Biomass power plant ash composition for synergistically improving soil carbon sink and microbial activity and preparation method and application thereof

Abstract

The invention discloses a biomass power plant ash composition for synergistically improving soil carbon sink and microbial activity and a preparation method and application thereof, and belongs to the technical field of agricultural resources and environment. The biomass ash composition comprises fly ash and slag, and the mass ratio of the fly ash to the slag is (1-3): (1-3); and determining the physicochemical properties and the heavy metal content of the biomass ash composition. The preparation method comprises the steps of raw material pretreatment and compounding. According to the soil diagnosis result, the optimal formula is selected, blind application is avoided, and the input-output ratio of improved resources is maximized. The defects (FA bacteriostasis and BS carbon sequestration are weak) of a single component are overcome, the unification of two contradictory targets of carbon sequestration and enrichment is realized, and the functions of a soil organic carbon library and an ecological system are synchronously improved. A high-added-value resource utilization way is found for solid waste, waste is turned into wealth, the cost is low, and the method conforms to the strategy of circular agriculture.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid waste resource utilization and soil improvement, and particularly relates to a biomass power plant ash composition for synergistically improving soil carbon sink and microbial activity, and a preparation method and application thereof. BACKGROUND

[0002] Biomass power plant ash is a solid waste generated in the process of biomass power generation, mainly including fly ash and slag. Fly ash has fine particles, large specific surface area, and is rich in mineral elements such as silicon, calcium and potassium, and unburned carbon; the slag has relatively coarse particles, developed pore structure, and contains more alkaline substances and trace elements. At present, the ways of its resource utilization are relatively single, or directly landfilled, or used as low-value building materials, and its environmental value cannot be fully utilized. Although some studies have attempted to use it for soil improvement, there are the following significant defects: Firstly, the existing technology simply mixes fly ash and slag or applies them separately, ignoring the complementarity and potential antagonism of the two in terms of physicochemical properties and ecological functions. Fly ash is rich in carbon source and nutrients, but its high pH and salt can easily inhibit soil microbial activity; the loose structure of slag is beneficial to microbial habitat, but its carbon sequestration capacity is limited. Simple mixing cannot achieve the synergy of "carbon sequestration" and "increasing bacteria", and may even exacerbate soil ecological risks due to improper ratio.

[0003] Secondly, there is a lack of precise ratio guidance based on the response of the soil ecosystem. The existing methods are mostly at the stage of "using what you have", and fail to scientifically functionally compound according to the seemingly contradictory goals of "improving soil organic carbon pool" and "activating microbial community", resulting in unstable improvement effect and low resource input-output ratio.

[0004] Therefore, it is an urgent need to develop a biomass power plant ash composition that can synergistically improve soil carbon sink and microbial activity, and a precise application method, to realize its high-value and ecologically safe resource utilization. SUMMARY

[0005] (I) Objectives The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a biomass power plant ash composition for synergistically improving soil carbon sink and microbial activity, and a preparation method and application thereof in improving degraded black calcic soil.

[0006] (II) Technical solutions In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions: In a first aspect, the present application provides a biomass power plant ash composition for synergistically improving soil carbon sink and microbial activity, which is composed of fly ash and slag, and the dry basis mass ratio of the fly ash to the slag is (1-3):(1-3); the fly ash inhibits microbial mineralization by reducing the content of dissolved organic carbon, while promoting the decomposition of recalcitrant organic carbon and forming mineral-organic complexes, thereby significantly improving the physical protection and chemical stability of soil organic carbon; and the slag can improve bacterial diversity.

[0007] The physicochemical properties of the fly ash are as follows: pH 9.5-9.95, electrical conductivity 2250-2984 µS·cm -1 , specific surface area 7.50-7.85 m²·g -1 , and organic carbon content 19.0-21.0 g·kg -1 . The physicochemical properties of the slag are as follows: pH 8.94-9.50, electrical conductivity 380-430 µS·cm -1 , specific surface area 9.75-11.85 m²·g -1 , and organic carbon content 12.13-13.5 g·kg -1 . In addition, the contents of heavy metals Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn in the fly ash and the slag both meet the risk screening values specified in GB15618-2018 “Soil Environmental Quality Risk Control Standards for Agricultural Land Soil Pollution”.

[0008] In a second aspect, the present application provides a preparation method of the biomass power plant ash composition for synergistically improving soil carbon sink and microbial activity, which comprises the following steps: (1) Raw material pretreatment: the fly ash and the slag are respectively subjected to drying, crushing, and screening to obtain raw materials with a particle size of less than 2 mm; (2) Optimization of compounding: the pretreated fly ash and slag are put into a mixer according to the mass ratio specified in claim 1, and mixed for 20-30 minutes until uniform.

