Study On Biochar Of Spent Mushroom Substrate And Its Application

Spent mushroom substrate contains abundant nutritional materials,which is always directly discarded or used as combustion.It not only causes the waste of resources,but also creates the environmental problem.The comprehensive utilization and the development of spent mushroom substrate can invite better economic,social and environmental benefits.In this study,using the Flammulina velutipes planting waste(spent mushroom substrate)as raw materials,spent mushroom substrate was studied by the microwave fast pyrolysis technology.The pyrolysis process of spent mushroom substrate,the distribution and the properties of solid products were explored.The feasibility of biochar used as soil conditioner was discussed.Studying a systematic research of microwave pyrolysis and solid products of spent mushroom substrate are able to provide a new method to make this agricultural waste as a renewable new energy.This paper firstly used mushrooms substrate as the raw materials,studying the composition and the thermo gravimetric analysis in order to find out the quality changing law of the pyrolysis process.The result provided a theoretical reference for the pyrolysis process selection of mushrooms substrate microwave.The single factor experiment explored the variation rule of three kinds of pyrolysis products(solid,liquid,gas)distribution with four main influence factors(microwave power,pyrolysis time and microwave absorbers amount)and determined the optimum process parameters:pyrolysis temperature of 450 ?,microwave power of 1.8 kW,the amount of added absorbent of 3%and pyrolysis time of 5 min.It was guaranteed that the occurrence of the second cracking reaction was controlled as far as possible under biochar completely pyrolyzed.Secondly,the influence of temperature on the production and the properties of biochar of microwave pyrolysis was investigated.And the changes of specific surface area,XRD crystal structure,surface morphology and surface element content were analyzed.With the increase of temperature,biochar yield and H,O,N content reduced,while HWC,O/C and(O+N)/C ratio decreased.At the temperature of 700 ?,the biochar pH value increased to 10.43 and water holding capacity increased to 7.886 ML·g-1.And biochar reduced the number of surface chemical groups,heteroatoms reduction and saturated fatty acid structure.Thirdly,six catalysts(potassium hydroxide,potassium chloride,potassium carbonate,potassium hydrogen carbonate,calcium oxide,calcium carbonate)were selected to investigate the influence of catalyst to biochar,including element content,available nutrient,physical and chemical properties and organic composition.Catalyst could increase the yield of biochar and H/C and O/C ratio and reduce the degree of carbonization of biochar.The effects of KOH and CaO were greater than other catalysts which strengthen the biomass carbon specific surface area and the iodine adsorption value.Finally,the comprehensive utilization of biochar produced by microwave pyrolysis was studied,Biochar improved the soil nutrients,soil pH,water holding capacity and porosity,while the range that bulk density decreased was from 6.41%to 29.49%.Biochar also increased soil enzyme activity.When the amount of biochar was 100 g·m-2,soil catalase,sucrase and urease increased by 85.23%,44.82%and 24.17%respectively.Tomato plant height and stem diameter increased by 7.15%and 16.67%respectively.And the chlorophyll content of tomato leaves increased by nearly 3 times.It was suggested that adding a certain amount of biochar was conducive to the growth of tomato.