Carbon sequestration effect technology of biochar in flooded soil

Abstract

The invention relates to a methane emission reduction effect technology of biochar in rice-free and rice-containing waterlogged soil. The specific preparation steps of the biochar are as follows: (1) harvesting corn straws; (2) firing the corn straws in the step (1) at 500 DEG C to obtain biochar; and (3) grinding and sieving the biochar in the step (2) to obtain 80-100-mesh corn straw biochar. Before the rice seeds are sown, after the corn straw biochar in different proportions in the step (3) is applied to the land, ploughing and uniform mixing are conducted, and after the rice seeds are sown, the rice seeds grow naturally to determine the optimal carbon sequestration proportion of the biochar. Results show that the rice-free group and the rice group to which 2% of the biochar is applied can well fix the carbon carried by the biochar in the soil, and the accumulated methane emission in the flooded soil can also be remarkably reduced. Scientific basis is provided for straw resource utilization, and the method has very important significance on green and sustainable agricultural development applying the biochar.

Description

Technical Field

[0001] The invention relates to a biochar methane emission reduction effect technology in flooded soil without rice and with rice, belonging to the technical field of biochar carbon emission reduction effect. Background Art

[0002] Globally, it is agreed that greenhouse phenomena have been triggered due to excessive human production and activities. Methane is the second largest greenhouse gas, so it has a significant impact on the greenhouse effect. More importantly, the concentration of methane has risen sharply in the past two decades. Agricultural activities are the main source of greenhouse gases, accounting for about 24% of the total greenhouse gas emissions. It is estimated that 40.9% of greenhouse gases produced by agricultural production activities come from rice, of which methane is the main greenhouse gas emission. China is a country with rice as its main food, and its annual rice production accounts for 28.1% of the world's total production. Therefore, methane emissions from rice in China or the world have always been a hot research topic. In addition, in addition to rice fields, methane emissions from submerged farmlands such as wetlands, taro and aquaculture ponds may also be a research hotspot in the future. Therefore, it is also very necessary to conduct some research on flooded soils in the rice-free group and the rice group. How to effectively reduce methane emissions from flooded soils is of great significance to slow down or even solve the increasingly serious greenhouse effect.

[0003] In addition to the potential risk of greenhouse gas emissions, the final destination of crop straw (such as corn straw) is also a very thorny practical problem. Traditional treatment methods, such as straw burning and landfilling, will cause environmental problems such as rapid carbon dioxide emissions and soil acidification. Therefore, it has been suggested to pyrolyze straw waste at high temperature in anoxic or anaerobic environments to obtain biochar. Biochar has the characteristics of large specific surface area, porosity, stable chemical properties and strong adsorption capacity. Based on these characteristics, the Intergovernmental Panel on Climate Change (IPCC) recommended the use of biochar to reduce methane emissions from rice fields in 2019. Biochar has become popular as a promising technology to reduce methane emissions from rice fields.

[0004] In addition to studying the effects of biochar on methane emissions from flooded soils, it is also necessary to study the physical and chemical properties of flooded soils under the action of biochar. Previous studies on the effects of biochar on methane emissions from rice fields have mainly focused on biochar modification, preparation methods, and raw materials. For example, compared with water-washed biochar, the use of hydrogen peroxide (H 2 O 2 ) and nitric acid (HNO 3) modified biochar has a more obvious inhibitory effect on methane emissions. Biochar produced at temperatures of 300°C, 500°C and 700°C can effectively inhibit methane emissions from rice fields. In addition, the study also showed that biochar produced from three different raw materials, orange peel, rice straw and bamboo powder, had different methane inhibition effects. In addition, the application of biochar can not only change the structure of the microbial community, but also increase the pH value and improve the soil oxygen content, thereby reducing methane emissions. Changes in soil properties have a significant impact on methane emissions, such as pH and organic matter. Despite these reports, there are studies on the effect of applying different ratios of biochar on cumulative methane emissions in flooded soils without and with rice, especially finding the optimal biochar ratio to achieve the ideal carbon fixation effect. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a low-cost and widely available biochar as an improved material for reducing methane emissions, and to provide an optimal biochar application ratio in flooded soils without rice and with rice, so as to achieve the effect of reducing cumulative methane emissions to the greatest extent.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] (1) Take 1-2 kg of corn stalks, air-dry the raw materials before making charcoal, cut them into pieces of about 10 cm, and put them into the carbonization furnace. The charcoal making temperature control adopts the "programmed temperature rise" technology, that is, the temperature rises by 8.5°C per minute. After reaching 500°C, this temperature is maintained until there is no more gas overflowing from the outlet, and the heating program is turned off. The entire carbonization process takes about 10 hours. After the cracking process is completed, cool it to room temperature, open the carbonization furnace, and take out the biochar. Grind and sieve the biochar to obtain 80-100 mesh corn stalk biochar;

