Preparation Of Sludge Biochar And Its Impacts On Soil Properties And Crop Growth

This study used a microwave screw moving bed reactor to pyrolyze the sludge-straw mixture(at different mixing ratios)to prepare biochar at different temperatures,and the co-pyrolysis of the mixture with bentonite and potassium phosphate was also performed to modify the biochar properties.The properties of prepared biochar are measured by FTIR,SEM,XRD and other tests.It was found that there is no heavy metal in the tested sludge sample.The addition of straw into the sludge reduces the ash content of the mixture,and has an effect on biochar yield,elemental composition of biochar,crystal type,pore structure and pH.Adding two catalysts increases the biochar yield and promotes the formation of biochar pore structure.The proportions of N,C,H and S elements in the modified biochar are reduced.The crystal type changes.The pH of the potassium phosphate-modified biochars are alkaline.Through a short-term pot experiment,the effects of different types of biochar on the pH,nitrogen and phosphorus of corn-planting soil samples and the plant growth rate and dry matter content of corn are explored.It is concluded that the pH value of weak alkaline soil used in this study is significantly impacted by the pH value and surface porosity of the applied biochar.With the addition of biochar,the content of nitrogen and phosphorus in the soil increases,showing a good capacity of continuous nitrogen and phosphorus supply.The mixing of straw with sludge is not conducive to the increase of soil nitrogen content.Modification of biochar using two types of catalysts are not conducive to enhance the soil nitrogen level.For soil phosphorus level,potassium phosphate as the catalyst has the best effect.The growth rate and dry matter content of corn plants are affected by many factors.Overall,the addition of slugde-derived biochar reduced the growth rate and the dry matter content of crops.The addition of straw into sludge for biochar production increases the crop growth rate and reduces the crop dry matter content.Both catalytic modification treatments showed negative effects on the growth rate,and the dry matter content of vegetation showed an increasing effect at pyrolysis temperature of 450?.