[0009] In a third aspect, the present application provides an application of the biomass power plant ash composition for synergistically improving soil carbon sink and microbial activity as a soil conditioner for improving degraded black calcic soil.

[0010] Further, the application comprises: applying the biomass ash composition to the soil plough layer 10-15 cm below the ground surface in a strip or hole application manner at a dosage of 200-400 kg / acre.

[0011] Further, the timing of the application is the fallow period after crop harvesting.

[0012] (III) Beneficial effects The present application is first designed based on the synergistic mechanism of "fly ash as carbon source and nutrient bank, and slag as microstructure regulator". Fly ash provides organic carbon, and slag creates a physical protective microenvironment through cementation reaction. The two are compounded in the soil to build a "carbon fixation" and "microbial habitat" coexisting "aggregate-pore" composite structure, achieving the dual goals of "carbon fixation" and "increasing bacteria" that are traditionally difficult to balance.

[0013] As shown in Tables 3 and 4, under the preferred ratio (1:1), the soil organic carbon is significantly improved, the carbon pool management index (CPI) is greater than 1, and the soil microbial biomass carbon and nitrogen and the diversity of bacterial and fungal communities (Chao1 and Shannon index) are maintained at an excellent level, confirming the sustainability and ecological friendliness of the improvement effect.

[0014] The present application finds a "waste-to-resource" high-value resource utilization way for biomass ash, which is low in cost, simple in operation, in line with the circular agriculture strategy, and has great environmental benefits and promotion potential. DETAILED DESCRIPTION

[0015] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0016] Example 1: Preparation and application of biomass ash composition (fly ash: slag = 1:1) 1. Raw material preparation and pretreatment: Take biomass fly ash and slag that meet the safety standards of GB 15618-2018, and dry them at 105°C to constant weight. After crushing by a jaw crusher, pass through a 2 mm standard sieve to obtain homogeneous raw materials with particle size less than 2 mm. The detailed physicochemical properties and heavy metal content are shown in Tables 1 and 2; Table 1 Basic physicochemical properties of biomass power plant fly ash and slag

[0017] Table 2 Heavy metal content (mg·kg -1 )

[0018] 2. Optimization of compounding: 50 kg of each of the pre-processed fly ash and slag were accurately weighed according to a dry basis mass ratio of 1:1, and were put into a three-dimensional mixer for mixing at a speed of 25 rpm for 25 minutes, and the mixture was discharged, thereby obtaining the biomass ash-slag composition.

[0019] 3. Soil improvement application: In the degraded black calcareous soil region of Northeast China (soil pH 7.45, organic carbon 9.7 g / kg), after the autumn crop harvest, the composition prepared in this example was applied at a dosage of 300 kg / acre, and was applied in strips at a depth of 12-15 cm below the preset seeding line using a fertilizer applicator. After application, the natural freezing and thawing process was used to promote the fusion of the composition with the soil.

[0020] Example 2: Preparation and application of a biomass ash-slag composition (fly ash: slag = 1:2) The difference between this example and Example 1 is only in the compounding ratio. According to a dry basis mass ratio of 1:2, 33.3 kg of fly ash and 66.7 kg of slag were weighed, and the preparation and application methods were the same as in Example 1.

[0021] Example 3: Preparation and application of a biomass ash-slag composition (fly ash: slag = 1:3) The difference between this example and Example 1 is only in the compounding ratio. According to a dry basis mass ratio of 1:3, 33.3 kg of fly ash and 66.7 kg of slag were weighed, and the preparation and application methods were the same as in Example 1.

[0022] Example 4: Preparation and application of a biomass ash-slag composition (fly ash: slag = 2:1) The difference between this example and Example 1 is only in the compounding ratio. According to a dry basis mass ratio of 2:1, 33.3 kg of fly ash and 66.7 kg of slag were weighed, and the preparation and application methods were the same as in Example 1.

[0023] Example 5: Preparation and application of a biomass ash-slag composition (fly ash: slag = 3:1) The difference between this example and Example 1 is only in the compounding ratio. According to a dry basis mass ratio of 3:1, 33.3 kg of fly ash and 66.7 kg of slag were weighed, and the preparation and application methods were the same as in Example 1.

[0024] Effect verification The changes in soil organic carbon under the addition of fly ash and slag of the examples and comparative examples are shown in Table 3; the changes in soil microbial diversity index under the addition of fly ash and slag are shown in Table 4.