[0008] In addition, this study also published the following preliminary experiments to determine the optimal carbon fixation ratio of biochar.

[0009] (1) Apply different biochar contents in (1) to the soil, including 0%, 0.5%, 1%, 2% and 3% biochar in the rice-free group and the rice group, for a total of ten groups, and mix the soil and biochar. Transplant the rice seedlings. After transplanting the rice seedlings, let them grow naturally for 105 days;

[0010] (2) Every 15 days, the gas in each treatment group was collected using a static chamber method, and the methane emission in each treatment group was measured using a gas chromatograph equipped with a flame ionization detector;

[0011] (3) Every 30 days, the pH, redox potential, soluble organic carbon, and total organic carbon of the soil in each treatment group were measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 .Schematic diagram of the static gas collection device.

[0013] Figure 2 .Changes in soil physical and chemical properties.

[0014] Figure 3 .Outdoor temperature change curve.

[0015] Figure 4 .Comparison of cumulative methane emissions and variables.

[0016] Figure 5 .Amount of biochar and fertilizer applied in different treatments (g / pot)

[0017] Figure 6 Basic chemical and physical properties of biochar and soil DETAILED DESCRIPTION

[0018] The present invention is further described below in conjunction with the accompanying drawings and specific preferred implementation examples, but the protection scope of the present invention is not limited thereby.

[0019] Embodiment 1:

[0020] The soil used in this experiment was taken from the rice planting area of ​​Pingtang Street, Yuelu District, Changsha City, Hunan Province, China (28°2′N and 112°53′E). The surface soil (0-20cm) of the area was collected and three locations were randomly selected for sampling. The basic physical and chemical properties are: pH—6.57, redox potential—85.50mV, total phosphorus—0.29g / kg, total nitrogen—1.08g / kg, soluble organic carbon—145.33mg / kg, total carbon—25.56g / kg.

[0021] In this experiment, corn straw biochar was prepared at 500°C. 1-2 kg of corn straw was taken, and the raw material was air-dried before charcoal making, cut into pieces of about 10 cm, and put into the carbonization furnace, and the carbonization temperature was controlled at 500°C for 10 hours to obtain corn straw biochar.

[0022] The biochar prepared above was used for cultivation experiments in potted plants. Each potted plant had an upper diameter of 24.4 cm, a lower diameter of 21.0 cm, and a height of 23.0 cm. 0 g of biochar, 12.5 g of biochar, 25 g of biochar, 50 g of biochar, and 75 g of biochar were added to five medium-sized potted plants with different proportions of biochar. The collected soil was air-dried, ground, and sieved to 2 mm. The treated soil was then filled into each medium-sized potted plant until 2.5 kg of the soil was mixed thoroughly to obtain five treatment groups, which were recorded as CK. 0 , CK 1 , CK 2 , CK 3 , CK4 , each treatment group was tested in triplicate.

[0023] Deionized water was added to the potted plants to submerge the soil until the water surface was 3 to 5 cm above the soil. Ensure that the water surface of each treatment group was always 3 to 5 cm above the soil during the 105 days of the cultivation experiment. The cultivation time began three days after the soil was submerged. Soil samples were collected from each treatment group on the 15th, 45th, 75th and 105th days to avoid the effects of adding urea, superphosphate and potassium chloride on day 0 as much as possible. After the obtained soil was air-dried, the visible plant residues and coarse debris in the soil samples were manually removed, and they were ground and sieved for the determination of the pH, redox potential, soluble organic carbon and total organic carbon of the soil in each treatment group.

