Carbon Sequestration And Economical Benefits Of Crop-Residue-Derived Biochar In Soil

Biochar refers to the biomass materials which are pyrolyzed under relatively low temperature(less than 700℃)with anaerobic condition,containing high level of carbon,with large specific surface area and high aromatization.Biochar generally refers to the solid material with high carbon content,large specific surface area and high aromatization produced by the anaerobic or anaerobic pyrolysis of raw materials at low temperature(generally lower than 700℃).Biochar has great potential in soil remediation and greenhouse gas mitigation due to its excellent physicochemical properties.Studies have shown that biochar can not only remain stable in soil,but also promote crop yield by enhancing soil fertility.Bioenergy,as carbon-neutral by-product producing during pyrolysis process,can serve as substitute for fossil fuels which make biochar technology economically and environmentally feasible.At present,there are relatively lack of studies focusing on the assessment of carbon sequestration and emission reduction of the overall scheme of biochar soil application.Few studies have analyzed the application rate of biochar in soil and the economic feasibility of practical application scenarios in China even though the promising potential of mitigating greenhouse gases.Therefore,this paper studied the carbon sequestration and emission reduction potential of biochar soil application under different crop planting systems,and preliminarily discussed the feasibility of the technology at the economic level.The main contents and conclusions of the paper are as follows:(1)The effects of biochar from different biomass materials on soil carbon sequestration and emission reduction were studied.By means of numerical fitting and dynamic fusion of multi-dimensional model,the results show that the carbon sequestration potential,on the one hand,originates from the part of greenhouse gas that is fixed due to the increase of crop yield while crop yield increase rate shows a trend of increasing to critical point before decreasing to zero or even negative with the increase of biomass addition.The effect of the same types of biochar application on the yield of different crops was similar,and the maximum yield increased by 26%on average.For the same plant system,different biomass species and different physicochemical properties of biochar exert a significant difference in yield.Under the same application rate of biochar,other kinds of biochar effect>rice straw biochar>wheat straw biochar.The carbon sequestration potential also depends on the content of unstable components of biochar and the mean residence time of unstable components.Biochar can be stabilized in soil for a long time and reduce soil SOC and N2O emissions.The results provide theoretical support for biochar soil application technology,which can slow down greenhouse gas emissions in many aspects in farmland.(2)The dynamic equilibrium process of carbon content in the farmland-biochar-atmospheric cycling system was studied.When the number of iterative rotation was set to 200,the rice and wheat systems reached the maximum system emission reduction potential at the 64 and 108 rounds respectively,and the carbon sequestration emissions reached 20.59 t/hm2 and 30.75 t/hm2 CO2e-c,and the biochar contents in the soil were 10.2 t/hm2 and 17.1 t/hm2.The cyclic decline model experiment shows that with the increase of soil biochar,the potential of carbon sequestration and emission reduction of farmland increases first and then decreases.When the system reaches the threshold of biochar content,the continuous addition of biochar will lead to the increase of greenhouse gas emissions of the whole system.The sensitivity analysis shows that biochar yield and soil N2O emission are the most critical parameters of the system,which directly affect the potential of carbon sequestration and emission reduction of the system.(3)The economic feasibility of biochar soil application technology was studied,and the cost effectiveness assessment of BSA(Biochar Soil Application)shows that it is economically feasible without considering the carbon price factor only under the wheat scenario.While considering the low carbon price factor,NPV(Net Present Value)changes from negative to positive in the corn scenario,and the payback period is 12 years.The NPV of rice scenario is still negative but comparing to the open burning of straw based on straw,it still has greater environmental and economic benefits.Under the high carbon price setting,all three crop scenarios are economically viable.Factor analysis of the economic feasibility of biochar application shows that agricultural benefits contribute the most,followed by the carbon price index.Although certified emission reductions(CCER)projects are clearly defined for this kind of biochar application technology in China,environmental emissions reduction benefits of BSA system is indispensable for the assessment in future.Overall,our paper gives a theoretical insight on the viability of biochar technology application as a brand-new carbon capture and storage project.