Effect And Life Cycle Analysis Of Biochar Remediation In Cadmium-contaminated Soil

Soil heavy metal pollution is on the rise as a result of human activity.Cadmium(Cd)is one of the most concerning heavy metal pollutants in the world due to its high toxicity and mobility.Cd in soil is easily enriched in the edible sections of staple foods like rice,wheat,and corn,posing a health and safety risk to humans.Therefore,the remediation of Cd-contaminated soil has received much attention.Biochar application,which is commonly utilized in soil Cd contamination remediation,has tremendous potential in lowering Cd bioavailability and enhancing agricultural sustainability among numerous remediation approaches and materials.The majority of the known research focuses on the effect of biochar on Cd-contaminated soil in a specific scenario.Few research have looked at the differences in biochar’s remediation effect in different planting systems’ soil application settings.The results of the analysis are not uniform,and the environmental impact of biochar application across its entire life cycle is still unclear.Therefore,this study first established a literature database based on 780 papers on biochar remediation of Cd-contaminated soils that were included in the Web of Science database before December 2020.A Hierarchical Meta-analysis was used to evaluate the biochar remediation effect of cadmium-contaminated soil in flooded grasses,dryland grasses,and non-grass planting systems and the soil,root system,and edible parts.Single Meta-regressions and Random Forest were used to clarify the biochar.Effects of production parameters,soil physicochemical properties,and anthropogenic factors on biochar remediation.Finally,Life Cycle Assessment,Life Cycle Cost,and Hierarchical Metaanalysis are coupled to evaluate the effect,environmental impact,and economic cost of biochar remediation.This research intends to uncover biochar’s cadmium pollution remediation effect in various planting systems,as well as its life-cycle influence on its own manufacturing process,thereby bringing fresh insights into the long-term management of typical crop planting systems.Core results are shown below:(1)Biochar application can significantly reduce the available Cd content in crop soil.Biochar application significantly reduced soil Cd bioavailability(p < 0.0001)and significantly reduced Cd content in crop roots and edible parts(p<0.0001).The average declines were 31.2%,31.5%,and 37.9%,respectively.(2)There are relative differences in soil biochar remediation effects in different planting systems.The soil Cd bioavailability decreased by 29.5%,28.6%,and 33.8% in flooded gramineae,dry-fed gramineae,and non-poinee cropping systems,respectively.The reduction rates of Cd bioaccumulation in the roots of the three types of planting systems were 28.5%,24.9%,and 35.8%,respectively.The decline rates of Cd bioaccumulation in the edible part of the three types of planting systems were 36.4%,45.0%,and 36.9%,respectively.(3)The relative contributions of biochar application rate,biochar p H,soil p H,and soil CEC to changes in Cd content in crop roots and edible parts all exceeded 44.30%.The higher the biochar application rate and biochar p H,the greater the relative decrease of Cd content in crop roots and edible parts during biochar remediation.The higher soil p H and soil CEC were,the smaller the relative decrease of Cd content in crop roots and edible parts was when biochar was applied for remediation.(4)Lignocellulosic biochar reduced Cd levels in flooded Gramineae(Type A: 35.60 percent,45.66 percent)and dry-fed Gramineae roots and edible sections the most(Type B:33.63 percent,59.34 percent).Good results: manure biochar had the best impact on reducing Cd content in non-grass(Type C: 59.34 percent and 49.84 percent)crops’ roots and edible sections.(5)The key factors affecting the life cycle of biochar remediation in cadmiumcontaminated soil are pyrolysis temperature,pyrolysis time,yield,and condensate consumption.Among all types of biochar,the lowest environmental impact is lignocellulosic biochar(L350)produced at 350 °C for 0.72 h,herbal biochar(H450)produced at 450°C for 0.32 h,and manure produced at 350°C for 0.63 h.At 350 °C for 0.55 hours,biochar(M350)and wood-based biochar(W350)are produced.(6)The consumption of pyrolysis energy(diesel)is the main factor affecting the environmental impact of biochar production.Herbal biochar(H450)with a heating temperature of 450 °C and a production time of 0.32 h has the lowest economic cost and negative environmental impact.The cost of biochar production mainly comes from the consumption of diesel and condensed water.Biodiesel replaces petrochemical diesel to produce H450,reducing its environmental impact by 48.8%.