[0024] The static chamber method was used to collect gas samples from each treatment group. The static gas box was made of acrylic material, with a length of 0.4m, a width of 0.4m, a height of 0.9m, and a volume of 0.144m 3 . A small hole with a diameter of 0.5 cm was opened on the upper cover (0.4m×0.4m), and a rubber tube with the same aperture was inserted into the small hole. One end of the tube was inserted into the box 2 to 3 cm deep, and the other end was connected to the syringe outside the box to extract the gas inside the box. The gas sampling period was from 9:00 to 11:00 a.m. every day, and gas collection was carried out every five days between the three parallel samples of each treatment group. During the two-hour gas collection process, water was added to the water tank to form a closed space between the box and the water tank to isolate the influence of external gas. An electric fan was placed in the box, and the electric fan was turned on during the gas collection period to mix the gas inside the box. When collecting gas, the gas inside the box was sucked by a syringe, and the gas in the syringe was stored in a 50mL aluminum foil gas sampling bag. The methane emissions in each treatment group were determined by a gas chromatograph equipped with a flame ionization detector.

[0025] Through the above cultivation experiment, we obtained:

[0026] On days 15, 45, 75, and 105, the soil samples from the potted plants without rice were analyzed, and there was no significant difference in pH and redox potential among the treatment groups. 2 , CK 3 and CK 4 The dissolved organic carbon concentration of the group was compared with that of CK 0 The carbon content of the two groups decreased by 13.92%, 14.97% and 6.85% respectively, while the total organic carbon showed no difference.

[0027] In the 105-day pot experiment, CK without biochar application 0 The cumulative methane emission of the group was the highest, and CK with 2% biochar was 3The cumulative methane emissions of the group were the lowest. 0 Compared with the CK group 1 , CK 2 , CK 3 and CK 4 The cumulative methane emissions of the groups decreased by 2.04%, 41.41%, 50.16% and 30.23%, respectively.

[0028] These results indicate that in the flooded soil without rice, CK 3 The group could best fix the carbon carried by biochar in the soil, and the application of 2% biochar was the most effective in reducing cumulative methane emissions.

[0029] Embodiment 2:

[0030] The soil used in this experiment was taken from the rice planting area of ​​Pingtang Street, Yuelu District, Changsha City, Hunan Province, China (28°2′N and 112°53′E). The surface soil (0-20cm) of the area was collected and three locations were randomly selected for sampling. The basic physical and chemical properties are: pH—6.57, redox potential—85.50mV, total phosphorus—0.29g / kg, total nitrogen—1.08g / kg, soluble organic carbon—145.33mg / kg, total carbon—25.56g / kg.

[0031] In this experiment, corn straw biochar was prepared at 500°C. 1-2 kg of corn straw was taken, and the raw material was air-dried before charcoal making, cut into pieces of about 10 cm, and put into the carbonization furnace, and the carbonization temperature was controlled at 500°C for 10 hours to obtain corn straw biochar.

[0032] The biochar prepared above was used for cultivation experiments in potted plants. Each potted plant had an upper diameter of 24.4 cm, a lower diameter of 21.0 cm, and a height of 23.0 cm. 0 g of biochar, 12.5 g of biochar, 25 g of biochar, 50 g of biochar, and 75 g of biochar were added to five medium-sized potted plants with different proportions of biochar, respectively. The collected soil was air-dried, ground, and sieved to 2 mm. The treated soil was then filled into each medium-sized potted plant until 2.5 kg of the soil was mixed thoroughly to obtain five treatment groups, which were recorded as E, K, and E. 0 , EK 1 , EK 2 , EK 3 , EK 4 , each treatment group was tested in triplicate.

[0033] The rice seeds selected were Xiang Zao Xian 45, a conventional medium-maturing early indica variety bred by the Agricultural Science Bureau of Yiyang City, Hunan Province (Xiang Shen Rice No. 2007002). Before germinating the rice, it was first washed with ultrapure water, then soaked in 70% ethanol for 30 seconds and 10% NaClO solution for 10 minutes to sterilize the surface of the seeds, and then fully washed with ultrapure water. After the rice seeds were disinfected, they were placed in a cultivation pot, and rice nutrient solution was added to slightly above the grid, and hydroponics was carried out for two weeks.

