP calculation formula is as follows:

[0098]

[0099] In the formula, F CH4 is the cumulative methane emission during composting (mg); F N2O is the cumulative emission of nitrous oxide during the composting process (mg).

[0100] The emission flux and cumulative emission of nitrous oxide during composting are as follows: Fig.10 and Fig.11 As shown in the figure, in the early stage of composting, the emission flux of nitrous oxide in Se treatment was at a low level. When the composting was carried out for about 25 days, the emission rate of nitrous oxide began to gradually increase. The control and Se treatments reached the emission peak on the 34th day. The emission rate of nitrous oxide in Se treatment was 36.1% lower than that in control. At the end of the experiment, the accumulation of nitrous oxide in Se treatment was 29% lower than that in control. This shows that the addition of selenium inhibited the emission of nitrous oxide.

[0101] In this experiment, the cumulative emissions of methane and nitrous oxide during the composting process were converted into carbon dioxide equivalent (gCO2-eqkg) as follows: Fig.12 As shown in the results, the addition of selenium reduced the impact of composting on the global warming potential, among which the global warming potential of Se-treated composting was reduced by 28% compared with the control (P < 0.05). Therefore, selenium has a mitigation effect on greenhouse gas emissions during the composting process of Mikania micrantha and Pomacea canaliculata.

[0102] Example 7 Effect of low-carbon formula on greenhouse gas emission functional genes of selenium-enriched compost of invasive organisms

[0103] (1) The invasive plant Mikania micrantha was collected, dried in a constant temperature forced air drying oven at 60°C for 48 h, crushed into 2-3 cm by a grinder, and stored in a dry place for later use; the invasive animal Pomacea canaliculata was collected, frozen to death in a -20°C refrigerator, and the snail meat was separated with tweezers and placed in a -20°C refrigerator for later use.

[0104] (2) The materials in step (1) are mixed evenly according to a carbon-nitrogen ratio of 21:1, that is, Mikania micrantha:Pomacea canaliculata meat=3:1 (mass ratio), and the moisture content of the materials is adjusted to 60%.

[0105] (3) Experimental setting: control (CK) and Se treatment. In the Se treatment, a selenium mixed solution was uniformly sprayed, and the selenium mixed solution contained 0.98 mg / kg of nano-selenium, 1.36 mg / kg of sodium selenate, and 0.99 mg / kg of sodium selenite (based on the total weight of the materials). In the control (CK), no selenium solution was sprayed. Both the control and Se treatments used an air pump to continuously supply oxygen, and the temperature of the temperature control sheet was controlled at 30°C. Composting began, and the composting days were 50 days.

[0106] (4) Compost sample metagenomic sequencing, gene prediction and abundance analysis were performed by Shenzhen Geneplus Technology Co., Ltd. After library inspection, Illumina PE150 sequencing was used. The raw data collected after sequencing had a certain proportion of low-quality data. To ensure that the results of subsequent analysis are accurate and reliable, it is necessary to perform quality control and host filtering on the raw data to obtain clean data for subsequent analysis. Then, the method of assembling and analyzing the obtained fragments has been described in previous studies, and fragments less than 500 bp were screened out. Using the open reading frame predicted by MetaGeneMark, the prediction results filtered out information less than 100 nt in length. Subsequently, CD-HIT software was used to perform redundancy processing on the open reading frame prediction results to obtain a non-redundant initial gene catalog (clustering with 95% identity and 90% coverage). Gene abundance analysis requires Bowtie2 to compare the initial gene catalog with the clean data of each sample. The number of reads is calculated based on the gene comparison, and the genes supporting reads are set in each example. The subsequent analysis is based on the gene catalog (Uni gene), which is obtained by screening out genes supporting reads ≤ 2 in each instance. Basic information statistics are performed based on the abundance information of each gene in each sample in the gene catalog.

[0107] Functional genes related to nitrous oxide emission during composting Fig.13 As shown in the figure, compared with the control, the abundance of nirK genes in Se treatment was higher in the middle and late stages of composting, and on the 27th and 50th days of composting, the abundance of nirK genes in Se treatment was significantly lower than that in the control (P < 0.05). During the composting process, the abundance of nirK genes was positively correlated with the emission of nitrous oxide, indicating that the addition of selenium reduced the emission of nitrous oxide.

Claims

1. A formula for selenium-rich compost of invasive organisms, characterized in that: The invention comprises compost material and selenium source, wherein the compost material is micrantha micrantha and Pomacea canaliculata meat; the carbon-nitrogen ratio of the compost material is 20-30:1; the selenium source is composed of sodium selenate, sodium selenite and / or nano-selenium, and the addition amount is 1.5-4.5 mg / kg of the compost material.

2. The invasive organism selenium-rich compost formula according to claim 1, characterized in that: The selenium source consists of nano-selenium and sodium selenate, the added amount of nano-selenium is 1.13-1.36 mg / kg of compost material, and the added amount of sodium selenate is 1.58-1.95 mg / kg of compost material.

3. The invasive organism selenium-rich compost formula according to claim 2, characterized in that: The amount of nano-selenium added was 1.21 mg / kg of compost material, and the amount of sodium selenate added was 1.92 mg / kg of compost material.

4. The invasive organism selenium-rich compost formula according to claim 1, characterized in that: The selenium source consists of nano-selenium and sodium selenite, the added amount of the nano-selenium is 1.37-1.51 mg / kg of compost material, and the added amount of the sodium selenite is 1.08-1.25 mg / kg of compost material.

5. The invasive organism selenium-rich compost formula according to claim 4, characterized in that: The amount of nano-selenium added was 1.47 mg / kg of compost material, and the amount of sodium selenite added was 1.16 mg / kg of compost material.

6. The invasive organism selenium-rich compost formula according to claim 1, characterized in that: The selenium source consists of nano-selenium, sodium selenate and sodium selenite, wherein the amount of nano-selenium added is 0.85-1.12 mg / kg of compost material, the amount of sodium selenate added is 1.12-1.57 mg / kg of compost material, and the amount of sodium selenite added is 0.81-1.07 mg / kg of compost material.

7. The invasive organism selenium-rich compost formula according to claim 6, characterized in that: The amount of nano-selenium added is 0.98 mg / kg of compost material, the amount of sodium selenate added is 1.36 mg / kg of compost material, and the amount of sodium selenite added is 0.99 mg / kg of compost material.

8. The invasive organism selenium-rich compost formula according to claim 1, characterized in that: The carbon-nitrogen ratio of the compost material is 21:

1.

9. A method for preparing selenium-rich compost of invasive organisms based on the formula of selenium-rich compost of invasive organisms according to any one of claims 1 to 8, characterized in that: The steps include: S1. drying and crushing the cleaned Mikania micrantha; washing the separated Pomacea canaliculata meat; S2. Place the compost material described in step S1 into a compost container at a carbon-nitrogen ratio of 20 to 30:1, control the moisture content to 50% to 70%, mix well, and evenly spray 1.5 to 4.5 mg / kg of the total weight of the compost material with a selenium source solution, and then aerobically compost at 30 to 35° C. for 40 to 50 days to obtain invasive bio-selenium-rich compost.

10. The selenium-rich compost of invasive organisms prepared by the preparation method according to claim 9.

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