Study On Biochar Preparation Based From Plant-type And Its Effect On Crop Growth

There are large amounts of waste such as straw,husks and peels result from large agricultural country in China.Although plenty of them has been used as functional materials,direct return to land,animal feed,or fuel,et al.there is still good deal of them has been burned or discarded in field or roads.Therefore,the development use of plant-quality agricultural wastes,such as straw,husks and peels is getting an increasing attention nowadays.In this paper,pot experiments with different crops were carried out to determine the effects of biochar prepared from different raw materials on crop growth and content of TOC,TN,P,K,and other elements.The paper was aimed to assess the effects of raw material types on biochar and its corresponding soil properties and the content of major elements.The results were showed as following:The first part mainly analyzed the physical and chemical properties of raw materials and the optimization of biochar process parameters for pyrolysis preparation.The main research results included the following two aspects:(1)The results of fourier transform infrared(FTIR)spectroscopy and X-ray diffraction(XRD)patterns showed that the functional groups and microcrystalline structures of MS,WS,SS,SH,RH,CS and OS were similar.The TG curves of corn stalk(MS),wheat straw(WS),sunflower straw(SS),sunflower seed husk(SH),rice husk(RH),chestnut shell(CS)and orange peel(OS)decreased with temperature,and the decline was mainly in the range of 250-400?.And there was a distinct peak of DTG curves in the range of 250?400? and tailing phenomenon in the high temperature range,which indicated that the hemicellulose and cellulose in the raw materials were basically pyrolyzed at this temperature range,and the weight loss after 400? is mainly the pyrolysis of the remaining lignin and the further aromatization of the biochar.Thus,the pyrolysis process of MS,WS,SS,SH,RH,CS and OS had the same parameters and mechanism.(2)The preparation of biochar with sealed method instead of N2 atmosphere in the range of 300-700? was proved to be feasible.And compared to condition in nitrogen atmosphere,the residence time was shorter under sealing oxygen limiting method when the temperature was below 500?.Meanwhile,the relationship between the pyrolysis temperature(T)and the residence time(t)with sealed method and N2 atmosphere were established by experimental fitting as follows:t=-4.80973+254.94279×0.99485T and t=-65.4627+295.4227×0.9978T respectively.The second part mainly analyzed the physical and chemical properties and adsorption properties of biochar,and optimized the biochar with excellent comprehensive performance as a spare sample for crop pot experiment.The main research results included the following two aspects:(1)The pH,apparent density,porosity and TOC content of biochar increased with pyrolysis temperature.However,the yield,the TN,P,K content of biochar,and water holding capacity decreased slightly with pyrolysis temperature when the pyrolysis temperature was higher than 500?.The results of fourier transform infrared(FTIR),X-ray diffraction(XRD)and scanning electron microscopy(SEM)showed that the pore volume of biochar and the degree of aromatization increased with pyrolysis temperature.The results showed that the pyrolysis temperature and the type of raw materials all had an impact on the physicochemical properties of biochar.However,the influence of raw material types on the physicochemical properties of biochar was more pronounced than the pyrolysis temperature.(2)The adsorption of Pb2+by biaochrs of wheat straw(BWS),maize straw(BMS),sunflower straw(BSS),rice husk(BRH),sunflower husk(BSH),chestnut shell(BCS)and orange skin(BOS)could be fitted by both Frendlich and Langmuir models.The adsorption of Pb2+by seven biochars of BMS,BSS,BWS,BRH,BSH,BCS and BOS can be fitted by both Frendlich and Langmuir models,and the adsorption amount is high.Meanwhile,biochars of straw(BMS,BSS and BWS)and orange peel(BOS)adsorption effect was better than BRH,BSH and BCS chaff,nut shell biochar.The main possible reasons were that the adsorption behavior of Pb2+ by seven biochars BOS,BSH,BRH,BSS,BCS,BMS,BWS was affected by its own mineral components,chemical functional groups,pore volume and specific surface area.Meanwhile,the higher specific surface area and pore structure were the main reason of that the adsorption rate of biochars of maize straw(BMS),sunflower straw(BSS)and wheat straw(BWS)on methylene blue solution was much higher than that of orange shell(BOS)and sunflower seed shell(BSH).In the third part,biochar was applied to the soil for crop cultivation experiment,and the effects of biochar application on the growth of TOC and other nutrients in the soil and crop yield were analyzed.The main research results included the following four aspects:(1)The crops pot experiments showed that the growth of crops was promoted and the yield of crops was increased because of biochar added.Particularly,the type of biochar had great differently effect on the growth and yield of crops.For example,compared to the non-addition group,the number of potted flowers of BWS,BCS,and BMS group increased by 69.4%,69.9%,and 66.2%,respectively.Probably,the effects of BWS,BMS and BCS on the growth status of mimosa,mung bean,wheat and red canola were more obvious compared with others,which was mainly because the much content of K,P,porosity and better water holding capacity of BWS and BMS,as well as TOC and TN content and high apparent density of BCS made it better for the growth of crops.(2)The contents of TOC,TN,P,and K in soil increased with the application of biochar.However,the increased amount was significantly affected by the type of raw material for biochar preparation but had no positive correlation with the content of TOC,TN,P and K in the biochar itself.For example,the TOC content of BOS was as high as 63.79%,but the TOC content of soil with BOS was only 2.84%,while the TOC content in the soil was as high as 3.91%for 44.17%of TOC content in BRH.(3)The effect of biochar on the contents of TOC,TN,P,and K in soil had a certain relationship with the biochar water holding capacity,apparent density and porosity,and the contents of K and P in the soil vary.The content of K and P in soil increased with the increase of water holding capacity and apparent porosity of biochar.The soil with BCS had higher TOC and TN content than other soils probably was mainly because that high apparent density increased aeration of soil.(4)The growth of crops and the content of nutrients such as TOC,TN,P,and K were promoted with the application of biochar.However,further analysis of data fitting by Origin software showed that the contents of nutrients such as TOC,TN,P,and K in biochar and the corresponding nutrient elements in soil and the nutrients such as TOC,TN,P,and K in soil There is a linear correlation between the contents of elements,but the content of TOC,TN,P,K and other nutrients in the soil is not linearly related to the plant height and yield.This may be due to TOC.The transfer mechanism of nutrients such as IN,P and K in soil is related to the mechanism of migration and transformation.In summary,the straw is rich in TOC,TN,P,K and other elements,can provide or increase the content of TOC,N,P,K and other nutrients or components for soil and crops,and the apparent density of biochar is high.Depending on the properties such as porosity and water holding capacity,the permeability of the soil and the ability to maintain nutrients are increased,which contributes to the supply of crop nutrients and moisture,promotes the growth of crops,and increases the yield of crops.The pH value of the test soil is similar to that of the test soil and does not affect the acidity and alkalinity of the soil.