[0025] Table 3 Changes in soil organic carbon under the addition of fly ash and slag

[0026] Table 4 Changes in soil microbial diversity index under the addition of fly ash and slag

[0027] Conclusion: From Table 3 and Table 4, it can be seen that the biomass ash composition provided by the present application, fly ash and slag in the ratio range of (1-3):(1-3), can effectively improve the stability of soil organic carbon (reflected in the improvement of CPI and the reduction of mineralization rate), while maintaining excellent microbial diversity. Among them, Example 1 (1:1 ratio) achieves the best balance between carbon sequestration effect and ecological effect, fully verifying the synergistic effect of fly ash and slag. In contrast, pure fly ash has a tendency to inhibit microbial diversity, and pure slag has limited carbon sequestration effect, which highlights the outstanding advantages of the present application in achieving synergistic effect through precise compounding.

[0028] The physicochemical properties and heavy metal content range of the fly ash and slag of the present application are shown in Table 5-6; Table 5 Basic physicochemical properties range of fly ash and slag of biomass power plant

[0029] Table 6 Heavy metal content range (mg·kg-1) of fly ash and slag of biomass power plant -1 )

[0030] The above description of disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A biomass power plant ash composition that synergistically enhances soil carbon sink and microbial activity, characterized in that, comprising fly ash and slag, the mass ratio of fly ash to slag being (1-3):(1-3); The physico-chemical properties of the fly ash range from: pH 9.5 ~ 9.95, electrical conductivity 2250 ~ 2984 µS·cm -1 , specific surface area 7.50 ~ 7.85 m²·g -1 , organic carbon content 19.0 ~ 21.0 g·kg -1 ; The physico-chemical properties of the slag range from: pH 8.94 ~ 9.50, electrical conductivity 380 ~ 430 µS·cm -1 Specific surface area 9.75 ~ 11.85 m²·g -1 Organic carbon content 12.13 ~ 13.5 g·kg -1 ; Moreover, the contents of heavy metals Cd, Hg, As, Pb, Cr, Cu, Ni, Zn in the fly ash and slag meet the risk screening values stipulated in GB 15618-2018 "Soil Environmental Quality Risk Control Standards for Agricultural Land".

2. The biomass power plant ash composition for synergistically enhancing soil carbon sink and microbial activity according to claim 1, characterized in that, comprising fly ash and slag, the mass ratio of fly ash to slag being 1:1, 1:2, 1:3, 2:1 or 3:

1.

3. The biomass power plant ash composition for synergistically enhancing soil carbon sink and microbial activity according to any one of claims 1 to 3, characterized in that, The particle size of the fly ash and slag is less than 2 mm.

4. A method of preparing a biomass power plant ash composition for synergistically enhancing soil carbon sink and microbial activity as claimed in any one of claims 1 to 3, characterized in that, comprising the following steps: (1) raw material pretreatment: dry, crush and screen the fly ash and slag respectively to obtain raw materials with a particle size of less than 2 mm; (2) compounding: put the pretreated fly ash and slag into a mixer according to the proportion and mix uniformly.

5. The method of claim 4, wherein the biomass power plant ash composition is prepared by the steps of: a) providing a biomass power plant ash; b) providing a soil; c) mixing the biomass power plant ash and the soil to form a mixture; d) incubating the mixture for a period of time; and e) collecting the biomass power plant ash composition. 5 The mixer in step (2) is a three-dimensional mixer, and the mixing time is 20-30 minutes.

6. Use of the biomass power plant ash composition of any one of claims 1-3 in improving degraded black calcareous soil and synergistically improving the soil carbon sequestration capacity and microbial activity as a soil conditioner. Soil application range: pH value 7.15 ~ 8.21; organic carbon content: 8.9 ~ 10.0 g kg -1 ; total nitrogen content: 1.60 ~ 1.85 g kg -1 ; available phosphorus content: 25.0 ~ 35.0 g kg -1 ; available potassium content: 250 ~ 260 mg kg -1 .

7. The use of a biomass power plant ash composition according to claim 6 for improving degraded chernozem, simultaneously increasing the soil's carbon sequestration capacity and microbial activity as a soil conditioner, characterized by that, The biomass ash composition is applied to the soil layer 10-15 cm below the ground surface at a dosage of 200-400 kg / acre by strip application or hole application.

8. The use of a biomass power plant ash composition according to claim 6 or 7 for improving degraded black calcareous soil, synergistically improving the soil's carbon sequestration capacity and microbial activity as a soil conditioner, characterized in that, The application timing is during the fallow period after crop harvesting.

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