[0034] Deionized water was added to the pot to submerge the soil until the water surface was 3 to 5 cm above the soil. Ensure that the water surface of each treatment group was always 3 to 5 cm above the soil during the 105 days of the cultivation experiment. The cultivation time was calculated three days after the soil was submerged. Rice seedlings with similar growth conditions were selected for transplanting, and two rice seedlings were transplanted in each pot. Soil samples were collected from each treatment group on the 15th, 45th, 75th and 105th days to avoid the effects of adding urea, superphosphate and potassium chloride on day 0 as much as possible. After the obtained soil was air-dried, the visible plant residues and coarse debris in the soil samples were manually removed, and they were ground and sieved for the determination of the pH, redox potential, total nitrogen, total phosphorus, soluble organic carbon and total organic carbon of the soil in each treatment group.

[0035] The static chamber method was used to collect gas samples from each treatment group. The static gas box was made of acrylic material, with a length of 0.4m, a width of 0.4m, a height of 0.9m, and a volume of 0.144m 3 . A small hole with a diameter of 0.5 cm was opened on the upper cover (0.4m×0.4m), and a rubber tube with the same aperture was inserted into the small hole. One end of the tube was inserted into the box 2 to 3 cm deep, and the other end was connected to the syringe outside the box to extract the gas inside the box. The gas sampling period was from 9:00 to 11:00 a.m. every day, and gas collection was carried out every five days between the three parallel samples of each treatment group. During the two-hour gas collection process, water was added to the water tank to form a closed space between the box and the water tank to isolate the influence of external gas. An electric fan was placed in the box, and the electric fan was turned on during the gas collection period to mix the gas inside the box. When collecting gas, the gas inside the box was sucked by a syringe, and the gas in the syringe was stored in a 50mL aluminum foil gas sampling bag. The methane emissions in each treatment group were determined by a gas chromatograph equipped with a flame ionization detector.

[0036] Through the above cultivation experiment, we obtained:

[0037] On days 15, 45, 75, and 105, the potted soil in the rice group was sampled and analyzed. In terms of pH and redox potential, EK 0 , EK 1 , EK 2 , EK3 and EK 4 There is no significant difference. In the early stage of the experiment, EK 1 , EK 2 , EK 3 and EK 4 The dissolved organic carbon concentration of the group was compared with that of EK 0 The EK 1 , EK 2 , EK 3 and EK 4 The total organic carbon concentration of the group was compared with that of EK 0 The soluble organic carbon and total organic carbon in the late stage of the experiment had no significant difference.

[0038] In the 105-day pot experiment, EK 0 The cumulative methane emissions of the EK group were the highest, while the EK group with 2% biochar was 3 The cumulative methane emissions of the group were the lowest. 1 , EK 2 , EK 3 and EK 4 The cumulative methane emissions of the groups were 0 The differences in the P values ​​in the control group were 17.49%, 32.84%, 62.42% and 24.69% lower.

[0039] These indicate that in the flooded soil of the rice group, the EK3 and EK4 groups can fix the carbon carried by biochar in the soil well, and the application of 2% biochar can most effectively reduce the cumulative methane emissions.

Claims

1. A method for reducing methane emissions in flooded soils without or with rice using biochar, characterized in that The specific steps are: (1) Take 1-2 kg of corn stalks, air-dry the raw materials before making charcoal, cut them into pieces of about 10 cm, and put them into the carbonization furnace. The temperature control of charcoal making adopts the "programmed temperature rise" technology, that is, the temperature rises by 8.5°C per minute. After reaching 500°C, this temperature is maintained until there is no more gas overflowing from the outlet, and the heating program is turned off. The entire carbonization process takes about 10 hours. After the cracking process is completed, cool it to room temperature, open the carbonization furnace, and take out the biochar. Grind and sieve the biochar to obtain 80-100 mesh corn stalk biochar; (2) Applying different biochar contents in (1) to the soil, including 0%, 0.5%, 1%, 2% and 3% biochar in the rice-free group and the rice group, for a total of ten groups, and mixing the soil and biochar. Transplanting the rice seedlings. After transplanting the rice seedlings, let them grow naturally until 105 days; (3) Every 30 days, measure the soil pH, redox potential, soluble organic carbon, and total organic carbon in each treatment group; (4) Every 15 days, the gas in each treatment group was collected using a static chamber method, and the methane emission in each treatment group was measured using a gas chromatograph equipped with a flame ionization detector.

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